High-Strength Concrete With Limestone Filler Cements

For high strength concrete, the use of superplasticizer and high cement content leads to a very low water to cement ratio. In this concrete, the cement used cannot complete its hydration due to the unavailable space to locate the reaction products. In this case, the addition of limestone filler can modify the packing of cement grains, and it increases the hydration degree of portland clinker leading to the same strength level. In Europe, a vast experience has been developed with limestone blended cements. However, the use of limestone filler is a recent practice in South American countries. In this paper, the effect of a limestone filler in the production of high strength concrete was studied using 0, 9.3, and 18.1 percent of replacement by mass of clinker. Concretes were designed to achieve 50 MPa compressive strength at 28 days (450 kg/(m cubed) of cement content and a water-to-cementitious material ratio of 0.34). The mechanical properties, including compressive strength, split tensile strength and elasticity modulus were evaluated at 1, 3, 7, 28, and 150 days. The results show that limestone filler increases concrete strength at very early ages due to enhanced clinker grains hydration. It did not affect significantly the mechanical strength of concrete containing 9.3 percent of replacement while for concretes with 18.1 percent of filler, a relative strength reduction was observed after seven days. At all ages, limestone filler replacement improves clinker efficiency but, it decreases with hydration progress.