Abstract
The volume changes of cement based composites are significantly exhibited in the hardening process. Initial phases of the hardening are complemented by the expansion due to the heat evolution that is subsequently alternated by the shrinkage. Both could cause a crack initiation. It is evident that ultimate volume changes of cement based composites are a complex process, because the final shrinkage is determined by the binder used, exposition and also by the previous history. The paper focuses on the evaluation of the main types of cements based on the Portland clinker by using a conventional procedure for the determination of the shrinkage on the standard cements mortars. These mortars were exposed to drying after 1 and 3 days of curing, related to the actual degree of hydration, which was estimated on the basis of compressive strength development. The hydration process was additionally monitored using thermogravimetry on the accompanying paste specimens during one year. The performed experimental program confirmed the essential sense of the curing regime especially for blended cement systems, which exhibited very low values of the hydration degree at applied curing intervals. Despite the slightly higher values of shrinkage of blended cements, the obtained results signalize the crucial effect of prolonged curing for these types of binders. The conclusion highlighted the necessity of taking into consideration the hydration degree during cement testing by using the conventional contact method. Otherwise, the simple interpretation leads to an overestimation of the less-suitable material solution.
Highlights
The cement-based-composites and related products represent a significant part of construction engineering
The reduction of the hydration heat was historically solved by the use of belite cement, currently, the application of supplementary cementitious materials (SCM) is preferred [13]
A special attention was paid to their predisposition to the drying shrinkage the measurement of the shrinkage was conducted for various curing regimes
Summary
The cement-based-composites and related products represent a significant part of construction engineering Their significance is a result of good physical properties and good availability of raw materials. The ultimate volume changes are closely related to the hydration process for cement based composites and conventional concrete. Thanks to the detailed description of individual clinker components, the prediction of ultimate volume changes using advanced techniques could be conducted [10, 11] These models take into account the dimensions of the produced element and, on the basis of calculated hydration heat, estimate the resulting vol no. The reduction of the hydration heat was historically solved by the use of belite cement, currently, the application of supplementary cementitious materials (SCM) is preferred [13] It is partially motivated from the environmental point of view, because these materials come from waste or by-products. CaO SiO2 Al2O3 Fe2O3 MgO SO3 K2O Na2O LOI Blaine [%] [%] [%] [%] [%] [%] [%] [%] [%] [m2/kg]
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