Field Performance Of Concrete Admixtures

80393139812825PDFResearch Paper310563Portland cement concreteCompressive strengthAdmixturesRetarders (Concrete)Mix designSouth DakotaHansen, M.R.Flottmeyer, Brenda L.South Dakota School of Mines and TechnologySouth Dakota. Dept. of TransportationNTL-HIGHWAY/ROAD TRANSPORTATION-MaterialsNTL-HIGHWAY/ROAD TRANSPORTATION-Pavement Management and PerformanceUS Transportation CollectionThis project investigated compatibility problems involving two concrete admixtures from W.R. Grace Products and Dacotah portland cement. The problems experienced by the South Dakota Department of Transportation (SDDOT) were described as rapid slump loss, premature stiffening, and low compressive strengths. The materials investigated in this report are commonly used by the SDDOT in concrete construction projects. The research objectives were met by performing mortar and concrete flow table tests to verify compatibility between Dacotah cement and a high-range water-reducing admixture (HRWRA) and a retarder. The flow table tests were also used to determine an optimum time of addition for the admixtures. A five factorial statistical design to create thirty-three concrete mix designs was used in an effort to reproduce a compatibility problem. Finally, a field demonstration project was conducted to verify compatibility between the cement and admixtures under field conditions. Maximum dosages of each admixture were used in an attempt to create a compatibility problem. The mortar flow table test of Type V cement and HRWRA exhibited an optimum time of addition of the admixture to be at four minutes. The retarder showed no effect on the flow table results. Concrete mortar flow table results showed an improved performance with delayed addition of both the HRWRA and retarder. Analysis of the 33 concrete mixtures showed no general incompatibility between the cement and admixtures when the manufacturers' recommended mixing procedures were followed. The field demonstration displayed incompatibility between the cement and both admixtures; however, both admixtures were used at the maximum recommended dosages. 4 References, 11 figures, 8 tables. 38p