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CIP 33 - High Strength Concrete

CIP 33 - high Strength ConcreteWHATis high Strength Concrete ?WHYdo We Need high Strength Concrete ?HOWto Design high - Strength Concrete Mixture?It is a type of high performance Concrete generallywith a specified compressive Strength of 6,000 psi (40 MPa) or greater. The compressive Strength is mea-sured on 6 12 inch (150 300 mm) or 4 8 inch (100 200 mm) test cylinders generally at 56 or 90-days orsome other specified age depending upon the applica-tion. The production of high Strength Concrete requiresmore research and more attention to quality controlthan conventional To put the Concrete into service at much earlierage, for example opening the pavement at To build high -rise buildings by reducing column sizesand increasing available To build the superstructures of long-span bridgesand to enhance the durability of bridge To satisfy the speci

CIP 33 - High Strength Concrete WHAT is High Strength Concrete? WHY do We Need High Strength Concrete? HOW to Design High-Strength Concrete Mixture? It is a type of high performance concrete generally with …

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Transcription of CIP 33 - High Strength Concrete

1 CIP 33 - high Strength ConcreteWHATis high Strength Concrete ?WHYdo We Need high Strength Concrete ?HOWto Design high - Strength Concrete Mixture?It is a type of high performance Concrete generallywith a specified compressive Strength of 6,000 psi (40 MPa) or greater. The compressive Strength is mea-sured on 6 12 inch (150 300 mm) or 4 8 inch (100 200 mm) test cylinders generally at 56 or 90-days orsome other specified age depending upon the applica-tion. The production of high Strength Concrete requiresmore research and more attention to quality controlthan conventional To put the Concrete into service at much earlierage, for example opening the pavement at To build high -rise buildings by reducing column sizesand increasing available To build the superstructures of long-span bridgesand to enhance the durability of bridge To satisfy the specific needs of special applica-tions such as durability, modulus of elasticity, andflexural Strength .

2 Some of these applications in-clude dams, grandstand roofs, marine foundations,parking garages, and heavy duty industrial floors.(Note that high Strength Concrete does not guar-antee durable Concrete .)Optimum Concrete mixture design results from select-ing locally available materials that make the fresh con-crete placeable and finishable and that ensure thestrength development and other desired properties ofhardened Concrete as specified by the designer. Someof the basic concepts that need to be understood forhigh Strength Concrete are:1. Aggregates should be strong and durable.

3 Theyneed not necessarily be hard and of high strengthbut need to be compatible, in terms of stiffnessand Strength , with the cement paste. Generallysmaller maximum size coarse aggregate is usedfor higher Strength concretes. The sand may haveto be coarser than that permitted by ASTM C 33(fineness modulus greater that ) because of thehigh fines content from the cementitious high Strength Concrete mixtures will have a highcementitious materials content that increases theheat of hydration and possibly higher shrinkageleading to the potential for cracking. Most mixturescontain one or more supplementary cementitiousmaterials such as fly ash (Class C or F), groundgranulated blast furnace slag, silica fume,metakaolin or natural pozzolanic high Strength Concrete mixtures generally need tohave a low water-cementitious materials ratio (w/cm).

4 W/cm ratios can be in the range of These low w/cm ratios are only attainablewith quite large doses of high range water reduc-ing admixtures (or superplasticizers) conformingto Type F or G by ASTM C 494. A Type A waterreducer may be used in high Strength Concrete20014. The total cementitious material content will be typi-cally around 700 lbs/yd3 (415 kg/m3) but not morethan about 1100 lbs/yd3 (650 kg/m3).5. The use of air entrainment in high Strength con-crete will greatly reduce the Strength attention and evaluation will be necessary if thejob specification sets limits for other Concrete proper-ties such as creep, shrinkage, and modulus of elastic-ity.

5 The engineer may set limits on these properties forthe design of the structure. Current research may notprovide the required guidance for empirical relation-ships of these properties from traditional tests and someof these tests are quite specialized and expensive toconduct for mixture evaluation. From theoretical con-siderations, lower creep and shrinkage, and high modulusof elasticity can be achieved with higher aggregate andlower paste volumes in the Concrete . Using the largestsize aggregate possible and medium to coarsely gradedfine aggregate can attain this. Smaller maximum sizeaggregate such as 3/8 inch ( ) can be used toproduce very high compressive Strength but requiredproperties like creep, shrinkage, and modulus of elas-ticity may be sacrificed.

6 If difficulty is encountered inachieving high Strength , simply adding more cementitiousmaterial may not increase Strength . Factors such asdeleterious materials in aggregates, aggregate coatings,coarse aggregate fracture faces, shape and texture,and testing limitations may prevent higher Strength frombeing achieved. Final Concrete mixture proportions aredetermined by trial batches either in the laboratory orby small size field production batches. The production,transportation, placement and finishing of high -strengthconcrete can differ significantly from procedures usedfor conventional Concrete .

7 For critical projects it is highlyrecommended that a trial pour and evaluation be con-ducted and included as a pay item in the contract. Pre-bid and pre-construction meetings are very importantto ensure the success of projects using high strengthconcrete. During construction, extra measures shouldbe taken to protect against plastic shrinkage and ther-mal cracking in thicker sections. high Strength con-crete may need longer time before formwork is Strength Concrete test cylinders should be care-fully molded, cured, capped, and tested. Extra care andattention to handling of test cylinder specimens at veryearly age is necessary.

8 Slower setting time of highstrength concretes may be experienced. The ASTMS tandards are continuously being revised to accountfor additional special precautions needed when testinghigh Strength Concrete . Particular attention should bepaid to the type of mold, curing, type of cylinder cap-ping material, and characteristics and load capacity ofthe testing Report on high Strength Concrete , ACI 363R,ACI International, Farmington Hills, MI, to Quality Control and Testing of high Strength Con-crete, ACI , ACI International Farmington Hills, a balanced mix design for high Strength Concrete , BryceSimons, The Concrete Producer, October 1995, Started with high - Strength Concrete , Ron Burg, TheConcrete Producer.

9 November of Testing Variables on the Measured CompressiveStrength of high Strength (90 MPa) Concrete , Nick J. Carino,et al., NISTIR 5405, October 1994, National Institute of Stan-dards and Technology, Gaithesburg, MD, ,000 psi Concrete , James E. Cook, ACI Concrete Interna-tional, October 1989, ACI International, Farmington Hills, MI.


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