Search Results (93)

The paper deals with the concept of how to regulate structure formation in the interfacial transition zone (ITZ) between the Ordinary Portland Cement (OPC) matrix and basalt to ensure the durability of basalt fiber-reinforced concretes. It has been demonstrated that the alkali–silica reaction (ASR) can be transformed from a destructive (negative) process into a constructive one in OPC concrete through activation by sodium water glass combined with the incorporation of an Al₂O₃-containing additive, namely metakaolin. Alkaline activation increased the compressive strength of OPC basalt fiber-reinforced concrete by 1.6–1.9 times. The formation of stable zeolite-like hydration products within the Na₂O-CaO-Al₂O₃-SiO₂-H₂O system promoted self-healing of the ITZ. This resulted in a 5.6-fold increase in ITZ microhardness compared to the cement matrix, as well as transforming expansion into shrinkage of concrete with a final value of 0.01 mm/m after 360 days. The structure-forming processes in the ITZ ensured a 1.14-fold increase in the compressive strength of 180-day alkali-activated OPC basalt fiber-reinforced concrete compared to its 30-day strength, in contrast to a 0.92-fold decrease in the strength of the non-modified OPC analog under conditions accelerating the development of ASR. Full article

Environmental concerns associated with the construction industry have drawn increasing attention worldwide. This study addresses the dual challenges of carbon emissions from cement production and construction waste disposal by developing and characterizing a fiber-modified geopolymer recycled aggregate porous concrete (GRAPC). An orthogonal experiment first optimized the GRAPC mix proportion (slag content = 40%, alkali modulus = 1.4, alkali content = 8%). Subsequently, the effects of coir, basalt, and steel fibers (0.25% and 0.5%) on its properties were investigated through laboratory experiments combined with scanning electron microscopy (SEM) analysis. The results show that steel fibers at 0.25% dosage enhanced compressive strength by approximately 25% due to their effective stress-bearing capacity. In contrast, 0.5% coir and basalt fibers reduced compressive strength by approximately 20.5% and 22.2%, respectively, due to low intrinsic strength and agglomeration. In addition, 0.25% coir and steel fibers increased effective porosity by 18.4% and 17.4%, respectively, owing to their uniform dispersion. All fibers promoted a more ductile-like failure mode, with coir fibers providing the best toughness improvement. This study elucidates how fiber type and dosage regulate the macro-properties and micro-mechanisms of GRAPC, providing a basis for designing sustainable eco-friendly concrete with great potential for non-primary load-bearing engineering fields. Full article

The application of fiber-reinforced polymer bars has been considered an alternative for the non-metallic reinforcement of concrete structures. Basalt fiber-reinforced polymer (BFRP) is a new composite used to reinforce concrete structures. However, the main drawback of BFRP is its low modulus of elasticity. Therefore, hybrid reinforced fiber polymers, in which carbon fibers replace part of the basalt fibers, might be considered as a relatively “simple” modification that can increase the modulus of elasticity. The literature data suggest that modification of the epoxy matrix with nanosilica particles can positively influence resistance to high temperatures. Besides the mechanical characteristics of FRPs, the evaluation of alkali resistance is necessary for technical approval for construction applications. This paper focuses on testing the alkali resistance of basalt fiber-reinforced polymer (BFRP) bars and its modification through the partial substitution of basalt fibers with carbon fibers (HFRP) and the addition of nanosilica to the epoxy binder (nHFRP). The alkali resistance was tested based on the most common method described in ACI report 440.3R-04—part B6. This method consists of three procedures carried out at 60 °C on the specimens immersed in an alkaline solution, both with and without load. The changes in the mass and tensile strength of the bars are examined after 1, 2, 3, 4, and 6 months. The test procedures are time-consuming and expensive, particularly Procedures B (in alkaline solution) and C (in concrete cover), in which longitudinal tested specimens must be immersed in alkaline solution and subjected to constant strain at an elevated temperature for a 6-month period. Therefore, this study proposes a test setup to achieve a less time-consuming and cheaper assessment of the alkali resistance of FRP bars. Additionally, the usefulness of the shear strength test for the evaluation of alkali resistance of FRP bars is also discussed. The results (Procedure A) indicate that modification of the composition of BFRP did not decrease the resistance to the alkaline environment in the case of HFRP (5% lower than in the case of BFRP). Under the same conditions, the decrease in the tensile strength of nHFRP was 40% higher than in the case of BFRP. This indicates that additional modification of the composition by adding nanosilica to the epoxy binder did not provide the expected stability of tensile properties at elevated temperatures. The results of the evaluation of alkali resistance according to Procedure B show that the device proposed for maintaining constant strain during the seasoning is promising. At this stage, the device makes it possible to conduct the tests at ambient temperature and yields a significantly lower decrease in tensile strength (10–14%) after 6 months, demonstrating a significant effect of temperature on the results of the FRP alkali resistance test. Full article

The northern segment of the Great Xing’an Range, northeastern China, hosts a previously unrecognized near-E–W-trending rhyolite belt in the Tulihe area. We conducted systematic geochronological and geochemical investigations to constrain its formation age, petrogenesis, and regional tectonic significance. Field investigation, petrographic observation, and zircon laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) U–Pb dating indicate that the rhyolite belt was formed during the Early Cretaceous, with emplacement ages directly determined from three samples ranging from 143.8 to 131.5 Ma. Geochemically, the rhyolites yielded high SiO₂ contents (74.44–75.88 wt.%), high total alkalis (K₂O + Na₂O = 8.50–8.99 wt.%), and low MgO contents (0.16–0.55 wt.%). They displayed strong enrichment in light rare earth elements and depletion in high field strength elements, weakly negative Eu anomalies, A/CNK ratios near unity, and relatively high Nb/Ta ratios. Trace element signatures and incompatible element abundances (Zr + Nb + Ce + Y = 193.2–338.3 × 10⁻⁶) are mostly consistent with highly fractionated I-type volcanic rocks, rather than S-type or M-type affinities. The geochemical data suggest that the rhyolites were mainly generated by partial melting of a medium- to high-K basaltic lower crust, with minor crustal assimilation and limited mantle input. Tectonically, Early Cretaceous magmatism in the northern Great Xing’an Range was governed by flat-slab subduction and subsequent rollback of the Paleo-Pacific (Izanagi) plate, while the local E–W-trending rhyolite belt was controlled by pre-existing faults, reflecting localized post-orogenic extension consistent with regional NE-trending volcanic belts. The northwest-to-southeast younging trend records asthenospheric upwelling and enhanced crust–mantle interaction induced by slab rollback. These results highlight the petrogenetic and tectonic evolution of medium- to high-K magmatism along the NE Asian continental margin and improve our understanding of Mesozoic volcanism in the Great Xing’an Range. Full article

In the research, the effect of basaltic pumice powder on the mechanical and thermal resistance properties of alkali-activated mortars (AAM) was studied. The class F fly ash, basaltic pumice powder (BPP), and ground granulated blast furnace slag were utilized as sustainable binder materials. The BPP was incorporated instead of fly ash and slag at concentrations of 10, 20, 30, 40, and 50%. In addition, the effects of different sodium hydroxide (NaOH) molarities (8, 12, 16 M) were investigated on the thermal resistance properties. The influence of curing time and its effects on different elevated temperatures (200, 400, and 600 °C) were also studied together at 7, 28, and 56 days on the AAMs. Flexural strength, compressive strength, weight change, and ultrasonic pulse velocity tests were carried out at the macro-scale. The microstructures of the AAM samples were analyzed using SEM and EDX spectroscopy. The results showed that dissolution of basaltic pumice particles requires a longer curing time. The 50% pumice-incorporated 8 M samples at 7 d exhibited the worst, whereas 16 M samples without pumice at 56 d performed the best in terms of mechanical strength and thermal durability. The optimal formulation for the best elevated temperature resistance is the 30% BPP and 16 M NaOH molarity. Full article

In response to escalating environmental concerns, the construction industry is under growing pressure to adopt sustainable practices. As a major consumer of natural resources and a significant emitter of greenhouse gases, it paradoxically holds the potential to become a leader in green transformation. This study investigates the development of innovative, fire-resistant, and alkali-activated hybrid binder foams incorporating recycled materials: fly ash, coal slag, and ground brick waste, as sustainable alternatives to traditional building materials. The fire resistance performance at a technical scale and the thermal behavior of fiber-reinforced, alkali-activated hybrid binder foams synthesized from recycled aluminosilicate precursors were determined. The properties of unreinforced composite were compared with the composites reinforced with merino wool, basalt fibers, polypropylene fibers, and coconut fiber. Small-scale fire-resistance tests revealed that merino wool-reinforced composites exhibited the best thermal insulation performance, maintaining structural integrity, that is, retaining shape and continuity without delamination or collapse for 83 min under fire exposure. Analyses combining chemical characterization (X-ray fluorescence) with microstructural methods (computed tomography and colorimetry) confirmed that fire performance is strongly influenced not only by fiber type but also by pore distribution, phase composition, and oxide migration under thermal loading. These findings demonstrate the potential of fiber-reinforced foamed, alkali-activated hybrid binder as eco-efficient, printable materials for fire-safe and thermally demanding construction applications. Full article

This study investigates the adhesion of polypropylene (PP), steel and basalt fibres to geopolymer matrices of varying composition. Geopolymers formed via alkali activation of fly ash (FA) and ground granulated blast-furnace slag (GGBFS) offer significant environmental advantages over Portland cement by reducing CO₂ emissions and energy consumption. The addition of water treatment sludge (WTS) was also investigated as a partial or complete replacement for FA. Pull-out tests showed that replacing FA with WTS significantly reduces the mechanical properties of the matrix and at the same time the adhesion to the fibres tested. The addition of 20% WTS reduced the compressive strength by more than 50% and full replacement to less than 5% of the reference value. Steel fibres showed the highest adhesion (9.3 MPa), while PP fibres had the lowest, with adhesion values three times lower than steel. Increased GGBFS content improved fibre adhesion, while the addition of WTS weakened it. Calculated critical fibre lengths ranged from 50 to 70 mm in WTS-free matrices but increased significantly in WTS-containing matrices due to reduced matrix strength. The compatibility of the fibres with the geopolymer matrix was also confirmed via SEM microstructural observations, where a homogeneous transition zone was observed in the case of steel fibres, while numerous discontinuities at the interface were observed in the case of other fibres, the surface of which is made of organic polymers. These results highlight the potential of fibre-reinforced geopolymer composites for sustainable construction. Full article

Basalt fiber-reinforced composites are increasingly utilized in sustainable construction due to their high strength, environmental benefits, and durability. However, the long-term tensile performance of these composites in alkaline environments remains a critical concern. This study investigates the degradation performance of basalt fibers exposed to different alkaline solutions (NaOH, KOH, and Ca(OH)₂) with varying concentrations (5 g/L, 15 g/L, and 30 g/L) over various exposure periods (7, 14, and 28 days). The performance assessment is carried out by mechanical properties, including tensile strength and modulus of elasticity, using experimental techniques and Response Surface Methodology (RSM) to find influential factors on tensile performance. The findings indicate that tensile strength degradation is highly dependent on alkali type and concentration, with Ca(OH)₂-treated fibers exhibiting superior mechanical retention (max tensile strength: 938.94 MPa) compared to NaOH-treated samples, which showed the highest degradation rate. Five machine learning (ML) models, including Tree Random Forest (TRF), Function Multilayer Perceptron (FMP), Lazy IBK, Meta Bagging, and Function SMOreg (FSMOreg), were also implemented to predict tensile strength based on exposure parameters. FSMOreg demonstrated the highest prediction accuracy with a correlation coefficient of 0.928 and the lowest error metrics (RMSE 181.94). The analysis boosts basalt fiber durability evaluations in cement-based composites. Full article

Alkali resistance is a critical factor for the long-term performance of glass fibers in cementitious composites. While zirconium oxide doping has proven effective in enhancing the durability of basalt fibers, its high cost and limited solubility motivate the search for viable alternatives. This study presents the first systematic investigation of titanium dioxide (TiO₂) doping in basalt-based glasses across a wide compositional range (0–8 mol%). X-ray fluorescence and diffraction analyses confirm complete dissolution of TiO₂ within the amorphous silicate network, with no phase segregation. At low concentrations (≤3 mol%), Ti⁴⁺ acts as a network modifier in octahedral coordination ([TiO₆]), reducing melt viscosity and lowering processing temperatures. As TiO₂ content increases, titanium in-corporates into tetrahedral sites ([TiO₄]), competing with Fe³⁺ for network-forming positions and displacing it into octahedral coordination, as revealed by Mössbauer spectroscopy. This structural redistribution promotes phase separation and triggers the crystallization of pseudobrukite (Fe₂TiO₅) at elevated temperatures. The formation of a protective Ti(OH)₄ surface layer upon alkali exposure enhances chemical resistance, with optimal performance observed at 4.6 mol% TiO₂—reducing mass loss in NaOH and seawater by 13.3% and 25%, respectively, and improving residual tensile strength. However, higher TiO₂ concentrations (≥5 mol%) lead to pseudobrukite crystallization and a narrowed fiber-forming temperature window, rendering continuous fiber drawing unfeasible. The results demonstrate that TiO₂ is a promising, cost-effective dopant for basalt fibers, but its benefits are constrained by a critical solubility threshold and structural trade-offs between durability and processability. Full article

In-situ lunar construction technology is critical for future lunar base development, and the production of geopolymers from lunar regolith—a novel cementitious material with concrete-like properties—has become a vital approach for achieving in-situ resource utilization. This study systematically investigated the influence of basalt fiber content (0–0.4%) on the mechanical properties of lunar regolith simulant geopolymers by controlling key parameters including curing temperature (20 °C and 80 °C), duration (1 d and 7 d), and alkali activator type (strong alkaline solution: a mixture of sodium hydroxide and sodium silicate, and weak alkaline solution: sodium silicate solution). Through testing of 144 specimens, the results revealed that strong alkali-activated specimens with 0.3% fibers cured at 20 °C for 7 d showed optimal ductility with compressive strength of 2.85 MPa and flexural strength of 0.53 MPa, exhibiting characteristic flat stress-strain curves. Specimens with 0.2% fibers under high-temperature curing at 80 °C for 1 d achieved maximum compressive strength of 44.76 MPa and flexural strength of 1.60 MPa but demonstrated brittle failure behavior. Weak alkali-activated specimens containing 0.1% fibers cured at 80 °C for 7 d attained superior comprehensive performance with peak flexural strength reaching 3.88 MPa, showing excellent fiber-matrix synergy. These findings provide important theoretical foundations for optimizing lunar construction materials through customized fiber reinforcement and curing strategies. Full article

Basalt fiber reinforced polymer (BFRP) has been utilized as a corrosion-resistant substitute for steel rebar in concrete structures. However, embedded BFRP rebars may degrade over time within the alkaline concrete pore solution. While extensive literature has scrutinized BFRP degradation under highly alkaline conditions (e.g., pH~13 in normal concrete), comparatively few studies have addressed its behavior under lower alkalinity (e.g., pH~11–12 in carbonated/green concrete). To address this issue, this study systematically investigates the degradation mechanism of BFRP rebars under coupled factors of pH (7, 11, 12, and 13), temperature (23, 40, and 60 °C), and aging time (30, 60, and 90 days). Research outcomes indicate that a decrease in pH from 13 to 11 at 23 °C results in a reduction in diffusion coefficient from 7.071 × 10⁻⁷ mm²/s to 5.876 × 10⁻⁷ mm²/s. Moreover, lowering the temperature from 60 °C to 23 °C at pH 12 leads to a decline in the diffusion coefficient from 7.547 × 10⁻⁷ mm²/s to 6.758 × 10⁻⁷ mm²/s. Furthermore, following a 90-day immersion at 60 °C, decreasing the exposure pH from 13 to 11 can significantly improve tensile strength retention from 25.357% to 71.933%. In the same scenario, flexural strength retention (or interlaminar shear strength retention) increases from 20.930% to 87.638% (or 23.464% to 76.592%) in such a mildly alkaline environment. A comprehensive degradation mechanism is uncovered, linking macroscopic mechanical properties to microscopic characteristics (encompassing fiber corrosion, matrix cracking, and interfacial debonding). This degradation process can be expedited by alkali attack and thermal activation. These findings contribute valuable insights into the alkali-induced degradation process and furnish a comprehensive dataset regarding the durability performance of BFRP rebars. Full article

This paper focuses on delineating and charactering of the magma crystallization conditions of the post-collision Lavarab Alkaline Basaltic Lavas in East Iran. The lavas consist mainly of alkali basalt and basanite, with subordinate trachybasalt. Olivine mostly shows forsterite, chrysolite and hyalo-siderite compositions. Clinopyroxenes are diopside and augite, belonging to peralkaline to subalkaline magmatic series within post-collisional tectonic settings. Estimates of temperature and pressure obtained from single clinopyroxene thermobarometers suggest that crystallization temperatures vary between approximately 1110 and 1260 °C, with pressures ranging from about 0.05 to 1.35 GPa, which correspond to depths of roughly 2 to 51 km at high oxygen fugacity in both the lower and upper continental crust. Olivine-liquid thermometry yields temperatures of ~1385 to ~1393 °C for basanites and ~1275 to ~1339 °C for alkali basalts, assuming a constant pressure of 1.4 GPa. The chemical compositions of phenocrysts in the studied basaltic lavas provide evidence of magma recharge, occurring through multiple pulses of new magma injected into the existing reservoir prior to eruptions. Petrographic evidence, including absorption features, rounded crystal morphologies, patchy zones in olivine, and sieve textures in clinopyroxene, support this interpretation. Additionally, microprobe analyses reveal oscillatory variations in crystal composition from core to rim, confirming the hypothesis of dynamic magma replenishment. Full article

Basalt-fiber-reinforced polymer (BFRP) composites, utilizing a natural high-performance inorganic fiber, exhibit excellent weathering resistance, including tolerance to high and low temperatures, salt fog, and acid/alkali corrosion. They also possess superior mechanical properties such as high strength and modulus, making them widely applicable in aerospace and shipbuilding. This study experimentally investigated the mechanical properties of BFRP plates under various strain rates (10⁻⁴ s⁻¹ to 10³ s⁻¹) and directions using an electronic universal testing machine and a split Hopkinson pressure bar (SHPB).The results demonstrate significant strain rate dependency and pronounced anisotropy. Based on experimental data, relationships linking the strength of BFRP composites in different directions to strain rate were established. These relationships effectively predict mechanical properties within the tested strain rate range, providing reliable data for numerical simulations and valuable support for structural design and engineering applications. The developed strain rate relationships were successfully validated through finite element simulations of low-velocity impact. Full article

Leveraging the sensitivity of long-period fiber grating (LPFG) to changes in the environmental refractive index, an LPFG-based seawater concentration monitoring sensor is proposed. Considering the highly saltine and alkali characteristics of the sensor’s operating environment, the proposed sensor is packaged by basalt fiber-reinforced polymer (BFRP), and the sensor’s sensitivities were studied by sodium chloride and calcium chloride solution concentration experiments and one real-time sodium chloride solution concentration monitoring experiment. The test results show the wavelength of LPFG, a 3 dB bandwidth and a peak loss of LPFG’s spectrogram change with changes in the concentration of sodium chloride or calcium chloride solutions, but only the wavelength has a good linear relationship with the change in solution concentration, and the sensing coefficient is −0.160 nm/% in the sodium chloride solution and −0.225 nm/% in the calcium chloride solution. The real-time monitoring test further verified the sensor’s sensing performance, with an absolute measurement error of less than 1.8%. The BFRP packaged sensor has good corrosion resistance and a simple structure, and it has a certain application value in the monitoring of salinity in the marine environment and coastal soil. Full article

Due to their low environmental impact, various mineral or cellulose-based natural fibres have recently attracted attention in the construction industry. Hence, the current study focused on basalt fibres and explored the changes in the physical, mechanical, and micro-structural properties of geopolymer concrete reinforced with such fibres. The current study used self-compacting geopolymer concrete, an eco-friendly concrete composed of fly ash, ground granulated blast furnace slag, and an alkali activator, in addition to the regular components of normal concrete. The self-compacting geopolymer concrete compacts under its own weight, so extra compaction is not required. The present study investigated the effect of the fibre content and length. Two different fibre lengths were considered: 12 mm and 30 mm. Three different percentages (1%, 2%, and 3% of the weight of the total mix) of the basalt fibres were considered to determine the optimum fibre content. The mix design was carried out for all the mixes with different fibre contents and fibre lengths, and the workability properties in the slump flow, T-500, and J-ring tests are presented. The effects of the fibre length and content were evaluated in terms of compressive strength (28 and 56 days) and split tensile strength. The results indicated that a higher fibre content effectively increased the compressive strength of 12 mm long fibres. In contrast, a lower fibre content was ideal for the 30 mm long fibres. In addition, the short fibres were more effective in enhancing the geopolymer concrete’s tensile strength than the long fibres. Furthermore, a detailed microscopic analysis was carried out, which revealed that fibre clustering, voids, etc., changed the strength of the selected fibre-reinforced self-compacting geopolymer concrete. Moreover, the analytical method’s predicted tensile strength agreed with the experimental results. Full article