TY - CONF A1 - Ramge, Peter A1 - Schmidt, Wolfram A1 - Kühne, Hans-Carsten A2 - Uzoegbo, H.C. A2 - Schmidt, Wolfram T1 - Effect of the storage of cement on early properties of cementitious systems T2 - ACCTA - International conference on advances in cement and concrete technology in Africa 2013 (Proceedings) N2 - As soon as cement is mixed with water, the hydration reaction starts to set of. The progression of the hydration process is governed by the amount and the availability of water and its possibility to access the unhydrated cement grain surfaces. For a total hydration cement theoretically requires water amounting approximately 0.38 of its own mass. Nevertheless, due to the cement’s highly hygroscopic nature, already the moisture in the ambient air can cause first hydration reactions to set in upon the cement grain surfaces. Such pre-hydration processes have an effect on the cement's properties. Dpending on the specific conditions during the storage the significance of the impact on certain properties can vary. If cement is consumed soon after production and is transported only short distances in a silo wagon to its final destination for immediate use without further stock transfer, the effects are rather negligible. However, if cement is delivered in bags, transported over long distances, shifted serval times and stored for longer time periods until it is finally consumend, these effects can be quite severe. Due to the actual logistical situation with comparably few cement plants, large delivery distances and partially less developed infrastructures, the latter scenario pictures the situation for the most cases in Africa quite well. In order to verify the relevance of the pre-hydation for practical application, a series of tests was conducted at the German Federal Institute for Materials Research and Testing (BAM). The influence of the cement storage on gresh and hardened concrete properties was investigated for different concrete and mortar types. The investigations show that the impact of the storage conditions is more pronounced for specialized concretes with high sophisticated optimized mixture compositions containing admixtures. Nevertheless, the effects also occur for ordinary concrete and should not be ignored. T2 - ACCTA - International conference on advances in cement and concrete technology in Africa 2013 CY - Johannesburg, South Africa DA - 28.01.2013 KW - Cement KW - Storage KW - Ambient conditions KW - Hydration KW - Pre-hydration KW - Atmospheric humidity PY - 2013 UR - https://opus4.kobv.de/opus4-bam/frontdoor/index/index/docId/27757 AN - OPUS4-27757 SN - 978-3-9815360-3-4 SP - 339 EP - 347 AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany