Early age investigation of mechanical and electrical properties

The various strength grades concrete mixes were obtained by the water-cement ratios of 0.35, 0.45 and 0.55. The compression test and electrical resistivity measurement of the concrete mixes were conducted at the early ages. The results showed that a higher strength grade concrete mix had the larger rate value in compressive strength obtained at the early ages, and in electrical resisitivity development, and the larger elastic modulus and the higher brittleness as well. Conversely, the mechanical properties and electrical resisitivity values were smaller and the rates were lower for a lower strength grade concrete mixes. The correlation of the mechanical properties and the electrical resisitivity could be obtained then. It was difficult to measure compressive strength of a concrete mix at very early age, however, it was much easier to measure its electrical resisitivity and get the development rate. Therefore, the compressive strength could be predicted by electrical resisitivity measurement, which could record whole hydration process from casting to hardening, and reflect porosity change and mechanical properties development