Development of a versatile method for on-site cement quality testing.
Yusuf, Abdullahi Mohamud
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Cement is a vital component of concrete that determines various physical and chemical properties and behaviors of concrete. The most common type of cement used for concrete is Portland cement. Cement is used to bind fine and coarse aggregate (sand and gravel or crushed limestone or granite) into a thick, coherent mass (Bye, et al., 2011).In order to bind matter into a coherent mass, Cement undergoes an exothermic hydration reaction with a reduction in volume. This reduction is called chemical shrinkage. Therefore, some parameters from the reaction like heat of hydration and chemical shrinkage can be used to study and monitor cement quality. In many countries especially in Sub-Saharan Africa, quality control measures are poor because these countries do not have enough labs. There are no preliminary on-site tests that can check whether the cement to be used in concrete batching is of adequate quality. Site records on the cement, sand and aggregates used and test samples of every concrete batch must be submitted to a regulating body to check whether the design requirements have been met. In Uganda the main regulating body is the Ministry of works and in the capital city the regulating body is Kampala Capital City Authority. The site records should also include records of the slump, structural element and location of the batch sample (Building and Construction Authority, 2021 ). A satisfactory certificate of test issued by any recognised physics laboratory or building or industrial research Centre or any public works department in East Africa will be accepted as proof thereof (WHO, 1969). The chemical tests conducted for the quality of cement by UNBS according to the East African (Ugandan) standards include initial setting time, soundness, Heat of hydration and chemical requirements like Loss on ignition, Insoluble residue, Sulphate Content and many others but do not consider chemical shrinkage (EAS, 2017). Existing Tests to determine whether concrete has attained the required strength do not first check the quality of cement first but like ASTM C39 are either generally conducted 7days and then 28days after casting. Others are conducted after the concrete has attained significant strength for example the Schmidt hammer.