Experimental Studies on Lime-Soil-Fly Ash Bricks

Transcription

1 Experimental Studies on Lime-Soil-Fly Ash Bricks Tabin Rushad S 1, Abhishek Kumar 2, Duggal S. K 3, Mehta P. K 4 1- Ph D Scholar, Department of Civil Engineering, Motilal Nehru National Institute of Technology, Allahabad 2- P. G. Student, Department of Civil Engineering, Motilal Nehru National Institute of Technology, Allahabad 3- Prof. & Head, Department of Civil Engineering, Motilal Nehru National Institute of Technology, Allahabad 4- Associate Prof., Department of Civil Engineering, Motilal Nehru National Institute of Technology, Allahabad rajaabhis@gmail.com ABSTRACT Fly ash is generated in large quantities especially by thermal power plants. A lot of research has been carried out for effective utilization of fly ash in building industry. Use of fly ash in manufacturing brick is one such subject which is being studied by researchers. The aim of the present study is to investigate the strength and water absorption characteristic of fly ash bricks made of lime (L), local soil (S) and fly ash (FA). The experiments were conducted both on Hand moulded and Pressure moulded fly ash bricks. It was observed that none of the L-S-FA bricks satisfy all the requirements of standard codes. While some of the bricks satisfy the provisions in respect of strength only the L-FA (40: 60) bricks satisfy the requirement of Indian Standard Code in respect of strength as well as water absorption characteristics. Keywords: Lime, Soil, Fly ash, Compressive Strength and Water absorption. 1. Introduction Fly ash is finely divided residue resulting from the combustion of powdered coal, transported by the flue gases and collected by electrostatic precipitators. Its proper disposal has been a cause of concern since long, which otherwise leads to pollution of air, soil and water. The disposal and utilization of this fly ash is a matter to ponder. The World Bank has cautioned India that by 2015, land disposal of coal ash would require about 1000 Km 2 of land. To overcome this problem and to encourage the utilization of fly ash, Government of India in 2003 made it mandatory to use at least 25% fly ash with soils on weight to weight basis for manufacture of bricks within a radius of 100 Km from coal or lignite based thermal power plants. Several researchers and organizations have put forward the methods for use of fly ash in brick making. For last several decades attempts are being made to find a suitable method for the disposal and proper utilization of fly ash. Saibulatov (1) confirmed the saving in fuel costs and reported a less variability in strength with ash bricks. Zhang and Xing (2) undertook an experimental program to study 994

2 the individual and admixed effects of lime and fly ash on the geotechnical characteristics of expansive soil. Its plastic limit increased by mixing lime and the liquid limit, and hence the plasticity, decreased by mixing fly ash. Based on the results they concluded that the expansive soil can be successfully stabilized by lime and fly ash. V Karthikeyan and M Ponni (3) studied the utilisation of fly ash in bricks. The fly ash can be effectively used for manufacture of bricks using fly-ash, lime, sand and gypsum. The useful proportion found was 25: 4: 3.33: 1. Tuncer B. Edil et al (4) evaluated the effectiveness of self-cementing fly ashes derived from combustion of sub-bituminous coal at electric power plants for stabilization of soft fine-grained soils in terms of California bearing ratio and resilient modulus (Mr) tests. Tests were conducted on soils and soil fly ash mixtures prepared at 7% wet optimum water content (a standardized condition, representative of the typical in situ condition in Wisconsin), and at 9 18% wet of optimum water content (representative of a very wet in situ condition). Addition of fly ash resulted in appreciable increases in the CBR and Mr values of the inorganic soils. Dr. Robert M. Brooks (5) blended the expansive soil with 12%rice husk ash (RHA) content and 25 % fly ash contents for strengthening the expansive sub-grade soil, but suggested a 15 % fly ash blending with the same RHA to form a somewhat smaller reduced layer. J. N. Akhtar et al (6) used C category fly ash as a raw material in FAB and also treated the fly ash with 10% cement or 5% coarse sand or 15% sand or different combination of sand and lime stone dust with or without 0.2% geo fibre. He observed that treated fly ash is superior in strength and the best result is found when the brick is made of 50% of fly ash and 25% admixture of sand and max tenth part by weight of lime stone dust. They found that the brick so made achieved the compressive strength that is close to the value of standard first class brick in India. Kolay, P.K. et al (7) on the other hand investigated the stabilization of class F pond ash on tropical peat soil. With increase of pond ash content (5, 10, 15 and 20 %) the maximum dry density (MDD) of peat soil increased while optimum moisture content (OMC) decreased. In this paper (8) the suitability of fly ash as raw material treated with lime is studied to make bricks of local soil. Such bricks termed as FALSB and their components were tested as per the relevant Indian Standards and results are presented below. 2. Materials Lime (L) The lime was tested as per the provisions of IS: The impurities present in lime were less than 5%. The OMC and MDD were found to be 42.5% and 1080 kg/m 3, respectively. Soil (S) The soil available in MNNIT Allahabad Campus was taken and tested as per the provisions contained in IS: The specific gravity of the soil was In all the samples, the fraction finer than 2µ was maintained as 11%. Its liquid limit (LL), 995

3 plastic limit (PL), and plasticity index (PI) were 30%, 21%, and 9% respectively. The OMC and MDD were 14.5% and 1780 kg/m³. Its unconfined compressive strength was N/mm². Fly ash (FA) The fly ash for the present investigation was procured from IFFCO, Phulpur, Allahabad. The specific gravity of fly ash was In all the samples, fraction finer than 2µ was maintained as 7.7%. Its LL, PL, and PI were 15%, 15%, and 0% respectively. The OMC and MDD were 45% and 800 kg/m 3 respectively. The chemical composition of fly ash is presented in Table 1. Table 1: Chemical Composition of Fly Ash Chemical % By Weight Composition Unburnt Carbon SiO Al 2 O Fe 2 O TiO CaO 2.24 K 2 O 0.60 MgO 1.28 Mo 2 O Methodology The modular bricks samples of size 190 mm 90 mm 90 (IS: ) were cast in lab using the lime, soil and FA in ratios of: 15: 5: 80 and 10: 10: 80; 25: 5: 70 and 20: 10: 70; 35: 5: 60 and 30: 10: 60 respectively. Similarly modular bricks made of L and FA in the ratio of 20: 80, 30: 70 and 40: 60 respectively were cast. The sample was mixed with sufficient quantity of water to obtain working consistency for moulding. The clean mould was filled with the lime fly ash and soil mixture without allowing any air bubble. The surplus mix was removed and top surface was leveled. For the hand moulded bricks no pressure was applied on the mould. The pressure moulded bricks were prepared by applying load of 10, 30 and 50 kn, respectively. The moulded brick were allowed to dry for two days, protecting from direct sun light. The specimens were immersed in water at room temperature for 24 hours and there after, the specimens were taken out of water. These samples were cured by moist jute bags for 7 and 28 days. The samples were tested after 7 and 28 days respectively for compressive strength as per the provisions of IS: 3495 (Part 1) The water absorption of the bricks was tested as per the provisions contained in IS: 3495 (Part 2) Before testing, the frogs and voids of the specimen were filled up with cement sand mortar (1: 1). 996

4 4. Experimental Results The results of the present investigation are presented in Figures 1 to 3 and compared with the Indian Standards of clay and fly ash bricks (IS: and IS: ). Figure 1: 7 Days Compressive Strength of Bricks made of L-S-FA (Soil-0%) Figure 2: 28 Days Compressive Strength of Bricks made of L-S-FA (Soil-0%) Figure 3: 7 Days Compressive Strength of Bricks made of L-S-FA (Soil-5%) 997

5 Figure 4: 28 Days Compressive Strength of Bricks made of L-S-FA (Soil-5%) Figure 5: 7 Days Compressive Strength of Bricks made of L-S-FA (Soil-10%) Figure 6: 28 Days Compressive Strength of Bricks made of L-S-FA (Soil-10%) 998

6 Figure 7: 28 Days Water Absorption of Bricks made of L-S-FA (Soil-0%) Figure 8: 28 Days Water Absorption of Bricks made of L-S-FA (Soil-5%) Figure 9: 28 Days Water Absorption of Bricks made of L-S-FA (Soil-10%) 999

7 5. Discussion Figures 1 to 6 show that compressive strength of all type bricks having different ratio of its constituent increase with pressure. With increase in soil percentage, strength of bricks go down. A comparison of figures 3 and 4 show that of brick of L: S: FA (35: 5: 60) follows the class 3.5 designation in respect of strength. In all cases studied, hand moulded bricks are not suitable for any use; same is the case with the machine moulded bricks at load of 10 kn. Increase in proportion of lime at constant amount of soil increases the compressive strength of the bricks. Figure 3 shows that the 7 days strength of bricks made of L: S: FA (35: 5: 60) at 50 kn of load, gained strength of class 3.5 brick. The 28 days compressive strength of bricks made of L: S: FA (35: 5: 60) at load of 50 kn belong to class 5. While bricks made of L: S: FA (35: 5: 60) at a load of 30 kn belong to class 3.5. Figure 6 shows that the bricks made of L: S: FA (30: 10: 60) at load of 30 and 50 kn and L: S: FA (20:10: 70) at load of 50 kn satisfy the class 3.5 designation. However none of the brick specimen (Fig. 7, 8 and 9) qualifies the water absorption percentage limits as specified in IS: Change in soil percentage from 0 to 10 % does not affect the water absorption capacity significantly. On application of load the gain in strength is more in case of bricks with large lime proportion. Lime proportion does not influence the compressive strength of hand moulded bricks. Bricks having L: FA compositions of 30: 70 and 40: 60 satisfy the requirements of class 3.5 and class 5, respectively, when compressive strength at 28 days is considered as shown in figure 1 and 2. Bricks with L: FA composition 40: 60 and moulded at 50 kn of load belongs to class 3.5 when compressive strength at 7 days is considered. Increase in lime content decreases water absorption capacity of bricks as shown in figure 7, 8 and 9. Brick with L: FA compositions 40: 60 is the only one satisfying the criteria of water absorption requirements of IS: Conclusion 1. The compressive strength of bricks increases with lime proportion. 2. The bricks made under pressure has increased compressive strength according as the pressure was applied 3. As long as the percentage between lime and fly ash is unchanged, the change in soil percentages does not affect compressive strength significantly. 4. Most of the L-S-FA bricks belong to class 3.5 and 5 in respect of strength only. In respect of water absorption all L-S-FA bricks fail. 5. Only L-FA (40: 60) brick satisfies the criterion of class 3.5 in respect of both strength and water absorption. 1000

8 7. References 1. Saibulatov S. (1984), Working Properties of Ash Ceramic Materials for Building Purpose, Glass Ceramics, 41(9), pp ZHANG Ji-ru and CAO Xing (2002), Stabilization of Expansive Soil by Lime and Fly Ash, Journal of Wuhan University of Technology - Materials Science Edition, 17(4), pp V Karthikeyan and M Ponni (2006), An Experimental Study of Utilization of Fly Ash for Manufacturing of Bricks, 22 nd National Conference of Architectural Engineers Trichur. 4. Tuncer B. Edil, M.ASCE; Hector A. Acosta, M.ASCE; and Craig H. Benson, M.ASCE (2006), Stabilizing Soft Fine-Grained Soils with Fly Ash, Journal of Materials in Civil Engineering ASCE, pp Dr. Robert M. Brooks (2009), Soil Stabilization with Fly Ash and Rice Husk Ash, International Journal of Research and Reviews in Applied Sciences, 1(3), pp J. N. Akhtar, J. Alam and M. N. Akhtar (2010), An Experimental Study on Fibre Reinforced Fly Ash Based Lime Bricks, International Journal of the Physical Sciences, 5(11), pp Kolay, P.K., Sii, H. Y. and Taib, S.N.L. (2011), Tropical Peat Soil Stabilization using Class F Pond Ash from Coal Fired Power Plant, International Journal of Civil and Environmental Engineering, 3(2), pp Om Prakash (1990), Utilization of Pulverized (Fertilizer Plant) Fly Ash as Low-Cost Bricks and Construction Material M. Tech. Thesis Submitted to MNREC, Allahabad. 9. IS: , Methods of tests for building lime Specification, Bureau of Indian Standards, New Delhi. 10. IS: , Methods of tests for Soils Specification, Bureau of Indian Standards, New Delhi. 11. IS: 3495 (Part 1 and 2)-1992, Methods of tests of Burnt Clay Building Bricks Specification, Bureau of Indian Standards, New Delhi. 12. IS: , Common Burnt Clay Building Bricks Specification, Bureau of Indian Standards, New Delhi. 1001

9 13. IS: , Pulverized Fuel Ash-Lime Bricks Specification, Bureau of Indian Standards, New Delhi. 1002