Search

Introduction/purpose: Concrete, mortar, and cement pastes are materials that have become central in various fields of construction, structures, and civil engineering. About 7 billion cubic meters of concrete are implemented. Concrete is generally considered a homogeneous material, but that is not always the case given its rheological behavior, which can be due to heterogeneous phenomena of segregation and bleeding. Methods: The study tested a concrete column's physical and mechanical characteristics and deformation in elevation. The tests included measuring absolute and apparent density, porosity, capillary absorption, permeability, speed of propagation, compressive strength, and static and dynamic modulus of elasticity. For this purpose, the standards of non-destructive testing (sclerometer, ultrasound, etc.) were used to take the average of a series of points located at different levels of the element to be tested. Results: The results indicate that changes in the column's height affect its physical and mechanical properties, either increasing or decreasing them (such as porosity, absorbency, permeability, compressive strength, and the static and dynamic modulus of elasticity). These changes are influenced by various factors, including the inherent properties of the concrete implementation (such as vibration and curing) and the climate conditions during construction. Conclusion: The findings of this study emphasize the importance of a nuanced approach to testing and evaluating variations in concrete properties by taking into account the multifaceted impact of changes in column height.

The use of blast furnace slag during the manufacture of cement is assumed to mitigate CO2 emissions. Generally, the amount of blast furnace slag in the slag cement (CEMIII) ranges between 36 % and 95 %. Slag cement is suitable for the production of all concrete classes, such as the large-scale civil engineering projects (roads, tunnels, bridges). In the case of tunnels, evaluating the performance of concrete exposed to high temperatures will be of great interest. This paper deals with the mechanical properties of cement pastes and mortars made with an ordinary Portland cement (CEMI) and slag cement (CEMIII) subjected to temperatures up to 650 °C. For this purpose, The test specimens were cured for 90 days and then subjected to four different temperatures (160, 300, 400 and 650 °C) at 1 °C/min. Following the 1 h of thermal load, the specimens were examined once their temperature cooled down to room temperature. Measurements were taken for mass loss, permeability, residual compressive strength and modulus of elasticity for each temperature.The test results demonstrated that permeability increases with temperature, and it follows an exponential type formula for both types of mortar. Where there is more loss of permeability in MIII mortars than in MI mortars.The residual compressive strength of all specimens increased up to 160 °C and decreased with further increase in temperature. This decrease is more significant when the temperature exceeds 400 °C. For all heating temperatures, the samples made from the slag cement (CIII and MIII) show higher residual compressive than those made with Portland cement (CI and MI). Furthermore, it was found that at all exposure temperatures the modulus of elasticity of all samples was more reduced compared to the compressive strength. In conclusion, we can say that when using slag cement, the samples show a good mechanical behavior (compressive strength and modulus of elasticity) at high temperatures and also for permeability.