Impact of hydrotalcite phases on the texture characteristic of OPC and its correlation with compressive strength and gamma Attenuation

Hydrotalcites (HTs), recognized for their eco-friendly synthesis, layered structure, and exceptional ion-exchange capacity, offer significant potential as functional additives in cementitious systems. Most previous studies used different types of HT based on varying the kinds of di- or tri-valent cations during the preparation process, but they did not change the ratio between them. Accordingly, this study tailored three Mg-Al-CO₃-based HTs with varying Mg: Al ratios (1:1, 2:1, and 3:1, designated HT1, HT2, and HT3) and incorporated them at 1 wt% into ordinary Portland cement (OPC) pastes. The effects of HTs on setting time, workability, and compressive strength were evaluated. Phase composition, textural properties, and microstructure of reference and HT-modified pastes were characterized using XRD, BET/BJH analyses, and SEM/EDX. Additionally, gamma-ray shielding performance against Cs-137 (661.64 keV) was assessed by determining the linear attenuation coefficient (µ) and half-value layer (HVL). Results reveal that HTs accelerate setting, slightly reduce workability, enhance compressive strength, and significantly improve radiation shielding. Among the tailored HTs, HT1 exhibited superior performance, achieving the highest compressive strength (88.8 MPa at 28 days) and greatest shielding efficiency, with µ increased by 112.5% and HVL reduced by 52.9% compared to OPC. These improvements are attributed to HT1's high surface area, amorphous/mesoporous nature, and its role as a nucleation site and filler, leading to a dense microstructure. Furthermore, incorporating HTs provides an environmentally sustainable approach for producing high-performance cementitious materials with enhanced mechanical and radiological properties, supporting industrial applications in construction and nuclear safety.