Freeze-thaw Test Research Articles

Effects of zeolite and palm fiber on the weathering resistance and durability characteristic of cement soil

This paper aims to investigate the effects of zeolite and palm fiber on the strength and durability of cement soil. Based on the findings of previous research, optimal proportions of zeolite, palm fiber, and cement, as well as the appropriate curing age, were determined. Subsequently, unconfined compressive strength tests, dry-wet cycle tests, and freeze-thaw tests were conducted, utilizing NaCl and Na2SO4 solutions over the specified curing period. The strength and durability characteristics of the samples were evaluated by assessing mass and strength loss, taking into account the combined effects of NaCl and Na2SO4 solution erosion. The test data also provide a fitting relationship between strength and the number of cycles under the influence of different solutions, thereby offering a basis for theoretical predictions without the need for additional experiments. Finally, the microscopic mechanisms were analyzed using scanning electron microscopy (SEM). The results indicate that the cement soil composite of zeolite and palm fiber, when combined in optimal proportions, exhibits the best durability and minimal loss of strength and mass, irrespective of whether exposed to clean water or salt erosion, as well as during dry-wet or freeze-thaw cycles.

Sulfate attack, freeze-thaw and high-temperature performances by evaluation of colemanite waste as binding material and aggregate in green geopolymer production

To turn the construction industry into a green application phase, alternatively, cementitious source materials have been partially or completely replaced by waste materials and industrial by-products. With this situation, boron minerals and products have a wide usage area and are increasing daily. The most common of the boron minerals is colemanite. In this study, in addition to using blast furnace slag (S) and fly ash (FA) as source materials in geopolymer mortar production, the mechanical and durability performances of geopolymer mortars by evaluating colemanite waste (CW) instead of both source material and aggregate were compared with 10 different series cured at room temperature. Mechanical properties were investigated on the 7th, 28th, and 90th days. For the durability study, a high-temperature test (300, 600, and 900 °C), freeze-thaw test (15 cycles), and sulfate solution attack test (10% magnesium sulfate (MgSO4) and sodium sulfate (Na2SO4)) were performed. Also, SEM, XRD, and TGA-DTA analyses were used to examine the situation before and after the durability tests. Substitution of colemanite waste up to 10% as a source material allowed it to show a strength increase. The highest compressive strength result on the 90th day was 39.06 MPa in the series where it was replaced with 5% fly ash. In the case of using colemanite as an aggregate, results close to the control sample were obtained. In the high temperature and freeze-thaw test, the colemanite waste formed a protective layer and provided better results in the series in which it was replaced by slag and used as an aggregate.

Study on the Mechanical Characteristics and Degradation Response of Unloading Rocks Surrounding Tunnels in Cold Regions

The excavation of the rock mass at the tunnel entrance in regions characterized by high altitudes and elevated stress levels results in the direct exposure of the surrounding rock to atmospheric conditions. This surrounding rock is subjected to the compounded effects of excavation-induced unloading damage and freeze–thaw erosion, which contribute to the degradation of its mechanical properties. Such deterioration has a negative impact on production and construction operations. Following tunnel excavation, the lateral stress exerted by the surrounding rock at the tunnel face is reduced, leading to a predominance of uniaxial compressive stress. As a result, the failure mode and mechanical behavior of the rock exhibit characteristics similar to those observed in uniaxial loading tests conducted in controlled laboratory environments. This study conducts laboratory-based uniaxial loading and unloading tests, as well as freeze–thaw tests, to examine the strength, deformation characteristics, and fracture attributes of unloading sandstone subjected to freeze–thaw erosion. A damage deterioration model for unloading sandstone under uniaxial conditions is developed, and the patterns of damage response are further analyzed through the identification of compaction points and the definition of damage response points. The results indicate that (1) as the degree of freeze–thaw erosion increases, the failure threshold of the sandstone significantly decreases, with the residual rock fragments on the fracture surface transitioning from hard and sharp to soft and sandy; (2) freeze–thaw erosion has a pronounced negative impact on the cohesion of the sandstone, while the reduction in the internal friction angle is relatively moderate; and (3) the strain induced by damage following three, six, and nine freeze–thaw cycles exhibits a gradual decline and appears to reach a state of stabilization when compared to conditions without freeze–thaw exposure. Investigating the mechanical properties and deterioration mechanisms of the rock in this specific context is crucial for establishing a theoretical foundation to assess the stability of the tunnel’s surrounding rock and determine the necessary support measures.

Experimental Investigation of Durability Properties of Polymer Coated Pumice Aggregate Lightweight Concretes.

Pumice aggregates with low density and high porosity are widely used in lightweight concrete. The high water retention ability of pumice aggregates adversely affects the properties of fresh concrete. Additionally, pumice aggregates' inadequate mechanical strength and durability hinder concrete performance. In recent years, research on coated aggregates has gained traction to improve the physical properties, mechanical strength, and durability characteristics of concrete. In this study, coarse pumice aggregates were coated with polyester and partially substituted with uncoated aggregates at ratios of 0%, 25%, 50%, 75%, and 100% in lightweight concrete formulations. Specific weight and water absorption tests were performed on the aggregates, while slump and unit weight tests were performed on fresh concrete mixtures. SEM-EDX analyses, unit weight, water absorbing capacity, sorptivity, compressive strength, freeze-thaw resistance, and sulfate resistance tests were performed on concrete specimens. The results indicated that the polyester coating significantly increased the specific weight of the aggregates and decreased the water absorption rates by up to 85%. Despite the coated aggregates resulting in decreased compressive strength of concrete specimens, they demonstrated reduced water absorbing capacity and sorptivity characteristics relative to reference concrete. Moreover, concrete made with coated aggregates exhibited better results in freeze-thaw and sulphate resistance tests.

Effect of Water Immersion and Freeze-Thaw Cycles on Pull-off Strength of FRP Epoxy Bonded on Concrete: An experimental study

The durability and performance of Fiber Reinforced Polymer (FRP) composites for strengthening reinforced concrete structures under various environmental conditions are critical for their long-term efficacy. This study investigates the effects of water immersion and freeze-thaw cycles on the pull-off strength of epoxy-bonded FRP concrete slabs, simulating conditions typical for waterfront structures such as piles, beams, and decks. Concrete slabs, fabricated to EN 1766 standards, were reinforced with Basalt (BFRP), Glass (GFRP), and Carbon Fiber Reinforced Polymer (CFRP) sheets using Duratek® AV21 epoxy resin. The samples were conditioned in a controlled laboratory environment (23±2°C, 50±5% RH) for 24 hours before being subjected to water immersion and freeze-thaw cycling tests. Pull-off tests, conducted per EN 1542, revealed cohesive failures in the concrete substrate. The average pull-off strength for the control samples was 3.26 N/mm² for concrete and 3.97 N/mm² for epoxy resin. Water immersion results showed a slight decrease in pull-off strength for CFRP and GFRP, by 9% and 2% respectively, while BFRP exhibited a 14% increase. Freeze-thaw cycling led to increased pull-off strength across all FRP types: 7% for GFRP, 7.3% for BFRP, and 3.75% for CFRP. The findings indicate that water immersion and freeze-thaw conditions have a marginal impact on the pull-off strength of FRP-reinforced concrete. Despite the environmental exposure, all test results remained above the required pull-off strength of 2.5 MPa, demonstrating the robustness of the FRP-concrete bond. The study supports the use of FRP composites for structural reinforcement in harsh environments, highlighting their resilience under adverse conditions. Further research is recommended to explore long-term performance and additional environmental factors to ensure comprehensive durability assessments of FRP-reinforced systems.

Influence of Different Mixing Methods for Cementitious Capillary Crystalline Waterproofing Materials on the Self-Healing Capacity of Concrete Under Various Damage Types.

Cementitious Capillary Crystallization Waterproofing Material (CCCW), as an efficient self-healing agent, can effectively repair damage in concrete structures, thereby extending their service life. To address the various types of damage encountered in practical engineering applications, this study investigates the impact of different mixing methods for CCCW (including internal mixing, curing, and post-crack repair) on the multi-dimensional self-healing performance of concrete. The self-healing capacity of concrete was evaluated through water pressure damage self-healing tests, freeze-thaw damage self-healing tests, mechanical load damage self-healing tests, and crack damage self-healing tests. The results show that the curing-type CCCW mixing method exhibited the best self-healing effect in repairing water pressure, freeze-thaw, and load damages, with corresponding healing rates of 88.9%, 92.7%, and 90.5%, respectively. The internally mixed CCCW method was also effective for repairing load damage in concrete, while the repair-type CCCW mixing method demonstrated the weakest repair effect on these types of damage. For concrete with induced pre-existing cracks, the internally mixed CCCW method, after 28 days of water-immersion curing, exhibited a significantly higher crack self-healing ability, with a self-healing ratio of 333.8%. Optical microscopy observations revealed that the crack surfaces were almost fully sealed, with a substantial deposition of white crystalline material at the crack sites. Further analysis using scanning electron microscopy (SEM) and X-ray Diffraction (XRD) provided insights into the surface morphology and phase characteristics of the self-healed cracks, indicating that calcium carbonate (CaCO3) and calcium silicate hydrate (C-S-H) were the main products responsible for crack healing.

Investigation of Chloride Salt Erosion on Asphalt Binders and Mixtures: Performance Evaluation and Correlation Analysis.

Asphalt pavement, widely utilized in transportation infrastructure due to its favourable properties, faces significant degradation from chloride salt erosion in coastal areas and winter deicing regions. In this study, two commonly used asphalt binders, 70# base asphalt and SBS (Styrene-Butadiene-Styrene)-modified asphalt, were utilized to study the chloride salt erosion effect on asphalt pavement by immersing materials in laboratory-prepared chloride salt solutions. The conventional properties and adhesion of asphalt were assessed using penetration, softening point, ductility, and pull-off tests, while Fourier transform infrared spectroscopy (FTIR) elucidated the erosion mechanism. The Marshall stability test, freeze-thaw splitting test, and Cantabro test were applied to study the effects of chloride exposure on the strength, water stability, and structural integrity of the asphalt mixture. Finally, the grey correlation analysis was employed to assess the impact of chloride salt erosion on the performance of asphalt binders and mixtures. The findings highlight that chloride salt erosion reduces penetration and ductility in both types of asphalt binders, raises the softening point, and weakens asphalt-aggregate adhesion, confirmed as a primarily physical effect by FTIR analysis. Asphalt mixtures showed decreased strength and water stability, intensifying these impacts at higher chloride concentrations and longer erosion duration. SBS-modified asphalt binders and mixtures exhibited greater resistance to chloride salt erosion, particularly in adhesion, as demonstrated by the Cantabro and pull-out tests. Grey relational analysis revealed that erosion duration is the most influential factor, with TSR and softening point emerging as the most responsive indicators of chloride-induced changes. These findings offer critical insights for practice, providing evidence-based guidance for designing and constructing asphalt pavements in environments with high chloride levels.

Turmeric-black pepper-honey nanoemulsion formulation and antiulcerogenic effect evaluation against ethanol-induced gastric ulcers in rats.

Gastric ulcer is a common disorder of the digestive system. The combination of turmeric and honey is known to treat stomach ulcers. However, curcumin, an active component in turmeric, has limitations, i.e., poor water solubility and low oral bioavailability. Therefore, turmeric and honey were formulated into a nanoemulsion with black pepper to enhance curcumin bioavailability. The study followed a systematic approach to optimize the nanoemulsion formula, determine stability, and evaluate ulcer healing activity in rats with ethanol-induced gastric ulcers. Nanoemulsion was prepared using a low-energy emulsification method called emulsion phase inversion (EPI). Two stability evaluations were carried out, i.e., storage and freeze-thaw stability tests. The organoleptic, droplet size, polydispersity index, pH, viscosity, and curcumin content of the nanoemulsion were evaluated. Male Wistar albino rats were induced with 96% ethanol for six days. The rats were divided into six groups, i.e., healthy control, ulcerated control, omeprazole, two different doses of turmeric, honey, and black pepper nanoemulsion (NTBH1 and NTBH2), and turmeric and honey nanoemulsion (NTH). The antiulcer activity was determined by measuring the ulcer area, ulcer index, curative index, ulcer severity score, and histology. The best formula with the smallest droplet size, i.e., 144.6±3.8 nm, was obtained from the nanoemulsion using Tween 80 as surfactant, glycerin as cosolvent, and sodium alginate as viscosity enhancer. The result showed that the nanoemulsion was stable after being stored at 25 and 40°C for four weeks and after six cycles of freeze-thaw test. The ulcer index of the ulcerated rats from the lowest to the highest, i.e., NTBH2, omeprazole, NTH, and NTBH1. In conclusion, the nanoemulsion developed in this study containing turmeric, honey, and black pepper holds promising potential in treating gastric ulcers, offering a hopeful outlook for future treatments.

Mechanical properties of polypropylene fiber reinforced concrete short columns under freeze-thaw cycles

To investigate the effect of polypropylene fibers on the mechanical properties of concrete structures in cold regions, obtain an appropriate amount of polypropylene fiber content, and improve the frost resistance of the structure, freeze-thaw cycle tests were conducted on three groups of reinforced concrete short column specimens with different polypropylene fiber contents. The depth of surface damage of the specimen was detected using ultrasonic method. The stress process and failure of the specimen were analyzed through axial compression test, and the corresponding changes in compressive toughness were discussed. A formula for calculating the axial compressive bearing capacity of polypropylene fiber reinforced concrete short columns after freeze-thaw cycles was established. The test results indicate that the addition of polypropylene fibers can reduce the compressive bearing capacity of reinforced concrete short columns. An appropriate amount of polypropylene fiber can enhance the frost resistance, ductility and toughness of concrete components, and the recommended volume fraction of polypropylene fiber is 0.08–0.12%.

Preliminary safety and in vivo efficacy of Acmella oleracea extract‐loaded glycolipid emulsion serum—Effects on ocular irritation, dermal absorption, and facial skin biophysical and microrelief properties

AbstractObjectiveSubstantial efforts have been progressively devoted to developing innovative, safe, and effective topical anti‐aging products that not only improve the appearance of aged skin but also prioritize environmental sustainability and the responsible use of natural resources. Thus, the current study targeted to evaluate novel, natural emulsion/serum comprising new glycolipid emulsifier (lauryl glucoside/myristyl glucoside/polyglyceryl‐6 laurate) and Acmella oleracea plant extract as a model active.MethodsThe developed serum was assessed concerning its stability (freeze–thaw test, accelerated study), safety (in vitro screening of eye irritation potential, dermal absorption study) and efficacy (randomized, active/reference‐controlled, half‐face, in vivo study). Changes in skin biophysical properties, microrelief, roughness, texture, surface, and volume parameters were assessed in the periocular and perioral areas of human volunteers after 2 weeks of product application, utilizing several bioengineering and topography techniques.ResultsThe stability study demonstrated favourable stability profile of the developed serum, with practically unaffected stability‐indicating parameters (apparent viscosity, yield, flow point, storage and loss moduli, loss factor, pH, electrical conductivity) during freeze–thaw cycling and after 3 months of storage at 45°C. The hen's egg test on the chorioallantoic membrane of fertilized chicken eggs confirmed the absence of ocular irritation potential of investigated serum; no effects of haemorrhage, lysis or coagulation were occurred. Skin permeation study using diffusion cells revealed no permeation of spilanthol from the tested A. oleracea extract‐loaded serum through the pig ear skin into the receptor medium, thus suggesting no absorption into systemic circulation. In vivo efficacy study corroborated beneficial effects of evaluated serum on the condition/appearance of facial skin, at both periocular and perioral areas—significant (p < 0.05) increase in skin hydration (10%–40%) and smoothness (~15%); significant (p < 0.05) decrease in roughness (20%–30%), scaliness (~30%), and wrinkles (~15%)—implying more hydrated, smoother, visibly milder skin.ConclusionThe present findings confirmed the stability, preliminary safety (no ocular irritation, no dermal absorption, and good skin tolerability), and efficacy (improved skin hydration and microrelief) of the A. oleracea extract‐loaded, glycolipid‐based serum, supporting its potential as a safe and effective topical anti‐aging product.

Phytochemical composition and antimicrobial potential of Stevia rebaudiana Bertoni extract and its topical spray formulation against animal skin pathogens.

The rise of antimicrobial resistance in veterinary medicine is a significant concern, particularly for pathogens responsible for skin infections. Although Stevia rebaudiana Bertoni (stevia) has demonstrated effective antimicrobial properties, there is limited research on its efficacy against animal skin pathogens. This study aimed to identify natural compounds in stevia extract, develop a topical spray formulation, and assess its effectiveness against six common bacterial and fungal pathogens associated with animal skin infections. The aerial parts of stevia plants were extracted using hexane in a Soxhlet apparatus. Total phenolic and flavonoid contents were quantified using colorimetric assays. The volatile oil content was analyzed using gas chromatography-mass spectrometry (GC-MS). The antimicrobial activity of stevia extract against Staphylococcus pseudintermedius, Malassezia pachydermatis, Microsporum canis, Microsporum gypseum, Microsporum gallinae, and Trichophyton mentagrophytes was evaluated using broth microdilution and time-kill tests. Environmental scanning electron microscopy (E-SEM) and leakage studies were conducted to assess the extract's impact on microbial morphology and cell membrane integrity. The antimicrobial efficacy and stability of a topical spray formulation containing stevia extract were evaluated using time-kill and freeze-thaw testing. The stevia extract yield was 3.59% of the dry plant weight with 259.96 ± 23.66 mg gallic acid equivalent (GAE)/g extract of total phenolics and 247.41 ± 19.92 mg quercetin equivalent (QE)/g extract of total flavonoids. GC-MS analysis identified major volatile components, including N-acetyl-14, 15, 16-trinorlabd-8(17)-en-13-amine (37.70% of peak area), phytol (11.02% of peak area), (-)-spathulenol (9.46% of peak area), n-hexadecanoic acid (8.01% of peak area), and (diphenylphosphinoyloxymethyl) dimethylsilane (7.59% of peak area). The minimum inhibitory concentration of the extract against the tested microorganisms ranged from 0.25 to 128.00 mg/mL. Time-kill kinetics exhibited time- and concentration-dependent germicidal effects. E-SEM and cell leakage analyses indicated that stevia extract compromised microbial cell membrane integrity. A spray formulation containing 10% w/w stevia extract displayed excellent eradication efficacy, achieving a 99.9999% reduction of S. pseudintermedius and a 99.999% reduction of M. pachydermatis and dermatophytes, with good stability after six freeze-thaw cycles. Stevia extract is an effective antimicrobial against S. pseudintermedius, M. pachydermatis, Mi. canis, Mi. gypseum, Mi. gallinae, and T. mentagrophytes in vitro. Future research will investigate the pharmaceutical properties and toxicity profiles of purified compounds and determine appropriate dosages and clinical efficacy.

Freeze-thaw resistance and deterioration mechanism of alkali-activated filling grouts prepared from full industrial solid wastes for tunnels

To promote the application of the proposed alkali-activated grout (AAG) prepared from full solid wastes in cold-zone tunnel projects located at high altitudes and latitudes, it is imperative to fully recognise its endurance to the repeated freezing and thawing in specific service scenarios. For this purpose, two groups of representative AAG were selected as subjects for this study, and a typical OPC-based grout was chosen as the control group. Freeze-thaw cycle tests were carried out on grout samples after 28 days of standard curing using the slow-freeze method to simulate the harsh service environment in cold regions. The deterioration impact of freeze-thaw cycling on the grout samples were evaluated by monitoring the changes in visual appearance, mass loss, mechanical strength, and damage coefficient after 20, 40, 60 and 80 freeze-thaw cycles. Furthermore, the deterioration mechanism of various grout samples under the action of freeze-thaw cycling was revealed by multi-technique characterization methods including X-ray diffraction (XRD), scanning electron microscope (SEM), and mercury intrusion porosimetry (MIP). The results show that at the same number of freeze-thaw cycles, the surface deterioration, mass loss and strength damage of AAG were obviously better than that of the OPC-based grout, suggesting that AAG exhibited greater resistance to freezing and thawing than the OPC-based grout. The mass loss ratio increased with the increase of the number of freeze-thaw cycles, following a roughly power function pattern. The deterioration in the flexural strength of grout samples caused by freeze-thaw cycles was more severe than the deterioration in their compressive strength. The gel products of AAG were mainly C-A-S-H and N-A-S-H, which showed stronger resistance to freeze-thaw damage than the gel products of the OPC-based grout, C-S-H and portlandite. Compared with the OPC-based grout, AAG samples possessed a denser microstructure with lower porosity and a smaller proportion of large-sized harmful pores, which was not favourable for the pore water holding and migration of during freeze-thaw cycling and the development of osmotic and frost heave stresses, thus providing better resistance to freezing and thawing. A variety of macroscopic characterisations and microstructural tests have demonstrated the good durability of AAG against the freeze-thaw cycles, which can serve as a scientific foundation for its future engineering uses.

Study on the physical mechanical properties and freeze-thaw resistance of energy storage concrete with artificial phase change aggregate

As the main material for major infrastructure in cold regions, the mechanical properties and freeze-thaw resistance of concrete have become key scientific issues affecting the safety and normal operation and maintenance of infrastructure in cold regions. Energy storage concrete with phase change materials (PCM) has high thermal storage performance, which is beneficial to improving the frost resistance of concrete. In our preliminary research work, the artificial phase change aggregate (APCA) containing PCM with high latent heat, good mechanical properties and frost resistance were made and tested. The APCA was added to the concrete and replaced with natural coarse aggregate in different proportions, resulting in several energy storage concrete schemes with different APCA contents. The water absorption characteristics, microstructure and pore characteristics of energy storage concrete with different APCA contents were tested and analyzed through negative pressure saturation test, SEM and MIP. The effects of APCA replacement on the composition, mechanical properties, failure morphology characteristics and frost resistance durability of energy storage concrete at various ages were analyzed through XRD test, strength test and freeze-thaw cycle test. The results showed that replacing natural coarse aggregates with APCA changed the pore characteristics of concrete, reduced its saturation water absorption rate, but did not change the composition of hydration products at various ages of concrete. Replacing with an appropriate amount of APCA in concrete is beneficial for reducing the total porosity, the number of more-harmful pores and harmful pores. APCA reduce the compressive strength and splitting tensile strength of energy storage concrete at various ages. The early splitting strength of energy storage concrete increases rapidly, while the later growth is relatively slow. APCA are beneficial for suppressing the expansion of pores and cracks under freeze-thaw action of concrete. APCA is helpful to improve the freeze–thaw resistance of the energy storage concrete. After 100 freeze-thaw cycles, their strength is still 96% of the 28 day strength, and their compressive strength is about 35 MPa. This study provides a reliable experimental and theoretical basis for improving the freezing resistance of concrete in cold area.

Use of Wheat Fiber and Nanobentonite to Stabilize Clay Subgrades

Since clayey soils naturally present low mechanical strength, they pose direct challenges for engineering applications. Finding appropriate soil stabilizers to address the challenges posed by clayey soils is crucial for ensuring that the soil meets the necessary geotechnical requirements and fulfills economic and environmental issues. To this end, this research uses several stabilizers and techniques in clayey soils to improve their suitability for construction. The main objective of this study is to assess the use of wheat fiber and nanobentonite (NB) in soil stabilization, estimate their behavior in practices, outline their obstacles and potential for soil improvement, and consider their ecological and financial effects. This research also evaluates the behavior of the soil by incorporating NB (0.4, 0.8, and 1.2%) as a stabilizing agent. For this purpose, the randomly dispersed wheat fibers as a reinforcing agent at different dosages and lengths (0.3, 0.6, 0.9%, and 5, 10, and 15 mm) were combined to the soil matrix. The soil was characterized by conducting compaction, unconfined compressive strength (UCS), direct shear (DS), California bearing ratio (CBR), indirect tensile strength (ITS), freezing-thawing (F-T) tests, and microstructural analysis. The data were used to assess the effect of wheat fiber and NB on the soil’s geotechnical properties. The results revealed that incorporating 0.8% NB into the soil led to the best enhancement in compressive strength. This improvement is attributed to the dehydration and formation of a viscous-like film between the soil particles. In addition, 0.6% fibers with a length of 15mm increased the interaction and bonding forces between the particles of soil, resulting in a maximum increase in compressive strength. Combining fibers and NB improved the shear strength, tensile strength, and bearing capacity. Besides, the stabilized soil exhibited superior resistance to freezing-thawing cycles compared to the unreinforced clay. Overall, the results indicate that using wheat fibers and NB is a cost-effective and eco-friendly solution for stabilizing clay subgrades.

Experimental investigation on freeze–thaw resistance of thermally activated recycled fine powder concrete

Recycled fine powder (RFP) is a new auxiliary cementitious material with potential activation. However, prior to its applications in concrete, its durability should be examined. This study focuses on RFP as the study subject. Through the freeze–thaw test of concrete, indexes such as the appearance change, mass and relative dynamic elastic modulus loss, microstructure, and pore and bubble structures are analyzed. The freeze–thaw model is used to predicate the service life of concrete under freeze–thaw cycles. The effect of a high RFP dosage on the freeze–thaw resistance of concrete before and after thermal activation is comprehensively examined. Results show that the appearance damage increases gradually when the RFP content is more than 15 %. For RFP dosages of 45 % and 60 %, thermally activated RFP concrete exhibits better freeze–thaw resistance than inactivated RFP concrete, and the maximum number of freeze–thaw cycles that thermally activated RFP can withstand is greater than that for inactivated RFP concrete. The mass loss and relative dynamic elastic modulus loss of thermally activated RFP concrete at 60 % dosage are lower than those of inactivated RFP concrete. Microscopic analysis shows that the most probable pore size, the proportion of harmful pores and more-harmful harmful pores of the thermally activation of RFP concrete is smaller than that of the inactivated RFP concrete when the dosages are 45 % and 60 %. Under the SEM image of dosage 60 %, the gels of the thermally activation of RFP concrete are more dense. These results indicate that the thermally activation of RFP tends to refine the pore structure and improve the pore distribution. Furthermore, the average radius and spacing of bubbles are smaller when the dosage of activated RFP is 60 %, thereby improving the freeze–thaw resistance of concrete. In this study, the freeze–thaw model used in this paper that can effectively describe the freeze-thaw change and predict the service life of RFP concrete. When the RFP dosage is 60 %, the lifespan of thermally activated RFP concrete is 2.4–3 times longer than that of inactivated RFP concrete, meeting the needs for structural designs in the central and southern regions of China for 50 years. The research results provide a theoretical basis for RFP resource utilization and the determination of the actual service life of RFP concrete.

Carboxymethyl Chitosan as a Reversible Template of Calcium Phosphate for Multifunctional Conservation of Carbonate Stone.

The accelerated deterioration of carbonate stone artifacts under climate change has long been an urgent issue. Inspired by biomineralization, we developed carboxymethyl chitosan-diammonium hydrogen phosphate (CD) composite and investigated the conservation effectiveness of the CD composite compared to diammonium hydrogen phosphate (DAP) on limestone. The morphologies and microstructures were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FT-IR). The consolidating effectiveness was investigated through a compressive strength test. The protective ability was assessed by disintegration resistance test, acid attack resistance test, salt attack resistance test, and freeze-thaw aging cycle test. SEM observations revealed that carboxymethyl chitosan (CMCS) served as an effective template, inducing the in situ formation of a uniform and continuous calcium phosphate coating on both the surface and interior of the stone. The tests indicated that the CD composite further enhanced the consolidating effectiveness and improved resistance to disintegration and freeze-thaw cycles. Notably, as an amphiphilic polyelectrolyte, CMCS functioned as a pH buffer and a protective barrier against sodium sulfate salts, which improved the resistance to acid and salt attacks. Additionally, the CD composite did not cause significant variations in the esthetic appearance or water vapor permeability. We then applied the CD composite at an actual carbonate stone cultural heritage site, successfully demonstrating the feasibility of CD application and the reversibility of CMCS in a real-world setting. Based on the study's results, our approach provides a new perspective for developing multifunctional and sustainable conservation materials for carbonate stone artifacts.

Study on Frost Resistance of Recycled Rubber Straw Concrete Using Particle Swarm Optimization Enhanced Artificial Neural Networks.

Rubber particles and straw powder were used to prepare recycled rubber straw concrete, and the freeze-thaw test was conducted on the recycled rubber straw concrete using the quick-freezing method. The frost resistance of the recycled rubber straw concrete was evaluated by determining the relative dynamic modulus of elasticity, the rate of mass loss, and the flexural strength of the recycled rubber straw concrete in the process of freezing and thawing. SEM was used to observe the microstructure of the recycled rubber straw concrete after the freezing and thawing process. SEM observed the microstructure of recycled rubber straw concrete after freezing and thawing. The effect and mechanism of rubber admixture and straw admixture on the frost resistance of concrete were investigated by microanalysis. Based on the experimental data, the particle swarm algorithm and genetic algorithm were used to optimize the BP neural network to establish the prediction model of recycled rubber straw powder, and the results show that the PSO-BP neural network prediction model established in this paper has good accuracy and stability. It has a good prediction effect on the flexural strength and the number of freeze-thaw cycles of recycled rubber straw concrete under different mixing ratios.

Mixture proportion optimization and durability evaluation of rejuvenating composite seal

Composite seal (CS) is effective in restoring pavement surface function and prolonging the service life, employing a double-layer structure composed of micro-surfacing and chip seal. Rejuvenating composite seal (RCS) applying rejuvenating agents to the chip seal is dedicated to revitalizing the aged asphalt of the original pavement surface. However, limited studies have focused on enhancing interlayer and temperature performance through optimizing mixture ratios. In this study, a modified emulsified asphalt with self-developed rejuvenating agent was applied, and the orthogonal test considering interlayer shear resistance and high temperature stability was conducted for initially mixture proportion of RCS, then the preliminary ratio was optimized. The proportion for micro-surfacing was determined by mixing test, wet track abrasion test, and loaded wheel sticking sand test. Simultaneously, the recommended asphalt spraying amount of rejuvenating chip seal was determined by utilizing accelerated loading abrasion test. In view of the abrasion resistance, interlayer adhesion, and cracking resistance, the coupled effects of aggregate size and paving rate of rejuvenating chip seal were studied. Long-term wet track abrasion test, freeze-thaw cycle test, and UV aging test were conducted to evaluate the durability. The results show that the asphalt-aggregate ratio of micro-surfacing is 7.1 %. For 4.75 mm or 7 mm rejuvenating chip seal, the recommended asphalt spraying amount is 1.5 kg/m2 or 1.6 kg/m2, and the range of paving rate is 60 %–70 %. For 9.5 mm or 13.2 mm rejuvenating chip seal, the results are 1.7 kg/m2 or 1.8 kg/m2, and 80 %–90 %, respectively. Under the conditions, RCS has better interlayer shear resistance and temperature performance, which can improve durability.

Evaluation of SMA-13 Asphalt Mixture Reinforced by Different Types of Fiber Additives.

This research aims at systematically evaluating the properties of SMA-13 asphalt mixture reinforced by several fiber additives including flocculent lignin fiber (FLF), granular lignin fiber (GLF), chopped basalt fiber (CBF), and flocculent basalt fiber (FBF). Firstly, the thermal stability, moisture absorption, and oil absorption property of these fiber additives were analyzed. Secondly, the property of SMA-13 reinforced using four types of single fibers and two kinds of composite fibers (FLF + CBF and FLF + FBF) was comprehensively analyzed. Specifically, the high-temperature performance was evaluated using the uniaxial penetration test and the rutting test, the medium-temperature anticracking property was evaluated using the IDEAL-CT test, the low-temperature property was analyzed using the beam bending test, and the water stability was studied by the freeze-thaw splitting test. Thirdly, the dynamic mechanical response of different-fibers-modified SMA-13 was evaluated using the uniaxial compression dynamic modulus test. Finally, correlation analysis between the results of dynamic modulus and the high-, medium-, and low-temperature mechanical performance was carried out. The research results reveal that the stability of CBF and FBF under thermal action is better than that of GLF and FLF, and FBF shows the best thermal stability. The oil absorption property of FLF is better than that of GLF, followed by FBF and CBF. The comprehensive mechanical properties of CBF- and FBF-reinforced SMA-13 are better than those of FLF- and GLF-modified SMA-13. CBF can better reinforce the mechanical property of SMA-13 under low and medium temperature, while FBF can better reinforce the performance of SMA-13 at high temperature. FLF/CBF- and FLF/FBF-composite-modified SMA-13 show better high-temperature mechanical performance than that of the single-fiber-reinforced mixture, and FLF has some negative impact on the properties of FLF/FBF-composite-modified SMA-13 at low temperature. Fibers have no significant influence on the water stability of the mixtures. Meanwhile, the linear correlation between the mechanical performance of all the fiber-reinforced SMA-13 and the dynamic modulus result is good.

Influence of Basalt Fiber Morphology on the Properties of Asphalt Binders and Mixtures.

Basalt fiber (BF) has been proven to be an effective additive for improving the properties of asphalt mixtures. However, the influence of basalt fiber morphology on the properties of asphalt binders and mixtures remains inadequately explored. In this study, chopped basalt fiber (CBF) and flocculent basalt fiber (FBF) were selected to make samples for testing the influence of the two types of basalt fibers on asphalt materials. Fluorescence microscopy was used to obtain the dispersion of fiber in asphalt binders. Then, a temperature sweep test and a multiple stress creep recovery (MSCR) test were carried out to appraise the rheological characteristics of the binder. Moreover, the performance of the fiber-reinforced asphalt mixture was evaluated by a wheel tracking test, a uniaxial penetration test, an indirect tensile asphalt cracking test (IDEAL-CT), a low-temperature bending test, a water-immersion stability test, and a freeze-thaw splitting test. The results indicate that the rheological behavior of asphalt binders could be enhanced by both types of fibers. Notably, FBFs exhibit a larger contact area with asphalt mortar compared to CBFs, resulting in improved resistance to deformation under identical shear conditions. Meanwhile, the performance of the asphalt mixture underwent different levels of enhancement with the incorporation of two morphologies of basalt fiber. Specifically, as for the road property indices with FBFs, the enhancement extent of DS in the wheel tracking test, that of RT in the uniaxial penetration test, that of the CTindex in the IDEAL-CT test, and that of εB in the low-temperature trabecular bending test was 3.1%, 6.8%, 15.1%, and 6.5%, respectively, when compared to the CBF-reinforced mixtures. Compared with CBFs, FBFs significantly enhanced the elasticity and deformation recovery ability of asphalt mixtures, demonstrating greater resistance to high-temperature deformation and a more pronounced effect in delaying the onset of middle- and low-temperature cracking. Additionally, the volume of the air void for asphalt mixtures containing FBFs was lower than that containing CBFs, thereby reducing the likelihood of water damage due to excessive voids. Consequently, the moisture susceptibility enhancement of CBFs to asphalt mixture was not obvious, while FBFs could improve moisture susceptibility by more than 20%. Overall, the impact of basalt fibers with different morphologies on the properties of asphalt pavement materials varies significantly, and the research results may provide reference values for the choice of engineering fibers.