Improving Sustainability in Construction | Assignment
Added on 2019-11-20
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STUDENT NAME - 42908 - Assignment 2By ‘Author Name’“Modular Construction Using Precast Concrete in Order to Reduce Wastages andEnvironmental Degradation”Affiliation (MSc Profile or Track) & Study noAbstractOver the past few decades, there has been a growing necessity to cut down on wastages in theconstruction sites. Unfortunately, the conventional construction systems provide for verylittle to waste mitigating measures. A higher cost of production further comes up as a resultand environmental degradation comes about due to the fact that wastes are environmentalpollutants. This has promoted the adoption of precast concrete systems. The construction(operation) process would change significantly due to the difference in material applicationbut this ultimately reduces the amount wastages. This is attributable to the off-site manner ofmember element casting that happens in a minimal wastage industrial processes. With that inmind, further research has been suggested to curtail wastages, costs and further improvesustainability while using the precast concrete.1.IntroductionWith wastes accounting for close to 6% - 9% of total project costs in the constructionindustry, the amount of losses is very significant considering the high cost of projects[ CITATION Bli10 \l 1033 ]. This industry still remains one of the most profitable sectors of theeconomy which leads to most attempts to mitigate wastage in construction sites beinguneconomical, a factor which further facilitates construction to carry on without properpreventive measures. As a result, both the technical and client parties incur huge costsconsidering the fact that the wastes have to be accounted for. Building projects that utilizeconcrete as the main material, in most cases, usually end up with a wastage factor of between5% - 10% of the overall costs. These wastes also contribute to a variety of environmentalproblems which have proven to be a setback in the construction industry. This waste materialis mostly in the form of concrete, used formwork, steel and it is usually a result of human andenvironmental factors within the site environment (Tam, et al, 2005).Whereas the disposal mechanisms currently being used help achieving a reduced wasteimpact on the environmental, the responsibility falls upon engineers and contractors to find abalance between waste free constructions and healthy profit margins. More alternatives that10 August 20171
STUDENT NAME - 42908 - Assignment 2reduce the amount of wastages and improve the quality of work too therefore have to bedeveloped (Mao, et al., 2013). This is where modular construction techniques come in asmanufacturers can come up with environmentally friendly materials while at the same time,implementing environmentally friendly building methods that also give way for theincorporation of sustainable energy. While relying heavily on existing literature, this reviewwill concentrate on precast concrete systems explaining how and when these systems areused, their material saving and environmental friendliness, the gaps in the research andfurther link them to my research project.2.Literature reviewModular construction systems categorically offer a solution to the issue of waste reduction.This is advantageous for developers seeking to increase their profit margins based on thefavourable economies of scale of the total cost of the development. As argued by Lu Aye, T.Ngo, R. H. Crawford, R. Gammampila and P. Mendisa, modular systems provides up to 51%material saving by mass by incorporating reused materials in modular construction that usedtimber, steel and concrete (Lu, et al., 2012). Concrete is one of these modular constructionmaterials whose application has been increasing gradually over the years for this very reason.As a fact, a study by Weisheng Lu and H. Yuan indicates a wastage factor of only 2% or lesswhen utilizing precast concrete in construction (Lu, 2013).In using precast concrete systems, the person using it may choose to go with a fully modularapproach or the inclusion in situ concrete during construction various stages. Whenconstruction teams utilize this precast approach, however, they may do so for specificmember elements including slabs, columns and beams. The reasons for using these membersinclude good insulation, easy demolition, higher frame strength and cost reduction [ CITATIONAri10 \l 1033 ].When looking at the various approaches to this system, 2 main approaches stand out whosedifference is in the percentage amount of precast elements used. They are discussed below.Fully precast concrete systems: this is where all member elements are cast off site andtransported to the site. Some of the best examples of these of the application of precastmodular structures are artificial harbours and bridges. One of the most recognized examplesis the Mulberry Harbour that was temporarily constructed by the British during the SecondWorld War to provide a platform for quick offloading of cargo along the beaches of10 August 20172
STUDENT NAME - 42908 - Assignment 2Normandy, France. At present, most bridges are constructed using prefabricated memberelements where the only in situ components are the abutment (Li, Z., et al., 2014).As argued by researchers R. Lawson, R. G. Ogden and R. Bergin, precast concrete systemshave a proven record of maintaining high levels of structural durability and stability as all themember elements have better tensile and compressive strengths compared to the conventionalin situ members (Lawson, et al., 2011). This provides the client and contractor with a betterschedule management and waste saving system. When considering the economies of scale,larger projects that use precast concrete are ultimately much cheaper to run and develop thantheir in situ concrete alternatives. The economic aspect of this system can however be non-existent when comparing to theconventional systems currently in use. This mean that, for smaller structures, the economiesof scale apply. Where development projects are smaller, there are significantly less wastesand time spent and this usually less and this leaves very little room for extra economicrecovery [ CITATION Bli10 \l 1033 ]. In actual sense, they could end up being more expensivethan the conventional concrete systems. This is because of their relatively higher productioncosts. Questions have also been raised by researchers about their seismic performance withsome researchers suggesting they could be weak.Partial precast concrete systems: these is usually when the construction utilizes both precastand in situ concrete in the same project. These practices are currently incorporated in high-rise structures such as warehouses plazas, residential high-rise blocks, bridges, harbours.These may not be as strong as precast structures but they also exhibit high levels of structuraldurability and reliability (Azman, et al., 2010). Partial precast concrete systems can be anadvantage to developers constructing small units as, they are much cheaper than theiralternatives e.g. those with three floors or less (Azman, et al., 2010).The major disadvantage that this system is that it is prone to wastages when comparing it tothe alternatives. In actual sense, waste is significantly reduced when comparing thedevelopment to concrete structures cast right there on site. They are, prone to some slightwastage as using the in situ cast concrete system leads to wastage.The research gaps existing in the in the body of knowledge relating to precast systems is incomplementary sustainable material incorporation. While it has been noted that modularconstruction does, in a lot of cases utilize reused materials, very few materials have beenresearched on that complement the precast concrete systems. These materials could include10 August 20173
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