ADVANTAGES AND DISADVANTAGES OF USE OF BRICK DUST AND FLY ASH AS A REPLACEMENT OF FINE AGGREGATES IN SELF COMPACTING CONCRETE

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1 International Journal of Technical Innovation in Modern Engineering & Science (IJTIMES) Impact Factor: 5.22 (SJIF-2017), e-issn: Volume 4, Issue 7, July-2018 ADVANTAGES AND DISADVANTAGES OF USE OF BRICK DUST AND FLY ASH AS A REPLACEMENT OF FINE AGGREGATES IN SELF COMPACTING CONCRETE ABSTRACT JAVAID IQBAL Research Scholar, Department of Civil Engineering, Gurukul Vidyapeeth Institute of Engineering & Technology, Banur This research work reports the potential of using Brick Dust Waste (BDW) and fly ash as a partial substitute of fine aggregates in the development of self compacting concrete. As we know that everything has some advantages as well as some disadvantages as nothing is perfect in this universe. So the main focus of this study is to determine whether the use of brick dust and fly ash as a partial replacement of fine aggregates in self compacting concrete is useful or not, and what are the limitations of using fly ash and brick dust as a replacement of fine aggregates in self compacting concrete. The study is also aims to focus at the measures which may be helpful to overcome the above mentioned limitations if arrives. In this research the properties of fly ash and brick dust were also studied and were also compared with the normal compacted concrete. KEY WORDS Brick dust, Fly ash 1.0 INTRODUCTION (A). Brick Dust Waste (BDW) BDW is recycled waste materials that are sourced from the demolishing of fired clay brick buildings or the discarded by-product materials from the cutting of fired clay bricks into shape and sizes for the construction of chimneys, and other uses needing the use of fired bricks. This results in the disposal of BDW as an environmental problem of concern. BDW has pozzolanic properties that enables it play an important role in the strength and durability of concrete, its use in concrete will alleviate the increasing challenges of scarcity and high cost of self compacting concrete and will help to strike a balance between the sustainability of the environment and the demand on construction due to the increase in population growth worldwide. In India the Brick dust is a waste product obtained from different brick kilns and tile factories. There is numerous brick kiln which have grown over the decades in an unplanned way in different part of the country. Tons of waste products like brick dust or broken pieces or flakes of bricks (brick bat) come out from these kilns and factories. So far, such materials have been used just for filling low lying areas or are dumped as waste material. Brick dust is a waste product obtained from different brick kilns and tile factories. There is numerous brick kiln which have grown over the decades in an unplanned way in different part of the country. Tons of waste products like brick dust or broken pieces or flakes of bricks (brickbat) come out from these kilns and factories. So far, such materials have been used just for filling low lying areas or are dumped as waste material. Due to availability of soil and fuel, demand and market conditions, the scale of production varies across India. Bricks are still produced using traditional techniques, involving manual labour and inefficient methods. Processes like firing and drying are done in open air, thus making it season-dependent. IJTIMES-2018@All rights reserved 930

2 Punjab, Haryana, Uttar Pradesh, Bihar and West Bengal are the major brick producing states in India. These states are account for about 65 per cent of the production. The brick kilns are located in clusters around main towns and cities with a production capacity of over 2 10 million bricks per year. Usually, the kilns operate for 6-8 months. Because of seasonal dependencies, the production process is brought to a virtual standstill during monsoon. Brick production in northern mountain regions in India such as Srinagar, Jammu and Dehradun is very low, and limited to the valleys. Table 1.1: Estimated numbers of kilns in major brick producing states in the Gangetic plains S. No States Typical Production Capacity of a Kiln (Number of bricks/year) Total Number of kilns 1 Punjab 4 8 Million Haryana 4 8 Million UP 2 8 Million Bihar 2 5 Million West Bengal 2 5 Million Brick dust as mineral admixture has the ability to react with lime in presence of moisture to form hydraulic products. As Portland cement liberates lime during hydration, in course of time, this liberated lime is leached out making the structure porous (Samanta et al., 1997). Due to acidic environment, CO 2 reacts with Ca(OH) 2 and forms calcium carbonate and water, then leaches out the whitish substance. Portland cement + water Ca(OH) 2 + CO 2 C-H-S (Glue) + Ca(OH) 2 (Fast Reaction) CaCO 3 +H2O In cement, mineral admixture mixes with liberated lime that in turn reacts with mineral admixture forming additional number of hydraulic compounds, reinforcing the hydraulic properties of cement itself. The reaction is as follows: Pozzolana + Ca(OH) 2 + water C-H-S (Glue) (Slow Reaction) The slow rate of reaction between mineral admixture and liberated lime coupled with the decrease in the portion of cement affects the hydraulic properties in the early age. But in the course of time, the mineral admixture reaction products contribute their share to improve the rate of hydration and consequently the strength properties of the concrete. The composition of brick powder is listed in Table 3.9. Table 1.2 Composition of Brick Powder Material Brick Powder Al 2 O % CaO 24.48% Fe 2 O % LOI 0.66% MgO 8.56% MnO 0.08% Na 2 O 1.02% P 2 O % SiO % SO % TiO % Cl 108 ppm K 2 O 1.84% IJTIMES-2018@All rights reserved 931

3 (B). FLY ASH Fly ash is a byproduct from burning pulverized coal in electric power generating plants. During combustion, mineral impurities in the coal (clay, feldspar, quartz, and shale) fuse in suspension and float out of the combustion chamber with the exhaust gases. As the fused material rises, it cools and solidifies into spherical glassy particles called fly ash. Fly ash is collected from the exhaust gases by electrostatic precipitators or bag filters. The fine powder does resemble portland cement but it is chemically different. Fly ash chemically reacts with the byproduct calcium hydroxide released by the chemical reaction between cement and water to form additional cementitious products that improve many desirable properties of concrete. The fine residue from these plants which is collected in a field is known as fly ash and considered as a waste material. The fly ash is disposed of either in the dry form or mixed with water and discharged in slurry into locations called ash ponds. The quantity of fly ash produced worldwide is huge and keeps increasing every day. Four countries, namely, China, India, United State and Poland alone produce more than 270 million tons of fly ash every year. One of the chief usages of volcanic ashes in the ancient ages were the use of it as hydraulic cements, and fly ash bears close resemblance to these volcanic ashes. These ashes were believed to be one of the best pozzolans (binding agent) used in and around the globe. The demand of power supply has exponentially heightened these days due to increasing urbanization and industrialization phenomena. Subsequently, this growth has resulted in the increase in number of power supplying thermal power plants that use coal as a burning fuel to produce electricity. The mineral residue that is left behind after the burning of coal is the fly ash. The term fly ash has been defined as "the finely divided residue resulting from the combustion of coal or finely ground waste and is carried in the gas flow." However, this definition does not include, the waste resulting from: (1) burning municipal waste or some other type of waste with coal; (2) injecting lime directly inside the heater to remove sulfur; or (3) the burning of trash industrial or municipal incinerators commonly called "incinerators ashes." Basically, four types of coal used in thermoelectric power stations are : anthracite, bituminous, sub-bituminous and lignite, which varies mainly in the calorific value and the amount of fixed carbon. The type of coal used influences the type of fly ash obtained. Due to the improved efficiency of burning, coal is crushed into thinner particles, with 75% passing the # 200 mesh (75 microns). The organic compounds are oxidized and volatilized during combustion and ash particles melt into the combustion zone of the furnace. The pozzolanic activity of fly ash is highly influenced by the quantity and composition of the glassy phase present. The low calcium fly ash, a product of calcination of bituminous coal, containing alumino silicate glass seems to be a little less reactive the calcium alumino silicate glass, present in high calcium fly ash. The crystals of minerals typically found in fly ash low in calcium are quartz, mullite (3Al 2 O 3.2SiO 2 ), sillimanite (Al 2 O 3.SiO 2 ) hematite and magnetite. These minerals possess no pozzolanic property. The mineral crystals typically found in high-calcium fly ash are quartz, tricalcium aluminate (3CaO.Al 2 O 3 ), calcium sulpho-aluminate (4CaO.3Al 2 O 3.SO 3 ), anhydrite (CaSO 4 ), free calcium oxide (CaO), free magnesium oxide (MgO) and alkali sulfates. With the exception of quartz and magnesium oxide, all mineral crystals present in the high calcium fly ashes are reactive. This explains why compared to low calcium fly ash, the high calcium fly ashes are more reactive. The physical properties & chemical properties of fly ash are listed in Table 1.3 and Table 1.4 respectively. Table 1.3 Physical characteristics of Fly ash Test Particulars Results Specific Surface Area (Blaine Fineness) 320 to 360 (m 2 /kg) Specific gravity 2.00 to 2.05 Bulk density 750 to 1800 (kg/m 3 ) Color Grey or Tan Physical form Powder form Class F IJTIMES-2018@All rights reserved 932

4 Table 1.4 Chemical Composition of Fly ash Constituent %age Silica SiO 2 58% Alumina Al 2 O 3 21% Ferric Oxide Fe 2 O 3 3.8% Titanium Dioxide TiO 2 0.8% Manganese Oxide MnO 0.4% Calcium Oxide CaO 7.0% Magnesium Oxide MgO 1.5% Sodium Oxide Na 2 O 0.6% Potassium Oxide K 2 O 0.9% Iron FeO 0.2% Phosphorus P 2 O 5 0.1% Alkali metal s Oxide 1.1% Sulphur Trioxide SO 3 1.1% Magnesium oxide MgO 0.4% Loss on Ignition 4.1% 2.0 DISADVANTAGES OF FLY ASH AND BRICK DUST AS A PARTIAL REPLACEMENT OF FINE AGGREGATES IN SELF COMPACTING CONCRETE (A). FLY ASH The quality of fly ash can affect the quality and strength of Cement concrete. Poor quality fly ash can increase the permeability of the concrete and cause damage to the building. Air Content In general, there is no difficulty in entraining air in high volume fly ash concrete % air can be routinely incorporated into high volume fly ash concrete mixtures. However, occasionally one may run into difficulty when the carbon content of the fly ash being used is high (> 4 %) or when activated carbon particles are present. The carbon content affects the air entraining agents and reduces the entrained air for a given amount of air-entraining agent. The carbon will absorb water. An additional amount of airentraining agent will need to be added to get the desired air content. Some fine fly ash results in a higher water demand due to increase in surface area If a fly ash contains an appreciable amount of carbon, it may be difficult to control the air content. Because of the very low water content, the slump of high volume fly ash concrete is low, and therefore, it is essential to use a super plasticizer when a high slump is needed for placement. Cold weather can have detrimental effects on concrete construction unless adjustments are made and precautions are taken to ensure acceptable performance. High volume fly ash concrete hydrates more slowly than an ordinary concrete. This factor, which increases with increasing fly ash replacement dosage, presents a problem in concrete construction where rapid stripping and turnaround are essential. Curing and permeability Concrete with 50 % Class F fly ash and moist cured in 5 C for 1, 3 or 7 days got lower 28 days strength than concrete with no fly ash. IJTIMES-2018@All rights reserved 933

5 (B). BRICK DUST * There may harmful ingredients presents in the brick dust which may retard the good properties of self compacting concrete properties. * The brick dust may also affect the slump flow of the self compacting concrete. * The quality of brick dust also affects the quality and strength of self compacting concrete. 2.0 CONCLUSIONS From the above discussion, we may conclude that the advantages of fly ash and brick dust are more as compare to disadvantages. The increase in the compressive strength, tensile strength and flexure strength is all possible due to the partial replacement of fine aggregates by brick dust and fly ash. So, in short we can conclude that the fly ash and brick dust have positive impact on the self compacting concrete. IJTIMES-2018@All rights reserved 934