Effect of fiber types on the electrical properties of fiber reinforced concrete

Using fibers in concrete, has been recognized as a practical method to improve concrete properties such as reduction in crack development and higher resistance against impact and abrasion. Dry cementitious material exhibits very high electrical resistivity. However, fibers can significantly decrease the electrical resistivity of concrete which affects its insulating nature and has negative effects on concrete properties such as durability and also in special cases such as rail road ties production. In this paper the effect of steel, glass, and nylon fiber on the electrical properties of Fiber Reinforced Concrete (FRC) is investigated. Six different fiber volume fractions (Vf) (0.10% vol., 0.25% vol., 0.50% vol., 0.75% vol., 1.00% vol., 1.50% vol.) and several water-tocement ratios (w/c) were considered as the main variables in the present study. In order to test the electrical properties of FRC, 100 mm×200 mm cylinders were casted, cured and tested. The four point technique was used for measuring the surface electrical resistivity of concrete after curing in water for 3, 7, 28, and 44 days. Additionally, the compressive strength of each specimen was determined experimentally using the Compression Test Machine. The results revealed that the electrical resistivity of FRC decreases with an increase in fiber content but different types of fibers have different electrical effects on concrete. The effects of different volume fractions of three fiber types, together with different concrete mix proportions are presented and discussed.