Green Concrete as a Building Material - Essay Example

Green Concrete as a Building Material The structures we reside in have tremendous effects on our environment. Concrete isthe worlds most used building material that can be shaped to make bridges, roads, dams, tunnels, buildings, etc. Of late, researches have shows that every year, over 6 billion tons of concrete are produced globally, which produces a large amount of carbon dioxide together with other green house gases into the environment, which leads to global warming. In recent years, worldwide concerns on climate changes have led researchers and scholars to find methods to minimize CO2 and other green house gas emissions. Green construction looks to balance resource efficiency, social and health issues all through the life cycle of a structure. Among them, green concrete many benefits that help in achieving this objective. This article offers an overview of the contemporary state of green concrete, which have reduced ecological impact. It is also stressed here that the use of green concrete has low energy cost, lower green house gas emissions, as well as low maintenance cost, which, in the long run, leads to sustainable construction materials. In addition, in terms of resource preservation, reuse of industrial byproducts and post-consumer wastes used as a partial replacement for Portland cement clinker, makes green concrete much more durable and eco-friendly. The overall change in the economic landscape and resource utilization factors is at the forefront of many green building movements. The research broadly focuses on the benefits of green concrete in achieving the sustainable and environment friendly construction goal. In regard to the use of concrete in construction, a number of questions arise; would the green concrete alleviate environmental pollution caused by the normal cement? Might there be any compromise in the quality and sustainability of green concrete structure? What are other social and economic contributions of green concrete relevant to the bodies advocating the green concrete? Green Concrete as a Building Material Introduction The buildings we reside in have an overreaching effect on our environment. Green building, otherwise referred to as sustainability, seeks to balance health, resource efficiency, as well as social concerns, all through the life cycle of a structure (Penttala 2004, p. 409). Green concrete has a couple of benefits to present in attaining this objective. Cement is a gray powder, which, when added to water, binds stone and sand together to produce concrete. Concrete is the worlds number one building material because of its durability and strength (Hendriks et al. 2004, p. 15). The longevity of this material means much less maintenance or replacement when contrasted to other building products. Even though, producing cement needs abundant energy, cement is merely a small portion (7-15%) of concrete (Penttala 2004, p. 409). The other ingredients require overly low energy to obtain. The high temperatures required for cement production make it an energy intensive process when contrasted to the manufacturing of other building materials (Penttala 2004, p. 409). Both chemical reactions that arise due to the processing of raw materials and fuel burning produce carbon dioxide (CO2) that, on the other hand, lead to global warming. This environmental effect can be mitigated through replacing a portion of the cement with blast furnace slag, fly ash, silica fume, as well as rice husk ash, among many other materials, in order to reduce carbon emissions produced during this process (Hendriks et al. 2004, p. 15). The paper discusses various drives on the way to improve environmental impacts of concrete for its sustainability as a green building material. Identification of cement specific properties in either by product or waste materials is fully covered. Discussion The support towards green concrete revolves around the utility cost, health, durability and reduced effect on the community (Nurdeen & Kabir 2010, p. 194). By utilizing nontoxic materials, sustainable structures have better indoor air quality. They also utilize materials opposing to moisture and rot to abolish issues concerning the growth of hazardous mildew and mold (Malhotra 2007, p. 61). Exterior walls normally have larger thermal mass, which provides the dual advantage of muffling outdoor noise and reducing temperature fluctuations. Sustainable structures make more use of substances harvested or manufactured in an ecologically responsible way (Malhotra 2006, p. 42). They as well utilize materials available in the vicinity, not just to lessen transportation effects (like pollution and fuel consumption) but also to improve the local economy. Attention to landscaping is significant also, with consideration offered to reducing storm water runoff, which can contaminate local watercourses (Battelle 2002, p. 67). Building with extremely durable, less expensive materials, for instance green concrete, prolongs the positive life cycle of a sustainable structure and reduces replacement or maintenance costs (Nurdeen & Kabir 2010, p. 194). These days, green concrete stands for ecologically friendly concrete (Battelle 2002, p. 67). This is a type of concrete, which has a decreased ecological effect with regards to energy emissions and consumption in its production, together with a reduced production of CO2 and other green gases (Malhotra 2006, p. 42). Green concrete can regularly, as well, be cheap to manufacture, since waste products are utilized as a fractional alternate for cement, energy use in production is reduced, landfill taxes are shunned and durability is enhanced. In this manner, in terms of energy and resource conservation, green concrete is effective to a large extent (Battelle 2002, p. 67). In the manufacturing of green concrete, it has at least 20% fly ash, a residual from power plants of coal-burning; it process produces less CO2 emission (Malhotra 2006, p. 42). Furthermore, concrete also can be put together with silica fume, blast-furnace slag or recycled concrete that has been crushed giving the producer more eco-friendly alternatives (Malhotra 2006, p. 42). Types of Additional Cementitious materials in Green Concrete Some additional cementitious materials (SCMs) can be found in large quantities, which can replace Portland cement used to create concrete (Tafheem et al. 2011, p. 98). These include ground granulated blast-furnace slag (GGBS), fly ash, natural pozzolans, silica fume and rice-husk ash, among others. Fly Ash Fly ash, also known as pulverized fuel ash (PFA), is a product that results from the burning of powdered coal at very high degrees. Its most known source are electric power-generating stations (Tafheem et al. 2011, p. 98). Those advantages of using PFA in concrete have been given below. 1) Improved workability and reduced water demand-Fly ash usually results in enhanced workability. The lessening of water requirement amalgamation PFA in cement is because of the spherical shaped particles plus their smooth surface (Tafheem et al. 2011, p. 98). 2) Higher enduring and strength gain: Fly ash concrete usually leads to lower, premature strength, but it still combines with free lime, rising compressive strength in due course (Tafheem et al. 2011, p. 98). 3) Lessened heat of hydration: Fly ash reduces the heat of hydration, which makes it popular for mass structures (Tafheem et al. 2011, p. 99). 4) Reduced permeability: research has established that permeability of this substance is significantly lower compared to plain Portland cement concrete (Tafheem et al. 2011, p. 99). This is because of the pore refinement, which takes place due to extensive pozzolanic action by the fly ash. 5) Increased durability: substituting Portland cement with Class F fly ash reduces the tricalcium aluminate substance of the concrete, which makes it more resistant to sulfates (Tafheem et al. 2011, p. 99). Fly ash rate also lowers the rate of attack from acids since permeability is reduced. 6) Lessened efflorescence: this substance chemically binds salts and free lime, which can lead to efflorescence (Tafheem et al. 2011, p. 99). 7) Reduced shrinkage: the prime contributor to drying contraction is water content (Tafheem et al. 2011, p. 99). This lubricating action of this substance reduces water requirement and as an impact, reduces drying shrinkage. Ground Granulated Blast-Furnace Slag (GGBFS) This substance is obtained through adding water to molten iron slag, which later latter forms a fine powder (Tafheem et al. 2011, p. 99). The comparison of GGBFS with Portland cement concrete can be summed up as follows: (1) concrete with Pozzolana cement or with greater dosages of GGBFS normally have lower heat of hydration; (2) concretes that have slag might show fairly longer periods of setting when compared to straight Portland cement mixtures, specifically for higher and moderate dosages and at reduced, ambient temperatures; (3) Concrete with Type IS cement achieves strength gradually, having much lower strength at early stages and higher or equal strength at later stages; (4) rising slag dosage is related to lower permeability in concrete; (5) GGBFS dosages higher than 35% concrete by mass of cementitious material, have shown an upgrading in the resistance to sulfate reaction and suppression of alkali-aggregate expansion (Mahasenan et al. 2003, p. 56). Silica Fume (SF) Silica fume is a by-product produced when ferro-silicon alloys or silicon metal are smelted by means of electric arc furnaces (Kim & Lee 2013, p. 662). This gauzily divided, smooth powder arises from the strengthening of silicon oxide gas. Silica fume is made mainly of silicon dioxide (SiO2). It is mainly specified for particular applications, for instance structures open to aggressive chemicals (Samarin 2009, p. 8). Its main use is to improve the durability of concrete through making it less porous. Silica fume incorporation benefits concrete in mainly two ways. First, the small particles physically lessen the void gap in the cement matrix — this filling up the gaps is referred to as packing. Second, silica fume is a tremendously reactive pozzolan (Amato 2013, p. 300). Rice Husk Ash (RHA) Together with granulated blast-furnace slag and fly ash, rice husk ash, is one of the most significant complementary cementitious material for application as a fractional substitute for Portland cement in concrete to trim down CO2 emissions (Burton & Pitt 2001, p. 34). The RHA has a lot of silica content, obtained through burning rice husk to get rid of any volatile organic carbon like lignin and cellulose. Goals of Producing Green Concrete The main aim of manufacturing green concrete is to make an ecologically pleasant concrete and lessen the harmful residuals manufactured in different industries and make the concrete inexpensive (Gore & Steffen 2008, p. 55). To facilitate this, new technology has to be developed. The technology takes into consideration each and every phase of a concrete constructions life cycle, i.e. specification, structural design, manufacturing and maintenance, and it comprises of all elements of performance, i.e. mechanical properties (shrinkage, strength, static behavior, creep etc.), fire resistance (heat transfer, spalling etc.),workmanship (strength development, workability, curing etc.), durability (frost, corrosion protection, new deterioration mechanisms etc.),environmental elements (CO2-emission, recycling, energy etc.) (Gore & Steffen 2008, p. 55). Some of the goals associated with economy and residual reduction are summarized below: (1) concrete with negligible used coal, (2) concrete with green binders and cement, (3) concrete with lifeless residuals, (4) function and continuation technology for green concrete buildings, (5) green structural solutions for green concrete (Yaghoobian & Kleissl 2012, p. 25). Environmental objectives are as follows: (1) carbon dioxide emission aggravated by concrete production should be lessened by a minimum of 30%, (2) the industry‘s residual products should be utilized in concrete production, (3) new forms of residual products, previously land disposed of or filled in other ways, should be utilized in concrete production, (4) carbon dioxide-neutral, waste-derived fuels should replace a minimum of 10% of the organic fuels used in cement production (Ademola & Oguneletu 2005, p. 106). Reducing Environmental Impact Through Green Concrete The World Earth Summits in Brazil and Japan, in1992 and 1997, respectively, made it highly clear that decreasing the rate of greenhouse gas emissions is vital for sustainable growth. Whereas greenhouse gases of concern consist of nitrous oxide (NOx) as well as methane (CH4), their volumes are moderately small contrasted to that of the main greenhouse gas, CO2 (Ademola & Oguneletu 2005, p. 107). As a result, the developed nations are thinking about putting restrictions on the emission of these gases. The greenhouse gases permit high-frequency radiation from the sun to enter the atmosphere and temperature the earth surface, but they do not permit the low-frequency radiation from earth‘s surface to leave the atmosphere (Ademola & Oguneletu 2005, p. 107). The higher volume of greenhouse gases in the air increases the temperature of earth‘s surface. Just a minute raise in the volume of greenhouse gas creates a larger rise in the global temperature. There are many ways that the concrete and cement industry can aid towards lessening CO2 emissions (Gore & Steffen 2008, p. 56). These consist of: (1) utilizing less Portland cement, (2) utilizing more complementary cementitious substances, (3) using recycled materials in concrete, (4) substituting high carbon fuels through low carbon fuels and, (5) when possible, dictating strength reception criteria at 56 or 91 days rather than 28 days (Ademola & Oguneletu 2005, p. 107). Conclusion A sustainable industrial development will influence the concrete and cement industry in many respects as the construction industry has ecological impact because of high consumption of energy, as well as other resources. So the vital issue is the utilization of eco-friendly concrete or green concrete to facilitate global infrastructure-development without raise in CO2 emission. Environmental problems related to the CO2 emissions – from the manufacture of Portland cement, resource and energy conservation considerations and expensiveness of Portland cement plants - command that complementary cementing materials must be utilized in increasing quantities to substitute Portland cement in concrete. Another, maybe even more significant issue, is the use of more ecologically friendly structural designs using more eco-friendly preservation or repair strategies that need less use of resources, ease CO2 emissions at each and every phase in the entire service life of the structure. References Ademola, J A & Oguneletu, P O 2005, Radionuclide content of concrete building blocks and radiation dose rates in some dwellings in Ibadan, Nigeria, Journal of Environmental Radioactivity vol. 81, no. 1. pp. 107–113. Amato, I 2013, Green cement: concrete solutions, Nature vol. 494, no. 5, pp. 300–301. 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Jappy, Exploiting wastes in concrete: proceedings of the international seminar, University of Dundee, Scotland, UK, p. 8 Tafheem, Z, Khusru, S & Nasrin, S 2011, Environmental impact of green concrete in practice, Proceedings of the International Conference on Mechanical Engineering and Renewable Energy 2011(ICMERE2011), Chittagong, Bangladesh. Yaghoobian, N & Kleissl, J 2012, Effect of reflective pavements on building energy use, Urban Climate vol. 2, no. 1, p. 25. Read More