Effects of a New Generation of Superplasticizers on the Properties of Fresh Concrete

Different superplasticizers have been tested in order to evaluate their effect on concrete properties and to express concrete's rheology in fundamental parameters such as yield stress and plastic viscosity. Measurements were made on concrete's rheology with two different viscometers, once for mortar and one for results from slump tests at different times after mixing, slump loses by means of time required to lose 30 mm of slump and time required to lose half the initial slump value were calculated. The time necessary before trowelling was also measured. Results show that viscosity-measurements on mortar give useful information about the fresh concrete's properties, information that cannot be attained with the traditional methods, such as slump, spread, etc. The method of evaluating trowelling hardness very efficiently measures the admixture's effect on retardation. Only those superplasticizers containing new types of acrylic and vinyl polymers show effects efficient enough to belong to the second generation.