Abstract:
The Ethiopian government has given priority to micro and small scale enterprises which have
a significant contribution in the infrastructure development of the country. These enterprises
include different sectors like manufacturing, service and construction industry etc. This study
focuses on the construction industry, production of prefabricated building elements,
particularly hollow concrete block products. In order to produce 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.
The laboratory tests on the compressive strength of hollow concrete blocks were conducted on
18 blocks sample with different size from each enterprise. The sampling technique was
random sampling method that taken particularly from newly or fresh produced concrete
blocks. The ratio was 1:12 and mold sizes were 10x20x40 cm, 15x20x40 cm and 20x20x40
cm. The samples were tested for compressive strength at the ages of 28 days.
The research was carried out by conducting laboratory test on randomly selected 18 blocks
samples and collecting primary and secondary data through questionnaires interview and
observation. Questionnaires interview and observation were employed to assess the qualities
of ingredients and method of production. Compressive test were conducted to evaluate the
compression strength of the hollow concrete blocks. The compressive test results of the
sampled hollow concrete blocks were evaluated 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 producers, sufficient tests are not
conducted for all ingredients used for production of hollow concrete blocks, In addition to
this, handling of those ingredients was poor, intermixing of sand and aggregate was
observed, and production process was also not conducted properly as specified in the
recommended standards.
According to Ethiopian standard (ES 596:2001) the results were not affected in case of
material quality but the final outputs of HCB were poor, these because of lack of mixing ratio
the result were decreases. All producers attain Class D, and this was based on compressive
strength result and its density.
These were an indication that the test results among a significant portion of the investigated
projects have shown large variability implying the quality control is unsatisfactory.
