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This study identified castor oil and phosphate ester as effective retarders through setting time, tensile, and flexural tests, and determined their optimal dosages. The mechanism by which phosphate ester affects the setting time of polyurethane was further investigated using molecular dynamics simulations. Fourier transform infrared spectroscopy was also employed to systematically study the physical and chemical interactions between phosphate esters and polyurethane materials. The results demonstrate that a 1% concentration of phosphate ester provides the most effective retarding effect with minimal impact on the strength of polyurethane. When phosphate ester is added to the B component of the two-component polyurethane system, its interaction energy with component A decreases, as do the diffusion coefficient and aggregation degree of component B on the surface of component A. This reduction in interaction slows the setting time. Additionally, the addition of phosphate ester to polyurethane leads to the disappearance or weakening of functional groups, indicating competitive interactions within the phosphate ester components that inhibit the reaction rate. [ABSTRACT FROM AUTHOR]

Introduction: Mineral trioxide aggregate (MTA) is a calcium silicate-based cement that has changed conventional dental therapeutic approaches. This study aimed to evaluate physical, chemical and biological properties of novel AGM MTA, in comparison with MTA Angelus. Methods: The samples were prepared according to the manufacturer's instructions. The initial and final setting times were measured via a Gillmore needle following the ISO 6876:2012 standard. The radiopacity of the materials was evaluated against an aluminium step wedge on the basis of the ISO 6876 and 13,116 standards. The pH changes were measured at intervals of 3, 6, 24, 72, 96 and 144 h postimmersion in Hank's solution and calcium ion release was analysed after 168 h of immersion via inductively coupled plasma optical emission spectroscopy (ICP‒OES). Moreover, the cytotoxicity was assessed through the MTT assay on human dental pulp stem cells (hDPSCs) after 24 and 72 h of exposure to the set/fresh status of various dilutions of MTA extracts, following the ISO 10993-12 standard. Results: No significant difference was found between the initial setting times of the two materials (Angelus: 11.0 ± 1.0 min, AGM: 10.3 ± 1.5 min); however, MTA Angelus demonstrated a significantly shorter final setting time. Both materials met the minimum radiopacity requirements according to the ISO 6876 standard, with MTA Angelus exhibiting greater radiopacity than AGM MTA. Both materials created an alkaline environment without presenting any differences in each time point and AGM MTA released significantly greater amounts of calcium ions. In the cytotoxicity assessment, while the diluted extracts of both materials did not elicit any cytotoxic effects, the nondiluted samples, after 72 h of exposure, as well as the 30-min set AGM MTA after 24 h of exposure, were shown to be cytotoxic. Conclusions: In conclusion, MTA Angelus presented a faster setting time and lower cytotoxicity, while AGM MTA demonstrated greater calcium ion release. However, both materials presented clinically acceptable properties and AGM MTA could be a potential alternative to MTA Angelus. However, further clinical studies are required to confirm its application. [ABSTRACT FROM AUTHOR]

An investigation of the effect of gamma radiation was carried out on the setting time of alkali-activated binder paste. Mechanically activated coal fly ash (FA), ground granulated blast furnace slag (BFS), and their 1:1 mass mixture (MIX) were activated by water glass with a module of 1.5. Fresh paste was cast into molds and exposed to Co-60 gamma radiation, at a dose rate of 9.62–9.53 Gy/h, until the final setting. The initial and final setting times were determined by measuring the penetration of the Vicat needle at regular intervals. The initial setting times were 1 h 3 min for BFS, 1 h 55 min for MIX, and 3 h 28 min for FA. The final setting times were 1 h 10 min for BFS, 2 h 13 min for MIX, and 4 h 1 min for FA. The received doses were 8.02 Gy for BFS, 17.54 Gy for MIX, and 34.14 Gy for FA. Exposure to gamma radiation resulted in a shorter initial setting time for BFS, a shorter final setting time for FA, and results with an insufficiently visible impact on MIX. For dose rates in the 9–10 Gy/h range, the irradiation by Co-60 gamma rays during setting did not lead to flash, nor did it delay the setting of alkali-activated binder pastes. [ABSTRACT FROM AUTHOR]

The high acidity and low hydration activity of fluorgypsum restrict its application in the field of plastering gypsum. In order to solve this problem and promote the large-scale application of fluorgypsum in plastering gypsum, CaO and Ca(OH)2 were selected as neutralizer while Na2C2O4, Na2SO4, K2SO4, K2SiO3 and gypsum hemihydrate were selected as activator, to modify fluorgypsum. The effects of type and dosage of activator and neutralizer on modification effect were investigated. The results show that 3%(mass fraction) neutralizer can improve the pH value of fluorgypsum to around 9 and keep its free fluorine content around 0.02% (mass fraction). Considering the cost, the cheaper CaO is choose as neutralizer. In addition, K2SO4, Na2SO4 and gypsum hemihydrate as activator have good excitation effect, among which Na2SO4 has the best excitation effect. Plastering gypsum excited by 1.0% (mass fraction) Na2SO4 is prepared, with initial setting time of 119 min and final setting time of 252 min. Moreover, the compressive strength is 10.30 MPa while the flexural strength is 3.85 MPa. It should be noted that all indicators reach the requirements of "Plastering gypsum"(GB/T 28627-2023). [ABSTRACT FROM AUTHOR]

Copyright of New Building Materials / Xinxing Jianzhu Cailiao is the property of New Building Materials Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of New Building Materials / Xinxing Jianzhu Cailiao is the property of New Building Materials Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This research investigates the use of recycled diatomaceous earth (diatomite) from the wine, beer, and oil industries as supplementary cementitious materials in cement-based mixtures. This study aims to reduce embodied energy and promote circular economy practices by incorporating these industrial by-products. The research evaluates the compressive strength, durability, and pozzolanic activity of the mixtures over 7, 28, and 90 days of hydration. The results demonstrate that uncalcined diatoms from wine and oil showed lower compressive strength than natural diatomite, whereas calcination at 500 °C significantly improved performance. Beer diatoms exhibited the lowest mechanical strength because of the organic matter content in their composition. The incorporation of quicklime failed to induce pozzolanic activity in uncalcined diatoms; however, calcination at 500 °C led to improved long-term performance, highlighting the importance of heat treatment for activating diatoms' pozzolanic properties. This study concludes that recycled diatoms, particularly when calcined, have potential as sustainable cementitious materials. [ABSTRACT FROM AUTHOR]

Copyright of International Journal of Advances in Engineering & Pure Sciences is the property of Marmara University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Hot weather concreting has gained significant attention in recent years due to the increasing annual mean temperature. The accelerated hydration process under high temperature curing conditions can lead to premature hydration products, therefore, retarding admixtures are recommended to control the setting time. Various non-destructive methods were analyzed to estimate the setting time of cement-based materials. However, the evaluation of delayed cement hydration with added retarding admixtures has not been reported. This study aims to monitor the two non-destructive methods, electrical resistivity and ultrasonic pulse velocity, during the initial 24 h in cement pastes with added calcium lignosulfonate, the most common retarder. The setting time of cement pastes, cured at temperatures of 20, 30, and 40 ℃, was evaluated based on the rise time of these non-destructive measurements. Further, the effect of added retarder on the setting delay in cement paste was discussed and compared with the Vicat needle test. The results of X-ray diffraction and thermogravimetric analysis at the rising time of electrical resistivity revealed that the use of the retarding admixture induces delayed hydration reaction of C3S, C2S, and C3A, key hydration products influencing the setting delay. [ABSTRACT FROM AUTHOR]

Ambient–cured plain geopolymer binders typically exhibit unacceptably prolonged setting time values and weak development of mechanical properties. In this paper, a focussed literature review was done on setting time effects of physical – chemical factors comprising sodium hydroxide concentration, liquid – to – solids ratio, sodium silicate – to – sodium hydroxide ratio, and the influence of precursor composition. Subsequently, an experimental study was done wherein 0% to 30% ground granulated blast–furnace slag (GGBS) or ordinary Portland cement (OPC) were incorporated into fly ash – based geopolymer (FA - GPC) mixtures to compare effects of the two setting time modifiers. Paste and mortar mixtures were subjected to compressive strength, drying shrinkage, and pore – related physical properties tests.It was found that a strong correlation exists between setting time and lime content or Ca/Al ratio of the precursor. Indeed, the starting materials that had compositional values of 5% to 20% CaO and/or Ca/Al ratio of 0.5 to 1.5, were found to exhibit stable performance. Incorporation of 10% OPC gave initial /final setting time values of 65 /106 mins that met standard criteria specified in EN 197-1 (2011) and/or ASTM’s C150. It was also observed that incorporation of 10% OPC and 20% GGBS exhibited contrasting shrinkage effects, wherein the former decreased while the latter significantly increased drying shrinkage to exceed the 0.10% maximum limit stipulated in ASTM C596.

This is an article in the field of mineral materials. The preparation of α-hemihydrate gypsum from phosphogypsum instead of natural gypsum is an important way of its high value-added utilization. However, soluble fluorine impurities in phosphogypsum will have adverse effects on α-hemihydrate gypsum. In this article, the effect of soluble fluorine on the setting time and the strength of the hardened body of α-hemihydrate gypsum was studied, and its mechanism was explored by XRD, SEM-EDS and XPS. The results show that soluble fluorine can shorten the setting time and decrease the mechanical strength of α-hemihydrate gypsum. The microstructure analysis of hardened body shows that soluble fluorine can coarsen the particles of gypsum dihydrate, increase the internal pores, and reduce the mechanical strength. XRD and XPS analysis show that soluble fluorine reacts with Ca2+ generated by the dissolution of α-hemihydrate gypsum to form calcium fluoride with smaller solubility product, thus shortening the setting time of α-hemihydrate gypsum.