Freeze-thaw Damage Research Articles

Automated estimation of cementitious sorptivity via computer vision.

Monitoring water uptake in cementitious systems is crucial to assess their durability against corrosion, salt attack, and freeze-thaw damage. However, gauging absorption currently relies on labor-intensive and infrequent weight measurements, as outlined in ASTM C1585. To address this issue, we introduce a custom computer vision model trained on 6234 images, consisting of 4000 real and 2234 synthetic, that automatically detects the water level in prismatic samples absorbing water. This model provides accurate and frequent estimations of water penetration values every minute. After training the model on 1440 unique data points, including 15 paste mixtures with varying water-to-cement ratios from 0.4 to 0.8 and curing periods of 1 to 7 days, we can now predict initial and secondary sorptivities in real time with high confidence, achieving R² > 0.9. Finally, we demonstrate its application on mortar and concrete systems, opening a pathway toward low-cost and automated durability assessment of construction materials.

Research on mechanical properties and pore structure evolution process of steam cured high strength concrete under freeze thaw cycles.

With the widespread use of high-strength concrete structures (HC), the impact of pore structure on their performance has become a current research focus. The mechanism by which different curing conditions and freeze-thaw cycles influence the evolution of pore structure remains unclear. Therefore, this study systematically investigated the frost resistance of high-strength concrete under different curing conditions, measured the mass loss rate, compressive strength, and relative dynamic elastic modulus of concrete under freeze-thaw cycles. Utilizing low-field nuclear magnetic resonance (NMR) technology, this study analyzed the evolution of pore structure in HC under freeze-thaw cycles. Additionally, the fractal dimension was used to evaluate the change of concrete internal pore structure, so as to reflect the influence of pore structure on the mechanical properties of concrete subjected to freeze-thaw cycles, and then evaluated the freeze-thaw damage of HC. The experimental results indicated that the steam curing regimes led to an increase in the porosity of HC, thereby influencing its frost resistance. Steam-cured high-strength concrete (SMHC) exhibited a higher degradation rate under freeze-thaw cycles, resulting in a greater level of deterioration compared to standard curing high-strength concrete (SDHC), even under the same number of freeze-thaw cycles.

Study on chloride ion penetration performance of recycled composite micro powder concrete under freeze-thaw environment

With the increasing generation of construction waste, the rational utilization of recycled micro powder has become crucial for the efficient development of construction waste resource recycling. This study investigates the chloride ion penetration performance of Recycled Composite Micro Powder Concrete (RCMPC) under freeze-thaw conditions. By incorporating Recycled Concrete Powder (RCP) and Recycled Brick Powder (RBP) in a ratio of 2:8 to replace various proportions of cement, specimens with different water-to-binder ratios (0.35, 0.45, 0.55) were designed and subjected to freeze-thaw cycles (FTC), pore structure analysis, rapid chloride ion migration, and diffusion tests. The results indicate that the frost resistance of the concrete decreases with the addition of Recycled Composite Micro Powder (RCMP). As the RCMP content increases, the mass loss rate and relative dynamic modulus decline, while the thickness of the damage layer increases. Moreover, the chloride ion migration coefficient and diffusion coefficient exhibit a linear increase with the number of FTC, with specimens containing higher RCMP content showing poorer chloride ion penetration performance. Based on the experimental results, this paper establishes a chloride ion diffusion model for RCMPC considering freeze-thaw damage, which demonstrates good predictive capability for the chloride ion diffusion behavior of RCMPC in freeze-thaw environments, providing a theoretical basis for its application in cold and marine regions.

Geographical variability in hygrothermal simulation results of historical building envelopes with interior insulation in Belgium

Thermal retrofits of existing buildings offer a great potential to reduce Europe’s energy use and CO2 emissions. The impact of these retrofitting strategies on the risk for degradation in building envelopes is assessed through hygrothermal simulations. Due to the lack of long term climate data, hygrothermal simulations are performed for a certain location, and the results are generalised over a large region. However, this generalisation may not be valid, since the hygrothermal performance of building envelopes is highly influenced by local climate conditions. Therefore, we assessed the geographical variability on degradation risks in building envelopes. This paper presents the results of 34560 hygrothermal simulations of solid masonry walls, with and without interior insulation, and including a range of other parameter variations, for 20 synoptic weather stations across Belgium. Generally, the risk for degradation is higher at locations with a higher elevation above sea level. For Belgium, the elevation correlates well with the mean temperature (invers correlation), and the annual precipitation and wind-driven rain load. For a known wall orientation, the impact of interior insulation on the risk for freeze-thaw damage is most determined by the elevation above sea level. Also the mould index in uninsulated walls correlates best with the elevation. On the contrary, the brick type is more important than the location when considering wood decay of embedded beam heads in retrofitted walls. To conclude, the risk for degradation cannot be generalised, especially over areas with complex variations in orographic and climatological conditions.

Multi-scale thermo-poro-mechanical simulation of the frost resistance of low-heat and moderate-heat hydraulic concrete considering the aging microstructure

Hydraulic concrete structures in cold regions are vulnerable to freeze-thaw damage. This paper proposes a multi-scale simulation analysis approach to investigate the mechanical properties and frost resistance of Low-heat Portland (LHP) cement, Moderate-heat Portland (MHP) cement, and Ordinary Portland cement (OPC) concrete. The hydration heat, hydration degree, pore size distribution, and compressive strength of LHP, MHP, and OPC concrete at different curing ages, as well as the ice amount, expansion strain, and mechanical properties under different freeze-thaw cycles are calculated and compared. Due to the lower early-hydrated C3S content of LHP and the higher later-hydrated C2S content, the porosity of LHP after 90d curing is lower than that of MHP and OPC, resulting in better mechanical properties and frost resistance. On this basis, the evolution model proposed in this paper can quantitative analysis the frost resistance of cement paste based on different content of C3S and C2S, which provided a feasible method for predicting the frost resistance of hydraulic concrete structures in cold regions.

Prediction of mechanical properties of basalt fiber concrete using hybrid recurrent neural networks based on freeze-thaw damage quantification

Prediction of mechanical properties of basalt fiber concrete using hybrid recurrent neural networks based on freeze-thaw damage quantification

Damage characteristics and mechanisms of shear strength at the interface between fiber-reinforced concrete and rock under freeze-thaw cycles

In concrete reinforcement projects conducted in cold regions, freeze-thaw cycles contribute to the deterioration of the 'concrete-rock' interface strength. To examine the characteristics of shear stress and the evolution of damage at the interface of PVA fiber-reinforced concrete and rock under freeze-thaw conditions, a series of freeze-thaw shear tests were performed utilizing a self-developed fully saturated shear apparatus. This experimental approach was complemented by CT and scanning SEM analyses to investigate the structural changes at the interface under varying degrees of freeze-thaw damage. The findings revealed that the ECC-S specimens with PVA fibers exhibited an approximate 17.64 % increase in porosity and a 46.5 % reduction in rock strength after 45 freeze-thaw cycles. In contrast, OC-S specimens without PVA fibers experienced an approximate 10.51 % increase in porosity and a strength reduction of about 22.9 % under identical conditions. Furthermore, the study indicated that as the number of freeze-thaw cycles increased, the strength did not consistently rise with the angle of shear. A threshold was identified at an angle of 45°, beyond which the strength did not exhibit significant increases. This research holds considerable theoretical significance and practical implications for enhancing concrete reinforcement methodologies in cold regions, thereby ensuring the safe and efficient operation of rock engineering projects in such environments.

Evaluation of the influence of freeze–thaw cycles on the joint strength of granite in the Eastern Tibetan Plateau, China

The freeze–thaw cycles will lead to rock deterioration and pose a significant threat to engineering stability in cold regions. In this study, granite samples collected from the Luanshibao Landslide in the Eastern Tibetan Plateau were subjected to a maximum of 120 freeze–thaw cycles at two temperature paths (− 10–20 °C and − 20–20 °C). The Brazilian test, uniaxial and triaxial compression tests were carried out to evaluate the strength behavior of samples while the scanning electron microscopy tests to investigate microstructural changes. The correlation between strength be-havior and microstructural evolution of samples after freeze–thaw cycles was discussed. Results indicate that the uniaxial compressive strength, elastic modulus, tensile strength, and peak strength of samples decreased nonlinearly with freeze–thaw cycles. Besides, freeze–thaw cycles exhibit more pronounced effect on the strength of samples, compared to the temperature path. Based on the Mohr–Coulomb criterion, a joint strength expression was proposed for the tensile, compressive, and shear strengths of granite, which characterizes the influence of freeze–thaw cycles and strength paths on strength behavior of granite samples. SEM images revealed the freeze–thaw damage to the microstructure of granite and further the deterioration of the mechanical properties. The results of this study can provide a valuable reference for assessing the freeze–thaw strength of granite in the context of construction in highland areas, guiding the development of more resilient engineering practices and informing future research on the long-term durability of materials in extreme climates.

Impact of typical environments in China's western mountainous areas on the durability of railway concrete: a review

PurposeThis study aims to analyze the impact mechanism of typical environments in China's western mountainous areas on the durability of railway concrete and propose measures to improve durability.Design/methodology/approachWith the continuous promotion of infrastructure construction, the focus of China's railway construction has gradually shifted to the western region. The four typical environments of large temperature differences, strong winds and dryness, high cold and low air pressure unique to the western mountainous areas of China have adverse effects on the durability of typical railway structure concrete (bridges, ballastless tracks and tunnels). This study identified the characteristics of four typical environments in the western mountainous areas of China through on-site research. The impact mechanism of the four typical environments on the durability of concrete in different structural parts of railways has been explored through theoretical analysis and experimental research; Finally, a strategy for improving the durability of railway concrete suitable for the western mountainous areas of China was proposed.FindingsThe daily temperature difference in the western mountainous areas of China is more than twice that of the plain region, which will lead to significant temperature deformation and stress in the multi-layered structure of railway ballastless tracks. It will result in cracking. The wind speed in the western plateau region is about 2.5 to 3 times that of the plain region, and the average annual rainfall is only 1/5 of that in the plain region. The drying effect on the surface of casting concrete will significantly accelerate its cracking process, leading to serious durability problems. The environmental temperature in the western mountainous areas of China is generally low, and there are more freeze-thaw cycles, which will increase the risk of freeze-thaw damage to railway concrete. The environmental air pressure in the western plateau region is only 60% of that in the plain region. The moisture inside the concrete is more likely to diffuse into the surrounding environment under the pressure difference, resulting in greater water loss and shrinkage deformation of the concrete in the plateau region. The above four issues will collectively lead to the rapid deterioration of concrete durability in the western plateau region. The corresponding durability improvement suggestions from theoretical research, new technology development and standard system was proposed in this paper.Originality/valueThe research can provide the mechanism of durability degradation of railway concrete in the western mountainous areas of China and corresponding improvement strategies.

Investigation on the evolution of concrete pore structure under freeze-thaw and fatigue loads

Hydraulic concrete structures in seasonal frozen regions serve under freeze-thaw cycles and cyclic loading conditions which cause notable alterations in the concrete pore structure and a significant reduction in the mechanical properties and durability of concrete. To understand the macroscopic and mesoscopic damage processes and mechanism of concrete subjected to freeze-thaw cycles and cyclic loading lead, the compressive experiment and computed tomography test of concrete after freeze-thaw and fatigue loading tests were conducted. And the influences of freeze-thaw cycle damage and cyclic loading damage on the pore structure of concrete were analyzed. The relationships between concrete pore fractal dimension, compressive strength, and elastic modulus were revealed. The concrete average pore size can be regarded to grows linearly under freeze-thaw and cyclic loading. The porosity, pore volume, and pore surface area increase with the increase in freeze-thaw cycles, and their relationship can be represented by a quadratic function. However, they first decrease and then increase with the increase of loading cycles after a specific freeze-thaw cycles number. Under the combined action of freeze-thaw cycles and cyclic loading, the non-uniformity degree of concrete pore distribution decreases, and the overall structure is more regular. The distribution of single pore morphology tends to be spherical and banded, respectively. The cyclic loading promotes the extension of the internal pores and cracks of freeze-thaw-damaged concrete which aggravates damage of concrete. Under freeze-thaw cyclic loading, the concrete compressive strength and elasticity modulus is linearly and positively correlated with fractal dimension. With the increase of loading cycles number after freezing and thawing, the fractal dimension and compressive strength decrease, and the elasticity modulus has a larger dispersion. The relationship model between concrete compressive strength and fractal dimension can well describe the macroscopic and mesoscopic evolution of concrete under freeze-thaw and cyclic loading. The results can provide a scientific basis for improving the design and maintenance of concrete and benefit extending the long-term service life of hydraulic concrete structures in cold climates.

Monitoring evolutionary damage of bended concrete beams subjected to freeze-thaw cycling through piezoelectric-enabled wave propagation method

Tunnels in cold regions are often subjected to freeze-thaw cycling, which poses a great challenge to a large number of tunnels in operation or to be built in these regions. Therefore, structural health monitoring (SHM) for lining concrete in cold regions is essential to ensure the safety and long-term operation of tunnels. In this study, the wave propagation method (WPM) is applied for the first time to monitor the cyclic freeze-thaw damage of lining concrete. First of all, the failure behaviors of concrete beams subjected to the coupling effect of flexural loading and freeze-thaw cycling are investigated. Particularly, the authors propose a refined numerical model to simulate the freeze-thaw cycling damage process of concrete beams considering the ice-water phase transition and concrete elastoplastic damage. Based on the numerical results, the internal damage expansion and flexural strength attenuation of concrete beams are revealed. Furthermore, the dynamic attenuation characteristics of stress waves are analyzed by using the wavelet packet decomposition and continuous wavelet transform to reveal. In addition, the WPM-based energy index is proposed to characterize the freeze-thaw damage degree of the lining concrete. A strong correlation is found between the stress wave signal and freeze-thaw damage, with a favorable correlation coefficient of 0.932, suggesting the excellent performance of the WPM in assessing the freeze-thaw damage of lining concrete. This research sufficiently manifests the applicability of the WPM method to monitoring the freeze-thaw damage within cold regional tunnel linings.

Strength degradation characteristics and damage constitutive model of sandstone under freeze-thaw cycles.

Thorough investigation into the laws governing frozen rock damage in high-altitude and cold regions can offer valuable insights for advancing infrastructure construction, ecological environment protection, and sustainable development on the Qinghai-Xizang Plateau. This study combined with the seasonal variation patterns of frozen rocks in the Qinghai-Xizang Plateau, and processed the rock samples using a freeze-thaw interval of -20 °C~20 °C. Uniaxial compression test was conducted based on the MTS816 rock mechanics testing system. The porosity changes of rock samples with different freeze-thaw cycles were analyzed using the MesoMR12-060H-I nuclear magnetic response analysis system. A rock freeze-thaw load coupled damage constitutive model was derived using the Lemaitre equivalent strain theory. Research has shown that during the freezing process, the pore water inside the rock sample is affected by the phase change of water-ice, resulting in frost heave force, which further promotes the expansion of the pore walls and the initiation of new cracks. When melted, pore water migrates towards newly formed micropores, thereby affecting the changes in the pores of rock samples. The increase in porosity at the micro level weakens the mechanical parameters of rocks at the macro level. The segmented freeze-thaw damage constitutive model based on Lemaitre equivalent strain theory can well fit the experimental results involved in this study, as well as the experimental results obtained by other researchers. The compaction stage can partially reflect the changes in sandstone pore structure under freeze-thaw cycles.

Evaluating the effectiveness of innovative pervious concrete pavement system for mitigating urban heat island effects, de-icing, and de-clogging

The Urban Heat Island (UHI) effect and water runoff pose significant challenges in urban environments. This research aimed to mitigate the UHI effect through the implementation of an innovative pervious concrete pavement (IPCP) system. Furthermore, the study investigated the main obstacles associated with conventional permeable pavements, such as clogging and vulnerability to freeze-thaw damage. To achieve this goal, a physical model apparatus was developed to simulate temperature variations, de-icing processes, and clogging incidents in the IPCP system. This apparatus was specifically designed with distinct sections for both the pervious concrete layer and the subbase layer. The findings revealed that careful selection of an appropriate subbase material significantly contributed to reducing the temperature rise (up to 37 %) under varying environmental conditions by enhancing evaporative cooling capacity. Additionally, the pavement simulation apparatus featured a dual-function drainage system. This system not only regulated the water level within the pavement by draining excess water but also addressed clogging (with up to 97 % permeability recovery) and de-icing concerns through the application of air pressure and hot water injection, respectively.

Study on the freeze-thaw damage degree and its influence on the shear strength parameters of sandstones

The variations of shear strength parameters against the freeze-thaw cycles are not well understood in the previous study. This research mainly investigated the influence of freeze-thaw treatment on the shear strength parameters and their relationship with the freeze-thaw damage variable for sandstones. The fraction dimensions of sandstone surfaces and basic friction angles display an increasing trend under freeze-thaw cycles. It implies that the sandstone surface becomes rougher due to the freeze-thaw loss of cementation minerals and thus induces the increase in the basic friction angle. Another interesting finding is that although the cohesion of sandstone reduces, the internal friction angle also increases with increasing freeze-thaw cycles. Thus, the reduction in the shear strength under freeze-thaw actions should be attributed to the loss of cohesion. Moreover, the change of shear strength parameters is also related with the freeze-thaw damage degree. As the number of freeze-thaw cycles increases, the increase in porosity and reduction in P-wave velocity are much larger for the YY and YR sandstones with higher porosities, thus, they suffer much more serious freeze-thaw damage, and they have a much larger variation in shear strength parameters. The novel finding is that the growth in basic friction angle is positively correlated with the increase of freeze-thaw damage, and the internal friction angle exponentially increases with the increase of freeze-thaw damage. This study provides a much better understanding of the change of the shear strength parameters under freeze-thaw cycles.

Microwave self-healing characteristics of the internal voids in steel slag asphalt mixture subjected to salt-freeze-thaw cycles

Microwave heating technology can be used to repair freeze-thaw (F-T) cycle damage and cracks caused by the use of snow melting salts and de-icers in winter. This study utilized three different gradations of asphalt mixtures: AC-13, SMA-13, and OGFC-13, and enhanced their microwave absorption performance with steel slag (SS). The heating uniformity was evaluated through surface and internal temperature tests. Additionally, the mechanisms of damage and healing of the asphalt mixtures under salt freeze-thaw (S-F-T) damage conditions were explored using S-F-T cycles test and X-ray computed tomography scans (CT). The results showed that OGFC-13 exhibits a significantly higher rate of temperature increase compared to the other two types due to its stronger wave absorption capacity. The thermal hysteresis caused by steel slag leads to uneven spatial temperature distribution. The study recommends an optimal microwave heating time of 40 s for SS asphalt mixtures, which has minimal impact on the mixture structure, by defining an evaluation method for the uniformity index and local overheat ratio. After undergoing S-F-T cycles, the porosity of all three asphalt mixtures increased, particularly at the top and bottom of the specimens. Among them, OGFC-13 exhibited the poorest durability under S-F-T conditions, with the S-F-T cycles having a significant impact on medium-sized voids (0.15–0.6 mm). After microwave heating, AC-13 and SMA-13 showed good repair effects, with porosity levels returning to their initial states. For large voids (>2.36 mm) in OGFC, microwave heating may not effectively reduce the number of voids. Additionally, the healing rate of mixture specimens at certain mid-height ranges is higher due to elevated surface temperatures in these areas, making it especially effective in repairing F-T damage. This study shows that microwave heating of SS asphalt mixtures can improve the durability of pavement in cold regions. However, implementation challenges include the need for specialized equipment and potential uneven heating. Future research should explore optimizing microwave heating techniques to minimize local overheating and investigate the long-term performance of microwave-repaired asphalt pavements under various environmental conditions.

Study of freeze-thaw deterioration of saturated and unsaturated hydraulic concrete based on measured strain

In actual concrete water projects, areas such as the back surface, above-water surface, and even areas where the water level fluctuates are in the unsaturated freeze-thaw state. The complexity of freeze-thaw tests of unsaturated hydraulic concrete has thus far prevented a sound understanding of the mechanisms at work in freeze-thaw deterioration of unsaturated hydraulic concrete. Given this situation, this study first compares three different unsaturated hydraulic concrete freeze-thaw test processes (polyurea seal, paraffin seal, and vacuum-bag seal) and then uses the vacuum-bag seal method to implement freeze-thaw tests of unsaturated hydraulic concrete. Afterward, three test schemes (unsaturated sealed freeze-thaw, water-freeze-thaw without air-entraining agent, and water-freeze-thaw with air-entraining agents) are conducted and the mechanisms of freeze-thaw deterioration of saturated and unsaturated hydraulic concrete are evaluated based on the measured temperature and strain of the concrete specimens. The results reveal a continuous and irreversible deterioration leading to the freeze-thaw damage of unsaturated sealed freeze-thaw specimens and water-freeze-thaw specimens with and without an air-entraining agent. After 200 freeze-thaw cycles, the cumulative residual strain of the aforementioned three test schemes reach 47 με, 616 με, and 273 με, respectively. The thermal expansion coefficient of concrete remains relatively constant with increasing freeze-thaw cycles. Water-freeze-thaw specimens without air-entraining agents have a greater thermal expansion coefficient than those with air-entraining agents, and unsaturated sealed freeze-thaw specimens have the smallest thermal expansion coefficient. The frost heave coefficient increases with increasing freeze-thaw cycles, and water-freeze-thaw specimens without air-entraining agents have greater frost heave coefficients than those with air-entraining agents.

Calcined Clays as Concrete Additive in Structural Concrete: Workability, Mechanical Properties, Durability, and Sustainability Performance.

Calcined clays (CCs) as supplementary cementitious materials (SCMs) can be a promising option to reduce clinker content and CO2 emissions in eco-friendly concretes. Although CCs as components of composite cements in combination with Ordinary Portland Cement (OPC) and limestone powder (LSP) have attracted industry interest, their use as concrete additives is limited. This study investigates the effects of the addition of CCs on the fresh and hardened properties of industry-standard ready-mixed concretes. Four concrete mix designs, each with three superplasticizer dosages, were tested, resulting in 12 variations. The CCs used, which are typical of 2:1 bentonite clays with low metakaolin content, reflect the clays available in Germany. The results showed that CCs significantly influenced the workability, which could be controlled with a high superplasticizer dosage. Increased CC contents reduced bleeding tendencies, which was beneficial for certain structural applications. Early age strength decreased with CCs, but the 28-day strength exceeded that of pure OPC concretes up to 30 wt% CCs. Resistance to CO2-induced carbonation decreased with higher levels of CCs but was comparable up to 15 wt%. Freeze-thaw damage decreased, and chloride migration resistance improved due to a denser microstructure. The global warming potential (GWP) of the concretes tested is in line with that reported in the literature for concretes made from highly blended cements, suggesting that CCs can improve the sustainability of concrete production.

Freeze-thaw resistance and service life prediction of fly ash incorporated ultra-high ductility magnesium phosphate cement-based composites

To develop ultra-high ductility magnesium phosphate cement-based composites (UHDMC) suitable for cold areas and fully utilize solid waste, the effects of fly ash (FA) substitution and freeze-thaw cycles on the mechanical properties and freeze-thaw resistance of UHDMC specimens were explored. The mechanism of freeze-thaw damage was revealed by mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM). Freeze-thaw damage model for UHDMC was established to predict its service life. The results showed that, after 300 freeze-thaw cycles, the compressive strength retention rate of the UHDMC specimens with FA substitution from 10 % to 30 % was above 88.7 %, and the tensile strain maintained above 3.48 %, still presenting the characteristics of multi-cracking and strain hardening. Meanwhile, after 600 freeze-thaw cycles, the mass loss rate and the dynamic elastic modulus of UHMPC specimens with FA substitution from 10 % to 30 % were below 1.38 % and above 81.1 %, respectively. The mechanical properties were mainly related to the total porosity and macropores. The effect of the water solubility of prismatic struvite-K crystals and the secondary hydration production of filamentous struvite potassium crystals on the matrix presented well explanation for the excellent freeze-thaw resistance of UHDMC specimens with FA substitution from 10 % to 30 %. At last, a freeze-thaw damage model for UHDMC specimens with FA substitution below 30 % based on the Weibull probability distribution function was established, predicting that their service life was up to 232 years in the northeastern of China.

Freeze-thaw impacts on geocell-stabilized bases considering effects of water supply and compaction

Although Novel Polymeric Alloy (NPA) geocells have been applied to stabilize road bases against the freeze-thaw (F-T) damage in practice, the relevant research lags the application. A scarcity of research has been reported to comprehensively evaluate the benefits of geocell stabilization in enhancing the F-T performance of bases. This study aims to investigate quantitatively the F-T performance of geocell-stabilized bases, focusing on two influencing factors-i.e., water supply and degree of compaction in the bases. A series of model-scale experimental tests (19 tests) was conducted using an upgraded customized apparatus. The results showed that the inclusion of geocells was beneficial for reducing frost heave and thaw settlement as well as mechanical properties (i.e., stiffness and ultimate bearing capacity) of road bases. The benefit of geocells was more remarkable for the well compacted bases than for the poorly compacted bases. The benefit was more pronounced in the open system than in the closed system.

Research on performance variations of different asphalt binders results from microwave heating during freeze-thaw cycles

Microwave heating (MH) as a sustainable pavement maintenance method can effectively repair the cracks caused by freeze-thaw (FT) damage. However, binders' properties may be weakened during this process then reduces the pavement life. For this purpose, this work aims to investigate the performance changes of neat binders (Nb) and high-viscous binders (Hb) during FT and MH. The physicochemical, rheological, and deformation properties are investigated after FT and MH. Results indicate that asphalt binders become harder and lead to an increase in carbonyl index (CI) and sulfoxide index (SI) after FT. MH has a limited damage level for binders especially for Hb, causing a slight increase in CI and SI, compared to binders after FT. Polymers play an important role in the viscoelastic responses of asphalt binders. Changes in viscoelastic properties of Nb mainly result from the binder damage of FT and MH, while viscoelastic changes of Hb are mainly due to the damage of polymers. This different damage mechanism causes Hb to show better resistance compared to Nb, which is reflected in modulus and phase angle. BBR tests indicate that MH can further deteriorate the damage of both binders, but Hb shows a lower performance decline compared to Nb, and it is recommended to conduct MH at the region with a minimum temperature above −12 °C. MSCR results reveal that FT and MH can improve the rutting resistance of Nb due to the hardening phenomenon after damage, and reduce the elastic stability of Hb due to the damage to polymers. In summary, Nb is sensitive to MH, its performance can be further damaged after MH. Hb has better resistance to MH, its properties do not further deteriorate, so Hb is more applicable to MH.