Abstract
Microstructure development of concrete, mortar, and paste scale of cement-based material (CBM) during the early hydration stage has a significant impact on CBM’s physical, mechanical, and durability characteristics at the high maturity state. The research was carried out using compositions with increased autogenous shrinkage and extended early age period, proposed within the RRT+ programme of the COST Action TU1404. The electrical conductivity method, used to follow the solidification process of CBM, is capable of determining the initial and final setting time, and the end of the solidification process acceleration stage for the paste and mortar scale. Simultaneous ultrasonic P- and S-wave transmission measurements revealed that the ratio of velocities VP/VS is highly dependent on the presence of aggregates—it is considerably higher for the paste scale compared to the mortar and concrete scale. The deviation from the otherwise roughly constant ratio VP/VS for each scale may indicate cracks in the material. The non-linear correlation between the dynamic and static elastic moduli valid over the three scales was confirmed. Additionally, it was found that the static E-modulus correlates very well with the square of the VS and that the VS is highly correlated to the cube compressive strength—but a separate trendline exists for each CBM scale.
Highlights
Formation and development of cement-based materials’ (CBMs) internal structure is a complex process that depends on various influencing parameters—such as the type of cement, aggregate, water-to-cement ratio, presence of chemical admixtures, and/or mineral additives, temperature, curing conditions, etc
Upon reaching this high state of maturity, the corresponding time is known as an early hydration period that varies from several hours to a few days or even weeks, depending on the CBM’s composition and curing conditions
Simultaneous P- and shear wave (S-wave) transmission velocity measurements confirmed the correlation between the compressive or tensile strength and dynamic elastic modulus at the early age of CBMs [12]. These findings indicate that the elastic parameters are valid solidification indicators, with which the development of other mechanical characteristics of CBMs can be evaluated at an early age
Summary
Formation and development of cement-based materials’ (CBMs) internal structure is a complex process that depends on various influencing parameters—such as the type of cement, aggregate, water-to-cement ratio, presence of chemical admixtures, and/or mineral additives, temperature, curing conditions, etc. After the solid-state is reached, ongoing hydration reactions result in a high state of CBM’s maturity that is reflected in the low rate at which the material’s strength and elastic properties are changing with time. Upon reaching this high state of maturity, the corresponding time is known as an early hydration period that varies from several hours to a few days or even weeks, depending on the CBM’s composition and curing conditions. Understanding microstructure development in CBMs in this early hydration period is fundamental, as it has a significant impact on the physical, mechanical, and durability characteristics of CBMs
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