Synergic effect of some waste pozzolans on the mechanical and shielding properties of geopolymer concretes

Abstract

This work aimed to investigate the effect of raw materials to geopolymer concrete; such as silica fume, metakaolin, ground granulated blast-furnace slag, and quartz powder on mechanical (compressive strength, flexural strength), physical, transport, and nuclear radiation shielding properties. The silica fume, metakaolin, ground granulated blast-furnace slag, and quartz powder used singly and/ or in combination for geopolymer mixture along with sodium-based solutions. Four different geopolymer mixtures were prepared and cured at three different temperatures (30°C, 60°C and 90°C) for three curing periods (5, 7 and 9 h). Then, the mineralogical and morphological properties were considered with X-ray diffraction (XRD), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) tests. Based on the findings, the use of metakaolin in the geopolymer mixture increased both the compressive and flexural strengths. In addition, the compressive strength of 137.5 MPa was reached in the mixture using metakaolin at 90°C and in a short period of curing, like 9 h. The metakaolin (MK) is decreased the sorptivity coefficient of the geopolymer concrete samples. Withal, extensive experimental measurements were performed to investigate the gamma-ray and fast neutron shielding properties of fabricated concretes. The mass attenuation coefficient enjoyed values such as 0.2078, 0.2078, 0.2079 and 0.2081 cm2/g for M1, M2, M3 and M4 geopolymer concretes, respectively. It was reported that the geopolymer concretes attenuated the fast neutron flux with the energy of about 4.5 MeV by 35%. All inspected geopolymer concretes exhibited excellent neutron attenuation properties, as their values ΣR greater than those of commonly used ones as the neutron absorbers.