21-09-2012, 12:50 PM
The Use of Rice Husk Ash in Low - Cost Sandcrete Block Production
INTRODUCTION
In olden days, soils with some percentage of silt and clay were used for building non-load bearing walls. Formation of cracks within a short time due to lack of binding materials (such as cement) and considerable amount of shrinkage, they are not being used these days. We can see such soil made walls in ancient cities in our country.
These days, laterite blocks, sandcrete, fired clay bricks etc are being used for construction. Sandcrete is made of proportion of cement and sand. As we are aware that the price of cement is increasing and the availability of river sand is decreasing these days, the production of sandcrete becomes expensive. As a result of this ever-increasing cost of these constituent production materials, and with the increasing demand, the price of sandcrete blocks has correspondingly increased. Majority of the country’s population finds it difficult or almost impossible to afford the cost.
Due to demands for housing, depletion of traditional building materials and expensive conventional building materials, the need for locally manufactured building materials can hardly be overemphasized.
SANDCRETE
The term sandcrete comes from "concrete" by replacing the first syllable "con" with the word "sand". This makes it clear that this material contains only sand as an aggregate and no stones. It is relatively new compared to other materials but they are not economical as sand isn’t so abundant now in our country.
CONCRETE
It is used like any other masonry unit to build foundations, walls etc. a typical concrete block is equivalent to 4.5 bricks, thus construction is faster. Mortar used is lesser making it cost saving. It is very popular in urban areas because of its durability and low maintenance.
LATERITES BLOCKS
Laterite is an old term for heavily weathered subsoil, rich in oxides of iron, aluminum, or both ranging from reddish yellow to dark brownish red in color. They are generally formed in hot and wet tropical areas and are formed from leaching of sedimentary, metamorphic, volcanic rocks and mineralized proto-ores.
PARTICLE SIZE DISTRIBUTION
In above graph, we can see that the particle size distribution of laterite is stepped. That shows the sample is poorly graded. The curve for pure sand is smooth, that is well graded. The curve showing particle size distribution of mix of laterite and sand is smooth, showing that the poorly graded laterite soil was greatly improved by the addition of sand. Specific gravity of 2.95 and 2.90 was obtained when laterite was admixed with 30 and 45% sand respectively [Ref 1]. The addition of 45% sand to the laterite increased the coarse sand component of the laterite from 30% to 53% while medium sand component or the percentage passing through the 600 μm sieve increased from 20% for natural laterite to 40%.
COST ANALYSIS
The cost of different construction materials is compared with those of laterite bricks. Costs include production cost, transportation cost, installation cost (number of bricks and amount of binder used) etc. So in economic view, all these costs are evaluated and overall economy is determined.
In carrying out cost comparison, it should not be based on the production cost per brick. Utilization cost for comparative purposes should include handling charges, cost of transportation and mortar consumption. That mean the economy of using a construction material will not depend only on one aspect like cost of production (labour and extraction), but it will be the combined effect of all cost spend on each brick.
The table below given gives the comparative rates of building materials available [Ref 1]. This table was evaluated in Nigeria during the year 2007-2008. In Nigerian states, abundant lateritic soil deposits exist which can be harnessed for brick production. In Kerala also laterite is available in plenty as discussed earlier.
CONCLUSION
1. Particle size distribution curve of the laterite used in this study was poorly graded and addition of 45% sand corrected this deficiency.
2. Addition of 45% sand content by dry weight of laterite enhanced its suitability for use in the production of bricks within the optimum cement content of 5%.
3. Cost analysis showed that laterite bricks save more money when used instead of fired clay bricks or sandcrete. (According study in Nigeria)
4. Since, like in Nigeria, Kerala has plenty of laterite soil sources, the production and use of laterite bricks will be economical.
5. The optimum cement content of 5% cement keeps the laterite bricks in the economical limit.
6. Laterite cement bricks can be used for low cost construction.
INTRODUCTION
In olden days, soils with some percentage of silt and clay were used for building non-load bearing walls. Formation of cracks within a short time due to lack of binding materials (such as cement) and considerable amount of shrinkage, they are not being used these days. We can see such soil made walls in ancient cities in our country.
These days, laterite blocks, sandcrete, fired clay bricks etc are being used for construction. Sandcrete is made of proportion of cement and sand. As we are aware that the price of cement is increasing and the availability of river sand is decreasing these days, the production of sandcrete becomes expensive. As a result of this ever-increasing cost of these constituent production materials, and with the increasing demand, the price of sandcrete blocks has correspondingly increased. Majority of the country’s population finds it difficult or almost impossible to afford the cost.
Due to demands for housing, depletion of traditional building materials and expensive conventional building materials, the need for locally manufactured building materials can hardly be overemphasized.
SANDCRETE
The term sandcrete comes from "concrete" by replacing the first syllable "con" with the word "sand". This makes it clear that this material contains only sand as an aggregate and no stones. It is relatively new compared to other materials but they are not economical as sand isn’t so abundant now in our country.
CONCRETE
It is used like any other masonry unit to build foundations, walls etc. a typical concrete block is equivalent to 4.5 bricks, thus construction is faster. Mortar used is lesser making it cost saving. It is very popular in urban areas because of its durability and low maintenance.
LATERITES BLOCKS
Laterite is an old term for heavily weathered subsoil, rich in oxides of iron, aluminum, or both ranging from reddish yellow to dark brownish red in color. They are generally formed in hot and wet tropical areas and are formed from leaching of sedimentary, metamorphic, volcanic rocks and mineralized proto-ores.
PARTICLE SIZE DISTRIBUTION
In above graph, we can see that the particle size distribution of laterite is stepped. That shows the sample is poorly graded. The curve for pure sand is smooth, that is well graded. The curve showing particle size distribution of mix of laterite and sand is smooth, showing that the poorly graded laterite soil was greatly improved by the addition of sand. Specific gravity of 2.95 and 2.90 was obtained when laterite was admixed with 30 and 45% sand respectively [Ref 1]. The addition of 45% sand to the laterite increased the coarse sand component of the laterite from 30% to 53% while medium sand component or the percentage passing through the 600 μm sieve increased from 20% for natural laterite to 40%.
COST ANALYSIS
The cost of different construction materials is compared with those of laterite bricks. Costs include production cost, transportation cost, installation cost (number of bricks and amount of binder used) etc. So in economic view, all these costs are evaluated and overall economy is determined.
In carrying out cost comparison, it should not be based on the production cost per brick. Utilization cost for comparative purposes should include handling charges, cost of transportation and mortar consumption. That mean the economy of using a construction material will not depend only on one aspect like cost of production (labour and extraction), but it will be the combined effect of all cost spend on each brick.
The table below given gives the comparative rates of building materials available [Ref 1]. This table was evaluated in Nigeria during the year 2007-2008. In Nigerian states, abundant lateritic soil deposits exist which can be harnessed for brick production. In Kerala also laterite is available in plenty as discussed earlier.
CONCLUSION
1. Particle size distribution curve of the laterite used in this study was poorly graded and addition of 45% sand corrected this deficiency.
2. Addition of 45% sand content by dry weight of laterite enhanced its suitability for use in the production of bricks within the optimum cement content of 5%.
3. Cost analysis showed that laterite bricks save more money when used instead of fired clay bricks or sandcrete. (According study in Nigeria)
4. Since, like in Nigeria, Kerala has plenty of laterite soil sources, the production and use of laterite bricks will be economical.
5. The optimum cement content of 5% cement keeps the laterite bricks in the economical limit.
6. Laterite cement bricks can be used for low cost construction.