ON QUALITY OF CEMENT SUPPLIED TO CONSUMER
Bernstein L. G. General Director of the Research Centre «Giprocement–Nauka»
Polozov, G. M. Candidate of Technical Sciences, Deputy Director for Research, Tsementergoretsikling LLC, St. Petersburg, Russia
Alitinform №2 (09) 2009 г. 101-104 p.
Production and consumption of cement is inextricably intertwined with production of concrete and concrete products, as well as with construction. Under contemporary conditions, this chain of relations has a complex pattern, especially as for logistics. Cement, going via the whole chain, is exposed to external impacts, such as: rehandling from one container to another one, transportation, mixing with other cement sorts or other materials, atmospheric influence, moisture contained in pressure air, and others. All those factors lead to changes in the core property of cement — its activity. Unpredictable changes in cement activity result in over–consumption of cement for production of concrete and reinforced concrete products, and also to a lack of stability in their properties, therefore to the reduction of safety of construction, buildings and structures.
Quality of concrete is influenced by properties of its components, correct composition and adherence to technological procedures. As stipulates the state standard GOST 18105, deviations in the strength of concrete from one product to another one, or from one batch to another one should not exceed ± 6–8%. In order to meet this requirement, it is necessary to stabilize properties and consumption of all concrete components, such as crushed stone, sand, cement, reinforcing elements and chemical admixtures. Consumption of sand and crushed stone should be kept with accuracy of 1%, according to the GOST. Requirements for flakiness of sand and crushed stone, content of powder and clay fractions, fraction composition of sand and crushed stone are also specified by the GOST.
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