Anchorage Bond Strength Characteristics of Lateritic Concrete with Laterite Aggregates and Palm Kernel Fibres

Abstract

Globally, sources of natural aggregate such as sand and quarry dust as fine aggregate, and crushed granite, sandstone, dolomite and basalt as coarse aggregate for concrete are fast getting depleted or exhausted. There is therefore the need to look for alternative sources to replace them. Laterite is abundant in tropical regions of the world and is a potential alternative to conventional concrete aggregates. Palm kernel fibre is also a natural and renewable material that is found to be good fibre reinforcement to improve cracking resistance of concrete. This study assessed the anchorage bond, compressive and tensile strength properties of concrete using lateritic aggregates mixed with palm kernel fibre (PKF). The compressive, bond and tensile (split cylinder and modulus of rupture) strengths of lateritic concrete were evaluated experimentally through crushing, tensile and anchorage bond tests. The same mix for characteristic strength of 25N/mm² concrete, the compressive strength was found to be 7.42N/mm² for lateritic concrete without PKF representing 29.68% of the 25N/mm2 concrete strength. The addition of palm kernel fibre to the lateritic concrete further decreased the compressive strength of the resulting concrete with increasing PKF to 1.90N/mm2 at 20% palm kernel fibre, causing 74.34% reduction in the compressive strength. The rate of reduction of the compressive strength was sharp initially for small amounts of the palm kernel fibre but approached a constant value at 15% and 20% additions of palm kernel fibre.  The tensile strength was 9.59% of the compressive strength showing a similar relationship with the compressive strength of conventional concrete. Also bond strength showed decreasing strength with increasing PKF addition except that the reduction was gradual compared to the compressive strength. Thus 2.31N/mm², 2.04N/mm², 2.18N/mm², 1.87N/mm² and 1.27N/mm² bond strength for 0%, 5%, 10%, 15% and 20% PKF addition respectively. A pull-out bond failure mechanism was observed to occur at or around the middle of the test discontinuous bar specimens while modulus of rupture observed to correlate with the bond strength value representing 84.79% of the bond strength of the 0% PKF specimen.