Figure 1a. Brick specimens B S20 A80
An experimental investigation has been carried out to study the feasibility of manufacturing bricks from locally available black cotton soil using industrial waste materials such as fly ash and crusher waste. In order to study the characteristics of brick, a total of 504 numbers of brick specimens of 230 x 110 x 70 mm size were cast in three series by combining black cotton soil, fly ash and crusher waste in different proportions. The brick specimens were then air dried, baked in kiln and tested for compressive strength, water absorption, efflorescence and density as per IS:3495 code. Also, for comparison purpose, 18 numbers of conventional burnt clay bricks and 18 numbers of pressed type water cured cement fly ash bricks were tested for the aforesaid brick properties. Test results obtained in the present investigation indicate that it is possible to manufacture good quality bricks from locally available black cotton soil by suitably adding either fly ash or crusher waste or both, and such bricks can be used in lieu of conventional burnt clay bricks or pressed type water cured cement fly ash bricks presently in use for various construction activities.
The common burnt clay brick is one of the oldest building materials and is being extensively used even today as a leading construction material because of its strength, durability and low cost. Demand for this brick in our country is increasing day-by-day because of the above mentioned favorable characteristics and brisk construction activities. Black cotton soil (also called black soil) is one of the major soil deposits in India covering an area of about 5.4 lakh square kilometer i.e. 16.6% of the total land area of the country ( [7], [25]).Ramanathapuram district in Tamilnadu has a total land area of 4123 square kilometer and the black soil deposits in the district constitute about 46% of the land area ( [6], [24]). Owing to the large amount of black soil deposits in Ramanathapuram district, there are no largescale brick manufacturing kilns available at present to cater to the needs of various construction activities in and around Ramanathapuram and Rameswaram regions, and people living in these regions rely on kilns available in the nearby areas which are about 40 to 100 km away from Ramanathapuram/Rameswaram city. This increases the cost of bricks and hence, the overall cost of projects in these regions by about 15 to 20%.
Generally, the quality of brick depends mainly on the type and quality of raw materials used for manufacturing them. It is a well-established fact that good quality brick can be manufactured from alluvial soil or red soil whereas it is not feasible to manufacture brick from raw black soil. This is mainly due to the following two reasons: (i) the black soil is highly expansive and sticky in nature when it comes in contact with water and hence, it is very difficult to mix and pug the soil, and (ii) the black soil shrinks heavily and develops large number of wide cracks when allowed to dry and hence, bricks made from this soil lose their dimensional stability and overall integrity. Therefore, in order to overcome the above two major problems, mineral admixtures can be added suitably to stabilize/treat the black soil so as to manufacture bricks.
The various mineral admixtures available to stabilize and improve the engineering properties of black soil are: cement, lime, sand, micro silica fume, blast furnace slag, fly ash (also called pulverized coal ash), rice husk ash, groundnut shell ash, bagasse ash, crusher waste (also called crusher dust or quarry dust), marble waste, granite waste, cement kiln waste, carbide waste, tile waste, ceramic waste, ground polyvinyl waste, steel mill scale waste, etc. Stabilization of black soil is often achieved either by using only one admixture ( [1], [2], [5] , [8], [13], [15], [16], [17], [18], [19], [20], [26]) or by using more than one admixture ( [3], [4], [11], [12], [14], [21], [22]). Now- a-days, cement stabilization is not preferable because of the increasing cost of cement and environmental concerns related to its production. Lime stabilization is also not suitable for soils which contain sulphates. Presence of sulfates can increase the swelling behavior of soil due to the formation of swelling minerals such as ettringite and thaumasite ( [23]). Also, mineral admixtures like sand, micro silica fume and blast furnace slag are scarce and/or costlier;other mineral admixtures like fly ash (a waste material from thermal power plants) and crusher waste (a waste material from quarry stone crusher units/industries) are cheaper and easily available in abundance when compared to the remaining ash-type or waste-type admixtures cited above.
Further, fly ash and crusher waste are industrial waste materials, and they are simply dumped near the plants on large hectares of fertile land. These wastes cause environmental problem, contaminate ground water quality and also cause serious health hazard to the people living in the nearby areas. Disposal of these wastes is a rapidly growing problem and effective utilization of these wastes converts them into useful products, saving natural resources and can also alleviate the disposal and environmental problems significantly. Therefore, in the present work, an attempt has been made to experimentally study the feasibility of making bricks from locally available black soil using low cost industrial waste materials such as fly ash and crusher waste. Test results obtained in this investigation are presented and discussed in this paper.
Following are the materials used in this experimental investigation:
Black soil available in the college (i.e. University College of Engineering, Ramanathapuram) premises having a specific gravity of 2.40, liquid limit of 68.12%, plastic limit of 38.67%, shrinkage limit of 14.25% and maximum unconfined compressive strength of 85.5 kN/m2 .
Gray color fly ash obtained from Tuticorin thermal power plant having a specific gravity of 1.93, bulk density of 18.63kN/m3 and fineness (on 75 micron sieve) of 92.54%.
Crusher waste having a specific gravity of 2.65, fineness modulus of 3.13, water absorption of 0.84%,maximum dry density of 20.62 kN/m3 , uniformity co-efficient of 15.98 and curvature co-efficient of 2.87.
Water available in the college premises having a pH value of 8.
In the present experimental investigation, a total of 504 numbers of brick specimens were cast in three series by combining locally available black soil in the Ramanathapuram region with low cost industrial waste materials such as fly ash and crusher waste in different proportions. In series 1, black soil and fly ash were combined, where as in series 2, black soil and crusher waste were combined. But, in series 3, black soil, fly ash and crusher waste were combined. The details of number of brick specimens cast in all the three series to evaluate the various brick properties by conducting relevant tests are presented in Table 1. For casting the brick specimens, the concerned materials were taken on weight basis in dry condition. The dry materials were then mixed thoroughly by adding required quantity of water till the mixture attains uniform color. Wooden molds of 230 x 110 x 70 mm size were used for casting the brick specimens. Figure 1a to1c shows typical brick specimens cast in the present work. The cast brick specimens were then allowed to dry for a period of 2 weeks, so that the moisture present in the green specimens evaporate. Then the brick specimens were baked in a kiln for about 24 hours at 600 to 800oC and then allowed to cool in a gradual manner for a period of 2 weeks. The burnt brick specimens were then taken out from the kiln and then tested for compressive strength, water absorption, efflorescence and weight density in the laboratory as per IS: 3495 code procedure ([10]). For comparison purpose, 18 numbers of ordinary burnt clay bricks (also called clay bricks) and 18 numbers of pressed type water cured cement fly ash bricks (also called fly ash bricks) commonly used for the construction activities were also tested for the aforesaid brick properties (vide Table 1).
Figure 1a. Brick specimens B S20 A80
Figure 1b. Brick specimens B S20 W80
Figure 1c. Brick specimens B S20 A 40W40
Table 1. Details of brick specimens cast
Test results obtained for fly ash stabilized (i.e. treated/modified) black soil bricks, crusher waste stabilized black soil bricks, and both fly ash and crusher waste stabilized black soil bricks in all the three series are presented in Table 2. Also, for the purpose of comparison, the test results obtained for the clay bricks and fly ash bricks are presented in Table 2. The results reported in Table 2 are average value of 6 specimens. The individual effect of addition of fly ash/crusherwaste,and the combined effect of addition of both fly ash and crusher waste into the black soil on various brick properties are discussed in the succeeding sections.
Table 2. Summary of test results
During the experimental investigation conducted in the series 1, it was observed that the brick specimens made by combining the soil and ash in the 100% : 0%, 90% : 10%, 80% : 20% . and 70% : 30% proportions have developed many cracks at the end of the air drying period. This shows that the shrinkage nature of the black soil cannot be completely eliminated by adding fly ash from 0 to 30%.Also, it was observed that the brick specimens made by combining soil and ash in the 0% : 100% proportion were in the form of powder at the end of air drying process. This is attributed to absolute absence of sticky nature of black soil and its total absence failed to bind all the particles present in the specimens. Further, it was observed that brick specimens made by combining soil and ash in the 20% : 80% and 10% : 90% proportions have resulted in partial damage or complete collapse when such specimens were kept in water for water absorption and efflorescence tests. This may possibly be due to non-uniform or inadequate baking of specimens in the kiln or due to the presence of little amount of sticky black soil in the specimens thus causing loss of dimensional stability and overall integrity leading to partial damage or complete collapse of the specimens. Besides, no formation of white patches (i.e. deposits) was noticed on the surfaces of all the specimens tested for efflorescence. This indicates the absence of water soluble salts in the locally available black soil. Therefore, it is evident from this investigation that it is not feasible to make bricks from locally available black soil by adding fly ash either up to 30% or beyond 70%.However, it is possible to make bricks from locally available black soil by adding fly ash from 40 to 70%, and bricks produced using this range have resulted in compressive strength values ranging from 5.05 N/mm2 to 5.65 N/mm2 , water absorption values ranging from 16% to 19% and density values ranging from 11.82 kN/m3 to 12.35kN/m3 . Also, it is observed that the brick specimens made by combining 50% of soil and 50% of ash (i.e. 1:1 ratio) have shown a higher compressive strength of 5.65 N/mm2 , lower water absorption of 16%and higher density of 12.35 kN/m3 when compared to the values obtained for all other combinations investigated in this series and hence, it is the optimum combination. Hence, good quality bricks can be prepared by combining the black soil and fly ash in equal proportion.
Like the observations made in series 1 investigation, it was observed during the investigation conducted in series 2 that the specimens made by combining soil and waste in the 100% : 0%, 90% : 10%, 80% : 20% and 70% : 30% proportions have developed cracks, the specimens made by combining 0% of soil and 100% of waste were in powder form, the specimens made by combining soil and waste in the 20% : 80% and 10% : 90% proportions have failed partially/completely, and no formation of white deposits was noticed on the surfaces of tested specimens. Hence, similar to the soil-ash bricks, soil-waste bricks can be made by adding 40 to 70% of crusher waste into the soil, and bricks produced using this range have resulted in compressive strength values ranging from 5.62 N/mm2 to 6.06 N/mm2 , water absorption values ranging from 12% to 19% and density values ranging from 13.77kN/m3 to 14.23kN/m3 . The bricks made using soil and waste have shown a higher compressive strength of 6.06 N/mm2 , lower water absorption of 12% and higher density of 14.23kN/m3 at the combination of 40% soil and 60% waste (i.e. 1:1.5 ratio) when compared to the values obtained for all other combinations investigated in this series and hence, it is the optimum combination. Hence, good quality bricks can be made by combining soil and waste in the ratio of 1:1.5.
It was found during the investigation conducted in series 3 that brick specimens made by combining soil, ash and waste in the 100% : 0% : 0% and 80% : 10% : 10% proportions have developed cracks, specimens made by combining 0% of soil, 50% of ash and 50% of waste were in powder form, specimens made by combining 20% of soil,40% of ash and 40% of waste have resulted in partial damage/complete collapse, and no formation of white deposits was noticed on the surfaces of tested specimens. Hence, it is clear that it is possible to make bricks by adding both fly ash and crusher waste into the black soil from 20 to 30%, and bricks produced using this range have shown compressive strength values ranging from 5.16 N/mm2 to 5.55 N/mm2 , water absorption values ranging from 13% to 18% and density values ranging from 13.63kN/m3 to 13.86kN/m3 . Also, it is seen that specimens made by combining 40% of soil, 30% of ash and 30% of waste (i.e. 1:0.75:0.75 ratio) have shown a higher compressive strength of 5.55 N/mm2 , lower water absorption of 13% and higher density of 13.86kN/m3 when compared to the values obtained for all other combinations investigated in this series and hence, it is the optimum combination. Hence, good quality bricks can be prepared by combining soil, ash and waste in the ratio of1:0.75:0.75.
It is seen from the results presented in Table 2 that the values of compressive strength, water absorption and density obtained for soil-ash, soil-waste and soil-ash-waste bricks at the optimum combination ratios are 5.65N/mm2 , 16% and 12.35 kN/m3 ; 6.06N/mm2 , 12% and 14.23 kN/m3 ; and 5.55N/mm2 , 13% and 13.86 kN/m3 , respectively. The corresponding values obtained for the conventional clay bricks are 5.93 N/mm2 ,15% and 14.82 kN/m3 , and for the pressed type water cured cement fly ash bricks are 6.23N/mm2 , 10% and 17.63 kN/m3 , respectively. Thus, it is clear that the results obtained in all three series for various properties of stabilized black soil bricks at optimum combination ratios are in good agreement with the results obtained for clay bricks and fly ash bricks. Besides, bricks tested in all three series for all combination cases studied have shown compressive strength values greater than 3.5 N/mm2 and water absorption values less than 20%. Since these values satisfy the values recommended in IS: 1077 code ([9]), bricks made by using any of the three combination cases (i.e. any of the three series investigated) can be used for the construction activities. Hence, fly ash and/or crusher waste stabilized black soil bricks is a viable alternative to the conventional clay or fly ash bricks.
Based on the experimental investigations carried out in this work, the following conclusions can be drawn: