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Use of Surface Treatment Materials to Improve Concrete Durability
Abstract
The effectiveness of concrete surface treatment materials such as silanes, siloxanes, etc., in preventing concrete deterioration due to sulfate attack, carbonation, and chloride-induced reinforcement corrosion was investigated. The effectiveness of these materials in decreasing the sulfate attack was evaluated by measuring the reduction in compressive strength. The chloride diffusion in the coated and uncoated concrete specimens was also evaluated. The performance of these materials in reducing carbonation was studied by exposing the coated and uncoated concrete specimens to a saturated carbon dioxide environment. The reduction in compressive strength due to sulfate attack in the concrete specimens coated with silane/siloxane in conjunction with an acrylic topcoat was very low compared with that in the uncoated concrete specimens and those coated with other surface treatment materials, the chloride diffusion was also least in the concrete specimens coated with silane/siloxane followed by a topcoat. Among all the surface treatment materials tested, silane/siloxane with an acrylic topcoat and two-component acrylic coating were most effective in preventing carbonation of concrete. Furthermore, silane and silane/siloxane with a topcoat were effective in reducing chloride-induced reinforcement corrosion in in-service structures.
... The application of surface treatment to RC structures has gained increasing popularity both for protection of newly built RC structures and for upgrading of existing structures (Almusallam, Khan, Dulaijan, & Al-Amoudi, 2003;Dai, Akira, Wittmann, Yokota, & Zhang, 2010; Japan Society of Civil Engineers). The ease of application has been particularly attractive to the construction industry (Basheer, Cleland, & Long, 1998;Ibrahim, Al-Gahtani, Maslehuddin, & Almusallam, 1997;Ibrahim, Al-Gahtani, Maslehuddin, & Dakhil, 1999;Nanukuttan, Basheer, McCarter, Robinson, & Basheer, 2008;Raupach & Wolff, 2003;Schueremans, Van Gemert, & Giessler, 2007;Swamy, Hamada, Fukute, Tanikawa, & Laiw, 1995;Zhan, Wittmann, & Zhao, 2003). ...
... Considerable laboratory and field studies have been conducted to study the diffusion process in surface-treated concrete (Basheer et al., 1998;Ibrahim et al., 1997Ibrahim et al., , 1999Nanukuttan et al., 2008;Raupach & Wolff, 2003;Schueremans et al., 2007;Swamy et al., 1995;Zhan et al., 2003). Some researchers have investigated surface-treated concrete in the same way as untreated concrete for the sake of simplicity (Medeiros & Helene, 2009;Sadati, Arezoumandi, & Shekarchi, 2015). ...
... Although considerable effort has been devoted to quantifying the diffusion parameters of surface-treated concrete by saltwater immersion tests (Basheer et al., 1998;Ibrahim et al., 1997Ibrahim et al., , 1999Nanukuttan et al., 2008;Raupach & Wolff, 2003;Schueremans et al., 2007;Swamy et al., 1995;Zhan et al., 2003), only a limited number of studies have reported on their theoretical prediction. In this section, the experimental data from two saltwater immersion tests are analysed quantitatively with the RNA. ...
Reinforcement corrosion induced by chloride penetration is a major threat to reinforced concrete structures in marine environments. The use of surface treatments to improve the durability of reinforced concrete structures has drawn increasing attention in recent decades due to their cost-effectiveness and convenience in construction. However, current knowledge of a practical, durable design to protect surface-treated concrete structures from chloride-induced steel corrosion remains insufficient. On this account, a rapid numerical approach was developed in this study to analyse the chloride diffusion in bilayer materials. In this approach, the time-dependency was considered for the chloride diffusion coefficients of both the surface-treated layer and the underlying concrete substrate and for the surface chloride content. The validity of this approach was verified with the finite element method and the computation time was only one hundred-thousandth that of the latter. This proposed approach makes it feasible in practice to estimate the probability of corrosion initiation in surface-treated concrete structures via Monte Carlo simulation.
... The methods that may be used to achieve concrete durability as described above all have various advantages and disadvantages. Upon careful consideration, hydrophobic impregnation may be considered to be a very advantageous solution as it does not change the appearance of the concrete structure, does not require expert knowledge for application, is easy to apply, is a low-cost option, does not require support or restraint, and has documented efficacy [20,22,23] . A summary of relevant research studies conducted on the influence of hydrophobic impregnations on reinforced concrete is presented in Table 1. ...
... • Silane penetration depth Use of surface treatment materials to improve concrete durability (Ibrahim et al., 1999) [22] • Chloride profiles ...
... • Silane penetration depth Use of surface treatment materials to improve concrete durability (Ibrahim et al., 1999) [22] • Chloride profiles ...
The durability of a reinforced concrete structure or structural element relates to its capacity to withstand its exposure environment, without the need for major repair over its service life. Realising concrete durability may be achieved using service life design. Service life design methods are used to ensure sufficient resistance of concrete structures to the exposure environmental actions. Avoidance of deterioration is a highly favourable option for the service life design of new structures. Surface treatment of reinforced concrete using hydrophobic impregnation (e.g. using silanes) may effectively be used for both corrosion control and avoidance of deterioration of reinforced concrete structures susceptible to chloride-induced corrosion. However, further studies are required to generate the statistical data and input variables required for the calibration and validation of service life prediction models for silane-treated structures.
... Conversely, under a chloride penetration test, the silicon agent better improved the performance of the concrete compared with the water based acrylic. Another study by Ibrahim, et al., (1999) showed that using silane as a surface treatment material enhanced the durability of concrete that was fully immersed in a sulphate solution compared to sodium silicate. However, the sodium silicate was found to provide better protection against carbonation. ...
... Concrete cylinders coated with the water-based acrylic coating exhibited slightly less damage than that of the non-coated cylinders. This can be attributed to the fact that the acrylic solution acts as a curing and sealing compound, thus, protecting the concrete against its surrounding environment by partially filling the concrete surface pores and creating a thin membrane (Vipulanandan et al., 2011;Al-Gahtani et al., 1999;Radlinska et al., 2012). However, the acrylic solution did not provide an adequate protection to concrete since it was completely damaged after 2 months of exposure to physical sulphate attack, as shown in Figure 5.4. ...
Field experience with concrete exposed to sulphates has often shown that concrete can suffer from surface scaling above the ground level caused by physical sulphate attack. This type of attack has been ignored and, in some instances, confused with chemical sulphate attack. In addition, current standards that evaluate the performance of concrete under sulphate attack, only deal with the chemical aspects of sulphate attack. This lack of information has led to confusion and contradictory views regarding the mechanisms of concrete deterioration due to physical sulphate attack.
In the current thesis, the performance of concrete exposed to environments prone to physical sulphate attack was investigated. The effects of mineral additives, water-to binder ratio (w/b), along with various curing conditions on the performance of concrete exposed to physical sulphate attack was studied. In addition, the effectiveness of different surface treatment materials in mitigating physical sulphate attack on concrete was explored.
Results show that concrete can experience dual sulphate attack. The lower immersed portion can suffer from chemical sulphate attack, while the upper portion can be vulnerable to physical attack. Lowering the (w/b) ratio and moist-curing reduced surface scaling above the solution level since the volume of pores was decreased. Although partial replacement of cement with pozzolans also decreased the pore volume, surface scaling increased due to the increased proportion of small diameter pores and the associated growth of capillary suction and surface area for evaporation.
Epoxy- and silane-based surface treatment materials were found to be adequate for protecting both cured and non-cured concrete exposed to physical sulphate attack. However, it was found that adequate curing of the concrete before coating is important to eliminate the separation of the surface treatment based on bitumen and enhance the resistance of concrete to physical sulphate attack. Using a water-based solid acrylic polymer resin did not provide adequate protection of concrete against physical sulphate attack.
... Ibrahim et al., 1999; Dai et al., 2010). A greater alkali content in the concrete may result from the interaction between sodium silicate and calcium hydroxide (Eq. ...
Due to the rapid increase of urbanization, industrialization, and population, a significant mass of C&D debris is generated worldwide by both developed and developing nations. Numerous nations have already pushed for the recycling of C&D debris into aggregate, which conserves natural resources and minimizes the need for landfill space, among other benefits. Recycling aggregate is thought of as a sustainable use for construction and demolition waste. However, it has a larger ability for absorbing water, poor interfacial transition zones (ITZs), a weaker bonding capacity, and other uncertainties for which RA treatment is necessary. The impact of various treatment techniques on the characteristics of RAs was examined in this work. This research examines various RA treatment techniques, including immersion in hydrochloric acid, coating sodium silicate, immersion in hydrochloric acid and coating with sodium silicate, and CO2 curing. Analysis was done on the Influence of Treatment Methods on the Properties of Recycled Aggregates 36 mechanical and microstructural properties of various types of treated recycled aggregate. It was discovered that the sodium-silicate-coated hydrochloric acid solution is superior to conventional treatment procedures in terms of cost and sustainability. These improvements were made possible by the making of C-S-H gel, which strengthened the layer over RA as a result of chemical reactions with hydration products of calcium rich in the mortar layer of the RA. These reactions filled the holes and blocked the cracks on the RA surface.
... Among them, surface hydrophobization with silane and organic coating protection are particularly representative. M Ibrahim et al. found that concrete treated with silane experienced only an 8.3 % strength decrease after 130d of exposure to 3 % sodium sulfate, compared to an approximately 41 % decrease in untreated concrete [15]. Shen, L. tested three commercial silanes for protecting concrete surfaces in a 4 % Na 2 SO 4 corrosion solution over 48 freeze-thaw cycles. ...
... Concrete, being a porous material, facilitates the penetration of corrosive agents such as carbon dioxide, water, and chloride ion into its interior, leading to internal corrosion [3,4]. Moreover, the brittleness of concrete makes it prone to developing fine cracks. ...
This study investigates the effect of the water-based permeable crystalline material on the compressive strength, permeability resistance, freeze-thaw resistance, abrasion resistance, and chloride ion permeability resistance of concrete through multiple sets of experiments. The results illustrate that the water-based permeable crystalline material enhances the compressive strength of concrete by approximately 9% and enhances the permeability resistance by 42.9%. Due to the notably higher permeability resistance, the chloride ion permeability resistance of concrete correspondingly increases by 17.2%. Moreover, this material significantly mitigates the damage caused by the freeze-thaw cycles and abrasion, making concrete more suitable for various working environments.
... Pore-blocking coatings are applied on the concrete surface and penetrate into concrete and react with existing CaðOHÞ 2 ; as a result, it forms an insoluble collide silicate that blocks capillary pores in concrete surface (Pan et al. 2017b;Maravelaki-Kalaitzaki 2007;Franzoni et al. 2013). Despite some improvement in concrete durability, they cannot remarkably reduce the chloride diffusion coefficient (Dai et al. 2010;Ibrahim et al. 1999). The fourth coating classification is multifunctional ones. ...
Polymer cementitious coatings (PCCs) are among the well-known types of coatings that combine organic and inorganic coating advantages. Crack-bridging, breathability, scratch resistance, and low water absorption are the main attained mechanical and durable properties of cementitious coatings due to polymer modification. In this research, the effect of calcium stearate (CS) in PCC was investigated. For this purpose, in the first step, PCCs with different polymer-to-cement ratios (P/Cs) (up to 0.6) were manufactured to obtain the optimum ratio. Results exhibited that a 40% P/C ratio enhances the pull-off strength compared to the others. Then, various CS (2.5%, 5%, and 10%) of the cement weight was added to the selected PCC mix proportion (P=C ¼ 0.4) to assess new characteristics of novel multifunctional PCC. The mini-slump flow diameter test, pull-off strength, capillary water absorption, contact angle, microstructure, and rapid chloride migration test have been studied. The outcomes illustrated that adding 2.5% CS can improve the permeability and durability of PCC under capillary condition with the lowest negative effect on bond strength and flowability.
... However, some researchers questioned the beneficial effect of silicate sealers. Moon et al. [13] reported a negligible effect of sodium silicate on the chloride diffusion coefficient, sulfate resistance, corrosion potential and corrosion current density. Dai et al. [14] observed an inefficiency of sodium silicate in preventing chloride penetration and variable waterproofing efficiency related to the presence of cracks and timing of the impregnation procedure used. ...
The degradation processes in surface layers of cementitious composites can be mitigated either by optimizing of the material or by applying surface protection. In this paper, the effect of lithium silicate (LS) sealer is investigated. Water absorbance is studied on standard cement mortar; frost resistance and porosity are examined on two types of concrete (C30/37 and C50/60). The results indicate that LS impregnation improves the water absorbance only slightly and only in the case of short exposure to water; water absorbance was reduced by 15–25% immediately after applying the LS sealer, but the effect was negligible (2–8%) after 24 hours of immersion in water. Frost resistance was not affected by LS impregnation, but a significant improvement of mechanical parameters (flexural tensile strength and weight loss after 50 freeze-thaw cycles) was observed. The resistivity of the concrete surface was increased by LS impregnation by 36–40%, indicating the improvement of quality of the surface layer, while the porosity was practically unaffected.
... After 15 cycles the weight loss was 0.8%. Ibrahim et al. [48] proved that concrete applied to the silane surface hydrophobization is characterized by a total stability after immersion in a sulfate solution. In addition, Aguiar et al. [49] indicated that silicon protected concrete is characterized by a low performance. ...
... The formed insoluble silicate gel acts as a micro-filler, generating a compact and dense microstructure on the treated concrete surface. Subsequently, this affects many characteristics of concrete, such as a decrease in water absorption [7,8], chloride permeability [6,9], and carbonation depth [6,10]. Simultaneously, a noticeable increase in abrasion [11,12] and frost resistance [6] has been reported. ...
Protection of concrete against aggressive influences from the surrounding environment becomes an important step to increase its durability. Today, alkali silicate solutions are advantageously used as pore-blocking treatments that increase the hardness and impermeability of the concrete’s surface layer. Among these chemical substances, known as concrete densifiers, lithium silicate solutions are growing in popularity. In the present study, the chemical composition of the lithium silicate densifiers is put into context with the properties of the newly created insoluble inorganic gel responsible for the micro-filling effect. Fourier-transform infrared spectroscopy was used as a key method to describe the structure of the formed gel. In this context, the gelation process was studied through the evolution of viscoelastic properties over time using oscillatory measurements. It was found that the gelation process is fundamentally controlled by the molar ratio of SiO2 and Li2O in the densifier. The low SiO2 to Li2O ratio promotes the gelling process, resulting in a rapidly formed gel structure that affects macro characteristics, such as water permeability, directly related to the durability of treated concretes.
... It was found that the concentration and soaking time affected the properties of RCA significantly; with higher concentration and longer soaking time, the compressive strength of the RCA may be reduced [41]. Also, the sodium silicate treatment may introduce alkalis which increase the risk of alkali silica reaction [39,40]), as well the treatment is not able to improve chloride ions penetration [42]. Therefore, the treatment is not considered to ensure good durability properties of new concrete. ...
Poorer quality indicators than natural aggregates generally characterize recycled aggregates. This is due to the composition of the primary raw material (mostly demolition waste), the method of processing (crushing, sorting) and the typical character of the grains, which, in addition to the original grain of natural aggregate, also contains the original adhered mortar. The resulting grains are heterogeneous, characterized by lower strength, higher porosity, higher absorbency, or the presence of cracks. Improving the quality of these grains is one of the approaches to increase their potential for use in concrete. Several methods of recycled concrete aggregate (RCA) grain strengthening are being studied worldwide, the effect of which on the final quality of recycled aggregates and new concrete is different. The article describes and compares the methods in terms of their impact on selected properties of both. The comparative analysis is based on the collection of results presented in research publications. Based on the evaluation of the results, polymer emulsion treatment can be identified as the most effective way to improve RCA water absorption. Sodium silicate treatment came out the best to improve the compressive strength of concrete mixed with treated RCA.
... In the practice of conservative works, the treatments by water repellent products or mix of products, such as consolidant and hydrophobic formulations, have been considered suitable methods to improve the durability of exposed concrete surfaces [1][2][3][4][5][6][7]. Durability requirements comprise the maintenance of the load capacity, the efficiency of the building during the whole service life and the conservation of materials and surfaces. ...
Water repellent treatments and combined products such as consolidant and hydrophobic formulations have been considered suitable methods to improve durability-related properties of exposed concrete surfaces. Since buildings in urban context usually suffer decay due to carbonation-induced reinforcement corrosion, in this work the authors studied how this range of protective products can affect the carbonation process of the concrete with regard of the case study of Palazzo degli Affari in Florence. An accelerated ageing test by CO2 exposure was performed on concrete mock-ups realised with the same recipe of the original, in order to evaluate the laboratory performance provided by the considered treatments. The assessment of the carbonation resistance was made by analysing the performance of the product actually employed in the conservation intervention of the Palazzo and other commercial formulations. Finally, the experimental results returned by the untreated samples were used to validate the fully-probabilistic method proposed by the fib-Bulletin 34 to predict the development of carbonation depth.
... In most cases, scholarly publications define sodium silicate as an inexpensive and widely used sealer. Its use for surface treatment is reported to result in a reduction in water absorption or permeability [4][5][6][7], a reduction in chloride permeability [5,7,8] a reduction in the carbonation depth of cementitious composites [4,8,9] and at the same time in a significant increase of the abrasion resistance [4,10,11] and a slight improvement of frost resistance [8]. ...
The concrete has been and at the same time will be the most used construction material worldwide. It is exposed to various physical and chemical degradation processes that deteriorate its properties and shorten its service life in most applications. As most of the detrimental effects on concrete come from the ambient environment, the quality of concrete surface plays a key role in the overall concrete performance. It should be resistant to abrasion, free of microcracks and open pores to prevent ingress of water, aggressive solutions, and gases. To enhance the properties of the concrete surface, various approaches can be used. The treatment via silicate-based sealers is becoming increasingly popular in concrete technology, especially in preventing deterioration when exposed to highly aggressive environments. This contribution focuses on applying unconventional test methods (e.g. combined scratch/acoustic emission method) to detect the fundamental properties of the treated cementitious surfaces will also provide a new perspective approach of material testing, which may be in the future advantageously used in technical practice. The present combined scratch/acoustic emission test evaluation will provide an excellent insight into lithium silicate sealers’ physical behaviour on fine-grained cement-based materials during this test.
... It is widely known that the deterioration mechanism of reinforcement corrosion is complex and the influencing factors mainly include oxygen, moisture, chloride ion, and carbon dioxide. The ingress of these media can cause the depassivation of reinforcement, which leads to the cracking and spalling of the concrete protective layer (Hussain and Ishida 2012;Ibrahim et al. 1999;Zheng et al. 2019;Wang et al. 2021a, b;Isgor and Razaqpur 2004). When the oxygen content on the surface of the reinforcement is sufficient, the surface is more likely to rust. ...
One of the most important factors affecting the durability of concrete structures is reinforcement corrosion, which is caused by oxygen concentration. Therefore, it is important to investigate oxygen diffusion in cement pastes. However, current research on oxygen diffusion models of unsaturated cement pastes has led to unclear conclusions. In this study, we propose a single-pipe oxygen diffusion model that considers five diffusion mechanisms: surface, Knudsen, transition, bulk, and water curtain. Further, a three-stage method is used to set up the model, and the division mode of this method is based on the mean free path (MFP) and the Mohycan model. The accuracy of the model is verified by comparing the calculated results with the experimental data. The proposed single-pipe model can be used to further analyze the durability degradation of reinforced concrete structures caused by steam, carbon dioxide, and other gases in the atmospheric environment.
... Many studies, including Brown (1981) and Ibrahim et al. (1999), examined the change in compressive strength as a main parameter to assess the resistance of cementitious materials to sulfate attack. In this study, the changes in compressive strengths of the mortars over 180 days of MgSO 4 exposure were monitored. ...
Fly ash-based geopolymer is an attractive supplemental cementitious material that has been receiving great attention from the community; however, its durability characteristics such as resistance to sulfate-related damage have not yet been fully examined. This study investigates the properties of fly ash-based geopolymer and its counterpart, Type V portland cement paste/mortar, when they are exposed to MgSO4 solution. Toward that end, a multiscale characterization was conducted. Changes in nanomechanical properties due to MgSO4 exposure were tracked and quantified by nanoindentation. Scanning electron microscopy and energy-dispersive X-ray spectroscopy were coupled to characterize microstructural and chemical changes at different MgSO4 exposure levels. Moreover, the effect of MgSO4 solution on macroscale properties, including changes in mass and compressive strength, were examined. Results indicated that exposure to MgSO4 solution affected the two cementitious materials very differently. No significant sign of deterioration was observed in fly ash-based geopolymer, although MgSO4 changed the chemical compositions by increasing Mg content and decreasing Na in the original N-A-S-H gel. On the contrary, Type V portland cement presented the degradation of the main hydration product due to the decalcification process with increasing MgSO4 exposure. This resulted in a significant drop of Ca/Si ratio and compressive strength after 6 months of MgSO4 immersion. Test-analysis results in different length scales in this study imply that fly ash-based geopolymer can be a durable material under MgSO4 environments.
... The effect of sealers on reducing or limiting chloride ions ingress into concrete is, however, inconsistent. 28,29 Ibrahim et al. 30 reported that the sealers' effect on the reduction of chloride diffusion and carbonation is minimal, whereas Jones et al. 31 and Golias 26 showed that silane was effective in reducing chloride ingress. ...
Penetration sealers are an economically viable technique to reduce water and aggressive substance ingress into concrete, and ultimately extend service life under harsh conditions. This paper discusses a laboratory investigation to assess effect of rate and application timing of a variety of penetrating sealers on saw cut concrete. Sealer types included pore lining, pore blocking, and pore refining in addition to surface coating. Testing included absorption, contact angle, and chloride ion penetration performed on mortar and concrete specimens. Results show sealers significantly reduced water penetration, as expected, with higher rates of application generally resulting in less absorption. Two applications of sealer applied at half the recommended dosage rate produced better performance than a single application at the full dosage rate, even for hydrophobic sealers such as silane. Of the sealers tested, solvent based and water based produced the greatest reduction in absorption and chloride penetration. The results show that sealers applied in the appropriate condition and concentration can greatly extend time to critical saturation by reducing absorption rate, significantly reduce chloride ingress and potentially increase service life of concrete or provide extra protection.
... Impregnating coatings (i.e., pore-blocking treatments) are able to block the capillary pores of the concrete and consequently improve the impermeability of buildings [28,29]. Generally, the treatments available on the market are based on silicates (such as lithium silicate, sodium silicate and calcium silicate) that, in contact with the chemical constituents of concrete, form a colloidal gel capable of blocking the pores and avoiding the penetration of potentially harmful external agents. ...
The increasing demand for reconstructions of concrete structures and the wide availability on the market of surface protective products and systems could lead to misunderstandings in the decision of the most effective solution. Surface protectors have become increasingly widespread in recent years in concrete restoration interventions thanks to their properties: they are able to protect the substrate from aggressive agents and consequently extend the useful life of the structures. The aim of this article is first of all to present the surface protective treatments available on the market, outlining their strengths and weaknesses. Subsequently, a characterization of seven different commercial coatings for reinforced-concrete structures is provided, taking into account chemical nature, fields of use and effectiveness, both in terms of physic and elastic performance and resistance to aggressive agents that undermine the durability of the treated concrete elements.
... The protection methods that are commonly used include: (i) the use of protective coatings on cement-based surface protective coating, (ii) rebars coating and (iii) corrosion inhibitors [3][4][5][6][7][8][9]. Some of these methods are suitable for new concrete structures, whereas others may also be adopted for existing structures (e.g., in repairs [10][11][12][13][14][15]). ...
The current paper aims to propose a novel epoxy resin bonding agent for improving the bonding strength of epoxy resin coating systems. These kinds of systems are mainly employed during the repair and maintenance of existing cement-based structures, especially concrete floors. The paper presents the results of a series of tests of epoxy resin coatings, in which the matrix of the bonding agent made of epoxy resin is modified with the addition of coconut fibers. Pull-off strength tests were performed on the cement paste and cement mortar substrates. The results presented that the addition of 0.5%-1.0% of coconut fibers to the bonding agent matrix resulted in increased pull-off strength of the coating. In turn, it was observed that in the case of using a higher volume fraction of fibers the occurrence for the delamination failure between the epoxy resin and substrate was more pronounced. This is manifested by the reduction of the pull-off strength of the epoxy resin coating and is probably caused by the increased presence of fiber clusters in the epoxy resin matrix. Finally, to confirm the obtained macroscopic results, the specimens were analyzed using the scanning electron microscopy method by examining the interface between the coating and substrate. Numerical simulations were successfully predicting the behavior of pull-off strength using simplified concrete damage plasticity. The linear behavior was defined for presenting the softening behavior of the substrate during loading.
... With a thickness of only 0.1-1.0 mm, organic coatings can effectively protect the substrate concrete from attack of water, water vapor, carbon dioxide, chloride ions, sulfate ions and other corrosive media; therefore, they have been widely used [3][4][5][7][8][9][10]. However, the volatile solvent in many organic polymer coatings often releases toxic gases during their application, causing air pollution and health issues. ...
To improve the chloride resistance of traditional polymer-modified cementitious (PMC) coating, a novel nano-PMC coating was synthesized through incorporation of nano-SiO2 or nano-TiO2 suspensions into acrylic emulsion. Water absorption ratios, Coulomb electric fluxes, and chloride diffusion coefficients of coated concrete at different ages were tested. In addition, the micromorphology and pore structures of the nano-PMC coatings were investigated through scanning electronic microscopy and mercury intrusion porosimetry. Results indicate that the application of nano-SiO2 or nano-TiO2 particles in PMC coating can fully play the filling effects, refine the large micropores in coating and reduce its porosity. Thus, the waterproofing and chloride resistance of coated concrete are substantially enhanced. As a result, the service lives of concrete with nano-PMC coatings can be remarkably prolonged. The service lives of coated concrete against chloride attack can be lengthened by 7.1 times or 2.8 times 0.5% nano-SiO2 or nano-TiO2 are added into the PMC coating, respectively.
... General classification of coating materials used in different industries[24][25][26][27][28][29][30][31][32][33]. ...
Coating materials are considered one of the most antique materials of human civilization; they have been used for decoration and the protection of surfaces for millennia. Concrete structures—due to their permanent exposure to different types of environments and contaminants—require the use of coatings that contribute to its preservation by reducing the corrosion of its components (steel and aggregates). This article intends to introduce the principal causes of concrete deterioration and the coating materials used to protect concrete structures, including a summary of the coating types, their advantages and disadvantages, and the latest developments and applications. Furthermore, this paper also assesses brief information about the potential challenges in the production of eco-friendly coating materials.
... Much research has been done on improving the permeability of concrete. At present, most of the investigations have focused on two areas: (1) The method of surface treatment on cementitious composites to improve impermeability, in which organic or inorganic permeable protective materials are widely used (Pan et al. 2016;McCarter 1998;Ibrahim et al. 1999;Leung et al. 2008;Zhang et al. 2018;Rodrigues et al. 2000); and (2) improving the microstructure and density of cementitious composites to improve their impermeability-for example, mixing nanoreactive powder to reduce the number of internal pores in concrete (Roux et al. 1996;Mahmoud and Bassuoni 2019;Sohail et al. 2018) or improving the antiseepage performance of concrete by optimizing the concrete manufacturing process (gradation, water-to-binder ratio, admixture, mixing process, curing method, and so on) (Bentur and Goldman 1989;Samouh et al. 2017). In recent years, improving the microstructure of cement-based materials by using the metabolites of alkali-resistant microorganisms to improve the impermeability of cementitious composites has become a hot topic (Xu et al. 2014;Menon et al. 2019;Zhang et al. 2017;Basha et al. 2018;Ramachandran et al. 2001;Kim et al. 2011). ...
... It is generally considered that hydrophobic impregnation method can provide an effective protection layer for concrete, which improve the impermeability of concrete and further protect the internal steel structure from water-dissolved salts [14,15]. Silane and siloxane materials are the primary choice for protecting concrete, and most research has focused on testing these materials and improving their performance [16][17][18][19]. Moreover, once the waterproof coating is damaged, water will still invade the concrete. ...
In high humidity areas, it is necessary to improve the impermeability of concrete to water and other erosion solutions. The internal defect and pore channel of concrete are the main factors affecting the impermeability and durability. In this paper, a novel hydrophobic agent named Yellow River Engineering Consulting (YREC) was prepared. The relative internal defect degree of concrete with different curing ages and YREC contents was evaluated by ultrasonic non-destructive testing as qualitative characterization method, and the effect of YREC on hydration reaction was investigates using X-ray powder diffraction (XRD). Water permeability and contact angle tests were used to analyze the internal and external hydrophobicity induced by YREC addition, respectively. The pore structure changes of concrete mortar matrix induced by YREC were further discussed applying low-temperature liquid nitrogen adsorption (LT-NA) and mercury intrusion/extrusion porosimetry (MIP). The results indicated that YREC not only improves the impermeability of water, but also greatly enhances the mechanical strength. In the case of mixing YREC, the porosity of concrete mortar matrix decreases accompanied with the more advantage pores (micropores and transition pores) developed. Based on the relative internal defect degree and the changes of multi-scale pore structure, the functionality and durability of concrete with 4% YREC addition are the most desirable.
... As the samples have more impermeable and more high strength, they became more resistant to carbonation. The polymer coatings are effective a protection method for the carbonation resistance of the concrete, when compared to cementitious or hydrophobic coatings [38]. Table 6 The splitting tensile strength results of specimens exposed to carbonation. ...
In this study, the effects of the curing time, the carbonation time, the phosphazene percentage used in the polymer and the cement content on the carbonation resistance of polymer-phosphazene concrete were experimentally and statistically investigated by Taguchi method. The Taguchi L25 (5⁶) orthogonal table was selected for this study. 100 × 100 × 100 mm specimens were prepared. The specimens were cured in water at 20 ± 2 °C for 28, 60, 90, 180 and 365 days. The polymer containing phosphazene was impregnated to the specimens and conducted polymerization by heating. Then, these samples were exposed to carbonation for 3, 7, 14, 28 and 56 days. The microstructure, the carbonation depth, ultrasonic pulse velocity, splitting tensile strength and changes in weight of the samples were determined. The Anova results found that cement content was found to be the experimental variable that most affected the results of the experiment. The percentage of this effect was found between 34.43% and 72.94% in Anova analysis. According to Taguchi results, the optimum experimental variables for the maximum splitting tensile strength, the maximum UPV, the minimum weight change and the minimum carbonation depth were found as 14 days for the carbonation time, 3% for the phosphazene percentage, 365 days for the curing time and 450 kg/m³ for the cement content.
... In view of that, protective materials are used on concrete surfaces to inhibit the solution erosion and reduce the water quantity absorbed by pore network [9]. Silane and siloxane materials are popular admixture in hydrophobic area of concrete, and lots of researches focused on enhancing the hydrophobicity by modify these materials [10][11][12][13]. The addition of unmodified silica microparticles has proved to be an effective method of water resistance by forming a barrier at the water-solid interface to prevent the diffusion of ions and water [14][15]. ...
An innovative hydrophobic agent named YREC (Yellow River Engineering Consulting) was adopted in this study. The substrate is mica powder, which is treated with silane coupling agent and polydimethylsiloxane. By comparing hydrophobicity of the hydrophobic agent with different dosages of polydimethylsiloxane and temperatures, the optimum processing scheme of hydrophobic agent was provided. A series of hydrophobic concrete with different water to cement ratios and YREC contents were prepared. Freeze-thaw (F-T) resistance and mechanical properties of concrete were investigated. Meanwhile, microstructure was determined by means of water adsorption test and mercury intrusion porosimetry. The results show that the YREC provides hydrophobic functional group and improves pore network to inhibit the invasion of water, which further enhances the F-T resistance and mechanical properties of concrete significantly. The pore size characterizations indicate that the addition of YREC increases the quantity of transition pores while decreases that of macro-pores, and the mechanical properties of concrete are reduced obviously due to the decrease of macro-pores. Compared with adjusting water to cement ratio, YREC is more conducive to refine pore structure of concrete.
... For example, Franzoni (Franzoni, Pigino and Pistolesi, 2013) found that the use of nano silica has a carbonation penetration reduction effect of around 14-47%. For his part, Ibrahim (Ibrahim et al., 1999) found that surface treatments based on silanes/siloxanes showed a reduction of around 20% in carbonation penetration. ...
This study aims to evaluate the use of silicon base (NS) and functionalized (NF) nanoparticles as emerging preventive surface treatment (ST) in reinforced concrete specimens. The specimens were fabricated with a water/cement (w/c) of 0.65 and subjected to a previous aging period through exposure to CO2. Subsequently, two different variants of the treatment were applied by spraying (using a 0.1% dispersion of nanoparticles in water) and then re-applied to carbonation. The carbonation depth and contact angle results indicate that there is an influence between the degree of aging and the efficiency of each treatment.
... However, CSA cement-based concrete sewage pipes and hazardous waste sealers are prone to severe aggressive environment, and chloride ions, sulfate ions, inorganic and organic acid ions would erode the materials severely. Therefore, improvement of impermeability of the materials is a critical method to improve their durability [2,3]. ...
In this study, the efficiency of surface treatment in the calcium sulfoaluminate (CSA) cement-based materials were explored. Several frequently used surface treatment agents (sodium silicate (NS), and magnesium fluorosilicate (MFS), tetraethyl orthosilicate (TEOS), poly-methyltriethoxysilane (PMTS)) were applied on hardened CSA mortar and concrete. The penetration depth of these agents and their influence of the treatment on the properties of water sorptivity, carbonation resistivity, mechanical property, and pore structure was investigated. Results showed that the penetration depth of NS and MFS was around 60-85um, and that PMTS, MFS, TEOS, and NS could reduce the water sorptivity by 94.0%, 17.0%, 11.0% and 7.8%, respectively. PMTS and TEOS could reduce the carbonation rate by 38.7% and 14.3%, respectively, but NS and MFS could not reduce it. In addition, PMTS can reduce the pores less than 50 nm (S pores) significantly, whereas has little influence on pores between 50 nm and 1 μm (M pores). NS, MFS and TEOS would reduce M pores, but increase S pores. By the combination of permeability and pore structure test, it was found that volume of S pores was positively correlated to the carbonation rate and the volume of M pores was positively correlated to the water sorptivity. Furthermore, it was found that surface treatment had little influence on the compressive strength, but it could increase flexural strength slightly. This work evidenced the effectiveness of surface treatment on CSA cement-based materials and highlighted the critical role of fine pores (less than 50 nm) in their transport properties.
... Due to restricted access of water and oxygen into the concrete body, the surface treatment could enhance the resistance to concrete deterioration in terms of chemical degradation such as sulfate attack and carbonation [40]. However, a lower bond between concrete body and surface treatment may potentially induce lower frost damage and abrasion resistance [41]. ...
The present study concerns hydrophobic surface treatments with silane-based liquid and crème on the concrete surface against external ionic transport for the application to concrete pavement coating. To quantify their effectiveness in mitigating the ionic penetration, water absorption and chloride transport were measured. Especially, back-scattered image analysis and the electrochemical impedance spectroscopy were used to identify the effect of pore-blocking at the interface of coating agents and the concrete. As a result, the surface treatment with both liquid and crème could significantly reduce the water absorption and chloride ingresses at all depths of measured concrete, due to a modification of the porosity. Moreover, the surface treatment on concrete substrate increased the polarization resistance, thereby enhancing the resistance to ionic transport into the concrete, and the crème type was slightly more effective at the same dosage of treatment.
... Organic paints, such as epoxy and silicone resins, 13,14 acrylic, 15,16 chlorinated rubber, 14 coal tar, 17 polyurethane, 18 and polymer modified cementitious coatings 19 are commonly used to form a continuous surface coating; (b) surface hydrophobic method: silane and siloxane are generally used to form a water-repellent surface 20,21 ; (c) pore-blocking treatment: sodium silicate/potassium silicate and fluorine sodium silicate/fluorosilicate are widely used as permeable crystallization materials 22,23 ; (d) biological method: calcium carbonate deposition is carried out by inducing microorganisms in cementbased materials, and consequently, pores and microcracks in concrete gradually become filled. [24][25][26][27] However, organic materials have poor durability and fireresisting ability, 28 and the surface protection properties of inorganic materials have yet to be revealed. ...
The performance of the conventional concrete skin was promoted by ultrasonic surface treatment (UST) in this study, and the newly formed dense and hard concrete skin was termed as ultrasonic hardening layer (UHL). The microstructure of UHL was scanned and analyzed, several durability‐related indicators, such as water vapor penetration rate, surface, and interface hardness, were measured, and it was found that UHL could effectively improve the durability of concretes. The light reflectance of the UHL concrete surface was measured in the spectrum range of UV (200 nm) to NIR (2,500 nm), and it manifested 24.17% less mean reflectance than the conventional concrete skin. Therefore, UHL could serve as a promising road material due to its better melting capacity in cold‐temperate zones.
Oxygen plays a key role in the oxidation of sulphide minerals in concrete aggregates. This study developed an accelerated test using high oxygen concentrations to evaluate the potential for sulphide oxidation and internal sulphate attack in concrete. Two methods were used: drying of water-saturated samples in an oxygen-filled environment, referred to as oxygen-drying, and wetting of semi-dried samples in oxygen chambers at 100 % relative humidity, referred to as oxygen-wetting. The idea beyond the two methods was to maintain the samples at levels of saturation and access to oxygen that accelerates oxidation. The oxygen-wetting method produced higher expansion. In this method, different approaches of pre-drying the samples before exposure to oxygen and 100 % RH were attempted, and the optimized approach – drying the samples at 40 ◦ C for 24 hours – was selected. The method was used to evaluate the efficacy of possible mitigation methods. The acceleration of the proposed method was validated by comparing its expansion to that of outdoor samples, revealing that the lab samples exhibited 7–10 times greater expansion Using metakaolin and slag increases the expansion, likely due to the higher reactive alumina content in the mixture. Type-F fly ash reduces the expansion since the alumina in fly ash is less reactive. High silica fume cement combined with slag reduces the deterioration, partly because it decreases permeability. Crystalline coatings applied after cracking reduced the ongoing expansion; however, the reduction was not significant. The sodium silicate-based coating was more effective when applied before cracking than when applied after cracking.
Cementitious construction materials like concrete stand as pivotal constituents in the respective industry owing to their wide-ranging benefits in terms of abundant raw material sources, ease of processing, versatile usability, exceptional material properties, durability, and cost-effectiveness. Nonetheless, the production of cement is associated with substantial carbon dioxide (CO2) emissions, thereby contributing significantly to global greenhouse gas levels. This conundrum underscores the pressing need for innovative solutions that can mitigate the environmental impact while preserving the indispensable attributes of cementitious construction materials. This review article delves into the realm of surface treatments as a promising avenue to augment the service life and sustainability of concrete structures. The primary objective of using coating technologies is to curtail the overconsumption of cement and natural resources – such as water, sand, and gravel – by extending the longevity of cementitious construction materials, which contributes to an alleviation in the environmental footprint of cement production and, subsequently, to a reduction in global anthropogenic CO2 emissions. In this comprehensive study, we discuss three distinct types of established surface coating: (1) organic coatings, (2) coatings based on nanomaterials like graphene, and (3) inorganic coatings. Through a systematic examination of these approaches, we elucidate their mechanisms of protection, highlighting their potential to enhance the durability, resistance to environmental stressors, and overall performance of cementitious construction materials. Based on a comprehensive literature review, we compare the performance of these surface treatments in terms of protecting different cementitious surfaces against different degradation scenarios. Finally, we give an outlook on new innovative approaches for the protection of cementitious surfaces, including the presentation of the concept of incorporating rare earth metal ions into the surface of cementitious construction materials. This could potentially combine the advantages of organic and inorganic surface treatments as well as integral waterproofing.
Description
This unique, new ASTM publication details the latest worldwide research on atmospheric corrosion, seawater corrosion, deterioration of concrete, and underground corrosion issues pertaining to tropical environments.
21 peer-reviewed papers cover:
• Mechanisms of corrosion processes.
• Performance of various remedial measures to prevent corrosion damage to steel in concrete.
• Proposal for revision of the ISO atmospheric corrosivity classification.
• New approach to cathodic protection of rebar and concrete.
• Evaluation of stainless steel for rebar in concrete as a long-term solution.
• Protection of underground structures in tropical marine environments.
• Difficulties of coating stainless steels for use in seawater.
Freeze–thaw cycles, application of deicing salts, and rebar corrosion are becoming main sources of concrete deterioration in bridge decks and pavements. During the past few decades, concrete surface treatments have begun to receive wide acceptance because of their effectiveness in sealing the concrete. Surface treatments achieve this by limiting fluid ingress, thereby reducing damage associated with freeze–thaw cycles, deicing salt application, and rebar corrosion. Soy methyl ester-polystyrene blends (SME-PS) have been shown to be an innovative, promising method of topical sealing. SME-PS, which is a derivative of soybean oil and expanded polystyrene, has been continuously studied since 2008. In this context, a comprehensive literature review compared the performance of SME-PS with that of traditional concrete sealers, including organic, inorganic, hybrid, and biotic sealers. These sealers were reviewed for performance in reducing water absorption and chloride penetration and improving freeze–thaw durability of concrete. The reviewed papers indicate that SME-PS possesses superior performance as a concrete protectant for reducing water absorption, chloride penetration, and freeze–thaw damage. To further enhance the feasibility of SME-PS, future studies may include investigating the physical and chemical protecting mechanisms of SME-PS, understanding the factors that affect the penetration behavior of SME-PS in concrete, and evaluating the short and long-term effectiveness of SME-PS in concrete.
Concrete filled steel tube (CFST) is an effective method to alleviate sulfate attack in saline soil environments. In this study, the effect of hoop restraint on the degradation behavior due to sulfate attack in ordinary Portland cement (OPC) paste and sulfate-resistance Portland cement (SRPC) pastes is studied. The cracking behavior and mass variation are determined to investigate deterioration process of the pastes. EPMA-WDS, nanoindentation and SEM-EDS are performed to analyse the deterioration mechanism of the cement paste under hoop restraint condition. As the results shown: The deterioration behaviors of cement pastes is strongly affected by hoop restraint. Specifically, the hoop restraint inhibited crack formation of the specimens and formation of sulfate products. The average effective sulfate diffusion coefficient is reduced by 30.26% and 5.81% for OPC and SRPC paste during 365 days of exposure, respectively, compared with the reference group. Moreover, the mechanism of deterioration of cement paste under hoop restraint condition is proposed based on change in chemical component of C–S–H phase. The hoop restraint from steel tube can effectively inhibit the sulfate attack on cement composite with important engineering significance.
The paper discusses innovative approaches and targeted structural treatments of works on paper and paintings made possible by temperature management technologies based on low-energy flexible mats for precision heat transfer. Flexible silicone MAT (Multipurpose Accurate Thermal Management, developed by the Precision Mat, LLC) laminates, and transparent carbon nanotube-based IMAT (Intelligent Mobile Multipurpose Accurate Thermoelectrical Device for Art Conservation, developed by IMAT project, Horizon Europe) prototypes with the associated mobile MAT and IMAT thermal management consoles were ideated and designed specifically for the field to offer accuracy, mobility and smart nano-tech for new CH remediation approaches over the unreliable traditional tools of the past, such as hand irons and heating tables, with the benefit of precision, steadiness, uniformity, and control in heat transfer from ambient to the customary temperatures used in heat activation (25 °C−65 °C). The varied MAT and IMAT mat dimensions, their flexible and thin profile combined with accuracy in the low temperature range allow conservators in diverse fields to formulate novel targeted treatments that exploit the effects of sustained precision mild heat transfer over time without the risks and unnecessary stress related to uncontrolled heat-transfer of the past. Case studies examine the application of flexible warming mats in diverse treatments of works on paper, and photographs conducted by the authors. The operational parameters and practical advantages offered by the low-energy heat transfer nanotechnology and targeted approaches taken in each particular treatment show the broad versatility of the new heat transfer method and how easily it could be tailored for the specific needs of each particular case, opening new opportunities for art conservators to refine their treatments within the margins of minimal intervention and risk.
The chosen object from the National Museum in Kraków collection (the Amber Altar of the Lord’s Passion) was examined by Raman spectroscopy (RS) and reflectance imaging spectroscopy (RIS) in short wavelength infrared (SWIR) spectral range. These studies allowed to identify the type of amber used and to assess the existence of a degraded layer. Based on the analysis of the reflection spectra and using the NMF (Nonnegative Matrix Factorization) algorithm, the amber of the Altar were assigned to two different classes. It may be associated with the use of different technologies for the preparation of amber plates. Moreover, as a result of the PCA (Principal Component Analysis) dimension reduction algorithm, an initial classification of the object’s amber into succinite (both native and German) and/or gedan-succinite and/or glessite was performed. Analysis of Raman spectra obtained by deep profiling method allowed to state the existence of a degraded layer on the surface of the amber figures of Saints Peter and Paul. The change in the spectrum profile depending on the depth of the signal collection indicates, among others, changes in the structure related to the exomethylene group and changes in the CH and CH groups. Thanks to the analysis of reflectance imaging spectroscopy and Raman spectroscopy, it was possible to identify the places of occurrence of amber imitations. The bands distinguished in the Raman spectra indicate the use of an epoxy resin.KeywordsAmberHeritage objectsReflectance imaging spectroscopySWIRRaman spectroscopyDegradationAmber imitation
Penetrating sealers are one means to reduce moisture and chemical transport into concrete. However, a large variety of products are available possessing different functional modes of action. This study investigated representative families of penetrating sealers applied to vertical, sawn faces of properly air-entrained concrete (~6%) to represent field application of sealers to concrete joints. Concrete was characterized for water transport, chloride diffusion, gas permeability, frost resistance in the presence of deicing salts, and potential for oxychloride formation. The results showed some sealers effectively reduced water absorption, prolonged time to saturation, and reduced chloride penetration. However, delayed time to critical saturation did not always result in improved frost resistance. All sealers significantly reduced the potential of oxychloride formation. The tests used for this study are broadly applicable and provide enhanced characterization for selection and application of new types of sealers and modes of action.
This study experimentally investigates the effects of strontium nitrate (Sr(NO3)2) aqueous solution on hardened concrete composite as a surface hardening method. Density, void content, water sorptivity, and surface abrasion resistance of the concrete mixture treated by Sr(NO3)2 solution were measured under diverse curing and treatment scenarios. The results showed that 30% Sr(NO3)2 aqueous solution increases the density by 1.0% and 2.2% and also decreases the void content by 7.4% and 14.4% with the water-cement ratio (w/c) of 0.5 and 0.4, respectively. Water sorptivity of the treated hardened concrete was decreased by 26.4% and 34.0% from the lithium silicate and sodium silicate treatments, respectively. In addition, the Sr(NO3)2 treatment increases the surface abrasion by 45% from the control specimen and about 25-30% from the two silicate-based treatments. X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive spectrometer (EDS), and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) were conducted to investigate the micro-morphologies, microstructure, and elemental characteristics. The results illustrate that (1) microstructures of hydrated cement matrix are densified, (2) portlandite (CH) in the matrix decreases as time elapses, (3) multiple types of hydrated aluminosilicate minerals (i.e. zeolites) are formulated, and (4) more subsequent polymerization related to C-S-H/C-A-S-H occurs. Lastly, the densifying and strengthening mechanisms of the hydrated cement by the Sr(NO3)2 treatment process are presented and discussed.
In this study, three types of concrete surface penetrant materials were studied in the laboratory environment, including two kinds of silicate solutions (modifying and reaction type), and another hydrophobic impregnating material silane. They were painted on two different cement-based (Normal Portland cement and Blast furnace slag) concrete. During the experiment, there were three sorts of painting schemes, consist of two kinds of silicate applied separately and a compound application of silicate reaction type and silane type. Five kinds of painting dosage were designed, which were the recommended dosage, and 0.25, 0.5, 1.0 and 2.0 times of the recommended dosage. The surface air permeability and water absorption rate of the concrete before and after painting penetrants were tested and compared. It found that all of them have little effect on air permeability, however, the air permeability of the concrete surface decreased with the increase of the surface water content. But the water absorption rate was not affected by surface water content obviously when it was 4-5%. The composite coating method could significantly reduce the surface water absorption rate of concrete, and the dosage was also much more economical.
Silicate-based surface impregnation is used to improve the surface durability of concrete structures. This study employs various analysis tools to understand the relationship between cement-hydrate formation behavior and durability development upon the application of a silicate-based surface impregnant. Through simple surface immersion experiments, we evaluate the chemical properties and mass transfer resistance of modified surfaces and observe changes in carbonation related to these properties. We found that calcium silicate hydrate at the surface is produced due to the application of the silicate-based surface impregnant. However, we confirm that the penetration of carbon and carbonation of the surface layer are promoted due to changes in both the hydrate and physical properties of the modified surface. In addition, the chemical and physical changes in the surface layer due to the modification reduce the elastic modulus of the surface layer and have no effect on improving mass transfer resistance. These results could present a significant contribution to developments in concrete applications and allied fields.
In order to improve the durability of concrete structures, silicate-based impregnant have been used, but the chemical interaction mechanism is not clear. Silicate-based impregnant react with calcium hydroxide, which is formed during the process of cement hydration, and form compounds similar to a calcium silicate hydrate (C–S–H). This paper performs reaction experiments by Ca/Si ratio, and solid state nuclear magnetic resonance (NMR) and X-ray powder diffraction (XRD), fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy are conducted for observing chemical changes of cement paste with silicate-based impregnants. Based on the results of XRD, reduction of monosulfate phase was observed as well as the formation of C–S–H (tobermorite-like phase). ²⁹Si and ²⁷Al NMR spectra also correspond with the XRD results. Further, possibility of both Al/Si substitution and formation of a structure close to C-(A)-S-H (C–S–H containing Al) were observed. Therefore, silicate-based impregnant formed not only new C–S–H reacting with calcium hydroxide, but also influenced other hydrates.
Porosity evolution caused by electrochemical chloride removal (ECR) process can affect the transport behaviour of concrete and vice versa. The main task in this investigation is to quantitatively understand the porosity evolution effect on ECR process, and find a more accurate model that gives good correlation with the experimental results concerning the ionic transport in concrete during the ECR. The porosity of the concrete near the cathode and anode were measured, before and after ECR treatment (mainly 7 days, 15 days and 30 days). A method to analyse and calculate the porosity profiles was proposed according to the ECR experimental data. The penetration and leaching of ionic species in concrete are studied by using a finite element procedure based on the Nernst–Planck equations. The proposed method is capable of reducing the numerical modelling error of the chloride profile in concrete during the ECR.
Epoxy-coated reinforcing bars are widely used in bridge decks to mitigate the corrosion of reinforcing steel. Research and practical experience both showed that the smooth epoxy coating significantly reduces the bond between concrete and reinforcing steel, which often results in the early development of transverse cracks in bridge decks. To solve this problem, the Illinois Department of Transportation (IDOT) proposed a new type of textured epoxy-coated (TEC) reinforcing bars with applied roughness to improve the bond between concrete and steel while providing corrosion protection. This study investigates the surface roughness of six different types of TEC bars and how it impacts the bar’s bond-slip behavior with concrete. First, the surface roughness of the TEC bars is compared with that of uncoated black bars (BLK) using 2-D parameters Ra, Rz, and 3-D parameters Sa and Sz. Second, direct pull-out tests are conducted on concrete specimens with embedded 1) BLK, 2) smooth epoxy-coated (SEC), and 3) all six TEC bars to compare their bond characteristics. Finally, a 3-D finite element model is developed and calibrated to simulate the bond-slip behavior of TEC bars embedded in concrete. The results show that the average surface roughness of TEC bars is 3–4 times that of the uncoated bars. Further, TEC bars generally exhibit higher slip resistance than the uncoated and smooth epoxy-coated bars.
This investigation evaluates the chloride diffusion coefficient for concrete made with marginal limestone aggregates and Type V Portland cement commonly used in the Arabian Gulf. Parameters investigated are (1) water-cement ratio, (2) cement content, (3) surface chloride concentration, and (4) exposure condition. An attempt is made to arrive at a model for predicting the onset of corrosion using the limited test data. The experimental results revealed that the chloride diffusion coefficient is strongly influenced by water-cement ratio and exposure conditions and marginally by cement content but unaffected by the surface chloride concentration. The chloride diffusion coefficient values ranged from (8 to 170) x 10-8 cm2/sec for different concrete mixes and exposure conditions. The high value of the chloride diffusion coefficient is mainly attributed to the low concrete quality and the local aggressive environmental conditions. The basis of the prediction model to corrosion initiation has been set and reasonable results are produced based on the limited experimental data.
Adverse geomorphic and climatic conditions as well as defective construction practices control concrete performance in the Arabian Gulf area. Condition surveys on structures located in Eastern Saudi Arabia show an alarming degree of deterioration within the short span of 10 to 15 years. Data show that this deterioration is attributable in decreasing order of importance to corrosion of reinforcement, sulfate attack, and environmental cracking. The mechanisms of these causal factors are discussed with respect to the environmental conditions of the Gulf coast.
After only 10 to 15 years of service, many reinforced concrete structures in the aggressive environment of the areas surrounding the Arabian Gulf are showing an alarming degree of deterioration. Condition surveys indicate that corrosion of the reinforcement is the most prevalent form of this deterioration. This article presents a study based on data collected from 20 reinforced concrete structures, all from 22 to 27 years in service, all located in Eastern Saudi Arabia. The study included an analysis of 108 cores to determine the influence of chloride content, cover of the reinforcement, and other factors that could lead to corrosion.
This investigation was carried out to elucidate the role of chloride ions in sulphate attack in plain and blended cements. Paste and mortar specimens made with Type I and Type V cements as well as with Type I cement blended with fly ash, silica fume and blastfurnace slag (BFS) were exposed to four sulphate and/or chloride environments for a period of two years. The performance of these cements was evaluated through visual inspection and measurement of reduction in compressive strength. X-ray diffraction and scanning electron microscopic techniques were used to study the sulphate attack mechanisms in plain and blended cements in both the presence and the absence of chloride ions. Results indicate that sulphate deterioration in plain cements was mitigated by the presence of chloride ions, whereas in blended cements, particularly those made with silica fume and BFS, the beneficial effect of chloride was only marginal. This is attributed to the Mg-oriented sulphate attack which was more operative in blended cements. In contrast to the gypsum and ettringite-oriented sulphate attacks, this type of attack was not inhibited in the presence of chloride ions.
“Surface coatings for improving performance of concrete under marine environments
- T Fukute
- H Hamada
“Recent developments of protection techniques for concrete structures in Japan
- K Katawaki
The effect of polymeric surface treatment compounds on the water absorption and chloride diffusion of concrete exposed to hot dry environments
- J G Carbrera
- K G Hassan
Kansas study questions silane sealer effectiveness.” Concrete Constr
- C F Crumpton
Protection of reinforced concrete elements against corrosion by polymer coating
- M M Kamal
- A E Salama
“Surface treatments for the protection of concrete
- M Leeming