Study of Pond ASH (BTPS) Use as A Fine Aggregate in Cement Concrete - Case Study

Transcription

1 Study of Pond ASH (BTPS) Use as A Fine Aggregate in Cement Concrete Case Study Prof. P. P. Bhangale Head & Associate Professor Civil Engineering Department, Shri Sant Gadge Baba College of Engineering & Technology, Bhusawal, Maharashtra, India. Prof. P. M. Nemade Assistant Professor Civil Engineering Department, Shri Sant Gadge Baba College of Engineering & Technology, Bhusawal, Maharashtra, India. Abstract Extensive study has born undertaken through the project to explore the possibility of utilizing this pond ash in the construction industry, especially in concrete and from view of sand becoming scare & contaminated with harmful chemicals & pond ash accumulation posing environmental problems, replacement of sand by pond ash in concrete attempted without compromising on strength. Pond ash sample was procured from Bhusawal Thermal Power Station (BTPS). Characterisation of pond ash sample was carried out and results indicated that pond ash sample can be tried as fine aggregate in concrete Keywords: BTPS (Bhusawal Thermal Power Station), Ponded Fly Ash, Cement Concrete I. INTRODUCTION Ash is the residue after combustion of coal in thermal power plants. Particle size of the ash varies form around one micron to around 600 microns. The very fine particles (fly ash) collected from this ash generated by electrostatic precipitators are being used in the manufacture of blended cements. Unused fly ash and bottom ash (residue collected at the bottom of furnace) are mixed in slurry form and deposited in ponds which are known as pond ash. Most of the Thermal Power plants in Indian adopt wet methods of disposal and storage of the ash in large ponds and dykes. In the wet method, both the fly ash collected from electrostatic precipitators and the bottom and grate ash are mixed with water and transported to the ponds in a slurry form. (2) Pond ash is being produced at an alarming rate and efforts are required to safely dispose it and if possible find ways of utilizing it. (3) Fly ash collected through hoppers has been widely accepted as pozzolonic and is being used by the construction industry. Pond ash being coarser and less pozzolonic is not being used, or more importantly in places where the fine aggregate is contaminated with harmful chemicals such as sulphates and chlorides and pond ash accumulation posing environmental problems.(4) The partial replacement of sand by pond ash in concrete is attempted. It is found that it is possible to use only pond ash as fine aggregate without compromising on strength and durability. This study opens up a major avenue for utilization of pond ash. II. RESEARCH SIGNIFICANCE Extensive literature survey was carried out and it was found that almost all the researches have concentrated on utilization of fly ash but utilization of pond ash is scarce. Presently Bhusawal Thermal Power Station (M.S.) has 1500 MW capacity of thermal power station and BTPS alone, nearly 1000 MT. of ponded ash is produced every day. Effective utilization of ponded ash is very essential to reduce the environmental problems caused by the accumulation of pond ash. If it is found suitable for construction industry, large scale utilization of pond ash would be possible and this will become a major contribution factor for reducing pollution. Future more a precious Natural resource as sand is becoming scare and quarrying of sand has Vol. 2 Issue 2 March ISSN: X

2 been restricted in many places near BTPS. This has lead to look for possibility of partial replacement of sand by pond ash without compromising on strength. III. EXPERIMENTAL PROGRAMMES Strength studies have been carried out on concrete with pond ash (BTPS) as partial replacement of sand probably for the first time in this area. Ordinary Portland cement conforming to IS: 1489: 1991 was used throughout the project work. The cement obtained was stored in airtight place to minimize weathering effect. Normal consistency value obtained was 30%. Similarly, initial and final setting time was 140 and 240 minutes, respectively. Specific gravity of cement was 3.16 and the value of soundness based on Le Chatelier s method was 1.2 mm. The results of other testes on cement are shown in table 1 and 2. Table 1. Chemical analysis of Cement Sample Chemicals % SiO2 Al3O3 Fe2O3 CaO MgO (LOI) SO3 % R2O3 IR Cement Table 2. Compressive strength of Cement Compressive strength, MPA Sample 3 days 7 days 28 days Cement Characterization on pond ash sample was carried on pond ash used in the investigations. Lime reactivity of pond ash sample was 3.04, specific gravity 2.06 and the bulk density was 825 kg/m3 the bulk density of coarse aggregate & fine aggregate is 1480 kg/m3 & 1740 kg/m3 respectively available Coarsed aggregate source from Sakegaon and fine aggregate Girana River near Jalgaon. Compacted state, respectively. The chemical composition of ponded ash shown in Table 3. The combine gradation of coarse aggregate, fine aggregate & ponded ash is given in Table4. The parameters chosen as variables were the same namely, different paste volumes, w/c ratio and different replacement levels. The compressive strength was determined at the ages of 7, 28 and 126 days for concretes of paste volume The ponded ash has been used as a part replacement of fine aggregate at different replacement labels water to cement ratio and pest volume in a given mix were the other parameters selected as a variables. The mix proportion ting is to produce the required properties in both plastic & hardened concrete by economical & practical combination of available material the design mixes prepared in accordance with the IS The mixes were designated as a mix with varying percentage ponded ash such as 0 %, 20%, 30 % and 40 % to evaluate the proportion. Cubes of dimension 150 mm were cast adopting weight batching and hand mixing technique. Steel moulds were used for casting and table vibrator was utilized for compaction. The cubes were demoulded after 24 hours and placed in water tanks for curing for 28 days after which they were air dried. Compressive strength studies air conducted on the mixes. The mix proportions for concrete Vp = 0.32 is given in Table 5 & compressive strength against pond ash added for Vp= 0.32 is given in Table 6. A minimum of three cubes were tested at a given test age and the average compressive strength obtained. The values were however, rounded to the nearest 1 MPa for recording. Table 3.chemical composition of ponded ash (S4) Sio Fe2 2 Compound LOI % SiO 2 Al2 O 3 + Al2O O 3 CaO MgO Na2O K2O 3 + Fe2O 3 Composition % Vol. 2 Issue 2 March ISSN: X

3 Table 4.Gradation of coarse aggregate, fine aggregate, ponded ash sample Cumulative Percentage Passing Sr. No. Sieve Size (mm) Coarse aggregate Fine aggregate Ponded ash FM Table 5. MIX PROPORTIONS FOR CONCRETE Vp = 0.32 W/c = 0.55 Water = 204 lit/m 3 Cement content = 371kg/m 3 Mix number RC1 RC2 RC3 RC4 20PAC1 20PAC2 20PAC3 20PAC4 30PAC1 30PAC2 30PAC3 30PAC4 40PAC1 40PAC2 40PAC3 40PAC4 Fine aggregate Batch quantity, kg/m 3 Ponded ash Coarse aggregate % coarse aggregate in total aggregate Note Vol. 2 Issue 2 March ISSN: X

4 c Reference concrete PAC Percentage of concrete Table 6.Compressive strength against pond ash added (Vp= 0.32) Compressive strength of concrete with 0%(M1), 20%(M2), 30%(M3) and 40%(M4) Pond Ash Vp = 0.32, Cement = 371 kg/m 3, water = 204 lit/m 3 Avg. Unit Fine Ponded Coarse Compressive strength N/mm 2 Mix Weight of Concrete Kg/m 3 Aggregate ash Aggregate 7 days 28 days 126 days M M M M IV. RESULT AND DISCUSSION Compressive Strength of Mixes with Vp = 0.32, w/c = 0.55, Cement = 371 kg/m 3 The results of the compressive strengths against percentage coarse aggregate in total aggregate show in figure 1 (ad) & compressive against ponded ash added for paste volume 0.32 is given in Figure 2. The mixes of this Vp showed the best strength mixes. Strength plots show that curves for ponded ash concrete tend to flatten out, indicating the relative insensitivity of the percent CA/FA in the mixes which could be due to the higher cement content of this concrete. At 40% replacement level, the curves tend to show a downward slope with the increase in coarse aggregate percentage indicating the influence of lack of enough fines or too much of coarse aggregate at higher replacement levels. Obviously, 40% of fine aggregate was too much in such an unplasticised mix Form Figure (2) the strength gain of ponded ash concrete due to the pore filling and pozzolanic effects are evident for paste volume of 0.32 up to a certain quantity of ponded ash addition in concrete. The rate of improvement of strength over reference concrete was higher for strength measured at 126 days than that 7 and 28 days. This set of mixes indicated that the maximum benefits were obtained at the 20% level of fine aggregate replacement while 30% replacement could also be acceptable but 40% was not. V. CONCLUSION 1) The density of concrete reduces with the increase in the percentage of pond ash the compressive strength of concrete with pond ash increases with increased curing period. 2) The maximum compressive strength occurs at the same percent of CA/FA which have shown the best workability in the mixes with paste volumes, w/c ratios and different levels of replacement of fine aggregate with ponded ash. 3) Mixes having higher fine aggregate percent shown strength comparable to maximum strength observed at later ages. However, mixes with lower fine aggregate percent shown lower strength at all ages. Such reduction in strength can be attributed to the formation of voids/pores due to lack of enough fines. 4) Considering the compressive strength criteria and cost of concrete, the replacement of fine aggregate with pond ash is feasible and the variation of strength of ponded ash concrete in comparison to reference concrete lies within ± 10% up to the age of 28 days for various mixes. Vol. 2 Issue 2 March ISSN: X

5 5) The compressive strengths of ponded ash concrete are equal to or higher than the reference concrete at any given age. The utilization of ponded ash enhances the strength considerably at later ages. The additional benefit in terms of strength can lead to economy. Utilization of ponded ash use in concrete is one of the effective ways of utilization of this industrial by product of BTPS and this will go to a long way in achieving sustainable development and to ensure that technology of ponded fly ash utilization as a replacement of sand in cement concrete should be viable both technically and economica REFERENCES [1] Mangaraj, B.E. and Krishanmoorthy S., Use of Ponded Fly Ash as Part Replacement of Fine Aggregate in Cement Mortar and Concrete and Influence on Workability Indian concrete Journal ( 1993). [2] Monzo, J., Pay, J., and Eduardo PerisMora, A Preliminary study of flyash granulometric influence on Mortar Strength, Cement and concrete research, Vol. 24. No. 4, (1994). [3] Manzo, J.Paya, PerisMoro, E. and Borrachero, M.V., Mechanical Treatment of fly ashes: Strength Development and Workbility of Mortars Containing Ground fly ashes, Vth Intl. Conf. Milwaukee, Wisconsin, U.S.A. Fifth (ANMAT) ACI (1995). [4] A.K. Mullick use of Industrial wastes for sustainable cement and concrete constructions. The Indian concrete journal vol 81 No (2007) [5] Kalgal M.R. Pranesh, RN and Ravi Shankars Strength and durability of concretewith pond ash as fine aggregate. The Indian concrete journal volume 81 No.3 711(2007). [6] A.G. Krishnamurthy, J.S. Chauhan, K.K. Punjabi waste Utilization & management National Workshop scientific solutions for waste management pollution control 5053 (2004) (4th October 2004). [7] A.K. Mullick use of Industrial wastes for sustainable cement and concrete constructions. The Indian concrete journal vol 81 No (2007). [8] An Information FLY Ash Utilisation & Disposal = An Information Guide Fly Ash Utiliation & Disposal, Central Building Research Institute Roorkee. (2005). (a) (b) Vol. 2 Issue 2 March ISSN: X

6 (c) (d) Figure 1. (a d) Showing compressive strength against ponded ash added for paste volume 0.32 Figure 2. Showing compressive strength against ponded ash added for paste volume 0.32 Vol. 2 Issue 2 March ISSN: X