This paper presents the results of the optimisation and characterization of Miscanthus fibre reinforced geopolymer foams based on fly ash and represents an important step forward in the development of a sustainable and environmentally friendly insulation material. Miscanthus belongs to a promising group of renewable raw materials with favourable thermal insulation properties. Design of experiment (DoE) were used to optimize the thermal conductivity and compressive strength of Miscanthus x giganteus reinforced geopolymer foams. In addition, the samples was analyzed using X-ray diffraction (XRD), Field emission scanning electron microscopy (SEM) and Fourier-Transform Infrared Spectroscopy (FTIR). Mixtures with a low thermal conductivity of 0.056 W (m K)-1 and a porosity of 79 vol% achieved a compressive strength of only 0.02 MPa. In comparison, mixtures with a thermal conductivity of 0.087 W (m K)-1 and a porosity of 58 vol% achieved a compressive strength of 0.45 MPa. Based on the determined parameters especially due to the low compressive strength, an application as cavity insulation or insulation between rafters is possible.

BACKGROUND: This study aims to evaluate the compressive strength, solubility, radiopacity, and flow of Bromelain (BR)-modified Biodentine (BD) for direct pulp capping (DPC). This is suggested to determine the impact of BR on the physical properties of BD.
METHODS: Eighty samples were prepared according to the ISO and ADA specifications and evaluated for compressive strength, solubility, radiopacity, and flow. The compressive strength was evaluated at 24 h and 21 days via a universal testing machine. The solubility was determined by weight loss after 24-hours immersion in deionized water. Radiopacity was assessed via X-ray with aluminum step-wedges, and flow was measured by the diameter of the discs under a standard weight. Independent sample t-tests were used to statistically assess the data. A significance level of 5% was considered.
RESULTS: The compressive strength was 41.08 ± 1.84 MPa for BD and 40.92 ± 1.80 MPa for BR + BD after 24 h, and 88.93 ± 3.39 MPa for BD and 87.92 ± 3.76 MPa for BR + BD after 21 days, with no significant differences. Solubility was slightly greater in the BR + BD (2.75 ± 0.10%) compared to BD (2.62 ± 0.25%), but not significantly different. The radiopacity was similar between BD (2.82 ± 0.11 mm) and BR + BD (2.73 ± 0.10 mm). BR + BD resulted in significantly greater flow (9.99 ± 0.18 mm) than did BD (9.65 ± 0.27 mm) (p ≤ 0.05).
CONCLUSIONS: BR-modified BD maintains BD\'s physical properties, with improved flow, making it a promising DPC agent that warrants further study.

This study presents a novel biotechnological approach for creating water vapor-resistant cryogels with improved integrity. Rice straw cellulose was transformed into nanofibrils through TEMPO-mediated oxidation and high-pressure homogenization. The resulting cryogels remained firm even when immersed in aqueous media, whose pores were used by live cell to deposit polyhydroxyalkanoate (PHA) particles inside them. This novel method allowed the compatibilization of PHA within the cellulosic fibers. As a consequence, the water sorption capacity was decreased by up to 6 times having just 4 % of PHA compared to untreated cryogels, preserving the cryogel density and elasticity. Additionally, this technique can be adapted to various bacterial strains and PHA types, allowing for further optimization. It was demonstrated that the amount and type of PHA (medium chain length and small chain length-PHA) used affects the properties for the cryogels, especially the water vapor sorption behavior and the compressive strength. Compared to traditional coating methods, this cell-mediated approach not only allows to distribute PHA on the surface of the cryogel, but also ensures polymer penetration throughout the cryogel due to bacterial self-movement. This study opens doors for creating cryogels with tunable water vapor sorption and other additional functionalities through the use of specialized PHA variants.

Precisely forecasting how concrete reinforced with fiber-reinforced polymers (FRP) responds under compression is essential for fine-tuning structural designs, ensuring constructions fulfill safety criteria, avoiding overdesigning, and consequently minimizing material expenses and environmental impact. Therefore, this study explores the viability of gradient boosting regression tree (GBRT), random forest (RF), artificial neural network-multilayer perceptron (ANNMLP) and artificial neural network-radial basis function (ANNRBF) in predicting the compressive behavior of fiber-reinforced polymer (FRP)-confined concrete at ultimate. The accuracy of the proposed machine learning approaches was evaluated by comparing them with several empirical models concerning three different measures, including root mean square errors (RMSE), mean absolute errors (MAE), and determination coefficient (R2). In this study, the evaluations were conducted using a substantial collection of axial compression test data involving 765 circular specimens of FRP-confined concrete assembled from published sources. The results indicate that the proposed GBRT algorithm considerably enhances the performance of machine learning models and empirical approaches for predicting strength ratio of confinement (f\'cc/f\'co) by an average improvement in RMSE as 17.3%, 0.65%, 66.81%, 46.12%, 46.31%, 46.87% and 69.94% compared to RF, ANNMLP, ANNRBF, and four applied empirical models, respectively. It is also found that the proposed ANNMLP algorithm exhibits notable superiority compared to other models in terms of reducing RMSE values as 9.67%, 11.29%, 75.11%, 68.83%, 73.64%, 69.49% and 83.74% compared to GBRT, RF, ANNRBF and four applied empirical models for predicting strain ratio of confinement (εcc/εco), respectively. The superior performance of the GBRT and ANNMLP compared to other methods in predicting the strength and strain ratio confinements is important in evaluating structural integrity, guaranteeing secure functionality, and streamlining engineering plans for effective utilization of FRP confinement in building projects.

The dataset presented here emanates from preliminary studies that compared the early-age compressive strengths of geopolymer mortars produced from construction and demolition wastes (CDW) commonly found in Qatar using different alkaline activators. Waste concrete, waste bricks and steel slag were used as aluminosilicate sources for the geopolymer mortars. Waste concrete was used as fine aggregate (75 µm to 4 mm), while solid or hollow red clay bricks were used together with steel slag as aluminosilicate powders. Solid red clay brick (75 µm to 1.4 mm) was also considered as fine aggregate. Different alkaline activators including solid powder or ground pellet forms of Ca(OH)2, CaO, and Ca(OH)2-NaOH, NaOH-CaCO3 and Na2SiO3-Na2CO3-Ca(OH)2 mixtures were employed by just adding water. Both solid powder Ca(OH)2 and viscous solutions of NaOH and NaOH-Na2SiO3 were also considered as alkaline activators. The geopolymer mortars included small amounts of some other additives such as gypsum, microsilica and aluminium sulfate to enhance the geopolymerization and hydration process. Random proportions of the materials were employed in the range-finding experiments, and the mortars produced were tested for compressive strength. The dataset shows the 7-day compressive strengths and densities of the 40 mixtures tested with mostly ambient temperature (20°C) curing. It also shows such data for mixtures in which variables such as curing at 40°C, mixing with hot water at 50 - 60°C temperature, grading of waste concrete aggregates, and collective grinding of the powdered materials were considered. The data indicates possible early-age compressive strengths of different geopolymer mortar mixture designs and the materials and mixture design methods that can be used to achieve desired early-age strengths from waste concrete and bricks.

This study examines the corrosion characteristics of weakly cemented sandstone under alkaline conditions, evaluating the effects of varying pH levels on its macroscopic degradation, micro-porosity, and mechanical properties, notably uniaxial compressive strength. Findings reveal that heightened alkalinity exacerbates rock damage, although a temporary alleviation in mass loss occurs between pH 9 and 11 due to pore clogging by complexes formed from cations like Ca2+ and Mg2+.Increased alkalinity induces marked changes in pore features, with an observed rise in pore numbers, transformation of pore shapes from elongated to more spherical, and adjustments in porosity, pore size, and roundness. Furthermore, the study confirms a decline in both the rock\'s compressive strength and elastic modulus as pH rises. These revelations shed light on the role of pH in the corrosion behavior of weakly cemented sandstone under alkaline conditions, providing a fresh perspective for understanding its corrosion mechanisms in such environments.

Doping of brushite cements with metal ions can entail many positive effects on biological and physicochemical properties. Cu2+ ions are known to exhibit antibacterial properties and can additionally have different positive effects on cells as trace elements, whereas high Cu2+ concentrations are cytotoxic. For therapeutical applications of bone cement, a combination of good biocompatibility and sufficient mechanical properties is required. Therefore, the aim of this study was to investigate different physicochemical and biological aspects, relevant for application, of a brushite cement with Cu2+-doped β-tricalcium phosphate, monocalcium phosphate monohydrate and phytic acid as setting retarder. Additionally, the ion release was compared with a cement with citric acid as setting retarder. The investigated cements showed good injectability coefficients, as well as compressive strength values sufficient for application. Furthermore, no antibacterial effects were detected irrespective of the Cu2+ concentration or the bacterial strain. The cell experiments with eluate samples showed that the viability of MC3T3-E1 cells tended to decrease with increasing Cu2+ concentration in the cement. It is suggested that these biological responses are caused by the difference in the Cu2+ release from the hardened cement depending on the solvent medium. Furthermore, the cements showed a steady release of Cu2+ ions to a lesser extent in comparison with a cement with citric acid as setting retarder, where a burst release of Cu2+ was observed. In conclusion, despite the anticipated antibacterial effect of Cu2+-doped cements was lacking and mammalian cell viability was slightly affected, Cu2+-concentrations maintained the physicochemical properties as well as the compressive strength of cements and the slow ion release from cements produced with phytic acid is considered advantageous compared to citric acid-based formulations.

Coal fly ash (CFA) is an essential raw material in brickmaking industry worldwide. There are some coal mines with a relatively high content of uranium (U) in the Xinjiang region of China that are yet understudied. The CFA from these coal mines poses substantial environmental risks due to the concentrated uranium amount after coal burning. In this paper, we demonstrated a calcifying ureolytic bacterium Halomonas sp. SBC20 for its biocementation of U in CFA based on microbially induced calcite precipitation (MICP). Rectangle-shaped CFA bricks were made from CFA using bacterial cells, and an electric testing machine tested their compressive strength. U distribution pattern and immobility against rainfall runoff were carefully examined by a five-stage U sequential extraction method and a leaching column test. The microstructural changes in CFA bricks were characterized by FTIR and SEM-EDS methods. The results showed that the compressive strength of CFA bricks after being cultivated by bacterial cells increased considerably compared to control specimens. U mobility was significantly decreased in the exchangeable fraction, while the U content was markedly increased in the carbonate-bound fraction after biocementation. Much less U was released in the leaching column test after the treatment with bacterial cells. The FTIR and SEM-EDX methods confirmed the formation of carbonate precipitates and the incorporation of U into the calcite surfaces, obstructing the release of U into the surrounding environments. The technology provides an effective and economical treatment of U-contaminated CFA, which comes from coal mines with high uranium content in the Xinjiang region, even globally.

UNASSIGNED: Geopolymers are alternative materials to cement because they require less energy in their production process; hence, they contribute to the reduction in CO 2 emissions. This study aims to evaluate the possibility of using industrial residues such as silica fume (SF) to improve the physical and mechanical properties of a pumice stone (PS)-based geopolymer.
UNASSIGNED: Through an experimental methodology, the process starts with the extraction, grinding, and sieving of the raw material to carry out the physical and chemical characterization of the resulting material, followed by the dosage of the geopolymer mixture considering the factors that influence the resistance mechanical strength. Finally, the physical and mechanical properties of the geopolymer were characterized. This research was carried out in four stages: characterization of the pumice stone, design of the geopolymer through laboratory tests, application according to the dosage of the concrete, and analysis of the data through a multi-criteria analysis.
UNASSIGNED: It was determined that the optimal percentage of SF replacement is 10%, which to improves the properties of the geopolymer allowing to reach a maximum resistance to compression and flexion of 14.10 MPa and 4.78 MPa respectively, showing that there is a direct relationship between the percentage of SF and the resistance.
UNASSIGNED: Geopolymer preparation involves the use of PS powder with a composition rich in silicon and aluminum. The factors influencing strength include the ratio of sodium silicate to sodium hydroxide, water content, temperature, curing time, molarity of sodium hydroxide, and binder ratio. The results showed an increase in the compression and flexural strength with 10% SF replacement. The geopolymer\'s maximum compressive strength indicates its non-structural use, but it can be improved by reducing the PS powder size.

This study aimed to evaluate the effect of incorporating nanocrystalline cellulose (NCC) sourced from rice husk on the mechanical properties of a commercial glass ionomer cement (GIC). NCC was isolated through acid hydrolysis, and its crystallinity, chemical structure, and morphology were characterized through x-ray diffractometry, Fourier-transform infrared spectroscopy, and transmission electron microscopy, respectively. Various concentrations of NCC (0%, 0.5%, 1%, and 1.5%) were added to reinforce the GIC matrix. Mechanical tests including compressive strength, flexural strength, hardness, and shear bond strength were conducted on the modified GIC samples. The addition of NCC resulted in increased hardness and shear bond strength values, with 1% NCC showing the highest values compared to other concentrations. However, there was no significant improvement observed in the compressive and flexural strength of the modified GIC. Failure mode test revealed a reduction in adhesive failure with the addition of NCC. Incorporating small amounts of NCC (0.5%-1%) suggests a promising and affordable modification of GIC restorative material using biomass residue, resulting in improved mechanical properties.