Concrete Surface Coatings Research Articles

Service Life Prediction of Inhibitors and Concrete Surface Coatings in Concrete-Embedded Reinforcing Steel Corrosion Caused by Chloride

Service Life Prediction of Inhibitors and Concrete Surface Coatings in Concrete-Embedded Reinforcing Steel Corrosion Caused by Chloride

Cementitious Coatings for Concrete Surfaces: Effects of Curing Conditions on Performance Measure

To increase cohesiveness, toughness, impermeability, and adhesion strength in cementitious materials like mortars and concrete, vinyl acetate ethylene (VAE) copolymer redispersible powder (RDP) is used. However, due to numerous variety of material, choosing an original performing RDP is challenging. The goal of this study is to assess the bond strength to concrete surfaces of various redispersible polymer-modified cementitious coatings under various accelerated settings. The outcomes showed that the RDP backbone composition has a significant influence on the coatings' adhesion strength. Methyl methacrylate (MMA) and Vinyl chloride (VC) present as comonomers in RDP exhibit outstanding thermal stability and boost tensile adhesion strength by 41% and 21%, respectively, in comparison to other RDPs. According to SEM studies, the VC- RDP stimulates the formation of fibrous ettringite, producing a uniform and cohesive microstructure.

Fungal-induced CaCO3 and SrCO3 precipitation: a potential strategy for bioprotection of concrete

Biomineralization of CaCO3 by microorganisms is a well-documented process considered applicable to concrete self-healing and metal bioremediation. Urea hydrolysis is the most widely explored and efficient pathway regarding concrete bioprotection. However, the potential of fungi has received relatively little attention compared to bacteria. In this work, we show that Fusarium cerealis, Phoma herbarum and Mucor hiemalis, isolated from concrete, could produce 828.6–941.3 mg L−1 ammonium‑nitrogen in liquid media through urea hydrolysis indicating significant urease activity, and could grow in moderate (pH 8.3) or even extremely alkaline (pH 10.6) conditions. After culture in media containing 50 mM CaCl2, at least 48.8% Ca2+ was removed from solution by the selected fungi as calcite. The accumulation of Ca by the biomass was around 83.64–114.21 mg g−1. In addition, all fungi could mediate strontium carbonate formation with F. cerealis processing the highest ability for Sr removal, with ~61% added Sr being removed from solution. Scanning electron microscopy showed carbonate biominerals were encrusted on hyphae or aggregated in fungal pellets. When equivalent concentrations of Ca2+ and Sr2+ were supplemented to the media, CaCO3 with incorporated Sr formed with F. cerealis and M. hiemalis, and Sr(Sr, Ca)(CO3)2 with P. herbarum. Our results demonstrate the potential of fungi in providing carbonate coatings for concrete surfaces and simultaneous immobilization of Sr. We anticipate our work will promote further practical field research on porous cementitious materials protection by fungi and immobilization of potentially toxic metals from metal-laden ingredients, such as fly ash and granulated ground blast furnace slag.

Predicting Service Life of Concrete Structure Exposed to Sulfuric Acid Environment by Grey System Theory

This paper investigated the sulfuric acid resistance of concretes with fly ash (FA) replacement ratios of 0, 20, 30 and 40% and coated with two types of concrete surface coatings. As an index for degree of acid corrosion, the acidification depth with corrosion time was evaluated by an accelerated laboratory test. The test program involved continuous acid immersion of specimens and alternate wet–dry cycles of acid exposure of other specimens. The relations between the acidification rate coefficient, its FA replacement as well as the pH value of the acidic exposure solution was investigated while assuming Fick’s 1st law of diffusion. The grey model (GM) for concrete acidification prediction was established by adopting the grey system theory, which comprehensively considered the effects of the FA replacement and pH value of acid. The GM model was then applied to predict the impact of pH value, thickness of concrete cover and surface coatings on the service life of concrete structure in different sulfuric acid environments. It was found that the concrete deterioration due to alternate wet–dry cycles of exposure to acid is more severe than continuous acid immersion, and the water-based protective coatings for as-cast finish concrete (PCC) and the deep penetrating sealer (DPS) were highly effective in reducing the acid attack. Compared with the increase of the thickness of concrete cover, the application of the PCC and DPS coatings significantly extended the service life of concrete.

Long-term performance of concrete surface coatings in soil exposure of marine environments

The present research addresses the performance of coated concrete samples after 88months of natural exposure to coastal soil of the Persian Gulf. A concrete mixture proportioned with water-to-cement ratio of 0.5 was used for casting the reference and all coated specimens. Five types of surface coatings were investigated. Samples were extracted at different ages of 9, 36, and 88months to monitor carbonation depth and chloride ion penetration into concrete. Slight signs of carbonation are observed for the reference concrete and specimens coated with cementitious coatings. Chloride ion concentration profiles are analyzed during the exposure period. Chloride ion diffusivity is investigated for each sampling time. Surface chloride build-up is also monitored. Time to corrosion initiation is calculated and incorporated as a means of ranking coating efficiencies. Among all studied coatings, aliphatic acrylic and polyurethane are proved to reduce chloride ion concentration most effectively. This resulted in increasing the simulated time required for corrosion initiation in soil exposure at marine environments.

Penetrating waterproofing coatings based on slag -containing cements, modified by natural zeolites

The paper deals with obtaining penetrating waterproofing coatings for concrete surfaces based on the slag-cement systems, modified by natural zeolite additives. The composition was investigated and physico-mechanical properties of slag-containing cements with natural zeolite, which were subsequently modified by the salt-electrolyte complex to create penetrating coating, were optimized. Studying the properties of the developed coating has confirmed its competitiveness in the market of similar concrete waterproofing products and shown the property retention in time (after 1-2 years of operation). Hydration products of the developed material were investigated using physicochemical research methods. It was shown that the component structure of the cement matrix creates the conditions for the synthesis of new hydration formations of C-S-H type, capable of concrete pore space calmatation. It was revealed that introducing the modifying complex additive of salts-electrolytes provides a directed formation of crystal-hydrate phases, capable of binding free portlandite in the concrete structure and filling voids and pores of the concrete. Concurrent administration of the natural zeolite additive promotes binding of free alkali and ensures forming of a durable waterproofing coating, which does not lose its insulating properties over time. Developed coatings become part of the concrete structure, sealing its composition and creating new stable formations, coatings are not peeled off over time and do not loosen the existing concrete as it was observed in the compared analogues. Thus, the developed method for restoring massive concrete structures allows to avoid costly removal and new concreting.

Time-dependent performance of concrete surface coatings in tidal zone of marine environment

Corrosion induced by salinity of marine environment is a great threat for significant infrastructures which are placed in such areas. Concrete surface coating is one of the main materials which are used in new or repaired concrete structures which are located in corrosive environment. In this study six different concrete surface coatings are implemented on the surface of concrete and the performance of these coatings has been investigated during 5years of exposure in tidal zone of Persian Gulf region. According to obtained results, epoxy polyurethane and aliphatic acrylic are proven to be the most efficient coatings, which cause a reduction the chloride penetration and enhance the service life of concrete structures. However, performance of surface coatings is time-dependent and coated concretes must be recoated with distinct surface coating in proper time which means before coatings deterioration time. A new method for evaluating the performance of surface coating has also been proposed.

Effectiveness of surface coatings in improving concrete durability

This paper reports results of a study conducted to evaluate the durability of concrete coated with concrete surface coatings representing five generic types. The durability of the uncoated and coated concrete specimens was evaluated by assessing water absorption, chloride permeability and chloride diffusion. The chemical resistance was evaluated by immersing the uncoated and coated mortar specimens in 2.5% sulfuric acid. The results indicated that epoxy and polyurethane coatings performed better than acrylic, polymer and chlorinated rubber coatings. However, noticeable variation in the performance of the same generic type procured from different manufacturers was noted. Therefore, the selection of coatings should be done after conducting trial tests rather than basing it solely on the generic type.

Synergistic effect of corrosion inhibitor and inorganic coating on reinforcement corrosion

Concrete surface coatings, either organic or inorganic, have long been used for the protection of reinforced concrete. The aim of the present work was to compare, in the presence of chloride ions, the performance of an acrylic emulsion and an inorganic coating, when the latter is or is not combined with an inorganic corrosion inhibitor. The behaviour of the inorganic coating was examined, as its use is increasing due to environmental reasons and it can be applied on concrete surfaces for the rehabilitation of old structures. Strain gauge (SG) technique, half‐cell potential measurements, mass loss and carbonation depth measurements, as well as chloride diffusion rate, revealed that the acrylic emulsion provides better protection for reinforcing steel in concrete than the inorganic coating. However, the combination of the inorganic coating with the corrosion inhibitor provides a higher level of protection against steel bar corrosion.

Sinthetic resin coatings for concrete surfaces

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