INFLUENCE OF DURABILITY ON MECHANICAL PROPERTIES OF PQC MIX

Abstract

The present study deals with the changes due to the addition of mineral admixtures such as wollastonite, flyash and silicafume on the workability, strength and durability of concrete. The workability studies have been carried out by using various w/c or w/ca ratios such as 0.55. Three different mineral admixtures were chosen and they were added in three different dosages I, II and III mixed thoroughly with the M25 designed concrete mix, cured for 7 days and 28 days and then tested. Dosage I consists of wollastonite or flyash 10% plus 5% silicafume, dosage II consists of wollastonite or flyash 15% plus 5% silicafume and dosage III consists of wollastonite or flyash 20% plus 5% silicafume. The specimens were tested for various strength properties such as compressive strength or flexural strength with and without admixtures and the results were compared. Addition of mineral admixtures reduces the mid span and 1/3rd span deflections in the flexural strength test and thus increases the flexural stiffness. Mineral admixtures result in a better dispersion of cement particles during mixing resulting in a dense concrete than the conventional cement concrete. This increased the mechanical properties such as compression and flexural strength even after 7 days and 28 days of hydration. Since the strength enhancement is more due to the addition of admixtures, it facilitates the removal of form work at early ages. The pore size distribution of concrete significantly affects the mechanical properties of the concrete or in other word reduction in the pore size distribution significantly increases the compressive as well as tensile strength of the harden concrete.