Development of nano-silica modification to enhance the micro-macro properties of cement-based materials with recycled clay brick powder

Abstract

Utilizing recycled clay brick powder (RCBP) as alternative binder provides an effective method for reducing the amount of the clay brick waste and the need for cement, but incorporating high volume of RCBP generally causes a reduction in the performance of cement-based materials. Considering that the nano-SiO2 (NS) is commonly used and highly efficient modification materials for cement-based materials, this paper developed the NS modification to enhance the performance of cement-based materials containing RCBP. Mixing RCBP negatively impacts the hydration reaction and hydration products, but adding NS accelerates the hydration process and the formation of hydration products in RCBP paste. Adding 0.5% and 2.0% NS causes 27.3% and 43.3% increase in the cumulative heat of 30% RCBP blended paste. The mix of NS can refine the pore structure of RCBP paste, and causes a distinct reduction in the percentage of the most harmful pore. The nanoindentation results show that adding NS can raise the elasticity modulus and indentation hardness of RCBP paste. Substituting RCBP for partial cement reduces the drying shrinkage, but mixing NS increases the drying shrinkage of RCBP paste. Incorporating RCBP leads to a decline in mechanical strength, nonetheless, the mechanical strength of RCBP paste rises with the increasing dosage of NS. Adding 2.0% NS results in 44.2% and 18.8% enhancement on the 1-d and 28-day compressive strength of 30% RCBP blended paste. By optimizing the dosage of RCBP, NS and mineral admixtures, it is possible to fabricate sustainable cement-based materials exhibiting good strength and permeability resistance.