DETERMINATION OF SELECTED PROPERTIES OF SELF COMPACTING LATERISED CONCRETE PRODUCED USING PLANTAIN LEAF ASH.

Abstract

For the past three decades, concrete has been one of the most demanded materials in the construction industry globally; the case in Nigeria is the same and the demand is still on the increase. However, the need to produce highly durable concrete with reduced environmental hazards and minimal requirement for expertise has led to the development of self-compacting concrete, a concrete that is highly flowable and consolidates under its own weight without the need for external vibration. This research focuses on determining some selected properties of self-compacting laterised concrete produced using plantain leaf ash at varying percentages both in the wet and hardened state. The selected properties in this research include: passing ability, filling ability, setting time, particle size distribution, specific gravity, Atterberg limit, oxide composition, compressive strength, split tensile strength and flexural strength. In the production of this self-compacting concrete, 200g of conplast SP430 was mixed with each of the concrete specimen as the chemical admixture. One hundred and twenty (120) concrete cubes of size 150mm x 150mm x 150mm, twenty seven (27) concrete cylinders of size 100mm x 200mm and twenty seven (27) concrete beams of size 100mm x 500mm were cast for the compressive strength, split tensile strength and flexural strength respectively. These concrete specimens were demoulded after 24 hours and cured in a curing tank for 7 days and 28 days. After curing, the concrete was crushed for the compressive strength, split tensile strength and flexural strength using the universal testing machine (UTM). L-box and V-funnel were used to determine the passing ability and filling ability of the concrete respectively in accordance with the specifications of European Federation of National Associations Representing for Concrete, EFNARC (2002). The study showed that all values gotten for the filling ability fall within the range of 6 to 12 seconds and the values gotten for the passing ability fall within the range of 0.8 to 1.0 blocking ratio as specified by EFNARC (2002). Also, the initial setting time for the OPC and 5%, 10% and 15% replacement with PLA gives 114 minutes, 200 minutes, 175 minutes and 147 minutes respectively while the final setting time gives 452 minutes, 695 minutes, 630 minutes and 602 minutes respectively. The compressive strength of the control concrete was 18.3 N/mm2 while the optimum dosage of PLA was 15% which gives a compressive strength of 13.3 N/mm2. However, it was discovered that the control concrete gives a split tensile strength value of 1.5 N/mm2 while the optimum dosage of PLA was 10% which gives 1.7 N/mm2. In addition, replacement of sand with laterite leads to a decrease in the split tensile strength. Furthermore, the control concrete gives a flexural strength of 5.8 N/mm2 while the value when cement is replaced with plantain leaf ash at 5% and 10% remained the same at 6.3 N/mm2 respectively. The research also revealed that replacing sand with laterite leads to a decrease in the flexural strength. The research has shown that PLA can be used as partial replacement for cement in lightweight aggregate concrete production.