Design specialist, Ontario Hydro, Toronto,
Head, Construction Materials Section, Canada Centre for Mineral and Energy Technology, Ottawa,
This report describes the performance of superplasticizers used as water-reducing admixtures in concrete. Various dosages of three commercially available superplasticizers were added to air-entrained reference concretes containing ASTM Type I, Type II, and Type V cements (ASTM Standard Specification for Portland Cement [C 150–78a]) to produce a 20% water reduction. The cement content, slump, and air content were kept constant in all mixes. The mechanical and elastic properties of hardened concrete and its freeze-thaw resistance were determined. The test results show that in all cases the strength and modulus of elasticity of the specimens cast from superplasticized concrete exceed those of the reference specimens. For concretes made with Type I cement, the concrete containing superplasticizers shows more shrinkage than the reference concrete, whereas for the other cements the shrinkage of the superplasticized concretes is comparable to or less than that of the reference concrete. The Type I portland cement concrete containing the melamine-based superplasticizer exhibits essentially the same creep as the reference concrete. The freeze-thaw durability of the superplasticized concrete containing either Type I or Type II cements appears to be satisfactory; however, concrete made with Type V cement and incorporating superplasticizers shows relatively poor resistance to freeze-thaw cycling.
Paper ID: CCA10404J