Utilization of Six Sigma in Quality Improvement of Recycled Aggregates Concrete

The use of recycled demolished concrete in producing new concrete is an established method to improve sustainability through reducing the environmental impact of using virgin aggregates and through reducing construction waste. Six sigma is a set of tools and strategies for process improvement. In this paper, the six sigma DMAIC methodology is utilized to optimize the design parameters in order to improve and assure the quality of the resulting recycled aggregate concrete. The project aims to produce concrete with compressive strength of 25？MPa without using additives. Five parameters were used in the initial analysis that were reduced to three after refinement. The refined parameters are the ratio of recycled coarse aggregates, the ratio of recycled fine aggregates, and the water/cement ratio. It was concluded that the optimum values for the three parameters are 26%, 30%, and 0.5, in order. 1. Introduction Despite the many advances in technology including material technology, concrete is still the premier construction material in all types of civil engineering works, including low- and high-rise building, water retaining structures, bridges, and general infrastructure. Concrete is a manufactured product, essentially consisting of cement, aggregates, water, and possibly admixtures, additives, or agents. Among these constituents, aggregates including sand, crushed stone, or gravel form the major part by volume. Traditionally, aggregates have been readily available at economic prices and of qualities to suit all purposes. However, there has been a rising awareness to the environmental damage caused by quarries producing such primary aggregates. Therefore, countries with major cycles of demolition and construction works, such as the Arabian Gulf region, including Kuwait, are exploring ways to use recycled aggregates produced from such activities. Since its establishment in 2001, the Environment Preservation Industrial Company (EPIC) in Kuwait has been cooperating with major stakeholders in the private and government construction sectors to encourage the utilization of recycled construction materials in projects around the country. The company receives the debris from demolished civil constructions and utilizes global production technologies with standard specifications to provide the construction market with quality recycled material mainly consisting of fine and coarse recycled aggregates. In addition to the many benefits to the environmental preservation envisaged by the use of recycled aggregates in civil works, financial savings are also incurred from