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The effect of nanoparticles and nucleation seeds on the hydration kinetics of alkali-activated materials is not well understood. Implications of nano-TiO2 (nTiO2) and C--S--H nucleation seeds (XSeed) on the early-age hydration and later-age properties of sodium hydroxide-activated ground granulated blast furnace slag were investigated. The effect of NaOH concentration (0.5, 1, 2, and 4 M) in the activator solution was reported. Results indicated the acceleration of early hydration kinetics with mixes of XSeed and nTiO2 when the concentration of the activator solution was 0.5/1 M. No considerable effects were noted with XSeed addition for 2/4 M, whereas there was an acceleration with the addition of nTiO2. These differences were attributed to the lack of dispersion of XSeed at higher activator concentrations. Hydrate phase assemblage did not change with the addition of nanoparticles by 28 days of hydration. Increase in strength, along with pore refinement, was observed with the incorporation of nanoparticles. [ABSTRACT FROM AUTHOR]

Background: Mental health issues are common among college students, and structured services have been proven to enhance outcomes. Despite increased enrolment for higher education in India, college mental health services remain sparse. JEEVANI is the first structured state-wide college mental health service in India. This paper describes its framework and provides an overview of its functioning during the initial five months. Methods: In 2019–2020, the Directorate of Collegiate Education, Government of Kerala, implemented the program in 66 colleges catering to approximately 60,000 students. Qualified counsellors were trained to identify issues and provide interventions and early referrals, using a stepped-care approach. They conducted awareness programs to promote mental health and reduce stigma. Results: The services were accessed by 2,315 students during the assessment period (October 2019 to February 2020). The beneficiaries were predominantly females (54.1%). Over a third (38.8%) belonged to the lower socio-economic strata, and 2.5% had significant vulnerabilities. Although no syndromal diagnoses were made, anxiety and depression were the most common presentations. The counsellors provided 3,758 individual sessions and facilitated support for students who reported academic difficulties or interpersonal issues. Severe mental illness was detected in 54 students, and referrals for specialist mental health input were initiated in 68. Conclusion: Describing the framework, sharing the technical material, and providing an overview of its functioning from a resource-constrained setting in India may encourage higher education institutions in low- and middle-income countries to consider similar projects. [ABSTRACT FROM AUTHOR]

Alite (Ca3SiO5: C3S*) and calcium aluminate (Ca3Al2O6: C3A) are the major phases in Portland cement, which have an essential role in the development of early age properties. The effects of gypsum content, fineness, and Na2SO4 addition on the early‐stage hydration kinetics are investigated for polyphase (co‐sintered) Ca3SiO5‐Ca3Al2O6 model systems using calorimetry, X‐ ray diffraction, thermal analysis, and solid‐state 27Al and 29Si nuclear magnetic resonance (NMR) spectroscopy. The results demonstrate that the hydration of C3A significantly affects the hydration of C3S. The C3S and C3A hydration is hindered considerably in severely over‐sulfated systems (where C3A hydration is suppressed due to a very high gypsum content) and systems with additional Na2SO4. Although there is a considerable amount of Al incorporation in the C‐S‐H phase, no clear trends with respect to gypsum content, hydration age or Na2SO4 addition are observed for the AlIV/Si ratios of the C‐S‐H phase determined from 29Si NMR. With the addition of Na2SO4, recrystallization of ettringite from the AFm phases is postponed from 1 day to 7 days. *Cement chemistry notation: C‐CaO, S‐SiO2, A‐Al2O3, S¯‐SO3, N‐Na2O. [ABSTRACT FROM AUTHOR]

Alite (Ca3SiO5: C3S*) and calcium aluminate (Ca3Al2O6: C3A) are the major phases in Portland cement, which have an essential role in the development of early age properties. The effects of gypsum content, fineness, and Na2SO4 addition on the early‐stage hydration kinetics are investigated for polyphase (co‐sintered) Ca3SiO5‐Ca3Al2O6 model systems using calorimetry, X‐ ray diffraction, thermal analysis, and solid‐state 27Al and 29Si nuclear magnetic resonance (NMR) spectroscopy. The results demonstrate that the hydration of C3A significantly affects the hydration of C3S. The C3S and C3A hydration is hindered considerably in severely over‐sulfated systems (where C3A hydration is suppressed due to a very high gypsum content) and systems with additional Na2SO4. Although there is a considerable amount of Al incorporation in the C‐S‐H phase, no clear trends with respect to gypsum content, hydration age or Na2SO4 addition are observed for the AlIV/Si ratios of the C‐S‐H phase determined from 29Si NMR. With the addition of Na2SO4, recrystallization of ettringite from the AFm phases is postponed from 1 day to 7 days. *Cement chemistry notation: C‐CaO, S‐SiO2, A‐Al2O3, S¯‐SO3, N‐Na2O. [ABSTRACT FROM AUTHOR]

Abstract: Effect of water to cement (w/c) ratio and temperature profiles on the densification of C–S–H (calcium silicate hydrate gel) and hydration kinetics of triclinic tricalcium silicate (C3S) is studied beyond the first day of hydration. Calorimetry and quantitative X‐ray diffraction/Rietveld analysis show that degree of hydration is unaffected by w/c up to 7 days and marginally thereafter. Coupling the degree of hydration with the portlandite content measured from thermal analysis indicate that C/S ratio of C–S–H decreases with increasing w/c. There is a clear increase in the portlandite content with increasing w/c, even though the degree of hydration is unchanged, due to the variations in C/S ratio of C–S–H. On the other hand, when C3S is initially cured at a lower temperature (20°C) and then at a higher temperature (40°C), there is a significant increase in the reactivity even until 28 days and vice versa. These experimental results were explained using the densified volumetric growth hypothesis, which assumes that hydration kinetics are dependent on the internal surface area of C–S–H. [ABSTRACT FROM AUTHOR]

Alite (impure C3S) being the major and most reactive phase in ordinary portland cement has been studied extensively. This paper focuses on the mathematical modeling of new hypothesis developed, densified volumetric growth, applied to the main hydration peak in alite hydration. This hypothesis assumes a time and particle size-dependent growth rate and densification rate of C-S-H controlled by its internal surface area. To test this hypothesis, a new microstructural modeling platform (Cementitious Reactions Simulator) has been developed. The model was used to calibrate and predict the isothermal calorimetric results from the literature and two sets of original experimental results with alite replaced with different replacement fractions of quartz, fly ash, and slag of different fineness. The model is able to capture and predict the effect of fineness and fillers without the need of varying the parameters for the particular set of simulations. The values of the parameters of simulation reflect the current experimental evidence from the literature and thus provide validation of the hypothesis which suggests that the main hydration period including deceleration period in the alite hydration is induced by the densification and reducing outer growth rate of C-S-H. [ABSTRACT FROM AUTHOR]