Water Repellent Treatment Research Articles

Influence of Water-Repellent Treatment with Silicon Resin on Properties of Concrete

Although studies on water-repellent properties of silicon resin (SR) on cement-based materials have received tremendous attention around the world in recent years, they mainly focus on individual properties of water-repellent concrete treated with SR such as strength and water permeability resistance. However, to date, a systematic and comprehensive investigation is missing. The current study therefore investigates the influence of SR on the durability properties of cementitious materials by adding SR emulsion into integral concrete mixture and coating concrete surface with SR. The microscopic and mechanical properties and the durability performance were tested on the integral SR water‐repellent concrete (C-ISR) and SR surface water-repellent concrete (C-SSR). The obtained results indicate that SR application has no impact on hydration reaction and corresponding composition of cement-based materials, while SR addition leads to a reduction in strength and early shrinkage of cement mortar because the added SR delays the hydration reaction. Water-repellent treatment via SR can significantly reduce the water permeability of concrete, which is more apparent for surface water-repellent treatment (SSR). Furthermore, the durability properties were investigated, and the results indicate that integral SR water-repellent treatment (ISR) possesses better properties than SSR, which suggests water-repellent treatment via surface coating as an effective means to improve concrete durability.

On the performance of film formers versus penetrants as water-repellent treatment of High-Performance Concrete (HPC) surfaces

A common way to conserve the aesthetic appearance of High-Performance Concrete (HPC) surfaces against e.g. undesired changes in colour is to apply water-repellent treatment. For this purpose, two types of treatment i.e. film former and penetrants are commonly employed, with film formers developing a continuous film on the surface, whereas penetrants line the near-surface pores of the substrate. In this paper, the performance of these two types of treatment – when subjected to artificial weathering (UV irradiation and humidity) – is assessed by colourimetry, static contact angle (CA) measurements, scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The obtained results revealed that both types of treatment led to hydrophobic properties by reducing the surface free energy (SFE) with the extent depending on the chemical functionalities of the used water-repellent agents. The film former successfully hindered water from extracting the soluble calcium-bearing constituents from the hardened cement paste and, thus, prevented the deposition of efflorescence onto the HPC surfaces. The smaller penetration depths of the penetrants due to the low permeability of the investigated HPC, on the other hand, most likely allowed for the formation of transport pathways into the bulk material allowing water to extract the soluble calcium-bearing constituents. Based on the provided experimental basis, the underlying mechanisms of water-repellent treatment when applied to HPC are highlighted and guidelines for the proper selection of surface treatment according to the protection desired are given.

Simulation of Water Movement in Layered Water‐Repellent Soils using HYDRUS‐1D

Core Ideas HYDRUS‐1D performed well for the water movement in layered water repellent soils. Two scenarios of silt loam/sand and sand/silt loam with water repellent soils, were applied. HYDRUS‐1D simulated infiltration parameters by differing two layered water repellent scenarios. Water repellency has many negative influences on soil water movement. However, simulations of water movement in layered water repellent (WR) soils are limited. Our objectives are to calibrate and validate the infiltration parameters and simulate water movement in layered WR soils based on ponded infiltration experiments conducted in wettable, slightly WR, strongly WR, and severely WR soils. Our experiments were conducted in 50‐cm long soil columns with two layer scenarios: Silt loam overlying (/) sand and sand/silt loam. For WR treatments, the surface soil was all 5 cm. For the wettable treatments, surface soils with thicknesses of 10‐ and 20‐cm layer sequences were added. Calibrations were conducted based on cumulative infiltration (CI), distance of the wetting front (Zf), and volumetric soil water content (θv) in the wettable and WR silt loam/sand treatments. Validations were conducted via eight additional treatments. The 12 WR layered soil treatments were selected for simulation. Three statistical parameters including the relative root mean square error (RRMSE), were used to assess the HYDRUS‐1D performance. The RRMSE for calibration and validation, ranged from 3.2 to 10% and 2.5 to 13.6%, respectively, confirming that HYDRUS‐1D was able to accurately describe water movement in layered WR soils. For the severely WR treatments, infiltration time reached 2800 h in silt loam/sand scenario and 1000 h in sand/silt loam scenario when water infiltrated to a depth of 35 cm. Overall, soil water repellency was more important than the interlayer position in regard to affecting water movement in layered soils, especially in the sand/silt loam scenario.

Water Repellency Decreases Vapor Sorption of Clay Minerals

AbstractAs soils become dry, water primarily exists as vapor that adsorbs to and desorbs from particle surfaces. The drying process also often enhances soil water repellency, yet the effects of repellency on soil water vapor sorption and exchange are not well understood. The objective of this study was to quantify the water vapor sorption dynamics of two minerals (Ca2+ saturated kaolinite and montmorillonite), in which water repellency was induced using two organic agents: cetyl trimethylammonium bromide (~4% by mass) and stearic acid (0.5%, 5%, 10%, 20%, and 35% by mass). Samples were then analyzed for water vapor sorption isotherms, solid‐water contact angles, organic carbon content, mineral surface morphology, hydrophobic functional groups (using Fourier transform infrared spectroscopy), zeta potential, and particle size distributions. The results showed that the water repellent treatments altered particle surface potentials and decreased surface areas relative to the controls. As a result, those samples adsorbed significantly less water and had less hysteresis between adsorption and desorption isotherms than the nontreated controls (p < 0.05). Differences in water adsorption were most pronounced for water activities >0.6, where hydrophobic compounds may have inhibited water vapor condensation, even at low concentrations. In contrast, solid‐water contact angles were small in montmorillonite treatments with <10% stearic acid, suggesting that low levels of hydrophobic compounds may have greater effect on vapor sorption compared to liquid water imbibition. Altogether, these results imply that repellency may reduce water retention in dry soils and enhance water vapor losses.

Fabricating durable, fluoride‐free, water repellency cotton fabrics with CPDMS

ABSTRACTThe demand for fluoride‐free and durable hydrophobic cotton fabric is dramatically increasing due to environmental and human safety concerns. The current approach to produce water repellent cotton fabrics is applying fluorocarbon compounds in topical treatments. However, the fluorocarbons employed in the water repellent treatments on cotton fabrics have environmental concerns and environmentally friendly technologies are desperately sought. Herein, we report a new approach of fabricating water repellent cotton fabrics with proper washing durability by using poly{dimethylsiloxane‐co‐[2‐(3,4‐epoxycyclohexyl)ethyl]methylsiloxane} (CPDMS) as a hydrophobic agent. Benefiting from formation of robust ether bonds between CPDMS and celluloses, the cotton fabrics could gain promising durability for daily laundry. The resultant cotton fabrics demonstrated simultaneously desired waterproofness (hydrostatic pressure up to 22 mbar), durability (hydrostatic pressure stabled at 12 mbar after five laundry cycles), and breathability. Moreover, the CPDMS modified cotton fabrics also exhibited robust physical property with tensile strength retention up to 73%. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46396.

Robust Water-Repellent Treatment of Cotton Fabrics with Polysiloxane Modified via Thiol-Ene Click Reaction

A facile and inexpensive way to prepare self-crosslinkable poly(dimethylsiloxane) (PDMS) for superhydrophobic treatment of cotton fabrics is reported in the study. Through thiol-ene click reaction between mercaptopropyltrimethoxysilane (MPTMOS) and vinyl-containing poly(dimethylsiloxane) (VPDMS), PDMS-g-TMOS can be simply and quickly synthesized. The trimethoxysilane group of PDMS-g-TMOS can react with hydroxyl group on cotton fabric and other -Si(OCH3)3 groups. The synthesized polysiloxane (PDMS-g-TMOS) was identified by FT-IR and 1H-NMR. The morphology of the treated cotton fabric was observed by SEM and XPS was used to analyze the elemental composition on the surface of cotton fabric. The analysis results indicated that the surface was fully covered with PDMS. Due to the low surface energy of PDMS and the rough surfaces of cotton fabric, the optimized water contact angle (WCA) and sliding angle were respectively 154°±0.4° and 14°±0.5°, indicating superhydrophobicity. Moreover, water spray test (AATCC Test Method 22-2010) was also applied to evaluate the water repellency of treated cotton fabric and a score of 90 was assigned according to AATCC Test Method 22-2010. The durability of treated cotton fabric was tested by 50 laundering cycles. The resultant WCA barely decreased and the score of water spray test dropped from 90 to 80, showing the reasonable wash durability.

Super water-repellent treatment of various cloths by deposition of catalytic-CVD polytetrafluoroethylene films

Polytetrafluoroethylene (PTFE), commercial name “Teflon,” films prepared by catalytic chemical vapor deposition (Cat-CVD), often called “hot-wire CVD,” are deposited on various cloths of cotton, cotton denim, nylon, and polyester. After deposition on such cloths, they show super water-repellent property without impairing breathability. The whole surface of fibers of these cloths is completely covered with PTFE layers which form reticulated sharp convex–concave network structures with a size of a few micrometers or less in pitch. The super water-repellent property can be seen even at the back side of the cloths when PTFE films are deposited only at the front side.

Super Water-Repellent Treatment of Clothing Fibers by Cat-CVD

Super Water-Repellent Treatment of Clothing Fibers by Cat-CVD

Masonry’s Resistance to Driving Rain: Mortar Water Content and Impregnation

Alongside well-researched themes such as water and moisture, the service life and function of masonry veneers are often compromised by precipitation combined with poor design considerations, execution, and selection of materials. Little research has been carried out on the subject of the impact of mortar consistency on masonry’s resistance to driving rain. Water-repellent (WR) impregnation is typically considered a quick fix when problems occur. Wall-panels of 1 m2 built with different flow table values for the mortar have been tested in a driving rain chamber, where both time-lapse videos and the measuring of penetrated water are used to evaluate performance. Subsequently, the panels were impregnated with the most common types of WR products and re-tested. The analysis shows that changing the mortar mix from dry to wet can decrease the penetration of driving rain by a factor of ten. The test results presented in this article show that mortar with low water content gives a porous interfacial transition zone (ITZ), thereby increasing the rate of water penetration. The tested WRs are found to be ineffective in increasing masonry’s resistance to high pressure driving rain. The results, combined with what is already known about WR treatments on masonry, call for careful consideration before applying such treatment. This proves especially true in countries with much driving rain followed by frequent freeze-thaw cycles.

Roughness, wettability and water absorption of water repellent treated recycled aggregates

Surface treatment techniques may improve the characteristics of recycled aggregates (RAs) for use in cementitious materials, possibly as an alternative to the energy and CO2 intensive high quality RA production process. In this paper, we investigate the effectiveness of two water repellent treatments (silane solution and paraffin wax) on the characteristics of different RAs in terms of porosity. We explored the relationship between roughness, porosity/surface area, and wettability of RAs on their water absorption (WA) kinetics. The long-term goal of the treatments is to reduce the water demand of concrete/mortar.We proposed a method to measure the roughness of coarse aggregates by optical interferometry. Contrary to popular belief, recycled concrete aggregates are as rough as crushed natural aggregates, and only red ceramic aggregate is less rough than natural aggregates. This technique combined with mercury intrusion porosimetry identified microstructural changes in the treated RAs. Silane was incorporated into smaller pores (<100nm) and caused a slight reduction in the total porosity and specific surface area of RAs. Paraffin wax also intruded into the RAs, filling larger pores (>100nm), and the wax significantly reduced the total porosity. Paraffin treatment formed a smoother surface and a thicker paraffin layer around the particles.We determined the water absorption kinetics using the standard 24h WA test with method adaptations in order to improve the accuracy and repeatability of the tests. Treated RA surfaces exhibited hydrophobic behavior but at the cost of efficiency. WA kinetics significantly changed after 2h.

Robust water repellent treatment for woven cotton fabrics with eco-friendly polymers

A new type of water repellent treatment for woven cotton fabrics is demonstrated by using environmentally friendly non-toxic polymers. As a result of the treatment, cotton fabrics also demonstrated resistance to water penetration due to hydrostatic pressure build-up. The treatment is achieved by sequentially coating the fibers with a polymer nanocomposite comprising a C-6 perfluorinated acrylic copolymer and silica nanoparticles and acetoxy-cure silicone (PDMS) resin. Water droplets were easily repelled with corresponding roll-off angles well below 20°. Even impinging small droplets (8µL) could be repelled with droplet roll-off angle of 17°. Additionally, treated fabrics were also able to hold a hydrostatic head pressure of 2.56kPa (equal to 26cm water column height) before leak. Performance of the hydrophobic cotton fabrics was tested by ultrasonic washing and wear abrasion tests. Hydrophobic fabrics resisted wear abrasion under 17.5kPa up to 30 abrasion cycles. Moreover, the treatment was made in such a way that the open porous structured was preserved allowing breathability. The ease of application technique, industrial scale availability of the low-cost polymers and the non-toxic ingredients would allow this fabric treatment to be implemented in large scale textile treatment facilities.

Nanomaterials for Conservation of Artistic Stones: Performance and Removal Tests by Laser Cleaning

In this work, nanomaterials were used as consolidants and protective layers for artistic stones. Synthetized nanocomposites were applied on marble and their performances as protective and water repellent coating were characterized. For the preparation of the novel nanocomposites, SiO2 and TiO2 nanoparticles were synthesized by laser pyrolysis and were dispersed in acrylic polymer and silicon-based resin. To evaluate the retreatability of water repellent treatments, the capability of laser to remove protective layers was explored. Laser cleaning tests with different working parameters have been carried out to optimize the effectiveness of the process. The effects of laser treatments on stone surfaces and on the applied nanocomposites were estimated by using confocal optical microscopy and Laser-Induced Fluorescence (LIF).

Waterproof, Ultrahigh Areal-Capacitance, Wearable Supercapacitor Fabrics.

High-performance supercapacitors (SCs) are promising energy storage devices to meet the pressing demand for future wearable applications. Because the surface area of a human body is limited to 2 m2 , the key challenge in this field is how to realize a high areal capacitance for SCs, while achieving rapid charging, good capacitive retention, flexibility, and waterproofing. To address this challenge, low-cost materials are used including multiwall carbon nanotube (MWCNT), reduced graphene oxide (RGO), and metallic textiles to fabricate composite fabric electrodes, in which MWCNT and RGO are alternatively vacuum-filtrated directly onto Ni-coated cotton fabrics. The composite fabric electrodes display typical electrical double layer capacitor behavior, and reach an ultrahigh areal capacitance up to 6.2 F cm-2 at a high areal current density of 20 mA cm-2 . All-solid-state fabric-type SC devices made with the composite fabric electrodes and water-repellent treatment can reach record-breaking performance of 2.7 F cm-2 at 20 mA cm-2 at the first charge-discharge cycle, 3.2 F cm-2 after 10 000 charge-discharge cycles, zero capacitive decay after 10 000 bending tests, and 10 h continuous underwater operation. The SC devices are easy to assemble into tandem structures and integrate into garments by simple sewing.

Carbonation of Water Repellent-Treated Concrete

Water repellent treatment has been considered an effective preventive method against water and aggressive ions penetration into concrete and consequently can improve the durability of concrete structures. In reality, many concrete structures are exposed to conditions with high risk of carbonation. In this contribution, one type of ordinary concrete had been prepared and surface impregnated by 400 g/m2silane cream and 100 g/m2and 400 g/m2silane gel. In addition, integral water repellent concrete was produced by adding 2% silane emulsion. Then, the specimens were exposed to accelerated carbonation for 7, 28, and 72 days. The effect of water repellent treatment on carbonation of concrete has been investigated. The results indicate that surface impregnation reduced carbonation depth of concrete under RH 70%, but integral water repellent concrete increased carbonation. Carbonation reaction started behind the hydrophobic layer in the surface-impregnated concrete. The coefficient of carbonation can be described better by a hyperbolic function of time. Treatment by 400 g/m2silane gel and silane cream showed better efficiency on reducing carbonation than usage of 100 g/m2. Coefficient of water capillary suction was decreased significantly by both surface impregnation and integral water repellent treatment. It is an effective method to protect concrete from water penetration into the material.

The Effect of Water Repellent Surface Impregnation on Durability of Cement-Based Materials

In many cases, service life of reinforced concrete structures is severely limited by chloride penetration until the steel reinforcement or by carbonation of the covercrete. Water repellent treatment on the surfaces of cement-based materials has often been considered to protect concrete from these deteriorations. In this paper, three types of water repellent agents have been applied on the surface of concrete specimens. Penetration profiles of silicon resin in treated concrete have been determined by FT-IR spectroscopy. Water capillary suction, chloride penetration, carbonation, and reinforcement corrosion in both surface impregnated and untreated specimens have been measured. Results indicate that surface impregnation reduced the coefficient of capillary suction of concrete substantially. An efficient chloride barrier can be established by deep impregnation. Water repellent surface impregnation by silanes also can make the process of carbonation action slow. In addition, it also has been concluded that surface impregnation can provide effective corrosion protection to reinforcing steel in concrete with migrating chloride. The improvement of durability and extension of service life for reinforced concrete structures, therefore, can be expected through the applications of appropriate water repellent surface impregnation.

Protective properties and durability characteristics of experimental and commercial organic coatings for the preservation of porous stone

Abstract The application of hydrophobic polymers to stone materials is an effective way to preserve stone artefacts and protect Cultural Heritage from decay. To improve the characteristics and performance of water-repellent treatments, and to avoid the use of harmful solvents, innovative solutions have been widely explored. As recent examples, organic nano-filled photo-polymerizable systems were proposed as free-solvent efficient protective coatings for porous stones. In this paper, the nano-filled coating, based on a methacrylate mixture matrix optimized in previous studies, was applied on two calcareous stone substrates, typical of Apulia Region ( Pietra Leccese , PL, and Pietra Gentile , PG). Its characteristic protective properties (in terms of water-repellency, chromatic modification, capillary water absorption, transmission of vapor water, penetration into the stone) were assessed and compared to the same characteristics displayed by two commercial organic water-borne hydrophobic coatings. Natural exposure and accelerated weathering tests were performed to estimate the long-term behavior of the coatings. The characteristic protective performance displayed by the experimental free-solvent photo-polymerizable coating was found greater than those recorded for the commercial organic products.

Influence of freeze-thaw cycles on properties of Integral Water Repellent Concrete

Service life of reinforced concrete structures usually was designed on the basis of one selected deteriorating mechanism as for instance carbonation, chloride penetration, and frost action. It could be shown in the meantime by numerous authors, however, that combined actions such as chloride penetration under mechanical load or chloride penetration in combination with freeze-thaw cycles may shorten the service life of reinforced concrete structures more than individual processes acting alone. We have found that chloride penetration is accelerated significantly by freeze-thaw cycles. Frost damage not only reduces mechanical strength and elastic modulus but migration of chloride is facilitated in the damaged pore structure. Chloride penetration can be retarded by the addition of silane emulsion to the fresh concrete. In this way Integral Water Repellent Concrete (IWRC) can be produced. Migration of water and ions dissolved in water can not be prevented by integral water repellent treatment but it is slowed down. The combination of damage mechanisms and the protective measures by integral water repellent treatment have to be taken into consideration in realistic service life prediction and design.

Water repellent treatment of cotton fabrics by electron beam irradiation

In this study, traditional dip-pad-cure (DPC) process and electron beam (EB) irradiation were used to graft cotton fabrics with fluorine containing chemical, 1H,1H,2H,2H-perfluorooctyl acrylate (PFA). The grafted cotton fabrics were characterized by FT-IR and SEM. The water repellent properties were measured by contact angle, hydrostatic pressure, and spry test. It was found that there was no significant difference between the grafted cotton fabrics with DPC and EB methods, and the treated fabrics showed good water-resistant properties. The grafted cotton fabrics also showed good washing stability. By measuring the bending rigidity and bending hysteresis, it was found that the cotton fabrics grafted with PFA became softer than untreated samples.

Water Repellency of Monument Soil Treated by Tung Oil

Earthen monuments exposed at archeological sites are afflicted by a series of diseases, such as shrinkage, cracking, and collapse, related to moisture evaporation or partially soaked in ground water. Water repellency treatment is a promising improvement to the durability of earthen monuments. To understand the hydrophobic mechanism of the soil treated by Tung oil, geotechnical tests, including permeability test and water repellency test, in the laboratory were conducted on clay soil sampled from a site where Da Bao’en Temple was in Nanjing, China. Test results indicate that Tung oil film coated on the soil particles could well decrease the surface tension and free energy, providing waterproofing property without obvious change in esthetic appearance. Laboratory tests indicate that Tung oil treatment decreases the hydraulic conductivity and increases the water repellency of the soil. Water repellent treatment with Tung oil provides a new approach for earthen monument conservation under humid weather condition.

Modelling the Influence of Hydrophobic Treatment on the Electrical Conductivity of Mortar and Brick

Abstract This study evaluates the suitability of electrical resistance-based moisture content measurements, which are known to guarantee reliable values for moisture contents of wood, when applied to selected mineral building materials with and without water-repellent treatment. For the testing specimens of cement – mortar and solid brick were produced – the water-repellent treatment for the mortar specimens was carried out both by internal hydrophobization and surface treatment, while the bricks were hydrophobized by surface treatment only. For the measurements of electrical resistance electrodes were inserted into the specimens. For this purpose a borehole was drilled and the measuring point at the tip of the electrodes was glued conductively into the material. The remaining outer part of the electrodes was sealed with electrically isolating glue in order to establish a conductive connection in the middle of the specimens only. After storage at different relative humidity, the electrical resistance of the specimens was recorded using data logging devices. Based on gravimetrically measured moisture contents resistance characteristics for each material were established. A satisfying accuracy resulting from the comparison between gravimetrically measured and mathematically calculated material moisture contents confirmed the suitability of electrical resistance based moisture content measurements for selected treated and untreated mineral materials.