Effect of Artificial Fly Ash Coarse Aggregate on Bulk Density, Water Absorption, and Compressive Strength of Lightweight Concrete

In recent years, lightweight concrete (LWC) has been extensively used in construction due to its benefits for reducing static loads, insulating against sound and heat, and so on. The LWC is typically produced by using natural and/or artificial lightweight aggregates (LWA). In this study, artificial fly ash coarse aggregate (AFCA) was produced through the cold bonding technique from a mixture of fly ash, Portland cement, and sodium silicate (Na2SiO3) as an activator. This study aims to assess the effect of AFCA on bulk density, water absorption, and compressive strength of the LWC. The AFCA was added to the concrete mixture by substituting 0, 50, and 100% by the volume of LWA. Expanded clay aggregate (ECA) as an LWA was also added to the reference concrete mixture for comparison purpose. Results showed that the replacement of ECA with AFCA gave positive results in which the compressive strength was increased from 17.0 to 47.7% and water absorption was decreased from 16.2 to 36.2% compared with those of LWC with ECA. Although the bulk density of concrete with AFCA was slightly higher than that of LWC with ECA, its value was still less than 1800 kg/m3 for all the mixtures considered as the LWC. In summary, the AFCA in this study could be used as the LWA to produce the LWC with the improved compressive strength and reduced water absorption.