Study Of Recycled Aggregate Concrete

This thesis presents experimental studies on the physical properties, mechanical properties and durability of coarse recycled concrete aggregate and recycled aggregate concrete. Concretes having water/binder ratios of 0.26, 0.40 and 0.60 were crushed manually at ages 28 days to serve as sources of aggregates for new concretes. The properties of the recycled aggregates and of the new concretes made from them, with 30% and 100% of aggregate replacements, were tested. The tests on the three different types of recycled concrete aggregates comprised the study of the physical properties such as apparent density, gradation, water absorption and particle shape, mechanical properties such as aggregate crushing value. The tests on recycled concrete comprised the studies of the workability, physical properties, mechanical properties and chloride diffusivity. Based on the research and results presented in this paper, we can draw the conclusion that the recycled aggregate concrete could be used for pilot and long scale buildings where the use of recycled aggregate concrete can be estimated as more economic and friendlier to the environment.The recycled concrete aggregates derived from three types of original concretes of which strengths were different in order to distinguish between properties that might be related to strength of original concrete. The properties of the recycled coarse aggregates derived from the crushed concretes were found to be significantly different from those of the natural aggregate. Moreover, substantial differences in physical properties and strength were found between the recycled aggregates derived from the low strength concrete, the medium strength concrete and the high strength concrete. Partly as a result of residual cement mortar attached to recycled concrete aggregate particles, marginal lower density, higher water absorption value, higher aggregate crushing value and lower robustness value are observed compared to the natural aggregate. test results indicated that the strength of original concrete primarily determines physical and mechanical properties of recycled concrete. With the enhancement of the strength of original concrete, the water absorption rate and aggregate crushing value of recycled concrete aggregate increased, however, the apparent density and robustness value decreased. It appeared that there was no significant change in the grading of the three types of aggregates despite the differences in the strengths of the concretes they were made from.Six different mixes were employed to examine the influence of incorporating coarse...