Indian Journal of Science and Technology

Abstract

Objective: To study the effect of the water to cement ratio (w/c) on 222Rn diffusion, gamma attenuation, neutron attenuation and Ultra-sonic Pulse Velocity (UPV) for local Portland concrete. Methods: The 222Rn diffusion coefficient was measured by putting a cubic concrete sample between two sealed compartments. The linear attenuation coefficients for g-rays from 137Cs and 60Co sources were measured using broad beam experimental setup. Neutron attenuation ratio was calculated by using Am-Be source with neutron flux 107 (n.cm2 .s-1). The Ultrasonic-Pulse Velocities (UPV) (m.s-1) were measured for all the faces of cubic concrete samples. Findings: Results showed that the effect of increasing w/c on linear attenuation coefficients of g-rays and neutron attenuation ratio were not significant and all results were within the uncertainties range. However, in the case of (UPV), the results showed linear relationship with negative slope. In addition, the effective diffusion coefficients De of 222Rn in concrete samples increased with increasing (w/c) (on the opposite of the behavior of (UPV) and the value of De changed from (3.6±0.39) ´ 10-10 m2 .s-1 for w/c = 0.35 to (11.0±0.7) ´10-10 m2 .s-1 for w/c = 0.6. Application/ Improvements: This study establishes a reliable test and evaluating procedure for determination of D and De by measuring the (UPV) for cubic Portland concrete sample.

Keywords: 222Rn Diffusion, Gamma Attenuation, Neutron Attenuation, (UPV), (w/c)