YEAR 2006

SOIL STABILIZATION WITH KOTA STONE SLURRY AND FLY ASH
By Pawan Kalla1, Arun Gaur, Manish Rotwal2 & Gaurav Aggarwal3

1. INTRODUCTION
1.1. General

In India there are many industrial by products, which are being dumped as waste material, creating disposal problem and pollution hazard. The major volume of various wastes in different industries, like red mud, blast furnace slag and other locally available low cost material, can successfully be used in road construction.

Kota stone is basically limestone. It is a very tough, non water absorbent and non porous stone. Moreover, their resistance to wear and delamination is higher than other stones. The production of Kota stone as per Director Mines and Geology Rajasthan is approximately 28,68,557 tonne per annum (2005). Kota stone slurry is also a waste material coming out from the Kota stone industries. Kota stone slurry is available in huge amount in areas near by Jhalawar and Kota in Rajasthan. Powder slurry is produced in cutting and polishing of Kota stone. Generally, it is available as a white, soft powder in moist condition. It creates soil pollution, water pollution and air pollution leading to adverse affect on crop production and human health. It is generally dumped on the road sides or in low lying areas, which gets washed and mixed with rainy water during rainy season. The present study tries to explore its potential as stabilizer in road construction.

Fly ash is produced from coal based thermal power stations as a waste by product. There are about 82 thermal power plants in the country which currently produce about 85 million tonne of fly ash per annum. India utilizes around 10 per cent of the total fly ash produced (1998) as against 3-5 per cent (1994). Fly ash consists of inorganic matter in the form of coal and unburnt carbon. It is generally grey to black in colour, abrasive and acidic in nature, particle size 1-300 µm. Pollution related problems in power plants are essentially caused by two aspects of the plant operation. The first involves water used for cooling and second involves burning of fossil fuel (coal), when coal is burnt in power stations, SOx, NOx, SPM (suspended particulate matter) i.e. fly ash are produced as major pollutants however as our energy consumption grows, the scale of air pollution will increase. The control of fly ash emission thus becomes most essential. This waste material can be utilized in the stabilization in road construction activities.

Ministry of Road Transport and Highways (MORT&H) has directed all its agencies to use fly ash for all road and embankment construction work within a radius of 100 km from the thermal power plant, as per Indian Road Congress Specifications IRC:SP:58-2001. Also National Highway Authority of India (NHAI), a premier road & highway agency in the country is utilizing fly ash on a massive scale. 60 lakh cum of fly ash is being used in its on going projects in Delhi, U.P. & West Bengal. And its new NH-2 project would use more than 67 lakh cum of fly ash.

1.2. Hazards due to Kota stone slurry and fly ash

Kota stone slurry causes health hazards. Silicosis is a pneumoconiosis caused by inhalation of silica which is lethal to macrophages that ingest it and releases their enzymes. It is a serious and progressive disease and it is caused by Kota stone slurry. Extrinsic allergic alveolitis can be caused by sensitization to farmer’s lungs by Kota stone dusts. It tends to affect the respiratory units to the lung rather than conducting airways and may have ‘flu’ like symptoms in addition. In some respects it is similar to humidifier fever which might be caused by sensitization. It causes irritation to skin, throat and respiratory tract (coughing and sneezing).

Fly ash is a source of air pollution since it remains air-borne for a long period and causes health hazards. Fugitive dust and heavy metal contamination in the ground water are the major problems for the local masses. Swallowing of fly ash may cause abdominal discomfort. It causes irritation to eyes (watering and redness), skin (irritant/contact dermatitis from mechanical abrasion or alkaline composition), and nose, throat, and respiratory tract (coughing and sneezing). Repeated inhalation of fly ash dust containing crystalline silica can cause bronchitis, silicosis (scarring of the lung), and lung cancer. It may also increase the risk of scleroderma (a disease affecting the connective tissue of the skin, joints, blood vessels, and internal organs). Inhalation of high levels of fly ash dust may result in severe inflammation of the small airways of the lung and asthma-like symptoms.

Two wastes, namely, Kota stone slurry from Kota stone industries and fly ash from thermal power plant have been used in combination to evaluate their stabilizing effect on black cotton soil. The endeavour is to assess the optimum amount of waste material that can be mixed with soil for best stabilization effects and also the amount which cause no or limited detrimental effects in the soil.

The present study was undertaken with the following objectives:

(i) To explore the possibility of using Kota stone slurry in rural road construction program in Kota region.
(ii) To study the effect of Kota stone slurry and fly ash on Modified Proctor’s density and OMC of black cotton soil.
(iii) To study the effect of adding Kota stone slurry and fly ash on consistency limits of black cotton soil.
(iv) To study the changes in CBR of a soil by the addition of Kota stone slurry and fly ash.

3. BACKGROUND LITERATURE

Swami 2002 during a study on use of marble dust concluded that addition of 15 per cent dust in sandy soils and 25 per cent in black cotton soils considerably improve the dry density and CBR of the soils .Chandra, et al.,(2005) while studying use of Rice Husk Ash (RHA) and lime sludge in stabilization of clayey soils found that addition of 20 per cent RHA and 16 per cent of lime sludge increases the CBR from 5 per cent to 16.7 per cent. RHA and lime sludge can effectively be employed in stabilization of clayey soils for subgrade and subbase economizing the cost of construction. Srivastava, et al. (1995) used fly ash and lime sludge in combination for stabilizing alluvial soil. The effect of adding fly ash to soil-lime sludge mix was to reduce the liquid limit, plasticity index and to increase the shrinkage limit. They also studied the compression and consolidation behaviour of a clayey soil stabilized with industrial wastes. Rao et al. (1999) reported that for high fly ash concrete with 60 per cent fly ash and 30 percent rice husk ash, the compressive strengths after both 7 days and 28 days were observed to have improved by about 43 percent, which is a significant contribution of fly ash as an admixture.

4. EXPERIMENTAL PROGRAMME

4.1. Materials and their properties

The soil used in the study was black cotton soil. The properties of soil as determined in the laboratory are given in Table 1. The soil is classified as inorganic clay with low compressibility (CL) as per Unified soil classification. According to AASHTO soil classification system, the soil lies in A-6 group.

Kota stone slurry is produced in cutting and polishing of Kota stone. It is soft and white in colour. Dried slurry is in lumped form in dump yards. The various properties of Kota stone slurry are given in Table 2.

The fly ash is obtained from coal based thermal power plants as a waste by product. It is fine grained, light weight, grey-black in colour containing some percentages of unburnt carbon. The various properties of fly ash are given in Table 3.

4.2. Test Programme

Before performing the various tests on materials, the proportioning of ingredients is to be ascertained. The amount of Kota stone slurry and fly ash was varied from 3 to 21 per cent by weight of soil in steps of 3 per cent. For, combination of both materials with soil, 18 per cent of Kota stone slurry was mixed with 3 to 21per cent of fly ash and 18 per cent of fly ash was mixed with 3 to 21per cent of Kota stone slurry. In total 27 mixes were prepared as given in table 4. Modified proctor’s density tests, Atterberg’s limit, CBR tests were conducted on various mixes.

The CBR is a measure of resistance of a material to penetration of standard plunger under controlled density and moisture conditions. The CBR test conducted in remolded or undisturbed specimen in the laboratory. Briefly the test consists of causing of cylinder plunger of 50 mm diameter to penetrate a pavement component material at 1.25 mm/min. The loads, for 2.5 mm and 5 mm are recorded. This load is expressed as a percentage of standard load value at a respective deformation level to obtain CBR value.

5. ANALYSIS OF RESULTS AND DISCUSSION

5.1. Modified Proctor’s test results

The results of standard compaction tests on black cotton soil treated with different proportions of Kota stone slurry and fly ash are summarized in Table 5. It is observed that relative proportions of Kota stone slurry and fly ash have considerable effect on the optimum moisture content and maximum dry density of the compacted soil. Variation in maximum dry density of soil with different proportions of Kota stone slurry-fly ash is shown in Fig. 1 and 2. The maximum dry density of soil increases to 1.917 gm/cm3 (from 1.855 gm/cm3 for neat soil) when 18 per cent of Kota stone slurry is added. It decreases to 1.681 gm/cm3 when 21 per cent of fly ash is added. The optimum moisture content increases with the increase in the proportions of Kota stone slurry and fly ash in the soil as shown in Fig. 3 and 4.

5.2. Atterberg’s limit
The results of liquid limit, plastic limit and plasticity index of different soil-Kota stone slurry-fly ash mixes are presented in Table 5. It was observed that liquid limit decreases with addition of Kota stone slurry and fly ash and plastic limit increases with addition of Kota stone slurry and fly ash. Fig. 5 and 6 shows effect of Kota stone slurry and fly ash on PI value of the soil. The effect of Kota stone slurry alone on plasticity index is more effective than fly ash. The addition of Kota stone slurry (3 to 21 percent) further reduces the PI value of the mix. The PI curve shows a minimum value of 5.54 when the soil was stabilized with 12 per cent fly ash along with 18 per cent Kota stone slurry. The optimum proportions of soil: Kota stone slurry: fly ash were 70:18:12.

5.3. Effect of Kota stone slurry and Fly ash on soaked CBR

The results of the soaked CBR tests on soil stabilized with different proportions of Kota stone slurry and fly ash are given in table 5. From the results, it is observed that there is considerable improvement in the soaked CBR values of different mixes. The soaked CBR of the soil used in the present investigation is 2.098 per cent. It increases to 8.79 percent for a mix soil: Kota stone slurry: fly ash as 79:18:3. The effect of Kota stone slurry alone on CBR is also considerable as may be seen from Fig.7 and 8. The soaked CBR of the soil stabilized with 18 per cent Kota stone slurry is obtained as 7.75 per cent, a 3.7 times increase when compared with that of neat soil. It further increases to 8.79 percent when 3 per cent fly ash is added and then decreases when fly ash is added further. There is a remarkable improvement when black cotton soil was stabilized with 18 per cent Kota stone slurry and 3 per cent fly ash.

If we look on four important characteristics of the Kota soil mix with Kota stone slurry, with fly ash and combination of both i.e. CBR values, OMC, maximum dry density (MDD) and plasticity index (PI) shows that with increase in Kota stone slurry and fly ash contents plasticity index value decreases, and when optimum Kota stone slurry and optimum fly ash was mixed with different proportions of fly ash and Kota stone slurry respectively then PI value varies. OMC values increases with increases in the Kota stone slurry and fly ash. MDD was almost constant in all the proportions. CBR values increases upto 18 per cent in case of Kota stone slurry and fly ash alone. When both the materials mix with each other with the optimum value respectively, then CBR value slightly increases and then decreases.

6. CONCLUSIONS

Following conclusions are drawn from the work described in the present paper.
1. The substantial amount of waste materials, like, Kota stone slurry and fly ash are being produced by various Kota stone industries and thermal power plants in the country. These materials are causing hazardous effects to the lands and surroundings and a great problem for their disposal. Use of these waste materials in road construction can reduce the problem of their disposal to a great extent.

2. The effect of Kota stone slurry and fly ash on consistency limits is to increase the liquid limit and plastic limit and decrease the PI value of the soil. The PI value of the soil decreases from 24.00 to 5.54 when 18 per cent Kota stone slurry and 12 per cent of fly ash are added.

3. The dry density of mix decreases with increase in proportions of Kota stone slurry and fly ash. Whereas, the optimum moisture content increases with increase in proportions of these materials.

4. The soaked CBR increases upto 18 per cent in mix of Kota stone slurry and fly ash (separately) with soil and decreases after that. While the CBR increases initially and then decreases with the combination of slurry and fly ash. The soaked CBR increases from 2.098 to 8.79 when 18 per cent Kota stone slurry and 3 per cent fly ash is mixed with the soil.

5. Kota stone slurry and fly ash can successfully and effectively used in stabilization of black cotton soil. The stabilized soil may be used as sub grade economizing the cost of construction also.




REFERENCES

1. Chandra Satish, Kumar Shiv and Anand Rajesh Kumar (2005), “Soil Stabilization with Rice Husk and Lime Sludge”, Indian Highways, Vol. 33, No.5, pp. 87-98.

2. Swami B.L (2002), “Feasibility Study for Utilization of Marble Dust in Highway Sector, IRC, HR Bulletin No. 67, New Delhi, pp. 27-36.

3. Bhasin, N.K., Goswami N.K., Oli P., Krishan N. and Lal N.B. (1988), “A Laboratory Study on Waste Materials for the Construction of Roads in Black Cotton Soil Area”, Highway Research Bulletin, No. 36, IRC, New Delhi, pp. 1-11.

4. IRC: 37-2001, “Guidelines for the Design of Flexible Pavements”, Indian Roads Congress, New Delhi.

5. IS: 2720-1979 (Part XVI), “Method of Test for Soils”, Bureau of Indian Standards, New Delhi.

6. IRC SP-58-2001 “Guidelines for the Use of Fly Ash in Road Construction” Indian Roads Congress, New Delhi.

7. Srivastava, R.K., Joshi D.K. and Kumar R. (1995), “Utilization of Industrial Waste (Fly Ash and Lime Sludge) in Combination for Stabilizing Alluvial Soils, Indian Geotechnical Conference (IGC-95), Vol. I, Bangalore, pp 223-226.

8. Rao, M.V.S., Rao K.R.M., Janaradhana M. and Kumar B.R. (1999), “High Fly Ash Concretes with Rice Husk Ash as an Admixtures”, Institute of Engineers (India), Vol. 80, New Delhi, pp. 57-63.

9. Annual Kota Stone Production Data 2004-05, Director, Mines and Geology, Rajasthan.

10. www.google.com Utilization of Fly ash in Road Construction.

11. www.google.com Hazards due to Fly Ash.

12. www.google.com Limestone Hazards.

13. http://kota.nic.in/ind.htm.

14. http://www.tifac.org.in/do/fly/proj/road1.htm.

15. http://www.tifac.org.in/news/flyindia.htm.