Performance of Concrete Containing Locust Bean Pod Ash and Metakaolin as Cement Replacement

Locust bean pod (LBP) is a pozzolanic African agricultural waste originated from locust bean tree (Parkia biglobosa). This study presents strength and extreme pH Resistance of locust bean pod ash (LBPA) concrete containing metakaolin (MK) as cement replacement material (control, OPC-LBPA, and OPC-LBPA-MK). The LBP and kaolin were thermally digested into LPB ash (LBPA) and MK. Ordinary Portland cement in concrete was replaced with LBPA by mass. The workability and setting times were determined. The strength and extreme pH resistance (HCl and H2SO4 acids, and sulphate) were assessed. Properties of the concrete were statistically analyzed and optimized using response surface methodology (RSM). As the LBPA content increased, the workability was reduced. Further, the 5% LPBA replacement showed the greatest improvement for the binary system while combined 20% (5% LBPA and 15% MK) replacement level gave the best performance for the ternary system at 90 days. Additionally, both blends improved the performance of concrete against acids and sulphate. The study concludes that up to 35% of OPC could be replaced using 20% of LBPA and 15% MK in a ternary system for structural concrete. LBPA along with MK should be utilized in the production of structural concrete for low-cost construction.