Concrete Chem testing-TQP pres.ppt Methylene blue test passes you can safely use your sand with moderate decrease in sand equivalent values Raw Materials- Fine Aggregates Organic impurities

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Concrete Chemical Testing Requirements and Testing…Requirements and

Implications

Prepared by: Mohammad Dokmak-TQPPresented at the UNESCO Palace-BeirutOct 16, 2012

Although physical testing of concrete is vital (mechanical, NDT, etc), this presentation will focus on chemical testing only at the different stages of concretingg gIt also focuses on the need and significance of every requested test.It does not provide solutions for repair.

Concreting Stages

Concrete shall be chemically monitored and controlled at each stage from production to post hardening.

Stage 1: Raw materialsStage 2: Fresh concreteStage 3: Hardened concrete Stage 4: Old concrete or Concrete under specific circumstances

Every stage necessitates certain chemical tests to be conducted. Some other tests are only required upon doubt.

Concreting Stages

Project specifications are almost crowded with chemical tests that to be conducted.As an engineer, you might not necessarily be knowledgeable of how to conduct abe knowledgeable of how to conduct a test; however, you should be aware of the reason behind requesting such test, able to analyze the obtained result, and almost able to recommend the proper solution.

In the subsequent slides, We will be focusing “ h t d h ” t t t t h t fon “what and why” to test at each stage of

concrete.

What to test and Why?Raw Materials

Concrete raw materials comprise the following:Cementetious materials (cement, fly ash, silica fume, etc)WaterAggregate (CA, MA, CS, and NS)and Admixtures (retarding, accelerating, air entraining, etc)

To ensure the quality of your concrete you should select the best concrete constituents, free of deicing chemicals , with minimum organic matters, non reactive with alkali, etc.

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Raw Materials- Cementetious

Test Method

Chemical analysis ASTM C114, or BS EN 196-2

Chromium VI content EN 196 10Chromium VI content EN 196-10Shrinkage tests (in water, in sulfate, etc)

ASTM C452,C1012, C596, or C1038


Need for cement Chemical AnalysisCement is almost reliable (consistent); however it has to be checked upon doubt of its properties, when bizarre strength results occurs under controlled conditions, to confirm type, etc.Indicators of alteration in cement composition are such that:

Early strength results at 7 days due to increase in Tricalcium Silicate (C S)%(C3S)%.Dicalcium Silicate (C2S) hardens slowly and contributes largely to strength increases at ages beyond 7 days.Tricalcium Aluminate (C3A) liberates a large amount of heat during the first few days of hardening and, together with C3S and C2S may somewhat increase the early strength of the hardening cement (this effect being due to the considerable heat of hydration that this compound evolves). It does affect setting times.Tetracalcium Aluminoferrite (C4AF) contributes very slightly to strength gain. However. Contributes to the color effects that makes cement gray.


Need for cement Chemical AnalysisMagnesium Oxide (MgO) causes delayed expansion when present in large amounts. ASTM limits all cements to 6.0%.Sulfuric anhydride (SO3) is an indirect measure of the amount of gypsum or calcium sulfate (CaSO4) in the cement. Gypsum is added to cement for the purpose of regulating setting time. Too much gypsum can cause expansion and, therefore, SO3 is generally limited (C150)p 3 g y ( )Insoluble Residue is an indication of the efficiency of the burning process. (I.E. Determines the amount of unburnt raw materials (clay) ; ASTM limit is 0.75%Alkalies: Large amounts can cause certain difficulties in regulating set times of cement.. Also, increase the risk of ASR reaction. ASTM has an optional limit in total alkalies of 0.60%, calculated by the equation Na2O + 0.658 K2O.

The above is just to mention the severe effect of cement composition on its behavior


Chromium VIDo not use cement which contains, when hydrated, more than 0.0002 % (2 ppm) chromium (VI) by dry weight of cement.

It has Short term effect. Skin ulcers or allergy, gy,Irritation of the nasal mucosa, and holes in the nasal septum, Nosebleeds, Nausea, Itching. It also has long term effects like: Carcinogenic in human’s site, Lung and sinonasal cavity, runny nose, sneezing, and holes in the nasal septum, Kidney and liver damage, irritation of the gastrointestinal tract, stomach ulcers, and convulsions, Damage of the DNA, Death.


Shrinkage/Expansion testsC596 is used to develop data on the effect of a hydraulic cement on the drying shrinkage of concrete made with that cementC1038 is used to determine the amount of expansion of a mortar bar when it is stored in water. Expansion may become excessive when the cement contains too much

lf tsulfate.C452 is also used to establish that a sulfate-resisting Portland cement that meets the performance requirements of Specification C 150 by adding different % of gypsum to the cement and testing.C1012 provides a means of assessing the sulfateresistance of mortars made using Portland cement. The standard exposure solution used in this test method contains 50g of Na2SO4 /L.

Raw Materials- Water

Test MethodChemical analysis of water for use in concrete AASHTO-T26pH TDS Sulfate Chloride ASTM D516 D512pH, TDS, Sulfate, Chloride, Total alkalies.

ASTM D516, D512, C114, AASHTO T 26,

• Potable water is suitable for use in concrete.

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The most important chemical in water for concrete use is the Chloride. It is limited to 500 ppm for prestressed concrete or in bridge decks and to 1000 ppm for other reinforced

Raw Materials- WaterChloride

concrete in moist environments.Water for concrete curing is of equal importance to mixing water, especially that salt crystals remains at the surface after water evaporates and would later dissolve and penetrate at any occasion.

pH below 7 causes little deterioration (etching) of concrete.Sulfate shall not exceed 3000ppm. (rarely occurs)

Raw Materials- WaterOthers

occurs)Alkalies as (Na2O + 0.658 K2O) shall be <600 ppm; else, ASR reaction is more likely to occur (to be detailed soon).Total dissolved salts is limited to 50,000ppm (5%). (rarely occurs)

Test MethodPotential alkali reactivity,ASR & ACR ASTM C289 &…Chloride Content BS 1744 P1S lf C BS 1744 P1

Raw Materials- Aggregates

Sulfate Content BS 1744 P1Soundness by Sodium or Magnesium Sulfate ASTM C88Methylene blue absorption ASTM C837Organic impurities of fine aggregates ASTM C40


Alkali Reactivity –ASR/ACR

Some aggregates react with the alkali hydroxides in concrete, causing expansion and cracking over a period of many years. This alkali-aggregate reaction has two forms—alkali-silica reaction (ASR) and alkali-carbonate reaction (ACR).( )Will be detailed in Concrete section


Chloride and Sulfate

Effects and limits will be discussed under concrete.Acid or water soluble? The water soluble is the reactive part and is less than or maxthe reactive part and is less than or max equal to the acid soluble part.In other word acid soluble chloride or sulfate represents the total ppm but usually requested for safety.


SoundnessThis test measures aggregate soundness when subject to weathering action in concrete or other applications.Both Sodium and magnesium can be usedBoth Sodium and magnesium can be used alternatively but with different concentration.The allowable limits for soundness shall be 12 % if sodium sulfate is used and 18 % if Magnesium sulfate is used (5 cycles).

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Methylene Blue Absorption MBA

MBT is a direct measure of Clay %.MBT is a also a smart test that identify whether the decrease in the sand equivalent value is really due to clay presence or because of silt y y psize materials.Aggregates are considered excellent for MBT values <0.4g/100g and poor for values >1.0g/100g (Rock Manual) If Methylene blue test passes you can safely use your sand with moderate decrease in sand equivalent values

Raw Materials- Fine Aggregates

Organic impuritiesFine aggregate shall be free of injurious amounts of organic impurities. Aggregates producing a color darker than the standard shall be rejected.U f fi t f ili i th t t i tUse of a fine aggregate failing in the test is not prohibited, provided that, when tested for the effect of organic impurities on the strength of the mortar, the relative strength at 7 days, calculated in accordance with ASTM C 87, is not less than 95 %.

Raw Materials- Admixtures

Test MethodpH, specific gravity and

lid f d isolids content of admixture ASTM C494Sulfate content of admixture GravimetricChloride content of admixture

BS EN 480-10, Potentiometric


pH should be > 7. lower values could be an indication of admixture rancidity (expiration).Solid content and specific gravity are used for cost control. S lf t t t i d i i t jSulfate content in admix is not a major deicing chemical to concrete because of the relatively small contribution of admix. 10% of sulfate in admixture could be considered marginal compared to sulfate coming from the cement (See combined sulfate example in concrete)


Although chloride if harmful to concrete, only relatively high concentrations in admixture are significant.2000ppm of chloride in admixture can be reported as 0 0% (BS 5075: part 1 appendix E)reported as 0.0% (BS 5075: part 1 appendix E)The contribution of admixture is relatively small. But what if admix has 30% of its solid content chloride?Effects and limits of chloride and sulfate will be discussed under concrete.

What to test and Why?Fresh Concrete

Chemical testing of fresh or hardened concrete is i il

Test MethodWater content of fresh concrete ASTM C1079

similar.The most useful chemical test that can be conducted on fresh concrete is the water content. water content of fresh concrete can be conducted within an hour with high precision.Salt of known conc. is added to a measured amount of fresh concrete; the decrease in the salt conc. in the mix reflect the water content.

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What to test and Why?Hardened Concrete

Test MethodpH of concrete

Depth of carbonationusing phenol phthaleine indicatorASTM C1084 BS 1881

Cement contentASTM C1084, BS 1881-p124

Chloride content BS 1881-p124

Sulfate content BS 1881-p124Alkali-Silica or carbonate reactivity (ASR/ACR) Many...listed belowEvaluation of thaumasite sulfate attack

Hardened Concrete

pH and carbonationIn a normal good quality reinforced concrete, the steel reinforcement ischemically protected from corrosion by the alkaline nature of theconcrete. This alkalinity causes the formation of a passive oxide layeraround the steel reinforcement. Concrete will react withatmospheric carbon dioxide (or sulfur dioxide) to cause gradualneutralization of the alkalinity from the surface inwards, a processknown as carbonationknown as carbonation.The rate at which this occurs is a function of concrete quality, inparticular the cement content, the water/cement ratio and thecompaction.It is generally accepted that the rate of the carbonation reaction isinversely proportional to the square root of the age of the structure.

Concrete cover, mm = √(Age yrs)On this basis, even with a cover of only 10mm, steel reinforcement should be safe for up to 100 years.

Hardened Concrete

pH and carbonationPh Ph is an indicator of carbonation; alternatively pH can be measuredWhen carbonation take place the pH value will start falling. The normal pH-value of concrete is above 13 and the pH-value of fully carbonated concrete is below 9. Once the carbonation process reaches the reinforcement and the pH-value drops beneath 13 thereaches the reinforcement, and the pH value drops beneath 13 the passive “film” on the re-bars will deteriorate and corrosion will initiate.Carbonation is a very simple test but an essential indicator of concrete deterioration.Carbonation is easy to conduct but very tricky and various possible mistakes might end with misleading results. Examples, extracting the concrete in the presence of water may move hydroxides to carbonated areas giving high pH values or pink color instead of colorless.

Hardened Concrete

Cement ContentThe cement content of concrete is important from the aspect of durability, impermeability and strength.Too low a cement content may permit rapid carbonation and subsequent loss of the protective alkaline environment for the steelenvironment for the steel.Too high a cement content may cause excessive shrinkage, thermal cracking from the heat of hydration in large pourings, or the risk of alkali silica reaction if a susceptible aggregate has been used and the cement is not a low alkali type.How precise is the test? To the nearest 40Kg/m3

Hardened Concrete

Chloride- Full storyChloride in concrete can originate from two mainsources:a) "Internal" Chloride, i.e. chloride added to theconcrete at the time of mixing; for example,contamination of aggregates or admixtures and the useof sea water or other saline contaminated water.b) "External" chloride, i.e. chloride ingressing into theconcrete post-hardening. For example, de-icing saltapplied to many highway structures; and marine salt,either directly from sea water in structures such aspiers, or in the form of air-borne salt spray in structuresadjacent to the coast; and salts from contact withcontaminated soil.

Chloride does not react with steel but act as catalyst in the corrosion process.Chloride present in plain concrete that does not contain steel is generally not a durability concern.

Hardened ConcreteChloride

Chloride has nothing to do with durable concrete (high strength, low permeability, etc)However, over decades, the concrete would deteriorate and the chloride is still hiding and waiting.What if concrete is already weak, permeable, or carbonated?

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The result would be similar to the below (<20 years old):

Hardened ConcreteChloride

ACI 222.1, chapter 3:

Hardened Concrete

Chloride

For about 20% cement content 0.10% or 1000ppm by weight of cement is about 200ppm by weight of concrete

Contribution of each constituent-example

Mix Design as provided by the

batch plant

Weight (SSD)

% by weight, A

Chloride content, ppm,

B

Approx Chloride content by weight of

concrete, ppm, A x B /100

Total Chloride content by weight of cement, ppm =

total x 100/A

cement 370 15 130 20

Hardened Concrete

Chloride

cement 370 15 130 20

686

silica fume 15 1 0 0water 145 6 30 2superplasticizer 10.8 0.4 2000 9Coarse Aggregate 687 28 70 20Medium aggregate 370 15 70 11Crushed sand 291 12 70 8Natural sand 540 22 150 33Total 2429 100 103

Sulfate attack can be 'external' or 'internal'.Internal: due to a soluble source being incorporated into the concrete at the time of mixing, gypsum in the aggregate, for

Hardened Concrete

Sulfate

example.External: due to penetration of sulfates in solution (soluble), in groundwater for example, into the concrete from outside. Cement usually has 3% sulfate (insoluble form)

Sulfates can attack concrete causing an expansivedisruptive effect resulting in gradual deterioration of thecement matrix. The reaction occurs between the sulfatesalts and the tricalcium aluminate (C A) giving needle

Hardened Concrete .Sulfate

salts and the tricalcium aluminate (C3A) giving needlelike crystals of ettringite (calcium sulphoaluminate) of aconsiderably larger volume than the reactants and, ifgrowing in pores in restricted space, exert a burstingpressure on the concrete, causing cracking anddisruption.

Hardened Concrete

Sulfate- Ettringite

Microcracks filled with Ettringite

Ettringite formation in a pore of cement paste

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Contribution of each constituent-example 1


batch plant

Weight (SSD)

% by weight, A

Sulfate content, ppm,

B

Approx sulfate content by weight of


Total sulfatecontent by weight of cement, ppm =

total x 100/A

cement 350 15 30,000 4359

Hardened Concrete

Sulfate

cement 350 15 30,000 4359

33473

silica fume 15 1 0 0water 145 6 200 12superplasticizer 10.8 0.4 100,000 448Coarse Aggregate 687 29 250 71Medium aggregate 370 15 250 38Crushed sand 291 12 200 24Natural sand 540 22 300 67Total 2409 100 5021

Contribution of each constituent-example 2


batch plant

Weight (SSD)

% by weight, A

Sulfate content, ppm, B

Approx Sulfate content by weight of


Total Sulfate content by weight of

cement, ppm = total x 100/A

cement 400 15 30000 4880

Hardened Concrete

Sulfate

33984

silica fume 15 1 0 0water 145 6 200 12superplasticizer 10.8 0.4 100,000 448Coarse Aggregate 687 29 250 71Medium aggregate 370 15 250 38Crushed sand 291 12 200 24Natural sand 540 22 300 67Total 2409 100 5021

One more bag of cement/m3 contributes as much as 100000 ppm of admix.

Hardened Concrete

SulfateHardened Concrete


Some aggregates react with the alkali hydroxides in concrete, causing expansion and cracking over a period of many years. This alkali-aggregate reaction has two forms—alkali-silica reaction (ASR) and alkali-carbonate reaction (ACR).( )Alkali-silica reaction (ASR) is more common. In ASR, aggregates containing certain forms of silica will react with alkali hydroxide in concrete to form a gel that swells as it adsorbs water from the surrounding cement paste or the environment. These gels can swell and induce enough expansive pressure to damage concrete

Hardened Concrete


Alkali-carbonate reactions (ACR) are observed with certain dolomitic rocks. The breaking down of dolomite, is normally associated with expansion. The deterioration caused by ACR is similar to that caused by ASR; however, ACR is relatively rare because aggregates , y gg gsusceptible to this phenomenon are less common and are usually unsuitable for use in concrete for other reasons. (like abrasion, absorption, etc.)

Hardened Concrete

Test Methods for Alkali Reactivity

Table: Test Methods for Alkali-Silica Reactivity (Source: Farny and Kerkhoff, 2007)

Test Name PurposeASTM C 227,Potential alkali-reactivity of cement-aggregate combinations (mortar-bar method)

To test the susceptibility of cement-aggregate combinations to expansive reactions involving alkalies

ASTM C 289,Potential alkali-silica reactivity of aggregates

To determine potential reactivity of siliceous aggregates

ASTM C 294, To give descriptive nomenclature for the more common or important natural minerals—an aid inConstituents of natural mineral aggregates common or important natural minerals—an aid in determining their performance

ASTM C 295,Petrographic examination of aggregates for concrete

To outline petrographic examination procedures for aggregates—an aid in determining their performance

ASTM C 342,Potential volume change of cement-aggregate combinations

To determine the potential ASR expansion of cement-aggregate combinations

ASTM C 441,Effectiveness of mineral admixtures or GBFS in preventing excessive expansion of concrete due to alkali-silica reaction

To determine effectiveness of supplementary cementing materials in controlling expansion from ASR

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Hardened Concrete

Test Methods for Alkali Reactivity

Table: Test Methods for Alkali-Silica Reactivity (Source: Farny and Kerkhoff, 2007)

Test Name Purpose

ASTM C 856,Petrographic examination of hardened concrete

To outline petrographic examination procedures for hardened concrete—useful in determining condition or performance

ASTM C 856 (AASHTO T 299),Annex: Uranyl- acetate treatment procedure

To identify products of ASR in hardened concrete

To identify products of ASR in hardenedLos Alamos staining method (Powers 1999) To identify products of ASR in hardened concrete.

ASTM C 1260 (AASHTO T303),Potential alkali reactivity of aggregates (mortar-bar method)

To test the potential for deleterious alkali-silica reaction of aggregate in mortar bars

ASTM C 1293,Determination of length change of concrete due to alkali-silica reaction (concrete prism test)

To determine the potential ASR expansion of cement-aggregate combinations.

ASTM C 1567, Potential alkali-silica reactivity of combinations of cementetious materials and aggregate (accelerated mortar-bar method)

To test the potential for deleterious alkali-silica reaction of cementetious materials and aggregate combinations in mortar bars

Hardened Concrete

Thaumasite Sulfate Attack (TSA)The availability of carbonate ions (CO3)2- changes the reaction products when sulfates enter the concrete. Below about 15°C in the presence of water, the reactions between the calcium silicate hydrate, the carbonate and the sulfate ions produces thaumasite p(CaSiO3.CaCO3.CaSO4.15H2O). The calcium silicate hydrates provide the main binding agent in Portland cement, so this form of attack weakens the concrete as well as causing some expansion and, in advanced cases, the cement paste matrix is eventually reduced to a mushy, incohesive mass (see pic).

Hardened Concrete

Thaumasite Sulfate Attack (TSA)

Thaumasite has formed around coarse limestone aggregate

Since TSA does not depend on the level of calcium aluminate hydrates, Sulfate resisting concretes (SRPC, low C3A) can be also susceptible to this form of attack.Concretes containing granulated ground blastfurnace slag (GGBS) as part of the cement have good

Hardened Concrete

Thaumasite Sulfate Attack (TSA)

g ( ) p gresistance to TSA. Decreasing permeability can be good defense against TSA.

Hardened Concrete

Other Circumstances

Concrete subject to fireConcrete subject to contact with chemicals (spillage, contaminated soil or water, etc)Concrete subject to renovation or addition ofConcrete subject to renovation or addition of structureConcrete showing some sorts of damage (Crack, efflorescence, spalling, coloring, etc)

What to focus on?Concrete under Specific circumstances

Situation Tests in order RemarkConcrete subject to fire

Visual, strength, carbonation, tensile of steel, load test, …

Conducted subsequently.

Concrete in contact with deicing chemicals

Chloride, sulfate, permeability, steel condition (corrosion), Petrographic, etc

•Petrographic might be needed toidentify possible defectschemicals etc. defects

Concrete subject to renovation or addition of structure

Visual, strength, carbonation, tensile of steel, chloride, sulfate, steel condition (corrosion), Steel scan, dimensions, etc.

Concrete showing some sorts of damage-Crack

Visual, crack monitoring, strength, carbonation, tensile of steel, chloride, sulfate, steel condition (corrosion), ASR detection, thaumasite detection, petrographic, etc.

Crack causes are numerous; further testing might be conducted progressively.

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When water penetrates into concrete, it dissolves the non-hydraulic CH (and various salts, sulfates and carbonates of Na, K, Ca)Remember C-S-H and CH is produced upon hydration of C S and C S

Hardened Concrete

Concrete Efflorescence

hydration of C3S and C2SThese salts are taken outside of concrete by water and leave a salt deposit.

Concrete – Best Property

I nominate “Impermeability” as the best immunity for best durable concrete

What about you?What about you?

Thank you for being durable to such presentation.p

Documents

Concrete Chem testing-TQP pres.ppt Methylene blue test passes you can safely use your sand with moderate decrease in sand equivalent values Raw Materials- Fine Aggregates Organic impurities