Study on Shrinkage and Elastic Modulus of Limestone Calcined Clay Cement Concrete

In Africa, one of the most promising options for lowering costs and environmental impact of concrete is the use of limestone calcined clay cement (LC3) systems. However, improper use of the constituent materials may result in a concrete with substandard properties. The results reported here are part of a larger study on the properties of LC3 concrete made with African rawmaterials and focus on deformation properties including drying shrinkage and elastic modulus of concrete with three different clinker levels and four different clays from South Africa and Tanzania, which are compared with two reference mixes; one with 100% CEM II/A-L 52.5 N and the other with 50% of cement replaced by ground granulated blast-furnace slag. Overall, it can be concluded that the LC3 mixes produce lower shrinkage strain than the reference mixes provided that the alkali level in the system is not high. The performance is mainly related to the high internal surface area of the clays which absorb some of the available water in the system, a resulting that the rate of loss of moisture in the paste is reduced. Also, results indicate that the elastic modulus performance of the LC3 concrete, regardless of the clinker content and type of clay, is similar to that of the reference mixes.