Effect of water to cement ratio (w/c) and age on the ultrasonic and electrical Non-Destructive Testing (NDT) of plain and chemical admixtured concrete

Abstract

The ultrasonic velocity, the electrical resistivity and the compressive strength of plain (N), accelerating admixture (A), high range water reducing admixture (H), and retarder admixture (R) concrete samples of 0.35, 0.42, 0.55 and 0.6 w/c ratios were measured, The effect of concrete age on the samples with 0.42 water to cement (w/c) ratio were studied. The results show that, the ultrasonic velocity, the electrical resistivity and the compressive strength are inversely proportional to the w/c ratio for all samples and at the same w/c ratio the values of these parameters for the high range water reducing admixture (H) concrete, are relatively higher than that of the accelerating admixture (A) concrete then the Plain (N) concrete, then, retarder admixture (R) concrete. \xa0For the samples with different ages, the results show that, the ultrasonic velocity, the electrical resistivity and the compressive strength increase rapidly at first 7 days, after that, the increment slows down significantly after 28 day, and at the same age, the values of theses parameters of the accelerating admixture concrete sample (A4) are higher than that of the other samples {high range water reducing concrete (H4), plain concrete (N4) - retarded concrete (R4)} The destructive compressive strength was correlated to the nondestructive ultrasonic velocity and electrical resistivity measurements. Linear relationships between the compressive strength and either the ultrasonic velocity or the electrical resistivity were obtained. The results were attributed to the hardening and the microstructure development in the different concrete samples