Method to determine mixture proportions of workable ultra lightweight cement composites to achieve target unit weights

Abstract

Ultra lightweight cement composite (ULCC) is a type of composite characterized by low unit weights <1500kg/m3 and high compressive strengths of up to about 65MPa. The low unit weight is achieved by incorporating cenospheres as micro-lightweight aggregates in cement paste. As the cenospheres are by-products from coal burning power plants, their properties may vary greatly. This results in great difficulty in determining the mixture proportions of the ULCC. In this research, a new design method is developed and proposed that can be used to effectively determine the mixture proportions of workable ULCC to achieve a desired target unit weight with minimal laboratory trials. The relationship between the spacing among spherical cenospheres and the water-to-cementitious materials ratio (w/cm) needed to achieve the target workability is the basis of this design method. For a given cenosphere sample, if its particle size distribution and particle density are determined, it is possible to design a mixture of ULCC using this method.