The socio-economic growth of a nation depends heavily on the availability of adequate infrastructure, which relies on essential materials like river sand (RS) and cement. However, the rising demand for RS, combined with its excessive extraction causing ecological damage, and its increasing cost, has raised significant concerns. At the same time, the production of cement contributes significantly to environmental damage, especially through CO2 emissions. In this scenario geopolymer technology has emerged as a sustainable alternative to cement, offering environmental benefits and reducing the carbon footprint of construction materials. This study investigates the impact of replacing RS with copper slag (CS) and laterite soil (LS) in geopolymer mortar (GM) on key properties such as setting time, flowability, compressive strength, and microstructure. The results showed that as LS content increased, setting time and flowability decreased considerably, while increasing CS content caused a reduction in these values. Unlike the other observed parameters, the compressive strength values showed no distinct upward or downward trend. Moreover, the microstructural analysis, including SEM, EDS, XRD, FTIR, TGA and BET, provided valuable insights to support the observed results across various mix designs. Overall, the findings highlight that optimised binary blends of CS, LS and RS not only improved the compressive strength but also enhanced the microstructural characteristics of geopolymer mortar, reinforcing their potential as sustainable and high-performance alternatives to conventional fine aggregates.

In order to enhance the application of epoxy mortar in pavement repair engineering, an epoxy -based repair material with short molding time, easy fabrication, high early strength and good durability was developed. In the past, the fillers of epoxy mortar were mainly fly ash and silica fume. In this paper used loess (LS) and river sand (RS) which were lower cost and more readily available, mixed with epoxy resin to make a new epoxy mortar system. The influence of epoxy resin mass fraction (20%,25%,30%), filler type (LS, RS), and LS -to -RS ratio (2:1,1:1,1:2) on the mechanical properties and durability of the epoxy mortar were investigated. It was observed that the early compressive strength of the specimens increased significantly with the increase of the proportion of epoxy resin in the mixture, reaching 49.2 MPa after 2 h of curing. Moreover, when the mass fraction of epoxy resin increased from 20% to 30%, the flexural strength increased by more than 20% after curing for 2 h. Additionally, compared to single filler, mortar containing both LS and RS exhibited superior durability. Unlike the specimens of the all -river sand group L0, which showed a 40% to 60% decrease in mechanical properties in sulfate and chloride saline solutions, almost no loss of strength occurred in the L1R1 group. This phenomenon can be explained by the findings from SEM and MIP tests that the L1R1 group has a more compact pore structure compared to the L0 group.