Loss Of Tensile Strength Research Articles

Influence of Weather Conditions and Mechanical Reclamation on Molding Sand with Alkali-Phenolic Binder for Manganese Cast Steel

The article presents the results of research on the properties of molding sands in Alphaset technology (alkaline-phenolic). These sands are often used in steel foundries, producing large castings. However, knowledge about them, and especially about the changeability of their properties with the change of environmental conditions (seasons), is still insufficient. Various compositions of molding sand were analyzed based on fresh chromite sand and reclaimed sand. A binder and hardener in various mass ratios were used to prepare the mass. The research methodology included, among others, tests of tensile and bending strength, permeability, abrasion, gas emissivity, and ignition losses. These tests were carried out for summer and winter conditions. The results showed the optimal proportions of resin and hardener, showed the influence of ambient temperature on the properties of the molding sand, and the possible ratio of reclaimed sand in relation to fresh sand. However, you should always remember to verify them under the conditions of a specific foundry.

Accelerated weathering performance of plantation-grown juvenile poplar and Chinese fir woods

Abstract Plantation-grown juvenile wood species are extensively used as raw materials in the Chinese wood industry. The weathering performances of the wood are crucial for outdoor application. Two of the most important plantation-grown juvenile woods, poplar (Populus × euramericana cv. ‘74/76ʼ) and Chinese fir (Cunninghamia lanceolata Hook), were sliced into thin veneers and compared in this study to observe their weathering performance during exposure to UV alone for 504 h and UV/water for 168 h. The color difference, weight loss, and tensile strength loss of both veneers all increased with exposure time. Scanning electron microscopy showed that the initial structural deterioration originates from the corner of the middle lamella and pit, followed by cell separation, cell wall thinning, deformation, and collapse. Fourier transmission infrared spectroscopy, electron resonance spectrometry and X-ray photoelectron spectroscopy revealed a decrease in lignin-based infrared absorption intensity and radical generation, as well as an increase in O/C ratio throughout the exposure. Water spray considerably accelerated deterioration by washing away the degraded fragments, thereby exposing the fresh substrate underneath. Compared to poplar wood, Chinese fir showed durable structural integrity but more darkening during weathering. These findings reveal the anatomically structural weak phase and photo-degradation performance of two plantation-grown woods during weathering. The results of this work may facilitate the proper external use and further photo-stabilization treatment of plantation-grown juvenile wood products.

Multiscale defects enable synergetic improvement in yield strength of CrCoNi-based medium-entropy alloy fabricated via laser-powder bed fusion

Recently, laser-powder bed fusion (L-PBF) has overcome a shortcoming concerning the relatively modest yield strength in the face-centered cubic structure of CrCoNi medium-entropy alloy (MEA); nevertheless, further enhancement remains challenging because the as-built defects are limited to dislocation cell structures and nano-inclusions. In this study, several the types of hierarchical defect structures are explored (including stacking faults, nano-twins, σ phase, and nano-precipitates) with the addition of Si to reduce the stacking fault energy and promote segregation at dislocation cells with Cr. The CrCoNiSi0.3 alloy is fabricated by the L-PBF process, and the effects of the Si addition and L-PBF processing on the hierarchical multiscale defects and corresponding mechanical responses are unraveled. The highest apparent density above 99.5 % is achieved under optimized conditions, exhibiting a high yield strength of 929 MPa owing to a synergetic effect from the generated defects comprising σ phase, nano-twins, and planar defects with moderate ductility of 14 %. In addition, the reduced stacking fault energy promotes deformation twinning, resulting in steady strain hardening. The alloy ultimately exhibits a tensile strength of 1264 MPa, with a moderate ductility of 14 %. A post-heat treatment induces a morphological change in the σ phase from a film-type at the cell walls to particulates at the cell junctions, leading to a significant increase in ductility without a loss of tensile strength, despite a loss of yield strength. This work provides insights to overcome the pre-existing limitations by imposing and adjusting multiscale defects.

The mechanical properties of GFRP bars embedded in geopolymer concrete after high temperature exposure

Geopolymer concrete prepared with fly ash and slag has exhibited excellent thermostability and thermal insulation performance. Through combining geopolymer concrete with glass fiber reinforced polymer (GFRP) bars, the existing problems like high energy consumption, massive CO2 emission and steel bars corrosion in traditional reinforced concrete structures can be solved. To investigate the mechanical properties of GFRP bars embedded in geopolymer concrete after high temperature exposure, a test was conducted on 419 specimens in this study. Factors that influence the performance include exposure temperature, exposure time and type of concrete cover. The results demonstrated that the tensile properties of bare GFRP bars decreased significantly in the temperature range from 400 °C to 600 °C, and the ratio of tensile strength loss was as high as 50%–90%. The geopolymer concrete cover can effectively slow down and mitigate the degradation in tensile strength and elastic modulus of GFRP bars after high temperature exposure (400–600 °C), but this effect weakens following the rise in exposure temperature and time. In addition, the degradation mechanism of GFRP bars within geopolymer concrete was further analyzed by scanning electron microscopy (SEM) in the microscopic level. Finally, the contribution ratio of each influence factor to the residual tensile strength of GFRP bars after high temperature exposure was numerically illustrated using the statistical method of analysis of variance (ANOVA).

Retaining Mechanical Properties of GMA-Welded Joints of 9%Ni Steel Using Experimentally Produced Matching Ferritic Filler Metal

Motivated by the loss of tensile strength in 9%Ni steel arc-welded joints performed using commercially available Ni-based austenitic filler metals, the viability of retaining tensile strength using an experimentally produced matching ferritic filler metal was confirmed. Compared to the austenitic Ni-based filler metal (685 MPa), higher tensile strength in gas metal arc (GMA) welded joints was achieved using a ferritic filler metal (749 MPa) due to its microstructure being similar to the base metal (645 MPa). The microstructure of hard martensite resulted in an impact energy of 71 J (-196 °C), which was two times higher than the specified minimum value of ≥34 J. The tensile and impact strength of the welded joint is affected not only by its microstructure, but also by the degree of its mechanical mismatch depending on the type of filler metal. Welds with a harder microstructure and less mechanical mismatch are important for achieving an adequate combination of tensile strength and notched impact strength. This is achievable with the cost-effective ferritic filler metal. A more desirable combination of mechanical properties is guaranteed by applying low preheating temperature (200 °C), which is a more practicable and economical solution compared to the high post-weld heat treatment (PWHT) temperature (580 °C) suggested by other research.

The effect of coupling agent on the mechanical properties of injection molded polypropylene/wheat straw composites

The objective of this work is to evaluate the effect of maleic anhydride-grafted polypropylene (MAPP) as coupling agent in polypropylene (PP)-based composites filled with ground wheat straw (WS) particles. The WS and the MAPP content in the composites was 10 wt% and 2 wt%, respectively. The samples were fabricated through melt compounding using a twin-screw extruder and then formed into dumbbell-shaped specimens by injection molding. The mechanical properties of neat PP and the composites with and without coupling were evaluated based on tensile and flexural tests and dynamic mechanical analyses (DMA). The experimental results showed that incorporating WS into the PP reduces its tensile strength by ~3 MPa, while improving its Young’s modulus by 0.14 GPa. The addition of MAPP compensated for the loss in tensile strength without affecting the modulus. Similar observations were made during the flexural tests as well, in which case, however, there was no loss revealed in the strength in the presence of WS due to the different types of load. The results of DMA analyses indicated an improved stiffness of WS-containing samples throughout the whole analyzed temperature range of 20-120 °C as a consequence of reduced chain mobility of PP caused by the stiff straw particles.

Effects of Air Plasma Modification on Aramid Fiber Surface and Its Composite Interface and Mechanical Properties.

In order to improve the interface and mechanical properties of aramid fiber (AF)-reinforced epoxy resin (EP) composites (AF/EPs), the surface modification of AF was carried out with atmospheric pressure air plasma, and the effects of plasma treatment time and discharge power on the AF surface and the interface and mechanical properties of AF/EPs were investigated. The results show that, when plasma treatment time was 10 min and discharge power was 400 W, AF showed the best modification effect. Compared to the unmodified material, the total content of active groups on the surface of AF increased by 82.4%; the contact angle between AF and EP decreased by 20%; the interfacial energy and work of adhesion increased by 77.1% and 19.1%, respectively; the loss of AF monofilament tensile strength was controlled at only 8.6%; and the interlaminar shear strength and tensile strength of AF/EPs increased by 45.5% and 10.4%, respectively. The improvement in AF/EP interfacial and mechanical properties is due to the introduction of more active groups on the AF surface with suitable plasma processing parameters, which strengthens the chemical bonding between the AF and EP matrix. At the same time, plasma treatment effectively increases the surface roughness of AF, and the mechanical meshing effect between the AF and EP matrix is improved. The synergistic effect of chemical bonding and mechanical meshing improves the wettability and interfacial bonding strength between the AF and EP matrix, which enables the load to be transferred from the resin to the fiber more efficiently, thereby improving the mechanical properties of the AF/EP.

Assessing concrete strength loss at elevated temperatures as a function of dielectric variation measured by GPR: an empirical study

ABSTRACT Reinforced concrete (RC) parts, which are exposed to high temperatures for a certain period, undergo physical-chemical changes that deteriorate their mechanical properties. To this end, this study investigates the efficiency of using ground-penetrating radar (GPR) as a non-destructive testing (NDT) method in assessing the core compressive strength loss, elastic modulus decrease, and tensile strength loss of concrete under extreme temperatures. RC specimens are fabricated and exposed to elevated temperatures (300°C, 400°C, 500°C, 600°C, and 700°C). GPR measurements are performed to estimate the relative dielectric permittivity (RDP) of the specimens before fire exposure (BFE) and after fire exposure (AFE). The compressive strengths of the cores extracted from the specimens are obtained also for BFE and AFE cases. Attained RDP values are in conformance with the previous research results and contribute additional evidence to the published literature. As the temperature levels are increased, RDP and strength-related values of concrete specimens decrease. The strength-related parameters are more sensitive to elevated temperatures, whereas the change in the RDP values is rather gradual. Through multiple correlations within 95% confidence intervals, core compressive strength loss, elastic modulus decrease, and tensile strength loss are, individually, estimated as a function of relative RDP change and applied temperature levels. Empirical formulas are obtained with high coefficients of correlation. The relative effects of RDP change and temperature are more pronounced in elastic modulus decrease and tensile strength loss compared to compressive strength loss. Overall, the outcomes of this paper confirm the viability of using the GPR technique for concrete dielectric characterisation in estimating the strength-related properties of concrete exposed to high temperatures, which might reduce the need for destructive testing.

Abstract 15274: Pediatric Valved Conduit From Biological Engineering in the Growing Lamb Model

Introduction: A valved conduit with growth potential for pediatric patients remains an unmet need. Here we present a novel valved conduit with growth potential based on initial data in a growing lamb model. The valve is constructed from three biologically-engineered tubes of acellular collagenous matrix possessing somatic growth potential (Syedain et al., Nat Comms, 2016) using resorbable suture with each tube contributing to create a “leaflet” (Syedain et al, Sci Transl Med, 2021). This tri-tube valve previously demonstrated growth over 52 weeks when implanted interpositionally in the pulmonary artery. Methods: In this study, a fourth tube of the same matrix is placed around the tri-tube valve to create a tubular valved conduit. The inlet segment is cut diagonally to allow for direct attachment to the myocardium, emulating a clinical repair (see figure). Results: The first two lambs to date implanted in this study exhibited normal leaflet function, a pressure gradient less than 5mmHg without regurgitation or dilatation of the conduit at 12-week echocardiography (see figure). During this time the animal’s weight increased from 34±2kg to 48±1kg. The inflow pattern with this myocardial implantation was more uniform than in the previous study that used a pulmonary artery interposition implant of the just the valve (with no conduit). Discussion: Demonstrating integration of the conduit’s matrix to the myocardium is a key step toward a clinical trial. Previous pulmonary interposition implants of the valve, while achieving integration with the adjacent artery prior to dissolution of the Maxon suture (50% loss of tensile strength in ~3 weeks, complete by ~26 weeks), did not establish this clinically relevant point of myocardial integration. Conclusion: The preliminary finding is that the valved conduit exhibits excellent function at 12 weeks in the growing lamb and integration of the conduit’s matrix with the valve annulus-myocardium will likely occur. Funding: R01 HL107572

Leaf litter breakdown along an elevational gradient in Australian alpine streams.

The breakdown of allochthonous organic matter, is a central step in nutrient cycling in stream ecosystems. There is concern that increased temperatures from climate change will alter the breakdown rate of organic matter, with important consequences for the ecosystem functioning of alpine streams. This study investigated the rate of leaf litter breakdown and how temperature and other factors such as microbial and invertebrate activities influenced this over elevational and temporal gradients. Dried leaves of Snow Gum (Eucalyptus pauciflora) and cotton strips were deployed in coarse (6 mm), and fine (50 μm) mesh size bags along an 820 m elevation gradient. Loss of mass in leaf litter and cotton tensile strength per day (k per day), fungal biomass measured as ergosterol concentration, invertebrate colonization of leaf litter, and benthic organic matter (mass and composition) were determined. Both microbial and macroinvertebrate activities were equally important in leaf litter breakdown with the abundance of shredder invertebrate taxa. The overall leaf litter breakdown rate and loss of tensile strength in cotton strips (both k per day) were greater during warmer deployment periods and at lower elevations, with significant positive relationships between mean water temperature and leaf breakdown and loss of tensile strength rate, but no differences between sites, after accounting for the effects of temperature. Despite considerably lower amounts of benthic organic matter in streams above the tree line relative to those below, shredders were present in coarse mesh bags at all sites. Ergosterol concentration was greater on leaves in coarse mesh bags than in fine mesh bags, implying differences in the microbial communities. The importance of water temperatures on the rate of leaf litter breakdown suggests the potential effects of climate change‐induced temperature increases on ecological processes in such streams.

Study of performance of aerostat envelope materials on the coast

In this article, the performance of several naturally aged envelope materials in Hainan, China, was studied. The results show that the outer layer contributes to the properties of the envelope materials, where PVF and PVDF are better candidates for a weathering layer than TPU and aluminum. Due to the superior water and mildew resistance of PVF and PVDF, the loss of tensile strength for 3216LV and FV1175 was slight, whose value reduced from 101.43 ± 5.45 Kgf/cm and 76.15 ± 3.81 Kgf/cm to 79.73 ± 6.40 Kgf/cm and 70.20 ± 6.57 Kgf/cm, respectively, when aging for 24 months with the helium permeability reduction from 0.8818 L/m2•day•atm and 0.6360 L/m2•day•atm to 0.2047 L/m2•day•atm and 0.2169 L/m2•day•atm aging for 18 months, in the case of FV1175 showed leakage after aging for 24 months due to delamination. However, the tensile strength of HV150 dropped from 82.13 ± 3.61 Kgf/cm to 15.22 ± 2.16 Kgf/cm at 24 months with helium leakage, owing to heavy mildew and degradation. Meanwhile, ETAV150 also exhibited a decreased tensile strength of 57.92 ± 1.32 Kgf/cm after 6 months aging, 32.8% lower than that of the original sample, and showed leakage when aging for 12 months. This research provides a theoretical guidance for the structural design and screen of envelope materials for aerostat used along the coast.

Durability of recycled aggregate concrete in cold regions

The combination of experimental programs and finite element numerical methods is adopted to explore the durability of WBC (waste brick concrete). Rapid freeze-thaw and flexural tests are performed with the content of WBCA (waste brick coarse aggregate) and the number of freeze-thaw cycles as variables. Freeze-thaw damage mechanisms at the microscopic interfaces of recycled concrete are revealed by scanning electron microscopy. The evolution laws of relative dynamic elastic modulus, mass loss rate, and flexural and tensile strength loss rate are analyzed. Combined with numerical simulations, the temperature stress distribution and three-point bending damage law of concrete with 100 % WBCA content at different freeze-thaw times are shown, and practical examples are verified. Results showed that WBC with high WBCA content has poor freeze-thaw resistance. Furthermore, WBC's freezing resistance and bending properties deteriorate as the number of freeze-thaw cycles increases. Possible damaged locations in the concrete are determined by stress analysis. The finite element model can predict the flexural performance of WBC better with an error of 4.5 % for the peak load and 3.5 % for the peak displacement of the beam. Therefore, the presented model can also be used to predict the performance of concrete after freezing and thawing under any WBCA replacement rate.

Improving the performance of recycled aggregate concrete using nylon waste fibers

The use of coarse recycled aggregates (CRA) as the replacement for natural aggregates is an eco-friendly solution to alleviate the extraction of natural resources and the harmful effects of demolition wastes on the environment. However, the mechanical and durability characteristics of CRA concrete are generally inferior compared to ordinary concrete. The performance of CRA concrete can be supplemented using different fibers and secondary binder materials. This study encourages the idea of using recycled nylon fiber (RNF) to upgrade the ductility of high-performance concrete (HPC) made with CRA. For this purpose, the effect of RNF on HPC properties was explored. RNF was introduced in HPC at four different volume fractions i.e., 0.1 %, 0.25 %, 0.5 % and 1 %. The experiments showed that RNF is generally harmful to the compressive strength and density of HPC. However, at 0.1 % volume, RNF showed a nominally positive effect on compressive strength. RNF addition was highly useful in enhancing the splitting tensile strength and crack resistance of HPC. The tensile strength loss of HPC due to 50 % and 100 % CRA incorporation can also be balanced using 0.25–0.5 % RNF. Water absorption and chloride permeability of HPC were marginally reduced at the incorporation of 0.1–0.25 % RNF. The recommended dosage of RNF is 0.25 %, considering the maximum tensile strength and low permeability of HPC. Owing to the addition of 0.5 % RNF, a CRA-based HPC can attain tensile strength higher than ordinary HPC. Thus, for tensile-loading applications, CRA-RNF-based HPC provides a ductile, and eco-friendly alternative to an ordinary plain HPC.

A novel quenching-electroshocking-tempering process for toughness improvement by microstructure refining and austenite stability tailoring in aviation bearing steel

In this work, the microstructural evolution and mechanical properties of aviation M50 steel under a novel quenching-electroshocking-tempering (Q-E-T) process were investigated. Microstructural observations indicate that the carbon concentration and volume fraction of retained austenite (RA) in Q-E-T specimens are higher than those in conventional quenching‐tempering (Q‐T) specimens due to the significant carbon partition induced by the introduced electroshocking treatment (EST). Meanwhile, the diameter of packets in the Q-E-T specimens is refined from 1.71 μm to 1.34 μm, which is attributed to the segmentation of blocky as-quenched RA by bainite transformation during EST. The mechanical analysis shows that an excellent combination of ultimate tensile strength and impact toughness is achieved for M50 steel subjected to the Q-E-T process. Compared with the conventional Q-T process, the impact absorbing energy of M50 steel is increased by 24.1% without any loss of tensile strength. Additionally, the thermal and mechanical stabilities of RA in the Q-E-T specimens are both improved. This work provides a novel strategy for improving the impact toughness of M50 by refining the microstructure and appropriately tailoring the stability of RA via an efficient Q-E-T process.

A novel micromechanical model to study the influence of cure process on the in-plane tensile properties of z-pinned laminates

This paper proposes a novel micromechanical model to study the curing effects on the in-plane tensile properties and failure mechanisms of carbon/epoxy laminates reinforced with z-pins. The microstructures including fiber distortion and resin-rich pockets caused by z-pins are characterized. The results indicate that cure-induced residual stresses greatly exist with increasing z-pin density. Thermal expansion and volume shrinkage mismatch between z-pins and resin-rich regions attribute to the high stress concentration. The existence of interfacial stress concentration and resin-rich channels produce a loss of tensile strength and lead to an initial pathway for crack growth under tension. The failure mode changing from the interfacial cracking to softening and damages of both interface and resin-rich regions is also revealed with increasing z-pin density.

Cotton strip assay detects soil microbial degradation differences among crop rotation and tillage experiments on Vertisols

The cotton strip assay (CSA) is a simple and inexpensive method of evaluating management effects on soil microbial decomposition. The average loss of tensile strength of cotton strips buried 3 to 35 days in soils from two long-term tillage and crop-rotation experiments was of the order: cotton-wheat rotation > minimum-tillage cotton monoculture > maximum-tillage cotton monoculture. The study suggests CSA can be an effective indicator to delineate microbial activity, soil organic carbon or crop biomass as influenced by agricultural practices in cotton fields.

Application of marble dust and ground granulated blast-furnace slag in emulsified asphalt warm mixtures

Warm mix asphalt (WMA) has the advantage of lower production temperature as compared to conventional hot mix asphalt (HMA). It is prepared by using various types of technologies which change the properties of bitumen binder attributes to ease in workability of the mixes. In the present study, bitumen emulsion was used for preparing WMA mixes by pre-coating the aggregates. Moreover, the conventional filler used in such mixes was replaced with industrial wastes to further reap environmental benefits. Marble dust (MD) and ground granulated blast-furnace slag (GGBS) are generated abundantly and disposal is a big issue. These were used in varying contents (i.e. from 2% to 8% by the weight of mix) and WMA properties were evaluated for strength and durability. Marshall properties and indirect tensile strength test (ITS) were carried out for strength evaluation. The tensile strength ratio (TSR) was conducted asperAASHTO T 283 for durability analysis. The wheel tracker test was performed for rutting analysis. Cantabro loss was determined to assess the cohesion resistance of the asphalt mixtures. Scanning electron microscopy (SEM) images were used to assess the microscopic characteristics of WMA and its constituents. The results revealed that the inclusion of both MD and GGBS as fillers into WMA had significantly improved the stability, tensile strength, TSR, rutting and Cantabro loss results as compared to the control mix. However, the addition of GGBS filler in emulsified warm mixes showed better resistance to moisture too. Lower rut depth was observed using GGBS as compared to marble dust filler. The statistical analysis reported that there was a significant difference between stability and TSR values whereas for adhesion loss it showed insignificant difference between the GGBS and MD based mixes.

Organic-matter decomposition in urban stream and pond habitats

Organic-matter decomposition is a key ecosystem process in freshwater ecosystems as it influences food web dynamics, represents a considerable flux in the global carbon cycle and can provide a useful measure of the ‘health’ of freshwater habitats. While organic-matter decomposition has been well studied among lotic ecosystems, research from small standing waterbodies such as ponds is largely missing, and decomposition studies are usually conducted on a single freshwater habitat type. However, there is a need to consider ecosystem processes across multiple freshwater habitats and connected ecosystems to better characterise ecosystem functioning at the landscape-scale, given the interdependence of landscape elements. This study provides a comparative analysis of organic-matter decomposition using a standardised field assay (cotton-strip assay) in the water column, riparian zone and land zone of urban pond and stream habitats. The average daily tensile-strength loss of the cotton strips (a process that corresponds to the catabolism of cellulose by microbes) was significantly higher in the aquatic habitats than riparian and land zones when all sites were considered, and when stream and pond sites were considered separately. Furthermore, the average decomposition rate was significantly higher within the water column in river habitats compared to pond habitats, although no difference was observed among riparian and land zones. Woody debris had a negative unimodal association with average per day tensile strength loss within streams, and a positive unimodal association within pond sites. Both nitrate and shading had positive unimodal associations with average per day tensile strength loss within stream sites. Among pond habitat, urban land coverage within 250m of each site was identified to have a negative association with average per day tensile strength loss. Here we demonstrated that urban freshwater habitats have heterogeneous organic matter decomposition rates, and that the responses can be complex. Understanding key ecosystem processes at a multihabitat scale will ensure the effective inclusion of ecosystem process in freshwater assessment and conservation protocols and improve the health and resilience of urban freshwater ecosystems.

Quantitative Assessment of Road Performance of Recycled Asphalt Mixtures Incorporated with Steel Slag.

Circular utilization of reclaimed asphalt pavement (RAP) has received extensive attention for its economic and environmental benefits. The application of recycled asphalt mixtures (RAM) in the upper layer of asphalt pavement faces the issue of inferior anti-slip performance and durability. This study aims to recycle steel slag as virgin aggregates in RAM and quantitatively evaluate the service performance of RAM with steel slag. Steel slag and basalt RAM were firstly fabricated and the five different RAP contents were involved. Then tests of Marshall stability, indirect tensile strength and Cantabro spatter loss were conducted to investigate the moisture susceptibility of RAM. Moreover, their high temperature stability, crack resistance and skid resistance were characterized. Indirect tensile fatigue test combined with Hamburg wheel tracking test were carried out to discuss the durability of RAM. The comprehensive performance of RAM with steel slag were quantitatively assessed based on an improved radar chart evaluation method. The results show that involving steel slag reveals a remarkable enhancement function on water stability, high and low temperature performance, skid resistance and fatigue resistance of RAM. Steel slag RAM with 50% RAP content demonstrates a rutting depth of 7.60 mm and a creep slope of 2.54 × 10−4, indicating its superior durability in high temperature and water environment. Compared with the comprehensive evaluation function of 0.5336 for basalt RAM with 30% RAP dosage, steel slag RAM reaches 0.7801, which represents its preferable road performance.

Tensile properties deterioration of BFRP bars in simulated pore solution and real seawater sea sand concrete environment with varying alkalinities

This study investigates the effectiveness of reducing alkalinity on the durability enhancement of basalt fiber reinforced polymer (BFRP) bars to address their durability in the alkaline environment of seawater sea sand concrete (SWSSC). After accelerated aging at different temperatures and durations, the tensile properties of BFRP bars immersed in simulated SWSSC pore solution and embedded in seawater sea sand mortar (SWSSM) with varying alkalinities were evaluated by tensile testing. In addition, scanning electron microscopy, X-ray micro-computed tomography, and low-field nuclear magnetic resonance were used to examine the microstructure of embedded BFRP bars and SWSSMs. The experimental results indicate that reducing the pH of the solution and SWSSM to around 12 or below can significantly mitigate BFRP bar tensile strength loss. The maximum improvement of tensile strength retention for bare and embedded BFRP bars are 43.52% and 40.27%, respectively. Compared to BFRP bars wrapped in normal SWSSM, the degradation of resin, basalt fiber, and fiber-resin interface of embedded BFRP bars in the low-alkalinity SWSSMs is considerably mitigated due to the reduced alkalinity and porosity. According to the Arrhenius prediction, the tensile strength retention of BFRP bars embedded in normal SWSSM will decrease to 70% within 1.70–5.10 years, but it will be more than 85% for those embedded in low-alkalinity SWSSMs. This study indicates that it is an effective way to mitigate the deterioration of BFRP bars by using low-alkalinity SWSSC when BFRP bars are used as reinforcement in marine SWSSC structures.