|Title of Invention||
A COMPOSITION AND A PROCESS FOR PRODUCING BRICKS FROM FOUNDRY RETURN WASTE SAND
|Abstract||The invention relates to the process of making bricks from return sand of foundry waste wherein the process involves steps of preparing the synergestic composition of building bricks by compressing the waste sand, soil, slag and water in a proportion alongwith cement of an amount of 7% -10% by weight as a binder, in a compactor to provide a mixture of wet compressive strength of at least 43 to 45 kg/cm.sup.2, then molding the mixture in a press to form green solid brick, then removing the green brick from the mold and transporting the green brick to a shaded area for curing for 7 days, and then the curing bricks are covered with straw or gunny bag and sprayed with water and finally to form building brick with relatively low porosity, high compressive strength, and low thermal conductivity.|
|Full Text||The second object of the invention is to use waste sand produced by foundries to produce useful products.
The third object of the invention is to provide solid bricks produced by hand compressing together waste sand along with soil, slag and cement and without using heat during the curing period.
The fourth object of the invention is to provide solid bricks, wherein the bricks are not baked in kiln.
The fifth object of the invention is to provide a process, wherein the bricks may be made at the site where bricks are required.
The sixth object of the invention is that these bricks shall have sufficient structural strength for use in building and construction.
SUMMARY OF INVENTION
A process for producing waste sand-cement bricks of bulk density of around 1.90 - 2.00 g/cc and having a wet compressive strength of at least 27-28 kg/cm.sup.2 at 7days and 43-45 kg/cm.sup.2 at 28 days in which at least 8-10% by weight of cement is added to a mixture of foundry return waste sand, cement and water and the mixture is then compacted in molds by compression or under a load of 12000 kgs to form bricks which are subsequently cured.
DESCRIPTION OF THE INVENTION
The invention relates to a process of producing waste sand bricks with a bulk density of around 1.90 - 2.00 g/cc and a wet compressive strength of 43 to 45 kp/cm.sup.2 (at 28 days) wherein a mixture of foundry return waste sand, soil, slag .cement and water is produced and then compressed in moulds of a compactor to form green bricks which are subsequently cured in an open air in shaded area.
Stabilised soil cement blocks are manufactured using locally available soil and cement. The best suited soil for block making will have clay between 10 to 15%, sand between 80 to 85% and silt around 5%
The naturally available soil is to be tested for clay content primarily. The clay content has to be between 10 to 15% If the clay is less or more, the soil is to be conditioned to reach the level of 10 to 15% clay content by suitable additions of sand / slag / clay etc., as required. Stabilization is generally carried out with cement or lime.
In one of the embodiments the soil and foundry return waste sand used for block making is sieved through 4 mm. The sieved material is thoroughly dry mixed with 7 to 10% cement depending on the strength required. To the cement soil mix, water is added (10% of weight of mix) till the sand reaches the mouldable consistency. This sand is moulded in a hand press to achieve a specific gravity of 2 to 2.05 gm/cc. The mould soil cement block is taken out and stacked under shade. The blocks are covered with straw or gunny bag and water is to be sprayed for 7 days to cure the blocks.
The blocks generally acquire the strength in 7 days and to increase the strength it can be cured for more number of days. These blocks do no use any fuel for curing . Hence environmentally friendly.
The present invention is to achieve a brick of good green compressive strength so that bricks produced in accordance with the process described in the invention can be handled, used and conveyed by the previously known methods and devices applicable to any of the kiln heated conventional bricks. The term "brick" in the specification and claims includes a waste sand building block of any shape and size and is not limited to a typical square or rectangular shaped bricks known in prior art.
This problem of damage of brick and low strength suffered in prior art with the conventional process bricks is solved in accordance with the invention by adding at least certain percentage by weight of cement to the mixture and then compressing/pressing the mixture in a compactor or a hand pressure at pressures of not less than 30 kg/cm.sup.2. Prior to the compacting operation the cement, which acts as a binder is added to the mixture consisting essentially of foundry return waste sand, soil and slag.
By using cement as a binder, bricks are made with the particle size of less than 1.4 mm and down size in the foundry return waste sand and in the soil from 3.5 mm and down size. This makes the bricks are made with uniformly distributed particles. The cement acts a strengthener and simultaneously acts as a binder in the composition.
The invention in further aspects has bricks having a porosity of .less than 10%.(Equivalent to moisture absorption capacity). This porosity can be produced in all brick sizes in use to improve heat insulating properties without the strength of the bricks falling below the required value. So with this process irrespective of shape and size of the brick, the porosity and density can be retained at the desired level.
In accordance with a further proposal of the invention the mixture after addition of the cement, is vibrated or acted upon by any other known means which induce mixing.
The invention makes use of foundry return waste sand in place of natural soil, which is the essence of the invention.
In sand foundry, the moulds are produced using a mix of foundry return sand, bentonite (clay), coal dust and water. The moulding sand gets recycled continuously to the extent of 98%. The foundry sand due to continuous recycling
Hence the idea is to use foundry return waste sand in soil cement block making in place of natural soil. The invention as such finds use for foundry return waste sand to produce a much required strong but cheap bricks. The process of making the bricks is simple and the invention can be put to work at any place, as it hardly involves any heavy machinery.
Experiments were conducted by using foundry return waste sand to an extent of 50 to 80% with cement at a constant rate of 7%. The blocks produced were tested for wet compressive strength after 7 days of curing and 28 days of curing. The results are tabulated as below: -
This clearly shows that with varying proportions of foundry return waste sand, the strength specific gravity and water absorption remains almost constant.
Hence further experiments were conducted to assess the wetting and drying capabilities to study the behaviour of block due to weathering for external wall applications.
1. With a higher foundry return waste sand content of 70 to 80% the edges of the blocks got eroded after 2 to 3 cycles (Alternate wetting & drying)
2. With foundry return waste sand content of 50 to 60% the edges of the blocks withstood erosion after more than 5 cycles.
3. With a foundry return waste sand content 60 to 70%, the edges of the blocks withstood erosion between 3 to 4 cycles.
Hence the foundry return waste sand proportion was fixed at 50 to 60% balance being natural soil for external walls and 6o to 70% of the return waste sand for internal walls.
Further studies were conducted to reduce the water absorption (to prevent more shrinkage Hence cement content was increased to 9 to 10% in place of 7% The results are tabulated as below: -
Hence the foundry return waste sand % is fixed between 50 to 60% max for external wa!ls(walls exposed to weather) with appropriate cement quantity varying from 9 to 10% to give adequate wet comp. Strength and less water absorption(The lesser the absorption of water better will be the strength)
Finally the invention proposes that the compacting of the mixture be effected by vibration or agitating process acting on the moulds. This leads to the compactor being particularly simple in design.
Firstly and currently, there is also a need in India for inexpensive housing. Secondly, invention provides a solution to the disposal problem posed by the production of tons of waste sand by sand foundry industries. Finally, the invention also provides a solution to the problem of providing relatively inexpensive construction material for housing and other purposes.
The invention provides solid bricks produced by the invention process of compressing a mixture of foundry return waste sand and cement. These solid bricks have a relatively low porosity, high compressive strength, and low thermal conductivity so that they are suitable for use in constructing homes for walls in place of conventional bricks.
The invention provides solid bricks produced by an invention process that Compresses soil, slag and cement together with a waste product, such return waste sand waste of a foundry. The invention process includes several steps, including a step of moulding in a press the mixture to produce a solid brick.
Furthermore, the invention needs only a mobile apparatus like a hand press that can be taken to practice the invention process with the supply of the foundry return waste sand made thereat the site. This mobility allows significant savings in terms of avoided handling and transportation of foundry return waste sand to manufacturing centre for processing.
The invention provides a unique and useful process for disposal of significant quantities of waste created in foundry factories and for relieving pressure while also providing a relatively inexpensive material suitable for use in many construction applications, including housing. Further, the invention saves significant amounts of energy in providing a invention that can be made at the spot of need, thereby avoiding the expense and energy needed to transport large
waste and creating a new product as a substitute for kiln baked bricks at a much lower cost made by a very simple but novel process.
Comparison between blocks made with foundry return waste sand and bricks
The present invention addresses itself to the problems mentioned previously and provides a composition which utilizes industrial waste amongst other ingredients for producing bricks which are lighter and stronger than the conventional bricks.
The present invention employs the technique of preparing a synergistic composition by mixing foundry return waste sand, soil, slag and cement in a fixed proportion so as to strike a synergistic balance.
From the foregoing description, it is abundantly clear that the brick composition of the invention results in a substantially lighter and unexpectedly stronger building bricks.
The foregoing examples demonstrate the synergistic nature of the composition.
1. A process for producing a waste sand-cement building brick and of bulk density of around 1.90 to 2.00 glee comprising the steps of:
(a) preparing a mixture of foundry return waste sand, soil, slag, water and cement, said mixture consisting essentially of waste sand, slag, soil and water and also including an amount of cement as a binder wherein the said foundry return waste sand is present in an amount of 50-70% by weight, said slag be present in an amount of 5-10% by weight, said cement being present in an amount of 7-10% by weight and said soil been present in an amount of 20-30% by weight;
(b) compacting said prepared mixture in a mold at a pressure of not less than 30kg/cm.sup.2 to form green brick with a hand press;
(c) removing said green brick from said mold;
(d) transporting said green brick to a shaded area; and
(e) curing said green brick in the shaded area to form said building brick.
2. The process as worded in claim 1, wherein the curing bricks are covered with straw or gunny bag.
3. The process as worded in claim 1, wherein the curing bricks are sprayed with water during the curing period.
4. The process as worded in claim 1, wherein the curing period is 7 days.
5. The process as worded in claim 1, in which the foundry return waste sand has a particle size of less than 1.4 mm.
6. The process as worded in claim 1, in which the cement is a ordinary port land cement.
7. The process as worded in claim 1, in which the bricks have a porosity of at less than 10%.
8. A synergistic composition for making bricks comprising a mixture of (a) foundry return waste sand from foundry waste present in an amount of from 50% to 70%, (b) slag in an amount of from 5 % t010 % from foundry waste (c) soil present in the amount of from 20 % to 30%, and (d) cement present in an amount of 7% to 10%, wherein the percentages are by weight of the total composition.
|Indian Patent Application Number||961/CHE/2006|
|PG Journal Number||48/2011|
|Date of Filing||05-Jun-2006|
|Name of Patentee||BRAKES INDIA LIMITED|
|Applicant Address||No.21, Patullos Road, Chennai 600 002|
|PCT International Classification Number||B65B13/00|
|PCT International Application Number||N/A|
|PCT International Filing date|