Amelioration of antimicrobial, radiation shielding, thermal stability of Portland cement composites using hematite nanoparticles

Egypt occupies a great position in the marble and cement industries in the Middle East. Therefore, marble waste has become a source of environmental nuisance while the cement industry represents environmental and economic threats due to carbon-foot print and energy consumption. Hence, the main objective behind this work is to produce smart cementitious materials based on recycling a large amount of volatile silica (VS as a source of silica) and marble sludge powder (MSP as a source of calcium) in addition to the inclusion of low-cost/small doses of mesoporous hematite nanoparticles (MPH) which controlled in the final performance of hardened composites such as compressive strength, thermal stability, gamma radiation shielding, and antimicrobial activity. It was found that replacing OPC with 20% industrial waste (10%VS +10%MSP) led to trivial decrease in the compressive strength value, from 67.8 to 64.5 MPa, at 28-days of normal curing. A turning point was observed after the individual inclusion of 0.25, 0.5, and 1 mass% of MPH nanoparticles to the prepared blend (80%OPC+10%VS+10%MSP) as the strength values increased from 64.5 to 70.5, 74.3, and 80 MPa, respectively. After 28 days of hydration, all composite pastes were exposed to elevated temperatures at 250, 550, and 850 degrees C (for 3hrs). The outcomes indicated the highest thermal resistivity for the nano-blend containing 1% MPH (coded C20-1MPH). XRD, TGA/DTGA, and SEM/EDX techniques detected various types/morphologies of hydration products. Furthermore, the agar diffusion test confirmed that more developed antimicrobial performance against Bacillus Subtilis, Klebsiella, Aspergillus niger, and Aspergillus fumigatus, has been attained via the cementitious discs containing C20-1MPH composite. The results of radiation shielding affirmed that C20-1MPH hardened composite, at 28 days of hydration, possessed the highest linear attenuation coefficients (mu= 0.14047 +/- 0.0016 cm(-1) and 0.10175 +/- 0.0026 cm(-1)) whatever the type of gamma radiation source (Cs-137 or Co-60).