Year-Round Accelerating Admixture


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Title: Year-Round Accelerating Admixture

Author(s): J. W. Brook and R. J. Ryan

Publication: Special Publication

Volume: 119


Appears on pages(s): 535-556

Keywords: accelerating agents; admixtures; cold weather construction; concretes; curing; freeze-thaw durability; freezing; protection; strength; temperature; water content; Materials Research

Date: 9/1/1989

An innovative chemical admixture has been developed which is effective between -7 and 35 C (20 and 95 F) and which is useful year-round. High dosage levels of 3910 to 5860 ml/100 kg (60 to 90 oz/cwt) of cement help to prevent concrete from freezing in cold weather at -7 to 0 C (20 to 32 F) ambient temperature while providing required set time and strength acceleration. Lower dosage rates of up to 1955 ml/100 kg (30 oz/cwt) of cement provide better acceleration at more moderate ambient temperatures. It provides the ability to better control set time of concrete that is retarded because cement has been replaced by fly ash. A variety of tests have shown that the admixture does not initiate corrosion of steel reinforcement embedded in concrete. Laboratory data is presented that demonstrates that the new chemical admixture provides strong, durable concrete with accelerated set, lower water demand, increased strength development, and will help prevent freezing in cold environments as low as -7 C (20 F) ambient temperature when properly air entrained. The use of warm concrete mix components and curing conditions normally practiced in the industry and recommended by ACI in newly published guidelines for cold weather concreting are not entirely necessary. Finally, use of this all-temperature accelerating admixture provides savings in both concreting cost and time.