Utilisation of Fly Ash in Structural Concrete for Sustainable Construction

Abstract

Our industrial world produces huge quantities of fly ash, which is a waste and need to be disposed safely or else it can cause disastrous consequences. The disposal of fly ash has been causing a headache to the environmentalists across the globe. Fly ash is a high pozzolanic industrial waste which has the substantial potential to substitute Portland cement, a major producer of CO2 and thereby decreasing greenhouse gas emissions. The production of fly ash is increasing in every year but the utilisation of fly ash is not even half of the production of fly ash. The effective utilisation of fly ash is restricted only to manufacture of bricks, producing fly ash based pozzolanic cement and use in pavements. To utilise the fly ash in high volume the innovative idea is fly ash used as a replacement material for cement and fine aggregate in structural concrete like RCC beam, concrete paver blocks, making fly ash pellets and fly ash angular aggregate.

Concrete paver blocks are being used for various purposes like paving of approaches, paths, parking places and footpaths. They also find their application in roadways or pavements. The increasing costs of construction or building materials and the need to meet sustainable development, different alternative construction methods, techniques and materials are being used extensively to replace old conventional methods. So as to enhance and improvise the applications of concrete paver blocks, proper knowledge and understanding of the products produced with materials, which are available locally and mineral admixtures, which are produced indigenously is essential.

This paper discusses sand replacement with fly ash, coarse aggregate replacement with fly ash pellets in low grade concrete, cement and sand replacement with fly ash in high grade concrete paver blocks. For low grade of concrete, the mix design was prepared for M20 concrete as per IS method. Sand was replaced partially with fly ash up to 60% by weight. To know the effect of sand replacement compressive strength, flexural strength, split tensile strength at 7 and 28 days are studied and optimum percentage of replacement noted. Then RCC beam casted with optimum percentage of sand replacement for flexure failure and behaviour compared with control concrete beam. Again the 10mm coarse aggregate were replaced up to 100% and compressive strength of cubes were studied. The mix design was done for M20 grade of concrete for light weight concrete beam with fly ash pellets without granite aggregate, compressive strength of cubes and behaviour of flexural failure of RCC beam studied and compared with conventional concrete beam.

Finally, the mix design was done for high grade concrete paver block by considering medium traffic. For the medium traffic the grade of concrete considered is M40. The shapes of the paver block considered in this project are Zig zag (60mm), Zig Zag(80mm), Dumbel (60mm), Rectangle(60mm), I(60mm), Pentagon(80mm). Sand replaced by fly ash source of steel plant sambalpur up to 40% and the corresponding 7 and 28 days compressive and flexural strength, water absorption, Durability (Freeze thaw test) characteristics were studied and compared with conventional control mix concrete. Similarly cement replaced by fly ash source of steel plant Dhenkanal up to 40% and the corresponding 7 and 28 days compressive and flexural strength, water absorption, characteristics were studied and compared with conventional control mix concrete.

The experimental results indicate there is significant improve in strength characteristics over control concrete when sand replaced by fly ash source of Bushan steel plant sampalbur up to 30% in low grade concrete and sand replaced by fly ash source of Bushan steel plant sampalbur upto 30% and cement replaced by fly ash source of Bushan steel plant Dhenkanal up to 40% in high grade concrete paver block. Since the fly ash is used for sand replacement it reduces the depletion of mineral resources and used for cement replacement it reduces the production greenhouse and makes sustainable environment.