LDA, An Eco-friendly Altrnative to Natural Aggregate in Structural Concrete for Engineering Construction
Publication Date : 17/09/2017
ABSTRACT Low Density Aggregate (LDA) made from fly ash, a waste product from the thermal power plant was used to replace the natural aggregate which turn out to be an efficient effort for green concrete. The process of creating LDA uses above 90% fly ash as major raw material mixing with small volume additives, carbonaceous solid fuel and water. The additives are clay and the coal which contributes the carbon percentage depending on the particle size and loss of ignition in the fly ash. After agglomeration and palletisation, the green pellets are transferred to a sinter machine for sintering. The physical characteristic of LDA product is found to be a superior aggregate than the natural aggregates. In this study, at first the concrete cubes were made using cement, sand and natural aggregate by mixing water. The materials were poured inside the 100 mm cube mould for making the samples. Secondly, the same procedure was followed to replace natural aggregate with the LDA keeping cement and sand content as the same. The LDA was collected from IMFA, Choudwar of two grades, one 4mm to 8mm and another 8mm to 16mm. The two aggregates were used in proportion of 40% to 60% respectively of the total LDA percentage. After de-moulding of the concrete cubes with LDA and natural aggregate, the samples were kept in two different curing conditions. One kept for moist curing for 28 days and another kept 28days in air-curing. After 28 days, both the cases of cubes were subjected to the compression test. It was observed that the concrete cube with natural aggregates had ultimate strength of 20.36 MPa, and the cube with LDA showed the ultimate strength of 16.69 MPa under the moist curing for 28days. However, the concrete cubes in air curing showed 17.93 MPa with natural aggregate and 18.3 MPa with LDA. The LDA cubes without curing or air curing showed higher compressive strength than the LDA cube with moist curing which is a positive result for places where curing is difficult to undertake. It was also observed that the compressive strength of the LDA concrete was about 10% less compressive strength than the concrete with natural aggregates under the same cement and sand content. The compressive strength of LDA concrete can be increased by changing the grading of the LDA and adding other admixtures. Due to limitation of time, it is recommended that for future study the LDA concrete should be made with different grades of LDA, 50:50 LDA and natural aggregate replacement, and at different cement content to achieve best results out of LDA.