Study on the physical and mechanical properties of Alkali-Activated concrete bricks

Alkali-activated concrete (AAC) has shown high potential as a replacement for ordinary Portland cement concrete (OPCC). It has been found that fresh AAC is usually dry and difficult to control during the casting process, as well as having flash setting issues. In light of the lack of a final form for the use of AAC in construction, there is a need to discover applications that benefit from the advantages of AAC while also being able to deal with its drawbacks. This paper will focus on taking advantage of AAC's defects by using it in a nonstructural application that does not require high-workability concrete, such as producing bricks. Waste from the iron industry was used as the main component for producing the AAC bricks in order to reduce the environmental impact, reduce the cost, and save large quantities of cement and natural aggregates consumed by the brick industry. Ground granulated blast furnace slag (GGBFS) and electric arc furnace slag (EAFS) were substituted for cement and aggregates, mixed along with an alkaline solution and superplasticizer. AAC bricks were produced in the same way as normal concrete bricks. The physical and mechanical properties studied were compressive strength, water absorption, bulk density, efflorescence, and drying shrinkage. Six parameters were considered throughout this investigation. The effects of binder content, cement replacement ratio, alkaline-to-binder ratio, sodium silicate/ sodium hydroxide mass ratio, sodium hydroxide molarity, and compaction pressure. The results showed that compared to ordinary bricks, AAC bricks provided high compressive strength up to 92 MPa, up to 54% less water absorption, a density of more than 2.8 t/m3, and a higher drying shrinkage up to 0.002 mm. Furthermore, no signs of efflorescence or salts appeared on the bricks.