Freeze-thaw Aging Research Articles

Simultaneous reduction and immobilization of Cr(VI) in seasonally frozen areas: Remediation mechanisms and the role of ageing

Among the toxic metals, hexavalent chromium [Cr(VI)] has attracted much attention due to its high mobility and toxicity, rendering considerable challenges for long-term remediation. In this study, the soil was collected from a dichromate contaminated industrial site in Liaoning Province, a seasonally frozen area in northern China, and subjected to frequent freeze-thaw cycles. Three additives, including (i) ferrous sulfate; (ii) calcium polysulfide; and (iii) combined biochar and calcium polysulfide were applied to reduce and immobilize Cr(VI) in the soils. The samples underwent 28 days of incubation followed by 16 freeze-thaw cycles. The toxicity characteristic leaching procedure (TCLP) and simulated acid rain leaching were adopted to test the remediation performances. It was observed that all three treatments can significantly reduce and immobilize Cr(VI) after short-term incubation, while biochar with abundant functional groups could adsorb and reduce Cr(VI) effectively. Notably, the concentration of Cr(VI) in TCLP leachates after incubation in combined treatment decreased by 67.87% and 37.27%, respectively, compared with the application of ferrous sulfate or calcium polysulfide alone. Freeze-thaw cycles induced the disintegration of soil particles and increased the risk of contaminant mobilization. Conversely, biochar particles has become finer and even produced nanoparticles with ageing, accompanied by the increase in oxygen-containing surface functional groups. Additionally, the specific surface area increased with the pyrolysis of biochar, which further enhanced the retention of soil colloidal particles and suppressed the migration of contaminants. Therefore, the cumulative release of Cr(VI) in the combined treatment (i.e., 10.97 ~ 32.97 mg/kg) was much lower than that of the other two treatments after freeze-thaw ageing. Overall, the combination of biochar and calcium polysulfide displayed advantages in the reduction and immobilization of Cr(VI), and offered a long-term, effective strategy for the remediation of Cr(VI) contaminated soils in cold regions.

Dry-wet and freeze-thaw aging activate endogenous copper and cadmium in biochar

Abstract While biochar is useful for environmental remediation, the effects of aging on the activation of endogenous trace metals in biochar remain unclear. In this study, three biochars with different concentrations of copper (Cu) and cadmium (Cd) were produced from the straws of Pennisetum sinese grown in moderately-polluted (MB), highly-polluted (HB), and clean (CB) soils. The effects of aging on biochar properties and bioavailability of endogenous Cu and Cd were investigated by Fourier-transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, Boehm titration, and chemical extraction before and after dry-wet (DW) and freeze-thaw (FT) aging. DW and FT aging increased the specific surface areas and abundance of oxygen-containing functional groups in the biochars. Aging decreased the biochar pH, degree of graphitization, and stability. The leachability of Cu and Cd were higher after FT aging than after DW aging, and the bioavailability of Cu and Cd were higher in MB and HB than those in CB. Aging increased the bioavailability of Cu in all biochars, whereas it only increased the bioavailability of Cd in MB. Aging increased the mobility of Cu and Cd by 2.31–12.2 and 0.22–1.31 times. The trends of the mobility and leachability of Cu were not consistent with those of total Cu in the biochars, while mobility and leachability of Cd and total Cd had the same trends. The activation of endogenous Cu was primary associated with the compositions of organic functional groups in the biochars. However, Cd activation was mostly related to the changes in the inorganic components and pH of the biochars. This study implies that aging can activate endogenous metals in biochars, and the potential environmental risk of a biochar should be carefully evaluated to ensure its safe and sustainable application.

Effect of aging on stabilization of Cd and Ni by biochars and enzyme activities in a historically contaminated alkaline agricultural soil simulated with wet-dry and freeze-thaw cycling.

Natural aging alters the surface physicochemical properties of biochars, which can affect the retention of heavy metals. This work investigated the effect of biochar aging on stabilization of heavy metals (Cd and Ni) and soil enzyme activities simulated with laboratory wet-dry (WD) and freeze-thaw (FT) cycling. A wheat straw (WS) biochar and a corn straw (CS) biochar were subjected to 30 WD or FT cycles, and Cd- and Ni-contaminated alkaline soils amended with the two fresh biochars (at 5% w/w) were subjected to 30-day constant moisture incubation and 30 WD or FT cycles. WD and FT aging caused slight reduction in the pH of the biochars, significant increases in their O contents and surface areas, and formation of new carbonate minerals. WS biochar was more effective than CS biochar at reducing the phytoavailable Cd in the soil, with reduction of 12.1%, 14.6%, and 12.9% under constant moisture incubation, WD aging, and FT aging, respectively. Reduction in phytoavailability of Ni by the addition of biochars was observed only under WD aging, by 17.0% and 18.5% in the presence of WS and CS biochars, respectively. Biochar amendment also reduced the distribution of Cd in the acid soluble and reducible fractions in all aging regimes. The addition of biochars decreased catalase activity in almost all aging regimes and invertase activity under FT aging, but increased urease activity under FT aging. Comparison of the enzyme activities in the soils amended with biochars under constant moisture and accelerated aging conditions indicates WD aging significantly decreased the activities of catalase, invertase, and urease in all treatments, while FT aging significantly increased urease activity in all treatments. These findings suggest that biochars can stabilize Cd in alkaline soils under changing environmental conditions, although the activities of some soil enzymes could be negatively impacted.

Transport and transformation of Cd between biochar and soil under combined dry-wet and freeze-thaw aging

We quantified the transport and transformation of Cd in historically contaminated soil (OS) and artificially contaminated soil (NS), treated with 3% (w/w) rice straw biochar prepared at 400 °C (BC400) and 700 °C (BC700) under combined dry-wet and freeze-thaw cycles for 72 days simulating the natural aging process of 8 years. An improved three-layer mesh experiment was developed to simulate the natural situation in field. The result showed that the total Cd concentration increased in the biochar but decreased in the soil, suggesting that Cd was transported from the soil into the biochar during the aging process. The total Cd concentration in BC400 treated with both soils was higher than that in BC700 treated with both soils, however, BC700 displayed stronger ability on immobilizing Cd than BC400 because the Tessier exchangeable Cd fraction in BC700 treated both soils was lower than that in BC400 treated with both soils. The average Tessier exchangeable Cd fraction in the soil and biochar decreased in all treatments during the aging process, indicating that Cd tended to be more stable in the soil for a long term. The result also showed that biochar could immobilizate Cd by decreasing the Tessier exchangeable Cd fraction of soil and biochar, and the quantitative contributions of biochar and soil to Cd immobilization were different in OS and NS treated with BC400 and BC700. The biochar contribution to the reduction in Tessier exchangeable Cd fraction accounted for 40–85% in NS treated with BC400 and 54–82% in NS treated with BC700. However, in OS treated with biochar, the biochar contribution accounted for nearly 100%, and soil had almost no contribution. In summary, OS did not contribute to Cd immobilization, while NS contributed nearly 50% to Cd immobilization, and BC700 was more effective in immobilizing Cd than BC400.

Durability and notch sensitivity analysis of environmental ageing induced glass fibre mat and kenaf fibre mat-reinforced composites

The durability of the notch and un-notch composites is mainly affected by environmental ageing, the condition of mechanical loading and mechanical ageing. Due to the dissimilarity of two components of fibre mat-reinforced thermosetting composites (e.g. fibre and resin), thermal stress and strain can be generated and raised by moisture, temperature variation, thermal ageing and mechanical ageing in any working environment. This study aims at investigating the effect of thermal ageing fatigue and mechanical ageing fatigue on the mechanical durability and notch sensitivity properties of glass fibre mat unsaturated polyester resin composites and kenaf fibre mat/unsaturated polyester composites. Tensile tests of smooth and notched specimens, low cycle tensile fatigue tests, dynamic mechanical analysis, stress distribution by point-stress failure criteria and notch sensitivity analysis were performed to both types of the specimens. Both composites were previously taken under up to 100 number of freeze-thaw ageing cycles (from −25 to + 58℃). It is found that the tensile modulus and un-notched strength of kenaf fibre mat/unsaturated polyester were decreased by 30 and 27%, respectively, which was more severe than that of glass fibre mat/unsaturated polyester composites. After the thermal ageing, notch (open hole) did not diminish the strength property of kenaf fibre mat/unsaturated polyester, and there was an absolute increase of characteristic distance (d0) which indicates the lower notch sensitivity of kenaf fibre mat/unsaturated polyester. Although glass fibre mat/unsaturated polyester had superior mechanical properties, after thermal ageing, while kenaf fibre mat/unsaturated polyester presented stable low cycle fatigue property, better energy absorption and notch sensitivity properties.

5S Multifunctional Intelligent Coating with Superdurable, Superhydrophobic, Self-Monitoring, Self-Heating, and Self-Healing Properties for Existing Construction Application

There is a constant drive to develop ultra-high-performance multifunctional coatings for existing construction used in modern engineering technologies. For these materials to be used in unsound infrastructure protections, they are required to present enhanced robustness while bearing functionalities to meet multiple uses. Single-function coating is not smart enough to provide satisfactory protection, and the preparation process of multifunctional materials is complex, costly, and provides poor durability. Thus, existing coatings are not suitable to generate an intelligent closed-loop protection system. Herein, we report an innovative 5S multifunctional intelligent coating (5SC) for existing construction materials with superdurable, superhydrophobic, self-monitoring, self-heating, and self-healing properties. The 5SC material showed highly durable superhydrophobic properties as revealed by the main failure tests of building materials including physical friction (abrasion, scratching), 100% tensile strain, photoaging (3000 h of ultraviolet (UV) aging), acid corrosion (concentrated hydrochloric acid and sulfuric acid), and freeze-thaw aging (salty solution). The coated surface was highly sensitive to pressure, with monitoring thresholds from 1 to 30 000 N per 0.01 m2. It showed an early heating rate as high as 6 °C/min while maintaining very good self-monitoring and ice-melting drainage performance to protect the existing structures. This novel composite material is suitable for constructions in extreme areas where corrosion and freeze-thaw damage can occur. This multifunctional material presents a very broad range of applications and development potential in the construction field.

Laboratory Assessment of Deteriorating Performance of Nano Hydrophobic Silane Silica Modified Asphalt in Spring-Thaw Season

In the seasonal frozen regions, freeze-thaw (F-T) damage is the main pavement damage, causing a variety of poor conditions in bitumen pavement, such as cracks, pits, potholes, and slush. In previous studies, we evaluated the effect of nano hydrophobic silane silica (NHSS) on the degradation of asphalt mixture under F-T cycles, and established the damage model of NHSS modified asphalt mixture in spring-thawing season. To gain more understanding of the influence of NHSS on asphalt in spring-thawing season, NHSS modified asphalt was systematically analyzed under F-T aging process in this study. The main research objective of this paper was to investigate the deteriorating properties of NHSS modified asphalt under Freeze-thaw aging process. Within this article, the physicochemical characteristics of NHSS modified asphalt were determined by using various laboratory tests, which included basic property test, dynamic shear rheometer test (DSR), Fourier transform infrared spectroscopy test (FTIR) and thermogravimetric analysis (TGA). The results showed that the incorporation of NHSS could inhibit the F-T aging process of asphalt. Moreover, the chemical composition and thermal stability of asphalt under F-T aging process was analyzed through FITR and TGA test parameters. The results illustrated that the sulfoxide functional groups content index was more suitable for evaluating the aging degree of asphalt in the spring-thawing season and the F-T aging process had a great impact on the thermal property of NHSS modified asphalt.

Changes in the physicochemical characteristics of peanut straw biochar after freeze-thaw and dry-wet aging treatments of the biomass

Effects of aging after pyrolysis were tested relative to the physicochemical characteristics of peanut straw biochar. Biochar was prepared at pyrolysis temperatures of 350 °C, 500 °C, and 650 °C; then, it was freeze-thawed and dry-wet aged. The physicochemical characteristics of the fresh and aged biochar were analyzed. The results showed that the pyrolysis temperature, ambient temperature, and humidity affected the physicochemical characteristics of the biochar. With the increase of pyrolysis temperature, the yield and surface acidic functional groups of the fresh biochar decreased, whereas the ash content, C content, pH, specific surface area, and mesoporous volume of the fresh biochar increased. The aging treatment increased the acidic functional groups content in the biochar and reduced the aromatic functional groups content, which decreased the pH value of the biochar. The aging treatment increased the specific surface area and pore volume of the biochar, and the effect of freeze-thaw aging was greater than that of dry-wet aging. The aging treatment also destroyed the complete shape of the fresh biochar, and reduced its stability. After the aging treatment, the C content of the biochar decreased, whereas the O content increased, due to oxidation of the biochar.

Mercury adsorption to aged biochar and its management in China.

Biochar is frequently applied for the reduction of mercury (Hg) migration in soil; however, most of the studies only focused on the adsorption capacity evaluation of fresh biochar. We investigated the Hg adsorption capacities of biochar prepared from wheat straw, corn straw, and sunflower seed shells. Biochar aging was simulated via natural aging, high-temperature aging, and freeze-thaw aging. The adsorption capacities of all the aged biochar were increased, and wheat straw biochar and seed shells biochar treated with high-temperature aging (wBC-Ha500 and sBC-Ha600) and corn straw biochar treated with freeze-thaw aging (cBC-Fta500) showed an observable improvement on the equilibrium adsorption amounts. The kinetics of the fresh biochar samples fitted the pseudo-first-order kinetic model and the pseudo-second-order kinetic model, while the kinetics of the aged biochar samples fitted the pseudo-second-order kinetic model. Biochar adsorption capacity increased with higher initial concentrations and increasing temperatures. Elemental analysis, Fourier-transform infrared spectroscopy (FT-IR) spectra, cation-exchange capacity (CEC), surface area (SA), zeta potential, and X-ray photoelectron spectroscopy (XPS) showed that the aging mechanism consisted of hydroxylation and carboxylation caused by the functional groups on the biochar surface. According to the different climatic zones in China, wheat straw biochar and seed shell biochar are suitable for the tropical zone and the subtropical zone, while corn straw biochar is more suitable for the cold and the mid-temperate zones.

Non-invasive analytical technique to address water uptake on stone surfaces: The implemented Contact Sponge Method (i-CSM)

Abstract The assessment of capillary rise rate is a recommended test in Cultural Heritage diagnostics to evaluate the evolution of stone textural properties and decay, and performances of conservation treatments. Beside laboratory tests, diverse non-invasive and non-destructive, in-situ methods were developed in order to establish the monitoring for monumental structures and decorative apparatus: Karsten tube, Mirowsky pipe and contact sponge methods (CSM). The comparison between the diverse techniques demonstrated high comparability between the datasets obtained with the CSM (UNI 11432:2011) and those recast with capillary absorption. However, the dataset collected with the conventional method is affected by high standard deviation due to several variables, mainly operator-dependent. The adoption of a pocket penetrometer, coupled with the use of a thicker sponge, aimed at parameterizing the load upon the surface. The implementations allowed a higher reproducibility of the measures, as well as the possibility of applying increasing pressures. In this study the i(mplemented)-CSM was adopted to test the adsorption behaviour of a set of ornamental stones (Macigno Sandstone, Breccia Aurora, Rosso Verona and Vicenza Stone) both un-weathered and weathered by freeze-thaw ageing and salt weathering. A correlation between the maximum open pore radius and an increase in water absorbance at higher loads was established. The preliminary promising results wait to be further validated on larger datasets.

Preparation and artificial ageing tests in stone conservation of fluorosilicone vinyl acetate/acrylic/epoxy polymers

AbstractIn this work, a series of fluorosilicone vinyl acetate/acrylic/epoxy (FVAE) polymers for protection of stone relics were prepared with different content of hexafluorobutyl methacrylate (HFBMA) by the seed emulsion polymerization process. Properties and structure of FVAE materials were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), and transmission electron microscopy (TEM). Viscosity, particle size, surface tension, gel content, adhesion and surface hardness of polymer materials were also determined. Surface morphology of the stone sample was observed by scanning electron microscopy (SEM). Compared with a commercial copolymer, ethyl methacrylate/methyl acrylate (EM/MA, Paraloid B72), protection ability of the prepared FVAE polymer was investigated using artificial ageing tests such as the freeze-thaw aging test, acid aging test and the soluble salts aging test. It was found that the FVAE polymers prepared can effectively prevent corrosion caused by H

Field and Laboratory Evaluation of Environmental Effects on Chip Seal Performance: Freeze-Thaw and Asphalt Aging

Abstract Chip seals generally deteriorate as a result of asphalt oxidation, wear and polishing of aggregates, bleeding, and raveling (loss of aggregates). In this study, two major environmental effects on chip seal performance, freeze-thaw, and asphalt aging were investigated based on laboratory tests and field distress survey. For freeze-thaw evaluation, laboratory chip seal samples were prepared for 18 combinations (6 aggregates X 3 asphaltic materials). A simple freeze-thaw protocol was developed and evaluation of freeze-thaw effect on aggregate types reveals that both the precoated and uncoated expanded shale lightweight aggregates perform comparatively very well against freeze-thaw. Evaluation of freeze-thaw effect on asphaltic material types reveals that CRS-2P, an emulsion performs significantly better than hot asphalts, namely PAC-15 and AC20-5TR. For aging evaluation, asphaltic materials were extracted from 15 (5 aggregates X 3 asphaltic materials) field test sections and increase in stiffness due to aging were determined using a dynamic shear rheometer. For each of the five aggregates, CRS-2P shows the lowest G*/sinδ, indicating minimum field aging susceptibility among the three asphaltic materials while AC20-5TR shows slightly higher G*/sinδ than PAC-15, indicating maximum field aging susceptibility. Overall field distress ratings of the CRS-2P sections (sum of distress ratings of all the CRS-2P sections) are better than those of PAC-15 and AC20-5TR. The overall distress ratings of PAC-15 sections are better than overall distress ratings of AC20-5TR. In case of aggregate types, precoated expanded shale lightweight test sections performed the best, while expanded clay lightweight sections performed very poorly. Both freeze-thaw and asphalt aging tests closely reflect field performances and it can be concluded that the freeze-thaw and aging performances can be used as effective tools for predicting long term chip seal performances.

Preparation and Sand-Fixing Property of a Novel and Eco-friendly Organic-Inorganic Composite

A novel guar gum/poly(acrylic acid)/loess (GG-g-PAA/loess) organic-inorganic composite used as chemical sand-fixing agent (CSFA) is successfully prepared in aqueous solution by polymerization guar gum (GG), neutralized acrylic acid (AA) and loess. The correlations between the content of prepared composite and the sand-fixing properties are investigated. The results show that the CSFA can significantly improve the compressive strength of the sand fixation specimens. Meanwhile, the sand fixation specimens have good thermal, freeze-thaw and UV-radiation aging stabilities to withstand the changes in temperature and strong UV radiation. Besides, the specimens treated with sand-fixing agent shows excellent water retention capacity.

A study of traditional Chinese wax–rosin adhesive

Wax–rosin adhesive made from beeswax and rosin is an ancient traditional Chinese adhesive widely used for joining and consolidating inlaid works during the Ming and Qing Dynasties. It is a dark yellow solid at room temperature, with a waxy surface lustre and a weak scent of plant resin, usually translucent or opaque, with an irregular shape when broken into fragments (Fig. 1). It can be easily removed mechanically and any residues can be cleaned with alcohol, demonstrating good reversibility without damaging objects such as jewellery, wooden objects, metal, lacquerware, and ceramics. This paper presents the adhesive properties of wax– rosin. Previous research [1] had revealed that the rosin concentration determines adhesive strength. If the ratio of the rosin to beeswax was too high, the adhesive became brittle. The optimum ratio of wax to rosin for stability against aging was determined experimentally, and the effects on adhesive strength of preparation time (the adhesive mixture was prepared by heating to 200°C with continuous stirring), purity of rosin and beeswax, and substrates for application, were studied. Results indicated that wax–rosin has the strongest adhesion when the preparation time is 40 minutes and that wax–rosin prepared from higher purity beeswax and rosin exhibits higher adhesive strength. Data from freeze-thaw aging indicated that beeswax with 95% purity (the best available locally) demonstrated better anti-aging properties than 70% purity beeswax, and that a higher proportion of beeswax had slightly improved the adhesive strength. Adhesive testing on metal, ceramic, and wood indicated that the tensile strength could reach 1 MPa even when the adhesive was applied onto smooth 黏蠟膠是中國一種由蜂蠟和松香製成的古老傳統膠

Newly Developed Adhesive Strength Test for Measuring the Strength of Sealant between Joints of Concrete Pavement

AbstractA new adhesive strength test (AST) was developed to determine the adhesive strength of joint sealant. A series of sealant thicknesses, displacement rates, and curing times was tested to determine proper AST testing parameters using self-leveling (SL) and non-self-leveling (NS) silicone sealants. A series of tests was conducted under varying moisture conditions. The results appeared to indicate that moisture may reduce adhesive strength. Drying-time tests were conducted to determine the approximate appropriate wait time between joint washing and sealant installation for 3.2 mm (1/8 in.) and 9.5 mm (3/8 in.) joints. A series of tests was also conducted on artificially aged sealants, which appeared to indicate that oven aging reduces adhesive strength for SL sealant. Non-self-leveling sealant, on the other hand, appeared to be largely unaffected by oven aging. Hot-water aging and freeze-thaw aging appeared to reduce adhesive strengths for both sealant mixtures.

Characterization of Materials with Repellents and Consolidants from a Historic Building

In order to study the feasibility of the rehabilitation of the building of the Palace of Riva Herrera (sixteenth century), in Santander, Spain, four types of natural stone found in the building have been characterized. The chemical, microstructural, physical, and mechanical properties have been obtained. Also, in order to evaluate the durability of the stones, a program of freeze-thaw aging has been completed. In parallel, the effect of four commercial water repellents and consolidants was analyzed by means of capillary absorption tests. The results showed relations between the durability and the open porosity of the different stones. The capillarity absorption coefficient can be applied as an indicator of durability. Also, all of the waterproofing treatments were shown to be effective, reducing the capillary absorption of the treated stones with respect to the stones not subjected to protective treatments by virtue of a delay in the capillarity process, this effect being greater in more porous material.

The long-term performance of cementitious composites reinforced with coir fibre

Effective prediction of the long-term performance of natural fibre-reinforced cementitious materials is vital for their application. In this study, coir fibres of two different average lengths were combined with cementitious materials and chemical agents to form coir fibre-reinforced cementitious composites (CFRCCs). The composites long-term performance was assessed and compared with two different accelerated ageing processes, i.e. a cement-saturated water ageing, and alternate freeze–thaw ageing. The flexural properties were compared with the properties of the reference mortar. Overall, the flexural strength of 400 days naturally aged CFRCC specimens was weaker than that of the reference mortar. The toughness and ductility of the fibre-reinforced specimens, however, improved. The cement-saturated water ageing method gave a precise prediction of the flexural strength development of 400-day-old specimens, and the freeze–thaw ageing method worked very well for the toughness performance estimation of CFRCCs.

The Creep Testing Apparatus (CRETA): A New Testing Device for Measuring the Viscoelasticity of Joint Sealant

Abstract A new device, the Creep Testing Apparatus (CRETA), has been developed for use in determining the viscoelastic properties of joint sealant. Creep tests were conducted on two types of silicone sealant: self-leveling (SL) and non-self-leveling (NS). The results appear to indicate that the silicone sealant tested is a linear viscoelastic material and that its creep response does not appear to be sensitive to temperature variations from 0 °C to 60 °C. Further creep tests were conducted under artificial aging conditions. Hot water aging appears to cause both SL and NS sealant to become softer and more ductile. Freeze-thaw aging did not appear to have an effect on the viscoelastic properties. Oven aging did not appear to affect SL sealant, but it did cause NS sealant to become stiffer. These results might be useful in a long-term joint performance model.