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Recycled Aggregate Fly Ash Concrete: An Exploratory Study
-- D N Parekh and C D Modhera
Concrete is one of the most widely used construction materials in the world, mainly due to its favorable features such as durability, versatility, satisfactory compressive strength, cost-effectiveness and availability. Globally, the concrete industry consumes large quantities of natural resources, which are becoming insufficient to meet the increasing demands. At the same time, many old buildings have reached the end of their service life and are being demolished, resulting in waste concrete; some concrete waste is used as backfill material, with much being sent to landfills. Recycling concrete by using it as new aggregate in concrete could reduce concrete waste and conserve natural sources of aggregate. In the last two decades, a variety of recycling methods for construction and demolition wastes (CDW) were explored and developed. It is known as recycled aggregate (RA). BS EN Standards (BS 8500-1 Concrete, 2006; and BS 8500-2 Concrete, 2006) recommends that recycled concrete be used in secondary structural members of relatively low grades, e.g., curbs, paving blocks and ground bearing floor slabs. © 2012 IUP. All Rights Reserved.
High Strength Concrete Using Mineral and Chemical Admixtures
-- M Vijaya Sekhar Reddy, J Rajendra Prasad and I V Ramana Reddy
In this experimental investigation, a brief review is presented on high strength concrete by using mineral and chemical admixtures. We have designed high strength concrete of grade M80. We have used all the mineral admixtures, namely, fly ash, blast furnace slag, silica fume and metakaolin, contributed by various reputed industries in India. We have collected all the details of these mineral admixtures from those reputed industries, and a brief introduction of all mineral admixtures is presented in this project work. We have also used superplasticizer (chemical admixture), namely, conflo manufactured by “fosrock chemicals” in Bangalore. We have used this superplasticizer in order to achieve good workability under lower water-cement ratio for high strength concrete such as M80. We have compared the compressive strengths of all these mineral admixtures at their individual replacements and combinations of various percentages. We have also found out the percentage replacements of these mineral admixtures in order to achieve maximum strength. We have presented the results in the form of graphs. © 2012 IUP. All Rights Reserved.
Effects of Sodium Chloride and Magnesium Sulphate on Glass Concrete
-- M N Bajad, C D Modhera and A K Desai
Initially, in India, the construction industry and the engineers did not take advantage of research and scientific developments in concrete construction to its fullest extent due to the lack of education and training facilities in concrete technology. Due to the lack of knowledge and skill of supervisors and construction contractors, there is a wrong notion that the greater the quantity of cement in concrete, the better will be the quality and strength of concrete. This paper reports the results of an investigation carried out to understand the effect of chloride and sulphate attack on concrete. It was observed that several million tons of waste glass are generated annually worldwide due to the rapid growth of population, improvement in the standard of living, industrialization and urbanization. Hence utilization of waste glass has become a critical issue worldwide. Concrete produced by replacing cement with waste Glass Powder (GP) in different proportions was studied. It was found that the strength properties were affected when concrete was subjected to attack, and higher resistance to attack was obtained when 20% cement was replaced with waste glass. © 2012 IUP. All Rights Reserved.
Performance of FRP Wraps on Reinforced Concrete Beams Exposed to Accelerated
Corrosion -- Dave Urmil V and Mistry Gaurav B
Comparative performance of Reinforced Concrete (RC) beams exposed to accelerated corrosion by impress anodic current and repaired using Fiber Reinforced Polymer (FRP) material is evaluated. 16 beams of 150 mm ´ 250 mm ´ 1,200 mm effective span are cured for 28 days. Four beams are subjected to 8 wetting-drying cycles of two weeks each—the beams are immersed in water with 3.5% NaCl solution up to tension reinforcement for one week and kept in open atmosphere for one week. Beams after exposure are repaired using polymer mortar, Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP) wrapping. Another four beams are protected using the GFRP and CFRP wrapping. The beams are subjected to corrosion using procedure described above for 16 weeks. Cracks observed during visual observation and half-cell potential measurements confirmed the effects of corrosion for all the beams. Corrosion has brought minor reduction in load carrying capacity, increase in deflection and higher strain for beams wrapped by GFRP and CFRP before corrosion as compared to that of control wrapped beams. Similar results are observed for beams wrapped by FRPs after corrosion. Superior performance is exhibited by CFRP material compared to GFRP in terms of corrosion protection for concrete. Thus, FRP wrappings have proved excellent material for protection of concrete against deterioration under corrosive environment. © 2012 IUP. All Rights Reserved.
Research Note:
Material Wastage in the Building Construction Projects
-- B L Rajput, Nitin Shelar, Chetan Gawade and Ravindra Bhoite
The size of the Indian construction industry is growing at a substantial rate. The Global Construction Perspectives, UK, and Oxford Economics, UK, predict that by 2020, Indian construction market will be worth almost $650 mn, making up to 5% of world’s total construction output (Global Construction, 2020). Emerging construction markets in Asia-Pacific will grow by an estimated 125% till 2020. India will overtake Japan by 2020 to become the third largest global construction market after China and USA. The Eleventh Five-Year Plan of Government of India allocates $492 bn for infrastructure development over the period 2007-2012. The residential demand for the period 2010-2014 is estimated to be approximately 4.25 million units, of which mid-range and affordable sectors continue to capture a significant share of 70% (www.buisness-standard.com/india/news). © 2012 IUP. All Rights Reserved.
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