Investigation on the Properties of Porous Concrete Using Recycled Concrete Aggregate as Partial Replacement of Coarse Aggregate

Infrastructure department is the second-largest economic sector in Ethiopia after the agriculture industry. Due to expansion in this infrastructure and increased development of the country, most of the places are covered either by impermeable cement concrete or bitumen surfaces that blocks the percolation of water from rainfall or any other sources. It is significantly desired to produce eco-friendly concrete to reduce environmental issues for sustainable development. One of these concretes is porous concrete made up of zero fine aggregate, creating a significant pore that allows the concrete to be water permeable. However, this type of concrete has not been considered in the Ethiopian market. Similarly, the demand for natural coarse aggregate is still high whereas natural resources are depleting. Hence, recycling of construction and demotion wastes in to secondary concreting materials is a sustainable solution that reduces the gap between demand and supply of fresh aggregate as well as waste disposal land. Therefore, the study aims to investigate the properties of porous concrete experimentally using recycled concrete aggregate as partial replacement of natural coarse aggregate. The test results for engineering properties of recycled concrete aggregate at different ratios of 0%, 15%, 30%, 45%, and 60% revealed that the material is suitable to be used as coarse aggregate. To determine the behavior of the concrete, both Workability and fresh density at fresh state, compressive strength, split tensile strength, porosity and permeability of the concrete were examined at 7, 14, and 28 curing days using specimen cube size of 150mm* 150mm* 150mm and cylinders of 200mm* 100mm. The experimental result indicates that replacement of recycled concrete aggregate by natural coarse aggregate improves the porosity and permeability of the concrete. Also, the optimum replacement percentage of RCA for porous concrete strength is at 30% with 28 th day compressive strength of 17.37MPa which is greater than the suitable value. A regression model was also developed to determine the degree of workability using compacting factor test. From the result, coefficient of determination (R 2 ) shows that compacting factor test values are 88% accurate to govern the workability of fresh porous concrete. Generally, the finding of this experimental study indicates that the use of recycled concrete aggregate as coarse aggregate for porous concrete production is practicable.