Abstract This study investigated lightweight aggregates (LWAs) production using blends of waste coal combustion ash (WCCA) and soda-lime waste glass (WG), with a focus on understanding how the chemical and mineralogical composition of WCCA influences sintering behavior and LWA performance. LWAs were fabricated at a sintering temperature of 1100 °C using six types of WCCA with varying mass contents of Fe 2 O 3 , loss on ignition (LOI), amorphous phase, and mineral phases. The WG was used with contents ranging from 0 to 50 wt%. X-ray computed tomography (X-CT) and physical/mechanical testing showed that LWAs produced with 50% WG exhibited improved strength-to-specific gravity due to fewer large voids and higher solid integrity. However, at lower WG contents (25–40%), successful LWA formation was only achieved when the WCCA had favorable compositional traits, specifically, higher Fe 2 O 3 , LOI, amorphous content, and lower high-melting-point minerals such as mullite. These conditions promoted partial melting, enhanced gas generation, and facilitated iron oxide reduction during sintering, all of which were essential for producing structurally stable and well-bloated LWAs. On the other hand, dissolution and pH measurements revealed that WG contributed minimally to chemical activation of WCCA prior to sintering but acts as a binder during sintering. The findings demonstrated that the suitability of WCCA for WCCA/WG-based LWAs production is strongly governed by WCCA melt-forming and iron oxide reduction potential, which is controlled by its chemical and mineralogical composition. Understanding the effect of WCCA composition on sintering was found essential for optimizing WCCA/WG blend ratios and provide guidance for the future scale-up WCCA/WG-based LWAs production using WCCA and WG industrial byproducts.
Abstract Fly ash-based geopolymers exhibit excellent mechanical performance under ambient conditions; however, their dimensional stability and residual strength can deteriorate substantially at elevated temperatures. This study investigates the effects of fly ash particle size and heat-expansive additives, including densified silica fume, raw perlite, and andalusite, on the thermomechanical performance, volumetric stability, and residual compressive strength of potassium-activated fly ash geopolymers exposed to standard fire heating for 0.5 and 2 h, followed by either natural cooling or water spraying to induce thermal shock. Finer fly ash increased geopolymerisation, and ambient strength by 38.3%, but increased thermal shrinkage and reduced early thermomechanical performance due to restricted vapour escape. Silica fume increased porosity at room temperature by 15.7%, induced expansion at 0.5 h, and substantially reduced thermal contraction at 2 h. It also achieved a residual compressive strength of 157% relative to the reference at 2h, attributed to its high content of unreacted and partially reacted amorphous silica. Andalusite significantly improved thermomechanical performance at 0.5 h by 72.8%, owing to its high thermal stability. Thermal shock generally arrested shrinkage and improved strength retention, while causing greater expansion in silica-rich mixes due to gel rehydration. The findings revealed strong relationships between fly ash particle size, initial porosity, amorphous silica content, thermal shrinkage, residual mechanical performance, and the potential of thermal-expansive additives under fire exposure.
To reduce the consumption of natural aggregates, biomass bamboo aggregate concrete hollow blocks (BACHBs) were developed for light-weight filled wall. Bamboo, a fast-growing renewable biomass, was processed into lightweight aggregates and used to partially replace crushed stone, enabling the production of a biomass-based masonry material. Epoxy mortar (EM) was employed as a surface modification method to enhance interfacial performance. BACHBs incorporating different BA replacement ratios (0–40
The dynamic tensile behavior of ordinary and mass concrete was investigated under combined static preloading and seismic strain rates through 222 specimens tested in direct tension and four-point bending. Strain rates ranged from quasi-static to 10^-2 s ^-1 , and preloading levels from 0 to 75 10^-4 and 10^-2 s ^-1 , respectively. Preloading consistently enhanced the DIF, adding approximately 0.05 units per 25
Temperature-dependent concrete damage-plasticity concept has been often implemented in structural fire engineering, despite the lack of experimental calibration data. However, when concrete, damaged under service or extreme loads, gets exposed to elevated temperatures it suffers from internal stress-concentration and weakened Interfacial Transition Zones (ITZ), which severely affects its constitutive behaviours. Despite this vulnerability, experimental data observing the constitutive behaviours of pre-damaged concrete at elevated temperatures remain limited. Current experimental study explores the dynamic interactions between prior damage and nature of sustained loading during exposure, both compressive and tensile, on the residual softening behaviour and damage evolution. Displacement-controlled cyclic compression and direct tensile tests reveal that strength attributes alone are insufficient indicators to concrete’s residual performance at elevated temperatures. The experimentally derived evolutions under compression and tension provide crucial insights towards the development of advanced material models, to capture post-fire behaviour of pre-damaged concrete in crushing or cracking failures.
