Prediction of compressive and tensile strengths of zeolite-cemented sand using porosity and composition

Abstract

The current paper aims to examine the effects of cement and zeolite contents on the strength of zeolite-cemented sand using the unconfined compressive strength (UCS) and splitting tensile strength (qt). First of all, the optimum content (i.e., the corresponding water content to the maximum UCS) was obtained from the response surface (RSM) and central composite design (CCD) methods. Then, unconfined compression and splitting tensile tests considering four distinct porosity percentages (η) related to Drsand = 35, 50, 70 and 85% (Dr = relative density), five cement contents (2, 4, 6, 8, and 10%), and six different percentages of zeolite replacement (0, 10, 30, 50, 70 and 90%) were performed. Then, the amounts of the improved UCS and qt of the specimens as a result of the porosity, zeolite and cement were measured. The results indicated that the 30% replacement of cement with zeolite (Z) was found the optimum amount of replacement. The strength improvement rate of the optimum zeolite-cemented sand (Z = 30%) compared to the mere cemented sand (Z = 0%) increased with the increase in the cement content as well as increase in the porosity of the compacted mixture. Based on the results of the zeolite-cement-sand mixtures, it has been shown that the UCS and qt improved by increasing the cement content (C). Also, the power function is well-matched to fit (UCS and qt)-C. The active composition parameter (AC) participate in the chemical reaction was introduced, as the minimum amount of either CaO or Al2O3 + SiO2. Afterward, the UCS and qt were plotted against the porosity/active composition parameter (η/AC), which is regarded as a controlling and key parameter of the UCS and qt. Also, the experimental results and the parameter of η−1.79AC1.43 introduce an acceptable description of the mechanical strength. Finally, the qt/UCS relationship is unique for the zeolite-cemented sand studied, being independent of the η/AC.