Freeze-thaw Research Articles

Research on the Durability of Modified Crumb Rubber Asphalt Mixtures in High-Altitude and Seasonally Frozen Regions

Asphalt pavements in high-altitude and seasonally frozen regions of China encounter significant challenges that impact their stability and durability. This study aims to evaluate the performance of modified crumb rubber (MCR) asphalt mixtures under typical conditions of high-altitude seasonal frozen regions, specifically focusing on the effects of ultraviolet (UV) exposure and freeze–thaw cycling. Laboratory tests were designed to simulate UV irradiation and freeze–thaw cycling on asphalt mixtures, and then a series of tests were conducted on the pre-treated asphalt mixture specimens to investigate the effects on the performance including cohesion, high-temperature stability, low-temperature cracking resistance, water stability, and fatigue resistance. The MCR asphalt mixtures were tested in comparison to the Styrene–Butadiene–Styrene (SBS) modified asphalt and conventional crumb rubber modified asphalt mixtures. The test results indicated that MCR-modified asphalt mixture exhibited better cohesion and water stability than other tested mixtures. Under UV aging conditions, it showed a relatively slow performance degradation rate due to its unique composition that mitigates stress sensitivity. Also, when subjected to freeze–thaw cycling, the incorporation of MCR particles in the asphalt mixture resulted in delayed micro-crack propagation and a self-healing effect, thus mitigating its performance degradation rate compared to the other mixtures. The findings suggest that MCR MCR-modified asphalt mixture is a promising alternative for improving the durability of pavement in high-altitude and seasonally frozen regions.

Early Effects of Bronchoscopic Cryotherapy in Metastatic Non-Small Cell Lung Cancer Patients Receiving Immunotherapy: A Single-Center Prospective Study

Background/Objectives: Cryotherapy is used for local tissue destruction through rapid freeze–thaw cycles. It induces cancer cell necrosis followed by inflammation in the treated tumor microenvironment, and it stimulates systemic adaptive immunity. Combining cryotherapy with immunotherapy may provide a sustained immune response by preventing T cell exhaustion. Methods: Fifty-five patients with metastatic non-small cell lung cancer who had received no prior treatment were randomized into two groups in a 1:1 ratio: the bronchoscopic cryotherapy group or the control group. Patients received up to four cycles of pembrolizumab as monotherapy or in combination with platinum-based chemotherapy. Immune-related adverse events (irAEs), complications, tumor size changes, overall response rate (ORR), and disease control rate (DCR) were evaluated. Results: Lung tumors, treated with cryotherapy, demonstrated continuous reduction from the baseline (22.4 cm2 vs. 14.4 cm2 vs. 10.2 cm2, p < 0.001). Similar changes were observed in pulmonary tumors in the control group (19.0 cm2 vs. 10.0 cm2, p < 0.001). The median change in pulmonary tumors between two groups was not significant (−42.9% vs. −27.7%, p = 0.175). No significant differences were observed in the ORR (28.6% vs. 23.1%, p = 0.461) or target lesion decrease (−24.0% vs. −23.4%, p = 0.296) between the groups. However, the DCR was significantly higher in the cryotherapy group (95.2% vs. 73.1%, p = 0.049). No cases of serious bleeding during cryotherapy or pneumothorax were observed. Six patients (25.0%) in the cryotherapy group and eight (26.7%) in the control group experienced irAEs. Conclusions: Our study demonstrated that combined bronchoscopic cryotherapy and immunotherapy with or without chemotherapy may reduce the rate of progressive disease in metastatic non-small cell lung cancer patients while maintaining a satisfactory safety profile.

Effect of Liquid Nitrogen Freezing on Maintaining the Quality of Crayfish During Freeze–Thaw Cycles: Muscle Structure and Myofibrillar Proteins Properties

The quality of frozen crayfish (Procambarus clarkii) is challenged by freeze–thaw (FT) cycles during storage. The effect of freezing methods on the quality of crayfish during FT cycles was investigated by comparing physicochemical properties, microstructure, and myofibrillar protein (MPs) properties. Three methods were used for crayfish freezing, including air convective freezing (AF) at −20 °C and −50 °C, as well as liquid nitrogen freezing (LNF) at −80 °C. The frozen crayfish were thawed at 4 °C after 45 d of frozen storage as 1 FT cycle. After 5 FT cycles, the water holding capacity of LNF crayfish (70.8%) was significantly (p < 0.05) higher than that of −20 °C AF crayfish (60.6%) and −50 °C AF crayfish (63.5%). The drip loss of LNF crayfish (7.83%) was significantly lower than that of AF crayfish. Moreover, LNF maintained the gel strength and the thermal stability of MPs from crayfish with higher gel storage modulus and enthalpy. These results demonstrated that LNF minimized the formation of large ice crystals, preserving the structural integrity of muscle and the properties of MPs, thereby maintaining crayfish quality. This study investigated the effect of LNF in preserving crayfish quality during FT cycles, providing valuable insights for reducing the quality degradation of aquatic products during storage and transportation.

Integrated computational assessment of concrete properties, durability, and environmental impacts

Due to the vast landscape of low carbon concretes that have been or can be developed, traditional empirical methods are impractical for comprehensive assessment of concrete performance. Here, we describe Panoramix 1.0, a Python-based tool that can predict physical and chemical properties of hydrated cements, and durability and environmental impacts of concretes. Applying it to CEM I concrete as a case study, we investigate the cement composition effects on the freeze–thaw resistance indicator (time to critical saturation degree, tCR). Results indicate that chemical composition of raw materials including Fe2O3 may influence freeze–thaw resistance, which is usually not considered in the current scheme of durability assessment. The results also show how the design space (i.e., feasible cement compositions) could be found for different types of concrete at specified minimum freeze–thaw resistance. We validate Panoramix by comparing its ranking of 28 concrete samples in terms of freeze–thaw performance (tCR) with experimental data for relative dynamic modulus of elasticity (RDME) reported in ten publications and measured using procedures from four different standards. By combining the composition-freeze–thaw resistance modelling with a life cycle assessment model, we show that the climate change impact (100-year global warming potential) per m3 CEM I concrete can be reduced from 313 to 286 kg CO2-eq. by decreasing the clinker-to-cement ratio while reducing tCR from 7 to 5.5 years.

Effect of Time and Temperature on the Detection of PRRSV RNA and Endogenous Internal Sample Control in Porcine Tongue Fluids

Population-based sampling has improved pathogen monitoring in the US swine industry by increasing sensitivity while reducing costs. Postmortem tongue fluids (TF) have emerged as a practical option for monitoring porcine reproductive and respiratory syndrome virus (PRRSV) in breeding herds, but limited data exist on optimal storage conditions. This study evaluated PRRSV RNA detection via RT-qPCR in TF samples under various storage times, temperatures, and viral loads. Additionally, the porcine endogenous reference gene (internal sample control, ISC) was assessed for monitoring sample quality. Three studies were conducted: Study 1 compared fresh TF samples to freeze–thaw TF samples, with significantly lower cycle threshold (Ct) values in fresh samples. Studies 2 and 3 evaluated PRRSV RNA stability across six time points (0 to 336 h) and four temperatures (−20 °C, 4 °C, 22 °C, and 34 °C). At 4 °C, Ct value variation was minimal (≤1.1) over 14 days (336 h), with no significant changes within 48 h. In contrast, storage at 22 °C and 34 °C resulted in increased Ct values. The ISC RNA showed similar stability patterns, maintaining quality at 4 °C but degrading at higher temperatures. In conclusion, storing TF at ≤4 °C for up to 14 days for PRRSV and ISC RNA detection is the best scenario, ensuring optimal diagnostic quality.

Optimization of Mechanical Properties and Durability of Steel Fiber-Reinforced Concrete by Nano CaCO3 and Nano TiC to Improve Material Sustainability

To meet the growing demand for sustainable building materials in modern construction projects, nanomaterials are widely used in concrete to improve its mechanical properties, durability, and environmental adaptability. The effects of different calcium carbonate nanoparticles (NC) and titanium carbide nanoparticles (NT) substitution rates (0%, 0.5%, 1% and 1.5%) on the mechanical and durability properties of steel fiber-reinforced concrete (SFRC) were analyzed by experimental studies. We also analyzed the evolution of the microstructure, chemical composition, and the evolution of functional groups of concrete by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The results demonstrated that NC replacement of 0.5% and NT replacement of 1% was the optimal combination for the preparation of composite concrete. Compared to SFRC with 0% substitution for both NC and NT (CG), the 28-day compressive strength of NC0.5NT1 increased by 35.5%, the flexural strength increased by 26.5%, and the splitting tensile strength increased by 16.3%. The durability performance of SFRC has been significantly improved. After 150 freeze–thaw cycles, the quality loss rate of SFRC cured for 28 days decreased by 40.6%, and the relative dynamic elastic modulus increased by 7.7%. Microscopic analysis indicates that an appropriate amount of NC and NT replacing cement improves the hydration reaction process of SFRC, increases the content of chemically more stable C-S-H gel, but does not change the types of hydration products of the cement. NC and NT have a filling effect, improving the pore structure of concrete, which helps enhance the mechanical and durability performance of concrete. The results of the study provide a theoretical basis for the application of NC and NT as reinforcing particles for cementitious materials in sustainable building materials.

Quantification of Myocardial Biomarkers in Sudden Cardiac Deaths Using a Rapid Immunofluorescence Method for Simultaneous Biomarker Analysis

Background/Objectives: Differential diagnosis of sudden cardiac death (SCD) remains challenging, particularly in cases lacking evident structural abnormalities. Cardiac markers have been proposed as useful tools for this differentiation in forensic contexts. However, key issues include the influence of postmortem interval (PMI) on marker stability and the limitations of traditional approaches that focus on pericardial fluid, which requires invasive sampling compared to peripheral blood. This study aimed to evaluate the potential of cardiac markers in peripheral blood for diagnosing SCD, addressing methodological concerns related to PMI, hemolysis, and sample handling. Methods: This study analyzed 5 cardiac markers (creatine kinase-MB [CK-MB], myoglobin, troponin I [TnI], BNP, and D-dimer) in peripheral blood samples from 42 autopsied cadavers, divided into an SCD group and a control group. Marker levels were quantified using immunofluorescence, with cases meticulously selected to exclude confounding factors such as chronic diseases, pulmonary thromboembolism, and drowning. The study also accounted for potential degradation due to PMI, and evaluated the accuracy of point-of-care testing (POCT) in forensic samples. Results: The study identified statistically significant differences in myoglobin and TnI levels between the SCD group and the control group, though myoglobin’s diagnostic reliability remains limited due to its lack of specificity for myocardial injury. TnI emerged as a more robust marker for SCD. Contrary to prior concerns, PMI showed no significant correlation with marker levels in samples handled without freeze–thaw cycles. Issues related to hemolysis were addressed, and no significant effects were observed from resuscitation maneuvers. Conclusions: This study supports the potential use of cardiac markers, particularly TnI, in peripheral blood for postmortem SCD diagnosis, emphasizing the importance of rapid and systematic analysis to minimize hemolysis-related variability. While further validation is needed to confirm these findings, this approach offers a less invasive, economical, and practical method for forensic investigations.

Study on the Improvement Effect of Polypropylene Fiber on the Mechanical Properties and Freeze–Thaw Degradation Performance of High Fly Ash Content Alkali-Activated Fly Ash Slag Concrete

This article systematically investigated the improvement effect of polypropylene fiber (PPF) on the mechanical and freeze–thaw properties of alkali-activated fly ash slag concrete (AAFSC) with high fly ash content and cured at room temperature. Fly ash and slag were used as precursors, with fly ash accounting for 80% of the total mass. A mixed solution of sodium hydroxide and sodium silicate was used as alkali activator, and short-cut PPF was added to improve the performance of AAFSC. Firstly, the strength characteristics of AAFSC at different curing ages were studied. Then, key indicators such as morphology, residual compressive strength, weight loss, relative dynamic modulus of elasticity (RDME), and pore characteristics of AAFSC after different freeze–thaw cycles were tested and analyzed. The strength performance analysis showed that the optimal dosage of PPF was 0.90%. When the alkali equivalent of the alkali activator was increased from 4% to 6%, the frost resistance of AAFSC could be improved. Furthermore, adding 0.90% PPF could increase the freeze–thaw cycle number of AAFSC by about 50 times (measured by RDME). With the increase in freeze–thaw cycles, the porosity of AAFSC increased, the fractal dimension decreased, and the proportion of harmless and less harmful pores decreased, while the proportion of harmful and multiple harmful pores increased. The relationship model between the porosity and compressive strength of AAFSC after freeze–thaw cycles was established.

Improving the Long-Term Mechanical Properties of Thermoplastic Short Natural Fiber Compounds by Using Alternative Matrices

Wood plastic composites (WPCs) offer a means to reduce the carbon footprint by incorporating natural fibers to enhance the mechanical properties. However, there is limited information on the mechanical properties of these materials under hostile conditions. This study evaluated composites of polypropylene (PP), polystyrene (PS), and polylactic acid (PLA) processed via extrusion and injection molding. Tests were conducted on tensile and flexural strength and modulus, heat deflection temperature (HDT), and creep analysis under varying relative humidity conditions (10% and 90%) and water immersion, followed by freeze—thaw cycles. The addition of fibers generally improved the mechanical properties but increased water absorption. HDT and creep were dependent on the crystallinity of the composites. PLA and PS demonstrated a superior overall performance, except for their impact properties, where PP was slightly better than PLA.

Modification Mechanism and Performance of High-Content Polyurethane-Modified Asphalt

To explore the influence of the polyurethane blending ratio on the micro-characteristics of polyurethane-modified asphalt, three samples of the modified asphalt with different blending ratios (40%, 50%, and 60%) were prepared. Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and scanning electron microscopy (SEM) were employed to elucidate the modification mechanism of polyurethane-modified asphalt. To investigate how the preparation method affects the performance of polyurethane-modified asphalt mixtures, two different preparation methods, namely internal blending and external blending, were adopted. The road performance of the polyurethane-modified asphalt mixtures was evaluated through the utilization of rutting tests, low-temperature trabecular bending tests, and freeze–thaw splitting tests. The FTIR test results indicate that during the modification of polyurethane, there is a change in both the intensity and position of the absorption peak, which affects the local arrangement of the molecular structure. Upon reaching a polyurethane blending ratio of 50%, a cross-linked network structure that is similar to polyurethane is formed. The results of the AFM test demonstrate that an increase in polyurethane content results in a corresponding increase in surface roughness. At a polyurethane content of 50%, the curing reaction is most effective, which is beneficial for enhancing the bonding performance between the asphalt and the aggregate, thereby enhancing the overall water stability of the mixture. The results of the scanning electron microscopy (SEM) tests indicate that the microstructure is more stable when the polyurethane content is 50%. The results of the performance test of the polyurethane-modified asphalt mixture indicate that the dynamic stability of the polyurethane-modified asphalt mixture is approximately four times that of the SBS-modified asphalt mixture. The flexural tensile strength and maximum flexural strain of the polyurethane-modified asphalt mixture are, respectively, 1.5 and 3.2 times those of the SBS-modified asphalt mixture, indicating that its anti-deformation ability is stronger in a low-temperature environment, and it is found that the low-temperature performance of the mixture prepared with the internal blending method is better than that with the external blending method. The splitting strength of the polyurethane asphalt mixture before and after freezing and thawing is greater than that of an SBS asphalt mixture: before freezing and thawing, by about 3.8 times; after freezing and thawing, by about 3 times. Although the freezing and thawing of the polyurethane mixture has damage, it still meets the requirements of the use of pavement materials. It can be observed that the incorporation of polyurethane alters the internal structure of the asphalt, which markedly enhances the properties of the asphalt mixture and offers a novel perspective on the development of modified asphalt materials.

Biocomposite Polyvinyl Alcohol/Ferritin Hydrogels with Enhanced Stretchability and Conductivity for Flexible Strain Sensors

Protein-based hydrogels with stretchability and conductivity have potential applications in wearable electronic devices. However, the development of protein-based biocomposite hydrogels is still limited. In this work, we used natural ferritin to develop a PVA/ferritin biocomposite hydrogel by a repetitive freeze–thaw method. In this biocomposite hydrogel, ferritin, as a nano spring, forms a hydrogen bond with the PVA networks, which reduces the crystallinity of PVA and significantly improves the stretchability of the hydrogel. The fracture strain of the PVA/ferritin hydrogel is 203%, and the fracture stress is 112.2 kPa. The fracture toughness of the PVA/ferritin hydrogel is significantly enhanced to 147.03 kJ/m3, more than 3 times that of the PVA hydrogel (39.17 kJ/m3). In addition, the free residues and iron ions of ferritin endow the biocomposite hydrogel with enhanced ionic conductivity (0.15 S/m). The strain sensor constructed from this hydrogel shows good sensitivity (gauge factor = 1.7 at 150% strain), accurate real-time resistance response, and good long cyclic working stability when used for joint motion monitoring. The results indicate that a PVA/ferritin biocomposite hydrogel prepared by a facile method has enhanced stretchability and conductivity for flexible strain sensors. This work develops a new method for the preparation of protein-based hydrogels for wearable electronic devices.

Study on influencing factors and prediction model of strength and compression index of sandy silt on bank under freeze–thaw cycles

The Inner Mongolia section of the Yellow River is a seasonal frozen soil area, where the freeze–thaw effect can alter soil strength and compressibility, affecting bank stability. This study takes the banks sandy silt of the Inner Mongolia section of the Yellow River as the research object. It systematically investigates the relationship between shear strength parameters and compression index of sandy silt and the initial dry density, water content, and freeze–thaw cycles of the soil. It analyzes the order and significance of influencing factors, establishes prediction models of shear strength and compression index, and evaluates the effects of freeze–thaw cycles on soil cohesion and shear strength. The results show that the shear strength index of sandy silt is proportional to changes in initial dry density and inversely proportional to changes in water content. After 10 freeze–thaw cycles, the cohesion of the soil decreases by 22.53 to 58.85%, and the shear strength decreases by 22.67 to 58.91%. The internal friction angle is less affected by freeze–thaw and tends to be stable overall. The smaller the initial dry density and the greater the water content, the greater the compression index and compressibility of the soil, but freeze–thaw has little effect on compression index. The factors affecting sandy silt shear strength and compression index are ranked as dry density > moisture content > freeze–thaw cycles. The stepwise regression model of soil shear strength and compression index based on initial dry density, water content, and freeze–thaw cycles is effective, providing technical guidance for engineering practice.

Biochar Amendment as a Mitigation Against Freezing–Thawing Effects on Soil Hydraulic Properties

Seasonal freeze–thaw cycles compromise soil structure, thereby increasing hydraulic conductivity but diminishing water retention capacity—both of which are essential for sustaining crop health and nutrient retention in agricultural soils. Prior research has suggested that biochar may alleviate these detrimental effects; however; further investigation into its influence on soil hydraulic properties through freeze–thaw cycles is essential. This study explores the impact of freeze–thaw cycles on the soil water retention and hydraulic conductivity and evaluates the potential of peanut shell biochar to mitigate these effects. Peanut shell biochar was used, and its effects on soil water retention and unsaturated hydraulic conductivity were evaluated through evaporation tests. The findings indicate that freeze–thaw cycles predominantly affect clay’s ability to retain water and control hydraulic conductivity by generating macropores and fissures; with a notable increase in conductivity at high matric potentials. The impact lessens as matric potential decreases below −30 kPa, resulting in smaller differences in conductivity. Introducing biochar helps mitigate these effects by converting large pores into smaller micro- or meso-pores, effectively increasing water retention, especially at higher content of biochar. While biochar’s impact is more pronounced at higher matric potentials, it also significantly reduces conductivity at lower potentials. The total porosity of the soil increased under low biochar application rates (0% and 1%) but declined at higher application rates (2% and 3%) as the number of freeze–thaw cycles increased. Furthermore, the characteristics of soil deformation during freeze–thaw cycles shifted from frost heaving to thaw settlement with increasing biochar application rates. Notably, an optimal biochar application rate was observed to mitigate soil deformation induced by freeze–thaw processes. These findings contribute to the scientific understanding necessary for the development and management of sustainable agricultural soil systems.

Effects of arginine and lysine on quality of shrimp during freeze–thaw cycles

Effects of arginine and lysine on quality of shrimp during freeze–thaw cycles

Environment friendly pesticide formulation by adding certain adjuvants and their biological performance against Sitophilus oryzae (L.)

Formulation and adjuvant technologies can facilitate the use of insecticides that have higher biological efficiency application features. Safety, physicochemical properties by increasing consumer demand for safe food and enhancing operator safety. The aim of this current work was to develop a green efficient, and stable pesticide formulation. Therefore, certain nano emulsions with and without Adjuvants Calcium Alkyl Benzene Sulphonate (Atlox 4838B), and non-ionic surfactant based on trisiloxane ethoxylate (ARGAL), were testing against Sitophilus oryzae (Coleoptera: Curculionidae). Certain analytical techniques were used for determining the characterization of the nano emulsions (Sesame, Clove, and Cinnamon). Results showed that all formulations were penal, achieving nanometric size for all compounds. Scanning Electron Microscopy (SEM) micrographs revealed spherical or quasi-spherical morphologies for the tested nanoemulsion formulation nanodroplets. Furthermore, dynamic light scattering (DLS) showed that the particle size of the formulation with the adjuvants showed a slight increase in the droplet size compared to the formulations without adjuvants. In comparison to the tested nanoemulsions with adjuvants, the viscosity of the nanoemulsions without adjuvants was lower. All studied formulations, both with and without adjuvant, showed an acidic to slightly acidic pH, except for sesame (NE) with AtloxTM 4838B, which showed a neutral pH, and they were kinetically stable with no phase separation, creaming, or crystallization. Furthermore, supporting the stability of these nanoemulsion particles was the absence of a separation phase following centrifugation, freeze–thaw cycles, and heating–cooling cycles. Findings proved that ARGAL and Atlox 4838B adjuvant stabilized NE by increasing Brownian motion, weakening the attractive forces with smaller droplets, increasing the value of zeta potential and polydispersive index (< 0.6), and decreasing surface tension. The bioassay technique using film residue to estimate LC50 values on S. oryzae adults indicate that Clove, Sesame, and Cinnamon nano emulsions with Atolx adjuvants were the most effective against S. oryzae adults under laboratory conditions, where the LC50 Values are 0.022, 0.032 and 0.035 µL/cm2 respectively after 27 h, or exposure time. Clove, Cinnamon, and Sesame nanoemulsion (NE) with 0.01% (w/w) adjuvant exhibited remarkable insecticidal activity against S. oryzae L., of 100, 100 and 97.5% respectively by in vitro assay.

Macro–Micro Properties of Remodeled Waste Slurry Under Freeze–Thaw Cycles

Waste slurry, a major by-product of urban construction, is produced in rapidly increasing volumes each year. Dehydrated waste slurry has potential as a roadbed material; however, its performance in freeze–thaw environments, which can induce frost heave and thaw settlement, and the mechanism of the influence of freeze–thaw cycles on its macro and micro properties are still unclear and need thorough investigation. This study explores the macroscopic and microscopic properties of waste slurry subjected to freeze–thaw cycles. We conducted unconfined compressive strength (UCS) and triaxial unconsolidated undrained (UU) shear tests, focusing on fissure compaction, elastic deformation, plastic yielding, and strain hardening stages. The results reveal a decrease in strength and elastic modulus with increasing freeze–thaw cycles, as well as in the damage degree generated by freeze–thaw cycles. To uncover the underlying microscopic mechanisms, we performed Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), and mercury intrusion porosimetry (MIP) analyses. These tests highlighted the evolution of pores and microcracks during freeze–thaw cycles. These results have important reference values for the reutilization of waste slurry discharged from large-diameter bored piles for roadbed backfill materials that need to be repaired quickly in seasonally frozen areas.

A New Capillary and Adsorption‒Force Model Predicting Hydraulic Conductivity of Soil During Freeze‒thaw Processes

A New Capillary and Adsorption‒Force Model Predicting Hydraulic Conductivity of Soil During Freeze‒thaw Processes

Transport of heat, water, and salts in freeze–thaw soils under flood irrigation: Experiment and simulation

Transport of heat, water, and salts in freeze–thaw soils under flood irrigation: Experiment and simulation

Early strength and durability of tannery sludge/metakaolin based geopolymer as concrete pavement repair material

Approaches to synthesising rapid geopolymer repair materials made from tannery sludge (TS) and metakaolin (MK) were explored to investigate the treatment and utilisation of TS. The setting time and 1-day compressive strength were taken as indicators for evaluating the performance of the TS/MK geopolymer as a repair material. The effects of the silica/alumina molar ratio (A), sodium oxide/silica molar ratio (B), water/cement (w/c) ratio (C) and TS content (D) were determined, and the durability of the geopolymer was also studied. The optimum formula (A = 2.58, B = 0.33, C = 0.67 and D = 10%) met the requirements for a pavement repair material. The final setting time of the optimum formula was 102 min, the 1-day compressive strength was 21.0 MPa and the chromium leaching concentration was 7.52 mg/l. The geopolymer also exhibited good resistance to high temperatures, acid rain and freeze–thaw processes. A geopolymer repair material that exhibited high early strength and stable performance at later stages was thus synthesised. Microstructure was examined using X-ray diffraction, Fourier transform infrared spectroscopy, mercury intrusion porosimetry and scanning electron microscopy, and it was found that a decrease in geopolymer gelation and increases in the pore size and porosity resulted in a decrease in the properties of the repair material.

Evaluating of ground surface freeze–thaw and the interrelationship with vegetation cover on the Qinghai-Xizang Plateau

Evaluating of ground surface freeze–thaw and the interrelationship with vegetation cover on the Qinghai-Xizang Plateau