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Alkali-activated slag grouting materials exhibited excellent mechanical properties but still faced technical challenges such as insufficient fluidity and overly rapid setting. To enhance their workability, this study introduced fly ash as a modifying component, leveraging its morphological and activity effects to systematically investigate the composite influence on fluidity, setting time, and compressive strength. The mechanism was further elucidated through microstructural analysis of the mineral crystallization characteristics of polycondensation products. The results indicated that with increasing fly ash content, the fluidity of the grouting material continuously improved, and both the initial and final setting times were significantly prolonged, albeit at the expense of a gradual decline in compressive strength. At a 20% fly ash content, the fluidity spread increased to 292 mm, the initial and final setting times were extended to 70 min and 103 min, respectively, while the 1 d and 28 d compressive strengths reached 11.8 MPa and 48.1 MPa, achieving an optimal overall performance that met practical grouting requirements. Microscopic analysis revealed that fly ash enhanced the rheological properties and delayed the setting process through the “ball-bearing effect” and its low early-age reactivity. However, as the fly ash content rose, the active calcium content in the system continuously decreased, inhibiting the formation and development of key mineral crystals such as calcium silicate and calcium aluminosilicate, thereby leading to the reduction in compressive strength.

Admixtures are an integral part of modern cementitious materials, as they significantly enhance the rheological, mechanical, and durability properties of the material. Though manufactured admixtures are mainly used in concrete production, they are expensive. Therefore, this research investigated the effect of sugarcane juice (SCJ), as a natural admixture, on the properties of concrete. Various percentages of SCJs were used to investigate the initial and final setting time, workability, compressive strength, and splitting tensile strength of concrete. Furthermore, the effect of different cement-sand ratios (c/s) and water-cement ratios (w/c) on the setting time of different cement mortar mixes was studied. Experimental results have shown that the setting time measured by the Vicat’s apparatus reduces significantly, up to a certain percentage of SCJ in the mortar mixes. Setting time is also reduced as the c/s and w/c ratios are reduced in the mortar mix. From the results, it was found that, based on the c/s ratio, with the addition of 20% SCJ in the mix, the initial setting time of mortar can be reduced to 10% from 79%. In the case of mechanical strength, compared to the control mix (0% SCJ), more than 29% higher compressive strength in concrete was achieved by adding 10% SCJ to the mix. For the splitting strength, this increment was more than 4%. The ANOVA analysis also proved that the higher percentages of SCJ produced a compressive strength that was not statistically different from the control concrete mix. Finally, the research outcome showed that the dosages of SCJ can greatly alter the setting time and mechanical strength of cementitious materials.

Alkali-activated fly ash/GGBS concrete (AAFGC) is a new blended concrete that has been studied by many researchers due to its environmental advantages and better technological characteristics. However, the effect of various factors on AAFGC fresh and hardened properties has not yet been thoroughly studied. The literature mainly describes the combination of NaOH and Na2SiO3 as an activator for the AAFGC’s activation, but alkali-activated GGBS concrete (AAGC) prepared with this activator solution is less workable due to its rapid setting behaviour. In this study, AAFGC was prepared using neutral grade liquid Na2SiO3 with a SiO2/Na2O ratio of 2.92. An experimental program was performed for fly ash-GGBS combinations (100-0, 50-50, 0-100), solution/binder ratios (0.6, 0.65, 0.7) and binder contents (300, 400 and 500 kg/m3) to evaluate the workability and the compressive and tensile strength of AAFGC. The results of this study show that a water glass of 2.92 silica modulus used as an activator to prepare AAFGC under ambient curing is very useful in the construction industry.

Approximately 2.78 Mt of coal fly ash is produced in the Philippines, with a low utilization rate. Using fly ash-based geopolymer for construction will lessen the load sent to landfills and will result in lower GHG emissions compared to OPC. It is necessary to characterize the fly ash and optimize the geopolymer components to determine if it can replace OPC for in situ applications. The activator-to-precursor ratio, the water-to-solids ratio, and the sodium hydroxide-to-sodium silicate ratio were optimized using a randomized I-optimal design from the experimental results of 21 runs with five replicates, for a total of 105 specimens of 50 mm × 50 mm × 50 mm paste cubes. The engineering properties chosen as the optimization responses were the unconfined compressive strength (UCS), the initial setting time, and the final setting time. The samples were also ambient-cured with the outdoor temperature ranging from 30 °C to 35 °C and relative humidity of 50% ± 10% to simulate the on-site environment. Runs with high unconfined compressive strength (UCS) and short setting times were observed to have a low water-to-solids (W/S) ratio. All runs with a UCS greater than 20 MPa had a W/S ratio of 0.2, and the runs with the lowest UCS had a W/S of 0.4. The initial setting time for design mixes with a W/S ratio of 0.2 ranged from 8 to 105 min. Meanwhile, five out of seven design mixes with a W/S ratio of 0.4 took longer than 1440 min to set. Specimens with an alkali activator ratio (NaOH/WG) of 0.5 (1:2) and 0.4 (1:2.5) also had significantly lower setting times than those with an alkali activator ratio of 1. The RSM model was verified through confirmatory tests. The results of the confirmatory tests are agreeable, with deviations from the expected UCS ranging from 0 to 38.12%. The generated model is a reliable reference to estimate the UCS and setting time of low-calcium FA geopolymer paste for in situ applications.

This paper presents the research method of hardening process of gypsum binders and composites, based on them, using the ultrasonic method. Modern construction composites, based on higher water resistance gupsym, contain the coarse aggregate particles, giving them heat and sound insulating properties. One of the frequent purposes, designing such composites, is the slowdown of the processes of setting, so it allows the builders to work with the material for a sufficiently long period. The use of standard control penetration methods of the setting processes for the considered composites becomes difficult because of the presence of course particles in the binder paste. The ultrasonic method is proposed to use alternatively to study the process of setting. For its implementation, the technique has been developed, based on the use of ultrasound systems for quality control of concrete products. The transit time of ultrasonic signals through the layer of hardening binder paste with the fixed thickness was measured in a regular intervals until completely setting. On the basis of the obtained data, the ultrasound velocity was calculated and the setting time was determined. For this purpose, a differential curve of the time of ultrasound transmission was plotted, and the period was considered, at which the transition to the steady-state condition was carried out, it is equivalent to the end of the setting. The initial setting was determined by the first trip of the measuring equipment, corresponding moment of the formation of the primary crystal structure of the composite, which has sound-transmission properties. To verify the values of the setting time, the simultaneous measurement of the plastic strength of the model system was used. The moments of the beginning and the end of the setting, as well as the ultrasound velocities which were typical for these moments, were determined with the plastic strength. The obtained velocity values allowed to find the setting times of other composites. The actual setting time is estimated based on the values, obtained by all the available methods. The model, based on percolation theory, has been proposed for analyzing the physicochemical phenomena during the setting.

Background. Dental plaster, white orthodontic gypsum, and construction gypsum have β-hemihydrate particles. Setting time is an essential property of dental gypsum, which can affect the strength of the material. This research aimed to compare construction gypsum, dental plaster, and white orthodontic gypsum’s initial and final setting times. Methods. Three groups were included in this experimental laboratory study: construction gypsum (A), dental plaster (B), and white orthodontic gypsum (C). Each group consisted of 10 samples. Gypsum manipulation consisted of using 120 gr of powder and 60 mL of water. Gypsum powder and water were mixed using a gypsum mixer at 120 rpm. A homogeneous mixture was poured into a mold, and the setting time was measured using a Gillmore needle, according to ASTM C266-03. The initial setting time test was measured using 113.4 grams and a 2.12-mm needle. The final setting time was measured using 453.6 grams and a 1.06-mm needle. This test was repeated until the needle failed to penetrate the gypsum’s surface. All the data were analyzed with one-way ANOVA and post hoc Tukey tests using SPSS 23. Results. The average initial setting time for groups A, B, and C were 10.39±1.19, 16.17±1.40, and 24.46±1.51, respectively. The average final setting time for groups A, B, and C were 15.97±0.79, 24.31±0.88) and 33.37±0.66, respectively. One-way ANOVA and post hoc Tukey tests showed significant differences in the initial and final setting times between the three groups (P<0.05). Conclusion. There were differences in setting time between dental plaster, white orthodontic gypsum, and construction gypsum. The construction gypsum’s setting time is suitable as a type II dental gypsum, according to ADA No.25.

Calcium fluoroaluminosilicate glasses (CAS) are used in the formulation of glass ionomer cements for dental applications. However, the cements obtained from CAS glasses were found to be radiolucent. In this study, the influence of substituting Zn, Sr and Mg for Ca of CAS glasses was investigated with respect to the structure and setting characteristics, mechanical properties, and radiopacity of cements designed for luting applications. Three glass compositions based on substitution of Zn, Sr and Mg for Ca at 1:1 molar ratio was synthesized. They were coded as the G 021 (Ca: Zn), G 022 (Ca: Sr), G 023 (Ca: Mg). G 021 and G 022 glasses were processed by conventional melt quench route, whereas G 023 was processed by microwave melt–quench route. Each glass was then mixed with Fuji Type I GIC liquid in order to evaluate the properties of novel cements at different powder/liquid ratios. X-ray diffraction and Fourier Transform-Infrared spectroscopy analysis confirmed the structure of the processed glasses. The average particle size of the processed glass powders was within specification limits for luting applications (<15 μm). The substitution of Zn, Sr and Mg for Ca at 1:1 molar ratio increased the reactivity of the respective glasses. This has been reflected in their respective setting characteristics and mechanical properties. The optimal combination of setting time, strength and radiopacity for the cements examined here was shown by G 022 cements. The microwave melting can be utilized for processing ionomer glasses as it did not alter the structure and properties of G 023 cement.