International Journal of Modern Research in Engineering & Management (IJMREM) ||Volume|| 2 ||Issue|| 9 ||Pages|| 11-16 || September 2019 || ISSN: 2581-4540
Effect of Silica Fume and Fly Ash on Compressive Strength of Unfired Clay Bricks 1
Vishan Das, 2Aneel Kumar, 3Sheva Ram, 4Love Kumar 1, 2, 3
Department of Civil Engineering MUET jamshoro, Sindh, Pakistan 4 WWF-Pakistan
-------------------------------------------------------ABSTRACT--------------------------------------------------Readily available engineering materials are preferred in construction of different projects due to its low cost. Clay brick being cheaper and easily available is vastly used in developing countries like Pakistan. Even though clay bricks are largely used in Pakistan however no consideration have been exercised in the brick making industry to lower the use of brick making soil and enhance its compressive strength by using certain waste materials which possess clay like properties. This paper presents the results of a study made to assess the effect of Silica fume and Fly ash on compressive strength of unfired clay bricks. For that Silica fume and Fly ash were used in different proportions (from 2% to 10%) to the weight of clay soil to prepare the soil samples of 22cmĂ—11cmĂ—7.5cm and prepared samples were compared with conventional clay bricks of same site in terms of compressive strength. It was observed from results that compressive strength was increased at each different percent both of the materials. Hence obtained results suggest that there is potential to replace brick soil with either Silica fume or Fly ash to produce the unfired clay bricks with higher compressive strength.
KEYWORDS: Bricks, Clay, Compressive strength, Fly ash, Silica fume. ----------------------------------------------------------------------------------------------------------------------------- ---------Date of Submission: Date, 01 September 2019 Date of Publication: 20 September 2019 ----------------------------------------------------------------------------------------------------------------------------- ----------
I.
INTRODUCTION
Bricks are rectangular blocks made of clayey soil. In construction industry it is used in all types of walls, pavements and other elements of masonry construction. Bricks may be categorized in different classes and types based on quality of bricks, material used and size of the brick. Two basic types of bricks are Sun dried or Katcha bricks and Burnt/Fired or Paka bricks. The use of clay bricks in developing countries like Pakistan is inevitable due to its low cost and standing by availability, in turn it causes a big loss of useful land for the purpose of brick manufacturing. The area from where soil is dug out does not remain capable for irrigation purposes. To overcome this problem of soil erosion there is a need to reduce the use of soil for brick making purpose. Therefore, it requires some suitable materials possessing clay like properties to be added to the brick making soil to mitigate this hazard to a little extent in order to prevent the loss of our useful soil which can alternately be used for agricultural needs and also to increase its compressive strength and other physical properties. Lime stone dust, Wood saw dust, Fly ash, Water sludge, Silica fume, Rice husk ash, geo polymers, Wood aggregates, Bottom ash, Straw, Wood chips carpentry, Rice husk and Palm fiber, [1-13] are some of the materials whose successful use to replace the soil partially to manufacture bricks having physical and mechanical properties close to that of bricks made with clayey soil only has been studied by many scholars around the globe. The purpose of this study is to evaluate the effect of Silica fume and Fly ash on unfired clay bricks on ground with no laboratorial control in preparation of samples. 5 samples were prepared at each different percentage of each material in total 50 samples were prepared following the local traditional method of brick manufacture at local kiln site of a Village in District Umer kot, Sindh Pakistan, then after these brick samples with 5 conventional clay brick samples were taken to laboratory for compressive strength test.
II.
LITERATURE REVIEW
So much work has been done up to date on making of bricks by replacing some or whole portion of clay soil by some suitable waste materials and positive results have been reported, but its implementation in the brick making industry is nil in Pakistan and bricks are still being produced by using clay soil only.
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Effect of Silica Fume and Fly Ash on Compressive… Paki Turgut (2012) published a research paper on the use of Fly ash Silica fume and Lime stone powder in brick making without use of cement. The prepared samples were cured for 7, 28 and 90 days and were tested for compressive strength, flexural strength, water absorption, density, porosity and thermal conductivity. The results showed increasing trend in compressive and flexural strength with the increase of silica fume content in the mix, the compressive strength of these bricks at 20% of Silica fume were 23 and 26.5MPa after 28 and 90 days curing respectively. Hence material containing 20% Silica fume was satisfying mechanical and some physical properties such as; compressive strength, Flexural strength, density and water absorption hence it was compatible to load bearing and non load bearing concrete unit. It was also observed that production cost of these bricks was 6.4 times lower than that of traditional bricks [1]. Tabin Rushad S et al (2011) carried out experiments on Lime-Soil-Fly ash bricks. The major purpose of this study was to investigate the compressive strength and water absorption characteristics of above-mentioned bricks. Both type bricks hand molded and machine molded with different proportions of Fly ash, Soil and lime were tested and it was found that none of the bricks met all the characteristics of the standard values except that of made with 40% Fly ash and 60% Lime. It was concluded that change in percentage of soil did affect compressive strength unless Fly ash and Lime percentage was unchanged [2]. Badr El-Din et al (2012) presented research work on the use of Water sludge, Silica fume and Rice husk ash in brick making. All the three materials were used in different proportions, a few trials were made and optimum proportion was found at 50% Sludge, 25%Silica fume and 25% rice husk ash. The following conclusions were made based on the analysis of results: • Water treatment plant sludge can efficiently be used in brick manufacturing incorporated with other waste materials as, Silica fume Rice husk ash etc. • The chemical composition of Water treatment plant sludge was almost similar to the brick making clay. • The mechanical and durability properties showed that most of the brick samples of this research work were superior to the bricks available in local market. • The maximum percentage of sludge in the mixture was subject to the practiced sintering temperature Safeer Abbas, et al (2017) observed the effect of partial addition of fly ash to the brick clay on the mechanical and durability properties of burnt clay bricks. The fly ash was added from 5% to 25% with the increment of 5% each time. Total 150 specimens were prepared, by varying the percentage of fly ash by the weight of clay. The experimental results showed that compressive strength, modulus of rupture and breaking load decreased with the increase of percentage of fly ash content in the soil; however, the values were within permissible limits up to the 20% of fly ash for both compressive strength and modulus of rupture and up to 10% for breaking load. The efflorescence values were negligible at 5% and moderate at 20% of fly ash. Furthermore, it also was concluded that addition of fly ash up to 25% can reduce the weight by 18% and give the light weight bricks [4].
III.
MATERIALS AND METHOD
Brick Soil: Clayey soil is considered as most suitable for the manufacture of bricks. Clay is among one of the naturally occurring mineral material in abundant. Clay must possess some specific properties for its use in the manufacture of bricks. It should be plastic enough to be shaped and molded when water is added; also its mineral composition should be such that its particles fuse to gather when fired to a specified temperature. The chemical composition of clay varies from inch to inch in a pit. Its main compositional constituents are Silica, Alumina and Oxides of iron, the first two ingredients give strength to the bricks when fired and former are responsible for the variation in color of bricks. For this research work clayey soil present on kiln site was used as the base material. Silica Fume: Silica fume is a non crystalline and very fine by product obtained from silicon metal or ferrosilicon alloy produced in electric arc furnaces. This product is also in powder form having gray color somewhat resembling to Portland cement and fly ash. Silica fume exhibits cementious or pozzolanic or both properties. Like Fly ash this material is also largely used in cement concrete as partial replacement of cement, however its beneficial use in brick making as partial replacement of clay has also been witnessed through some studies.
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Effect of Silica Fume and Fly Ash on Compressive‌
Figure 1. Silica Fume Fly Ash: Fly ash is disposed off in large quantities. Fly ash is a non combustible portion of coal which is used in coal fired thermal power plants and it is obtained from dust collectors in powdery form. This byproduct possesses excellent pozzolanic properties and its use in cement mortar and concrete is well known, likely it can also be used in brick making soil to enhance over all properties of clay bricks. Due to very fine size of Fly ash particles it largely possess clay like properties in addition to that its pozzolanic properties give higher strength to the brick when mixed with brick making soil in a definite proportion, this fact has been revealed through many research works. In addition to that, it also makes the brick less pervious and durable.
Figure 2. Fly Ash
IV.
MATERIALS TESTING
Sieve analysis and Sedimentation analysis: Both sieve analysis and hydrometer test were used to determine the grain size distribution of all the materials used in this research work. The obtained results are presented below in Table 1. Table 1. Particle size distribution Sieve no. #4 #10 #40 #200 -
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Diameter (Âľm) 4.75 2.00 0.425 0.075 0.028 0.020 0.014 0.010 0.007 0.005 0.004 0.003
Soil 99.98 99.58 98.68 93.91 64.31 62.54 60.67 57.02 53.38 50.92 24.23 4.19
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% Passing Silica fume 100 100 93.74 22.96 9.33 4.78 2.41 1.37 0.23 0.23 0.23 0.23
Fly ash 100 99.93 97.06 71.77 37.44 20.92 1.79 0.28 0.28 0.28 0.28 0.28
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Effect of Silica Fume and Fly Ash on Compressive‌ Atterberg Limits: Shrinkage limit, Plastic limit and Liquid limit are collectively called as Atterberg limits. The results of tests for atterberg limits are given below in Table 2. Table 2. Atterberg limits Material Soil Silica fume Fly ash
Shrinkage limit 17.66 0 0
Plastic limit 26.52 79.70 66.00
Liquid limit 52.00 91.00 70.00
Plasticity index 24.48 11.30 4
Specific Gravity: Specific gravity is the measure of ratio of a substance to the reference substance, reference substance is mostly water. The specific gravity values for all the materials obtained are tabulated below. Table 3. Specific gravity test results Material Soil Silica fume Fly ash
Specific gravity 2.78 2.52 2.88
V.
RESULTS AND ANALYSIS
Compressive Strength: Compressive strength is the measure of load bearing capacity of any substance per unit area. Brick samples were subjected to the compressive load in universal testing Machine up to the failure load, then this load was divided by the face area of brick samples to get the compressive strength of samples. The compressive strength results are presented in the following sections Table 4 and Fig. 3-5. Table 4. Compressive strength values at different percentages for both materials Percentage of Materials (%)
2.0 4.0 6.0 80 10.0
Compressive strength of conventional clay bricks is 1.27 (N/mm2) Compressive strength of bricks at different percentages of Fly ash and Silica fume (N/mm2) Silica fume Fly ash 2.81 2.72 3.58 3.16 3.23 3.22 2.70 3.55 1.73 1.90
Figure 3. Compressive strength of Silica fume bricks
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Effect of Silica Fume and Fly Ash on Compressive‌
Figure 4. Compressive strength of Fly ash bricks
Figure 5. Comparison of Compressive strength for both materials
Figure 6. Prepared brick samples left for drying under Sun rays
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Effect of Silica Fume and Fly Ash on Compressive… VI.
CONCLUSIONS
This research work replicates the suitability of the use of Fly ash and Silica fume in unfired clay bricks with clay soil in different proportions to enhance its compressive strength and following results were found. For sun dried bricks Compressive strength value was highest at four percent of Silica fume and then started decreasing and became lower at ten percent however compressive strength value was higher than conventional clay bricks at all different percentages of Silica fume. The compressive strength was 121% higher than virgin bricks at 2% of silica fume and it increased to 181% higher at 4% 151% at 6%, 112% at 8% and 36% at 10% addition of Silica fume. For Fly ash compressive strength value was highest at 8% and then decreased at 10%. However, like Silica fume bricks at all different percentages compressive strength value was higher than conventional clay bricks. Compressive strength was 114% higher at 2% of Fly ash, 148% higher at 4%, 153% higher at 6%, 180% higher at 8% and 49% higher at 10% of Fly ash. Hence from this study it can be concluded that Silica fume and Fly ash can effectively be used to replace some portion of soils and get the higher compressive strength
ACKNOWLEDGEMENT I am thankful to almighty Allah for His graciousness, blessings and mercy to successfully complete this research work. Secondly I pay heartfelt thanks to Prof. Dr. Aneel kumar for his precious, remarkable and valuable guidelines and support in preparing and conducting this research paper.
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