Performance characteristics of concrete containing natural and artificial pozzolans

Abstract

In this research, the effects of natural zeolite (NZ) and rice stalk ash (RSA) as Portland cement replacement materials on properties of cement were investigated using three different combinations (NZ, RSA, NZ+RSA) of tests. These materials were used as substituted for Portland cement in different proportions, and then physical, mechanical and thermal properties, namely, unit weight, compressive strength, splitting tensile strength, water absorption, freezing-thawing resistance and thermal conductivity values were determined. According to the experimental results, the unit weights of the concretes produced with NZ, RSA ranged from 2169 to 2236 kg/m(3) and it decreased slightly with the increasing content of NZ and RSA in the mixture. The ranges of compressive strengths of the substituted materials for NZ, RSA and NZ+RSA were 17.75-25.61 MPa, 21.28-27.15 MPa and 15.79-20.89 MPa, respectively. The splitting tensile strength ranged from 1.29 to 2.16 MPa. The pozzolan concretes water absorption races for NZ, RSA and NZ+RSA were 5.34-5.74%, 5.23-4.86% and 5.04-5.16%, respectively. In addition, the thermal conductivities varied between 1.589 and 1.729 W/mK. The results of this study showed that the use of NZ and RSA pozzolans at 5% of the weight of cement improved the performance characteristics of the concrete.