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

In order to produce reinforced concrete and hollow concrete blocks with good quality whichrnsatisfy strength and durability requirements, great care have to be taken for their productionrnstarting from ingredient selection to finished product. In addition to this, every production processrnshould follow proper scientific procedures. For this, quality control plays a significant rolernbecause qualities of these ingredients and their production process could affect the overall qualityrnof buildings to a higher extent. Quality control comprises a combination of action and decisionrntaken in compliance with specification and checks that these are satisfied.rnConsidering this, investigations focusing on quality control in reinforced concrete and hollowrnconcrete block production has been conducted in projects administered by Addis Ababa HousingrnProject found in various parts of Addis Ababa located in Yeka Ayat II, Yeka Ayat III, YekarnAbado, Bole Arabsa, Kolfe keranyo, tulu dimtu and kelento sites.rnThe research is carried out by collecting information on qualities of ingredients and method ofrnproduction through questionnaires and observation and sample compressive strength test resultrnfrom consultant data file to check their compliance with the help of statistical analysis andrnminimum strength requirement set on recommended standards.rnThe findings of the investigation have shown that in all construction sites, sufficient tests are notrnconducted for all ingredients used for production of reinforced concrete and hollow concreternblocks. Among those ingredients, sand testes by some sites for its silt content using jar test,rnobservation and or both. In addition to this, handling of those ingredients were very poor, duringrnobservation intermixing coarse and fine aggregate, grass grown on the top of sand, reinforcementrnbar rests on the ground… were shown and production process also not conducted properly asrnspecified in the recommended standards.rnAccording to the result of statistical analysis of concrete compressive strength test collected fromrnconsultant data files, the quality control on significant portion of the construction sites are notrngood. As per the classification of ACI 214, the standard deviation of 46.15 % of the compressivernstrength has shown that the quality control is not good. From which, none of them fall in thern“fair” classification range and 46.15 % in the “poor” range; and the coefficient of variation ofrn76.92 % of the compressive strength has shown that the quality control is not good from whichrnStudy on the Effectiveness of Quality Control for Reinforced concrete and Hollow concrete block production of In Projects administered by Addis Ababa housing AgencyrnVIrn15.38 % fall in the “fair” classification range and 61.54 % in the “poor” range. From the analysisrnof compressive strength test result, 35.14%, 14.86% and 21.62% of the projects has shownrndefective lots as per the Ethiopian, the American and the British codes compliance requirementrnrespectively. On the other hand, 40% of hollow concrete block producers don’t conduct test andrnthe remaining 60% of them conduct a test for compressive strength, but the result collected fromrnconsultant data files, can’t comply class C strength of Ethiopian standard for hollow blocks ESrn596:2001.rnThis is an indication that the test results among a significant portion of the investigated projectsrnhave shown large variability implying the quality control is unsatisfactory. It is also observedrnalmost one-third of the construction sites have got defective lots, which fail to satisfy therncompliance requirement set on the Ethiopian building codes and standards.rnKeywords: - Batching, bending, cement, coefficient of variation, compacting, cutting, curing,rnfinishing, mineral aggregates, mixing, placing, quality control, standard deviation, transporting,rntying and water.

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