Formation Of Calcium Silicate Research Articles

Evaluation of mechanical strength, gamma-ray shielding characteristics, and ITZ microstructural properties of heavyweight concrete using nano-silica (SiO2) and barite aggregates

This research assessed the mechanical performance, gamma-ray shielding, and interfacial transition zone (ITZ) microstructural properties of concrete mixes that incorporate barite coarse aggregates and nanosilica. To achieve this goal, several concrete mixes containing normal coarse aggregate (NC), barite aggregate (BC), and nano-silica/barite aggregates (NSBC) were fabricated. Several properties such as workability, mechanical strength, electrical resistivity (ER), ultrasonic pulse velocity (UPV), chloride migration (RCPT), and gamma shielding were comparatively assessed for these concrete mixtures. In addition, analytical characterizations viz., x-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electronic microscopy (SEM), and energy dispersive x-ray (EDX) were employed to study the ITZ microstructure at mortar/aggregate interface of concrete mixtures. The results showed that barite concrete incorporating nanosilica (NSBC) exhibited higher density and improved mechanical properties compared to both normal concrete (NC) and barite concrete (BC). Specifically, concrete mixture containing barite aggregate and 3% nanosilica (3NSBC) content exhibited improved impermeability and reduced concrete porosity. The gamma-ray shielding properties for 3NSBC were superior among all concrete mixtures. After 28 days, 3NSBC exhibits higher compressive strength (18.26% and 14.76%) and greater shielding capacity (12.82% and 6.66%) compared to NC and BC, respectively. The analytical characterizations results have demonstrated that nanosilica helps prevent the accumulation of calcium hydroxide in the ITZ by utilizing it to form calcium silicate hydrate. This leads to the development of a more compact and denser microstructure in the ITZ of nano-silica-based barite concrete (NSBC). Furthermore, it was revealed that, the incorporation of nanosilica exceeding 3% led to agglomeration, resulting in a weaker ITZ within the concrete leading to overall reduction in concrete properties.

Atomic‐level structure evolution of calcium silicate hydrate nucleation process, the amorphous‐to‐crystalline pathway

AbstractCalcium silicate hydrate (C‐S‐H) synthesis follows multistep nucleation processes ranging from amorphous globules to nanocrystals. This type of nonclassical nucleation pathway attracts extensive interest and yet related molecular processes are mostly unexplored. Herein, atomic‐level structure evolution during this process is unveiled. From inside to outside of the globule, the atomic arrangement evolves from amorphous configuration to layered stacking of calcium silicate layers with layers spaced by 1.1 nm. Numerous cations surrounding the globules provide extra calcium ions to form nano C‐S‐H foils at the edge of the globule. The polymerization to form calcium silicate chains has almost been completed before 5 min reaction, and the C‐S‐H structure formation is basically based on the self‐assembly to be calcium silicate layers and then lamellar crystal inside the globule. Silicate chain defects inhibit a‐ and c‐axes crystallization, but promote b‐axes one, leading to anisotropic growth of crystalline C‐S‐H. The defects lead to the crystallization pathways conversion from Si–O–Si bonds formation to Ca2+ electrostatic linking.

Ceramic-added lime and cement mortars: A review of applications in building products.

Ceramic-added air lime mortars have been used since ancient times owing to the pozzolanic effect provided by crushed ceramic particles that impart hydraulic properties. This work reviews the historical use, composition, reaction mechanisms, characterization techniques, and performance properties of ceramic-added air lime mortars. The fine ceramic powder composed of silica and alumina phases reacts with calcium hydroxide released during lime hydration to form calcium silicate hydrates (CSH) and calcium aluminate hydrates (CAH) via pozzolanic reaction. This provides hydraulicity and reduces setting time compared to pure air lime mortars. The coarser ceramic particles also serve as aggregate and refine the microstructure as filler. The reactivity depends on the ceramic composition, amorphous phase content, particle size distribution, and firing temperature. Optimal proportioning of the fine ceramic powder and coarse ceramic aggregate is necessary to achieve desired properties. Ceramic addition enhances the durability of air lime mortars against weathering while maintaining compatibility with lime-based masonry structures. Key novelties of this review include: (i) in-depth analysis of the influence of ceramic characteristics (mineralogy, particle size, pozzolanicity) and processing on reaction kinetics and phase evolution; (ii) systematic assessment of mechanical, physical and durability properties in comparison to conventional air lime mortars and cement-based grouts; (iii) elucidation of microstructural mechanisms governing performance using advanced characterization techniques; (iv) critical appraisal of test methods and standards for evaluation; and (v) rigorous discussion on potential applications in construction, conservation and repair, with case studies.

A critical review of experimental research on the durability of cement modified with partial steel slag replacement

The construction industry is looking for sustainable and cost-effective alternatives to conventional building materials. As the world faces increasing environmental challenges, the need for greener construction practices has become more urgent. Cement production is known for its high energy consumption and significant carbon dioxide emissions. Therefore, it is essential to find ways to reduce the environmental impact of cement production and use. One promising area of research is the use of industrial byproducts such as steel slag to partially replace cement in concrete. The use of these by-products not only solves the problem of waste disposal but also provides a sustainable solution to improve the properties of building materials. When mixed with cement, steel slag participates in pozzolanic reactions, in which reactive silica from the slag reacts with calcium hydroxide, produced during the hydration of cement, to form calcium silicate hydrate gel (CSH). This CSH gel is responsible for the strength and durability of concrete. Incorporating steel slag can improve the mechanical properties of concrete, including compressive, flexural, and tensile strength. In addition, steel slag can improve the durability properties of concrete, such as resistance to chemical attack, reduced permeability, and increased resistance to physical and chemical degradation over time. This paper investigates the durability properties of cement when partially replaced by steel slag, focusing on various aspects of durability, including resistance to chemical attack, mechanical strength, and long-term performance under various environmental conditions. The study includes a comprehensive experimental program designed to evaluate the impact of steel slag on the durability of concrete through a series of tests and analyses.

Nano soil improvement technique using cement

Nano soil-improvement is an innovative idea in geotechnical engineering. Nanomaterials are among the newest additives that improve soil properties. Herein, laboratory tests, such as unconfined compressive strength, direct shear test, and initial tests, were conducted to investigate the geotechnical properties of Kelachay clay with micro- and nanosized cement to evaluate its particles in untreated soil and observe changes in the behavioral properties of treated soil compared to those of untreated soil. Scanning electron microscopy and X-ray fluorescence images were analyzed before and after the grinding process to determine the nature of the studied particles. Furthermore, effects of time and nanocement content (0%, 1%, 3%, 5%, and 7%) on curing performance were evaluated. The optimum percentage of nano-cement was found to be 7%, which increased the unconfined compressive strength by up to 29 times and reduced the strain at rupture by 74% compared to the untreated soil. The results showed that nano-cement significantly improved the strength and stiffness of the soil–cement mixture by forming calcium silicate hydrate (C–S–H) gel that filled the pores and bonded the soil particles. Nano-cement also acted as a nucleation site for more C–S–H growth, enhancing the durability and strength of the mixture.

Remediation of Cu, Cr(VI) and Pb polluted soil with industrial/agricultural by-products in seasonally frozen areas

Soils contaminated with potentially toxic elements (PTEs) may face serious environmental problems and pose health risks. In this study, the potential feasibility of industrial and agricultural by-products as low-cost green stabilization materials for copper (Cu), chromium (Cr(VI)) and lead (Pb) polluted soil was investigated. The new green compound material SS ∼ BM ∼ PRP was prepared by ball milling with steel slag (SS), bone meal (BM), and phosphate rock powder (PRP) which had an excellent stabilization effect on contaminated soil. Under 20% SS ∼ BM ∼ PRP addition into the soil, the toxicity characteristic leaching concentrations of Cu, Cr(VI) and Pb were reduced by 87.5%, 80.9% and 99.8%, respectively, and the phytoavailability and bioaccessibility of PTEs were reduced by more than 55% and 23%. The freezing-thawing cycle significantly increased the activity of heavy metals, and the particle size became smaller due to the fragmentation of the soil aggregates while SS ∼ BM ∼ PRP could form calcium silicate hydrate by hydrolysis to cement the soil particles, which inhibited the release of PTEs. Different characterizations indicated that the stabilization mechanisms mainly involved ion exchange, precipitation, adsorption and redox reaction. Overall, the results obtained suggest that the SS ∼ BM ∼ PRP is a green, efficient and durable material for remediation of various heavy metal polluted soils in cold regions and a potential method for co-processing and reusing industrial and agricultural wastes.

Mineral-induced catalytic mechanism of sodium-calcium binary catalyst during coal char gasification

Binary catalyst composed of alkali metal and alkaline earth metal was widely used to overcome the shortcoming of single-metal catalyst. However, the synergistic mechanism between components remains unclear. In present work, sodium and calcium were loaded into the coal char individually or together. TGA gasification was used to investigate catalytic effect. In order to evaluate catalytic mechanism, Raman spectra of gasification residue, Raman spectra of quenched slag and phase composition at thermodynamic equilibrium were obtained. Loading of sodium or calcium significantly increased gasification rate of coal char and catalytic effect of sodium was better than calcium. Above 900 °C, catalytic effect of sodium-calcium binary catalyst was better than that of single catalyst, and gasification residue of binary catalyst loaded char had more calcium silicate and less sodium silicate than gasification residue of single-metal catalyst loaded char. It was speculated that calcium reacted first with silica in coal to inhibit sodium inactivation. Raman spectra of quenched slag and theoretical calculation showed that silica preferentially reacted with calcium oxide to form calcium silicate in calcium oxide-sodium carbonate-silica system, which proved above speculation. Furthermore, the significant catalytic activity of binary catalysts inhibited the graphitization evolution of carbon structure during char gasification, which is conducive to the improvement of gasification rate.

Designing low-carbon cement-free binders for stabilization/solidification of MSWI fly ash

Low-carbon and high-efficiency binder is desirable for sustainable treatment of municipal solid waste incineration fly ash (MSWI FA). In this study, CaO or MgO was used to activate ground granulated blast furnace slag (GGBS) to form calcium silicate hydrate and magnesium silica hydrate gel for stabilization/solidification of hazardous MSWI FA. Experimental results showed that potential toxic elements (PTEs), such as Pb and Zn, significantly inhibited the formation of reaction products in CaO-GGBS system due to the complexation between Ca(OH)2 and PTEs, whereas PTEs only had insignificant inhibition on transformation from MgO to Mg(OH)2 in MgO-GGBS system, resulting in lower leachabilities of PTEs and higher mechanical strengths. Stabilization/solidification experiments demonstrated that MSWI FA (70 wt%) could be recycled by MgO-GGBS binder (30 wt%) into blocks with desirable 28-day compressive strengths (3.9 MPa) and PTEs immobilization efficiencies (99.8% for Zn and 99.7% for Pb). This work provides mechanistic insights on the immobilization mechanisms of PTEs in CaO/MgO-GGBS systems and suggests a promising MgO-GGBS binder for low-carbon treatment of MSWI FA.

Carbon fiber surface nano-modification and enhanced mechanical properties of fiber reinforced cementitious composites

It has been widely recognized that fiber–matrix interface has great significance on the performance of fiber-reinforced cementitious composites. In this research, an effective fiber modification method is proposed and its enhanced mechanical properties are observed. Through the condensation and polymerization of the tetraethyl orthosilicate under alkaline conditions, a thin SiO2 layer was formed on carbon fiber surface, which can react with Ca(OH)2 thus form calcium silicate hydrate to condense the fiber–matrix interface. In this paper, nano-SiO2 modified carbon fibers are produced and the mechanical properties of modified carbon fiber reinforced cementitious composites are investigated. Modified material exhibited 24.7% enhancement in flexural strength and up to 25.1% enhancement in tensile strength with the fiber volume fraction of 0.5%. Better post-crack behavior and toughness properties were also estimated, which were attributed to nano-modification strengthening the ITZ through the reaction of surface nano-SiO2 with Ca(OH)2 resulting in much more amount of CSH gel and a denser microstructure of fiber–matrix interface. The microstructure of denser interface and porosity can be found through SEM and BSEM analysis. The porosity on the observation surface of interface transition zone of unmodified fiber and modified fiber was 4.03% and 2.43%, respectively. The change of chemical elements in the interface transition zone was analyzed by line scanning, and the Ca/Si of the modified carbon fiber was significantly lower than that of the unmodified carbon fiber.

The Stabilization Mechanism of Nano-SiO2 Precursor Solution.

The issues associated with the fabrication of nano-silica (NS) mineral powder, such as high cost and agglomeration, can be effectively mitigated by using a precursor solution of NS as the external mixture of cement-based materials. Based on the liquid-phase preparation of NS mineral powder, its preparation technology was thoroughly investigated herein. The precursor solution of NS was synthesized using acid media (HCL, HNO3, HBO3, HCOOH, CH3COOH)—the acetic acid concentration was 1~15%—and siliceous materials. (The concentration of sodium silicate was 20~38%). In addition, the pH value (pH4~pH8) of the precursor solution was measured using a pH detector. The indexes of NS, such as precipitation time, morphology, and distribution, were observed to formulate a preparation technique for the precursor solution of NS that possessed the best results for the precipitation of nanoparticles. From the acquired results, it was demonstrated that acetic acid solution (concentration ≤ 3%) and sodium silicate solution (concentration ≤ 25%) were mixed into a solution with pH = 6, which was the optimum mixing ratio for the precursor solution of NS. The prepared precursor solution of NS was also added to the Ca(OH)2 saturated solution, and the precursor solution became active from a stable state. Then, NS particles were precipitated in an alkaline solution and reacted with Ca(OH)2 to form calcium silicate gel, which made the solution increasingly turbid and generated many visible and uniformed flocculating substances. With time, gels were continuously produced, which then turn white. Similarly, NS particles can be precipitated when the precursor solution is added to cement paste, which reacts with the Ca(OH)2 to generate CSH gel and improve the compactness of the cement paste.

New understanding on formation mechanism of CaFe2O4 in Fe2O3 -Fe3O4-CaO-SiO2 system during sintering Process: Phase transformation and morphologies evolution

The complex calcium ferrite is the main binder phase of high basicity, high iron and low silicon sinter used in blast furnace (BF), and its formation amount and structure are important factors affecting sinter quality. This work research on the phase transformation and morphologies evolution of Fe2O3 -Fe3O4-CaO-SiO2 systems roasted 900 °C − 1200 °C in air atmosphere to understand the formation process of calcium ferrite. In CaO-Fe3O4 system, the prolonged roasting time and higher temperature promotes that CaFe5O7, CaFe3O5, and Ca2Fe2O5 gradually transformed into the stable existence of CaFe2O4. In CaO-Fe3O4 system, the higher temperature promotes that the combination of Fe3O4 and CaO formed the stable CaFe3O5 with orthorhombic structure. The replacement reaction between the newly formed CaFe3O5 phase and the unreacted CaO phase occur to form Ca2Fe2O5. In CaO-Fe3O4-SiO2 system, FeSiO3 can be combined with Fe3O4 to form Fe2SiO4 and Fe2O3. Under the action of high temperature, FeSiO3 and CaO undergo displacement reaction to form the unstable CaSiO3, the new formation of CaSiO3 can be easily combined with CaO to form the stable Ca2SiO4. With the further increase of temperature, the complex calcium ferrite is formed in calcium silicate layer. The final product complex calcium ferrite and calcium silicate exist at the same time. The formation of calcium silicate has an unfavorable effect on formation of complex calcium ferrite in the sintering process.

Role of pH value on electrophoretic deposition of nano-silica onto carbon fibers for a tailored bond behavior with cementitious matrices

Electrophoretic deposition (EPD) of nano-silica (NS) onto carbon fiber (CF) surfaces may considerably improve the bond properties toward cementitious matrices. In the article at hand, varied pH conditions (neutral, acidic, and alkaline environments) are studied during EPD for a tailorable interfacial bond. Zeta potential measurements and cyclic voltammetry (CV) confirmed the importance of pH with regard to the EPD process. Scanning electron microscopy (SEM) and X- ray photoelectron spectroscopy (XPS) revealed that an acidic environment enables the most pronounced and homogeneous NS coating on the CF surfaces. X-ray diffraction (XRD) analysis delivered deeper insights into the microstructures of modified CFs, indicating a decreased graphite interlayer spacing d002 and an increased crystallite size Lc after treatment. This results in a changed temperature-stability as well as mechanical properties, as revealed by thermogravimetric analysis (TGA), single-fiber tensile tests, and Weibull analysis.To assess the interaction of the modified CFs with cementitious matrices, single-fiber pullout tests were performed, showing the highest bond strength and total pullout work of CFs treated in an acidic environment. This is mainly explained by a reaction of the high number of NS particles with calcium hydroxide to form calcium silicate hydrate (C-S-H) gel and, thus, intensifying the interfacial transition zone, subsequently increasing the bond properties of CF to a matrix. As well, abundant oxygen-related functional groups were introduced on the CF surfaces from anodic oxidation, leading to an enhanced bond by promoting precipitation of cement hydration products onto the CF surfaces.

LCA of Mortar with Calcined Clay and Limestone Filler in RC Column Retrofit

Cement manufacture contributes about 5–7% of the global carbon dioxide emission. The fastest short-term remedy is to replace parts of ordinary Portland cement (OPC) in concrete with supplementary cementitious materials (SCMs) to reduce CO2 emissions. Calcined clay and limestone filler have proven to be potential substitutes to good quality SCMs such as fly ash and slag because of their abundance, low cost, and potential reactivity to calcium hydroxide to form calcium silicate hydrates (C-S-H) which are responsible for the strength and other mechanical properties of concrete. A life cycle assessment (LCA) to evaluate the environmental impact of mortar with calcined clay and limestone filler in reinforced concrete (RC) column retrofitting is carried out using data from a multi-purpose complex project in Rizal province in the Philippines. A total of four retrofitting methods are evaluated based on two retrofitting techniques (RC column jacketing and steel jacketing) with two material alternatives (pure OPC-based mortar and mortar with partial replacements). Results show that RC column jacketing using patched mortar with partial replacement of calcined clay and limestone fillers is the least environmentally damaging retrofit option. The use of these SCMs resulted in a 4–7% decrease in global warming potential and a 2–4% decrease in fine particulate matter formation. Meanwhile, RC column jacketing decreased the effect on human carcinogenic toxicity by 75% compared to steel jacketing.

Enhancing magnetism of ferrite via regulation of Ca out of sit A from spinel-type structure by adjusting the CaO/SiO2 mass ratio: Clean and value-added utilization of minerals

Ferrites with a typical AB2O4 structure are excellent soft magnetic material precursors. One progress for preparation of manganese ferrite is to use the minerals as raw materials. However, the inclusive impurities, such as Ca and Si, may dope in the AB2O4 structure and have an adverse effect on the magnetism of ferrites. In this work, the effects of CaO and SiO2 on the crystalline structure transformation, interfacial elements distribution, and magnetism change of the MnO2-Fe2O3-CaO-SiO2 system for preparation of high-performance ferrite materials were systematically investigated. It's found that Ca ions can readily be doped in the sit A of spinel-type structure to form CaaMnbFe2O4, and the magnetism of manganese ferrite was observably declined due to the Ca doping. A diffusion couple of synthetic CaaMnbFe2O4 and SiO2 was designed to determine the Ca migration. Results demonstrated that regulation of Ca out of sit A from the spinel-type structure can be successfully realized via adjusting the CaO/(CaO ​+ ​SiO2) mass ratio below 0.55, and the magnetism of ferrite after Ca migration was obviously enhanced. The migrated CaO combined with SiO2 to form calcium silicate which was distributed at the boundaries of ferrite particles. Eventually, the verification test of low-grade manganese ores with CaO and SiO2 impurities was conducted to validate the Ca migration effect.

The effect of calcination conditions on oat husk ash pozzolanic activity

Supplementary cementitious materials (SCMs) are known and used to reduce cement consumption, but some waste sources currently used for partial cement replacement are threatened by changing industrial production processes and local availability. Thus, considering possible sources of amorphous silica for use as SCM, especially pozzolans, there is an opportunity to investigate the use of agricultural residues such as oat husks, which currently have little or no commercial value. This work aims (i) to identify the burning temperature that promotes the reduction of carbon content and increase the amorphous material, (ii) to present the chemical and physical characterization analysis results, and (iii) to evaluate the pozzolanic potential of selected oats husks ashes (OHA) produced under controlled calcination temperatures. Local samples of oat husks were sun-dried, sieved, and split into two portions. One portion was subjected to analysis of moisture content, and the second portion was pre-calcined at 350 °C for 2 h in an aerated laboratory oven and turned into ashes under 400 to 700 °C respectively, using ramp heating rate of 10 °C/min. The ashes were ground in a ball mill and subjected to chemical and physical analysis, considering Loss on Ignition (LOI) at 950 °C, chemical composition through Energy Dispersive X-Ray Analysis (EDX), structural state analysis by X-ray diffraction (XRD), morphology by digital microscopy, density using glass pycnometer and chemical reactivity with calcium hydroxide measured through thermogravimetric analysis of a control mortar defined as (R3) model paste. The results show that the ash chosen for pozzolanic potential analysis, produced at 600 °C, shows an average ash content value of 3.6%, and chemical concentration of 45.97% oxygen (O), 21.2% silicon (Si), and 16.91% potassium (P), in addition to evidence that characterizes crystallization of its structure and consumption of 8.74% of Ca(OH)2 from the control matrix, indicating low pozzolanic activity. It was concluded that local oat husks in Ireland calcinated between 600 and 700 °C presented a favorable balance between the percentage of residual carbon amount and silica in the amorphous form that is favorable to react with calcium hydroxide forming calcium silicate hydrate. It opens up a possibility of investigating the use of OHA as SCM, requiring more studies about the oats husks calcination time, cement replacement rate, and performance tests to consider practical applications, and maybe contributing to reducing the OPC consumption, production necessity, and consequently, the environmental issue caused by its production.

Effects of Silicic Acid on Leaching Behavior of Arsenic from Spent Calcium-Based Adsorbents with Arsenite

The spent adsorbents that remain after being used to purify As-contaminated water constitute waste containing a large amount of As. These spent adsorbents, after being disposed, are likely to come into contact with silicic acid leached from the soil or cementitious solidification materials. Thus, it is crucial the evaluate the effects of silicic acid on spent adsorbents. In this study, the effects of silicic acid on spent Ca-based (CaO and Ca(OH)2) adsorbents with arsenite were investigated. The As leaching ratio for the spent adsorbents decreased with an increase in the initial concentration of silicic acid in the liquid. Under the tested conditions, the As leaching ratio decreased from 8–9% to less than 0.7% in the presence of silicic acid at an initial Si-normalized concentration of 100 mg/L. The primary mechanism behind the inhibition of As leaching by silicic acid was determined to be re-immobilization via the incorporation of arsenite during the formation of calcium silicates. In the presence of silicic acid, spent Ca-based adsorbents with arsenite had a lower As leaching ratio than those with arsenate. Therefore, spent Ca-based adsorbents with arsenite were found to have a higher environmental stability than those with arsenate.

Pengaruh Penggunaan Ternary Blend Fly Ash Dengan Volume Tinggi dan Abu Sekam Padi Terhadap Kuat Tekan Beton Mutu Tinggi

This study aims to find the effect of ternary blended: cement, fly ash (FA), and rice husk ash (ASP) on the compressive strength of high-strength concrete. The composition of FA and ASP used for cement replacement were 0%, 10% ASP, 30% FA, 10% ASP+30% FA, 10% ASP+40% FA, and 10% ASP+50% FA. The water-cement factor (FAS) and binder used are 0.3 and 500 kg/m3 fresh concrete, respectively. The specimens used for compressive strength is cubes of 100×100×100 mm with tests at the age of 1, 3, 7, 28, and 56 days. The results showed that the use of 10% ASP increased the compressive strength of the concrete compared to the control concrete but required more superplasticizers. The use of 30% FA as a cement substitute showed a decrease in compressive strength compared to control concrete but reduced the use of superplasticizer. The use of a combination of FA and ASP as a substitute for cement showed a decrease in compressive strength under control concrete and concrete using 30% FA. The decrease in the compressive strength of concrete with the combination of ASP and FA is beyond the initial expectation. This may be due to the disproportionate use of FA compared to ASP so that the reaction that occurs is not optimal to form calcium silicate hydrate (CSH). However, the use of ternary blended cement, FA, and ASP still has added values which is better workability than without using FA.

Microstructural analysis of recycled brick aggregate concrete modified by silane

AbstractThere are essential differences between recycled brick aggregate (RBA) and recycled concrete aggregate (RCA). The weak area of RCA is the old mortar attached to the aggregate surface, while the weak area of RBA is its own larger porosity. Silane has a small molecular structure, which can penetrate into the concrete with water as the medium and react with the active functional groups in the concrete to form a network structure of silane polymer. In this paper, 8% silane solution was used to modify recycled brick aggregate concrete (RBAC) in two schemes. The first scheme was that RBA was soaked in 8% silane solution, and the second scheme was that 8% silane solution was added in the mixing process of RBAC instead of water. The results showed that compared with the unmodified RBA, after silane modification of RBA its apparent density increased by 5.48%, water absorption decreased by 61.12%, crushing index decreased by 11.09%. The average compressive strength of RBAC with RBA modified by silane was 11.72% higher than that of unmodified RBAC, and the average compressive strength of RBAC mixed with silane was 9.12% lower than that of unmodified RBAC. The pores and cracks on the surface of RBA were significantly reduced and the interface transition zone (ITZ) of RBA was compacted after silane modification of RBA. RBA contained Si, Fe, Al, Ca elements and a small amount of Na, K, Mg elements brought by mineral powder; the content of Ca, O, Si elements in ITZ and cement mortar were rich, which indicated that there were a large amount of calcium silicate hydrate (C‐S‐H) in ITZ and cement mortar; ITZ and cement mortar contained Al elements, which indicated that there were ettringite and monosulfate; the content of Ca element in RBA and ITZ increased after silane modification of RBA, which indicated that silane hydrolyzed and reacted with free calcium ions to form calcium silicate.

Study on Preparation and Interfacial Transition Zone Microstructure of Red Mud-Yellow Phosphorus Slag-Cement Concrete.

Open stockpiling and the continual production of industrial solid wastes such as red mud (RM) and yellow phosphorus slag (YPS) have caused serious environmental pollution issues. Additionally, concrete prepared easily and with high strength is a widely applied building material. Therefore, replacing part or all of the cement for preparing concrete with RM and YPS will greatly reduce this kind of solid waste and, thus, decrease environmental pressures. This study investigated the best ratio for the replacement of concrete with RM and YPS, testing the mechanical properties as well as the morphology, material composition, and microporous structure of the interface transition zone (ITZ). The results showed for the concrete prepared with ordinary Portland cement replaced by 10.00 wt.% RM and 18 wt.% YPS, compared to ordinary Portland cement concrete, the compressive strength of concrete with basalt aggregate and dolomite aggregate increased by 25.04% and 27.27%, respectively, when the concrete was cured with steam for 28 days. Furthermore, it had a smaller average pore diameter and crystal size in the ITZ. The aggregate and matrix were more closely intertwined. This was because RM had a low cementitious activity and mainly had a filling effect when added to concrete, while the highly active silica in YPS could react with the Ca(OH)2 crystal (CH) produced from cement hydration to form calcium silicate hydrate (CSH) gel, improving the mechanical properties and microstructure of the concrete.

Calcium silicate-human serum albumin composite hydrogel decreases random pattern skin flap necrosis by attenuating vascular endothelial cell apoptosis and inflammation

Random pattern skin flaps are commonly used in plastic surgery to repair skin defects. However, as flap survival mainly relies on blood supply from the distal pedicle and the wound bed, the distal part of the flap is prone to necrosis. Subsequent pathological reactions, including inflammatory reactions, cell apoptosis, and oxidative stress, also aggravate skin flap necrosis. Calcium silicate (CS) has gained attention for its multiple bioactive functions, including promoting angiogenesis and decreasing cell apoptosis, as well as its excellent biocompatibility and safety. Meanwhile, human serum albumin (HSA) hydrogel exhibits excellent drug carrier characteristics and good viscosity for clinical applications. Here, CS was incorporated into HSA hydrogel to form a bioactive composite hydrogel and to control its gelling time. PBS, CS-PBS, HSA hydrogel, and CS-HSA hydrogel were injected under skin flaps on day (-1) and skin flap surgery was performed on day 0. On day 7, the skin flap necrosis rate of the CS-HSA hydrogel group was significantly decreased with increased blood perfusion. Si ions were consistently released from the CS-HSA hydrogel under the skin flap 7 days after operation. Histological staining showed significantly increased CD31+ blood vessels, decreased cell apoptosis, and CD68+ macrophage infiltration. In vitro assays showed that low concentrations of CS extracts sustained cell viability, migration, and tube formation ability of human umbilical vein endothelial cells (HUVECs). CS extracts also decreased HUVEC apoptosis under glucose/oxygen-deprived conditions. Under these conditions, the macrophage inflammatory response decreased. Based on these results, composite CS-HSA hydrogel is suitable for clinical application, and can improve random pattern skin flap survival by attenuating vascular endothelial cell apoptosis and inflammation.