APPLICATION OF GEOTEXTILES IN PAVEMENT

The production of Portland cement has been swelling manifold throughout the world due to the mounting demands of the construction industry. However, this huge production of Portland cement is highly internal- energy-intensive and causes emission of green house gas, CO2. The pollution involved in the manufacture of cement hampers the image of concrete as a sustainable material. Efforts are continuously being made to make concrete environmentally friendly. Concrete is the most commonly used construction material without proper substitute so far. With the increase in construction activities, there is heavy demand on its ingredients, particularly for cement. Many such alternates for cement have been tried by different scientists worldwide, but the best choice of a substitute material to cement has been agreed to be the Geopolymer paste. Also, cement is manufactured by the calcinations process of a hefty quantity of lime stone and this large quantity of lime stone is explored from the lime quarries, which in turn creates an imbalance in the mineral wealth of our planet. In spite of the easy availability of Portland cement in the market at present, concrete made out of it is found to be less durable in some of the very severe environmental conditions due to the presence of free calcium. Therefore, arrival of any new alternate material of construction immediately should be assessed for both strength and durability. The complex phenomenon of aggressive chemical attack and the associated damage to concrete considerably reduces the strength and stiffness of reinforced concrete members leading to premature failure. Failure does not only mean structural collapse but also includes loss of serviceability characterized by cracking, spelling, deboning or excessive deflection. Keeping all the above aspects in mind, a detailed experimental investigation on the manufacturing process, serviceability under loads, durability against various severe disturbing agents are inevitable as far as a new material is concerned. Geopolymer concrete is a firsthand development in the world of concrete in which cement is wholly replaced. Geopolymer concrete is a versatile and embryonic material in the construction industry. In this regard, Geopolymer concrete can be considered as a potential candidate material to replace cement concrete which does not generally have free lime which attributes an inherited property of acid resistance. Geopolymers are ceramic materials that are produced by alkali activation of alumina-silicate raw materials, which are transformed into reaction products by polymerization in a high pH environment and hydro thermal conditions at relatively low temperatures. As relatively new material, extensive studies are still needed to explore its applicability as a construction material. In this research, anthracite coal burnt low calcium fly ash from Tuticorin Thermal Power Station, Tamilnadu, India has been used to synthesize Geopolymer concrete. This work is state-of-the-art and the first of its kind in India to evaluate the applicability of Indian fly ash in Geopolymer concrete as source material for manufacturing alumina-silicate concrete under heat curing, with the aid of an exclusively designed Heat-curing chamber in the Geopolymer concrete laboratory of Thiagarajar College of Engineering, Madurai, Tamilnadu, India. The present research has been organized into four primary sectors namely achievement of normal strength (30 N/mm2) and high strength (50 N/mm2) Geopolymer concretes, durability study on plain Geopolymer concrete cubes and cylinders, comparative study on the flexural behavior of reinforced cement concrete and reinforced Geopolymer concrete beams of various sizes, and durability study on reinforced Geopolymer concrete beams exposed to sulfuric acid attack, chloride attack, sodium sulfate and magnesium sulfate. Under the prime sector, using low calcium class F Indian fly ash, M30 and M50 grade Geopolymer concrete cubes and cylinders were manufactured and tested for resistance to sodium sulfate, sulfuric acid, and chloride and water absorption according to the procedure given in ASTM C 642. Durability aspects such as visual appearance, change in mass and change in compressive strength were noted and compared with ordinary Portland cement concrete cubes and cylinders of same grades subjected to the above tests. From the test results, it was observed that Geopolymer concrete exhibited very good resistance to all exposures, whereas OPC concrete got deteriorated very much. Reinforced cement concrete and reinforced Geopolymer concrete beams were cast and tested for load at first crack, ultimate load, ultimate moment and maximum deflection. The experimental results of reinforced cement concrete and reinforced Geopolymer concrete beams were compared. It was observed that with the same percentage of tensile reinforcement, reinforced Geopolymer concrete beams showed higher ultimate moment resistance which exceeded by reinforced cement concrete beams with exemplary ductility. Finally, small reinforced Geopolymer concrete beams were cast. The specimens were subjected to durability tests such as resistance to chloride attack, sulfuric acid attack, sodium sulfate and magnesium sulfate. Of all the permeability tests on these durability parameters, it was observed that there was marginal reduction in the weight of the specimen subjected to acid attack and the weight loss was negligible in the case of specimen subjected to sodium sulfate attack. But the deposits found on the elements exposed to magnesium sulfate solution not only increased the weight marginally but also enhanced the flexural strength. Study of these durability tests reveals that Geopolymer concrete has the potential and could well be implemented into prefabricated structural applications particularly in aggressive environmental conditions