Feasibility of making aircrete without autoclave using indigenous materials in Bangladesh

Abstract

This study was aimed to investigate the feasibility of production of lightweight concrete (aircrete) in Bangladesh without autoclaving and using indigenous materials. It demonstrated the feasibility and sequential approach for producing Aircrete using acquiescent technology of Bangladesh. Initially the study gives a thorough search for local materials and appropriate production technique. Bangladesh, being a tertiary-geological-featured country, possesses no natural lightweight concrete that could be incorporated in this research. However, relatively suitable indigenous and easily available foreign material options were identified and utilized in the study. It was found that a binder (OPC or PCC), local sand and Sylhet sand, a foaming agent preferably aluminium as nonmechanized foam generator were the best components for producing the aircrete. However, lime is used to enhance performance of aluminium and admixtures if required were applied in this study. Feasibility study integrating a series of materials revealed that the optimistic notion towards the production of Aircrete (density less than 1000 kg/m3) in Bangladesh. Range of ingredient contents was identified through this study. The typical zone for density less than 900 kg/m3 and strength greater than 1 MPa was identified by the research. In this condition research gave the best solution with the mix design proportion that water and cement content should be above 470 kg/m3 and 485 kg/m3 respectively. Aluminum should be mixed with 2% of cement content. However the maximum strength could not be achieved more than 1.4 MPa. Major problem associated with the research that water leakage in the mold, accommodation of the expanded concrete in the mold, loss of hydration moisture, etc. However it shows that Aircrete give low strength due to high water-cement ratio, low cementation index and foamy honey comb structure. From the results, it was seen that density decreased with increased cement and water content, whereas compressive strength increased with increased cement but decreased water content, thereby indicating a conflicting relation. Consequently, a number of interpretable charts were constructed to correlate density and compressive strength with material contents. However, although target density range was achieved, strength criteria were insufficient for practical application. This study was an approach for producing Aircrete in Bangladesh. The outcome and recommendations may provide future scope for the next researchers interested in this field. Future researcher can continue their research using the experiment results with introducing autoclaving with normal technique, with confined or unconfined condition.