The influence of mineral admixtures on the theology of cement paste and concrete

Rheological tests on cement paste were used to successfully select the type and dosage of mineral admixtures that improved concrete workability, Among the six different mineral admixtures tested, the ultrafine fly ash (UFFA) was determined to give the best results by reducing the yield stress and viscosity. These improved theological properties were not achieved by increasing the water demand and/or the high-range water reducer (HRWR) admixtures dosage. Therefore, the addition of UFFA improved the concrete flow without a potential decrease of the hardened properties or an increase in cost. The conclusions reached based on cement paste tests were validated by concrete slump tests. The cement paste theological data were also compared using two simpler tests, minislump and Marsh cone. The goal was to determine whether the simpler tests could be used to characterize the theology of cement paste adequately. The conclusions are that these simpler tests are unreliable for measuring workability. (C) 2001 Elsevier Science Ltd. All rights reserved.