Investigating the fresh and mechanical properties of wood sawdust-modified lightweight geopolymer concrete

Geopolymer concrete has developed as a potential alternative to ordinary Portland cement-based concrete, wherein various industrial by-products have been converted as beneficial spin-offs. Apart from appropriate compressive strength in the construction sector worldwide, the durability, sound absorption, thermal conductivity, and weight of concrete are also major concerns. Lightweight geopolymer concretes have gained attention because of their superior strength, durability, lower environmental impact, and sustainable characteristics. In this view, the current study examined the feasibility of using sawdust as a natural fine and coarse aggregate substitution in fly ash (FA)-granulated blast furnace slag (GBFS) based geopolymer concrete. Four mixes with a different percentage of sawdust (25, 50, 75, and 100) substituting natural aggregate were designed to examine the effects of sawdust on fresh and hardened features of geopolymer concrete compared to those conventional FA-GBFS-based geopolymer concrete with natural aggregate. Sodium silicate (NS) and sodium hydroxide (NH) (with NS/NH ratio of 0.75) were utilized to dissolve the alumina silicate from FA and GBFS. Informational models were developed using an experimental dataset to estimate the compressive strength of geopolymer concrete mix designs. Besides, using the weight of the developed network, a global sensitivity (GS) analysis was developed to identify the sensitivity of compressive strength to the waste sawdust content. Test results confirmed that by substituting natural aggregate with 100% sawdust, there was around a 35% decrease in compressive strength. Nevertheless, the sound absorption coefficient was increased by an average of 38% in frequencies range between 1800 and 2500 HZ, and thermal conductivity decreased by around 4.5 times once the natural aggregate was substituted by 100% sawdust.