It Rained and People Sought Protection Against Rain Water Falling on the Head

8/13/2019 It Rained and People Sought Protection Against Rain Water Falling on the Head

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Widespread

Construction

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It rained and people sought protection against rain water fall ing on thehead. The concept, the art and the science of waterproofing developedfrom this desire for protection against rain water.

In the beginning, most people thought that the objective of waterproofingwas to prevent rain water from fall ing on their head. As people startedusing delicate and costly materials, and housing equipment, systems, etc.inside buildings, the ensurement of water t ightness of building typestructures became important. It wil l be seen that the prevention of theingress of water into buildings is necessary for reasons more importantthan the prevention of an inconvenience or an architectural nuisance orfor facil i tating the proper uti l ization of the space inside. In theconventional scheme of making buildings waterproof, doors have doorleaves, windows have shutters and roofs are made water-tight throughspecific waterproofing treatments or arrangements.

With time, it was recognized that it would be a good idea to make waterretaining structures also water-tight. But it took a while to recognize thatthere was more to waterproofing than to prevent rain water from falling onthe head or arresting water leakages through water re taining structures. Ittook time to recognize that the failure to waterproof structural elements, inaddition to roofs of buildings, could lead to situations.
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With delays to realize, and failures to act, buildings, bridges and otherstructures started becoming unusable because these were notwaterproofed in t ime. This happened, generally and more quickly in thecase of concrete structures, which were built during recent decades, thanin the case of structures, which were built before 1965 or so.

The lack of durabil ity of concrete structures has been a worldwidephenomenon. In a paper in 1991, Papadakis, Vayenas and Fardis1 stated

: The last two decades have seen a disconcerting increase in examplesof the unsatisfactory durabil ity of concrete structures, specially reinforcedconcrete ones.

The problem of unsatisfactory durabil ity is more acute in India where ithas reached an alarming state. The alarming situation in India, caused bythe early distress in reinforced concrete structures, is reflected inTechnical Circular 1/99 of the Central Public Works Department,Government of India, wherein it has been stated that while works as oldas 50 years provide adequate service, the recent constructions areshowing signs of distress within a couple of years of their completion.

In most cases of concrete structures, the structural distress in the form ofcracking in the concrete elements or collapse of the structure is anexternal manifestation of corrosion in the ferrous elements inside.

There are reasons behind the early or accelerated rate of distress, inmodern day concrete structures. The rate, at which modern day structures

started reaching states of early distress, accelerated with the use of HighStrength Deformed (HSD) reinforcing bars (rebars) in the construction ofreinforced concrete structures.

Among other factors, contribut ing to the decaying process, was thelowering of the period of wet curing of concrete from 28 days to 37 daysor none. As there is a move towards a greater use of Portland PozzolanaCement (PPC) in l ieu of Ordinary Portland Cement (OPC) in concrete, thischange in the type of cement wil l have its effect on the durabil ity ofconcrete structures, unless special provisions wil l have been made.

Address the problem of early dist ress in concrete structures and solutionsthereto. As surface protection of structures by waterproofing is proposedas a viable solution to the problem of early distress in concrete structures,it is explained why waterproof structures are durable structures.

Durable and effective waterproofing systems are described later in thispaper.


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Early Distress and Causes

The alarming state of affairs with constructed facil i t ies of recent decadeshas put civil ization in peril. When humanity is in peril, God comes to showthe way. In such circumstances ten years ago in 1996, Lord Ganesh,showed the way when the stone statues started drinking milk on offeringby worshippers. Ganesh started drinking water. It was Lord Ganesh ofrock or stone who drank milk and water. Ganesh, cast in metal, wouldneither drink milk nor water.

Lord Ganesh drank milk and water to teach architects and engineers alesson. The lesson was : concrete, an artificial stone, would absorb waterand other l iquids. The rate and quantity of water would depend upon thepermeabil ity and porosity of concrete.

This absorption of water by concrete, though undesirable, is inevitable inthe case of concrete structures without surface protection. This water,that enters inside the structure, creates a moist environment. When airfrom the environment, containing oxygen, enters into the structure and

reaches rebars or prestressing elements of steel, oxidation, the mostcommon of the different processes of corrosion of steel, takes place, ifthe Fe2O3protective layer of passivation on the surface of rebars andprestressing elements wil l have been destroyed due to carbonation (bycarbon dioxide from air) or chloride intrusion or due to pozzolanic reactionfrom the use of PPC or High-Volume Fly Ash (HVFA) cement3-5 inconcrete. Though the process of corrosion requires oxygen and a moistenvironment, carbon dioxide, chlorides, acids and sulphates can further

add to the destabil izing processes. It needs to be noted that, l ike oxygen,even acids and chlorides, the well-known agents of corrosion, wil l beineffective in causing or augmenting rebar corrosion unless there wil l be amoist environment. Similarly, other harmful reactions in concrete, viz.,alkali-sil ica reaction, sulphate attack, etc. wil l fail to take place unlessthere wil l be moisture. On the other side of the picture, water alone wil lnot cause any problem unless there wil l be oxygen. A case in point is aship under water on the sea bed. In the absence of sufficient oxygen, therate of corrosion is very slow even when there are chlorides in the water.Thus, though it is essential, for corrosion to take place, that the concreteenvironment, surrounding rebars and prestressing elements, be moist,

submersion in water is l ikely to inhibit the process of corrosion.

The above suggests that all structures above ground and those portions ofstructures below ground, which are exposed to the atmosphere (e.g.basements, tunnels, underground water reservoirs, machine pits, l i f t pits,and so on), wil l be vulnerable, if left unprotected, whereas rebar corrosionmay not be a problem in the case of foundations. In simpler terms, allstructures, exposed to air, wil l be vulnerable. Of these, concrete


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structures (primarily reinforced concrete structures), constructed duringrecent decades, have been characterized by early decay and distress.There must be reasons for this development, that goes beyond anypossible shortfall in the quality of construction.

It has been written extensively on the basic causes of the problem of earlydistress in concrete structures, constructed during recent decades, andsolutions thereto. Of particular interest to the reader wil l be that the use

of high strength rebars with surface deformations has been primarilyresponsible for the early decay in concrete structures of recentconstructions. The problem has been more acute in India where the HSDbars were of the cold twisted deformed (CTD) type, commonly known astor bar.

CTD bars are particularly susceptible to early corrosion as high post -yieldstresses are locked in such rebars from the time of manufacturing,inducing speedy corrosion in keeping with the phenomenon of stresscorrosion at high stress levels, even before concrete is cast .

Early corrosion sets in CTD bars also because the protective surfacelayer of Fe2O3or Fe3O4 is destroyed during cold twisting of the rebar as apart of the manufacturing process.

Other factors, which can make concrete structures predisposed to earlydecay and distress, is the lowering of the duration of moist curing ofconcrete from 28 days of earlier years to 7 days or less and the shift

towards the use of f ly ash based PPC from OPC that used to be commonlyused in construction in earlier days.

The PPC concrete lacks the capacity of OPC (wit h about a monthscuring) to produce 15 to 25% (by mass of cement paste) calciumhydroxide Ca(OH)2 and with it to maintain a pore water alkalinity of 12.4and above for prolonged periods of t ime, thereby protecting rebars andprestressing elements through the formation and preservation of theFe2O3 layer of passivation. Furthermore, unlike OPC concrete, PPCconcrete lacks the properties of self- healing of pores and cracks.

In summary, in addition to the absorption of water or moisture, porousconcrete permits the diffusion of carbon dioxide and oxygen, all of whichare present in the atmosphere. Because of the changes in the propertiesof materials of construction and because of the shortening in the durationof curing, todays concrete structures, compared to structures of earlierdecades, are affected more adversely by the atmospheric and otherexternal agents of corrosion, viz., water or moisture, carbon dioxide,oxygen, etc.


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The Solution

An obvious solution to the problem of early decay and distress in concretestructures would be to use the appropriate rebar and cement and to curethe concrete over prolonged periods of t ime. That would mean the use ofplain round bars of mild steel and OPC with curing for about a month. Butsince the construction may not be with plain round bars of mild steel andOPC, coupled with a months curing, the next best option would be toprotect the structures, both new and existing. This protection of concrete

structures wil l have to be, as a minimum against water, oxygen andcarbon dioxide. It can be said, as an analogy, that concrete structures,similar to steel structures, can benefit from surface protection. Just as inthe case of steel structures, the failure to provide surface protection toconcrete structures wil l mean loss of durabil ity and high l ife-cycle cost ofthe unprotected structure.

Effective and durable waterproofing treatments wil l make structuresdurable. Such treatments wil l also prevent any architectural nuisance ofdamp ceil ings and walls.

This concept of providing surface treatment to concrete structures for thepurposes of making such structures waterproof as well as durable hasbeen stressed . The concept was adopted by Central Public WorksDepartment of the Government of India in 1999 and subsequently in thecode IS 456:200024. It is mentioned in clause 8.1.1. of the code that One

of the main characteristics influencing the durabil ity of concrete is itspermeabil ity to the ingress of water, oxygen, carbon dioxide, chloride,sulphate and other potentially deleterious substances. It has furtherstated in clause 8.2.1 that The life of the structure can be lengthened byproviding extra cover to steel, by chamfering the corners or by usingcircular cross-sections or by using surface coatings which prevent orreduce the ingress of water, carbon dioxide or aggressive chemicals.

It has been explained in details in Ref. 8 that, of the four alternatives,recommended in IS 456:200024, the provision of surface protectionsystems is the only logical and practical way of ensuring long life for

concrete structures.

Even six years after the publication of the code24, architects andengineers appear to have overlooked the mandatory provisions of thecode as they have failed to implement the provisions in clause 8 of thecode.

The failure to provide the surface protection wil l not only condemn the


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unprotected structures to early decay and distress, the constructedstructures wil l also fail to meet the requirements of the code IS456:200024. The surface protection system is provided as a waterproofingsystem on the surface of structures, and not on reinforcing bars25.Though the code has recommended the provision of surface coatings, allconcrete surfaces are not necessarily amenable to the application ofcoating systems. Thus, this writer believes that since the objective is toprevent the ingress of harmful elements, coatings or other waterproofing

systems should serve the purpose of lengthening the l ife of concretestructures.

Effective Waterproofing Treatments

It has already been explained that waterproofing systems or treatments,provided on the surface of structures, can do much more than preventingan inconvenience or architectural nuisance. Such treatments, if effective,

can make structures durable. That, however, requires that the treatmentsare not only effective in preventing the ingress of water into the structure,but that the treatments are also durable. Many different materials andsystems have been tried for the waterproofing of structures. Fieldexperience shows that most of the treatments fail to achieve the desiredresults even in the short term.

The reasons are many, and these include:A) Wrong conceptB) Lack of a wil l to do the work wellC) Failure to adapt an appropriate technologyD) Failure to improvise

Wrong ConceptFailure of waterproofing treatments due to the application of wrongconcepts are all around. A few examples wil l suffice. Waterproofingtreatments are provided on compressible treatments for thermalinsulation. The excessive compressibil i ty of the material for thermalinsulation leads to large movements in the waterproofing treatments andtheir consequent failures.

Waterproofing treatments are provided on a course of Plain CementConcrete (PCC), which fails for the lack of reinforcing elements and a lackof adequate bond at the interface between the substrate and the PCC. Asmall quantity (0.5% to 2.0%) of a plasticizer or a superplasticiser isadmixed with concrete in the name of waterproofing, simply because itmeets the requirement of the code IS 2645:2003, which, with its nameIntegral Waterproofing Compounds for Cement Mortar and Concrete


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Specification27, has a misleading tit le, ignoring the fact that the text ofthe code reads : The permeabil ity to water of the standard cylindricalspecimen prepared with the recommended proportions of waterproofingcompound shall be less than half of the permeabil ity of similar specimenprepared without the addition of the compound when tested in accordancewith the method given , thereby qualifying chemicals, withoutwaterproofing properties, as chemicals suitable for successfulwaterproofing treatments.

Lack of Will to Do The Work Well

It is believed that the manufacturer of chemicals wil l be particularly keento see that the waterproofing system, based on his chemicals, wil l performwell. In the Indian environment, many manufacturers are keen to sell thechemicals to anyone for any purposes and the work of waterproofing isexecuted by contractors as authorized/ approved applicators.

In this system of work by applicators, the quality of work generally suffersas:

A) The manufacturer of chemicals is not aware of the f ield conditions ofindividual sites and the developer of the chemicals and systems,generally chemists have limited knowledge about construction.

B) The applicator is not aware of the l imitations of the chemicals.C) The applicator does not use the right quality of chemicals as he

does not have the reputation of chemicals/systems to uphold.

Failure to Adopt Appropriate Technology

Waterproofing is an activity in the domain of civil engineering, and itinvolves structures. It can thus be very helpful to have a good knowledgeof civil engineering and structures. Thus, when chemists and materialscientists develop chemicals and systems of waterproofing , they arelikely to overlook fine points in civil-structural construction engineering,and the technology for waterproofing may not be appropriate. This isparticularly so as most often technologies are first developed, andavenues are sought to apply the technology. The best results are possiblewhen technologies are developed to solve problems, and not the other

way round.

Failure to Improvise

Every work site has a character of its own, requiring improvisation.Though a particular waterproofing chemical and a particular system willbe employed as the basic treatment, local conditions frequently require fora successful waterproofing treatment that certain modifications are made


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to the implementation procedure or that a different chemical and adifferent system be employed locally as a stand-alone or as an additionaltreatment. A failure to make necessary improvisation may lead to a f ailureof the waterproofing treatment.

Widespread Construction

WIDESPREAD CONSTRUCTION for waterproofing is free from the

shortcomings, commonly found in other technologies. The waterproofingsystems for waterproofing under W idespread Construction were developedto solve specific problems after others had failed to solve such problemsby the application of different known systems of waterproofing.

Terrace-waterproofing is possible with varying permutations and

combinations within a wide product range, to suit the 'tailor-made'

requirements of the clients.

1. Whilst any water proofing system is decided, it is imperative to

have a basic substrate, which is structurally sound. If the base on

which a waterproofing application is done, happens to be weak, then

the system chosen wil l also weaken. In order to have the base

concrete strong enough, the concrete should be admixed with an

integral waterproofing compound which would give a homogeneous,

workable mix at lower water/cement ratio and reduce the

permeabil ity. It should be ensured that the terrace is given a proper

slope. Any standing water shall not be permitted. Many

waterproofing systems have been found to fail because of standing

water remaining on the surface consistently for longer duration.

2. The concrete, after casting, should be cured by ponding orsprinkling water or with a suitable curing compound spread over the

entire surface. Init ial curing is crit ical and should start immediately

after the init ial setting of the concrete, say after 4 to 6 hours of

placing concrete. Lack of init ial curing is the main cause of drying

shrinkage cracks.


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3. For construction of the parapet wall, a suitable mortar plasticizer

should be used with the bricklaying and plastering mortar to improve

the quality of the mortar.

4. Before starting any treatment for waterproofing of the slab, all the

visible cracks, undulations, joints etc. should be taken care of with a

suitable waterproof repair mortar.

5. On the cured and repaired concrete surface, there are 3

alternatives, which can be considered for waterproofing.

Concrete leaks due to the following reasons:

1. Thermal Variation

2. Long Term Drying Shrinkage

3. Crack In Transition Zone

4. Structural Stresses

5. Creep Deformation

6. Thermal Incompatibil i ty between Paste & Aggregate

7. Rusting Of Steel

8. Sulphate Action, Moisture Movement Due To VolumeChange

ANATOMY OF WATER PROOFING

Significant factors contributing towards the dampness coming from

the terraces into the soffit of the ceil ings are:

The entry of water through cracks in external plaster


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Failure of pointing

Hollow left due to insufficient grouting of stone masonry

Capillary action

Incorporation of incompatible components l ike RCC lintel

bands in stone/brick masonry walls

f lashing of water on external surfaces

inadequate and imperfect expansion structural

deformations etc.

NEED OF WATER PROOFING PRODUCTS

Ideally concrete, the most widely and regularly used construction

material is supposed to be water t ight with co efficient of hydraulic

permeabil ity between 10-8 to 10-10 m/sec. a well made concrete

with proper mix design and with proper pouring and curing practices

is regarded as a very low porous material. However it is seen in

practice that concrete loses its permeabil ity due to the following

reasons:

1. Improper gradation of materials

2. Excessive water cement ratio

3. Less compaction

4. Awkward architectural sect ion

5. Improper shuttering


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6. Cold joints shuttering either in mass concreting or in tall

vertical structures

7. Use of bad quality construction materials such as corrosive

reinforcement or reactive aggregates

8. Lack of curing : t imely curing specially in high cement content

concrete mix or where high grade cement is used in plastering

9. Damage to structures due to earthquake effects

10. Failure of plumbing

Some of the essential precautions to be taken at the time of

construction are as follows:-

1. Every building plan, whether for new building OR foraddition/alteration to new building, must give details of terracingto be provided , water proofing system for roof with details of

joint wi th parapet wa ll, sunken f loor and down water pipes inscale not smaller than 1:20.

2. Specifications laid down by the manufacturers of the waterproofing products should be followed scrupulously to ensure thatno air bubbles are left between the under lying surface and thewater proofing layer. Adequate overlaps should be provided forthe water proofing layers, including cover up to the parapet wall.There are a large number of relevant Indian Standards and Codeof practice available.

3. Drainage slope of the roof is one of the most important factors.For the guidance of the field Staff, each building plan must alsoincorporate a roof plan, showing the position of drainage Pipesand direction and extent of slope on the roof. Drainage slopeshould not be flatter than 1 in 80 and should preferably be 1 in40. There should be no undulations in the roof surface, which


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may result in accumulation of rain water. At the time ofconstruction, the roof levels should be personally recorded bythe Inspector of Works and 100% check exercised by the

Assistant Engineer. Extra care is necessary for construction ofgolas, coping and joints.

4. At the extension joints in buildings , wa ter proofing has to bestrengthened by inserting a PVC Or a copper plate to preventwater from seeping. These joints should also be plugged by agood sealant. Polysulphide based flexible sealants have goodadhesion to concrete surfaces and can be compressed orstretched upto 50% of the width of the joints and are goodmaterial for sealing of expansion joints. Depth of the expansion

joints above the copper/PVC plate should norma lly be kept half ofthe joint width and should not exceed 20 mm.

5. Special precautions should be taken for sealing of area aroundthe water spouts to make them water proof.

6. Any type of impermeable layer/coating should never be appliedon both faces of the wall as the wall must be allowed tobreathe. A non-permeable finish or waterproof f inish should notbe applied on a wet wall, as it takes a long time to lose waterused during construction. The interior of a new building shouldpreferably be provided with l ime based color wash.

7.

Quality of casting of concrete slab and quality of terracing hasto be good and strictly as per specifications. Dense and lowpermeabil ity of concrete also ensures relief-from dampness andcomes by adequate cement content and low water cement ratioin concrete apart from required level of compaction and adequatecuring.


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8. Area surrounding plinth of the building should be f il led withgood earth and rammed with slope away from the building,preferably with plinth protection apron.

9. Proper drip course should invariably be provided on parapet wallcopings, sun-shades, chajjas etc.

10. Sunken floors are a constant source, of leakage and dampness.

These floors are provided for accommodating the toilet seats. Sunkenfloors must invariably be coated with suitable epoxy or polyurethanecompound or polymer cementit ious waterproofing compound. Thesecoatings should be given over the slabs as well as on the walls up to40 cms above the floor level.

11. Proper distribution, design and installation of joints in the buildinge.g. expansion/contraction and construction joints and maintenancethereof can go a long way towards improving the water proofing of thebuilding, since any crack may give rise to ingress of water.

12. Adequacy of drainage must be ensured. As a general guide l inefor every 40 M2 of roof area, one 100 mm diameter rain water pipemust be provided. Drainage wil l also depend upon the intensity of rainfall in the area.

Definition of damp proofing

One of the essential requirements of a building is that it should be dry.Dampness in building may occur due to bad design,faulty construction and use of poor quality of materials. Dampness notonly affects the l ife of building adversely, but also createsunhygienic condition for the occupants. The treatment given to preventleakage of water from roof is generally termed as waterp roofing, where asthe treatment given to keep the walls, f loors and basement dry is termedas damp proofing.

A damp proof course (DPC) is a physical barrier inserted into the fabric

of a building to stop water passing from one place to another. This can be

on a horizontal plane, stopping water rising up from the ground by being

sucked up by the dry masonry above, or vertically to stop water passing

from the outside of a building, though the masonry, to the inside. DPC's

have taken many forms through the ages and one of the earliest forms


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was to use a layer of slate in the construction. Slate is sti l l used but the

less expensive plastic version (below right) is now more widely used.

HORIZONTAL DPC

Causes of Dampness:

The dampness in building is a universal problem and the various

causes, which are responsible for the entry of dampness in a structure,

are as follow.

1) Rising of moisture from ground

The ground on which the building is construction may be made of soil,which easily allows the water to pass. Usually the building material used

for the foundations, absorb moisture by capil lary action. Thus the

dampness finds its way to the floor through the sub structure.

Rising of ground water level
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2) Action of rain

If the faces of wall, exposed to heavy showers of rain, are not suitable is

protected, the become sources of dampness in the structure. Similarly the

leaking root also permits the rainwater to enter a structure.

3) Exposed of top wall

The parapet wall and compound wall also should be providing with a

damp proof course on the exposed tops. Otherwise the dampness entering

thought these exposed tops of such walls may lead to serious result.

4) Condensation

The process of condensation takes place when warm humid air is

cooled. This is due to the fact that cool air can contain less invisible water

vapour than warm air. The moisture deposits on the walls, f loors and

ceil ing. This is the main causes in badly designed kitchen.

There are various causes of dampness as mention below

1. If the site located on a site, which cannot be easily drained off, the

dampness wil l be interring in structure.

2. The orientation of a building is also an important factor, the wall

obtaining less sunrise and heavy shower of rain are l iable to become

damp.

3. The new constructed walls remains damp for short duration.

4. Very flat slope of a roof may also lead the penetration of rain waterwhich is temporary store on roof.

5. The dampness also caused due t o bad workmanship in construction

Such as defective joints in the roofs, improper connection of wall.

Effect of dampness

The building material such as bricks, t imbers, concrete etc, has moisture

content, which is not harmful under normal condition. The rise in moisture

content of these materials beyond the certain level from where it come

visible or when it deterioration leads to the real dampness. If absolute

terms, the moisture content of different materials may be same, but theacceptable l imit differs from material to material. For instance, the

presence of 10 per cent by weight in t imber is not harmful. But the same

level could saturate a brick or cause deterioration of plaster.


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The structure is badly aff ected by dampness. The prominent effect of

dampness is as follow.

1. A damp building gives rise to breeding of mosquitoes and creates

unhealthy condition for those who occupy it.

2. The metals used in the construction of material are corroded.

3. The decay of t imber takes place rapidly due to dry-rot in a damp

atmosphere.

4. The unsightly patches are formed on the wall surface and ceil ing.

5. The materials used as floor covering are serious damaged.

6. It results in softening and crumbing of the plaster.

7. The materials used for wall decoration are damaged and it leads to

diff icult and costly repairs.

8. The flooring get loosened because of reduction in the adhesion when

moisture enters through the floor.

Methods of damp proofing

Following methods are used for prevent the defect of dampnessin structure

1. Membrane damp-proofing

2. Integral damp-proofing

3. Surface treatment

4. Guniting

5. Cavity wall construction

1. Membrane damp-proofing

This consists in proving layer or membrane of water repellent materialbetween the source of dampness and the part of the structure adjacent to

it. This type of layer is commonly known as damp-proof course and it may

comprise of material l ike bituminous felts, mastic asphalt, si l icon, epoxy,

polymers, plastic or polythene sheets, cement concrete etc depending

upon the source of dampness, d.p.c may be provided horizontally or


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vertically in f loor, walls etc. provision of d.p.c in basement is normally

term as tanking.

Membrane damp proofing

General Principles to be observed while laying d.p.c are as under

1. The d.p.c should cover full thickness of wall excluding rendering.

2. The mortar bed upon which the d.p.c is to be laid should be made

leveled, even and free projections. Uneven base is l ikely to cause damage

to d.p.c.

3. When a horizontal d.p.c is to be continued to a vertical face, a cementconcrete fi l let 75 mm in radius should be provided at the junction, prior to

the treatment.

4. Each d.p.c should be placed in correct relation to other d.p.c, so as to

ensure a complete and continuous barrier to the passage of water from

floors, walls or roofs.

2. Integral damp proofing

This consists in adding certain water-proofing compound with the

concrete mix to increase its impermeabil ity. Such compounds are

available in market in powdered as well as l iquid form. The compoundsmade from clay, sand or l ime help to fi l l the voids in concrete and make it

water proof.

Another form of compound like alkaline sil icate, aluminum sulphates,

calcium chloride etc. react chemically when mixed in concrete to produce

water proof concrete.
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Pudlo, permo, impermo etc are some of the many commercially made

preparations of water-proofing compound commonly used. The quantity of

water proofing compound to be added to cement depends upon the

manufacture recommendations. In general, one kg of water proofing

compound is added with one bag of cement to render the mortar or

concrete water-proofing.

3. Surface treatment

The moisture finds its way through the pores of material used in f inishing.

In order to check the entry of the moisture into the pores, they must be

fi l led up. Surface treatment consists in f i l l ing up the pores of the surface

subjected to dampness. The use of water repellent metall ic soaps such as

calcium and aluminium oleates and stearates is much effective

in protecting the building against the ravage of heavy rain. Bituminous

solution, cement coating, transparent coatings, paints and varnishes fall

under this category. In addition to other surface treatment given to walls,

the one commonly used in l ime cement plaster. The walls plastered with

cement, l ime and sand mixed in proportions of 1:1:6 is found to serve the

purpose of preventing dampness in wall due to rain effectively.

Surface treatment

5. Guniting

This consists in deposing an impervious layer of rich cement mortar over

the surface to be water proofed. The operation is carried out by use of a

machine known as cement gun. The assembly broadly consists of amachine having arrangement for forcing the mixture under pressure

through a 50 mm dia flexible hosepipe. The hosepipe has nozzle at its

free end to which water is supplied under pressure through a separate

connection.

The surface to be treated is f irst thoroughly cleaned of dirt, dust,

grease or loose particles and wetted properly. Cement and sand usually

taken in proportion of 1:3 to 1:4 are then fed into the machine. This
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mixture finally shot on the prepared surface under a pressure of 2 to 3

kg/cm2 by holding the nozzle of the cement gun at a distance of 75 to 90

cm from the working face. The quantity of water in the mix can be

controlled by means of regulating value provided in the water supply hose

attachment. Since the material is applied under pressure it ensures dense

compaction and better adhesion of the rich cement mortar and hence the

treated surface becomes waterproof.

Cavity wall construction

This consists in shielding the main wall of the building by an outer skin

wall leaving a cavity in between the t wo. The cavity prevents the moisture

from traveling from outer to the inner wall.

Understanding Water and Deleterious Substance TransportMechanisms in Concrete

Abstract: Moisture migration into concrete is the leading cause of

concrete degradation worldwide. There are two primary watertransport mechanisms in concrete. Considering waters powerful

forces and then designing concrete structures to adequately resist the

known effects of these two common water transport mechanisms is

paramount to achieving durable structures. Designers, contractors,

and owners need to thoroughly understand the differences in the

mechanisms to ensure the structures they are building provide

adequate problem-free service life.

PART 1 GENERAL SUMMARYA. Section Includes: Furnishing of all labour, materials, services andequipment necessary for the supply and installation of waterproofingsystems (as described in the BOQ) to concrete substrates, above-grade,on either dry or wet side of substrates, as indicated on drawing and asspecified herein.

A p p l i c a b l e S t a n d a r d s :
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The following standards are referenced herein.1. American Society for Testing Materials (ASTM)2. Army Corps of Engineers (CRD)3. NSF International (NSF)

4. Bureau of Indian Standard (IS) 2720

SYSTEM DESCRIPTIONCatalytic In -d e p t h C r y s t a l l in e W a t e r p r o o f i n g : Blend of portlandcement, f ine treated sil ica sand and active proprietary chemicals. Whenmixed with water (or a flexibil izer) and applied as a coating layer, theactive chemicals in the coating layer penetrate the concrete substrate andcause a catalytic reaction which generates a non-soluble crystall ineformation of dendrit ic f ibers deep within the pores and capil lary tracts ofconcrete. This process causes concrete to become permanently sealed

against the penetration of l iquids from any direction. Two productversions of Catalytic In -depth Crystall ine Waterproofing are available,i.e. cementit ious and Flexible-Matrix.The Flexible-Matrix version is preferred over the cementit ious version,due to its elongation characteristics and additional virtue of forming amembranous barrier around the concrete to which it is applied.

A c r y l i c P o l ym e r - M o d i f i e d F l ex i b l e C em e n t i t i o u s M emb r a n e / Co a t i n g :having UV resistance, underground ground-chemical resistance, high

melting points, f lexible and elastic with high adhesive strength. Themembrane shall be reinforced with a layer of non-woven polyester fabricof minimum 30 g/sqm. The Acrylic Polymer-Modified Flexible Cementit iousMembrane / Coating shall be protected with a subsequent protectivecementit ious layer of concrete screed / plaster in thickness as specified inthe BOQ. The total coating thickness shall be as specified by themanufacturers technical l i terature but not less that 1.5 mm and shall beapplied in 2 - 3 coats.

SUBMITTALSSubmit l isted submittals in accordance with conditions of the Contract

and with Division

Product Data : Submit product data, including manufacturersspecifications, installationinstructions, and general recommendations for waterproofing applications.

Also includemanufacturers certif ication or other data substantiating that productscomply with requirements


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The guarantee wil l cover the surfaces treated and wil l blind the agency torepair, at his expense, any and all leaks through the treated surfaceswhich are not due to structural weaknesses or other causes beyondapplicators control such as fire, earthquake, torna do and hurricane. Theguarantee shall read as follows.

Civil Materials related with waterproofing : Cement, screened riversand, brick-bats, aggregates, integral waterproofing compounds, etc.

required for screeds, protective toppings and plasters shall conform to thepertaining IS standards (IS 269, IS 8112, IS 13286, IS 383, IS 2645, IS12118 and IS 3495). The Consultants / PM shall demand the conformanceof these materials from the Specialized Executing Waterproofing Agencies/ civil contractor from time to time and they shall have to produce testreports / documents to prove the conformance of these materials withtheir applicable standards, without any argument.

MIXES

General : Mix waterproofing material as specified by the Manufacturer.Follow exact instructions as mentioned in the respective technicall iterature. Mix waterproofing material in quantit ies that can be appliedwithin 20 to 30 minutes from time of mixing.

Application :

Liquid applied coatings / membranes : by brush, spray, squeegee ortrowel

Pre-Fabricated Membranes : by priming and torching

EXECUTION EXAMINATION

Site Visit : Prior to waterproofing installation, arrange visit to project sitewith waterproofing manufacturers representative. Representative shallinspect and certify that concrete surfaces are in acceptable condition toreceive waterproofing treatment.

Verification of Substrates : Verify that concrete surfaces are sound andclean, and that form release agents and materials used to cure theconcrete are compatible with waterproofing treatment.


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Examination for Defects : Examine surfaces to be waterproofed for formtie holes and structural defects such as honeycombing, rock pockets,faulty construction joints and cracks. Such defects to be repaired inaccordance to manufacturers product data .

PREPARATION

Concrete Finish : Concrete surfaces to receive waterproofing treatment

shall be free from scale, excess form oil, laitance, curing compounds andforeign matter. Horizontal surfaces shall have a rough wood float, smoothor broom finish, as required by the waterproofing material manufacturer.

SSD stands for saturated surface-dry and it describes a condition that aconcrete surface must be brought to when a cement product is to beapplied to it. The surface is SSD when the concrete is saturated withwater to a depth of several mil l imeters, but the other surface is devoid offree water, as if i t had been dried with a tower.

This surface condition is very important when applying cement products toexisting concrete because the saturation prevents rapid drying andweakening of the product and its bond to the surface. Just as important,removal of free water from the surface prevents dilution and weakening ofthe product in exactly the location where strength is most vital: at thebond interface, Make sure your concrete is SSD before applying

Surface Preparation : Smooth surfaces (e.g. where steel forms are used)or surfaces covered with excess form oil or other contaminants shall bewashed, l ightly sandblasted, water blasted, or acid etched with muriaticacid (as necessary) to provide a clean absorbent surface. Surfaces to beacid-etched shall be saturated with water prior to application of acid.

Repair of Defects: Surface defects shall be repaired in accordance withmanufacturersinstructions as follows:

1. Form Tie Holes, Construction Joints, cracks: Chip our defective areasin a U shaped slot 25mm wide and a minimum o f 25 mm deep. Clean slotof debris and dust. Soak area with water and remove excess surfacewater. Apply a polymer modified cementit ious bonding coat of approvedmaterial to the slot. Then fi l l cavity with a non-shrink, waterproof,cementit ious grout / mortar, while the bonding coat is tacky. Compresstightly into cavity using pneumatic packer or block and hammer. Where


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the concrete is defective, do injection grouting with high pressure (140psi) grouting machine using cement admixed with non-shrink groutingadmixture.

2. Rock Pockets, Honeycombing or Other Defective Concrete: Rout outdefective areas to sound concrete. Remove loose materials and saturatewith water. Remove excess surface water and apply a polymer modifiedcementit ious bonding coat of approved material to the area. While the

bonding coat is sti l l tacky, f i l l cavity to surface level with non-shrink grout.Where the concrete is defective, do injection grouting with high pressure(140 psi) grouting machine using cement admixed with non-shrinkgrouting admixture.APPLICATIONConstruction Joints : Apply cementit ious bonding material in slurry form

to joint surfaces between concrete pours, just prior to pouring freshconcrete. Moisten surfaces prior to the bonding coat application.

Where joint surfaces are not accessible prior to pouring new concrete,consult manufacturer for application procedure.

Coves (vata): Make a minimum 4 inch (diagonal) cove / vata at all 900interfaces in concrete surfaces where waterproofing is carried out, withoutfail.

Surface Application : After repairs, surface preparation, treatment ofconstruction joints, cracks, honeycombs, t ie-holes, etc., have beencompleted in accordance with manufacturers product data and asspecified herein, apply / provide the waterproofing material as specified inthe manufacturers technical and application data sheet to concretesurfaces. Application rates, thicknesses and locations shall be asindicated in the drawing. When brushing, work slurry well into surface ofthe concrete, f i l l ing surface pores and hairl ine cracks. When spraying,hold nozzle close enough to ensure that slurry is forced into pores andhairl ine cracks. When torching, uniformly burn the surface whenoverlapping, to ensure that the membrane adheres uniforml y.

Sandwich (Topping) Application : When treated structural slabs are toreceive a concrete or other topping, place the topping only after the init ialcuring period of the material is being used, is completed. Lightly pre-water when rapid drying conditions exist.


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CURING

Cementitious materials : Begin curing as soon as the appliedwaterproofing material has hardened sufficiently so as not to be damagedby a fine spray. Cure the treatment with water as per the manufacturersinstructions. In warm climates, more-than-normal curing duration may benecessary to prevent excessive drying of coating.

Liquid applied membranes / Pre-fabricated membranes : natural aircuring for duration as described in the manufacturers technical datasheet.

Ai r Circulation : Do not lay plastic sheeting directly on the waterproofingcoating as air contact is required for proper curing. If poor circulationexists in treated areas, it may be necessary to provide fans or blown air toaid in curing of waterproofing treatment.

Water-holding Structures: For concrete water-holding structures such asswimming pools, reservoirs, water treatment tanks and wet wells, cure thewaterproofing system for a minimum of three days and then allow thewaterproofing system to set for 7 days before fi l l ing structure with l iquid.

For structures holding hot or corrosive l iquids, cure waterproofingtreatment for three days and allow setting for 15 days before fi l l ing.

Protection : During the curing period, protect the treated surfaces fromdamage by wind, sun, rain and temperatures below 20 C. If plasticsheeting is used for protection, it must be raised off the waterproofingcoating to allow sufficient air circulation.

INTERFACE WITH OTHER MATERIALS

Backfilling : Do not backfi l l for 36 hours after application. If backfi l l takesplace within seven days after application, then backfi l l material shall bemoist so as not to draw moisture from waterproof coating.

Paint , Epoxy or Similar Coatings : Do not apply paint or other coatingsuntil waterproofing treatment has cured and set for a minimum of 21 days.Before applying or coating, neutralize treated surface by dampening withwater and then washing waterproofed surface with 15% (HCL) muriatic


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acid, diluted in a ratio of one part acid to four parts water by volume.Flush acid off treated concrete surfaces.

Grout , Cement Coat , Plasteror Stucco : Because the waterproof coatingforms a relatively smooth surface and the resulting waterproof coatingreduces the suction characteristics of the concrete, it may be necessaryto use a suitable bonding agent for proper bonding of cementit ioussystems (IPS, screeds, plaster, etc.), if they a re applied

Responsibility to Ensure Compatibility : The respective manufacturersmust confirm in writ ing regarding compatibil i ty of their waterproofingtreatments with other coatings, plaster, stuccos, t i les or other surface-applied materials. It shall be the responsibil i ty of the manufacturer /installer of the waterproofing material to take whatever measures arenecessary, including testing, to ensure acceptance by or adhesion to theirwaterproofing system.

FIELD QUALITY CONTROL

Observation : Do not conceal installed waterproofing system before it hasbeen observed by Architect/Engineer, waterproofing manufacturersrepresentative and other designated entit ies.

Flood Testing :

1. Perform flood test on completed waterproofing installation for aminimum of 72 hours before placement of other construction.

2. Plug or dam drains and fi l l area with water to a depth of at least 100mm.

3. If leaks are discovered, make repairs and repeat tests unti l no leaksare observed.

CLEANING AND PROTECTION

Cleaning : Clean spil lage and soil ing from adjacent surfaces usingapproximate cleaning agents and p rocedures.


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Protection : Take measures to protect completed waterproofing systemfrom damage immediately after application. Do not permit traff ic onunprotected coating or membrane.

Documents

It Rained and People Sought Protection Against Rain Water Falling on the Head