Investigation of Blended Oil Palm Nut-Husk Ash and Over-Burnt Bricks Precast Concrete for Wall Cladding

Abstract

The suitability of Oil palm nut-husk ash (OPNHA) and crushed over-burnt bricks (COBB) was investigated for wall cladding. A mathematical model was developed and used to optimize the mix proportion that  produces the maximum strength of OPNHA/COBB concrete for wall cladding, using Scheffe's simplex lattice approach. The model formulated compares favourably with the experimental data. It also satisfies the T and F - statistics. The optimum value of strength predicted by this model is 33.41996N/mm², at a mix ratio of 1:0:2:4:0.4 of ordinary Portland cement, OPNHA, river sand, COBB and water-cement ratio; followed by 30.84N/mm2 with 0.6:0.4:3:6:0.6 ratios . Three mixtures (optimum, medium and low strength) were selected for other tests viz: impact values, water absorption and thermal properties. The results indicate that mixtures with optimum strength showed greatest resistance to impact load, followed by that with medium and low strength. Water absorption for optimum, medium and low strength were 1.51%, 2.24% and 0.56%, respectively. Thermal conductivity of 0.5017W/mk, 0.339W/mk and 0.394W/mk were recorded for the optimum, medium and low strength mixtures. The thermal resistivity were 1.992mk/W, 2.946mk/W and 2.538mk/W for the optimum, medium and low strength mixtures. Specific heat capacity of 1.134W/kgk, 0.84W/kgk and 0.9115W/kgk and thermal diffusivity of 0.00879m2/s, 0.00989m2/s and 0.00948m2/s were observed for the optimum, medium and low strength mixtures. Thermal absorptivity values were 0.146mm-1, 0.138mm-1 and 0.141mm-1 for the optimum, medium and low strength mixtures, respectively. The values met the set standards (ACI 122R-02 2002, ASHRAE, 2009 and Building and construction Authority, 2010).

Keywords: Compressive strength, precast OPNHA concrete, Mix design, Mathematical model, Optimization, Wall cladding.