Silicate Concentrations Research Articles

Citrus bliss: potassium, sodium, and calcium silicates secrets for post-harvest diseases of fruit defense

Biotic stress significantly challenges the global citrus industry. Major post-harvest issues include diseases caused by Penicillium digitatum, Penicillium italicum, Geotrichum citri-aurantii, Alternaria alternata, and Phytophthora citrophthora. The negative impact of chemical fungicides on the environment and health necessitates eco-friendly alternatives. This study examines the effectiveness of sodium, potassium, and calcium silicates against common citrus diseases. In vitro tests evaluated mycelial growth inhibition using silicate concentrations from 0 to 10,000 ppm after 7 days at 25°C. Sodium silicate showed the highest efficacy, completely inhibiting P. digitatum and P. italicum at 2000 ppm. Potassium and calcium silicates achieved 100% inhibition against Penicillium spp. at a concentration of 1%. In vivo tests on Sidi Aissa clementines assessed the preventive and curative effects of 1, 2, and 6% silicate salt solutions. Sodium silicate prevented 41% of brown rot, 72% of sour rot, and 100% of green mold at 6%. Calcium silicate at 6% significantly reduced blue mold and black rot by 32% and 74%, respectively. Sodium silicate was most effective in curative treatments, suggesting its potential as a pre- or post-harvest spray to control P. digitatum, P. italicum, and G. citri-aurantii.

Pre-treated municipal solid waste bottom ash as alkali-activated mortar precursor

Pre-treated incinerator bottom ash was used as a precursor of alkali-activated mortars. Control mortars were produced using coal fly ash. Different combinations of alkaline activator were tested (sodium oxide/binder ratio (4%, 6%, 8%, 10% and 15%) and silicon dioxide/sodium oxide ratio (0, 0.5, 1.0, 1.5 and 2.0)) and the influence of these on the mortar's mechanical performance was evaluated. The mortars were tested in both fresh (for density and workability) and hardened states (for dry density, compressive and flexural strengths and modulus of elasticity) after 7, 28, 91 and 182 days. The first stage of work was precursor pre-treatment in a sodium hydroxide solution to prevent the expansion of fresh specimens due to the reaction of aluminium with the alkaline activator. The pre-treatment was effective in preventing excessive hydrogen gas generation during setting, leading to dimensional stability and improved strength. Different optimum sodium oxide contents were observed after 28 days (i.e. 15% for fly ash specimens and 8% for bottom ash specimens). The results of a simplified life-cycle assessment showed that such mixes exhibited lower overall carbon dioxide emissions when compared with cement-based counterparts. However, this trend was reversed with increasing contents of sodium hydroxide and sodium silicate.

A Global Ocean Opal Ballasting–Silicate Relationship

AbstractOpal and calcium carbonate are thought to regulate the biological pump's transfer of organic carbon to the deep ocean. A global sediment trap database exhibits large regional variations in the organic carbon flux associated with opal flux. These variations are well‐explained by upper ocean silicate concentrations, with high opal ‘ballasting’ in the silicate‐deplete tropical Atlantic Ocean, and low ballasting in the silicate‐rich Southern Ocean. A plausible, testable hypothesis is that opal ballasting varies because diatoms grow thicker frustules where silicate concentrations are higher, carrying less organic carbon per unit opal. The observed pattern does not fully emerge in an advanced ocean biogeochemical model when diatom silicification is represented using a single global parameterization as a function of silicate and iron. Our results suggest a need for improving understanding of currently modeled processes and/or considering additional parameterizations to capture the links between elemental cycles and future biological pump changes.

Effects of the Sedimentary Environment on Organic-Rich Shale in the Intracratonic Sag of the Sichuan Basin, China

The enrichment of organic matter in high-quality marine shale is generally controlled by factors such as the redox conditions of sedimentary environments, productivity levels, terrigenous input, and ancient productivity. However, the controlling effect of the sedimentary environment on organic matter enrichment in intracratonic sag is still unclear. This study takes samples from the Qiongzhusi formation shale in southern Sichuan Basin as the research object, focusing on trace elements as well as rare earth elements in different stratigraphic intervals. The provenance of the Qiongzhusi formation shale is mainly terrigenous, with sediment sources mainly consisting of sedimentary rocks and granites. The primary sedimentary environment transitions from a continental margin setting, influenced by rift-related tectonic activity and sediment influx from adjacent landmasses, to an open oceanic environment characterized by mid-ocean ridge processes and oceanic plate subduction zones. During sedimentation, saline water was present, with predominant sedimentary environments ranging from shallow water to deep water continental shelves. The shale in the study area is characterized by a higher content of silicates and a lower content of carbonate minerals. Its siliceous sources are mainly influenced by biogenic and terrigenous debris, indicating higher ancient primary productivity and representing a favorable target for shale gas exploration.

Preparation of solid alkali activator for geopolymer synthesis using vanadium-bearing shale tailing

The vanadium-bearing shale tailing (VST) with large reserves pollutes the environment and urgently needs to be utilized as a resource. Due to its main component being silica, VST has great potential as a raw material for geopolymer. Therefore, this study uses VST to prepare the solid alkali activator (SAA) by thermochemical methods. Analysis show that the temperature and NaOH dosage of thermochemical reaction significantly affect the alkaline activation effect of SAA. Temperature affects the silicate content and the amount of NaOH affects the soluble silicate content in SAA. When the reaction temperature is high (such as above 900 ℃) and the amount of sodium hydroxide is low (such as the mass ratio of sodium hydroxide to VST is 0.6), quartz almost transforms into silicates, but the silicates have a stable cyclic chemical structure and are difficult to dissolve during the geopolymerization reaction. When the reaction temperature is low (such as less than 700 ℃) and the amount of sodium hydroxide is high (such as the mass ratio of sodium hydroxide to VST is 0.9), quartz in VST is difficult to fully convert into silicates, there are unreacted quartz and sodium hydroxide in SAA, and SAA has poor alkaline activation performance. The optimal synthesis process conditions for SAA are as follows: synthesis temperature is 900 °C and the mass ratio of sodium hydroxide to VST is 0.95. The main silicate components of SAA are Na2SiO3 and Na15.6Ca3.8Si12O36. During the synthesis of one-part geopolymer (OPG), Na2SiO3 dissolution generates a strong alkaline reaction environment and provides active silicon-oxygen tetrahedron monomers or oligomers, Na15.6Ca3.8Si12O36 is bonded with geopolymer gel structure by stable cyclic silicate structure, which makes OPG have a compact integrated structure. When the mass ratio of SAA to MK is 1:1.3, the 7-day compressive strength of the prepared OPG is about 49 MPa, SAA has the potential as a substitute for commercial sodium silicate to prepare geopolymers.

Influence of Steel Slag as a Partial Replacement of Aggregate on Performance of Reinforced Concrete Beam

Amidst the global pursuit of sustainable alternatives in concrete production, this study explores the viability of incorporating by-products or waste materials as aggregates to support the concrete construction industry, with a specific emphasis on steel slag. The objective of this study is to evaluate the effectiveness of steel slag as a partial replacement for fine and coarse aggregates in concrete production. The experiment involved casting 30 cubes and 10 beams, replacing fine aggregate from 0 to 60%. Flexural and compressive strength tests at 7 and 28 days followed the ACI method. Results revealed that a 30% replacement of fine aggregate with steel slag led to higher compressive strength at both 7 and 28 days, while a 45% replacement showed superior flexural strength at 28 days. Further chemical analysis and optimization are recommended for deeper insights. The study concludes with marginal improvements in compressive and flexural strength with steel slag partial replacement, identifying 30% for fine aggregate and 45% for coarse aggregate as optimal replacements. In addition, the mineral composition of steel slag exhibits significant variability, with compounds, including silicon dioxide (SiO2), iron oxide (Fe2O3), manganese oxide (MnO), aluminum oxide (Al2O3), and calcium oxide (CaO). Chemical analysis indicates high silicate content and minimal alkali content, contributing to enhanced strength during concreting. Higher steel slag replacement reduces workability, confirmed by slump tests. However, all mixes maintain a true slump, and unit weight increases with steel slag aggregate replacement. Compressive strength improves incrementally with higher steel slag content, echoing prior research. In addition, flexural strength rises with steel slag replacing both coarse and fine aggregates, suggesting enhanced performance in reinforced concrete structures. These findings highlight steel slag’s potential as a sustainable alternative in concrete production, aiming to advance its application in the construction industry, promoting environmental sustainability and economic viability.

Study of nanosilica coated and polyaniline grafted cotton fabric

Valuable biomass product nanosilica obtained from rice husk has been hybridized with polyaniline through grafting and was used as coating material over cotton fabric using 3-aminopropyltriethoxysilane as crosslinking agent. In order to optimize the coating percentages of nanosilica and polyaniline, different weight concentration of both sodium silicate and aniline were used to develop the nanosilica coated and polyaniline grafted cotton fabric. The resulting cotton fabrics were studied for their UV shielding property, thermal and basic fabric properties. Cotton fabric coated with 50% of aniline and 0.75% of silica (S0.75A50C) affords the highest Ultraviolet Protection Factor (UPF) as 46.2. The result shows that the nanosilica coated and polyaniline grafted cotton fabric possess higher UV shielding when compared with that of neat cotton fabric.

Improving the scour-resistance performance of for offshore wind turbines: Experimental and computational fluid dynamics studies on macro and micro characteristics

To enhance the resistance to local scour around offshore wind turbine monopiles, 15 mixtures were designed based on Response Surface Methodology (RSM). Cement content, sodium silicate content, and rubber powder content were selected as independent variables. After determining their flowability, the compressive strength and shear strength were measured after curing in pure water and artificial seawater for 3 days, 7 days, 14 days, and 28 days. Experimental results indicate significant improvement in the mechanical properties of the modified soil, including increased Unconfined Compressive Strength (UCS), internal friction angle, and cohesion. The optimal mix ratio is identified as CSR40–10–15, consisting of 40 % cement, 10 % sodium silicate, and 15 % rubber powder. The strength variation mechanism is elucidated from both macroscopic and microscopic perspectives. Finally, numerical simulations using Computational Fluid Dynamics (CFD) software validate the scour resistance performance based on the optimal mix ratio of flowable solidified soil, offering a new approach for local scour protection around offshore wind turbine monopile.

Mechanical and microstructural characterization of one-part binder incorporated with alkali-thermal activated red mud

The traditional production of silicate cement is associated with substantial carbon emissions and environmental degradation. In contrast, cementless alkali-activated binders, derived from solid waste and industrial byproducts, have garnered significant interest for their reduced material costs, energy efficiency, and environmental benefits. This research investigates the application potential of an advanced mixture of anhydrous sodium silicate and red mud in one-part alkali-activated binders. It is assessed through various analytical techniques, including compressive strength, X-ray diffraction, fourier transform infrared, thermogravimetric analysis, digital image correlation, and scanning electron microscopy with energy dispersive spectroscopy. Findings demonstrate that the synergy between red mud and anhydrous sodium silicate markedly enhances the early strength of one-part alkali-activated binders incorporated with alkali-thermal activation. The increment in sodium silicate content is pivotal for bolstering binder performance. A 40 % red mud admixture results in a compressive strength of 40 MPa, achieving an optimal carbon-to-strength ratio. The inclusion of polypropylene fiber significantly influences the mode of compression failure in alkali-activated binders. Alkali-thermal activation of red mud elevates the levels of active silicon and aluminum, markedly augmenting the reactive silica and aluminum content. This modification fosters the disintegration and reorganization of Si-O and Al-O bonds in silica-aluminum materials, culminating in a denser structure. This structure is characterized by the generation of amorphous ((N, C)-A-S-H) gels, contributing to the material's enhanced properties.

Investigating the potential of unconventional resources in the Midland Basin: A comprehensive chemostratigraphic analysis of a Cline Shale (Wolfcamp-D) core

Basinal mudrocks assigned to the Wolfcamp Group in the Midland Basin are prolific producers of oil and gas. Technological advancements in horizontal drilling and hydraulic fracturing have been successful in the exploitation of oil and gas from these tight mudrocks. However, many challenges remain unsolved in capturing their macroscale compositional variations to enhance recovery factors and delineate “sweet spots”. To gain improved insights into this fine-grained system, high resolution chemostratigraphic (XRF) data was integrated with mineralogical measurements (XRD), logs, thin sections, and TOC readings, as well as hierarchical cluster analysis to: 1) develop a sequence stratigraphic framework, and 2) reconstruct paleo-redox, as well as ancient water-mass, conditions within the Cline Shale (Wolfcamp-D) from a core in the Midland Basin.This study revealed the presence of three chemo-stratigraphically distinct depositional sequences in the Cline Shale, herein termed Lower, Middle, and Upper Cline from the base upwards. All three units exhibit distinct mineralogical and petrophysical characteristics, were correlated across the basin, and interpreted as third-order sequences. Superimposed onto the three interpreted third-order sequences within the Cline, are potential higher frequency (fourth-order) sequences. These fourth-order sequences typically consist of a lower interval, interpreted as lowstand deposits and an upper interval, which is interpreted as transgressive and highstand deposits. The lower interval is interpreted to be deposited during highly reducing conditions while the upper interval is interpreted to be deposited under suboxic conditions. The highest organic matter preservation is associated with the interpreted lowstand deposits, especially in the Upper Cline. Optimal landing zones (20 ft) are recognized in the upper zone of the Cline Shale based on their high resistivity, total organic richness, elevated siliceous content, and reduced percentage of clay minerals. These zones have been correlated with several nearby wells.The current study demonstrates the wealth of information that can be gained from a single core/well when properly investigated at high resolution with measurements on a cm-scale. The observed shifts in the chemistry of the sediments character and composition are distinct, with implications for sequence stratigraphic analysis, the reconstruction of ancient water-mass conditions, and the identification of “sweet spots” for hydrocarbon resources. The provided analysis lays a foundational basis for further studies in the region, serving as critical data input for expansive regional research efforts.

Utilization of silicon dioxide nanoparticles and silicon salts to enhance astaxanthin production in Haematococcus Pluvialis

Haematococcus pluvialis is a type of microalgae that is commercially important as it is the primary source of natural astaxanthin - a potent antioxidant used in nutraceuticals, cosmetics, food, and aquaculture industries. Various nanoparticles and chemicals have been used to stimulate the growth of H. pluvialis to increase astaxanthin production. In this study, silicon nanoparticles were synthesized from tetraethyl orthosilicate (TEOS) and characterized to ensure the pure synthesis of uniform nanocrystals of silicon dioxide. The microalgae were cultivated in optimal Haematococcus medium (OHM) under specific conditions, including a temperature of 25 °C, a pH of 7, and a light intensity of 50 μmol. s−1.m−2 for 12 h of light and 12 h of darkness. To study the amount of viability and astaxanthin production, the microalgae were exposed to different concentrations of silicon, sodium silicate, calcium silicate, and potassium silicate. The highest astaxanthin production (194 mg/g) was obtained after stimulation at 200 μg/ml of silicon compared to the control after 15 days by high-performance liquid chromatography (HPLC) technique. Therefore, it can be concluded that certain concentrations of silicon and silicon salts can be considered a suitable stimulus to produce astaxanthin in the H. pluvialis microalgae. This study highlights the potential of using silicon nanoparticles as a stimulant for astaxanthin production in H. pluvialis, which could have significant implications for the nutraceuticals, cosmetics, food, and aquaculture industries.

Synergistic enhancement of rheological and anti-aging properties of asphalt modified with bio-oil and layered silicate

Applying bio-oil to asphalt pavement effectively reduces the dependence on traditional petroleum asphalt in pavement industry. However, the utilization of bio-oil can encounter rutting and aging issue of modified asphalt. To solve the aforementioned issue, two kinds of organic layered silicates with typical structures were adopted to enhance the high-temperature and anti-aging performance of the bio-modified asphalt. The modification mechanism and the synergistic effect of bio-oil and organic layered silicate on asphalt were explored through rheological characterization, infrared spectroscopy tests, gel chromatography tests, etc. Results showed that the incorporation of layered silicate in bio-modified asphalt can improve asphalt-filler interaction and hence the high-temperature and fatigue performance of asphalt. When the content of layered silicate is 5 %, the negative effect of Castor oil on the high-temperature performance of asphalt can be eliminated. Still, for Turpentine wood oil and Straw oil, the content of layered silicate is 7 %, which shows the same effect. The waste bio-oils can balance the low-temperature performance of asphalt modified with layered silicates. Furthermore, the addition of layered silicates was effective to reduce oxidation reaction and improve the anti-aging performance of bio-oil modified asphalt. When the ratio of layered silicate to bio-oil is 1 1, the composite-modified asphalt maintains the best anti-aging performance. Specifically, Castor oil, Straw oil, and OMMT are more suitable, and Turpentine wood oil and OREC are more appropriate. According to the quantification of the functional group aging index, the SI and CI of the optimal ratio of different types of bio-oil asphalt are Castor oil: 61.64 % and 59.41 %, Turpentine wood oil: 50.02 % and 53.57 %, Straw oil: 50.01 % and 55.05 %. Composite modified asphalt can be applied to complex service conditions.

AI-driven design for the compressive strength of ultra-high performance geopolymer concrete (UHPGC): From explainable ensemble models to the graphical user interface

Ultra-high performance geopolymer concrete (UHPGC) has become of interest in recent years as a more economical and sustainable alternative while offering similar mechanical performance to ordinary ultra-high performance concrete (UHPC). The lack of an effective mix design methodology has inhibited the widespread use of UHPGC, despite its potential. This paper adopted an artificial intelligence (AI)-based approach to accurately model the compressive strength (CS) of UHPGC, a critical parameter to ensure structural integrity and reliability. Ensemble machine learning (ML) models such as RF, XGBoost, LightGBM and AdaBoost, which have been very popular lately, were selected as AI algorithms. For the establishment of these models, a comprehensive and reliable dataset of 181 test results was used, including 13 input features. Additionally, feature importance and Shapley additive explanations (SHAP) analyses were used to ensure the explainability of the prediction models and tackle the "black box" challenge of ML models. The results obtained revealed that all ensemble models successfully predicted the CS of UHPGC; in particular, the XGBoost model consistently exhibited the best overall performance in terms of higher R2 (0.948) and lower RMSE (6.68), MAE (4.73), MAPE (4 %), and mean error value (1.095), in the test phase. Moreover, feature importance and SHAP analyses revealed that the most influential features on the CS of UHPGC were age, fiber and silica fume, sodium silicate (Na2SiO3), and water content. Lastly, a graphical user interface (GUI) was developed to easily predict the CS of UHPGC in practical applications.

Siliceous deposition in limestone-marl alternations of the Yangtze Carbonate platform during the Permian Chert Event

During the Permian Chert Event (PCE), limestone-marl alternations (LMAs), contemporaneously developing in the Yangtze region with chert-mudstone alternations, differed from typical LMAs by their enrichment in authigenic siliceous components (quartziferous components and Mg-phyllosilicates). However, the factors driving the transition from distal chert deposits to proximal siliceous-rich carbonate deposits remain unclear, and the genesis of authigenic siliceous components is puzzling. Resolving these issues could provide a deeper understanding of the paleoclimate and paleoenvironment during the PCE. Optical and SEM observations and geochemical analyses revealed that Si4+, derived from seawater, silica-secreting organisms, and terrigenous clasts, precipitated as authigenic quartziferous components under relatively acidic conditions, while it precipitated as Mg-phyllosilicates through reverse weathering by combining with the dissolved high-Mg calcites under relatively alkaline conditions. Through the facies division of LMAs, its variations describe relative and short-term sea-level fluctuations in the Yangtze Carbonate Platform (YCP). By integrating tendency comparisons and time series analyses of sea level fluctuations, continental weathering intensity, authigenic siliceous content, and relative proportions of quartz vs. Mg-phyllosilicates, four proxies exhibit covariation and similar astronomical signals, indicating that the high sea level period of the YCP, corresponding to intensified continental weathering, favored the deposition of authigenic siliceous components and reverse weathering. Because the facies variations encompass short eccentricity, obliquity, and precession cycles, sea level fluctuations are considered to have been influenced by Gondwana glaciation P3. The seawater in the continental shelf cooled and became rich in silica and nutrients under the effect of upwelling. Interglacial periods may trigger high sea levels and intensified continental weathering in the YCP, facilitating the influx of Si-rich eutrophic seawater and stimulating biological silica secretion by radiolarians. However, the direct precipitation of activated silica resulted in weakened reverse weathering. Consequently, the lithological transformation from distal to proximal areas during the PCE was attributed to differences in silica-secreting organism abundance, upwelling intensity, biological pump activity, reverse weathering intensity, OM abundance, pH conditions, and seawater temperature between the continental shelf and carbonate platform.

Bottom water quality plasticity in the northern gulf of Mexico hypoxic zone

The growth of the now ubiquitous hypoxic zones found throughout the global coastal ocean are primarily a consequence of nutrient enrichment in surface waters increasing organic production that sinks into bottom waters where oxygen is depleted faster than it is replenished. Hypoxic zones may increase or decline in number because of future climate changes. Here we summarize the summertime variations of dissolved inorganic silicate (DSi), phosphate (DIP), nitrogen (DIN; nitrate + nitrite and ammonium) and ammonium concentrations in the bottom waters of the northern Gulf of Mexico continental shelf from 1985 to 2022. The concentrations of all three are strongly correlated to oxygen concentrations, but not in the same way. At zero oxygen concentration, the annual concentrations of DSi, DIP, and ammonium changed over 38 years at a rate of 1.6 % y−1, 2.0 % y−1 and -1.7 % y−1, respectively. However, the nitrate + nitrite concentrations at zero oxygen concentrations did not change over the same interval. The silicate efflux from anoxic sediments is directly related to warming temperatures and is co-related to phosphate concentrations. The bottom water DSi:DIN molar ratios increased over three decades as DIN:DIP molar ratios decreased, suggesting strong nitrogen limitation compared to silicate and phosphate, and reveal significant plasticity in regeneration rates in the bottom waters that may be dependent on changes in the surface waters. Hypoxia and food web models based on a stationary equipoise of these amounts and ratios in surface and bottom waters will likely be deficient as coastal waters warm, acidification increases, and river water quality changes. Data refreshment and improved understanding of food web changes and warming futures are recommended.

The Extent of Response to Spraying with Different Concentrations of Potassium Silicate and Planting Dates on Yield Traits of Safflower (Carthamus tinctorius L.)

The Extent of Response to Spraying with Different Concentrations of Potassium Silicate and Planting Dates on Yield Traits of Safflower (Carthamus tinctorius L.)

Physical Mechanisms Sustaining Silica Production Following the Demise of the Diatom Phase of the North Atlantic Spring Phytoplankton Bloom During EXPORTS

AbstractEach spring, the North Atlantic experiences one of the largest open‐ocean phytoplankton blooms in the global ocean. Diatoms often dominate the initial phase of the bloom with succession driven by exhaustion of silicic acid. The North Atlantic was sampled over 3.5 weeks in spring 2021 following the demise of the main diatom bloom, allowing mechanisms that sustain continued diatom contributions to be examined. Diatom biomass was initially relatively high with biogenic silica concentrations up to 2.25 μmol Si L−1. A low initial silicic acid concentration of 0.1–0.3 μM imposed severe Si limitation of silica production and likely limited the diatom growth rate. Four storms over the next 3.5 weeks entrained silicic acid into the mixed layer, relieving growth limitation, but uptake limitation persisted. Silica production was modest and dominated by the >5.0 μm size fraction although specific rates were highest in the 0.6–5.0 μm size fraction over most of the cruise. Silica dissolution averaged 68% of silica production. The resupply of silicic acid via storm entrainment and silica dissolution supported a cumulative post‐bloom silica production that was 32% of that estimated during the main bloom event. Diatoms contributed significantly to new and to primary production after the initial bloom, possibly dominating both. Diatom contribution to organic‐carbon export was also significant at 40%–70%. Thus, diatoms can significantly contribute to regional biogeochemistry following initial silicic acid depletion, but that contribution relies on physical processes that resupply the nutrient to surface waters.

Study on the microscopic characteristics and hydration mechanism of thermo-alkali activated electrolytic manganese residue geopolymers

As a form of solid waste, electrolytic manganese residue (EMR) exhibits low reactivity, high sulfate content, and exceeds the standards for heavy metals. To address these drawbacks, a high-temperature thermal activation method was employed to enhance its reactivity and remove pollutants. The study investigated the physicochemical properties and leaching toxicity of EMR under different thermal activation conditions. Additionally, the thermally activated EMR was utilized in the preparation of geopolymer material, and the influence of EMR activation temperature, EMR content, sodium silicate content, and molar ratio on the mechanical properties, hydration mechanism, microstructure, and leaching toxicity of the EMR geopolymers was analyzed. The results indicated that after activation in the temperature range of 0–1200°C, the active content of silica-alumina in EMR increased, sulfate decomposition occurred, and the leaching of Mn2+ and NH4+-N decreased to 21.24 and 0.576 mg/L, respectively. When the activation temperature reached 1200°C, the compressive strength of the geopolymer, prepared with 50 % EMR, 50 % granulated blast furnace slag (GBFS), 30 % sodium silicate, and a molar ratio of 1.2, could reach 53.2 MPa at 28-day. Under activation in the range of 0–800°C, ettringite was abundant in the geopolymers, providing strength support. With activation in the range of 800–1200°C, the geopolymers became denser, exhibiting flaky and agglomerate gels. A diffraction peak appeared at 20°-40°(2θ) corresponding to C-(A)-S-H and N-S-A-H gels. Due to the slow depolymerization-polymerization kinetics of the EMR geopolymer and high sulfate content, the heat release rate and cumulative heat were significantly lower than ordinary portland cement (OPC). In the structure of EMR geopolymer, Mn2+ replaced Na+ and Ca2+ in the silicoaluminate structure or chemically bonded with anionic groups to the geopolymer. Simultaneously, Mn2+ participated in the formation of the EMR geopolymer gel, encapsulating within the gel. Therefore, the leaching of pollutants from EMR geopolymers met the standards of GB8978–1996.

Novel gelatin/ chitosan double network hydrogel reinforced by lignin and calcium silicate for potential treatment of bone defects

Artificial materials for the potential treatment of bone defects are very trendy in such research fields. To investigate a hydrogel scaffold with better mechanical strength and osteoinductivity is always a challenge since brittle and soft properties are always the problems in traditional hydrogels. In our study, a novel gelatin/chitosan hydrogel crosslinked by a double network filled with lignin and calcium silicate is fabricated. Enhancements of mechanical strength, low swelling ratio, and improvement in osteoinductivity were achieved in this composite double network hydrogels. The results revealed that lignin was a key factor in raising the compressive strength and stability of the hydrogel because more hydrogen bonds were formed between lignin and the crosslinking network. Even after swelling equilibrium, the compressive strength remained almost unchanged. In addition, the hydrogel groups with a higher ratio of lignin also had lower cytotoxicity and improved osteoinductivity of pre-osteoblasts while the increasing concentration of calcium silicate progressively weakened these performances. Therefore, the gelatin/chitosan double network hydrogel reinforced by lignin would be a potential bone tissue-engineered artificial material.

Cement-based external wall insulation material with thermal performance improvement by partial substitution of calcium silicate

External wall composite insulation materials have shown great potential for energy saving and emission reduction in the construction industry, but cement-based material as one of the external wall composite insulation materials has the problem of high thermal conductivity. Herein, a composite insulation material was prepared using the press method by expanded polystyrene (EPS) and cement of different calcium silicate content. The addition of porous calcium silicate provides nucleation sites for cement hydration to promote hydration reaction and increase the porosity of the inorganic cementitious phase from 75 % to 85 % and refine the average pore size from 2826.09 nm to 421.31 nm. The cement-based composite insulation material which the calcium silicate content is 20 % has 0.0423 W/(m·K) in the thermal conductivity, which is 23.1 % lower than the non-calcium silicate content of cement-based composite insulation material (0.055 W/(m·K)). The simulation analysis proves that the improved insulating properties are attributed to the increased interface between solid-phase and gas phase, thinner heat transfer walls, and longer heat transfer paths due to the pore structure changes in the inorganic cementitious phase. This proposed composite insulation material provides a new choice for external wall insulation.