Abstract
•Low cost ZnFe2O4 spinel nanoparticles prepared at different temperatures.•The influence of particle size of synthesized nanospinel on the physico-mechanical characteristics.•ZnFe2O4 spinel nanoparticles act as nucleation sites for the hydration reaction.•ZnFe2O4 spinel nanoparticles improve the fire resistivity and linear attenuation coefficient values for OPC pastes.
The purpose of this investigation is the utilization of low cost ZnFe2O4 spinel nanoparticles (ZFs NPs) for enhancing the physico-mechanical, fire resistivity, morphological characteristics and gamma radiation shielding of hardened ordinary Portland cement (OPC) pastes. Spinel dried gel was fabricated via simple sol gel regime. The dried gel was calcined at different temperatures (400, 500, 600 and 700 °C) to fabricate ZFs NPs of different particle sizes. ZFs NPs were admixed to OPC via the addition of different doses (0.25, 0.5, 1 and 2 mass%) of ZFs NPs attained at 400 °C. On the other hand, 1 mass % of ZFs NPs obtained at 400, 500, 600 and 700 °C was admixed to OPC. The physico-mechanical characteristics for the various OPC-ZFs NPs composite pastes were investigated at various hydration times. Fire resistivity test was performed for all pastes for 3 h at 300, 500 and 700 °C. XRD, TGA/DTG, and SEM/EDX techniques were adopted to define phase composition and microstructure of the various hardened pastes. The results demonstrated that addition of 1% ZF500 NPs upgraded the compressive strength of hardened OPC pastes by 62, 35, 24, 25 and 22% after 1, 3, 7, 28 and 90 days of curing, respectively and at the same time upgraded γ radiation shielding by 113, 125, 130% after 3, 28 and 90 days of curing in water, correspondingly. Besides, improved fire resistance features were attained by the same addition. XRD, TGA/DTG, and SEM/EDX techniques confirmed that, diverse hydration yields like CSHs, CASHs, CAHs, CFSH, CFH and CZH were developed in presence of ZF500 NPs.