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In this chapter, it will discuss and study into the commonly used which is conventional and traditional materials for bricks production in current construction industry, as according to Thomas (1996), currently in over the world, there got multiple types of choice in bricks manufactured from wide range of material, but yet in western world, bricks are usually produced by these common material such as fired clay, calcium silicate which known as sand lime and flint lime or concrete. Hence 3 types of commonly traditional material in term of properties and details will be highlighted in this chapter which is calcium silicate bricks, concrete bricks and clay bricks. Moreover, this chapter will also further discuss and look into several types of recycling materials which is potential for bricks production such as bottom ash and fly ash, recycled fine aggregates and sea sand and etc. In accordance to that, comparison in all aspect between the traditional and alternative recycling materials used to produce bricks will be discuss and describe in order to find out the difference in between their characteristic.
2.2 Conventional and traditional materials for bricks production
2.2.1 Clay Bricks
According to Yvonne (1996), she mentioned that these clay bricks are consider as one and only most efficient materials which has been widely used in terms of their energy consumption. Clay brick can be consider as the one of the type that are most commonly used bricks and application by contractors in construction industry nowadays, in Malaysia construction these type of clay bricks in term of usage and application has to be refer to BS 3921:1895. By referring regard with BS 3921:1895, the work size dimension of clay brick had been set to 215x102.5x65mm while coordination size is 225x112.5x75mm, work size is consider as the actual size of brick that should conform within specified permissible deviation while coordination size provide the meaning of the size of coordinating space allocated and specified to a brick including allowances for joints and tolerances (Horng 2010).
Clay bricks are mainly produced from the natural material which is fired clay that consist a wide range of different colour and textures. They can be manufactured in many different shapes, sizes and strengths, in fact in term of properties such as water absorption, suction rate and compressive strength also can be control and produce. These properties are determined mainly by the kiln, method of forming the bricks in specific shape whether by manually moulding or extrusion and also type of clay used (Thomas 1996). Basically there are three varieties of clay bricks available which are Common bricks, Facing bricks and Engineering bricks. According to Taylor (1994), common bricks are ordinary bricks which have no special claim and design to give an attractive good finished appearance and high strength, which in fact in general also consider as the cheapest bricks available. While for facing bricks are specially designed and made to give an attractive appearance which was free from imperfection that require extra rendering or plaster to the surface such as cracks. Whereas engineering bricks was consist the most highest density and well fire which are designed primarily with strong vitreous body for strength and durability, due to the more complicated process to produce these bricks hence it price also cost higher than the other types.
Figure 2.1: Common bricks
Common Brick - Product Code: Mbc2002Common Brick - Product Code: Mbc2011Common Brick - Product Code: Mbc2024Source: The Matching Brick Company (1991) , viewed 15 July 2012, <http://www.matchingbrick.co.uk/products.html#engineer>
Figure 2.2: Facing bricks
Stock Facing Brick - Product Code: Mbc4006Waterstruck Facing Brick - Product Code: Mbc5001Waterstruck Facing Brick - Product Code: Mbc5016Source: The Matching Brick Company (1991), viewed 15 July 2012, <http://www.matchingbrick.co.uk/products.html#engineer>
Figure 2.3: Engineering bricks
Engineering Brick - Product Code: Mbc1001 Engineering Brick - Product Code: Mbc1002 Engineering Brick - Product Code: Mbc1008Source: The Matching Brick Company (1991), viewed 15 July 2012, <http://www.matchingbrick.co.uk/products.html#engineer>
Manufacturing technique for the production of clay bricks have been evolving from initially which is by hand moulded processes to modern mechanization. At present according to Bas (1999), brick productions consist of five basic stages that can be found and allocate everywhere around the world, each of the operations are interdependent and brick will follow through these stages in a way designed specifically to suit raw material used and the final product. Figure 2.4 illustrate the main stages in clay brick manufacture.
Figure 2.4 General flow of materials in brick production Source: (Bas 1999, p. 5)
As show in Figure 2.4, the first stage is clay preparation, during this stage when clay are being digging out, it is prepare by crushing and mixing until uniform consistency and in order to make clay suitable for brick making, it must be mixed with water so that to increase plasticity, before it is transfer toward brick moulding machine, few day resting and left alone is necessary. Bricks moulding technique is designed to suit the moisture content of clay, bricks can either be moulding through hand or machine, normally the usually used method used to increase moisture content as stated by Taylor (1994) are semi-dry process, stiff plastic process, wire cut process and soft mud process. After moulding, the brick will undergo the second stages which is Drying stages, it is carried out to let the humidity or moisture content inside the bricks to run free or escape in order to prevent the wet brick cracks inside when temperature is rapidly increase during fire, in fact the process also enables and assist the firing temperature rises and increased smoothly without problem such gases and vapour are trapped within the bricks that are namely Bloating. Then following stage is pre-heating where the bricks are heated constantly but slowly mainly to avoid cracking, during the firing stages, the purpose is to let the brick increase in strength and decrease the soluble salt content by ensure localized melting sintering of the clay, there are 4 main processes which are clamps, continuous kilns and tunnel kilns. The last stage which is cooling stages, the bricks are stack and cooled down in kiln after fired, this stages is necessary because bricks can result in crack inside which will indirectly cause loss of strength when temperature is rapid rise and then rapidly cool down.
According to Richard and Kreh (1990), all properties of structural clay product such as brick are affected by the composition of the raw material use and the manufacturing process. The important properties are strength, durability, colour, texture and absorption. In fact, each brick used in construction are required to be tested first before proceed to the next stage in masonry construction.
Sadek and Roslan (2011) stated that compressive strength of brick is important as an indicator of masonry strength and indirectly brick strength become an important requirement in brickwork design. Strength is known as resistance of brick needed to increase in term of load when stress constantly appeared on it before it breaks. For the properties of durability of clay brick is much more likely to be a problem than its strength since in most situation, clay bricks are very much stronger than is required structurally (Taylor 1994). Colour and finished of the clay brick are determine by the chemical composition of natural clay and mineral which added to the natural clay, another factor that influences or affect it colour is depends on how well the temperature during firing being control in kiln clay burned period (Richard and Kreh 1990). Whereas for texture properties in bricks, it is the arrangement of particles of raw materials in brick such as hard and smooth finish should had fine finish or texture, normally many textures can be achieve or obtained during the stiff mud process. Lastly for absorption, it may be an important property of clay bricks, since bricks that have very low absorption are invariably of high durability, Richard and Kreh (1990) argues that the water content of bricks must be correct to obtain the best result from combining of brick and mortar to form a wall. It is frequently ignored and forgot in construction which indirectly cause the strength and durability of the wall are affected.
According to William (2001) Fire Bricks which is also one of the clay mould bricks which using the refractory clay to produce is consider as a special bricks which can withstand and resist much more higher of heat and temperature. The bricks are mainly application for builder to construct lining chimney shafts, boilers and kilns or for those work activities or building which require excessive resistance toward heat. Eeydzah (2010) mentioned that even though these bricks are much weaker, but compare to other the advantage is much lighter, easier to form and produce and also insulation properties is way much better than dense bricks.
2.2.2 Concrete Bricks
According to Hafiz (2010), the concrete bricks are usually and one of the most used in the construction industry as wall panel and partially drains. Concrete brick are produced from a controlled mixture of Portland cement and aggregates in sizes, colours, and proportions which are similar to clay bricks that can be served as a purpose of loadbearing or non load bearing (Beall 1993). Normally these concrete bricks production need to fulfill and comply with all the appropriate requirements as stated in BS6073: Part 2 1981 specification for precast concrete masonry unit (Thomas 1996).
Horng (2010) stated that the concrete is hardened by conventional water curing process or special compression method whereas BS 1180 mentioned that the minimum requirements and the classification of these types of bricks are common with sand-lime bricks. William (2001) stated there have another type of concrete brick which is different in term of material of production, instead of cement and sand, it is actually made with cement and furnace clinker or fly ash. These bricks are built into various positions in walling mainly to help and allow those especially internal housing decoration such as picture rails, skirting, serving hatches and door frame can be secured by using nailing and nailed into them. Normally the natural colour of concrete bricks are cement colour which is greyish, but nowadays pigments are allowable which then give a range of colour such as of brown and reds are produced (Yvonne 1996).
Taylor (1994) also mentioned that concrete bricks BS 6073 are relatively one of the concrete brick that are recently introduced, these bricks are comprising well compacted, low workability concrete mixes of appropriate aggregates size, leading to products of high strength and durability. In fact the properties such as colour and textures can be control which can give a final appearance very similar to clay bricks, and are most important are it is free from efflorescence but due to different movement characteristic, these type of bricks are suggested not to bond with other brick types as it will affect their structural strength and dulability.
2.2.3 Calcium Silicate (Sand-Lime) Bricks
According to Taylor (1994), these bricks are made by combine and blending the finely ground sand or flint and lime together uniformly in the approximate ratio of 10:1. After that the semi dry mixture is then pressed into mould in shape and cured in an autoclave for two or three hour to speed the chemical hardening. The finished of these bricks are quite natural and uniform, the colour of the bricks is darker when wet than when dry. Thomas (1996) specified that all these bricks requirements are required to comply to BS 187:1978.
Beall (1993) defines that calcium silicate brick are the most widely and extensively used by contractors in industrialized countries such as Europe, Russia, Australia and United States, the main reason is because the suitable siliceous sands are more readily available compare to clay in their country, in fact it has been broadly manufactured and produces in United States in the early year of 1900s. Taylor (1994) stated that the main properties of calcium silicate bricks are:
A high degree of regularity, with a choice of surface texture ranging from smooth to rustic.
A wide range of colour as pigment can be added which then available to produced various type of colour
Very low soluble salt content, hence is fine with efflorescence
Relatively higher moisture movement compare to other bricks
Compressive strength with range 7-50 N/mm2 (BS187)
Good overall durability in clean atmosphere, but they may deteriorate slowly in polluted sulphur containing atmosphere.
2.3 Recycling materials for bricks production
2.3.1 Bottom ash and fly ash
According to Safiuddin (2010), Fly ash (FA) and bottom ash (BA) are produces as a by-product from municipal solid waste incinerators and coal fuelled power stations, it is a highly dispersible powder which contain mainly aluminosilicare and derriferrous glassy spherical particle and irregularly shaped grains of amorphous clay, mullite quartz and unburned metamorphic fuel whereas BA consists of irregular particles that can be add up to 10-15mm in size. The chemical compositions of both ashes from same power plant are similar.
Fly ash which obtained from coal combustion is frequently used in add into concrete due to cost saving by substitute the material of portland cement, the pozzolanic properties of fly ash can improve the strength of concrete which can be found during curing at 38 Degree Celsius that it greatly accelerates its contribution to the strength of concrete (Orchard 1979). Lingling, Wei, Tao and Nanru (2005) found out that fly ash can actually improves the compressive strength of bricks and increase their resistant toward frost attack whereas Cicek and Tanriverdi (2007) also realized the positive effect of fly ash on the compressive strength of bricks during his studies research.
According to Kumar (2002), he clearly stated that sufficient strength which comply to the minimum requirement of bricks can be achieve in produce brick by using these fly ash hence it have potential to use as substitute of conventional clay bricks and blocks. Naganathan et al (2012) also defined that the strength of bricks increase with the increase in fly ash, in fact he conclude that bricks of good quality can be made by using bottom ash and fly ash whereby contributing to sustainable building. Figure 2.5 clearly illustrate that the evidence and application of both of fly ash and bottom ash in real construction, from here we tend to believe that both fly ash and bottom ash since years ago already is one of the waste materials that can be trusted and widely apply by other country to recycled and apply back to construction to produce various type of material such as bricks.
Figure 2.5: Application of waste material in real construction.
Souce : (Safiudin 2010, p. 1960)
According to Naganathan (2012), there got a lot of advantages of using bottom ash and fly ash in brick making, mainly can consuming large volume of waste which then indirectly reduced the environmental problem which cause by dumping these waste in landfill and ash pond, moreover it also help enhance the properties and performance of bricks, in fact it do contribute to sustainable development and assist developers to get green building index points.
2.3.2 Recycled fine aggregates
According to Ismail and Yaacob (2010), the initially and inventive use of recycled fine aggregates began and start at the end of World war II during the time when the nation of European fed problem in rubble material disposal. Which then the RILEM Technical Committee take an important steps of publishing in promoting the recycling aggregates which finally end up followed by several number of researchers around the world.
In the studies research of Ismail and Yaacob (2010), it stated that brick dimension is influenced by material content and the density of constituent materials, their study focus on average brick dimension which was calculate and evaluated from 10 samples each group regarding length, width, depth, area and volume. Figure 2.6 show the summarized of average brick dimension and clearly stated and summarized that bricks with recycled fine aggregates had an uniform size and surface area similar to bricks with conventional materials.
Figure 2.6 The dimensions of brick specimens
Source : (Ismail and Yaacob 2010, p. 880)
188.8.131.52 Brick Density
The density of brick specimen was calculated by dividing the weight with volume. In figure 2.7 stated that the density of control bricks was 2032.3 kg/m3 which mean the result of the density for brick content 50% recycled fine aggregate slightly increase 1.7% if compared with control brick. Conclusion in the figure show average density of brick by using recycled fine aggregates are much lower compare to control brick, even the most lower can be observed in brick with 100% content of recycled aggregates which reduce 3.5 % ( Ismail and Yaacob 2010).
Figure 2.7 The average density of bricks with recycled fine aggregates
Source : (Ismail and Yaacob 2010, p. 880)
184.108.40.206 Compressive strength
The compressive strength of a material determines its load carrying capacity before stress apply on it and become failure. British Standard Institution states that the compressive of bricks should not be less than 7N/mm2 (Ismail and Yaacob 2010). The figure 2.8 illustrated the detailed result of compressive strength of all bricks types
Figure 2.8 The average compressive strength of bricks with recycled fine aggregate
Source : (Ismail and Yaacob 2010, p. 881)
It can be seen from the figure, the result of compression strength of control brick is 12.32N/mm2 which mean the overall finding reveal that with additional of recycled fine aggregate can instantly increase the compressive strength. In the report, (Ismail and Yaacob) conclude that based on the test result, the bricks produced with recycled fine aggregates show positive result in each test and some even similar to brick with conventional natural material hence overall it can be utilized in brick mixture as good substitute for natural sand.
2.3.3 Sea Sand
According to Hafiz (2010), use of river sand in Malaysia is very widespread in construction industry, in order to protect the environment of river and prevent erosion or flooding, seas sand are suggested to be one of the substitutions to replace river sand. The composition of sand varies from place to place depends in the sources and condition of the local rocks. Sand is classified as a unique raw material for construction industry due to allocation for obtaining bulk loads of sand for construction work.
Sea sand has become a potential resource yet also consider as waste material which are capable to supply fine aggregates for domestic construction usage, in accordance to that, applications of sea sand is more economic by using river sand. Sea sand mostly contain more content of salinity or sodium chloride which may directly cause or affected the durability of structural if being ignored and without treated which then result in swilling, precipitation, sulfating and other adverse consequences. Hence precautions must be taken to eliminate to avoid unwanted hazard (Hafiz 2010). Rahman (2010) argues found out that sea sand contains significant â€œimpuritiesâ€Â such as magnesium and sodium chlorides which lead to corrosion in iron, in fact in past research, sea sand is considered unsuitable for construction industry because of its small size and unless the chloride content that caused rusting is extract or reduced.
220.127.116.11 Sieve Analysis Sea Sand
The sieve analysis of sea sand is to determine the gradation of sea sand such as the distribution of aggregates particles, by size within a given sample. There are many types of sieves depends on different sieve size. The figure 2.9 show the analysis of sea sand that use as concrete aggregate.
Figure 2.9 Average Granulometric Curve of typical sea sand used as concrete
Source: (Hafiz 2010, p. 8)
The figure show that percentage of passing sea sand to get 100% on sieve analysis and sieve size is quicker than other material. This happen due to sea sand is a fine aggregate that less retain in sieve size. As a basic material in brick mixture, a classification of aggregate is very important as it will affect the strength of brick, the advantages of this process ensure the size of apertures decrease in logarithmic fashion.
During current situation, enormous quantities of domestic, industrial and construction waste are generated annually throughout the country, instead disposing all of them, this research and chapter is actually give an further detail and look into several types of potential recycling material which able to used as substitution or replacement of natural resources in brick productions. After go through this chapter, it can be noticed that even though many alternative potential recycling waste solid has been introduced but yet the awareness of public toward scarcity of natural resources is still very low, it proved by most of the traditional material such clay brick, calcium silicate bricks and concrete bricks are still among the favourite choices of construction industry, bulk by bulk quantities of these material are being produced which indirectly caused depletion of related natural resources. This chapter not only showed many advantages such as avoid negative impact toward environment by using the recycling waste solid to produce bricks instead of dumping them in open fields,in fact it also prove that the result and properties of brick manufactured by recycling material is comparative, some even prove more better in term of economic and strength, so why still hesitate on the choice ?