Aref A. Abadel

Excessive use of natural resources and environmental concerns are key issues motivating the recycling of waste materials in the construction industry to minimize landfill problems. Free cement binders such alkali-activated binders have emerged as a prospective alternative to ordinary Portland cement, wherein diverse industrial, agriculture, and by-product waste materials have been converted as valuable spin-offs. Annually, tens of millions tons of red brick wastes are generated, which leads to several environmental problems. Thus, waste red brick powder (WRBP) was used as binder or a fine aggregate (silica sand) substitute to prepare some new types of alkali-activated mortars (AAMs). These mortars contained ground blast furnace slag (GGBFS) and metakaolin (MK) with various levels of WRBP (0, 15, 30, and 45%) as a substitute for silica sand. The prepared AAMs were cured at 300 °C, 600 °C, and ambient temperature. All the specimens were tested to determine the effects of various WRBP contents on the workability, strengths, and microstructures of the designed AAMs. The workability of the fresh AAMs was considerably dropped due to the incorporation of WRBP as binary binder or fine aggregate replacement. In addition, AAM containing 15% of WRBP as GGBFS and MK replacement displayed a significant improvement (by 30.7%) in the strength performance. However, the increasing content of WRBP to 30% and 45% significantly led to a decrease in compressive strength from 49.9 MPa to 44.7 and 34.2 MPa, respectively. Overall, the mortars’ strength was increased with the increase in WRBP contents from 0 to 45% as sand substitute. Conversely, the mortars strength was reduced with the increase in curing temperatures. The microstructure analyses of the studied mortars revealed an appreciable enhancement of the geopolymerization process, gels formulation, and surface morphology, leading to an improvement in their compressive and flexural strength characteristics. It was asserted that high-performance mortars with customized engineering properties can be designed via the inclusion of WRBP into alkali-activated MK-GGBFS mixes.

Carbon dioxide emissions are one of the problems that arouses the interest of scientists because of their harmful effects on the environment and climate. The construction sector, particularly the cement industry, is a significant source of CO2. On the other hand, solid waste constitutes a major problem facing governments due to the difficulty of decomposing it and the fact that it requires large areas for landfill. Among these wastes are LCD waste glass (WG) and used rope waste. Therefore, reusing these wastes, for example, in concrete technology, is a promising solution to reduce their environmental impact. Limited studies have dealt with the simultaneous utilization of glass waste as a substitute for cement and rope waste (nylon) fiber (WRF). Therefore, this study aimed to partially replace cement with WG with the addition of rope waste as fibers. Thirteen mixtures were poured: a reference mixture (without replacement or addition) and three other groups containing WG and WRF in proportions of 5, 15 and 25% by cement weight and 0.25, 0.5 and 0.75% by mortar weight, respectively. Flow rate, compression strength, flexural strength, dry density, water absorption, dynamic modulus of elasticity, ultrasonic pulse velocity and electrical resistivity were tested. The results indicate that the best ratio for replacing cement with WG without fibers was 5% of the weight of cement. However, using WRF increased the amount of glass replacement to 25%, with an improvement in strength and durability characteristics.