Optimization of Controlled Low Strength Material Using Spent Foundry Sand, GGBS, Fly Ash and CKD

Abstract

A Controlled low strength material (CLSM) is a highly flowable material which does not need any compaction and primarily comprises of sand, cement, water and other filler materials. The main implementation of CLSM is to replace soil backfill. The purpose of this project was to optimize a mix proportion for CLSM using various industrial by-products and to construct a material which does not have any commercial building material as its constituent. The recycling of such a waste materials will not only be having positive impact on the environment but will also lead to construction stability and economy. The mixes must possess the consistency, flowability and strength which is required for CLSM. This was achieved using trial mixing and new mixes were derived using the performance of previous pours. To investigate the properties of derived mixes tests for flowability, bleeding, density and compressive strength were performed. An effort has been made to completely replace natural coarse sand with Spent Foundry Sand (SFS). It was also found that cement and sand mixes could not provide the highly flowable and consistent mixes with high water/fines required to achieve a low strength of not more than 2 MPa at 28 days. To rectify this, binary and ternary mixes were derived by incorporating Fly Ash (FA) and Ground Granulated Blast-Furnace Slag (GGBS) with cement and sand. Since production of cement leads to high CO2 emission the cement in this project was also completely replaced with Cement Kiln Dust (CKD). The optimum pour with regards to both fresh and hardened properties was found to be made up of all the by-products without using any of the commercial building materials but very high water content was need for its generation.