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1. Understanding the role of a novel internal conditioning technique with functionalized montmorillonite in cement hydration kinetics

   https://doi.org/10.1016/j.conbuildmat.2023.131223  

   Luo, Dayou; Wei, Jianqiang (July 2023, Construction and Building Materials)

   A novel internal conditioning (InCon) technique based on saturated sodium montmorillonite (sMT) functionalized with two non-ionic surfactants, polyoxyethylene (9) nonylphenylether and t-octyl phenoxy poly ethoxyethanol, is investigated in this study. With the integration of water for internal curing and pozzolanic reactivity in a single system, the role of InCon in modifying cement hydration kinetics is comprehensively elucidated. The results indicate that, in the presence of InCon, both silicate reaction and secondary aluminate reaction rates are enhanced, and the apparent activation energy (Ea) of cement hydration was decreased from 34.3 KJ/mol to 28.7 KJ/mol indicating a lower temperature sensitivity and threshold of the cement hydration reactions. In addition, decreased CH contents, improved degree of hydration, increased chemical shrinkage, and the formation of additional Csingle bondSsingle bondH and aluminum-containing phases were obtained from the cement with InCon. The autogenous shrinkage of cement and the negative impact of dry sMT on the early age strength of cement can be offset by InCon paving a new path to improve the overall properties of concrete. 

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2. Recent developments in reactivity testing of supplementary cementitious materials

   https://doi.org/10.21809/rilemtechlett.2021.150  

   Suraneni, Prannoy (March 2021, RILEM Technical Letters)

   Identification and rapid characterization of novel supplementary cementitious materials (SCMs) is a critical need, driven by shortfalls in conventional SCMs. In this study, we present a discussion of recently developed reactivity tests – the R3 test, the modified R3 test, the lime strength test, and the bulk resistivity index test. These tests measure reactivity parameters such as heat release, bound water, calcium hydroxide consumption, strength, and bulk resistivity. All tests can screen inert from reactive materials. To additionally differentiate pozzolanic and latent hydraulic materials, two parameters, for example, calcium hydroxide consumption and heat release, are needed. The influences of SCM bulk chemistry, amorphous content, and fineness on measured reactivity are outlined. Reactivity test outputs can predict strength and durability of cement paste/mortar/concrete; however, caution must be exercised as these properties are influenced by a variety of other factors independent of reactivity. Thoughts are provided on using reactivity tests to screen materials for concrete durability. 

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3. Engineering of high specific strength and low thermal conductivity cementitious composites with hollow glass microspheres for high-temperature high-pressure applications

   https://doi.org/https://doi.org/10.1016/j.cemconcomp.2020.103514  

   Krakowiak, K. J. (April 2020, Cement concrete composites)

   Lightweight cement-based composites with high specific strength and low thermal conductivity are highly sought in the energy and construction industries. These characteristics are important in designing cement liners for high-temperature, high-pressure (HTHP) wells, in addition to those operating in permafrost. Similar attributes are also desirable in designing cementitious composites for energy efficient building envelopes. This work reports the results of an experimental campaign focused on engineering lightweight cementitious composites with hollow glass microspheres. It is demonstrated that the chemical stability of microspheres at HTHP conditions can be directly controlled by modulating the specific surface area and dissolution rate constant of supplementary siliceous additives. In addition to the stabilizing effect, such additives lead to the pore structure refinement and the enhancement of interfacial transition zone (ITZ). Introduced lightweight composites are capable of delivering significant load bearing capacity when normally cured, which is greatly increased by hydrothermal curing. Such high specific strength composites possess thermal conductivity below 0.3 W/mK at the oven dry density <1000 kg/m3 and cement dosage <400 kg/m3. This class of cementitious composites bears potential to enhance zonal insulation and well integrity, as well as increasing energy efficiency of building envelopes. 

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4. Effects of surfactant properties on pore wetting of membrane distillation

   https://doi.org/10.1016/j.memlet.2024.100077  

   Coolidge, Connor; Alhadidi, Azal_Mohammed Hassan; Wang, Wei; Tong, Tiezheng (December 2024, Journal of Membrane Science Letters)

   Pore wetting is a major constraint to the performance of membrane distillation (MD) for hypersaline brine treatment. Despite the existence of surfactants with diverse properties, an explicit relationship between the properties of surfactants and their capabilities of inducing pore wetting has yet to be established. In this study, we perform a comparative analysis of the wetting behaviors of various surfactants with different charges and molecular weights in MD desalination. The induction time of surfactants to initiate pore wetting was correlated to the apparent contact angle and surface tension of the feedwater. Our results show that different surfactants resulting in similar feedwater surface tensions can lead to drastically different wetting potential, suggesting that both charge of the head group and molecular weight of surfactants have a significant influence on membrane pore wetting. Further, we demonstrate that parameters that have been commonly used to indicate wetting potential, including apparent contact angle and solution surface tension, are not reliable in predicting the wetting behavior of MD membranes, which is intricately linked with surfactant properties such as charge and molecular size. We envision that our results not only improve our fundamental understanding of surfactant-induced wetting but also provide valuable insights that necessitate thorough consideration of surfactant properties in evaluating wetting potential and membrane wetting resistance for MD desalination. 

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5. Machine learning enables prompt prediction of hydration kinetics of multicomponent cementitious systems

   https://doi.org/10.1038/s41598-021-83582-6  

   Lapeyre, Jonathan; Han, Taihao; Wiles, Brooke; Ma, Hongyan; Huang, Jie; Sant, Gaurav; Kumar, Aditya (February 2021, Scientific Reports)

   Abstract Carbonaceous (e.g., limestone) and aluminosilicate (e.g., calcined clay) mineral additives are routinely used to partially replace ordinary portland cement in concrete to alleviate its energy impact and carbon footprint. These mineral additives—depending on their physicochemical characteristics—alter the hydration behavior of cement; which, in turn, affects the evolution of microstructure of concrete, as well as the development of its properties (e.g., compressive strength). Numerical, reaction-kinetics models—e.g., phase boundary nucleation-and-growth models; which are based partly on theoretically-derived kinetic mechanisms, and partly on assumptions—are unable to produce a priori prediction of hydration kinetics of cement; especially in multicomponent systems, wherein chemical interactions among cement, water, and mineral additives occur concurrently. This paper introduces a machine learning-based methodology to enable prompt and high-fidelity prediction of time-dependent hydration kinetics of cement, both in plain and multicomponent (e.g., binary; and ternary) systems, using the system’s physicochemical characteristics as inputs. Based on a database comprising hydration kinetics profiles of 235 unique systems—encompassing 7 synthetic cements and three mineral additives with disparate physicochemical attributes—a random forests (RF) model was rigorously trained to establish the underlying composition-reactivity correlations. This training was subsequently leveraged by the RF model: to predict time-dependent hydration kinetics of cement in new, multicomponent systems; and to formulate optimal mixture designs that satisfy user-imposed kinetics criteria. 

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