Assessment of hollow concrete blocks production in micro and small scale enterprises: a case study in aksum town.

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.