This paper intends to examine the influence of temperatures on the early age of cement paste hydration, as well as the setting time and the compressive strength of cement paste with the addition of Triethanolamine (TEA) and Triisopropanolamine (TIPA); hence, the mechanisms of TEA, and TIPA at different curing temperatures were explored. The outcomes show that adding 0.05% and 0.1% TEA, and 0.05% and 0.1% TIPA retarded the setting time of cement pastes; however, this retardation depended on both the dosage and the curing temperature. At 23°C curing temperature, both TEA and TIPA could be used as a hardening accelerator at the dosage of 0.05% by cement weight. Adding 0.05% TEA into the cement paste strongly accelerated the hydration of C₃A and increased the early compressive strength, which was more efficient than adding 0.05% and 0.1% TIPA, especially after 8 hours of curing. However, at 50°C curing temperature, as TIPA strongly accelerated the formation of AFt, AFm, CH, using TIPA was more effective than using TEA to enhance the cement paste's compressive strength. These results can offer theoretical direction for the application of cement-based materials adding TEA and TIPA under hot and standard curing temperatures.

This paper presents an experimental campaign and a numerical model that describe a potential application of magnetic nanoparticles (MNP) in oil well cementing pastes. MNP, when subjected to an oscillating magnetic field, can generate a heating effect, which accelerates the cement hydration reaction through thermal activation. This, in turn, reduces the downtime during expensive oil well cementing operations. An experimental campaign was conducted to verify the heating potential of MNP in cement pastes. The obtained results were used to calibrate and validate a numerical model implemented in an optimized computer code, which takes into account the thermo-chemical coupling of the hydration reaction. The early application of the numerical model successfully reproduced the thermal behavior of MNP-blended cement pastes exposed to inductive heating. Furthermore, it has the potential to be extended for simulating the behavior of cement pastes in oil wells during the early ages when the effects of hydration are crucial to consider.

This study examines the application of the maturity method to obtain the ultimate properties of ECC. Within the scope of the study, the maturity method according to the Arrhenius equation was applied to four different ECC mixtures encountered in the literature: the activation energies and the ages at which they achieve ultimate properties were determined. Subsequently, the mixtures were subjected to standard and accelerated curing to reach an equivalent age of 1 year. The properties of the specimens at 1-year equivalent age were determined after both standard curing at 23°C and accelerated curing at 60°C. Thus, both the validity of the maturity method and the effect of accelerated curing in ECC were evaluated. Mechanically, compressive and flexural tests were performed, while non-destructive tests such as ultrasonic pulse velocity, rapid chloride ion penetration, and resonant frequency were used to determine ECC properties. As a result, it was determined that all ECC mixtures achieved their ultimate properties in less than a year. Furthermore, it was revealed that ECC retains its distinctive properties even in the ultimate state. Additionally, while accelerated curing led to a slight decrease in all properties compared to normal curing, it contributed to a slight improvement in deformation capacity. Nevertheless, considering the proximity of the results between normal and accelerated curing, it can be concluded that accelerated curing has the potential to be applied in ECC, and based on the findings, the maturity method has the potential to predict the long-term properties of ECC mixtures.

The use of engineered cementitious composite with polyvinyl alcohol fiber has shown excellent potential in building facilities due to its strain-hardening and multiple-cracking features. However, when polyvinyl alcohol fiber melts at around 230°C, spalling behavior of engineered cementitious composite may occur, weakening the mechanical properties and reducing ductility of high strength engineered cementitious composite. Thus, investigating the fire resistance is of great significance. By adding steel fibers to cementitious composites, qualitative and quantitative comparisons were done through observing appearance changes, spalling extent, surface cracking, mass loss, and residual mechanical properties. Results indicate that steel fiber can increase the risk of spalling and surface cracking in high strength engineered cementitious composite, improve residual mechanical abilities also. The ductility varies with steel fiber content at different elevated temperatures. Scanning electron microscopy results show that more hydration products are produced on the surface of steel fiber at 400°C, which improves interface transition zones between fiber and cementitious materials. However, an oxidation film found on the surface of steel fiber at 800°C triggers negative effect on bridging.

The influence of temperature on the hydration of cementitious materials has been traditionally modelled using the maturity concept and Arrhenius law. This approach yields a single material property, called apparent activation energy (E_a), that describes the whole temperature dependence. Determining E_a experimentally has sparked controversy, such as whether the different properties (e.g., compressive strength, tensile strength, E-modulus) exhibit different E_a, whether a single E_a value exists for the entire hydration process, or whether cement paste and concrete possess the same E_a. Furthermore, studies measuring E_a from elastic modulus measurements are truly scarce, likely due to experimental challenges with measuring this property at early-ages. This work investigated the influence of temperature on the elastic modulus evolution of cement paste and concrete. A single mix for each material was tested with the EMM-ARM (Elasticity Modulus Measurement through Ambient Response Method) methodology under three different isothermal conditions. The resulting elastic modulus evolution curves were used to derive E_a evolution curves from two traditional computation methods: the ‘speed’ method and the ‘derivative of speed’ method. Results showed that the elastic modulus evolution of both materials initially presented a constant E_a, independent of temperature and hydration development as preconized by the classical Arrhenius law. However, as hydration progressed to later stages, the activation energy exhibited evident dependencies on both temperature and hydration levels. Cement paste and concrete consistently exhibited different E_a values throughout hydration, with concrete having higher values. The use of the E_a curves to superimpose the different experimental elastic modulus evolution curves by means of the equivalent age concept led to near-perfect superpositions, strengthening the validity of this concept when applied to elastic modulus evolution.

Over the past years there has been an increasing trend to use supplementary cementitious materials in concrete to improve its sustainability credentials and durability properties. Perhaps amongst the most popular supplementary cementitious materials is ground granulated blast-furnace slag (GGBS). While the hydration and setting characteristics of mixes with GGBS cured under standard conditions (20°C) has been adequately investigated, the effect of temperature on heat of hydration and setting and the interrelation of these properties has not been evaluated for GGBS containing mixes. In this study, the heat of hydration and setting behaviour of mixes with various levels of GGBS (0, 20, 35, 50 and 70%) cured under elevated temperatures (20, 30, 40, 50 and 60°C) is determined. Elevated curing temperature accelerates the hydration reactions and can significantly reduce the setting time of GGBS-containing mixes. The investigation of heat of hydration at very early ages, can provide an indication of the initial and final setting times of cementitious mixes. The “apparent” activation energy used to characterise temperature sensitivity of cementitious systems, is calculated based on heat of hydration and setting time measurements. It was found that the “apparent” activation energy increases with GGBS content for both heat of hydration and setting behaviour. The value of “apparent” activation energy differs significantly depending on the material property that is considered, such as compressive strength, heat of hydration or setting time.