Wet Dry Research Articles

Effect of anionic polyacrylamide amendment on the climatic durability of solidified waste rock fine

In order to improve the climatic durability of solidified waste rock fine (WRF), anionic polyacrylamide (APAM) was innovatively introduced to amend solidified WRF in this study. The effects of APAM content, freeze-thaw (F-T), and wet-dry (W-D) cycles on the mechanical behaviors of solidified WRF were explored. After that, zeta potential, fourier transform infrared (FTIR) spectroscopy, and scanning electron microscope (SEM) tests were initiated to understand the behavioral mechanisms of APAM. The results show that APAM can significantly improve the mechanical properties and durability of solidified WRF, and there exist a threshold content of APAM (0.3%~0.8% in this study), beyond which the strength will decrease. The microscopic test shows that the bridging effect and the filming effect induced by APAM are considered to be the two decisive factors affecting the mechanical behavior of S-WRF. On the one hand, the linear APAM long chain enables the cohesion between particles to be stronger through ion bridging, on the other hand, the long chains cross-link with each other to form a network interwoven inside the structure, thus playing a microfabric reinforcement role and enhancing the crack resistance of the solidified matrix. In addition, life cycle assessment (LCA) further confirmed the advantages of using industrial by-products combined with APAM to amend solidified-WRF. These results provide a theoretical basis for using APAM as trace additives to mitigate climatic durability-related issues.

Effect of Wet‐Dry Cycles on the Loading–Unloading Damage of Granite

ABSTRACTInvestigating the effect of wet‐dry (W‐D) cycling on loading–unloading damage is crucial for ensuring the stability of granite slopes in mountainous areas prone to strong earthquakes. This study conducted a series of W‐D cycling and loading–unloading tests on granite samples, complemented by weight measurements, wave velocity assessments, and nuclear magnetic resonance (NMR) tests on samples subjected to W‐D cycling. The results indicated that W‐D cycling reduced the mechanical properties of granite and increased the irreversible strain, dissipated energy, and number of acoustic emission (AE) counts during loading–unloading. The increase in the number of W‐D cycles led to a significant rise in the number of small‐scale, intergranular, and transgranular microcracks and the gradual formation of middle‐scale and large‐scale microcracks. W‐D cycling weakened the granite because of crystal expansion and contraction as well as mineral dissolution, whereas loading–unloading damaged the granite through inconsistent deformation resulting from the varying hardness of different minerals. This study provides a foundation for understanding the formation mechanism of seismically cracked slopes under the combined effects of rainfall and earthquakes.

Performance of stabilized copper mine tailings with freeze-thaw and wet-dry seasonal cycles

Approximately 3.44 billion tons of copper mine tailings (MT) were produced globally in 2018 with an increase of 45% from 2010. Significant efforts are being made to manage these tailings through storage facilities, recycling, and reuse in different industries. Currently, a large portion of tailings are managed through the tailing storage facilities (TSF) where these tailings undergo hydro-thermal-mechanical stresses with seasonal cycles which are not comprehensively understood. This study presents an investigative study to evaluate the performance of control and cement-stabilized copper MT under the influence of seasonal cycles, freeze-thaw (F-T) and wet-dry (W-D) conditions, representing the seasonal variability in the cold and arid regions. The control and cement-stabilized MT samples were subjected to a maximum of 12 F-T and 12 W-D cycles and corresponding micro-and-macro behavior was investigated through scanning electron microscope (SEM), volumetric strain (εv), wet density (ρ), moisture content loss, and unconfined compressive strength (UCS) tests. The results indicated the vulnerability of Copper MT to 67% and 75% strength loss reaching residual states with 12 F-T and 8 W-D cycles, respectively. Whereas the stabilized MT retained 39%–55% and 16%–34% strength with F-T and W-D cycles, demonstrating increased durability. This research highlights the impact of seasonal cycles and corresponding strength-deformation characteristics of control and stabilized Copper MT in cold and arid regions.

Temporal changes in the mobility of As, Pb, Zn, and Cu due to differences in biochar stability caused by lignin content

Understanding biochar aging is a critical factor in predicting its long-term effects when added to soil. This study explores the complex links between lignin content in biochar feedstock and biochar stability during accelerated aging, including its influence on heavy metal mobility in soil. In this study, nine types of biochar based on fir (F), pine (P), and oak (O) sawdust were produced at 400 °C, and lignin was extracted from them using ammonia after 0, 3, and 7 days (named as 0FB, 3FB, 7FB, 0PB, 3PB, 7PB, 0OB, 3OB, and 7OB). Subsequently, each biochar was subjected to 25 cycles of wet-dry (WD) and freeze–thaw (FT) aging. The aged low-lignin biochars (7FB, 7 PB, and 7OB) released more dissolved organic matter (DOM) and contained more oxygen-containing surface groups on their surfaces than the high-lignin biochars (0FB, 0PB, and 0OB). The low-lignin biochars with high DOM leaching released 37–85 % more anionic arsenic (As) from biochar-amended soil after 25 cycles of aging than the high-lignin biochars. The stabilities of lead (Pb), zinc (Zn), and copper (Cu) were increased due to strong binding to surface functional groups on the low-lignin biochar. The acid-soluble fractions of Pb, Zn, and Cu were converted to organic-bound fractions as biochar aging progressed, with the degree of transformation being inversely proportional to the lignin content of biochar. This research highlights the crucial role of lignin in shaping biochar stability, and reveals how biochar stability impacts soil heavy metals speciation, opening new avenues for effective biochar-based environmental solutions and the promotion of soil health.

Assessment of Durability of Chemically Stabilized Soils Using Different Moisture-Susceptible Methods

The durability of chemically treated subgrade soils is important for pavement design life, and it is a major concern for transportation and defense agencies. Stabilized soil layers should retain strength and stiffness properties under wetting–drying-related durability cycles and moisture exposure. Many durability test methods, including wetting and drying, tube suction, and Engineer Research and Development Center’s wet-test methods, have been developed and used in several stabilization studies in the past. It is important to study and determine how these methods address the long-term performance of chemically stabilized soils with a focus on stabilizer permanency. Therefore, this research study conducted a comprehensive laboratory investigation using all three methods to assess the durability of stabilized soils as per the US Department of Defense protocols. Three types of soils, silty sand, clayey sand, and high-plasticity clay, and three types of stabilizers, vinyl acetate-ethylene (VAE) copolymer, Portland cement type I, and hydrated lime, were considered in this study. Silty sand, clayey sand, and high-plasticity clay soils were treated with VAE copolymer, cement, and lime, respectively. Results of cement-stabilized soil showed that it is unsusceptible to moisture fluctuations, whereas VAE-stabilized soil indicated its higher susceptibility to moisture variations. Both the ASTM wet–dry (W-D) test and tube suction test methods revealed that lime-treated clayey soil is moisture-susceptible. All three methods showed similar findings, with good agreement existing between tube suction and ASTM W-D tests for all combinations of soils and stabilizers considered in this study.

Shear Strength of Loess in the Yili Region and Corresponding Degradation Mechanisms under Different Cycling Modes

In the Yili region, China, complex environmental conditions induce repeated wet–dry (WD) and freeze–thaw (FT) cycles, deteriorating soil shear strength and producing frequent loess landslides. In this study, we collected soil samples from the Alemale landslide, Yili Prefecture and performed their triaxial shear tests with different numbers of WD, FT, and WD-FT cycles. In addition, we summarized the change mechanisms of loess mechanical properties and its deterioration, in the Yili region, under different cyclic effects. Subsequently, the test results under the three cycling modes were compared and analyzed, the differences in the deterioration effects of different cyclic conditions on loess were discussed in depth, and finally, a multiple linear regression model was established and the weights of single factors under the action of coupled cycles were analyzed. The results show the following: (1) Regardless of the confining pressure values, the principal stress evolution trends in soil samples under different cycling modes were generally consistent, i.e., after an initial increase, peak values were reached, followed by a final decline. (2) Under unconsolidated undrained (UU) conditions, shear strength values of all soil samples tested under the three cycling modes dropped after the first twenty cycles, exhibiting different evolution patterns. (3) Coupled WD-FT cycling most significantly promoted soil shear strength degradation, with less WD cycling effect, and FT cycling had the least significant effect; in all three modes, the first cycle had the highest contribution to this effect. From the perspectives of cohesion, angle of internal friction, and decay of shear strength attenuation, the coupled WD-FT cycling effect on soil shear strength could not be reduced to a simple single-factor addition–subtraction relationship. (4) Weight analysis of soil samples after WD, FT, and WD-FT cycling revealed that WD cycles in the coupled WD-FT cycling mode had the most significant impact on the shear strength attenuation of soil samples (contributing 57%), FT cycles had a medium impact (contributing about 33%), while the effect of the total number of cycles was negligible (about 10%). The research results provide experimental and theoretical bases for subsequent control of loess landslides.

Dynamic responses of a waste sludge modified by magnesium-cement-based multiphase cementitious material under influences of temperature and moisture cycles

This paper explores the influences of external stress and moisture and temperature cycles on the microstructure and dynamic responses (including the dynamic shear modulus G, damping ratio λ, and accumulative plastic strain εp) of a waste sludge that is modified by magnesium-cement-based multiphase cementitious material. Experimental results show that (i) freeze–thaw (FT), wet-dry (WD), and wet-dry-freeze–thaw (WD-FT) cycles significantly change the soil’s pore system. Intra-aggregate pores gradually evolve into inter-aggregate pores and cracks develop during moisture and temperature cycles. This leads to the degradation of the pore structure and decrease in the soil stiffness; (ii) during the progress of moisture and temperature cycles, the G decreases, and the λ increases. The effects of WD and WD-FT cycles on the G and λ are more significant compared to FT cycles. The G increases with the confining pressure σc while the λ is not sensitive to the σc. The relationships of the G and λ to the deviator stress σd are generally non-monotonic and the turning point of such relationships is influenced by the moisture and temperature cycles; (iii) the εp increases after moisture and temperature cycles and the development of the εp during cyclic loading gradually evolve from plastic shakedown to plastic creep. Predictive models based on decay laws considering stress states are developed to describe the changes in dynamic shear modulus and accumulative plastic strain.

Cracks evolution and micro mechanism of compacted clay under wet-dry cycles and wet-dry-freeze-thaw cycles

Desiccation crack is a significant factor contributing to numerous engineering and environmental disasters. Under complex climate conditions, soils undergo not only seasonal wet-dry (WD) cycle, but also freeze-thaw (FT) cycle, which can alter the structural characteristics of soil, and influence the formation and development of cracks. In this study, the laboratory WD cycle and wet-dry-freeze-thaw (WDFT) cycle tests were carried out on the compacted lean clay samples which were dried to different dryness degrees to analyze the formation and development of cracks under different conditions and to discuss the mechanisms involved from a microstructural perspective. A high-resolution camera and scanning electron microscope were utilized to capture pictures of the macroscopic cracks on the sample surface and microscopic pores within the samples at each stage, respectively. The quantitative analyses were then conducted on the macroscopic cracks and microscopic pores. The results indicate that, with higher dryness degree, the crack ratio and crack width of the sample decrease with consecutive WD cycles. The samples subjected to WDFT cycles exhibit a higher crack ratio, wider cracks, and a greater proportion of primary cracks compared to the samples subjected solely to WD cycles. With lower dryness degree, the crack ratio and crack width remain relatively unchanged after each WD cycle, mainly consisting of small, shallow, and densely distributed sub-cracks. The overall crack ratio of samples subjected to WDFT cycles is lower than that of samples subjected solely to WD cycles. This is attributed to the aggregation of aggregate particles during the drying process and the dispersion promoted by the wetting process. Additionally, under high drying degrees, the FT process stabilizes the aggregate structure, while under low drying degrees, the FT process promotes the dispersion, rearrangement, and even fragmentation of aggregates, resulting in differences in crack development between WD and WDFT at different dryness degrees. These research findings provide valuable insights into the study of soil crack evolution and its mechanisms under complex environmental conditions.

Influence of acid rain climate environment on deterioration of shear strength parameters of natural residual expansive soil

Shallow landslides often occur on expansive soil cutting slopes especially during continuous rainy, causing traffic disruptions and enormous economic losses. This study experimentally investigated the effects of acid rain climate environment on the shear strength parameters of natural residual expansive soil (NRES). Firstly, the effects of the acid rain (pH = 3, 5, and 7) and wet-dry (W-D) cycles (n = 0, 2, 4, and 6) on the shear strength parameters of the NRES were studied by the direct shear test. Secondly, the changes in the microstructure and mineral composition of the NRES was studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Finally, the mechanisms behind the shear strength loss of the NRES under acid rain and W-D cycles were considered. The direct shear test results revealed that acid rain and W-D cycles could accelerate the decline of shear strength of NRES, with the most apparent decrease under the first two W-D cycles. After two W-D cycles, the cohesion (c) of the soil samples under the acid rain with pH = 5 and 3 is 15.2 % and 31.2 % lower than that under the solution with pH = 7, respectively, while the internal friction angles (φ) of the soil samples decreased slightly. The results from XRD and SEM indicated the acid rain infiltration could cause different degrees of dissolution and leaching of free cementitious substances in NRES, resulting in the formation of loose structures with larger voids. This trend is more pronounced after the superposition of W-D cycles. Therefore, the integrity of the soil microstructure unit is reduced and the ability to resist vertical stress is weakened. In the direct shear test, the soil structure is more likely to form a shear fracture surface, eventually leading to the decline of shear strength.

Changes in abrupt alternations between wet and dry over the Great Lakes Region of Central Asia during the period 1976–2015

• GLRCA experienced an overall wetting trend. • Both D-W and W-D alternation events slightly decreased at the regional scale. • DWAA events decreased in 1976–1995 but increased in 1996–2015. • The variation of DWAA events was closely related to the dry and wet months. Under climate warming, the frequency of dry-wet abrupt alternation (DWAA) events was largely increased at the global scale. In this study, we identified DWAA events, including dry-wet (D-W) alternation events and wet-dry (W-D) alternation events, based on the Standardized Precipitation Evapotranspiration Index (SPEI) for the Great Lakes Region of Central Asia (GLRCA), and analyzed temporal and spatial variation of DWAA during the period 1976–2015. Over the entire study period, GLRCA experienced an overall wetting trend, and a heavy dry trend was mainly distributed in the southwest. Although both D-W alternation events and W-D alternation events showed a slight decrease at the regional scale, there were two clearly opposite trends between 1976 and 1995 and 1996–2015, with a decrease in 1976–1995 and an increase in 1996–2015. Spatially, the variation in the number of D-W alternation events and W-D alternation events exhibited a large heterogeneity. A significant increase in the frequency of D-W alternation events and W-D alternation events was observed in the southwest of arid climate zone, which may be attributed to the increased frequency of dry months and wet months in the region. This study in DWAA events is of importance to the implementation of water resources management, disaster prevention and mitigation policies in the GLRCA under the challenge of future climate change.

RESPON TANAMAN PAKCOY (Brassica rapa L.) TERHADAP APLIKASI KOMPOS AMPAS KELAPA DAN NPK MUTIARA (16:16:16)

The study aimed to determine the response of Pakcoy (Brassica rapa L.) to the Application of Coconut Dregs Compost and Pearl NPK (16:16:16). This study used a factorial completely randomized design consisting of two factors. The first factor is the provision of coconut dregs compost consisting of four levels, namely 0 g/plant, 150 g/plant, 300 g/plant, and 450 g/plant.The second factor is the provision of NPK Mutiara fertilizer (16:16:16) which consists of four levels, namely 0 g/plant, 4 g/plant, 8 g/plant, and 12 g/plant. The parameter observed was the Number of Leaves, Economical Wet Weight, Weight Dry, and Root Volume. The data were statistically analyzed and continued with the Difference Test Real Honest (BNJ) at the 5% level. The results showed that the interaction of coconut dregs compost and pearl NPK 16:16:16 have a significant effect on parameters Number of Leaves, Dry Weight, and Root Volume. Compost best treatment coconut dregs 450 g/plant and NPK pearl 16:16:16 12 g/plant. The main influence effect of coconut pulp compost was significantly on all parameters. The best treatment dose of coconut pulp compost is 450 g/plant. The main influence pearl NPK fertilizer 16:16:16 had a significant effect on all parameters. The best treatment of pearl NPK fertilizer 16:16:16 12 g/plant.

Bond degradation and EMI-based monitoring of CFRP to concrete interfaces exposed to wet-dry cycling

This study aims to examine the bond behaviour of CFRP to concrete interfaces that are exposed to wet-dry (WD) cycling and to explore the applicability of an electromechanical impedance (EMI)-based monitoring method for the bond via the use of piezoelectric transducers (PZTs). Single shear tests were performed on CFRP-concrete interface specimens subjected to a maximum of 360 WD cycles. WD cycling causes a shift in the debonding failure mode from cohesive failure within the concrete to a mixed mode of cohesive failure and adhesive failure. The bond capacity of the conditional specimens did not decrease significantly until 270 WD cycles, indicating that severe bond degradation occurred after 270 WD cycles. Moreover, a generalized method that yields representative evaluation results was applied based on the load response curve, and the bond slip relationship was proposed for the interfaces under WD cycling. In addition, an EMI method that is based on PZTs was employed to monitor the CFRP-concrete interface during exposure to WD cycling and single shear tests. It can be found that EMI monitoring can monitor WD cycling-induced bond degradation and interfacial debonding damage that occurs in single shear tests.

Durability Improvement of Biocemented Sand by Fiber-Reinforced MICP for Coastal Erosion Protection.

Soil improvement via MICP (microbially induced carbonate precipitation) technologies has recently received widespread attention in the geoenvironmental and geotechnical fields. The durability of MICP-treated samples remains a critical concern in this novel method. In this work, fiber (jute)-reinforced MICP-treated samples were investigated to evaluate their durability under exposure to distilled water (DW) and artificial seawater (ASW), so as to advance the understanding of long-term performance mimicking real field conditions, along with improvement of the MICP-treated samples for use in coastal erosion protection. Primarily, the results showed that the addition of fiber (jute) improved the durability of the MICP-treated samples by more than 50%. Results also showed that the wet–dry (WD) cyclic process resulted in adverse effects on the mechanical and physical characteristics of fiber-reinforced MICP-treated samples in both DW and ASW. The breakdown of calcium carbonates and bonding effects in between the sand particles was discovered to be involved in the deterioration of MICP samples caused by WD cycles, and this occurs in two stages. The findings of this study would be extremely beneficial to extend the insight and understanding of improvement and durability responses for significant and effective MICP treatments and/or re-treatments.

Effects of Grinding and Polishing on Surface Characteristics of Monolithic Zirconia Fabricated by Different Manufacturing Processes: Wet Deposition and Dry Milling.

To evaluate the effects of grinding and polishing on surface characteristics of monolithic zirconia fabricated by two different manufacturing processes. Two types of monolithic zirconia specimens, self-glazed zirconia (SZ) and conventional zirconia (CZ), were fabricated by wet deposition and dry milling, respectively. The specimens were randomly assigned into 4 groups (n = 10): as-sintered, ground, polished with a special zirconia polishing kit, and polished with a general-purpose ceramic polishing kit. Surface morphology and roughness (Ra ) were characterized, followed by one-way ANOVA analysis (α = 0.05). The as-sintered SZ exhibited a smooth surface with obvious different morphologies compared with the as-sintered CZ (Ra : 0.26 ± 0.05 μm versus 0.33 ± 0.10 μm). Ra of the ground SZ was significantly higher than that of the as-sintered SZ (p < 0.001) and the ground CZ (p = 0.011). For both SZ and CZ, Ra decreased significantly after polishing (p < 0.001), and there was no significant difference between the two groups with different polishing kits (SZ- p = 0.144; CZ- p = 0.322). Surface morphologies of SZ and CZ became similar after grinding and polishing. Monolithic zirconia SZ fabricated by wet deposition exhibited a smooth surface with specific patterns compared to the dry milled CZ. Grinding significantly changed the surface morphology of SZ and increased surface roughness of both zirconia specimens, which can be improved by polishing without being influenced by polishing kit selection.

Evaluation of a Wet Acid Scrubber and Dry Filter Abatement Technologies in Pig Barns by Dynamic Olfactometry

Livestock activities, in particular swine farms, are sources of odorant compounds that cause conflicts with the neighboring population. Beside the effects on the neighborhood, excessive odor emission can cause discomfort to farm workers. In this context the APPROAch project, aims to test the application of two different air cleaning technologies (a wet acid scrubber and a dry filter) to reduce dust, ammonia and odors, in naturally ventilated pig facilities. The aim of the present study is to evaluate, in a pig farm, the odor removal efficiency of the two tested abatement technologies, based on air samples analyzed by dynamic olfactometry. Odor sampling was carried out at a pig facility involved in the project and brought to the lab within 30 h from sampling, as established by the European Standard EN 13725:2004. Odor concentration was evaluated by dynamic olfactometry using an Olfaktomat-n 6 (PRA-Odournet B.V.—Amsterdam, The Netherlands). The results show that the wet acid scrubber prototype presents an average odor removal efficiency of 16%, whereas dry filter has from limited to no effect. This efficiency could be considered as a good result for a prototype even if further analysis, with longer sampling periods are needed.

Volume Changes and Mechanical Properties of Expansive Mudstone below Canals under Wet‐Dry/Wet‐Dry‐Freeze‐Thaw Cycles

The complex environment in northern China is the main reason for degradation of expansive mudstone below the canals, which resulted in instability and damage of canal slopes. In this study, a serial of laboratory tests was conducted to explore the volume changes and mechanical behaviors of expansive mudstone below the canals in Xinjiang. The experimental program includes wet‐dry (WD) and wet‐dry‐freeze‐thaw (WDFT) tests, volume measurement, and unconfined compression tests. The test results show that during the WD cycles, the volume changes of expansive mudstones with a higher dry range would be more significant. The freeze‐thaw process in the WDFT cycles resulted in a decrease of volume change ranges when the expansive mudstones had a relatively smaller dry range and a slight increase of volume change ranges when the expansive mudstones had a relatively larger dry range. In the meantime, the stress‐strain relationships of expansive mudstones with different dry ranges all presented strain softening under the cycles of WD or WDFT. The first cycle resulted in a significant decrease of failure strength. After seven WD/WDFT cycles, the failure strength of expansive mudstones with different dry ranges decreased by 37.2%∼59.1%. In addition, the freeze‐thaw process in the WDFT cycles promoted the softening of the stress‐strain relationships and aggravated the failure strength attenuation of expansive mudstones. Through this study, we expect to provide a preliminary basis for the construction and maintenance of expansive mudstone canals in Xinjiang.

Development of Bacterium for Crack Healing and Improving Properties of Concrete under Wet–Dry and Full-Wet Curing

Concrete cracking is inevitable, coupled with increased permeability, exacerbating the adverse impacts of atmospheric conditions and chemical attacks. Calcium carbonate precipitation resulting from certain microorganisms’ metabolism is a novel approach that can self-heal the cracks and improve concrete properties. In this study, the development and effect of bacteria Bacillus cohnii on crack healing, regained compressive strength after pre-cracking, sorptivity, water absorption, and concrete microstructures were investigated. For this purpose, a Bacillus cohnii bacterial concentration of 105 cells/mL was used as a water replacement in the concrete mixtures. Two methods subsequently cured the prepared concrete specimens: wet–dry (W-D) cycle and full-wet (F-W). In the wet–dry cycle, the cast specimens were immersed in water for 24 h and then kept at room temperature for 24 h, which was considered as one cycle; this process was repeated for 28 days. In the full-wet curing, specimens were immersed in water for 28 days. However, the curing water was changed every 24 h to facilitate the essential oxygen supply for bacterial activity to precipitate calcium carbonate. The results revealed that 90% and 88% surface healing was noticed in full-wet and full-dry pre-cracked specimens at 28 days.

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.

Performance of SiO2-impregnated flax fibre reinforced polymers under wet dry and freeze thaw cycles

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.

Comparison of Wet Process and Dry Process of Cement Manufacturing with Advantages and Disadvantages

In this paper we are discussing wet and dry process of Portland cement manufacture. Wet process minerals are wet ground to form a slurry and in dry process minerals are dry ground to form a powder like substance. In this paper, we are discussing the comparison between wet process and dry process with various advantages and disadvantages.