Study on the Effectiveness of Quality Control for the Production of Reinforced Concrete and Hollow Concrete Blocks (In projects administered by Addis Ababa housing Projects
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Date
2014-12
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Addis Ababa University
Abstract
In order to produce reinforced concrete and hollow concrete blocks with good quality which
satisfy strength and durability requirements, great care have to be taken for their production
starting from ingredient selection to finished product. In addition to this, every production process
should follow proper scientific procedures. For this, quality control plays a significant role
because qualities of these ingredients and their production process could affect the overall quality
of buildings to a higher extent. Quality control comprises a combination of action and decision
taken in compliance with specification and checks that these are satisfied.
Considering this, investigations focusing on quality control in reinforced concrete and hollow
concrete block production has been conducted in projects administered by Addis Ababa Housing
Project found in various parts of Addis Ababa located in Yeka Ayat II, Yeka Ayat III, Yeka
Abado, Bole Arabsa, Kolfe keranyo, tulu dimtu and kelento sites.
The research is carried out by collecting information on qualities of ingredients and method of
production through questionnaires and observation and sample compressive strength test result
from consultant data file to check their compliance with the help of statistical analysis and
minimum strength requirement set on recommended standards.
The findings of the investigation have shown that in all construction sites, sufficient tests are not
conducted for all ingredients used for production of reinforced concrete and hollow concrete
blocks. Among those ingredients, sand testes by some sites for its silt content using jar test,
observation and or both. In addition to this, handling of those ingredients were very poor, during
observation intermixing coarse and fine aggregate, grass grown on the top of sand, reinforcement
bar rests on the ground… were shown and production process also not conducted properly as
specified in the recommended standards.
According to the result of statistical analysis of concrete compressive strength test collected from
consultant data files, the quality control on significant portion of the construction sites are not
good. As per the classification of ACI 214, the standard deviation of 46.15 % of the compressive
strength has shown that the quality control is not good. From which, none of them fall in the
“fair” classification range and 46.15 % in the “poor” range; and the coefficient of variation of
76.92 % of the compressive strength has shown that the quality control is not good from which
Study on the Effectiveness of Quality Control for Reinforced concrete and Hollow concrete block production of In Projects administered by Addis Ababa housing Agency
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15.38 % fall in the “fair” classification range and 61.54 % in the “poor” range. From the analysis
of compressive strength test result, 35.14%, 14.86% and 21.62% of the projects has shown
defective lots as per the Ethiopian, the American and the British codes compliance requirement
respectively. On the other hand, 40% of hollow concrete block producers don’t conduct test and
the remaining 60% of them conduct a test for compressive strength, but the result collected from
consultant data files, can’t comply class C strength of Ethiopian standard for hollow blocks ES
596:2001.
This is an indication that the test results among a significant portion of the investigated projects
have shown large variability implying the quality control is unsatisfactory. It is also observed
almost one-third of the construction sites have got defective lots, which fail to satisfy the
compliance requirement set on the Ethiopian building codes and standards.
Keywords: - Batching, bending, cement, coefficient of variation, compacting, cutting, curing,
finishing, mineral aggregates, mixing, placing, quality control, standard deviation, transporting,
tying and water.
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Keywords
Batching, Bending, Cement, Coefficient of Variation, Compacting, Cutting, Curing, Finishing, Mineral Aggregates, Mixing, Placing, Quality Control, Standard Deviation, Transporting, Tying and Water