Search

Freeze-thaw resistance ability of concrete is an important issue when evaluating its durability. In this research, the objective was to predict concrete resistance to such cycles by analyzing water absorption based on the critical water saturation theory. In order to achieve this goal, detailed experiments were conducted, including water absorption, pore structure scanning, and mercury intrusion porosimetry of concrete with air-entraining admixture and different fiber content to obtain critical indicators, such as water absorption, porosity, and air void spacing factor, which formed the basis for predicting the service life of concrete. To predict the service life of concrete under freeze-thaw cycles, the critical saturation theory was utilized, taking into account environmental parameters and experimental indexes. The service life of concrete against freeze-thaw using air-entraining admixture and fibers had been calculated quantitatively in this paper. The results show that the predicted service life of concrete with air-entraining admixture was increased by more than 50 times, and using both air-entraining admixture and fiber could increase the service life by more than 80 times, even reaching 249 years. [ABSTRACT FROM AUTHOR]

The global challenge faced due to the impact of the construction industry on climate change, along with the issues surrounding sustainable waste disposal, has necessitated various research on using waste products as eco-friendly alternatives in construction. In this study, the avoidance of waste disposal through landfills in Australia was encouraged by incorporating lime kiln dust (LKD) and tire rubber waste (TRW) into masonry mixes to manufacture green bricks. Furthermore, the investigations in this article highlight the use of mercury intrusion porosimetry (MIP) to determine the durability of the LKD-TRW bricks when exposed to freeze–thaw (F-T) cycles by examining the pore size distribution within the bricks. The LKD waste was blended with ground granulated blast furnace slag (GGBFS) at a 70:30 blending ratio and combined with the TRW in stepped increments of 5% from 0 to 20% to produce these eco-friendly bricks. The compressive strength (CS), flexural strength (FS), frost resistance (FR), pore size distribution according to mercury intrusion porosimetry (MIP), and the water absorption (WA) properties of the bricks were assessed. The CS and FS values at 28 days of curing were recorded as 6.17, 5.25, and 3.09 MPa and 2.52, 2, and 1.55 MPa for 0, 5, and 10% TRW contents, respectively. Durability assessments using the F-T test showed that the bricks produced with 0% TRW passed as frost-resistant bricks. Furthermore, the results from the MIP test showed a total pore volume of 0.033 mL/g at 3 µm pore size for the 0% TRW content, further confirming its durability. Hence, the 0% LKD-TRW bricks can be utilized in cold regions where temperatures can be as low as −43 °C without deteriorating. Lastly, WA values of 7.25, 11.76, and 14.96% were recorded for the bricks with 0, 5, and 10% TRW, respectively, after the 28-day curing period. From all of the results obtained from the laboratory investigations, the LKD-TRW bricks produced with up to 10% TRW were within the satisfactory engineering requirements for masonry units. [ABSTRACT FROM AUTHOR]

Freezing and thawing (F/T) is an important occurrence in cold regions influencing soil geotechnical characteristics. Current study investigates effects of lime, Rice Husk Ash (RHA) and Nano-clay on unconfined compressive strength and F/T of loess under open and closed schemes. Loess was treated with 2, 4, 6 and 8% lime and RHA and 0.5, 1.0, 1.5 and 2% Nano-clay and compacted at optimum conditions. Samples were cured for 1, 7, 14 and 28 days at 35 °C before freezing at −23 °C and thawing at room temperature for 24 h intervals. Tests conducted on untreated and RHA and Nano-clay treated samples showed total loss of strength after one F/T cycle with noticeable weight and volume changes by samples subjected to open F/T. Exposing samples to closed F/T resulted in smaller changes in volume and strength. Samples treated independently with lime or concurrently with RHA and Nano-clay showed significant resistance to F/T particularly with curing time. Formations of chemical compounds bind particles, reduce void ratio resulting in a solid durable structure resisting freezing. Open F/T proved more detrimental than closed F/T scheme exhibiting moisture accessibility to be a dominant factor on F/T process. [ABSTRACT FROM AUTHOR]

An investigation was designed to assess the performance of pervious concrete prepared with fly ash (FA) and recycled concrete aggregates (RCA) in place of Portland cement (PC) and natural aggregates (NA). The percentage of NA replacement with RCA was varied (0%, 50% and 100%), while the percentage of FA substitution was fixed at 10%. Various fresh (workability and consistency), mechanical (compressive strength, split tensile and shear strength), durability (abrasion resistance, freeze–thaw resistance, flexure and acid resistance) and microstructural properties of the pervious concretes were evaluated after different curing periods. The findings showed that the incorporation of RCA at different levels and partial substitution of FA was desirable pervious concrete used for structural and pavement construction purposes. The incorporation of 10% FA in addition to higher levels of RCA was found to be particularly beneficial in refining the microstructure of pervious concrete. A homogenous microstructure with dense and layered calcium silicate hydrate and calcium hydroxide was observed for the mix made with 10% FA and 100% RCA. [ABSTRACT FROM AUTHOR]

This research investigates the durability of large-format 3D-printed thermoplastic composite material systems under environmental exposure conditions of moisture and freeze–thaw. Durability was evaluated for two bio-based composite material systems, namely wood-fiber-reinforced semi-crystalline polylactic acid (WF/PLA) and wood-fiber-reinforced amorphous polylactic acid (WF/aPLA), and one conventionally used synthetic material system, namely short-carbon-fiber-reinforced acrylonitrile butadiene styrene (CF/ABS). The moisture absorption, coefficient of moisture expansion, and reduction of relevant mechanical properties—flexural strength and flexural modulus—after accelerated exposure were experimentally characterized. The results showed that the large-format 3D-printed parts made from bio-based thermoplastic polymer composites, compared to conventional polymer composites, were more susceptible to moisture and freeze–thaw exposure, with higher moisture absorption and greater reductions in mechanical properties. [ABSTRACT FROM AUTHOR]

Waste andesite sand (AS) is produced when cutting andesite stone and doing other stone dressing procedures. Problems with storage and environmental pollution may result from the disposal of AS. These issues might be resolved using AS in the manufacturing of alkali-activated composites. Pozzolanic powders are used extensively in the construction sector to reduce the need for cement, which lowers the price of making concrete and lessens environmental pollution from CO2 emissions from cement producers. This paper reports the findings of an experimental examination into the impact of diatomite powder and waste andesite sand on the microstructural, durability, and mechanical characteristics of environmental-friendly alkali-activated lightweight composites (AALC). Ground blast furnace slag (GBFS) and diatomite powder (DP) were used as the main solid precursors, silica sand (SS) and waste andesite sand (AS) were used as fillers for the design of AALC mixtures. The alkaline activators adopted in this study were sodium hydroxide and sodium silicate. Physico-mechanical characteristics, transport properties, thermal conductivity, sorptivity, and drying shrinkage of generated AALC mixes were also examined in addition to its performance under freeze–thaw (F–T) cycles and high temperatures. SEM analyses of the AALC were conducted to investigate the microstructure of the produced specimens. Sixteen AALC mixtures were created using GBFS/DP ratios of 100/0, 90/10, 80/20 and 70/30 and AS was used to replace silica sand (SS) in four different rates of 0%, 25%, 50%, and 100%. Prior to ambient curing, the manufactured samples were cured at 80 °C for 24 h to quicken geopolymerization. The findings showed that the mixture with 100% GBFS and 100% AS had a maximum compressive strength of around 60 MPa. When GBFS was replaced with 20% and 30% DP, the compressive strength of AALC specimens was drastically reduced. The AALC mixtures containing 20% and 30% DP showed the lowest thermal conductivity results. The best high-temperature resistance was demonstrated by the mixture D20A50, which comprises 20% DP and 50% AS and experiences a strength loss of 20.7% at 900 °C. The best resistance to freezing and thawing exposure was found in mixtures that contained 10% DP and 50% AS. [ABSTRACT FROM AUTHOR]

Wood is a natural, organic, renewable, sustainable, and versatile building material. The mechanical reinforcement and durability of carbon fiber-reinforced polymer (CFRP) composites to wood are issues of concern. This study focuses on the durability aspects of CFRP-strengthened wood members. To ensure durability, we tested carbon fiber sheets wrapped by wooden member specimens, subjected to two different environments, including seawater dry-wet cycling and freeze-thaw cycling, on surface hardness. The samples also underwent SEM observation, pull-off strength, compressive shear strength, compressive strength, and flexural strength tests. After the above-mentioned environmental conditions and tests, the effect and durability of the CFRP-strengthened wood members were evaluated. The results indicate that wood members wrapped with CFRP can increase their strength, mainly when applying two resin layers. After two environmental durability tests, the wood components bonded well with CFRP. Our findings indicate that as the number of reinforcement layers increased, the compressive strength, flexural strength, and compression-shear strength of CFRP-reinforced wood specimens increased, but the pull-off strength remained unchanged.

Understanding the deterioration mechanism of concrete structures in cold climates that are susceptible to frost damage from repeated freezing and thawing cycles is imperative for ensuring their durability and serviceability. This study analyzed the impact of freeze–thaw (FT) exposure on concrete structural behavior by developing three machine-learning approaches—artificial neural networks (ANN), random forests (RF), and support vector machines (SVM)—to quantify the progressive loss in compressive strength after repeated FT cycles. The results demonstrate that all of the proposed models can predict the deteriorated compressive strength of concrete and align closely with the experimental results. The ANN model demonstrated the highest prediction accuracy with an R2 of 0.924, exhibiting a higher prediction accuracy than RF and SVM models. Sensitivity analysis using Shapley additive explanations (SHAP) revealed that concrete with an initially high strength, along with a lower water–cement ratio and air entrainment, exhibited the least reduction in compressive strength after freezing–thawing cycles, underlining the positive impact of these factors on the FT durability of concrete. The proposed modeling approach accurately predicts the residual compressive strength after FT exposure, enabling the selection of optimal concrete materials and structural designs for cold climates. [ABSTRACT FROM AUTHOR]

For several decades, class F fly ash has been an attractive supplementary cementitious material, at least in part, due to its ability to reduce Portland cement consumption and mitigate alkali-silica reactions in concrete. However, fly ash availability is becoming uncertain as the energy industry decommissions coal burning power plants as it transitions to renewable energy production. This situation creates a need to identify viable and sustainable alternative supplementary cementitious materials. There are several types of supplementary cementitious materials, such as natural pozzolans, metakaolin, or ground granulated blast-furnace slag, which appear to be potential alternatives to fly ash in concrete. In this research, a locally available natural pozzolan (pumicite) was selected to replace fly ash in concrete. After conducting alkali-silica reaction tests on mortar mixtures, rheological and strength properties, shrinkage, resistance to freezing and thawing, and chloride ion permeability of concrete mixtures containing different amounts of fly ash and natural pozzolan were evaluated. The results showed that pumicite was more effective than fly ash at mitigating the alkali-silica reaction, and a pumicite content of 20% was necessary to mitigate the alkali-silica reaction. Ternary mixtures containing both pumicite and fly ash were the most effective cementitious materials combinations for mitigating the alkali-silica reaction expansion. Additionally, pumicite provided acceptable compressive strength and modulus of rupture values (greater than 4.0 MPa) that exceeded the flexural strengths provided by established mixtures containing only fly ash. Shrinkage and durability factor values for all mixtures were less than 710 μstrain and greater than 75, which are generally considered acceptable. Additionally, all mixtures with acceptable alkali-silica reaction expansions had very low chloride permeability. These results indicate that pumicite can be a reliable alternative for fly ash. [ABSTRACT FROM AUTHOR]

This research investigates the durability of large-format 3D-printed thermoplastic composite material systems under environmental exposure conditions of moisture and freeze–thaw. Durability was evaluated for two bio-based composite material systems, namely wood-fiber-reinforced semi-crystalline polylactic acid (WF/PLA) and wood-fiber-reinforced amorphous polylactic acid (WF/aPLA), and one conventionally used synthetic material system, namely short-carbon-fiber-reinforced acrylonitrile butadiene styrene (CF/ABS). The moisture absorption, coefficient of moisture expansion, and reduction of relevant mechanical properties—flexural strength and flexural modulus—after accelerated exposure were experimentally characterized. The results showed that the large-format 3D-printed parts made from bio-based thermoplastic polymer composites, compared to conventional polymer composites, were more susceptible to moisture and freeze–thaw exposure, with higher moisture absorption and greater reductions in mechanical properties.

This study investigated the possibility of using basalt, diabase, and andesite natural stones instead of virgin fine aggregates. Substitution percentages varied between 10% and 40% according to the sand mass. The effect of basalt, diabase, and andesite addition on concrete performance was evaluated using strength and durability tests performed on the samples at the end of 7, 28, and 60 days. In addition, petrographic-mineralogical, X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses of basalt, diabase, and andesite stones were evaluated. The 60-day compressive strengths of the samples were 39% higher in samples with basalt additives, 35% higher in samples with diabase additives, and 37% higher in samples with andesite additives than in the control sample. At the end of 28 days, the water absorption rates of the samples with additives were 113.83%–55.81% less that of the control sample, on average, and the samples suffered 26%–52% less wear loss than the control sample. In addition, at the end of the freeze–thaw cycles, the compressive strengths of the samples with basalt, diabase, and andesite added were 67%, 63%, and 64% higher than that of the reference sample, respectively. The compressive strength values of samples exposed to the effect of sulfate for 180 days were examined, and samples with basalt, diabase, and andesite added had compressive strength values an average of 33.35%, 32.52%, and 32.80% higher than that of the reference sample, respectively. This study proves the usability of basalt, diabase, and andesite natural stones and their wastes as fine aggregate. [ABSTRACT FROM AUTHOR]

The aim of this study is to evaluate the potential weathering of three different varieties of Algerian limestones. Standard durability tests such as salt crystallization, thermal shock or freeze–thaw are usually employed to compared stone behaviors. However, salt crystallization tests do not consider the thermal effect on the samples, and freeze–thaw tests, the non-pure water solution in real conditions. In this study, standard tests were compared to adapted tests, to efficiently separate the real damage agent for each situation, and to develop durability tests close to real environments. The evaluation was carried out by non-destructive measurements such as porosity variations, water capillary uptake and P-wave velocity. The residual deformation in fresh samples and those subjected to the different tests was also quantified using strain gauges. The results showed that limestones with the same porosity and different microstructure behave differently. The combined effect of thermal shock, salt crystallization, and freeze–thaw tests modify the stone's porous network by opening and creating new fractures. The variation of the residual strain is considered as the main parameter that conditions the final deterioration of the stone, especially on the surface. In the travertine stone, the exposition to high temperature in the standardized salt crystallization tests is more damaging than the salt crystallization itself. At low temperature, freeze–thaw cycles with salt solutions show slightly less deformation than the ones carried out with pure water and a stabilization after 20 cycles. [ABSTRACT FROM AUTHOR]

Alkali-activated composites are significant materials in reducing CO2 emissions and ensuring sustainability. With the increasing concerns about climate change globally, the interest in alkali-activated materials has also increased. Researching different fibers has very important potential in this area. This study aims to make alkali-activated concretes widespread in the concrete sector by using the materials common in conventional concretes and ensuring that alkali-activated concretes are an alternative in terms of sustainability. Experimental studies were conducted to examine the mechanical, durability, and microstructural properties (SEM) of slag-based alkali-activated concrete (AASC) reinforced with three various fibers. The fibers, polypropylene (PP), polyamide (PA), and steel (ST), were used with two ratios (%0.4 and %0.8 by vol.). Compressive, splitting tensile, and flexural strength tests were carried out at 28 and 90 days. In terms of durability properties, the samples were exposed to high temperatures (300–600–900 °C) and freeze-thaw test (250 cycles). The results showed that the addition of fibers improved the strength and durability properties; for instance, the existence of steel and polypropylene fibers increased the flexural toughness factor values by 430% and 260%, respectively. Moreover, the compressive strength of the fibrous samples exposed to 900 °C was obtained in the range of 6-23 MPa. [ABSTRACT FROM AUTHOR]

In this study, mechanical, durability, and microstructural properties of fiber-reinforced slag-fly ash-based alkali-activated concretes were investigated. Polypropylene (PP), steel (ST), and polyamide (PA) fibers were used, and the mechanical properties such as compressive, tensile, and flexural behaviour were investigated. High temperature and freeze-thaw tests were carried out within the scope of durability properties. High-temperature tests were conducted at 300, 600, and 900 degrees. Freeze-thaw tests were applied in 250 cycles. Microstructural analyzes were also carried out to understand the matrix composition of fiber-reinforced slag-fly ash-based alkali-activated concrete. The fibers have improved many mechanical properties, such as tensile and flexural strength. Existing building codes have shown consistent results in predicting the compressive strength of fiber-reinforced alkali-activated concretes at high temperatures. In addition, comparisons were made using existing building codes for splitting tensile strength and flexural strength, and new models were proposed. [ABSTRACT FROM AUTHOR]

This paper focuses on the deterioration mechanism of hybrid basalt-polypropylene fiber-reinforced concrete (HBPRC) under the coupling of sulfate freeze-thaw cycles. The changes in the macroscopic properties of HBPRC under the influence of different volume contents of basalt fiber (BF), polypropylene fiber (PF) and hybrid BF-BF were investigated. The microstructure of HBPRC was characterized using the nuclear magnetic resonance (NMR) technique, X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the deterioration models of the BF- matrix interfacial transition zone (BF-ITZ) and the PF- matrix interfacial transition zone (PF-ITZ) in HBPRC were developed. The results showed that the fibers effectively reduced the cracking and macroscopic property damage induced by sulfate freeze-thaw cycles as the number of freeze-thaw cycles increased. When both BF and PF volume contents are mixed at 0.05 %, they can produce complementary effects, and their formation of a uniformly distributed three-dimensional mesh structure is more conducive to reducing the damage to the concrete, and their relative dynamic modulus of elasticity and compressive strength after 300 times of sulfate freeze-thaw cycles were increased by 67.10 % and 46.92 % compared with control concrete. At the same time, the addition of fibers resulted in a more stable evolution of the pore structure of the concrete, and the porosity of the specimens with fibers added at a volume admixture of 0.05 % and 0.1 % was reduced by 13.69–21.35 % after 300 cycles of sulfate freeze-thaw cycling, compared with control concrete. From the BF-ITZ and PF-ITZ deterioration models, it was concluded that the differences in the bonding performance of BF and PF to the concrete matrix affected the degree of frost damage to which they were subjected to coupling and the efficiency of salt solution replenishment, which in turn led to differences in the damage of each group of HBPRC. The reliability of the model was further verified by SEM observation of the morphological changes of different fiber-matrix ITZs before and after sulfate freeze-thaw cycles. • Explores the performance degradation pattern of HBPRC under sulfate freeze-thaw cycles. • Explores the internal degradation mechanisms of HBPRC under sulfate freeze-thaw cycles. • Degradation models for the BF-ITZ and the PF-ITZ are proposed. [ABSTRACT FROM AUTHOR]

Understanding the deterioration mechanism of concrete structures in cold climates that are susceptible to frost damage from repeated freezing and thawing cycles is imperative for ensuring their durability and serviceability. This study analyzed the impact of freeze–thaw (FT) exposure on concrete structural behavior by developing three machine-learning approaches—artificial neural networks (ANN), random forests (RF), and support vector machines (SVM)—to quantify the progressive loss in compressive strength after repeated FT cycles. The results demonstrate that all of the proposed models can predict the deteriorated compressive strength of concrete and align closely with the experimental results. The ANN model demonstrated the highest prediction accuracy with an R2 of 0.924, exhibiting a higher prediction accuracy than RF and SVM models. Sensitivity analysis using Shapley additive explanations (SHAP) revealed that concrete with an initially high strength, along with a lower water–cement ratio and air entrainment, exhibited the least reduction in compressive strength after freezing–thawing cycles, underlining the positive impact of these factors on the FT durability of concrete. The proposed modeling approach accurately predicts the residual compressive strength after FT exposure, enabling the selection of optimal concrete materials and structural designs for cold climates.

In cold regions, the construction of engineered structures such as roads and embankments experiences alternate freezing and thawing cycles, thus affecting their long-term stability or durability. This research aims to investigate the impact of freeze–thaw cycles on the geotechnical characteristics of red mud tailing (bauxite residue) stabilized with two biopolymers, guar gum (GG) and xanthan gum (XG). The effect of elevated temperature during sample preparation (thermogelation) on the strength and durability was also studied. Red mud tailing samples stabilized at various concentrations (0.25%, 0.5%, 1%, and1.5%) and curing periods (7, 14, and 28 days) were exposed to 10 freeze–thaw cycles. The results showed the efficacy of thermogelation biopolymers in enhancing the compressive strength and freeze and thaw resistance compared to other treated conditions. Also, post-freeze–thaw conditioning, the results showed maximum recovery of strength at 14 days of curing period when the temperature was constantly above 0°C. The findings postulated the biopolymer as a promising, environmentally friendly material for road constructions (particularly for subbase and shoulder) in cold regions. [ABSTRACT FROM AUTHOR]

In this study, it is aimed to determine the durability performances of bitumen-modified sulfur polymer concrete (SPC) under the long-term freeze–thaw cycles and to examine the results in comparison with sulfur concrete (SC) and traditional Portland cement concrete (PCC). Three different bitumen ratios were selected as 2.5%, 5%, and 7.5% by weight of pure sulfur for the modification. To check whether the modification was sufficiently realized, the changes in the microstructure of the modified sulfur were examined by a polarized optical microscope, differential scanning calorimetry, and scanning electron microscope. The sulfur modification of the modified sulfur sample prepared with 2.5% bitumen addition among the selected bitumen ratios was successful. Therefore, modified sulfur prepared with this ratio was used in the preparation of SPC. SPC, SC, and PCC prepared with the similar compressive strength were subjected to 150, 300, 450, 600, and 1200 freeze–thaw cycles. After the freeze–thaw cycles, the compressive strength, ultrasonic pulse velocities, relative dynamic modulus of elasticity, and weight changes were examined. At the end of 1200 cycles, the residual compressive strength value in SC and SPC was determined 24% and 58%, while the strength test could not perform on the PCC. SPC, SC, and PCC showed a reduction in RDME 49%, 77%, and 100%, respectively. PCC could not preserve their structural integrity, while the weight loss of SPC was found to be below 1% at the end of 1200 cycles. It was determined that SPC has better durability performance under long-term freeze–thaw effects than SC and PCC. [ABSTRACT FROM AUTHOR]

In construction, the proper selection of natural building stones and the prediction of their pathology are significant, with freeze-thaw action being a primary cause of deterioration. Testing for freeze-thaw durability, being labour-intensive and time-consuming, often conflicts with construction timelines. The proposed methodology estimates natural stone behaviour against frost damage using quicker laboratory tests (e.g., capillary water absorption). The use of natural stones with an open porosity exceeding 2 % is not advisable, as exceeding this threshold leads to losses in compressive strength of more than 10 % after 168 freeze-thaw cycles. This alternative evaluation through the capillary water absorption method provides a precise estimation of freeze-thaw durability, proving to be an instrumental tool for architects when selecting natural stones. • Capillary water absorption and porosity predict freeze-thaw durability. • Increased open porosity leads to higher strength loss after freeze-thaw cycles. • Variability in porosity size and distribution increases surface degradation. • Larger porosity sizes result in greater compressive strength reduction. [ABSTRACT FROM AUTHOR]

Application of carbon fibre reinforced polymer (CFRP) composites in strengthening of existing reinforced concrete (RC) structures has been widely accepted. However, the durability of adhesively bonded CFRP-concrete joint has not yet been fully investigated, which therefore paves the way to the topic addressed in this work: the durability of the joint in concrete elements strengthened with CFRP laminate using externally bonded reinforcement (EBR) technique. Concrete strengthened elements were kept in laboratory-controlled environments (approximately 20 °C/55 % RH, and water immersion at 20 °C), while others were kept outdoor to mainly promote natural ageing by carbonation, high temperatures, freeze-thaw attacks, and airborne chlorides. The results from durability tests after 4 years of exposure showed insignificant bond strength degradation but with a noticeable bond stiffness reduction, also, the stiffness degraded faster than the strength. Besides, environmental conversion factors of 0.75 and 0.95 were derived from a database of existing accelerated ageing test data and the natural ageing test data from the present work, respectively. • Durability of bond between EBR-CFRP laminate and concrete • Natural outdoor ageing versus laboratory accelerated ageing • Four years of ageing under natural and accelerated environments • Single lap shear test as mean of bond characterization • Environmental conversion factors as mean of the prediction of durability. [ABSTRACT FROM AUTHOR]

The present study has been developed to investigate the effect of freeze and thaw (F–T) cycles on the characteristics of highly rubberised asphalt materials to be used as impact-absorbing pavement (IAP) in urban road infrastructures. The tested samples were produced in the laboratory following the dry process incorporation. Two main types of crumb rubber particles in the range of 0–4 mm were used. Moreover, two types of binders, one warm and one cold, were utilised to prove the feasibility of cold-produced admixtures. The temperature range of the F–T procedure was comprised between −18 ± 2 °C (dry freezing), and 4 ± 2 °C (in water), and the cycles were repeated, on the samples, 10 times. At 0, 1, 5, and 10 cycles, the samples were tested with non-destructive and destructive testing methods, including air voids content, ITSM, ITS, and Cantabro loss. The waters of the thawing period were collected, and the pH, electric conductivity, and particle loss were measured. A consequent change in mechanical behaviour has been recorded between warm and cold produced samples. However, the tests found that the F–T cycles had limited influence on the deterioration of the highly rubberised samples. The loss of particles in the thaw waters were identified as being potentially caused by the temperature stresses. The research suggested various ways to optimise the material to enhance the cold-produced layer mechanical performances, aiming at a fume and smell-free industrialised solution and reducing the potential leaching and particle losses. [ABSTRACT FROM AUTHOR]

The durability of ultra-high performance concrete (UHPC) with initial micro-cracking subjected to coupled freeze-thaw and chloride salt (FT-CS) attacks was investigated. The initial micro-cracking was introduced under controlled condition in the laboratory by pre-tensioning the dog-bone specimens and unloading them at a target strain of 1500 με. The micro-cracked UHPC specimens were then submerged in a sodium chloride solution with the concentration of 4 wt % and subjected to freeze-thaw (F-T) cycles. The micro-cracked UHPCs exhibited excellent chloride penetration resistance as evidenced by the consistently low chloride ion concentration (generally less than 0.5%) and the limited penetration depth (not exceeding 6 mm) even after undergoing 300 cycles of the coupled FT-CS attacks. The tensile strength and compressive strength of the micro-cracked UHPC were improved by 28.0% and 18.3% at 200 F-T cycles, respectively. The improvement in the mechanical properties can be attributed to the self-healing effect which densified the fiber-matrix interface and the matrix. Secondary hydration and carbonation were confirmed quantitatively by thermogravimetric test and qualitatively by scanning electron microscopy test. However, the detrimental effects stemming from the coupled FT-CS attacks outweighed the beneficial effect of self-healing at 300 F-T cycles, resulting in a decline in mechanical performance. [ABSTRACT FROM AUTHOR]

Marl clays with varying levels of calcite content often exhibit more erratic behavior compared to other problematic soils, especially when exposed to repetitive Freeze-Thaw (F-T) cycles. It is crucial to prioritize the mechanical properties and durability of this particular soil variety as neglecting such characteristics can result in irreversible harm to the superstructures. This research focused on examining the utilization of lime and Nanoclay (NC) as stabilizers and Glass Fiber (GF) as reinforcement for natural marl soil. The study involved preparing samples with 6% lime and up to 1.5% NC, combined with varying amounts of GF ranging from 0 to 1%. The samples were cured for 7 and 28 days and subjected to 0, 1, 4, and 8 F-T cycles. Several Unconfined Compressive Strength (UCS) and Indirect Tensile Strength (ITS) tests as well as microstructural analyses including Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) were performed on the samples before and after being exposed to F-T cycles. Results showed that the application of GF enhanced the UCS and ITS of lime-NC-stabilized marl soil by creating interlocking zones between the particles. The addition of lime and NC shifted the behavior of the soil sample from ductile to brittle, while the inclusion of GF caused the soil to revert to ductile behavior, resulting in a decrease in secant modulus (E 50) and an increase in energy absorption capacity (E u) compared to samples without GF. Furthermore, incorporating GF along with lime and NC into the marl soil improved the F-T durability even after 8 cycles and resulted in reduced strength deterioration compared to the control sample. The optimum mixture was found to be 6% lime, 1% NC, and 0.75% GF, resulting in a noteworthy improvement of 6.5 times in the ITS and a slight decrease of 6% after 8 F-T cycles compared to the untreated marl soil. [Display omitted] • Glass fiber enhances the freeze-thaw durability of the lime-nanoclay-stabilized marl soil. • Inclusion of glass fiber and naoclay improves the mechanical properties of marl soil. • Glass fiber changes failure behavior to ductile state even after freeze-thaw cycles. • NC particles can effectively enhance the durability of the system. [ABSTRACT FROM AUTHOR]

Abstract Freeze-thaw cycles can cause considerable damage to porous materials and thus have an adverse effect on the durability of mortars and porous stone. To assess the behavior and frost resistance of two types of porous limestone, three commercially available repair mortars and four mixtures of laboratory-prepared repair mortars were subjected to freeze-thaw cycles according to EN 12371. During the test, samples of stone and mortar were bonded together and the weight loss was continuously monitored. The adhesion bond between the stone and the mortar was also observed during the cycles. Petrographic analysis and thin sections were also made before and after the freeze-thaw test. The pore size distribution (mercury intrusion porosimetry, MIP) of mortars and stones was also measured. The test showed that most of the repair mortars were damage more than porous limestone due to frost action. Two exceptions are two commercial available repair mortars. These mortars were able to keep the adhesion with the stone, and the frost did not modify significantly the cubic shape of the test specimens, only rounding of the edges was observed. All other samples were broken during the frost tests; stone/mortar interface was dismounted. Other typical damage features such as delamination, blistering, powdering, and granular disintegration were also observed leading to the gradual surface loss of the material. Our tests proved that low pozzolanic cement content in mortars decreases the material durability. According to the pore size distribution (MIP), the small pores (around 0.1 μm) control the weathering behavior of tested porous materials.

This article presents a methodology for calibrating an energy model to hourly measured temperature data with the goal assessing durability of a mass masonry tower in its present state and projecting the impact, that plausible retrofit scenarios may have on durability. The case study for this project is a load-bearing masonry structure constructed in 1867 which has been suffering from chronic moisture-related deterioration for much of its existence. The tower was instrumented to record relative humidity and temperature beginning in September 2017. Energy modeling software in combination with an optimization program was used to develop a calibrated model that could predict interior temperatures and relative humidity. Using the calibrated energy model, hygrothermal simulations were performed to see how changes to the interior ambient conditions affected the wall. The number of freeze cycles and moisture content were projected throughout the cross-section of the masonry compared to baseline conditions. [ABSTRACT FROM AUTHOR]

Flax fibres are of growing interest as a reinforcing fibre; however, they are susceptible to moisture and have demonstrated poor bond to conventional hydrophobic resins. Although there are multiple approaches to address these issues, research has heavily focused on their short-term performance. In this research program, the performance of flax fibre reinforced polymer (FFRP), manufactured using SiO2-impregnated flax fibre, is assessed for its short-term performance as well as its long-term performance when exposed to wet-dry (WD) and freeze-thaw (FT) cycles. Treated FFRP showed improved bond between the fibre and resin as well as resistance to fibre pull-out. It exhibited a tensile strength of 144 ± 15 MPa and a tensile modulus of 8.6 ± 0.35 GPa. When exposed to WD cycles, delamination between the fibre and resin were observed. The onset of statistically significant mechanical damage occurred after four WD cycles, with a final 3% reduction in strength and a 6% reduction in modulus post-exposure. When exposed to FT cycles, FFRP experienced cracking within the fibre, as well as delamination at the interface. The onset of statistically significant mechanical damage occurred after 50 FT cycles, which manifested as a final 5% reduction in tensile strength and 10% reduction in tensile modulus post-exposure. Regardless of treatment, FFRP demonstrated the same damage mechanisms as untreated variants. [ABSTRACT FROM AUTHOR]

Recent studies present the effects of freeze–thaw cycles (F–T) and porosity/cement ratio (η/Civ) on the strength and durability of chemically stabilized soils. However, the effects of η/Civ on strength and durability have not yet been studied for optimal conditions of compaction of silt-cement mixtures. Thus, this paper discusses the mechanical properties and durability of a chemically stabilized silt that undergoes freeze–thaw (F–T) cycles with rapid hardening Portland cement when molded in three compaction energies under optimal conditions (i.e. maximum dry density and optimum moisture content) using cement contents of 3–9% by weight. The results show a decrease in the split tensile and unconfined compressive strength of the mixtures when submitted to several F–T cycles, and an increase in the accumulated mass of loss (ALM) influenced directly by the η/Civ index. Freezing–thawing action may have weakened the effect of cement hydration products on filling in soil pores and bonding soil particles causing microcracks. The results also show that it is possible to establish a constant split tensile/compressive ratio of 0.16 regardless of the number of F–T cycles, the η/Civ index, and ALM. Nevertheless, the η/Civ index directly influenced the ALM, qu, qt, and also water absorbed by the capillary rise of all the samples. Finally, it was found mixtures that comply (in terms of durability at low temperatures and strength), requirements to be used in geotechnical constructions. [ABSTRACT FROM AUTHOR]

• The feasibility of waste concrete powder-based geopolymer reclaimed concrete was verified. • Carbonation depth, uniaxial compressive strength and dynamic elastic modulus of under different carbonation time were studied. • The changes of mineralogical phases and micromorphology characteristics of reclaimed concrete were analyzed. • The deterioration mechanism of carbonization and freeze–thaw-carbonization of reclaimed concrete was revealed. • It makes it possible to achieve the complete recycling of waste concrete. In order to realize the complete recycling of waste concrete, this paper used waste concrete powder (WCP), fly ash (FA) and granulated ground blast furnace slag (GGBS) as raw materials to prepared geopolymer, mixed with recycled waste concrete aggregates to prepare waste concrete powder-based geopolymer reclaimed concrete (WCPGRC). The WCPGRCs cured for 28 days were carried out carbonization test (group C-28d) and freeze–thaw cycle carbonization test (group DC-28d), and the WCPGRCs cured for 84 days were carried out carbonization test (group C-84d) to study their durability. The carbonation depth, uniaxial compressive strength (UCS) and dynamic elastic modulus (DEM) of three groups of WCPGRC under different carbonation times and different freeze-thawed-carbonation times were tested respectively. The mineralogical phases and micromorphology characteristics of WCPGRC before and after carbonization and freeze-thawed-carbonization were characterized through XRD and SEM. The results show that: (1) The carbonation depth of WCPGRC in groups C-28d, DC-28d and C-84d all increased with the carbonation time and freeze-thawed-carbonation time, and the maximum carbonation depth was 4.4 mm, 4.9 mm and 4.1 mm, respectively. (2) The UCS of C-28d increased by 9.7% from 39.11 MP to 42.56 MPa with carbonization time; The C-84d increased by 4.6% from 40.51 MPa to 43.31 MPa; The DC-28d first increased and then decreased with the increase of freeze–thaw-carbonization time, and the maximum UCS was 40.51 MPa on the 28th day. (3) The DEM of C-28d increased by 16.5% from 17.22GPa to 20.06GPa with carbonization time; The C-84d increased by 7.6% from 20.05GPa to 21.57GPa; The DC-28d first increased and then slightly decreased with the increase of freeze–thaw-carbonization time, the maximum DEM was 18.41 GPa on the 14th day. (4) Prolonging curing time increased the UCS and DEM, while freeze–thaw decreased the UCS and DEM of WCPGRC. (5) After the carbonization of WCPGRC, new carbonate crystals and geopolymer gels were generated, continued to fill the voids and cracks, making the overall structure denser. However, after the freeze–thaw-carbonization, the freeze–thaw cycle inhibited the geopolymerization, and the freeze–thaw damage intensified the carbonization, which reduced the structural integrity of WCPGRC. [ABSTRACT FROM AUTHOR]

Recycled aggregate concrete has obtained worldwide attention as an important part of sustainability. In the aspect of durability of recycled concrete under coupling multi-factors, a number of devices were designed and installed to investigate the durability of recycled concrete. In previous studies, the concrete specimen was tightened by the screws to apply a prestress with the jack, and then specimen was put in the devices for the durability test, which was difficult to operate and prone to stress loss. In this paper, in order to better research the durability of concrete under coupling multi-factors, we designed a coupling mechanism of alternated with loading and freeze-thaw cycles in salt-solution to replace the traditional mold loading to accurately simulate the simultaneous interaction of freezing thawing, corrosion and load. The coupling protocol was designed with repetitive load and 25 time’s freeze-thaw cycles alternately 2 times in the salt-solution, in which the maximum stress level (the applied stress to 28 days compressive strength) of repetitive load is 0, 40%, 70%. The specific operation was that specimens were loaded repetitively for the first time, then they were freeze-thawed in the salt-solution for 25 time’s cycles, after that, they were repetitively loaded again, and freeze-thawed in the salt-solution for another 25 time’s cycles. The experiment on compressive strength and microhardness of recycled concrete and natural concrete under coupling action was carried out. In the macroscopic test, compressive strength loss of each specimen was measured under the above mentioned coupling protocols. At the same time, the microhardness across the ITZs between the coarse aggregate and the cement matrix was measured before and after 50 freeze-thawing cycles for the control specimens. The macro test results showed that the stress level of the coupling action increased from 40% to 70%, the compressive strength loss of both recycled concrete and natural concrete increased from 1.8% and 71.3% to 27.2% and 100% respectively. It is implied that the durability of recycled concrete under coupling action is better than that of natural concrete, and the loading mechanism with high stress level will accelerate the deterioration of both recycled concrete and natural concrete. The micro test results showed that the microhardness values gradually increased with the increases of distance from the interface of natural aggregate and cement paste, the microhardness losses were 8.1% and 23.8% of the interface of both recycled aggregate and natural aggregate before and after the coupling action respectively. It can be seen that the interface transition zone was the weakest part of the concrete, and the decreasing rate of microhardness of the interface transition zone in natural aggregate specimens was faster than that of recycled aggregate after 50 time’s freeze-thaw cycles in salt-solution. The environmental scanning electron microscope (ESEM) test results indicated that the bond strength and plastic deformation ability of interface of natural aggregate are better than that of recycled aggregate before freeze-thaw cycles, while the ability to resist freeze-thaw at the interface transition zone of recycled aggregate was better than natural aggregate after freeze-thaw cycles. The related results can provide an insight into the long-term performance of recycled concrete subjected to harsh environmental conditions and thus to promote practical application of recycled aggregate concrete in the future. [ABSTRACT FROM AUTHOR]

The textural properties of a rock and the characteristics of its pore network are intrinsic variables to consider when investigating the resistance of rock to weathering. To establish the influence of these variables on the effectiveness and progression of weathering processes, two lithotypes of a limestone were analyzed with respect to their texture and porosity, and to their performance during artificial weathering experiments. The studied rock is Vicenza Stone, a bioclastic limestone with heterogeneous texture, variable grain size from fine to coarse, and high levels of open porosity (27–28%). Two sets of samples were obtained from a quarry, defining coarse-grained (CGV) and fine-grained (FGV) lithotypes of Vicenza Stone. Multiple techniques (optical microscopy, scanning electron microscopy, image analysis, mercury intrusion porosimetry, hygroscopicity, ultrasound, and water absorption) were used to characterize the texture and porosity of the limestone. The sample sets were subjected to freeze–thaw (UNI 11186:2008, Cultural heritage—Natural and artificial stone—Methodology for exposure to freeze-thawing cycles, 2008) and salt-crystallization (partial continuous immersion method with a Na2SO4-saturated saline solution) weathering experiments to investigate the processes and progression of mechanical and chemical weathering. Differences in freeze–thaw-induced micro-cracks and in the deposition of secondary micrite between the lithotypes show that the CGV has an overall higher susceptibility to freeze–thaw weathering than FGV. Salt-weathering processes induced micro-crack formation, material dissolution, and secondary precipitation, suggesting the simultaneous occurrence of mechanical stress and chemical dissolution–precipitation processes. FGV is more prone to salt-induced weathering than CGV, whereas CGV is susceptible to the wide thermal excursions of freeze–thaw weathering. [ABSTRACT FROM AUTHOR]

• Durability of EAF concretes under different exposure conditions up 3 years is studied. • Concretes with EAF slag and equivalent mixes with limestone or barite were compared. • Experimental investigation and microstructure of long-term properties were examined. • The use of EAF as an aggregate for concrete production must be carefully monitored. The durability of concrete mixes with EAF slag as aggregate (HS) is studied; mixes with limestone (HC) and barite (HAB) aggregates were used as reference for structural and heavy-weight applications, respectively. Compressive strength, elastic modulus, water penetration under pressure, wet-dry cycles, freeze-thaw cycles, influence of environmental condition and leaching tests were conducted. The results indicate that HS tends to present higher depth of water penetration under pressure, a slightly higher expansion, higher carbonation depth and similar compressive strength than reference HC. Should be payed attention to the formation of stain points on HS concrete surface subjected to wet-drying cycles. [ABSTRACT FROM AUTHOR]

• Influence of PCMs in concrete deck under combined freeze-thaw and chloride-ingress. • Microstructure-guided numerical simulation establishing macro-micro relation. • Significant increase in frost and chloride-durability in concretes with PCM. • Reliability-based probabilistic analysis shows significant gain in life of bridge. • Helps to tune dosage and transition temperature of PCMs to maximize life of bridge. Use of phase change materials (PCMs) to tailor the thermal performance of concretes by efficient energy storage and transmission has gained traction in recent years. This study incorporates microencapsulated PCMs as sand-replacement in concrete bridge decks and performs numerical simulation involving multiple interactive length scales to elucidate the influence of PCM-incorporation in concretes subjected to combined freeze-thaw and chloride ingress-induced deterioration. The simulations show significant increase in durability against combined freeze-thaw and chloride ingress-induced deterioration in concretes when microencapsulated PCMs are incorporated. In addition, a reliability-based probabilistic analysis shows significant increase in life expectancy of bridge decks with PCM-incorporation. The numerical approach presented here provides efficient means to develop design strategies to tune dosage and transition temperature of PCMs to maximize durability of concrete structures in regions that experience significant winter weather conditions. [ABSTRACT FROM AUTHOR]

• Determine the mechanical behavior of the original material used to build ‎the Ksour. • Study the addition of others natural local material to the original adobe. • Increase the SEB ‎ proprieties such as the waterproof and the durability. • Study the effect of chemicals attack's and environmental conditions on the SEB. The Ksour of south of Algeria, classified as a World Heritage of UNESCO, are earthen constructions, built with ancestral techniques. Although these techniques are widely used in the Saharan Desert region, very few studies hav approached them with scientific understanding. These old structures are known to suffer over time of damage due to difficult weather conditions. Several rehabilitation solutions have been established, but the problem remains considerable due to lack of information and knowledge on the behavior of these structures. Predominantly, their very complex architectural design and the materials used makes them very different in comparison to the most known masonry construction. These aspects are further discussed in the literature. This study contributes, primarily, to shed an understanding of the mechanical behavior of the original material used to build the Ksour. Secondly, to assess the impact of adding other natural local materials to the original earth materials in order to increase their proprieties, such as their waterproof performance and durability. These added materials must be able to adapt to these structures while respecting their originality in terms of architectural, color appearance and also their mechanical behaviors'. The obtained results show the effects archived by using different compositions on the durability of stabilized earth blocs from 28 days to 6 months' time scale. In total over 564 samples were analyzed during this study and their performances are presented. [ABSTRACT FROM AUTHOR]

Abstract The degradation mechanisms of bonded joints between CFRP laminates and steel substrates under severe environmental conditions require more durability data and studies to increase the database and better understand their causes. Studies on bond properties of double-strap CFRP-to-steel bonded joints with two different composite materials as well as adhesive coupons subjected to freeze-thaw cycles for 10,000 h were conducted to reduce that gap. In addition, the equivalent to the number of thermal cycles and their slips induced in the CFRP laminates was replicated by an equivalent (mechanical) loading-unloading history condition imposed by a static tensile machine. The mechanical properties of the adhesive coupons and the strength capacity of the bonded joints were only slightly changed by the artificial aging. It was confirmed that the interfacial bond strength between CFRP and adhesive is critically related to the maximum shear stress and failure mode. The interfacial bond strength between adhesive and steel degraded with the aging. However, the equivalent thermal cyclic bond stress caused no detectable damage on the bond because only the interfacial elastic regime was actually mobilized, which confirmed that pure thermal cycles aging, per se , at the level imposed, have a low impact on the degradation of CFRP-to-steel bonded joints. [ABSTRACT FROM AUTHOR]

Recycled aggregate concrete has obtained worldwide attention as an important part of sustainability. In the aspect of durability of recycled concrete under coupling multi-factors, a number of devices were designed and installed to investigate the durability of recycled concrete. In previous studies, the concrete specimen was tightened by the screws to apply a prestress with the jack, and then specimen was put in the devices for the durability test, which was difficult to operate and prone to stress loss. In this paper, in order to better research the durability of concrete under coupling multi-factors, we designed a coupling mechanism of alternated with loading and freeze-thaw cycles in salt-solution to replace the traditional mold loading to accurately simulate the simultaneous interaction of freezing thawing, corrosion and load. The coupling protocol was designed with repetitive load and 25 time’s freeze-thaw cycles alternately 2 times in the salt-solution, in which the maximum stress level (the applied stress to 28 days compressive strength) of repetitive load is 0, 40%, 70%. The specific operation was that specimens were loaded repetitively for the first time, then they were freeze-thawed in the salt-solution for 25 time’s cycles, after that, they were repetitively loaded again, and freeze-thawed in the salt-solution for another 25 time’s cycles. The experiment on compressive strength and microhardness of recycled concrete and natural concrete under coupling action was carried out. In the macroscopic test, compressive strength loss of each specimen was measured under the above mentioned coupling protocols. At the same time, the microhardness across the ITZs between the coarse aggregate and the cement matrix was measured before and after 50 freeze-thawing cycles for the control specimens. The macro test results showed that the stress level of the coupling action increased from 40% to 70%, the compressive strength loss of both recycled concrete and natural concrete increased from 1.8% and 71.3% to 27.2% and 100% respectively. It is implied that the durability of recycled concrete under coupling action is better than that of natural concrete, and the loading mechanism with high stress level will accelerate the deterioration of both recycled concrete and natural concrete. The micro test results showed that the microhardness values gradually increased with the increases of distance from the interface of natural aggregate and cement paste, the microhardness losses were 8.1% and 23.8% of the interface of both recycled aggregate and natural aggregate before and after the coupling action respectively. It can be seen that the interface transition zone was the weakest part of the concrete, and the decreasing rate of microhardness of the interface transition zone in natural aggregate specimens was faster than that of recycled aggregate after 50 time’s freeze-thaw cycles in salt-solution. The environmental scanning electron microscope (ESEM) test results indicated that the bond strength and plastic deformation ability of interface of natural aggregate are better than that of recycled aggregate before freeze-thaw cycles, while the ability to resist freeze-thaw at the interface transition zone of recycled aggregate was better than natural aggregate after freeze-thaw cycles. The related results can provide an insight into the long-term performance of recycled concrete subjected to harsh environmental conditions and thus to promote practical application of recycled aggregate concrete in the future. [ABSTRACT FROM AUTHOR]

The ever-increasing utilization of fiber-reinforced polymer (FRP) bars has led to a surge in research regarding their bonding properties with concrete. In this study, the bond durability behavior between high-strength fiber-reinforced concrete (FRC) and sand-coated basalt FRP (BFRP) bars was examined under three different environmental conditions including immersion in seawater solution at 50 °C for 3, 6, and 9 months, immersion in the sulfuric acid solution for 3, 6, and 9 months with an ambient temperature range of 20 to 30 °C, and exposure to 270 freeze–thaw cycles. A total of 60 pull-out samples were prepared using either basalt (B) fibers or polypropylene (PP) fibers. Plain concrete pull-out samples were served as controls. Test results revealed that all exposures have degraded the bond, leading to pull-out failure in all of the specimens. Exposure to 50 °C seawater was found to cause the most significant degradation. However, the use of basalt fibers helped to mitigate the loss of bond strength in the specimens when compared to plain concrete specimens. For example, after 3, 6, and 9 months of exposure to 50 °C seawater, bond strength retentions of 73.58%, 56.04%, and 34.47% were observed for basalt FRC (BFRC) specimens, compared to 39.64%, 49.37%, and 29.61% for plain concrete specimens. On the other hand, a lower retention in bond strength of 16.28% was recorded for polypropylene FRC (PPFRC) specimens at 9 months of exposure to 50 °C seawater. The bond stress-slip relationship of the tested bars was accurately predicted using two calibrated analytical models: the Eligehausen, Popov, and Bertero (BPE) model and the Cosenza, Manfredi, and Realfonzo (CMR) model. Notably, both models showed a strong correlation with the observed bond stress-slip relationships in the experiments. [ABSTRACT FROM AUTHOR]

This paper aimed to explore the mechanical properties of a cement-based material with carbon nanotube (CNT) under drying and freeze-thaw environments. Mercury Intrusion Porosimetry and Scanning Electron Microscopy were used to analyze the pore structure and microstructure of CNT/cement composite, respectively. The experimental results showed that multi-walled CNT (MWCNT) could improve to different degrees the mechanical properties (compressive and flexural strengths) and physical performances (shrinkage and water loss) of cement-based materials under drying and freeze-thaw conditions. This paper also demonstrated that MWCNT could interconnect hydration products to enhance the performance of anti-microcracks for cement-based materials, as well as the density of materials due to CNT’s filling action.

In outdoor applications, textile reinforced cementitious composites (TRCs) are susceptible to varying weathering conditions. To guarantee their performance during the entire life-time, it is necessary to evaluate the long-term behaviour. In this paper, the mechanical behaviour of reference specimens is compared to aged specimens, which are subjected to heat-rain and/or freeze-thaw cycles. Results show that subjection to heat-rain cycles leads to a larger degradation of the tensile behaviour compared to subjection to freeze-thaw cycles. Besides the macroscopic tensile behaviour, also the cracking behaviour is evaluated. Analysis shows that cracks are formed at lower stress levels after being subjected to environmental loading. [ABSTRACT FROM AUTHOR]

This paper investigates the severity of pothole problems, conducts a critical assessment of current maintenance practices, and identifies resources available for pothole repair based on the results from a questionnaire survey of six provincial transportation agencies in Canada. The survey outcomes indicated a greater percentage of moderate to highly severe potholes in the study area. Freeze-thaw cycles were identified as the most influential factor in pothole formation. A large portion of pothole repair operations are conducted in the summer period. The frequently used patching materials were conventional cold mix, hot-mixed asphalt, Quality Pavement Repair, and Innovative Asphalt Repair. The throw-and-go method is commonly used for pothole repair operations in all seasons. The durability of a winter-repaired patch is significantly less than that of summer. Raveling, edge disintegration, and cracking are the most concerning distresses of patch failure, which could be a result of inadequate stability, adhesion, cohesion, and stripping potential of patching materials. [ABSTRACT FROM AUTHOR]

This study examined the effects of freeze–thaw (FT) cycles on the flexural performance of reinforced concrete beams strengthened with externally bonded fibre-reinforced polymer (FRP) laminates fabricated using bio resins. Six large-scale beams including three retrofitted with bio resin-FRP, two with epoxy-FRP, and one control beam, were tested. A fully bio furfuryl alcohol (FA) resin derived from corn cobs and sugar cane, and a partially bio epoxidized pine oil (EP) resin, were investigated. Additionally, 40 FRP tension coupons fabricated with the bio resins and the epoxy resin were tested to assess the effect of FT cycles on their tensile properties. Specimens were exposed to 300 FT cycles over a period of seven months at a temperature range of +6 to −27 °C. The study showed that this aggressive FT regime did not have a negative effect on the ultimate capacities of the beams or the coupons. In fact, all the conditioned beams had peak loads between 7 and 17% higher than their unconditioned counterparts, which may be attributed to the additional curing of concrete during the thawing phase of the FT cycles by submersion in water. The FT conditioned beams with the FA and the EP resin FRPs had 22 and 25% higher yield loads and 25 and 31% higher ultimate loads, respectively, compared to the FT conditioned unstrengthened beam. [ABSTRACT FROM AUTHOR]

Scrap tyres are one of the most important wastes. They can be used in different ways because of their availability and their non-degradable nature. This paper aims to demonstrate their reuse through durability properties experimental assessment of lightweight concretes aged five years, incorporating rubber aggregates as partial replacement of 5%, 7.5% and 10% of coarse/fine and coarse aggregates. The effect of the rubber aggregates on the lightweight concretes durability has been analysed. Firstly, the water absorption was evaluated, and then the mass losses were measured through many tests: freeze-thaw, elevated temperature and attack by Na2SO4 and HCl solutions. Wetting-drying cycles were carried out in order to accelerate the aging of the studied lightweight concretes and to reduce the tests duration. It has been observed that the water absorption decreased with small rubber content. The mass losses of the mixes were almost depending on rubber aggregates content and size, and the exposures duration. [ABSTRACT FROM AUTHOR]

In this study, a novel coupling testing protocol with separated repetitive loading and freezing-thaw cycles in salt-solution is designed to simulate coupling mechanical loading and complex environmental effects on durability and deterioration of recycled aggregate concrete (RAC). The Micromechanical properties and porosity of RAC were also characterized by scanning electron microscopy (SEM) and microhardness. The results show that the number and width of cracks of RAC and NAC under freeze-thaw cycles obviously increased with the increase of alternating times of repetitive load and the compressive stress level. The compressive strength losses for both RAC and NAC increase with the increase of compressive stress level and alternative times of repetitive load. However, the compressive strength of natural aggregate concrete (NAC) became lower than that of RAC after freeze-thaw cycles. It was found that the freeze-thaw resistance of RAC seems even better than that of NAC under the same freeze-thaw attacks and cyclic mechanical loading. It indicates that after freeze-thaw cycles in salt-solution, the durability of RAC is better than that of NAC. On the other hand, the microhardness and SEM characterization results indicate that the interface transition zone (ITZ) was a weak part in both RAC and NAC, and the ITZ in NAC obviously deteriorated faster than that of RAC. [ABSTRACT FROM AUTHOR]

Although previous studies attested to the feasibility of using recycled aggregates from unseparated construction and demolition waste (UCDW aggregates) in unbound layers of road pavements, the degradation caused by compaction and freezing action under simulative conditions has not been investigated yet. To investigate the effects of these two sources of degradation on resilient modulus (RM), three UCDW aggregates were collected from different plants in the Turin area and compared with a natural (NAT) aggregate. Partially-saturated specimens of UCDW aggregates at the optimal moisture content (w opt ) and at w opt ±2% were prepared at the gyratory shear compactor with 30 and 100 gyrations, and by subjecting specimens to 0, 4 and 8 two-day freeze–thaw cycles from −18 °C to +20 °C. Brittle and weak components of UCDW aggregates (crushed concrete, bricks) generate fine particles in the first part of the compaction process (in the first 30 gyrations). Freeze–thaw action led to a clear increase in the resilient modulus of UCDW specimens compacted at w opt and w opt +2%. A similar trend in RM was observed in the case of NAT aggregate in similar moisture conditions, while both UCDW and NAT exhibited a slight decrease for some samples prepared at w opt −2%. Under more severe but non–simulative testing conditions such as those currently used to select conventional granular materials, UCDW aggregate exhibits lower performances than NAT aggregate. Conversely, when evaluated in more simulative test conditions, the behaviour of UCDW aggregate is comparable to that of NAT one. [ABSTRACT FROM AUTHOR]

The design of concrete durability is normally based on the assessment of its performance when subject to a single deterioration mechanism. In reality, concrete structures are subject to varying environmental exposure conditions which often results in multi-deterioration mechanisms occurring. The Nordic climate, with cold harsh winters, poses a severe challenge to the long-term durability of concrete. The most common deterioration mechanisms are freeze-thaw damage, carbonation and chloride induced corrosion. Research is now more focused on the assessment of coupled deterioration mechanisms. For instance, evaluating how cracks resulting from freeze-thaw influence chloride ingress, or how carbonation changes the surface properties and thereby influencing freeze-thaw scaling and chloride penetration. This paper presents the results of research projects at VTT focusing on coupling deterioration mechanisms. These research projects have built on several decades of concrete durability research at VTT, including 15 years of field station studies. The durability of the concretes has been assessed using both accelerated laboratory testing and also from in situ exposure results from field stations. This research has contributed to the development of concrete performance models and service life tools, supporting a holistic approach for deterioration assessment. [ABSTRACT FROM AUTHOR]

This paper examines the performance of concrete beams internally reinforced with basalt fiber-reinforced polymers (BFRP) bars after being subjected to freeze-thaw (FT) cycles. Prior to beam testing, pullout specimens were tested after being exposed to 100 and 200 FT cycles and to a freezing temperature of −20 °C. The pullout test results showed that FT cycles had a slight effect on the bond strength of the BFRP bars. Both unconditioned and conditioned specimens showed similar bond stress-slip relationships and comparable bond strengths. Exposing the pullout specimens to low temperature resulted in a decrease of 10% in their bond strength. In the beam tests, half of the beams were subjected to 200 FT cycles prior to testing whereas the remaining beams were tested at room temperature. The test parameters included the reinforcement ratio, the shear span-to-depth ratios, a / d , and the environmental conditioning. It was observed that conditioning changed the mode of failure of some of the tested beams as compared to that of their unconditioned counterparts. The effect of conditioning on the failure mode was less pronounced in the over-reinforced beams with a / d > 2.5. Conditioning under- and over-reinforced beams with a / d = 2.5 resulted in reductions of 7.4 and 13.4%, respectively, in their load carrying capacities. FT conditioning had a slight effect on the ductility of the tested beams regardless of their a / d ratio or their internal reinforcement. [ABSTRACT FROM AUTHOR]

This paper presents the results of a collaborative research project between Quebec's Ministry of Transportation and Ontario's Ministry of Transportation, which aimed at characterizing a new type of headed glass fiber-reinforced polymer (GFRP) reinforcing bar and evaluating its suitability as internal reinforcement for concrete structures. To achieve these objectives, the project was implemented in three stages: (1) evaluation of the physical and mechanical properties; (2) determination of the pullout behavior in concrete; and (3) characterization of the long-term durability of the headed GFRP bars. A total of 57 specimens embedded in a 200-mm concrete cube were tested with the direct pullout test to investigate the effect of confinement, bar size, concrete compressive strength, and exposure conditions on the pullout behavior of the headed GFRP bars. Simultaneously, microstructural analyses and measurements of the physicochemical and mechanical properties were carried out on conditioned and unconditioned headed GFRP bars. The results show that the materials, geometry, and interface configuration of the head provided very good mechanical interlocking to the GFRP bars. Up to 63 and 53% of the guaranteed tensile strength of the straight GFRP bars were achieved for 15.9- and 19-mm diameter bars with headed ends, respectively. Scanning electron microscopy and differential scanning calorimetry showed no material changes in the head and bars after exposure to alkaline solution and freeze-thaw cycling. Exposure to the alkaline solution under sustained loading had the most detrimental effect, with the bar retaining 79.4% of its pullout strength. The results indicate that the tested headed GFRP bar has suitable mechanical and durability properties for use as reinforcement in concrete bridge components. [ABSTRACT FROM AUTHOR]