Use of Construction and Demolition Waste as Replacement of Coarse Aggregate in Concrete

Abstract

Nowadays, the use of concrete in infrastructure project activities are in large quantity. So the consumption of concrete ingredients is increased. As we know that aggregate play a very important role in concrete which occupies the largest volume of about 60-75% of total concrete volume. Due to that use of natural aggregates demands are increasing day by day. To overcome this problem, use of recycled aggregates can be replaced with natural aggregates by improving its basic properties. Recycled aggregates are the aggregates produced from the processing of previously used construction materials such as construction and demolished waste of structural buildings, tested specimens from a laboratory, concrete from ready-mix concrete plants and pre-casting units are some sources of recycled aggregate. As it is found from the literature that the recycled aggregates used for non-structural elements like paver blocks, concrete blocks, kerbs and grass blocks. In present work, the recycled aggregate is procured from “Ahmdavad Enviro Projects Pvt. Ltd.”, for mixture proportioning of concrete. Demolition waste consists of concrete waste which includes only aggregates as well as least amount of brickbats. Experimental investigation has been done with natural aggregates to find out the physical properties of recycled aggregates with different proportions such as 0%, 20%, 40%, 60%, 80% and 100%. Physical properties such as fineness modulus, specific gravity, water absorption, moisture content, bulk density and aggregate impact value of recycled aggregate are investigated. It was observed the recycled aggregate absorbed more water compared to natural aggregate. Mix design of M25 grade of concrete is developed for natural aggregate (100 %) and recycled aggregate (100 %). At the age of 7 days, it was found that the compressive strength of recycled aggregate concrete was less as compared to natural aggregate. For the improvement of compressive strength of recycled aggregate concrete, cement is replaced with Metakaolin and GGBS by 5% to 10% and 15% to 25% respectively. Final mix design is developed by replacing cement with Metakaolin 10% and GGBS 15% for recycled aggregates concrete. The results of mechanical and durability properties are compared. The experimental results showed that recycled aggregates concrete has increased in compressive strength but decreased in other mechanical properties compare to natural aggregates concrete. The water penetration for recycled aggregates concrete has increased compared to natural aggregate concrete. The other durability properties were found almost similar for both recycled aggregates concrete and natural aggregates concrete. The further investigation was also carried out for the RC elements such as RC beams, RC columns and RC slabs for both recycled aggregates concrete and natural aggregates concrete. RC beam was tested for two-point load and results showed that the load carrying capacity is reduced with 9.43% in recycled aggregates concrete compare to natural aggregates concrete. RC column was tested for axial compressive load and investigation results observed that the load carrying capacity is increased with 7.14% in recycled aggregates concrete compare to natural aggregates concrete. RC slab was tested for punching shear test and experimental results showed that the load carrying capacity is decreased by 2.67% in recycled aggregates concrete compare to natural aggregates concrete. The overall result showed that the improving the mechanical and durability properties of recycled aggregate concrete by cementitious material in concrete. Recycled aggregates physical properties may vary from source to source. In the present investigation, the age of recycled aggregates was less than one year. The experimental investigation results showed that the recycled aggregates might be used in structural members also.