Mutogoh M a - Precast Lightweight Concrete With Pumice as Aggregates

8/9/2019 Mutogoh M a - Precast Lightweight Concrete With Pumice as Aggregates

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JOMO KENYATTA UNIVERSITY

OF

AGRICULTURE AND TECHNOLOGY

DEPARTMENT OF CIVIL, CONSTRUCTION AND ENVIRONMENTAL ENGINEERING

STUDY AND DESIGN OF PRE- CAST LIGHTWEIGHTCONCRETE WITH PUMICE AS AGGREGATES

AUTHOR: MICHAEL A. MUTOGOH

REG NO: E25-0128/04

SUPERVISOR: ENG: MANG’URIU

This document has been submitted in partial fulfillment for the award of thedegree of Bachelor of science in Civil, Construction and environmentalengineering


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STUDY AND DESIGN OF PRE- CAST LIGHTWEIGHT CONCRETE WITH PUMICE AS AGGREGATES April 1, 2010

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Contents

List of abbreviations ..................................................................................................................................... iv

List of tables ................................................................................................................................................. vi

List of figures ............................................................................................................................................... vii

Dedication .................................................................................................................................................. viii

Acknowledgement ....................................................................................................................................... ix

Abstract ......................................................................................................................................................... x

Chapter 1 ....................................................................................................................................................... 1

1.0 Introduction ............................................................................................................................................ 1

1.1 Background ......................................................................................................................................... 1

1.2 Problem statement ............................................................................................................................. 2

1.3 Problem justification ........................................................................................................................... 21.4 Objectives............................................................................................................................................ 2

1.4.1 Overall objective .......................................................................................................................... 2

1.5 Project hypothesis............................................................................................................................... 2

1.6 Scope and limitation of study ............................................................................................................. 3

1.6.1 Scope ............................................................................................................................................ 3

1.6.2 Limitations .................................................................................................................................... 3

Chapter 2 ....................................................................................................................................................... 4

2.0 Literature review ..................................................................................................................................... 4

2.1 General overview of pre-casting ......................................................................................................... 4

2.2 Benefits of pre-casting ........................................................................................................................ 4

2.3 Pre-cast elements and lightweight concrete ...................................................................................... 5

2.4 Pumice ................................................................................................................................................. 6

2.5.1 Properties of pumice .................................................................................................................... 6

2.5 Mix design ........................................................................................................................................... 7

2.5.1 Objectives of mix design .............................................................................................................. 7Chapter 3 ..................................................................................................................................................... 10

3.0 Methodology ......................................................................................................................................... 10

3.1 A survey of pumice availability ......................................................................................................... 10

3.2 Collection and sampling of material ................................................................................................. 10

3.4 Sampling of materials ....................................................................................................................... 11


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3.5 Grading of materials for concrete production .................................................................................. 11

3.5.1Coarse aggregate ........................................................................................................................ 11

3.5.2 Fine aggregates .......................................................................................................................... 12

3.6 Determination of specific gravity and water absorption of aggregates ........................................... 13

3.6.1 Method for fine aggregates (5mm and below) .......................................................................... 14

3.6.2 Determination of specific gravity and water absorption for coarse aggregates ....................... 16

3.7 Dry-rodded density of pumice .......................................................................................................... 17

3.8 Concrete mix design .......................................................................................................................... 17

3.8.1 Mix Proportioning Methods ....................................................................................................... 17

Background Data required for mix Proportioning .................................................................................. 18

Step-by-Step Procedure of Mix Proportioning Calculations ................................................................... 19

3.9 Control mix ........................................................................................................................................ 203.10 Batching .......................................................................................................................................... 20

3.11 Mixing of concrete .......................................................................................................................... 20

3.12 Slump test ....................................................................................................................................... 20

3.13 Compacting test .............................................................................................................................. 21

3.14 Casting of compression test specimen ........................................................................................... 21

3.15 Curing of the test specimen ............................................................................................................ 21

3.16 Compressive strength determination ............................................................................................. 22

3.17 Selection of a mix for precast concrete casting .............................................................................. 22

3.18 Flexural strength test ...................................................................................................................... 23

3.19 Comparison of pre-casted elements made from normal concrete and pumice concrete ............. 23

4.0 Data collection and Results Analysis ..................................................................................................... 24

4.1 Grading .............................................................................................................................................. 24

4.2 Specific gravity and water absorption .............................................................................................. 27

4.3 Moisture content .............................................................................................................................. 30

4.4 Properties of trial mixes .............................................................................................................. 314.5 Summary of trial mixes ............................................................................................................... 36

4.6 Flexural strength test results ............................................................................................................ 41

5.0 Discussion of results .............................................................................................................................. 43

5.1 Availabity of Pumice .......................................................................................................................... 43

5.2 Grading .............................................................................................................................................. 43


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5.3 Specific gravity .................................................................................................................................. 43

5.4 Water absorption .............................................................................................................................. 43

5.5 Dry rodded density of pumice aggregates ........................................................................................ 44

5.6. Pumice concrete design ................................................................................................................... 44

5.6.1 Slump ......................................................................................................................................... 45

5.6.2 Compacting factor ...................................................................................................................... 45

5.6.3 Density ....................................................................................................................................... 45

5.6.4 Compressive strength ................................................................................................................ 45

5.7 Normal granitic aggregate mix design .............................................................................................. 46

5.7.1 Slump ......................................................................................................................................... 46

5.7.2 Compacting factor ...................................................................................................................... 46

5.7.3 Compressive strength ................................................................................................................ 465.8 Flexural strength ............................................................................................................................... 46

5.9 Comparison and analysis of pre-casted elements made from normal concrete and pumiceconcrete .................................................................................................................................................. 47

5.9.1 Pre- casted pumice structural concrete ..................................................................................... 49

5.9.2 Pumice concrete and eco-sustainability .................................................................................... 50

Chapter 6 ..................................................................................................................................................... 51

6.0 Conclusions and Recommendations ..................................................................................................... 51

6.1 Conclusions ....................................................................................................................................... 51

6.2 Recommendations ............................................................................................................................ 51

7.0 References ............................................................................................................................................ 53

8.0 Appendix ............................................................................................................................................... 54

List of abbreviationsPPC Portland pozzolana cement

Mpa Mega Pascal

ACI American concrete institute

f ′cr Required average compressive strength of concrete (N/mm2)

f ′c Specified compressive strength of Concrete (N/mm2)


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K this value refers to material defects proportion.

S standard deviation of strength test data

BS British Standards

CL Clause

W/C Water Cement ratio

DoE Department of Environment

Tm 1 Trial mix one (0.48 w/c ratio)

Tm 2 Trial mix two (0.54 w/c ratio)

Tm 3 Trial mix three (0.60 w/c ratio)


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List of tables

Table 1: Granitic aggregate grading ........................................................................................................... 24Table 2: Pumice aggregates grading .......................................................................................................... 25Table 3: Fine aggregate grading ................................................................................................................. 26Table 4: Specific gravity and water absorption results for pumice aggregates .......................................... 27Table 5: Specific gravity and water absorption results for granitic aggregates ......................................... 28Table 6: specific gravity and water absorption results for sand ................................................................. 29Table 7: Moisture content of pumice (Tm 1 mixing) ................................................................................... 30Table 8: Moisture content of pumice (Tm 2 mixing) ................................................................................... 30Table 9: Moisture content of pumice (Tm 3 mixing) ................................................................................... 30Table 10: mix proportions for trial mixes (source Tables in the appedix) ................................................... 31Table 11: compacting factor (Tm 1 - 0.48 w/c ratio) .................................................................................. 31Table 12: Average density and strength versus age (Tm 1) ........................................................................ 31Table 13: Compacting factor (Tm 2 - 0.54 w/c ratio) .................................................................................. 33Table 14: Average density and strength versus age (Tm 2) ........................................................................ 33Table 15: Compacting factor (Tm 3 - 0.60 w/c ratio) .................................................................................. 34Table 16: Average density and strength versus age (Tm 3) ........................................................................ 34Table 17: Summary of slump (trial mixes) .................................................................................................. 36Table 18: Compacting factor (selected mix - 0.60 w/c ratio) ...................................................................... 38Table 19: Average density and strength versus age (Selected mix) ............................................................ 38Table 20: Compaction factor (Normal aggregate mix) ............................................................................... 39Table 21: Average density and strength versus age (Normal mix) ............................................................. 39Table 22: Normal concrete mix design table based on procedure by Department of Environment (DoE) -

London ........................................................................................................................................................ 54Table 23: Absolute volume mix design method table based on procedure by American concrete institute(ACI 2000) -TM 1 ........................................................................................................................................ 55Table 24: Absolute volume mix design method table based on procedure by American concrete institute(ACI 2000) -TM 2 ........................................................................................................................................ 56Table 25: Absolute volume mix design method table based on procedure by American concrete institute(ACI 2000) – TM 3 ....................................................................................................................................... 57Table 26: Scaled down trial mixes proportions for actual laboratory casting ............................................ 58Table 27: Trial mix 1 results (casted on) ..................................................................................................... 58

Table 28: Trial mix 2 results (casted on) .................................................................................................... 59Table 29: Trial mix 3 results (casted on) ..................................................................................................... 59

Table 30: Selected mix results (casted on) .................................................................................................. 60Table 31: Normal aggregate mix (Casted on) ............................................................................................ 60Table 32: Slump Ranges for Specific Applications (after ACI, 2000) Table 5.14 .......................................... 61Table 33: Typical State DOT Slump Specifications (data taken from ACPA, 2001) Table 5.15 ................... 61Table 34: Approximate Mixing Water and Air Content Requirements for Different Slumps and Maximum Aggregate Sizes (adapted from ACI, 2000) Table 5.16 ............................................................................... 62Table 35: Water-Cement Ratio and Compressive Strength Relationship (after ACI, 2000) Table 5.17 .... 63


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Table 36: Volume of Coarse Aggregate per Unit Volume of PCC for Different Fine aggregate FinenessModuli for Pavement PCC (after ACI, 2000) Table 5.18 ............................................................................. 63

List of figures Figure 1: A house made from lightweight precast concrete ....................................................................... 6Figure 2: Pumice aggregate .......................................................................................................................... 6

Figure 3: Grading sieves ............................................................................................................................ 12 Figure 4: granitic coarse aggregate grading curve ................................................................................... 24 Figure 5: Pumice coarse aggregate grading curve .................................................................................... 25 Figure 6: Fine aggregate grading curve .................................................................................................... 26 Figure 7: Density variation with age .......................................................................................................... 32

Figure 8: strength development curve: Tm 1 .............................................................................................. 32 Figure 9: Density variation with age (Trial mix 2) .................................................................................... 33 Figure 10: Strength development curve (Tm 2) .......................................................................................... 34Figure 11: Density Variation with age (Tm 3) ............................................................................................. 35

Figure 12: Strength development curve (Tm 3) .......................................................................................... 35 Figure 13: Summary of strength development for the trial mixes ............................................................... 36 Figure 14: 28 day strength versus w/c ratio ............................................................................................... 37 Figure 15: Density versus w/c ratio graph ................................................................................................. 37 Figure 16: Density Variation with age (Selected mix) ................................................................................ 38 Figure 17: Strength development curve (Selected mix) .............................................................................. 39

Figure 18 :Density variation with age (Normal mix) ................................................................................... 40 Figure 19: Strength development curve (Normal Mix) ............................................................................... 40 Figure 20: Comparison of Strength development for pumice and normal aggregate concrete ................. 41


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DedicationI dedicate this work to my loving parents and siblings, most especially to my loving mum who has gonethrough a lot to make me who I am.


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AcknowledgementMy final year’s project would never be were it not for the following people I consider very important andspecial. They did all to advice, teach and assist me get information and the insight of the project. First andforemost Almighty God for his divine love and care. Secondly to My supervisor, Eng. Mang ’uriu for hiscontinuous and insightful technical advice through out each step of study. My sincere gratitude goes to

the chairman of the department of civil, construction and environmental engineering, Prof. W. Oyawa, forfacilitating finances and equipment for research.

Further appreciation to the laboratory team; Mr. Kamami, Mr. Karugu and Mr. Juma among other veryable laboratory staff that went an extra step to make sure we got utmost knowledge and experience inmaterial and other tests.

Last but not least, I thank my fellow classmates, friends and all other people who in one way or anothercontributed to the success of this project. God bless you all.


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AbstractPre- cast concrete has proven to be an efficient method of construction, particularly when time is

considered. It is justifiable to use lightweight concrete to make precast concrete elements. The main

specialties of lightweight concrete are its low density and thermal conductivity. Its advantages are that

there is a reduction of dead load, faster building rates in construction and lower haulage and handlingcosts. This would effectively improve the efficiency of using and installing these elements on site.

Pumice is a natural lightweight aggregate that can be used in production of lightweight concrete for pre-

casting. However, pumice is a special kind of material and absorbs a lot of water. In order to use it in pre-

cast concrete production, design criteria should be established. Its properties and applicability also needs

to be understood.

Therefore, this fundamental study report is prepared to show how with proper materials engineering

education, pumice can be used to provide economic and sustainable solutions to current global housing

crisis.Focus was on the appropriate concrete design method to be used for pumice concrete, its performance in

terms of compressive strength, water absorption and density and supplementary tests and comparisons

with normal weight concrete.


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Chapter 1

1.0 IntroductionThe construction industry is no doubt the most vibrant and dynamic industry in many economies in the

world. The growing rate of population increase has led to an increased demand in space and

accommodation. Engineers have had to shift their approach in design of structures in order to meet the

growing population. These structures have had to conform to existing limitations such as scarce land,

cultural and social factors, economic factors and aesthetic factors.

In the recent years, engineers and architects have designed very complicated structures to meet all these

requirements. Concrete has remained one of the most important construction materials used in many

countries. In Kenya, in the rush to meet the millennium development goals and vision 2030, thegovernment has placed more emphasis on development and use of more eco-sustainable and

environmental friendly materials in construction. It has in the recent past insisted of the maximum use of

the available cheap resources while at the same time checking on quality and most of all, safety of its

people.

1.1 Background

In the use of concrete as a construction material, self weight, especially in the above mentioned situation

of modern and complicated structures, represents a huge proportion of the total weight or load of the

structure. It is without doubt that, from experience and current economic conditions the heavier a

structure is the heavier and expensive the foundation will become. It is also certain that foundation

construction of any structure is the most costly exercise in any engineering project. It is therefore very

true that there are substantial merits in the reduction of the density of construction concrete. One of these

would be reduction of the dead loads and all other loads on structure members. Another would be to

bring down the weight of the concrete units to within the capacities of handling equipment in the case of

precast members and their fitting. This would substantially in turn reduce the size of foundations and

automatically reduce the costs. Therefore the incorporation of lightweight aggregates as structural

concrete constituents would be primarily on economic and efficiency considerations.

Light weight aggregates have been used since time in memorial in construction as structural concrete,

aesthetical concrete among many other uses. Lightweight aggregates as the name suggests have unique

properties that an engineer has to put into consideration when using them. There are many types and kinds

of light weight aggregate majorly natural lightweight aggregates and artificial or manmade lightweight


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aggregates. Pumice is an example of natural lightweight aggregate that is available in Kenya. Pumice is a

light colored froth like volcanic material found mainly in areas that have experienced volcanic activity in

the past.

In this study, lightweight concrete made using pumice will be used in pre-cast elements.

1.2 Problem statementThe rising need for accommodation and scarcity of space has resulted in the design and construction of

complicated structures that are very heavy. These structures are very expensive. This therefore calls for

the reduction of the overall cost of construction by reducing costs related to heavy superstructures while

striving to meet the population’s demand of accommodation.

1.3 Problem justificationThe essential requirement of any construction medium is strength, durability, fire resistance and the value

for money. On all these counts, pre-cast lightweight concrete made with pumice appears to be a very

sustainable material. The study will try to establish the practicality of using precast concrete elements

with pumice aggregates to reduce loads.

1.4 Objectives

1.4.1 Overall objectiveThe overall objective would be:-

To investigate the feasibility of using pre-cast concrete elements with pumice as aggregates and their

significance in load reduction in structures

1.4.2 Specific objectives To study and investigate the properties of pumice concrete and compare it with normal concrete.

To establish a pumice concrete mix that can be used in modern structures.

To determine whether the incorporation of pumice concrete in structural elements can

significantly reduce dead loads of a super structure and the associated economic implications.

1.5 Project hypothesis

Use of precast concrete with pumice as total and partial replacement of normal coarse aggregates reducesthe dead load in concrete superstructures substantially hence reducing the overall cost of construction

while maintaining the structural soundness.


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1.6 Scope and limitation of study

1.6.1 ScopeThe study will cover the following:-

Investigation of the availability of pumice in Kenya and its material and structural properties.The feasibility and viability of pumice concrete in reduction of overall density.

Designing a typical mix for precast elements, and recommend a method of design.

Establishing the economic and environmental impacts of incorporating pumice in modern

construction.

Analyze the significance of using pumice in partitions, hollow ports and other fittings and overall

effects on the weight of superstructure.

The following mixes will be dealt with:-

Normal aggregates with ordinary sand as control concrete (Mix A).

Pumice aggregates with ordinary river sand concrete (Mix B).

1.6.2 LimitationsThough it would be necessary to test analyze the use of different types of cements in the project, time

factors will limit the study to only use of Portland Pozzolana cement (PPC; 32.5N). Factors such as

durability of concrete and carbonization will also not be covered because of limited time. Some structural

implications of joints and their design will not be dealt with.


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Chapter 2

2.0 Literature review

2.1 General overview of pre-castingPre-cast units are components of buildings and structures which are pre-formed and made available foruse at site. Such precast units can be classified as small or large depending on their sizes and weights(A.M HAAS).

Pre-casting generally involves the division of a continuous structure into pieces. These pieces are thenassembled carefully to form the structure. This therefore calls for adequate design to cover these. Carefulstudy and design of the concrete to be used therefore remains the core challenge in this project.

Lightweight concrete has been used previously in pre-fabricated construction. Pre-casting or prefabrication in reinforced concrete involves a mould shaped in a way that reinforcement is placed and

concrete is then cast. Such casting is done in a factory or at a fixed location on site. The completedelements are then finally transported to the erection area.

2.2 Benefits of pre-castingEconomy in the use and cost of formwork and scaffoldingWhen elements are pre-cast, few moulds are used repeatedly to produce similar elements. This iscontrary to cast insitu work where formwork is required for the entire structural element. Theamount of scaffolding will be reduced since few people will only be required up in the building toaid in fixing members being fitted. This therefore reduces the cost of formwork that would berequired in the case of casting in situ.Encourages conservation of available forest resources.

In Kenya today, the major type of formwork and scaffolding used comes from timber and timber products. This is because timber is relatively cheap and available. This means that for everyconstruction being done, several trees are cut. Trees are an important part of our ecology andthere is a global call for the restoration of forest cover and closer home, efforts are being done toreclaim water towers like Mau, Mt. Kenya, Mt Elgon, Aberdares and Cherengani hills amongmany others. It is without doubt that if pre-casting is encouraged, fewer trees will be cut forformwork.Results in reduced building time.Pre-casting of elements such as beams and slabs can be done simultaneously with otherconstruction activities like foundation construction, walling and partition work. When the pre-castelements are fixed, construction continues since time for curing and demolition of formwork isnot required.

Provides possibilities of closer control of construction activities.Pre-casting allows for quality control in concrete mixtures, with parameters such as homogeneityof mixes, workability, placing, compaction and curing being closely monitored by an appointedclerk.Enhances good workmanship.


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With pre-casting, workmanship is closely monitored and it is possible to monitor individualworkers and monitor their output.Allows utilization of skills.In pre- casting individual capabilities are utilized for instance, a carpenter or fabricator will makemoulds; a mason will ensure units are laid correctly. This therefore encourages specialization.

Maximum re-use of mould work equipment.A single mould can be used repeatedly to cast many other similar elements. This thereforeeliminates the need for repetitive fabrication of moulds.Provides continuity of construction process.Pre-casting allows construction to proceed since unnecessary stoppages like allowing for casted

parts to get cured and develop strength and lack of working space due to scaffolding and propsand formwork support are eliminated.Reduced delays due to unfavorable weather conditions.Pre- casted elements can be made from a workshop and the activity is not affected by uncertainweather conditions such as rain, snow and sunlight. Some important activities like casting of slabsare usually interrupted with sudden downpours, sunlight in cast insitu works. This interferes withthe program and even the integrity of work. Such incidents are not common in pre-castedconstruction.

2.3 Pre-cast elements and lightweight concreteStructural lightweight concrete may be regarded as concrete having strength at least in excess of 10 Mpaand perhaps more importantly having a good degree of durability. Such concrete is likely to have adensity of in the range of 1200 – 2000 kg/m 3.

In the use of precast elements in construction, pumice aggregates make the whole concept veryadvantageous and effective. Pumice aggregates in precast concrete elements reduce the weight of theelements substantially. This in turn increases efficiency in handling, erecting and fitting these elementstogether. It also facilitates faster building rates, and lower hauling costs as stated above. In other words, itis possible to use available cheap handling and lifting equipment.

The weight of a building on the foundations is an important factor in design, particularly now that thetrend is the construction of high rise buildings. The use of lightweight concrete has sometimes made it

possible to proceed with a design which otherwise would have had to be abandoned on the score ofweight (A. Short 1968). In framed structures, the frame has to carry the load of the floors and walls andconsiderable savings in cost can be brought about by using lightweight concrete for floors, beams andwalling.

It has been shown experimentally and by practical experience in the industry that faster building rates can be achieved with lightweight concrete than with the more traditional materials, and for this reason many builders today are prepared to pay considerably more for lightweight concrete units than for traditionalalternatives, for the same wall area (William Kinniburgh 1968).


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F igur e 1: A h ouse made from l ightweight precast concrete 2.4 Pumice

Pumice is a locally available material. It is also well spread on global basis. Pumice is the oldest knownlightweight aggregate and from 100 B.C. onwards was commonly used as an aggregate in the concreteroofs and walls of Roman buildings; Pumice is used for reinforced concrete slabs, mainly for industrialroofs in Germany. With a density of about 700- 1200kg/m 3, pumice used in concrete elements can reducedead loads by over 30% and hence reduce the overall weight of structures.

Figure 2: Pumice aggregate

2.5.1 Properties of pumiceIn the design of precast concrete elements made with pumice, an engineer will have to consider material

properties of pumice and the concrete mix design to achieve strength required. The challenge would bethe task of designing the strength and providing for connections. Aggregate used for concrete work must

produce concrete that is adequately strong and is capable of satisfactory compaction; it must be durableand free from harmful ingredients (A. Short 1968).

Several studies have been done on pumice as an aggregate in concrete have shown that it is a soundmaterial in structural concrete. The task is to enforce a suitable and sound quality control and


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management (T. EIGAWA 1992). A less obvious but none the less one of the striking features oflightweight concrete is the relatively high insulating values which they exhibit, a property whichimproves with decreasing density. Pumice aggregates are very porous than gravel and so have absorb agreat deal of more water during the making of the concrete (A. Short and William Kinniburgh 1968).

Although slightly higher fines content may be necessary, structural lightweight concrete is generallyamenable to a mix design process similar to that for normal weight concrete. Sometimes it is better to usevolume batching for lightweight material. This would apply where moisture will vary substantially (J.LClarke 1993).

Pumice concrete is not in general suitable for cast in-situ work because of the tendency for this aggregateto float to the surface, leading to segregation of the mixture. In its natural state pumice usually containsimpurities and if used with reinforcement it must be washed before mixing (A. Short 1968).

2.5 Mix designUnfortunately the state of the art in concrete material science has not yet advanced to the point where wecan rationally determine the expected strength of concrete even if we were provided with all conceivableinformation about the constituent materials and their properties. Concrete mix design therefore is a highlyempirical subject so much so that it is necessary to produce trial mixes from which then final mix design

parameters can be designed. (Christian Meyer).

The design of a concrete mix can be defined as the selection of the most suitable materials, i.e. cementand aggregate, and the most economical proportions of cement, water and the various sizes of aggregates,to produce a concrete having the required physical properties.

The design of lightweight concrete mixes differs considerably from that used for normal dense concretemixes. In many instances, the functional requirements are not merely those of strength and workability, asin normal structural concrete, and each lightweight aggregate must be separately considered. TheEngineer must be satisfied when specifying a standard mix for the structural.

2.5.1 Objectives of mix designThe objective of mix design is to determine the mix proportions such that the resulting concrete has aspecified strength and meets specific durability requirements. Actually this objective involves threeseparate goals:-

1. To achieve the specified strength and durability requirements.2. To assure that the mixture is workable.3. To minimize the amount of cement, the most expensive ingredient of the mix.

Mix designs usually are based upon volumetric measurements, but concrete is usually mixed (at least in acommercial setting) according to weight of materials. Therefore, a mix design most commonly givesdirections for making the mix based upon weight (www).

A very simple method for mixing concrete is the "1:2:3" method. This type of concrete would use one part of cement, two parts of fine aggregate (sand), and three parts of coarse aggregate (gravel). To thismixture is added enough water to bring the concrete to the desired consistency. This will make a goodconcrete, but it is rather inefficient, since it tends to use more cement than is necessary.


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As shown in the above example, a mix design will usually give direction as to the quantity of cement,coarse aggregate, fine aggregate, and water in a specified amount of concrete (usually m 3). A mix designwill also give directions as to amounts of admixture such as air entraining agents, water reducers, orcorrosion inhibiting agents.

The first step in creating a concrete mix design is to determine the desired compressive strength of thefinished concrete. This is expressed in terms of the 28-day compressive strength; the strength the concretewill achieve in 28 days. This is usually based upon statistical data of similar mixes, or there are acceptedformulas that will account for statistical variations in concrete strengths if data is not available.

After determining the design strength, a water-cement ratio is selected. The common source for this is the American concrete institute (ACI) code, Portland cement Association's Design and Control of Concrete Mixtures and the British department of environment standard manuals for designing concrete. In thesemanuals, tables are available, which show various water contents per cubic meter for varying levels ofslump, coarse aggregate size, and air entrainment. So we now have the amount of water in the mix, and itsratio to the cement. The amount of water is divided by the water-cement ratio, yielding the weight ofcement needed for the mix.

Water and cement will make the "paste" that holds the aggregates together. The aggregate selection begins by consulting relevant tables which relates maximum aggregate size of the coarse aggregate, andfineness modulus of the fine aggregate to show the volume of coarse aggregate per unit of volume ofconcrete (www).

After the volume of coarse aggregate has been determined, the weight of each material (water, cement,and coarse aggregate) per cubic meter of concrete is converted to volume through the use of specific

gravity. The total of these is then subtracted from one cubic meter, and the difference made up using fineaggregate.

This is a general outline of the process for designing a concrete mix. There are other concerns, such as airentrainment levels, sulfate resistance, aggregate sizing, and mix water characteristics, which must also beconsidered.

Sometimes a mix design can be developed by experience or previously collected field data to arrive at arequired strength of concrete. Though this approach will not be used, it is briefly described here below.

Proportioning from Field Data

This approach consists of adopting the previously used concrete mixture design for a new project provided that the following requirements are met:Strength-test data and standard deviations of strength test data collected from field showthat the previously designed mixture is acceptable.The statistical data should essentially represent the same materials, proportions, andconcreting conditions to be used in the new project.The data used for proportioning should also be from a concrete with an f c′ within therange of the strength of concrete required for the new project


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The data should represent at least 30 consecutive tests or two groups of consecutive teststotaling at least 30 tests (one test is the average strength of two cubes or cylinders fromthe same samples)Durability requirements must also be met.

If all the above requirements are met the previous mixture design may be approved for the new project provided that the specified compressive strength of concrete, f ’cr is equal to or greater than the requiredaverage compressive strength, f ′cr , of concrete, calculated as follows:

The f ′cr will be obtained from the following equation:-

f ′cr = f ′c + kS

Where

f ′cr =required average compressive strength of concrete (N/mm2) to be used as the basis for

selection of concrete proportions

f ′c = specified compressive strength of Concrete (N/mm

2

)

S = standard deviation of strength test data, expression of S is given in the DoE booklet and is provided in the Appendix of this document.

K= this value refers to material defects proportion. It is also provided in DoE booklet andappendix of this document.

If the f ′c is less than f ′cr, or statistical data or test records are insufficient or are not available, the mixture

should be proportioned by the trial-mixture method.


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Chapter 3

3.0 MethodologyThe following was done during the study:-

1. Determination of pumice availability

2. Collection and sampling of material.

3. Grading of materials according to BS 882 and other associated codes.

4. Carrying out of the specific gravity tests.

5. Establishing of mix designs (trial mixes) for different blends i.e.

Normal aggregates with ordinary river sand fines concrete.

Pumice aggregates with ordinary river sand fines concrete.

6.

Establishing the properties of green concrete in the above listed mixes and casting of cubes fortesting at different ages.

7. Establishing the properties of hardened concrete (Concrete cubes and beams) of the above listed

mixes.

8. Casting of reinforced beams of the above mixes and testing their flexural strength variations.

3.1 A survey of pumice availabilityThe availability of pumice aggregate and its distribution in Kenya was determined. This involved study of

geological and soil maps available. It involved checking on available publications on this material in

libraries. It also involved the consultation of respective experts and scholars in the geology department.

3.2 Collection and sampling of materialPumice was collected from one of the quarries in the Great Rift Valley. The quarries were found around

Kijabe, Mai -Mahiu, Longonot, Suswa and many parts around Nakuru.

Ordinary granitic aggregates were obtained from quarries around college. Ordinary river sand was

obtained from local suppliers. It was ensured that these materials were of quality and with negligible

defectives.

Aggregates of sizes 20mm were used for the study. Pumice naturally occurs with ashes, clay and other

deleterious materials.

For design purposes, the aggregates were washed to remove the dust and deleterious materials.


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3.4 Sampling of materialsThe material was sampled to obtain representative samples. Sampling was done by the riffling box

method. The method is described here below.

The box was assembled and placed on a flat surface. The material was then scooped using a hand shovel.

The scooped material was then poured on top of the box till the collecting boxes below were full.

The material on one of the two receiving containers was discarded and the material in the remaining

container re- introduced in the box as described above.

The material on one of the receiving containers was taken as a representative material for testing.

3.5 Grading of materials for concrete productionIn order to design and produce a concrete mix, it is important that the grading of the constituents be done.

This is done on coarse and fine aggregates to establish whether the particular particle distribution of a

batch is good for concrete production. This then enables the materials engineer to choose the source of his

materials (quarry and river).

Grading for ordinary material was done using the British standards (BS 882: 1992 specification for

aggregates from natural sources for concrete).

The code gives the sieves and envelopes (bounds) or limits required for coarse and fine aggregates.

3.5.1Coarse aggregateCoarse aggregate is defined as aggregate mainly retained on a 5.0 mm BS 410 test sieve and containing

no more finer material than is permitted for the various sizes in this specification (CL 2.2).

Coarse aggregate may be described as gravel (uncrushed, crushed or partially crushed) as defined in 2.2.1,

or as crushed rock as defined in CL2.2.2, or as blended coarse aggregate as defined in CL2.2.3.

In this project the pumice collected occurs naturally as uncrushed material. The ordinary granite is a

product of crushed rock.

When determined in accordance with BS 812-103.1 using test sieves of the sizes given in Table 3,

complying with BS 410, full tolerance, the grading of the coarse aggregate was to be within the

appropriate limits given in Table 3 of BS 882. The material used was 20 mm and below.


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3.5.2 Fine aggregatesWhen determined in accordance with BS 812-103.1, using test sieves of the sizes given in Table 4

complying with BS 410, full tolerance, the grading of the sand was to comply with the overall limits

given in Table 4. Additionally, not more than one in ten consecutive samples was to have a grading

outside the limits for any one of the grading C, M or F, given in Table 4 (CL 5.2.1).

The method of grading for both fines and coarse aggregates is described here below:-

F igur e 3: Gr ading sieves

Object

To determine the particle size distribution of aggregates by sieving

Apparatus

Balance accurate to 0.5% of mass of test sample.

Test sieves as listed a below

Oven capable of maintaining constant temperature to within 5%

Mechanism of shaking sieves.


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Chart for recoding results.

Sieve sizes

Coarse aggregates: 50mm, 37.5mm, 20mm, 14mm, 10mm, 5mm and 2.36mm.

Fine aggregates : 10mm, 5mm, 2.36mm, 1.18mm, 0.6mm, 0.3mm and 0.15mm

Procedure

The test samples were dried to a constant mass by oven drying at not more than 105±5 0C

An approximate sample was taken from the original sample by riffling.

It was ensured that the sieves wert dry and clean before using them.

The required sample was then weighed out.

The sieve of the largest mesh size was placed in the tray and the weighed sample put on to the sieve.

The sieve was shaken horizontally with a jerking motion in all directions for at least 2 minutes and until

no more than a trace of a sample was passing. It was ensured that all material passing fell into the tray.

All material retained on the sieve was weighed.

The results were tabulated in the table provided and the cumulative weight passing each sieve calculated

as a percentage of the total sample to the nearest whole number.

The grading curve for the sample was plotted in the grading chart.

3.6 Determination of specific gravity and water absorption of aggregatesSpecific gravity also known as particle density is an important parameter in the design of a concrete mix.

It helps in the determination of the overall density of final concrete produced.

In the project, specific gravity was done in accordance with BS EN 1097: part 6 2000(Test for mechanical

and physical properties of aggregates).

The pycometer method was used for determination of specific gravity and water absorption for fine

aggregates ( CL 9 ), while the wire basket method was used in the determination of specific gravity and

water absorption of coarse aggregates (Annex c – determination of particle density and water absorption

for lightweight aggregates).


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The parameters that would be required at the end of the test were as stated below:-

1. Particle density on an oven- dried basis

Ratio of oven dried sample of aggregates to the volume it occupies in water including both

internal sealed voids and water accessible voids ( CL 3.2 ).

2. Apparent particle density

Ratio of oven dried mass of sample of aggregated to the volume it occupies in water including

any internal sealed voids but excluding water accessible voids ( CL3.3 ).

3. Particle density on a saturated surface -dry basis

Ratio of the combined mass of a sample of aggregate and the mass of water in the water

accessible voids to the volume it occupies in water including both internally sealed voids and

water accessible voids if present ( CL 3.4 ).

4. Water absorption

Increase in mass of a sample of oven dried aggregate due to the penetration of water into the

water accessible voids ( CL 3.6) .

The methods are described here blow:-

3.6.1 Method for fine aggregates (5mm and below)Object

To determine the specific gravity and the water absorption values of aggregates.

Apparatus

i. A balance

ii. A drying oven

iii. A pycometer bottle

iv. Sample containers

v. Stirring rod

Sample for test

A sample of about 500g was used for aggregates less than 5mm.

The sample was thoroughly washed to remove all material finer than 0.075mm test sieve as follows:-

The test sample was placed in the tray and enough water added to cover it. The sample was agitated

vigorously and immediately poured over the sieve which had previously been wetted on both sides. The


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operation was repeated until the wash water was clear. All material retained on the sieve was returned to

the washed sample.

Procedure

Transfer the washed sample to the tray and add further water to ensure that the sample is completelyimmersed. Ensure that the sample is completely immersed.

The sample was kept immersed in water for 24 hours. The aggregate was placed in the pycometer and

filled with water.

The cone was screwed in to place and any entrapped air eliminated by rotating it on the sides.

The bottle was dried on the outside and weighed as (A).

The sample was emptied in to the tray; the pycometer refilled with water to the same level as before,

dried on the outside and weighed as (B).

Water was carefully drained from the sample by decantation through a 0.075mm sieve and any material

retained returned to the sample.

The aggregate was exposed to a gentle current of warm air to evaporate surface moisture and was stirred

at frequent intervals to ensure uniform drying until no free surface moisture could be seen. The saturated

and surface dry sample was then weighed as (C).

The sample was placed in the tray and dried in an oven at a temperature of 104 – 105 C for 24 hours. It

was then cooled in a dessicator and weighed as (D).

Calculations

i. Specific gravity on an oven dried basis

=

ii. Specific gravity on a saturated and surface dried basis

=

iii. Apparent specific gravity

=

iv. Water absorption (% of dry mass)

=


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3.6.2 Determination of specific gravity and water absorption for coarse aggregatesApparatus

(i) Double beam balance of capacity 5kg

(ii) Container of steel or enameled iron with rubber plate.

(iii) Wire basket of opening 3mm or less, dia 20 cm and height 20 cm.

Preparation of sample

A representative sample was obtained by quartering or riffling.

The weight of the sample was to be 2kg for less than 20mm aggregates.

The sample was washed thoroughly with water to remove the dust on the surface of the grain and then

soaked in water at 25 C for 24 hours.

The specimen was removed from water, shaken off, and rolled in large absorbent cloth until all the

visible films of water were removed.

The large particles were wiped individually. The sample was divided into two parts to be used each for

one test.

Procedure for testing

The sample was weighed to the nearest o.5 g (Ws).

The sample was then placed in the wire basket, immersed in water at room temperature, and tapped to

remove entrapped air on the surface and between the grains and weighed while immersed (Ww).

The sample was removed from the water, dried in drying oven to constant weight at the temperature of

105 C and cooled at room temperature and weighed to the nearest 0.5g (Wd).

Results

The results were calculated as follows:-

(i) Specific gravity on saturatedsurface dry basis

=

(ii) Absolute dry specific gravity

=

(iii) Water absorption (% of dry weight)


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=

3.7 Dry-rodded density of pumiceThis is the weight of aggregate that would fill a container of unit volume. It is used to convert quantities

by weight to quantities by volume.

Dry aggregates were gently placed in the container of known volume in three layers and each layer

tamped a prescribed number of times with a 16mm diameter round nosed rod. The overflow was removed

by rolling a rod across the top of the container. The net weight of the aggregates in the container was

divided with the volume of the container to obtain the dry rodded density.

3.8 Concrete mix designConcrete mix design was carried out to determine the proportions of constituents of concrete that was to

meet the desired strength and other properties. This was done according to accepted standards and

specifications.

Mix design enabled choosing of a mix that was recommended in the casting of precast element for testing.

It entailed coming up with adequate water/ cement ratio that would give adequate compressive strength.

3.8.1 Mix Proportioning MethodsVarious mix proportioning methods have been developed that are used in mix proportioning.

The following two methods have been described in the ACI Committee 211 standard practice for

proportioning of concrete mixes

Weight method

Absolute-volume method

3.8.1.1 The Weight-proportioning method

This is fairly simple and quick for estimating mix proportions using an assumed or known weight of the

concrete per unit volume (i.e. Density).

This method was used to design the normal weight mix that was used in the project as control mix and towhose other mixes was compared to.

3.8.1.2 The Absolute-volume-proportioning method

This is a more accurate method and involves use of specific gravity values for all the ingredients to

calculate the absolute volume each would occupy in a unit volume of concrete.


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This method is usually used in the design of concrete with constituents of special or different properties

from those of normal constituents.

In this project, the absolute-volume method, was used since pumice, a lightweight material was being

dealt with. There are two approaches in this method. These are:-

Mix proportioning from field data

Mix proportioning by trial mixtures

It may be noted that any mix design method provides only a first approximation of proportions. This has

to be checked by trial batches in the lab.

In the project, the second approach was used. This is because of unavailability reliable field data to

support the first approach. The trial mixture is described here below:-

Proportioning by Trial Mixtures

Involved, first establishing the relationship between strength and w/c ratio for the materials to be

used in the concrete.

This relationship was then used for proportioning the concrete ingredients using an appropriate

method.

The strength versus w/c ratio curve was established by preparing the three mixtures with three

different w/c ratios to produce a range of strengths that encompass f ′cr

The mixtures were prepared using the same materials proposed for the work

The mixtures were to have a slump and air content within 25 - 50m and 2%, respectively.

Three cubes per w/c ratio were made and cured.

At 28 th day test age, the compressive strength of concrete was determined by testing the cubes in

compression

The test results were plotted to produce strength versus w/c ratio curve that was used to

proportion an appropriate mix for the pre-casting exercise.

For required average compressive strength of concrete, f ′cr , the w/c ratio was obtained using ACI

method.

Background Data required for mix Proportioning

The following background data was gathered before starting the mix proportioning calculations:Sieve analysis of fine and coarse aggregate; fineness modulus

Dry-rodded unit weight of coarse aggregate

Bulk specific gravity of materials

Absorption capacity, or free moisture in the aggregate


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Variations in the approximate mixing water requirement with slump, air content, and grading of

the available aggregates

Relationship between strength and w/c ratio for available combinations of cement and aggregate

Job specifications if any [e.g., maximum w/c ratio, minimum air content, minimum slump,

maximum size of aggregate, and 28-day compressive strength]. In this case the precast elements

would require class 15- 20 concrete.

Step-by-Step Procedure of Mix Proportioning Calculations

The required compressive strength of concrete was determined by a suitable criterion (the DoE

Method was used in this case i.e. f ′cr = f ′c + kS

The w/c ratio was then selected (the ACI tables was adopted in this project and ratios 0.48, 0.54

and 0.6 were used).

The maximum size of aggregate was selected.The air content was then selected.

The slump was selected.

The water content was then selected.

The cement content was then selected.

The coarse-aggregate content was calculated.

The air content was calculated.

The fine-aggregate content was calculated as:

Weight of fine aggregates for a given vol. of concrete= absolute vol. of fine agg. sp. gravity unit weight of water

Absolute vol. of fine aggregate

= Vol. of concrete – sum of absolute volumes of water, cement, air, and coarse aggregate

Absolute vol. of an ingredient of concrete except air

= (weight of ingredient) / (sp. gravity of

Ingredient unit weight of water)

Absolute vol. of air= (% air content vol. of concrete) /100

The weight of water, fine aggregate and coarse aggregate was corrected to compensate for the

moisture in the aggregates

The calculations for laboratory trial batch were made and the concrete produced.


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The slump, air content, unit weight and 28-day compressive strength of the produced concrete

mix was measured.

the batch re-adjustments were done till the desired slump, air content, and 28-day compressive

strength were achieved

3.9 Control mixA normal concrete mix design was done for the normal granitic aggregates and was used in this project as

the control. The procedure was as described here below:-

Stage 1 selection of target water/ cement ratio

Stage 2 selection of free water content.

Stage 3 determination of cement content.

Stage 4 determination of total aggregate.

Stage 5 selections of fine and coarse and aggregate contents.

3.10 BatchingBatching involves proportioning the material or the constituents of concrete to produce the concrete. The

batches were done according to the mix design results. These proportions were reduced to a volume

corresponding to the amount of concrete required. The size of the mix is arranged so that there was a

percentage extra to cater for waste.

3.11 Mixing of concreteAfter mix design of three mixes of different water cement ratio, the trial mixes the trial mixes were done

and their properties as fresh concrete established. The mixing was done by hand using a pan. A pan mixercould be used instead. The interior surfaces of the pan or mixer were cleaned and then wetted a bit. The

ingredients of concrete were added in a definite order so that the total quantity of one particular material

or grading was not added all at once. Mixing was continuous and it was ensured that all material formed a

homogeneous mix.

3.12 Slump testThis is a well established test that was carried out in the form of a frustum of a cone having an upper

diameter of 100 mm, and a lower diameter of 200 mm and a height of 300 mm. The mould was placed in

a smooth, horizontal, vibration free and non -absorbent surface and was filled in three equal layers with

the concrete to be tested, each layer being tamped 25 times with a standard tamping rod. The top layer

was struck off level with the mould and the cone was immediately lifted and amount of by which concrete

slumps was measured. It was important that the cone was lifted truly vertical. The slump was measured

using a steel rule. The inside of the mould was made free from superfluous moisture.


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3.13 Compacting testThis test was used to determine the compacting factor. The test is designed to apply a given amount of

work to a given amount of concrete and to reduce to a minimum the work lost in overcoming the friction

between the concrete and the containing surfaces.

The apparatus consisted of two conical hoppers fitted with strong doors at their base and a cylinder below

them. The top hopper was filled with concrete to be tested using a scoop ensuring not to compact it to any

extent.

The door at the bottom of the top hopper was then opened and concrete allowed to fall in to the bottom

hopper, care was taken to see that no concrete fell to the cylinder below during this process. The concrete

was then allowed to fall into the cylinder by opening the door at the bottom of the second hopper. The

cylinder was leveled off without compacting it in any way. The cylinder was then weighed and recorded

as w.

The cylinder was then emptied and filled with compacted concrete. The cylinder was again weighed and

recorded as W.

The compacting factor was computed as w/W.

3.14 Casting of compression test specimenCompressive strength is the primary physical property of concrete (others are generally defined from it),

and is the one most used in design. It is one of the fundamental properties used for quality control for

lightweight concrete. Compressive strength may be defined as the measured maximum resistance of a

concrete specimen to axial loading. It is found by measuring the highest compression stress that a test

cylinder or cube will support.

The mixes were then be used to cast cubes for testing. This was done according to BS 1881 part 108 -

1983. Ten cubes were casted for each mix. The cubes were crushed to determine the strength

development at different ages.

3.15 Curing of the test specimenThis was done according to the British practice (BS 1881 Part 111). The test specimen was cured 16 – 24

hours after casting. This was done at a constant temperature of about 20 – 220 0C and relative humidity of

about 90 %.


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3.16 Compressive strength determinationThe test cubes were crushed using a universal test machine complying with BS 1881 part 115 – 1986

specifications.

The testing procedure was as described in BS EN 12390-3: 2003 as below:-

The test cube was removed from the curing tank and the excess moisture from the surface of the specimen

wiped and weighed before placing it on the testing machine.

All testing machine bearing surfaces were wiped clean and any loose grit or other extraneous material

removed from the surfaces of the specimen that was in contact with the platens. The cube specimens were

then placed in a way that the load was applied perpendicularly to the direction of casting. The specimen

was centered with respect to the lower platen to an accuracy of ± 1 % of the designated size of cube. A

constant rate of loading within the range 0, 2 MPa/s (N/mm2 _ s) to 1,0 MPa/s (N/mm2 _ s) was selected.

The load to the specimen was applied without shock and is increased continuously, at the selected

constant rate ± 10 %, until no greater load can be sustained. This load was recorded.

The crushing was done as follows:-

3 cubes for 7th day strength




The 28 day strength was plotted against the respective water cement ratios to obtain a curve that aided in

selecting the best mix for concrete that was used in pre-cast elements.

3.17 Selection of a mix for precast concrete castingIn order to precast, a suitable mix had to be selected from the mixes above aided with the water/ cement

ratio versus 28th day strength curve drawn as stated above. Among the important parameters considered

were:-

Strength

Water/ cement ratio

Density

Workability


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The selected mix was then prepared and its properties determined as described in the above procedures.

An additional test; the flexural strength test was done on this selected mix. This was done according to BS

1881 and as described here below:-

3.18 Flexural strength testBeams of size 100mm x 100mm x 500mm were casted and tested on a span of 400mm as in BS 1881 part

109 -1983. These beams were tested using the compression test machine with a special adaptor for

flexural test.

The specimen was placed in the machine, correctly centered with the longitudinal axis of the specimen at

right angles to the rollers. The mould-filling direction was placed normal to the direction of loading.

Loading was not started until all loading and supporting rollers were in contact with the test specimen.

The load was then applied steadily and without shock at such a rate as to increase the stress at a rate of

about 0.06 ± 0.04 N/ (mm2·s). Lower loading rates were used for low strength concretes and the higherloading rates for high strength concrete. Once adjusted, the rate of loading was maintained without

change until failure occurred. The maximum load read on the scale was recorded as the breaking load.

3.19 Comparison of pre-casted elements made from normal concrete and pumice concreteFrom the above determined concrete mix and the above tested properties of the mix, a comparison and

analysis of using pumice and normal aggregates was done. The two materials were compared by the

following parameters:-

WeighDensity

Flexural strength


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4.0 Data collection and Results AnalysisIn this chapter, focus was on the performance of concrete made from pumice aggregates. All the tests

method adopted were as described in the previous chapter. The results presented in this chapter regarded

the compressive strength test, density, moisture content, and water absorption for different trial mixes of

the lightweight concrete and comparison to normal concrete.

4.1 GradingSieve sizes (mm) Wt. retained (g) Wt. passing (g) % retained Total % passing

38.1 0 5112 0.0 100.0

19 1642 3470 32.1 67.9

13.2 1084 2386 21.2 46.7

9.5 1698.5 687.5 33.2 13.4

4.75 636.5 51 12.5 1.02.36 42.5 8.5 0.8 0.2

1.18 8.5 0 0.2 0.0

Table 1: Granitic aggregate grading

F igur e 4: grani tic coarse aggregate grading cur ve

-20.0

0.0

20.0

40.0

60.0

80.0

100.0

120.0

1 10 100

C u m u

l a t i v e % P A S S I N G

Sieve sizes

COARSE AGGREGATES SIEVE ANALYSIS BS 882:1992

Series1

Limits

Limits


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Sieve sizes (mm) Wt. retained (g) Wt. passing (g) % retained Total % passing

1350 100

20 15 1335 1.1 98.9

14 350 985 25.9 7310 643 342 47.6 25.4

5 295 47 21.9 3.5

2.36 47 3.5

1.18

total 1350

Table 2: Pumice aggregates grading

F igu re 5: Pumice coarse aggregate gradi ng curve

0

20

40

60

80

100

120

1 10 100

c u m u

l a t i v e %

p a s s i n g

sieve sizes (logarithmic)

BS 882 lower bound

BS 882 upperbound

pumice grading


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Sieve sizes (mm) Wt. retained(g)

Wt. passing(g)

% retained Cumulative %retained

Cumulative % passing

5.0 40.5 1496.00 2.64 2.64 97.36

2.0 47.0 1449.00 3.06 5.69 94.31

1.18 210.0 1239.00 13.67 19.36 80.64

0.6 419.5 819.50 27.30 46.66 53.34

0.3 537.0 282.50 34.95 81.61 18.39

0.2 215.5 67.00 14.03 95.64 4.36

0.1 67.0 0.00 4.36 100.00 0.00

Total 1536.5

Table 3: Fine aggregate grading

F igur e 6: Fi ne aggregate grading cur ve

0.00

20.00

40.00

60.00

80.00

100.00

120.00

0.0 0.1 1.0 10.0

C u m u

l a t i v e % P a s s i n g

Sieve Sizes

Fine Aggregate Sieve Analysis

sand grading

lower BS 882 bounds

upper BS 882 bounds


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4.2 Specific gravity and water absorptionPumice coarse aggregates

A B Av.

Weight of wire basket (a) 398 398.5

Weight of wire basket +

aggregate (b)

493 477

Weight of aggregate in water

(a+b) (Ww)

95 78.5

Weight of saturated surface

dry sample (Ws)

454 422

Weight of oven dried sample

(Wd)

355 327

Specific gravity on saturated

surface dry basis =

1.26 1.23 1.25

Absolute dry specific gravity

=

0.99 0.95 0.97

Water absorption (% of dry

weight) =

27.9 29.1 28.5

Table 4: Specific gravity and water absorption results for pumice aggregates


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Granite coarse aggregatesA B Av.

Weight of wire basket (a) 420 417

Weight of wire basket +aggregate (b)

1015 1020

Weight of aggregate in water

(a+b) (Ww)

595 603

Weight of saturated surfacedry sample (Ws)

983.5 1003

Weight of oven dried sample(Wd)

963 984

Specific gravity on saturatedsurface dry basis =

2.53 2.51 2.52

Absolute dry specific gravity=

2.36 2.46 2.41

Water absorption (% of dryweight) =

2.1 1.9 2.0

Table 5: Specific gravity and water absorption results for granitic aggregates


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Ordinary SandSample A Sample

BAv.

Weight of jar + sample + water (A) 1706 1734.5

Weight of jar +water (B 1417 1417

Weight of saturated surface drySample (C)

460 505.5

Weight of oven dried sample (D) 457.5 503.5

Specific gravity on an oven driedbasis =

2.68 2.68 2.68

Specific gravity on a saturated andsurface dried basis =

2.69 2.69 2.69

Apparent specific gravity=

2.71 2.71 2.71

Water absorption (% of dry mass)

=

0.55 0.40 0.48

Mean valuesSpecific gravity on anoven dried basis

2.68

Specific gravity on a saturatedand surface dried basis 2.69

Apparent specific gravity2.71

Water absorption(% of dry mass)

0.48

Table 6: specific gravity and water absorption results for sand


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4.3 Moisture content

Sample A Sample B

Weight of moist aggregates (g) A 301.1 340.9

Weight of oven dry aggregates(g ) B 253 285Weight of moisture(g) 48.1 55.9

% weight of moisture 19% 19.6%

Table 7: Moisture content of pumice (Tm 1 mixing)

Sample A Sample B

Weight of moist aggregates (g) A 296 307.7

Weight of oven dry aggregates(g ) B 244.6 257.3

Weight of moisture(g) 51.4 50.4

% weight of moisture 21% 19.6%


Sample A Sample B

Weight of moist aggregates (g) A 385.5 398.1

Weight of oven dry aggregates(g ) B 321.8 331.7

Weight of moisture(g) 63.7 66.4

% weight of moisture = 19.8% 20%



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Proportions of concrete constituents for trial mixes

The following proportions were arrived at from the mix design procedure as shown in tables in the

appendix section of the report.

water Cement Fine aggregates Coarse aggregates

Trial mix 1 241.732 395.833 626.4 648

Trial mix 2 241.678 351.852 615.6 648

Trial mix 3 242.069 316.67 693.9 648

Table 10: mix proportions for trial mixes (source Tables in the appendix)

4.4 Properties of trial mixes

Weight of partially compacted concrete 2.4

Weight of fully compacted concrete 2.8

Compacting factor 0.86

Table 11: compacting factor (Tm 1 - 0.48 w/c ratio)

Slump

The slump was 30mm

Age (Days)

Average

density(Kg/m 3)

Average compressivestrength (N/mm 2)

7 1863.957 8.354893

14 1865.825 9.852809

21 1859.694 10.72049

28 1846.976 12.44835Table 12: Average density and strength versus age (Tm 1)


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F igur e 7: Density vari ation with age

F igu re 8: str ength development curve: Tm 1

18301835184018451850185518601865187018751880

7 14 21 28

D e n s i t y

( k g / m

3 )

Age (days)

Tm 1: Density variation with Age

density

0

2

4

6

8

10

12

14

0 10 20 30

S t r e n g t

h ( N / m m 2

)

Age (Days )

Strength development curve :Tm1

0.48 w/c ratio


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Weight of partially compacted concrete 2.5

Weight of fully compacted concrete 2.85

Compacting factor 0.88

Table 13: Compacting factor (Tm 2 - 0.54 w/c ratio)

Slump

Trial mix 1 produced a36mm slump.

Age (Days)Averagedensity

Average compressivestrength

7 1866.3 8.088064

14 1862.023 8.554882

21 1858.076 10.28593

28 1850.032 11.88544Table 14: Average density and strength versus age (Tm 2)

F igur e 9: Density vari ation with age (Tr ial mi x 2)

1840

1845

1850

1855

1860

1865

1870

7 14 21 28

D e n s i t y

( k g / m 3

)

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Mutogoh M a - Precast Lightweight Concrete With Pumice as Aggregates