Chloride Research Articles

Allosteric Cholesterol Site in Glycine Receptors Characterized through Molecular Simulations.

Glycine receptors are pentameric ligand-gated ion channels that conduct chloride ions across postsynaptic membranes to facilitate fast inhibitory neurotransmission. In addition to gating by the glycine agonist, interactions with lipids and other compounds in the surrounding membrane environment modulate their function, but molecular details of these interactions remain unclear, in particular, for cholesterol. Here, we report coarse-grained simulations in a model neuronal membrane for three zebrafish glycine receptor structures representing apparent resting, open, and desensitized states. We then converted the systems to all-atom models to examine detailed lipid interactions. Cholesterol bound to the receptor at an outer-leaflet intersubunit site, with a preference for the open and desensitized versus resting states, indicating that it can bias receptor function. Finally, we used short atomistic simulations and iterative amino acid perturbations to identify residues that may mediate allosteric gating transitions. Frequent cholesterol contacts in atomistic simulations clustered with residues identified by perturbation analysis and overlapped with mutations influencing channel function and pathology. Cholesterol binding at this site was also observed in a recently reported pig heteromeric glycine receptor. These results indicate state-dependent lipid interactions relevant to allosteric transitions of glycine receptors, including specific amino acid contacts applicable to biophysical modeling and pharmaceutical design.

Inducing α-Helicity in Peptides by Silver Coordination to Cysteine.

Short peptide sequences consisting of two cysteine residues separated by three other amino acids display complete change from random coil to α-helical secondary structure in response to addition of Ag+ ions. The folded CXXXC/Ag+ complex involves formation of multinuclear Ag+ species and is stable in a wide pH range from below 3 to above 8. The complex is stable through reversed-phase HPLC separation as well as towards a physiological level of chloride ions, based on far-UV circular dichroism spectroscopy. In electrospray MS under acidic conditions a peptide dimer with four Ag+ ions bound was observed, and modelling based on potentiometric experiments supported this to be the dominating complex at neutral pH together with a peptide dimer with 3 Ag+ and one proton at lower pH. The complex was demonstrated to work as a N-terminal nucleation site for inducing α-helicity into longer peptides. This type of silver-mediated peptide assembly and folding may be of more general use for stabilizing not only peptide folding but also for controlling oligomerization even under acidic conditions.

Numerical modeling of the behavior of concrete exposed to chloride ions by coupling age and mechanical stresses

This study proposes a quantitative examination of the issue of chloride ion infiltration in concrete under mechanical strain in a hostile setting while considering the influence of time, commonly referred to as the aging effect. The relationship between the diffusion coefficient and age, when subjected to specific levels of uniaxial or biaxial stresses for various W/C ratios, has allowed us to assess the concentration of chloride ions and the time needed for corrosion to begin through the coating layer in three dimensions. The numerical model results corroborate the notion that the corrosion process is affected by the fluctuation of the diffusion coefficient, which is directly linked to the age factor and the mechanical stresses exerted on the concrete. The model also emphasizes the extended distribution of chloride ion concentration at a certain depth, which is connected to the ratio of water to cement, influenced by the diffusion coefficient and the degree of mechanical stress in older structures.

Dynamic Marine Atmospheric Corrosion Behavior of AZ91 Mg Alloy Sailing from Yellow Sea to Western Pacific Ocean

In this work, the dynamic marine atmospheric corrosion behavior of AZ91 Mg alloy sailing from Yellow Sea to Western Pacific Ocean was studied. The corrosion rates were measured using the weight loss method. The microstructure, phase, and chemical composition of corroded samples were investigated by SEM, EDS, XRD, and XPS. The results show that the evolution of corrosion rates of AZ91 Mg alloy was divided into three stages: rapidly increasing during the first 3 months, then remaining stable for the next three months, and finally decreasing after 6 months. The annual corrosion rate of Mg alloy reached 32.50 μm/y after exposure for 12 months in a dynamic marine atmospheric environment, which was several times higher than that of the static field exposure tests. AZ91 magnesium alloy was mainly subjected to localized corrosion with more destructiveness to Mg parts, which is mainly due to the synergistic effect of high relative humidity, the high deposition rate of chloride ion, sulfur dioxide acidic gas produced by fuel combustion, and rapid temperature changes caused by the alternating changes in longitude and latitude during navigation. As the exposure time increased, the corrosion pits gradually increased and deepened. The maximum depth of the corrosion pit was 197 μm after 12 months of exposure, which is almost 6 times the average corrosion depth. This study provides scientific data support for the application of magnesium alloys in shipborne aircraft and electronic equipment. The results could provide guidance for the design of new magnesium alloys and development of anti-corrosion technologies.

Physico-chemical and correlation study of ground drinking water of Tonk district of Rajasthan (India)

This study investigates the qualitative analysis of groundwater obtained from the Tonk district of Rajasthan to determine its suitability as potable water. Around 321 ground drinking water samples were collected and analysed for various physico-chemical characteristics including pH, electrical conductivity (EC), total dissolved solid (TDS), HCO3−, F−, Cl−, SO42−, NO3−, Ca2+, Mg2+, total hardness (TH) and total alkalinity (TA) in Tonk district of Rajasthan (India). The groundwater in the region is a little alkaline and hard. The EC during the pre-monsoon period varies from 434 to 7271 µS/cm, while in the post-monsoon period, it ranges from 356 to 8871 µS/cm. TDS of samples ranged between 285 to 5090 mg/L in the pre-monsoon and 247 to 6140 mg/L post-monsoon seasons. Few samples have EC, TDS, and TH levels higher than the permissible limit, restricts its usage as drinking water. The water quality in the study area varies from soft-fresh to hard-brackish in both pre- and post-monsoon seasons. Anion concentrations in analysed samples followed the order: HCO3− > Cl− > SO42− > NO3− > F−. Notably, the Water quality index (WQI) results for all collected samples fall within the range of 4.55–96.83, indicating they are considered safe and suitable for drinking purposes. Water quality data was analysed by correlation study and geochemical processes. A strong correlation between the Water Quality Index (WQI) and fluoride levels is found in both seasons. The geochemical analysis shows that most of the samples are in the rock water interaction zone, with some in the evaporation zone due to the high content of chloride ions. The groundwater chemistry appears to be influenced by rock-water interaction and evaporation sedimentation. The molar ratio of Ca2+/Mg2+ denotes calcite dissolution and silicate weathering revealing enrichment of Ca2+ and HCO3− ions in aquifer.

Performance of limestone calcined clay cement (LC3) incorporating low-grade marine clay

Clay is a globally abundant material and can potentially be used as a cement substitute after calcination. Though kaolinitic clay exhibits notable reactivity, the potential of low-grade clay with relatively low kaolinite content remains underexplored. This study comprehensively analyzed the chemical and mineralogical composition of marine clays at various locations and depths in Singapore, assessing their feasibility for preparing limestone calcined clay cement (LC3). The hydration kinetics and microstructure development of LC3 pastes, incorporating calcined marine clay, were investigated by XRD, isothermal calorimetry, SEM, and MIP. Additionally, a mini-migration test was employed to investigate chloride ion diffusion in LC3 pastes. The results revealed that Singapore marine clays contain relatively low kaolinite content (16–20% by QXRD). Despite a 25% reduction of 28 days compressive strength compared to reference OPC, LC3 samples exhibited outstanding resistance against chloride penetration regardless of kaolinite content (<40%) or replacement level (LC3-70 or LC3-50). The chloride diffusion coefficient (LC3-50) is one order of magnitude lower than the OPC system. Overall, our findings broaden the selection of raw materials for LC3 preparation and underscore the robustness of LC3 to resist chloride penetration, irrespective of variations in the clay's quality or source.

Mn-doped nickel-copper phosphides as oxygen evolution reaction electrocatalyst in alkaline seawater solution

Compared with traditional water electrolysis, electrolysis of seawater has larger resources and a brighter future. However, seawater contains more elements that have greater corrosive effects on electrodes; especially chloride ions (seawater contains more chloride ions) have the greatest impact. The existence of the corrosion problem creates greater difficulties in electrolyzing seawater, further limiting the efficiency of the electrocatalyst for electrolysis of seawater. In this paper, we report a Mn-doped Ni2P/Cu3P as an environmentally friendly monofunctional electrode for seawater electrolysis, which was made by a simple hydrothermal phosphatization operation method. The experimental results show that Mn-doped Ni2P/Cu3P presents overpotential of only 161 mV for oxygen evolution reaction (OER) at iR compensation of 90 and a current density of 10 mA cm−2. It has a small Tafel slope (25.15 mV dec−1) and a large capacitance (9.58 mF cm−2 on 1 × 1 nickel foam), which exceeds most reported oxygen evolution activities of non-precious metal-based electrocatalysts for electrolysis of alkaline seawater. The performance of Ni2P/Cu3P was probably significantly enhanced due to Mn doping by some characterization means. Through Density functional theory (DFT) analysis, it is known that the doping of Mn gives a large enhancement in the adsorption energy of water when Ni2P/Cu3P is electrolyzed with seawater. This paper provides train of thought for the exploration of excellent electrocatalysts for electrolysis of alkaline seawater.

Electrodeposited ZIF-67 reinforced polypyrrole coating on ferritic stainless steel substrate with durable anticorrosion performance

The harsh acidic environment containing chloride ions has created serious corrosion hazards for ferritic stainless steels. Zeolitic imidazole frameworks (ZIFs) are a promising material for corrosion protection due to their microstructural and physicochemical properties. In this study, we proposed the electrodeposited ZIF-67 reinforced polypyrrole (PPY) coating (PPY/ZIF-67) for corrosion protection of 430 ferritic stainless steel (430SS). The morphology, microstructure, and anticorrosion behavior of the pristine PPY and hybrid PPY/ZIF-67 coating systems were characterized. The successful electrodeposition of ZIF-67 nanoparticles on the surface of the PPY layer resulted in a uniform distribution and a compact coating structure, which contributed to the overall uniformity of the coating and enhanced both the barrier and activity inhibition functions of the coating. The protective performance of PPY/ZIF-67 coatings was evaluated through electrochemical tests, the results indicated that the anticorrosion efficiency of PPY/ZIF-67 coating (with 0.4 mol/L pyrrole monomer content) reached to 99 %, and the coating demonstrated a durable corrosion protection ability (744 h) in 0.1 mol/L HCl solution. Such performance of can be attributed to the combined effect of the anodic protection provided by the inner PPY film, the active corrosion inhibiting properties of the ZIF-67 nanoparticle layer, and the hindrance of aggressive species by the compact coating structure over the prolonged service time.

Chloride Corrosion Process of Concrete with Different Water–Binder Ratios under Variable Temperature Drying–Wetting Cycles

In this paper, four water–binder ratios (w/b) of 0.29, 0.33, 0.39, and 0.46 were designed. A variable test temperature was implemented in the drying–wetting cycle test according to the temperature fluctuations in the actual service environment, and the constant temperature test was established as the control group. The mechanical properties and chloride corrosion resistance of concrete with different w/b ratios under variable temperature drying–wetting cycles, as well as the microstructure changes, phase composition, and damage mechanism inside the concrete, were investigated. The results showed that the mechanical properties of concrete increased first and then decreased with drying–wetting cycles increasing, whereas the chloride corrosion resistance continued to decline. A higher w/b exacerbated the deterioration of the concrete performance. A higher w/b increased the porosity, chloride diffusion depth, and chloride content, thus reducing the resistance of chloride corrosion. Compared with w/b = 0.29, the compressive strength, splitting tensile strength, mass, and relative dynamic elasticity modulus of w/b = 0.46 exposed to 60 drying–wetting cycles decreased by 54.50%, 52.44%, 0.96%, and 6.50%, respectively, while the porosity, peak chloride content, and erosion depth increased by 45.12%, 70.45%, and 45.00%. Compared with the drying–wetting cycle with a constant temperature, the cumulative damage caused by the drying–wetting cycle with a variable temperature was greater, resulting in more severe deterioration of concrete performance. The increase in the test temperature significantly accelerated the diffusion rate, penetration depth, and chemical binding capacity of chloride ions. After 60 drying–wetting cycles, the peak chlorine content and erosion depth of w/b = 0.46 under variable temperature cycles were 15.38% and 10.32% higher than those under a constant temperature, while the compressive strength, splitting tensile strength, mass, and relative dynamic elastic modulus were reduced by 7.76%, 14.81%, 0.33%, and 2.40%, respectively. Microscopic analysis confirmed that higher w/b and variable temperature cycles accelerated the decay of mechanical properties and the decline of chloride corrosion resistance. According to the numerical fitting analysis, the w/b should be 0.29~0.39 under the condition that the mechanical properties and chloride corrosion resistance of concrete are met.

Effect of a Hybrid Pumice–Portland Cement Extract on Corrosion Activity of Stainless Steel SS304 and Carbon Mild Steel A36

The change in the corrosion activities of SS304 and the carbon steel A36 were studied during their exposure for 30 days to hybrid pumice-Portland cement extract (CE), to simulate the concrete–pore environment. The ionic composition and the initial pH (12.99) of the CE were influenced by the reduction of Portland cement (PC) content, volcanic pumice oxides and alkaline activators. Because of the air CO2 dissolution, the pH decreased and maintained a constant value ≈ 9.10 (established dynamic ionic equilibrium). The CE promoted the passivation of both steels and their free corrosion potential (OCP) reached positive values. On the surfaces, Fe and Cr oxides were formed, according to the nature of the steel. Over the time of exposure, the presence of chloride ions in the pumice caused a localized pitting attack, and for carbon steel, this fact may indicate an intermediate risk of corrosion. The chloride effect was retarded by the accumulation of SO42− ions at the steel surfaces. Based on electrochemical impedance (EIS), the polarization resistance (Rp) and the thickness of the passive layers were calculated. Their values were compared with those previously reported for the steels exposed to CEs of Portland and supersulfated cements, and the hybrid cement was considered as a PC “green” alternative.

Modeling carbonation depth of recycled aggregate concrete containing chlorinated salts

The durability of recycled concrete is susceptible to degradation from both chloride salt attack and carbonation when exposed in service environment. The depth of carbonation in recycled concrete subject to chloride salt attack was studied here. This investigation assessed the effects of mineral admixture, replacement rate of recycled coarse aggregate, and quality of recycled coarse aggregate on the carbonation depth. The carbonation depth Recycled concrete was studied through accelerated simulated carbonation in the laboratory for 7d, 14d and 28d. Based on the results, the correlation analysis was conducted to investigate the relationship between depth of carbonation, mineral admixture, recycled coarse aggregate replacement rate, recycled coarse aggregate quality and the presence of chloride ions. The objective of this study was mainly to investigate the effect of internal chloride ions on the depth of carbonation of recycled concrete subjected to chloride salt attack. The study referred to previous academic research on carbonation in recycled concrete that had not been affected by chloride salts, and conducted a comparative analysis to identify the carbonation depth pattern in recycled concrete influenced by chloride salt exposure. The study discovered a negative correlation between the replacement rate of mineral admixture and recycled coarse aggregate and the carbonation resistance of concrete. Moreover, enhancing the quality of recycled coarse aggregate positively impacted the carbonation resistance of concrete. An improved model was developed that considers the effect of internal chloride salts on the carbonation depth of recycled concrete, in reference to the empirical prediction model presently available. The model demonstrated a high level of agreement with experimental outcomes, displaying an error range of between −4.32% and 8.27%. It enables an in-depth comprehension of the carbonation behavior of recycled aggregate concrete in an environment exposed to chloride salt attack. Based on the model, the service life of recycled concrete structures can be more accurately forecasted, which can provide a theoretical direction for enhancing the durability of engineering structure.

Effect of Micro-Cracks on Chloride Ion Diffusion in Concrete Based on Stochastic Aggregate Approach

For concrete structures in offshore areas, chloride ion erosion is one of the main factors affecting durability. It is crucial to evaluate the chloride ion permeability resistance of concrete structures. In this paper, a finite element simulation of the chloride ion diffusion process in concrete is conducted. A mass diffusion finite element model based on a random aggregate approach is established to investigate the influences of an aggregate, the interface transition zone, and micro-cracks on the chloride ion diffusion coefficients in concrete. The results show that the mass diffusion finite element analysis based on the exponential function model and the power function model can effectively simulate the chloride ion diffusion process in concrete. In addition, the data reveal that volume fraction and distribution aggregates considerably affect chloride ion diffusivity in concrete. Also, the interface transition zone significantly accelerates chloride ion diffusion in concrete. Moreover, this acceleration effect exceeds the barrier effect of an aggregate.

Effective In Situ Alkoxide Trapping by TMSX in the Presence of TPP Catalyst in Glycidol Acetal Rearrangements.

This study demonstrates a nucleophile-catalyzed, trimethylsilyl halide-promoted rearrangement reaction of glycidol acetals to form halogenated cyclic acetals. The acetal group has been activated selectively in the presence of trimethylsilyl cation, which is used as in situ-generated alkoxide trapping reagent. Nucleophilic chloride and bromide ions participate in addition reactions with epoxides predominantly via SN1-type epoxide opening, while non-nucleophilic iodide and triflate ions induce a positive charge at the epoxide carbon. A systematic investigation of acetal-initiated polyene cyclization of epoxy polyenes has been conducted using bicyclic epoxonium ions as transient intermediates. Unfavorable orbital orientation and other stereoelectronic factors hinder the much-anticipated polyene cyclizations. The potential of this method has been showcased through its application in the total synthesis of parvistone A, a chlorinated styryllactone.

Chitosan-based buccal mucoadhesive bilayer tablets enhance the bioavailability of tizanidine hydrochloride by bypassing the first-pass metabolism

Tizanidine hydrochloride (TZN) is an antimuscarinic agent used in the treatment of pain-related spasms, multiple sclerosis, and stroke-related spasticity. It has low oral bioavailability (40 %) due to excessive first-pass metabolism in the liver. The aim of this project was to enhance the systemic bioavailability of TZN by developing buccal mucoadhesive bilayer tablet formulations using chitosan salts with molecular weights of 136 kDa (7 cP) and 169 kDa (10 cP). Structural characterisation of chitosans and their salts was performed by FTIR, 1H NMR, DSC, TGA, and XRD analyses. Soluble chitosan salts, chitosan glutamate and chitosan chloride, for the adhesive layer, and insoluble ethyl cellulose for the impermeable backing layer were selected as polymers to fabricate the buccal tablets by direct compression method. The tablets containing TZN demonstrated high swelling and good mucoadhesion characteristics as well as released all the drug within 8 h. While TC10, formulated with 10 cP chitosan chloride, showed the highest swelling properties, TG10, prepared with 10 cP chitosan glutamate, exhibited the highest mucoadhesion. Chitosan glutamate tablets (TG7 and TG10) demonstrated better mucoadhesive characteristics and stability than chitosan chloride ones (TC7 and TC10) in the buccal medium based on the results of swelling and drug release studies. The permeability studies performed by Franz diffusion cell demonstrated that the amount of TZN passing through the bovine buccal mucosa was between 13.4 and 14.4 %. Stability studies conducted at 5 ± 2 °C, 25 ± 2 °C and 40 ± 2 °C for 6 months showed that no changes in the content uniformity and pH were observed. The in vivo comparative bioavailability studies in female New Zealand rabbits were performed and TZN-containing buccal mucoadhesive bilayer tablets fabricated with both chloride (TC10) and glutamate (TG10) salts of chitosan demonstrated three times higher bioavailability than the commercial TZN product (Sirdalud® oral tablet) administered by the gastrointestinal route.

High correlated color temperature artificial lighting impairs retinal pigment epithelium integrity and chloride ion transport: A potential mechanism for choroidal thinning

Among the environmental factors contributing to myopia, the role of correlated color temperature (CCT) of ambient light emerges as a key element warranting in-depth investigation. The choroid, a highly vascularized and dynamic structure, often undergoes thinning during the progression of myopia, though the precise mechanism remains elusive. The retinal pigment epithelium (RPE), the outermost layer of the retina, plays a pivotal role in regulating the transport of ion and fluid between the subretinal space and the choroid. A hypothesis suggests that variations in choroidal thickness (ChT) may be modulated by transepithelial fluid movement across the RPE. Our experimental results demonstrate that high CCT illumination significantly compromised the integrity of tight junctions in the RPE and disrupted chloride ion transport. This functional impairment of the RPE may lead to a reduction in fluid transfer across the RPE, consequently resulting in choroidal thinning and potentially accelerating axial elongation. Our findings provide support for the crucial role of the RPE in regulating ChT. Furthermore, we emphasize the potential hazards posed by high CCT artificial illumination on the RPE, the choroid, and refractive development, underscoring the importance of developing eye-friendly artificial light sources to aid in the prevention and control of myopia.

Investigation of iron dissolution mechanism in acidic solutions with and without dissolved CO2 – Part I: EIS measurements

ABSTRACT Aqueous CO2 corrosion of mild steel is one of the major problems in the oil and gas industry. While current understanding primarily focuses on cathodic reaction mechanisms, less attention has been given to the impact of aqueous CO2 on the anodic iron dissolution reaction. In contrast, the mechanism of iron dissolution in strong acidic environments has been thoroughly investigated. Among the reaction mechanisms found in the open literature, a multi-path mechanism was identified that could explain the iron dissolution in strong acidic sulfate solution; both in terms of steady state polarization sweeps and impedance data at various pH values and current densities. However, the role of aqueous CO2 in solutions containing chlorides on the mechanism of iron dissolution had remained an open question. The present study used electrochemical impedance spectroscopy (EIS) as the main technique, to study the mechanism of iron dissolution in strong acid chloride solution with and without the presence of CO2. Results showed that the presence of chloride ions (0.5 M) decreases the rate of iron dissolution by competing with hydroxide ions to adsorb on the metal surface, forming chloride-containing intermediate species that participate in the iron dissolution reaction. The resulting decrease in the availability of hydroxide intermediates, which are more effective at enhancing the reaction rate compared to chloride-containing intermediates, leads to an overall decrease in the rate of iron dissolution. While the presence of CO2 increases anodic current density, EIS investigation revealed that neither aqueous CO2 nor other carbonic species directly react on the bare metal surface to form adsorbed intermediates involved in the anodic reaction. EIS investigation suggested that aqueous CO2 may induce changes in the chemical composition of adsorbed species, rate constants, and surface coverage, thereby altering the kinetics of the underlying reactions.

Investigation on the mechanism of self-healing effect of cementitious capillary crystalline waterproofing material on concrete and enhancement of its resistance to chloride erosion

To enhance the compactness of concrete in coastal areas and impede the ingress of chloride solutions into the structures, Cementitious capillary crystalline waterproofing material (CCCW) was internal incorporated into concrete. This study employed one-dimensional chloride immersion diffusion tests and wet-dry cycle tests to emulate the deterioration of concrete under natural conditions due to chloride ions. The optimal dosage of CCCW was determined by conducting chemical titration to measure the chloride ion concentration at various depths within the specimens. Subsequently, the influence of incorporating CCCW on the compressive strength of concrete under chloride conditions was assessed. Finally, employing experimental methods such as MIP, SEM and EDS, the pores within cementitious materials and the formation of internal crystals was examined at a microscopic level. Research indicates that in chloride salt environments, the penetration of salt solutions can trigger the formation of spider silk biomimetic shape crystalline structures within the internal pores of CCCW. thereby enhancing the compactness of concrete to achieve a self-healing effect while preventing the intrusion of chloride salt solutions.

Physical-chemical and microbiological characterization of water destined to hemodialysis

This research evaluated the physical-chemical and microbiological parameters of water and dialysate in four distinct hemodialysis units located in the southeast region of Brazil. The physical-chemical parameters evaluated were pH, electric conductivity, turbidity, alkalinity, free chlorine, nitrate, fluoride, chloride, sulfate, sodium, potassium, calcium, and magnesium ion concentrations. Microcystin was also quantified. The microbiological parameters evaluated were the detection of total coliform, total heterotrophic bacteria count (THB), and the isolation and identification of microorganisms in pre-reverse osmosis treatment and post-reverse osmosis treatment water samples and dialysate. The nitrate, fluoride and THB levels found in the water samples may present risk to the patient under hemodialysis treatment. Microcystin was detected in one of the potable water samples. Microorganisms were identified throughout the hemodialysis of the entire water treatment system, with Ralstonia sp. being the most frequent. The presence of emergent pathogenic bacteria highlighted in this study highlights the necessity of microbiological monitoring of water destined for hemodialysis. Keywords: dialysate, hemodialysis, water treatment.

Preparation and performance research of ecological concrete using waste wood

To mitigate environmental damage from mineral aggregate extraction, bio-based materials have garnered research interest as potential replacements for natural mineral aggregates. This work utilized waste wood as filler to prepare lightweight foam concrete with thermal insulation, low-temperature and corrosion resistance properties. The feasibility of using wood aggregate-based foam concrete (WFC) was explored in terms of dry density, softening coefficient, compressive strength, thermal conductivity, chloride ion permeability, freezing resistance, and sulfate attack resistance. Results showed that simultaneous addition of waste wood aggregate (WA) and foam effectively reduced WFC bulk weight and thermal conductivity while enhancing water resistance. However, the porous morphology of WA and foam caused the reduction of mechanical properties. In terms of durability, the addition of WA can increase the energy absorption capacity when WFC is subjected to expansion stress, reduce the damage to the structure, and have an inhibiting effect on the cracking of WFC caused by sulfate attack and freeze-thaw cycles. Nevertheless, WA's high water absorption loosened the matrix in WFC's interfacial transition zone (ITZ), increasing harmful pores and negatively affecting durability. In addition, in order to predict the mechanical properties of WFC and the resistance to sulfate attack, this study established a function model for the relationship between the compressive strength (Maintenance specimens of the same age and Specimen of sulfate attack) and the WA dosage. In conclusion, The use of waste wood for the preparation of WFC is more advantageous and sustainable than conventional foam concrete for the insulation of precast walls and coastal structures.

A New Sustainable PPT Coating Based on Recycled PET to Improve the Durability of Hydraulic Concrete.

A new, sustainable polypropylene terephthalate (PPT) coating was synthesized from recycled polyethylene terephthalate (PET) and applied onto a hydraulic concrete substrate to improve its durability. For the first step, PET bottle wastes were ground and depolymerized by glycolysis using propylene glycol (PG) in a vessel-type reactor (20-180 °C) to synthesize bis(2-hydroxypropyl)-terephthalate (BHPT), which was applied as a coating to one to three layers of hydraulic concrete substrate using the brushing technique and polymerized (150 °C for 15 h) to obtain PPT. PET, BHPT, and PPT were characterized by FT-IR, PET, and PPT using TGA, and the PPT coatings by SEM (thickness), ASTM-D3359-17 (adhesion), and water contact angle (wettability). The durability of hydraulic concrete coated with PPT was studied using resist chloride ion penetration (ASTM-C1202-17), carbonation depth at 28 days (RILEM-CPC-18), and the absorption water ratio (ASTM-C1585-20). The results demonstrated that the BHPT and PPT were synthetized (FT-IR), and PPT had a similar thermal behavior to PET (TGA); the PPT coatings had good adhesion to the substrate, with thicknesses of micrometric units. PPT coatings presented hydrophilic hydrophilic behavior like PET coatings, and the durability of hydraulic concrete coated with PPT (2-3 layers) improved (migration of chloride ions decreased, carbonation depth was negligible, and the absorption water ratio decreased).