Effects on Compressive and Tensile Strength of Concrete by Replacement of Natural Aggregates with various Percentages of Recycled Aggregates

Abstract

Recycled aggregate concrete is required owing to environmental conservation and actual consumption of resources. In the construction industry, for the manufacturing of concrete the demand for replacement of ordinary aggregates by recycled aggregates has increased worldwide due to the large quantity of structure and destruction waste. The objectives of this research is to evaluate the effects of strength of concrete by replacing the normal crush with different percentages such as 25%, 50%, 75% and 100% of recycled aggregates. To conduct this study, a total of 120 cylinders (60 for compression and 60 for splitting cylinder test) are casted with mixing ratio of 1:1.9:3.8 and water to cement ratio of 0.59 while curing is carried out for 7, 14, 21 and 28 days. Numerous laboratory tests are performed like workability test, compression tests and splitting tensile strength tests, to check and compare effects of the recycled aggregate concrete with reference mix M1 (0%RA). The results illustrate that the workability of concrete decreases when the quantity of recycled aggregates are increased due to more water absorbing capacity. Further, it is also perceived that the compressive strength of concrete is decreased by 3.8%, 5.7%, 12.9%, and 15.8% respectively at 28 days of curing by substituting coarse aggregates with various percentages such as 25%, 50%, 75% and 100% of recycled aggregates as compared to reference concrete mix M1 (0% RA). Similarly, splitting tensile strength is also decreased when the quantity of recycled aggregates in ordinary concrete is increased. Moreover, this reduction in workability and strength of concrete is due to more water absorbing capacity of recycled aggregates. Hence it is concluded from the research that up to 25% replacement of natural aggregate with recycled aggregates, the recycled aggregate concrete is usually preferable to reduce the cost of construction as well as improve the environmental pollution issues. It is also observed that the splitting tensile strength of a concrete batch should vary between 9 – 11% of its respective compressive strength test results.