Sustainability in the Construction Industry - Essay Example

Sustainability in the Construction Industry - An appraisal of Recycled materials. A Thesis in Civil Engineering Submitted by to insert the Name with Affiliation here) March 2009 Contents Particulars Page no 1.0 Abstract 3 2.0 Introduction 3 3.0 Reusability as sustainable solution 4 4.0 Aims and Objectives 6 5.0 Initiatives to enhance reusability concepts 6 6.0 Experience on reuse initiatives 7 6.1 Production of Secondary Aggregates 8 6.2 As Landfill Cover Material 8 6.3 Recycling of burned clay products 8 7.0 Recycling of other materials 9 7.1 Waste Rubber as Aggregate Replacement 9 7.2 Aggregate Replacement with Pulverized Ash 9 7.3 Blast furnace slag aggregates 10 7.4 Use of incinerated ash 11 7.5 Use of glass in construction. 11 8.0 Conclusion 12 9.0 References 13 Sustainability in the Construction Industry - An appraisal of Recycled materials. 1.0 Abstract The demand for better infrastructure structure systems have led to large scale consumption of all types of building materials. And , this increased demand for building materials have caused huge impact on the environment in the form of natural resource depletion and escalated energy demand for the production. Thus to sustain the growth of building industry it has become inevitable to search for alternate solutions that causes less impact on the environment. One of the ways of attaining this objective is by using the recycled materials for construction activities. The objective of the thesis is to analyze the potentiality of material recycling to ensure the sustainability of building industry. The current practice and research initiatives in the recycling of demolition wastes and other solid wastes for different purposes in the building construction is also presented in this report. 2.0 Introduction The term "sustainability" was related to the regional development process by Gro Herlem Brundtland in the book 'Our common Future' based on the careful assessment about the environmental aspects of every human endeavor on earth. The objective then was to have a balanced view of all the development process which included not only the environment but also the health, social aspects, economics, politics , technology etc. In line with these, sustainable building construction was evolved that aims in the promotion of infrastructural systems with least effect on the environment like, very low energy consumption, controlled natural resource utilization, lesser social and psychological effects besides a harmonious existence with other living and non-living entities around it. One of the important ways to ensure the sustainable practices of building construction is to have proper recycling strategy to minimize the resource consumption. The major reusable portions of different types of construction materials are given in the table 1. Table 1 Reusability of building materials (WebUrbanist, 2007) Type of the materials Reusable potential Steel 100 % of the steel used in the building could be reused. The different materials produced are reinforcing bars, meshes and sections. Aluminum 100 % of the material could be is recycled. Timber Though structural reuse is very limited, timber remains could be used for the preparation of organic mulch. Concrete In the case of unset concrete, the proper washing could help to separate the aggregates from concrete. The hardened concrete would be reused as aggregate new concrete works or road base etc. Brick & Tiles Less damaged pieces would be directly reused after cleaning. In the case of broken parts they could be crushed and reused as aggregate or along with the cement , being a pozzolanic material. Gypsum Shall be recycled in the plastic board. Plastic It could be easily reused after powerdering and reducing the size to granulated ones. 3.0 Reusability as sustainable solution. One of the major issues of sustainability facing the construction industry is the dwindling rate of the natural resources. All the structures constructed across the world needed concrete - which is a well-proportioned mixture of cement and aggregates. The rapid increase in the infrastructure development initiatives have led to large scale consumption of concrete which have indirectly added pressure on the environment for the supply of the aggregates. When the supply of natural aggregates turned short, the industry decided to crush the parent rocks to prepare the manufactured aggregates. The manufactured aggregates too had its own problems due to the improper quality control in the production process and the poor choice of rock deposit for the manufacture of aggregates. Even the supply of manufactured sand is found inadequate to meet the aggregate demand for construction process. The aggregate replacement systems in concrete have been in vogue as a long-term solution for the aggregate crisis and also to ensure sustainability in the construction process (Chang, et al, 1999). Further, the building construction is considered as a cyclic process, which consists of either demolition of old structure at the site and constructing newer structure in its place. Thus, clearing of the debris or excavation of soil that adds up to some of waste material which need to be integrated with the aggregate demand experienced by the industry. Thus the reusability of these materials depends on the characteristics of the demolition wastes. Typical composition of demolition wastes that are characterized based of different field studies are given in table 2. Table 2 Typical composition of demolition wastes (Dickie, 2009) Particulars Percentages Soil 45 Sand and gravel 18 Concrete 10 Brick 10 Bituminous material 10 Others 4 Wood 3 Thus identifying the potential reuse for these materials could result in lesser volume to be disposed and also simultaneously ensures saving in the procurement cost of materials in the newer construction due to maximizing the reuse of the waste materials (Bossink and Bouwers, 1996). In addition , such initiatives would also lead to the significant reduction in the volume of landfill and local disturbances caused in the form of noise, vibration and dust . 4.0 Aims & Objectives. The broad objective of the thesis is to explore the reuse possibilities of construction and demolition wastes in the newer constructions and also to evaluate the aggregate replacement in concrete by reusing the alternate materials that have problems for disposal. The data obtained in the study would be very helpful to arrive at the pragmatic steps to evolve comprehensive measures to ensure sustainability of building construction. Also this initiative would help to identify the major research issues that need to be addressed to improve the acceptability and reliability of reuse materials in the infrastructure promotion programmes. 5.0 Initiatives to enhance the acceptability of reuse concepts. Along with the efforts made to increase the reuse rate of demolition wastes, adequate precautions are also being taken by certain nations to guard against any adverse impacts in future. Though Norway is blessed with abundant supply of low cost natural aggregates , considerable progress was achieved in the use of recycled aggregates derived from construction and demolition wastes (Petkovic et al, 2004). The regulatory authorities there have framed necessary guidelines for the use of recycled materials in the road construction, where huge quantities of demolition wastes were required. As a result, the problems like leaching from the materials used, could be arrested by framing appropriate guidelines for practice. These measures would help to accelerate the acceptability of recycled materials further in this country due to the presence of strict guidelines for the use of waste materials in construction (Petkovic et al, 2004). While, in United States, the refusal by the Municipal landfill authorities for construction demolition wastes and higher tipping charges compels to identify reuse and recycle potential for building material and other construction wastes. by municipal solid waste landfill operators to accept the construction and demolition waste in addition to the very high tipping fees charged by them have forced the regional authorities to evolve systems to increase the demand for secondary aggregates. Authorities of regional administration were very confident to attain these objectives by framing proper strategies for waste recycling operations . It is reported that by following the properly planned strategies the construction and waste recycling operations could certainly be made reliable (Peng, n.d.). The documents pertaining to the assessing the environmental aspects in the procurement of construction and demolition wastes is conducted among both the public and private clients in Sweden. The specific details regarding the type of building material, contractors environmental contribution, aspects pertaining to ecology and construction methodology were the major ones being assessed (Sterner, 2002). The survey which was conducted as structured interviews revealed that the process being implemented are uncomplicated and everyone could easily understand the environmental impact of the building material. This shows that the positive public perception about the ability of system to monitor the impact of any issue arising from recycled materials could strengthen reasons for using the recycled materials (Sterner, 2002). In another case reported in Australia, proper goal setting and feed back interventions primarily for timber and concrete waste streams have helped to reduce the volume of solid wastes significantly in a construction process. The periodic performance monitoring coupled with the preparation of general index for material usage efficiency and recycling indices have increased the reuse rate of demolished materials (Lingard et al, 2001). The significant change in the attitude of people towards high consumption rates in construction process could be achieved by proper awareness creation exercises. Thus the field study undertaken to assess the importance of such activities have revealed that selective choice to use materials having less embodied energy have resulted in the wider choice for recycled materials (Treloar, 2003). 6.0 Experience on reuse initiatives The different type of initiatives have been adopted across different regions to increase the material reuse in the construction process. The usage of sophisticated machines and equipments have helped to recover materials with less damage that could be reused without any problems in the quality. Experience have shown that different types of building units like hollow concrete blocks could be reused successfully. Also, the steel bars and other related materials as scrap could also be taken into the industrial units for reuse while manufacturing. According to US EPA (2009) the various measures proposed in this connection are as follows Converting the green waste into valuable materials like compost. The reusing the concrete and asphalt for sub-base in road building. Recycling he metal wastes by selling it off to scrap metal dealers. Bricks being reused for landscaping applications 6.1 Production of Secondary Aggregates The demolished waste materials could be screened and crushed to form secondary aggregates that satisfy the building regulations enforced by various regional governing bodies. The production of secondary aggregates in such form could also be used as topsoil for landscaping if they are unsuitable for construction purpose. These types of plants have proven to supply large quantities of materials in limited period of time. In one such cases reported Ascot environmental was able to supply nearly 80000 tones of materials to Jersey Marine site with in a period of one month (Stennor environmental services, n.d). 6.2 As Landfill Cover Material All engineered landfill units needs huge quantities of rich organic cover soils to be spread over the filled landfill matter. The demand for huge volume of the soil is thus causing severe pressure on the environment. The exploration of a suitable substitute material have finally resulted in the identification of alternate daily cover from the recycled demolition wastes. Materials like construction and demolition waste, ash and cement kiln dust etc were found suitable for the preparation of alternate daily cover material (Recycle guy, 2009). 6.3 Recycling of burned clay products The process of recycling of important clay products for building construction is an age old practice. Good quality burnt bricks and tiles often recovered from the demolition of old buildings could find a possibility of reuse in the newer type of constructions. Stills these methods are not without challenges. The bottlenecks encountered in the recycling process of bricks are as follows (Recycled burnt clay, n.d.). (i) The quality of bricks varies considerably across regions and hence to have a judgment of the recycled masonry structure constructed from brick masonry is very difficult exercise. (ii) Cleaning of brick is a cumbersome exercise. The mortar dust present on the bricks could result in poor adhesion between brick and mortar in reused construction and results in poor performance of the structure. (iii) High labor cost component involved in all the above process lead to higher cost of recycled bricks than the purchasing new ones. But it can be readily used in the road construction as a filling or surfacing materials. Also the presence of reactive alumina in the bricks makes suitable pozzolanic materials. In properly ground form they could be used in combination with lime to prepare a binding materials or in combination with cement for the preparation of mortar and cement (Recycled burnt clay, n.d.). 7.0 Recycling of other materials 7.1 Waste Rubber as Aggregate Replacement Large quantities of rubber in the form of used waste tyres are often dumped and discarded that often lead to environmental problems and unhygienic conditions. Thus research is undertaken to explore the possibility of using the rubber shredded to the sizes of fine aggregates that could be used as a replacement of normal aggregates in concrete (Skripkiunas et al, 2007). Earlier research findings have shown that such type of replacements could give considerable advantage in the resistance to frost and ice melting salt. Also the advantage of adding rubber based elastic aggregates on the elastic properties of concrete under static and dynamic loads are also reported and rubber aggregate concrete showed higher ultimate strain before failure. The deformation characteristics of tyre aggregate concrete showed that they have higher set plastic deformations than the ordinary concrete. Thus based on the tests results reported the shredded rubber wastes could be used as a aggregate replacement options (Skripkiunas et al, 2007). 7.2 Aggregate replacement with Pulverised fly ash Flyash is a waste material generated in the thermal power plants and causes considerable amount of environmental problems related to its disposal. Successful efforts have been made in finding different application for its reuse in the construction sector. The pozzolanic properties of the flyash have been made use of in the manufacture of pozzolanic cement. Recently, the efforts are made for its use as an aggregate for the concrete preparation. The experiments were conducted for this purpose to determine the mechanical properties of concrete by replacing the sand with class F flyash (Siddique, 2003a). The replacements by weight are made in five different percentages: 10, 20, 30, 40 and 50. The results of the tests performed to determine compressive strength, split tensile strength, flexural strength and modulus of elasticity were determined at 7, 14, 28, 56, 91 and 365 days. The results obtained showed that flyash could be successfully used as partial replacement of fine aggregate in structural concrete (Siddique, 2003a). Another set of experiments conducted showed that both the compressive strength and the abrasion resistance of the concrete increased with the increase in percentage of replacement with flyash. Nealry 40 percent increase in the abrasion resistance is reported to have achieved by replacing 40 percent of cement and with flyash (Siddique, 2003b). Attempts made in the replacement of cement with class F flyash too have demonstrated the possibility of 50 percent cement replacements in the manufacture of precast elements and also in the construction of reinforced concrete elements (Siddique, 2004). 7.3 Blast furnace slag aggregates Blast furnace slag is a non-metallic by product formed in the process of reduction of iron ore to molten iron in the blast furnace. They consist mostly of silicates, alumino-silicates and calcium alumina silicates. Depending on the cooling method used for molten slag different forms of slag products are formed. These are air cooled blast furnace slags (ACBFS), foamed or expanded slag, pelletized slag and granulated blast furnace slag (GBFS) (Blast furnace slag, n d). Granulated blast furnace slags are sand size particles formed from rapid water quenching. They exhibit cementitious properties when converted to fine particles by crushing or milling. They are found to be suitable for a partial replacement or as additive to Portland cement. Detailed research have been undertaken to asses the feasibility of using bottom ash (BA), granulated blast furnace slag (GBFS) and a combination of these materials as fine aggregate in concrete (Isa et al, 2007). The results obtained showed that GBFS and BA influenced the durability of concrete positively when used as aggregates. Their ability to reduce surface abrasion and less resistance to temperature effects are the factors that added to their merit. Thus the research results recommends the utility of using GBFS and BA to be used as alternate aggregates in concrete (Isa, et al, 2007). 7.4 Use of incinerated ash The utility of using the incinerated ash of the stabilized municipal solid waste along with natural aggregates has been investigated in detail. The flyash from the incinerator was washed , milled and then stabilized using cement - lime process . They are then reused as recycled aggregate for the preparation of mortar and concrete. The engineering characteristics of concrete prepared from such recycled aggregates did not differ much from the results reported with those of natural aggregates (Collivignarelli and Sorlin, 2002). The potential reuse of solid waste incineration ash is till unclear due to the possibility of toxicity leaching. The ash from these units are often classified as potentially toxic materials and hence detailed experimental evidence is required to establish their acceptability levels. It is observed that the bottom ash obtained from refuse-derived fuel incineration process have shown better acceptability for use as fine aggregate when compared with that that obtained from solid waste incineration carried out without any pretreatment. Still, the compressive strength values obtained from using RDF based bottom ash have shown a reduction of 23 percent in comparison with conventional type of aggregates (Chang et al, 1999). 7.5 Use of glass in construction. Waste glass is one of the most important waste materials found to have great utility in the concrete preparation. These materials were usually directly transported to landfills and its application in concrete preparation has certainly helped in the value addition. The major challenge in using waste glass aggregates is the alkali-silica-reactivity of glass in concrete. The recently published research results report different type of mitigation strategies for alkali-silica reactivity (Alhumoud et al, 2008). Most of the studies have identified the influence of factors like the type of glass, particle size of aggregate, presence of pozzolanic materials like flyash or lithium based inhibitors, addition of compounds in the form of air entrainers or shrinkage reduction agents and fibre reinforcements. The important findings reported are the 50 percent replacement of sand with fine glass particle having particle size less than 0.5 mm did not exhibit any adverse strength characteristics. Also, addition of 20 percent of flyash too showed good control on the expansion caused by alkali-silica reaction (Alhumoud et al, 2008). Thus the information presented by the researchers could give sufficient information for the preparation of concrete mixtures using glass fibre aggregates. In an another set of experiments glass articles were tested for the replacement as a binder. In the case of such experiments the replacement as binder was tested for the proportions of 10 %, 5%, 20% and 30 %. Also, 100 % replacement of fine aggregate with the processed glass was also evaluated. The workability tests conducted on concrete prepared using natural sand and glass sand with different binder replacement levels gave 70 to 80 percent variations in results when compared with the control samples (Shayan and Xu, 2004). Interlocking of angular particles, suction established across larger particles in the presence of water and surface tension caused by the water on the glass particles are the reasons identified for the marked variation in the workability. In the case of strength tests, the concrete prepared from 100 percent replacement of fine aggregates by glass particles exhibited comparable performance with that of control sample (Shayan and Xu, 2004). 8.0 Conclusion The importance of recycling process to increase the sustainability of construction is gaining momentum day by day. The analysis conducted in the report have clearly established the supportive role that governments across different countries have initiated to create wider acceptance of these concepts. Further, necessary environmental guidelines for the reuse of different types of waste materials too need to be evolved for large-scale use of the recycled materials. In addition to the issue of sustainability, the recycling industries are said to have higher job creation potential. The available information have shown that re-use jobs in construction could generate 8.7 jobs every 1000 tones of wastes handled, which is said to be 9 times more than traditional recycling jobs and 38 times more than the landfills and incinerators could ensure (The reconstruction centre, n. d.). Thus it could also soon turnout to be one of the largest employment potential areas in the construction industry. 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