Effect of sawdust ash and laterite on the electrical resistivity of concrete

Abstract

This study is an experimental research aimed at evaluating the electrical resistivity of concrete containing laterite and sawdust ash (SDA). Laterite was used to partially replace the sand in concrete while SDA partially replaced cement as a supplementary cementitious material. Cylindrical samples of Ø100 by 200 mm were used to evaluate the singular and combined influences of water-binder ratio, SDA and laterite on the electrical resistivity of concrete as a measure of durability. The sawdust ash content of 0, 10, 20 and 30% by weight of cement was considered while an optimum 30 % laterite content was examined and water-binder ratios of 0.35, 0.50 and 0.65. Additionally, some samples were cured in 1 %, 3 % and 5 % of sodium chloride salt (NaCl) to simulate the marine environment. The electrical resistivity test was conducted using the four-electrode method (Wenner’s Method) in accordance with ASTM C1202. The results of the investigations revealed that the resistivity of concrete generally increases with age at all replacement levels with optimum performance at a water-binder ratio of 0.50. Also, the results show that an increase in the sawdust ash content reduces the resistivity of concrete while the addition of laterite at 30% increases the electrical resistivity of concrete at increased water content. Chloride ion exposure generally reduces the ER of concrete while laterite reduces the impact of the chloride ion.

Keywords

• laterite
• sawdust ash
• electrical resistivity
• durability
• water-cement ratio
• laterised concrete