Construction of dams by using roller compacted concrete (RCC) is a relatively recent technology which has increasingly developed in the past few years. With regard to various horizontal lift joint in the body of RCC dams and in order to increase the safety factor in the design, the experimental investigation was conducted on the basis of improving bond strength in RCC by using interface cement grout and imparting changes in normal pressure.
RCC samples were constructed in two layers with maximum aggregate size of 25 mm, type I cement of Isfahan plant and Khash pozzulan. On the whole, in different conditions of using grout with w/c ratio of 0.5, 0.75, and 1 as well as no grout condition, the first stage of bond strength tests in normal pressure (0,5,10, and 15 kg/cm2) by using the designed machine in this study and the second stage tests were conducted in normal pressure (20,25,30,35, and 40 kg/cm2) by using stone direct shear machine. From the sum of 250 made samples, the results of bond strength and compressive strength in 7, 28, and 90 days in the first stage, and the results of maximum bond strength and residual bond strength in 28 days in second stage have been obtained. On the basis of the results obtained, bond strength parameters have been obtained and analyzed.
The results of this study indicated that the Mohr coulomb criterion shows the upward tend of bond strength with an increase in normal pressure very well, and by increasing the normal pressure from the first stage to the second stage, interface cohesion decreases and the interface angle increases. Also, by using grout between layers paves, the way for an increase in bond strength compared to the no grout condition, and there will be a decrease in bond strength with an increase in w/c ratio of grout. In this case, changes in cohesion parameter are in phase with changes in bond strength while to sensible changes in interface conditions are evident on the interface friction angle.
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