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The Effect Of Partial Replacement Of Conventional Fine Aggregate (sand) With Lateritic Soil In The Production Of Sandcrete Bricks
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2.5 Water
Water plays an indispensable role in sandcrete brick production. Both the quality and quantity of the water is of great importance. Water is needed during the mixing process and also during the curing period. The quantity of water used in sandcrete brick production is usually expressed in relation to the cement content, hence the term water/cement (w/c) ratio. This ratio must be carefully controlled as it greatly affects the strength, workability and durability of the concrete. A very low w/c ratio will lead to poor hydration of the cement resulting in reduced strength and low durability. The workability of the sandcrete will also be poor. Very high ratios also have similar end effects, as the sandcrete bricks will even flow. The quality of the water is often not given enough attention during sandcrete bricks production. Many dissolved solids and suspended solids in water may greatly affect the quality and strength of the concrete. The Cement and sandcrete bricks Association of Australia (2002) recommends the mixing water for sandcrete bricks to be potable and this is the generally accepted quality for water used in sandcrete production. In some instances, there may be more stringent restrictions placed on mixing water. Impurities that if in high concentration in water may make the water suitable for concrete production include chlorides, suspended solid and sodium sulphate. Allowable maximum amount of impurities in mixing water is given in BS EN 1008 (2002) and ASTM C 1602 (2006). Water with pH value less than 6 or higher than 9 is also not acceptable for concrete production. Sea water contains high level of chloride which can lead to rapid corrosion of the steel reinforcement bars especially when the concrete is porous and no adequate cover is provided for the reinforcement bars. Since these factors cannot always be taken care of, it is advisable to avoid making reinforced sandcrete bricks with sea water (Shetty, 2005). The requirement of water for sandcrete bricks curing is less stringent. However, the water should not contain impurities, dissolved or suspended which will stain or attack the hardened sandcrete instance water with high amount of iron if used for curing could impair the appearance of the sandcrete bricks.
2.6 Manufacture of sandcrete bricks.
The production of sandcrete bricks can be discussed under the following subheadings:
(i) Batching and Mixing (ii) Compaction and Demoulding (iii) Curing and
(iv) Storage and Transportation.
2.6.1 Batching and Mixing
Batching is the process of measuring out the various quantities of the components. This can be done by mass or by volume. Of the two, batching by mass is professionally preferable as it eliminates errors due to the variations contained in a specific volume. However, most producers, especially those that batch manually, use the volume batching process because it is simpler and much more convenient than weight batching. Manual batching is done using head pans, wheel barrows or specially constructed wooden gauge boxes with a bag of cement taken to be twice the volume of a head pan and the same volume as a wheel barrow. The use of the wooden boxes for batching is becoming obsolete. Cements is usually supplied in bags of 50kg net weight. Batching using head pans or wheel barrows does not make for uniformity as these volumes measured are greatly dependent on the state and size of the head pans or wheel barrows. It should be noted that sand is usually supplied wet and it is in this wet condition that it is most often used. The quantity of water added to the mix must therefore be adjusted to compensate for the water in the wet sand. Furthermore, since sandcrete is a zero slump concrete, the amount of mixing water added is of great importance. Too little or too much water will cause the bricks to fail immediately after demoulding. Mixing is done either manually (with shovels or spades) or mechanically (using Sandcrete mixers of various capacities). Large producers generally use mixers. This offers a more uniform and homogenous mix, especially when the volume is large. In manual mixing the components are mixed using shovels or spades and turned over several times until a homogenous mix is obtained. Whatever method is adopted, adequate mixing is necessary to achieve uniform colour and texture between block batches, prevent variations in strength and minimize web cracks (Portland Cement Association, 1975).
2.6.2 Compaction.
Compaction is a very important process in bricks production. Compaction is achieved by mechanical vibration or manual (hand) compaction. Manual compaction is less effective and is adopted by small scale producers. One brick is produced at a time using a locally manufactured mould. The compaction is effected using a tamping rod. Great care is needed in demoulding the bricks in order not to introduce cracks in it. There are basically three types of machines used in bricks moulding in Nigeria. Some of these in addition to compaction also vibrate the blocks. The machine type greatly affects the quality and the required water used in the block production. The three major types of machines are (i) Egg laying machines (ii) Electric vibrating machine and (III) Manual hand press machines.
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ABSRACT - [ Total Page(s): 1 ]ABSTRACT WILL BE HERE SOON ... Continue reading---
CHAPTER ONE - [ Total Page(s): 2 ]CHAPTER ONE1.0 Introduction Lateritic soils are formed in hot, wet tropical regions with an annual rainfall between 750 to 300mm, (usually in areas with a significant dry season) on a variety of different types of rock with high iron content. The location on the earth, that characterize these conditions fall between latitude 35oS and 35oN (Person, 1970).Laterisation is the removal of silicon through hydrolysis and oxidation that result in the formation of laterite and lateritic soil ... Continue reading---
CHAPTER THREE - [ Total Page(s): 7 ]ProcedureAbout 200g of soil sample was passed thoroughly with distilled water to form a uniform paste. A portion of the paste was placed in a brass trough bar (linear shrinkage trough device). The surface of sample was leveled and smoothened off to the brass of the trough bar and the trough was then placed in an oven for 24 hours at temperature of about 105°C. The initial length of the trough bar filled with the soil sample was taken. After 24 hours, the trough bar was brought out of the oven ... Continue reading---
CHAPTER FOUR - [ Total Page(s): 15 ]PERCENTAGE OF STABILIZER ... Continue reading---
CHAPTER FIVE - [ Total Page(s): 1 ]CHAPTER FIVE5.0 CONCLUSIONS, REFERENCE AND RECOMMENDATION. 5.1 Conclusion. Tests
have been conducted to evaluate the suitability of lateritic soils
along Asa dam area Ilorin kwara state and its effect on the strength of
sandcrete bricks when used to replace the conventional fine aggregate,
the following conclusions can be drawn from the analysis of the results:
I. The use of lateritic fine as a partial replacement has a significant influence on the engineering pro ... Continue reading---
REFRENCES - [ Total Page(s): 3 ]REFERENCESAdam, E. A. (2001): Compressed Stabilised earth block manufactured in sudan, A. Publication for UNESCO (online) Available from http://unesdoc.unesco.org.Adepegba, D.A. (1975). “Comparative Study of Normal Concrete which contains Laterite Fines instead of Sand†Building Science; 10:135-41.Agbede, I.O. and Manasseh, V. (2008): use of cement sand admixture in lateritic brick production for low cost housing Leonardo electric Journal of practices and technology, 12, pp163-174.Ak ... Continue reading---
