Evaluating the effectiveness of coal bottom ash on the mechanical durability and microstructural characteristics of lightweight cellular concrete

Coal bottom ash (CBA), a byproduct of coal-based power plants, offers a potential route for reducing the environmental footprint of cement-based materials used to produce lightweight cellular concrete. This study experimentally investigates the influence of CBA as a partial cement replacement on the fresh, mechanical, durability, non-destructive, and microstructural properties of lightweight cellular concrete. For this purpose, six mixtures were developed at a target density of 1600 kg/m 3 . The whole experimental procedure includes a control mix, a mix having 5% silica fume (SF) only (S5CB0) and other mixes containing a constant 5% SF with 0–20% CBA replacement. Compressive strength (CS) and splitting tensile strength tests were performed along with ultrasonic pulse velocity (UPV) to assess the destructive and non-destructive properties. Furthermore, water absorption and rapid chloride permeability were measured to assess durability performance. In addition, scanning electron microscopy and energy-dispersive spectroscopy were evaluated for evaluating microstructural morphology. Based on the results, 10% CBA replacement achieved 8.85% and 10.59% increases in CS over the S5CB0 mix at 28 and 56 days, respectively. The same mix recorded UPV improvements of 11.74% and 8.52%, respectively. Furthermore, the chloride-ion charge passed decreased by 11.55% and 10.87% at 28 and 56 days, respectively, for 10% CBA replacement over the mix having 5% SF only. Microstructural observations and EDS results further supported the formation of a comparatively compact aluminosilicate-rich matrix at moderate CBA content. In addition, the 10% CBA and 5% SF combination reduced embodied CO 2 emissions by almost 8.95% relative to the S5CB0 mix. Overall, under the investigated conditions, 5% SF with 10% CBA combination provided balanced mechanical, durability, microstructural, and environmental performance.