Study of Stabilized Mud Block as an Alternative Building Material and Development of Models
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Date
2012-01
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Addis Ababa University
Abstract
Soil or earth as a building material is available in most areas of the world. In developing
countries, earth construction is economically the most efficient means for house construction
with the least demand of resources. But, traditional earth construction techniques such as Wattle
and Daub (in Ethiopia “Chika bet’’) and Cob suffer from water attack or erosion by rain and
shrinkage cracks. Therefore, they need to be continuously maintained in order to keep them in
good condition.
This thesis studies the effect of the proportion between the soil and the stabilizers (such as
cement and straw fiber) on stabilized earth blocks durability. It also compares mechanical
properties (compressive strength and shrinkage) of stabilized earth blocks which are prepared
using only local soils (which is taken from Yeka sub city Addis Ababa area) and with the
addition of stabilizers (cement and straw fiber).
This research provides detailed technical information on suitable earth construction such as
stabilized earth blocks production. These include information on suitable soil types for stabilized
earth house construction, stabilizers and production of stabilized earth blocks. Related literatures
review show that soil types, proportions between soil and stabilizer amount and compaction
pressure applied to the moist soil mix affects the quality of the stabilized earth block.
Since soil in Yeka area of Addis Ababa is not much exposed to waste products (pollution), this
soil was found to be the most suitable site for the test. Laboratory tests were conducted on Yeka
area soil and provided detailed information on the soil grading (grain size). The result was
compared with standard values to verify suitability of the soil for soil stabilized earth block
production. It is possible to determine the suitability of other area soils by applying the same
technique.
Using soil (from Yeka area of Addis Ababa) and stabilizers (cement and straw fiber), six
different types of samples were prepared. Tests were conducted on these samples in order to
evaluate their performance such as compressive strength and total water absorption on which the
durability of the blocks depend. The effect of the cement and the straw fiber content in stabilized
mixture was evaluated and comparisons were made. For all block samples, their shrinkage value
(after drying process) was calculated in percents and compared with recommended values.
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The investigation has revealed that, out of all block samples, blocks which are produced from
5% cement (5C), 2% cement with 3% straw fiber (2C3S) and 2% cement with 6% straw fiber
(2C6S) have compressive strength, dry shrinkage and total water absorption values above the
recommended minimum values for structural work.
Finally, a possible model for manually operating earth block making machine and sieving
machine were modeled and designed using Solid works 2007. These machines could be used in
production of uniform and durable stabilized earth blocks.
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Mechanical Engineering