Evaluation of Strength of Geo-Polymer Concrete Using Combination of Fly Ash and GGBFS as Source Material

Abstract

Concrete usage around the globe is second only to water. An important ingredi- ent in the conventional concrete is the Portland cement. One ton of cement emits approximately one ton of carbon dioxide in the atmosphere. Moreover, cement pro- duction is not only highly energy-intensive, next to steel and aluminium, but also consumes significant amount of natural resources. In order to meet infrastructure de- velopments, the usage of concrete is on rise. The global cement industry contributes around 2.8 billion tons of the greenhouse gas emissions annually, or about 7% of the total man-made greenhouse gas emissions to the earth's atmosphere. It is essential to nd alternatives to make environment friendly concrete. One of the alternative is to OPC concrete is to replace the amount of Portland cement in concrete with by-product materials such as y ash and ground granulated blast furnace slag. Another alternative to make environmentally friendly concrete is the development of inorganic alumina-silicate polymer, called Geopolymer, synthe- sized from materials of geological origin or industrial by-product materials such as

y ash,slag that are rich in silicon and aluminum. By exploring use of the y ash and slag based geopolymer concrete, two environment related issues are tackled i.e. the high amount of CO2 released in the atmosphere during production of OPC and utilization of industrial waste like Fly ash and Slag. Fly ash and slag-based geopolymer concrete has excellent compressive strength, suffers very little drying shrinkage and low creep, excellent resistance to sulfate at- tack, and good acid resistance. It can be used in many infrastructure applications. One ton of low-calcium y ash can be utilized to produce about 2.5 cubic meters of high quality geopolymer concrete, and the bulk cost of chemicals needed to manu- facture this concrete is cheaper than the bulk cost of one ton of Portland cement. Given the fact that y ash is considered as a waste material, y ash and slag-based geopolymer concrete is, therefore, cheaper than the Portland cement concrete. The durable properties of geopolymer concrete can further enhance the economic benefits. In all, there is so much to be gained by using geopolymer concrete. Experimental work in this major project comprises preliminary investigation on the y ash based and slag and based geopolymer concrete. Low calcium Processed

y ash from Dirk India Private Limited has been used for y ash based geopolymer concrete. And ground granulated blast furnace slag from JSW steel has been used for slag and y ash based geopolymer concrete.The effect of good quality y ash as well as slag on the mechanical properties like Compressive strength, Split Tensile strength and Flexural strength of geopolymer concrete has been investigated. Results are compared for ordinary Portland cement concrete, y ash and slag based geopolymer concrete for M25 normal grade. For developing the mix proportion of geopolymer concrete, parameters like alkaline liquid to y ash ratio 0.4, rest period 1 day, curing temperature 900C are kept con- stant.The parameters such as alkaline liquid ratio 2 and 2.5, super plasticizer dosage 1.5% and 1.0%, curing period 24 and 48 hours and concentration of NaOH solution 12 M extra water content 15% and 10% etc have been varied throughout investigation. The parameters giving highest results are selected for making y ash and slag based geopolymer concrete. The density of geopolymer concrete was found equivalent to that of control concrete for both grades. For M25 grade geopolymer concrete, cement content is fully replaced by combination of processed y ash (50:50) proportion in case of y ash and slag based geopolymer concrete. The cubes, beams and cylinders as per IS provisions has been used for measuring the Compressive strength, Split Tensile strength and Flexural strength respectively for all concrete mixes. Samples have been tested at 3, 7 and 28 days, respectively. Various curing techniques were employed in order to study their effect on various properties of geopolymer concrete. Geopolymer concrete was exposed to saline water curing with 8% and 15% concentration. The geopolymer concrete exposed to 15% concentration of saline water was found out to gain more strength as compared to normal control concrete. Similarly geopolymer concrete was exposed to high temper- ature of 5000C for 2 hours, 4000C for 4 hours and 3000C for 6 hours respectively in a mufie furnace. Geopolymer concrete subjected to high temperature conditions shows increase in strength at initial ages. Ambient curing for geopolymer concrete was also carried out and its strength properties were studied. The geopolymer concrete showed excellent gain in strength for ambient curing as well as saline water curing. The results have indicated that the geopolymer concrete gives good results for various mechanical properties as compared to control concrete as Very less amount of variation is observed. The geopolymer concrete is a good alternative as a construction material from strength considerations.