This study evaluates a wet-activated multicomponent organomineral modifier for sustainable concrete. The modifier was produced by co-grinding Portland cement and rice husk ash (RHA) in the presence of Sika^® ViscoCrete^®-20HE and was subsequently combined with polypropylene fibers. Three modified mixtures were tested after 28 days of curing and compared with a control concrete. The modified concretes achieved compressive strengths of 42.2–45.0 MPa, compared with 36.8 MPa for the control. Among the tested formulations, Mix 2, containing 6 wt.% RHA, 4 wt.% polypropylene fibers, and 1.3 wt.% superplasticizer, showed the most favorable overall performance. Its compressive and flexural strengths reached 45.0 and 5.8 MPa, corresponding to observed differences of 22.3% and 26.1%, respectively, relative to the control formulation. Because the complete mixture compositions and w/c ratios differed, these comparisons do not isolate the contribution of any individual constituent. Fracture toughness increased from 1.15 to 2.16 MPa·m^1/2, water absorption decreased from 6.8% to 5.1%, and freeze–thaw resistance increased from 138 to 242 cycles. Qualitative SEM and XRD observations showed morphological and phase-related differences between selected control and modified specimens; however, these observations did not establish the causes of the measured performance differences. In addition, because no compositionally identical non-activated RHA reference or direct reactivity test was included, the independent effect of wet activation on RHA reactivity could not be established. The investigated integrated modifier therefore shows potential for improving concrete performance while enabling the beneficial use of RHA.

The present study investigates the development of non-autoclaved aerated concrete (NAAC) incorporating rice husk ash (RHA)-derived amorphous silica, polypropylene microfibers, and a polycarboxylate-based superplasticizer to improve mechanical performance and durability while maintaining low density and thermal conductivity. Experimental investigations included density, compressive strength, thermal conductivity, water absorption, X-ray diffraction (XRD), microstructural observations, and TG–DTA analysis. The developed compositions containing 5–7% RHA and 0.10–0.20% polypropylene microfibers achieved compressive strength values of 4.5–4.8 MPa at densities of 520–560 kg/m³, which are comparable to or higher than values commonly reported for non-autoclaved aerated concrete of similar density. Thermal conductivity decreased to 0.12–0.13 W/(m·K), while water absorption was reduced to 15–18%. XRD, microstructural, and TG–DTA analyses suggested enhanced hydration reactions and improved development of the cementitious matrix due to pozzolanic interaction between amorphous silica and calcium hydroxide. The incorporation of polypropylene microfibers was associated with improved structural homogeneity of the developed NAAC compositions, whereas the superplasticizer enhanced mixture homogeneity and pore stability. The results suggest that the combined use of agricultural waste-derived silica and fiber reinforcement provides an effective approach for producing sustainable and energy-efficient NAAC without autoclave curing.