Concrete Coatings Research Articles

Geopolymer synthesis by the alkali-activation of blastfurnace steel slag and its fire-resistance

Geopolymer has been synthesized by the activation of blastfurnace steel slag (GGBFS) using 6% (NaOH) or 3% NaOH+3% Na2SiO3. The geopolymer obtained in both cases exhibits an amorphous homogeneous and tightly-packed structure as well as a high compressive strength exceeding, that obtained by conventional mortar. In testing the response toward elevated temperatures it has been found that the geopolymer formed using 3% NH+% NS as activator reveals high stability and fire resistance where it retains high strength values even upon exposure to temperatures up to 500°C. The results clarify, also, that the geopolymer possesses stability and fire resistance higher than those exerted by normal concrete. The current study indicated the feasibility of the alkali – activated BFS geopolymer as a fire resistant coat substituting the reinforced concrete coat to lightweight polystyrene panels used for walls, roofs and partitions in construction work. Such introduced coat offers the following merits relative to the reinforced concrete coat: lower density, higher strength, higher fire-resistance, free of steel mesh reinforcement and reduced cost. The results of the present investigation clarify that geopolymerization could be considered as a viable technology for the conversion of industrial by-products having an aluminosilicate composition into attractive construction materials.

Long-term durability of onshore coated concrete —chloride ion and carbonation effects

Enhancing service life of reinforced concrete (RC) structures located in marine environments is an issue of great interest for design engineers. The present research addresses the effect of surface coatings on service life of onshore RC structures. Long-term performance of concrete samples up to 88 months of exposure at natural marine environment was investigated. Two onshore exposure conditions, including soil and atmosphere and different types of concrete coatings were studied. Carbonation rates of up to 0.5 and 1.5 mm/year were observed at the first 88 months of exposure for soil and atmospheric samples, respectively. Surface chloride ion build-up and variation in chloride ion diffusion were monitored with respect to time, and service life was estimated. Based on the obtained results it is proposed to use the aliphatic acrylic and polyurethane coatings for enhancing the service life of concrete structures in the investigated exposure conditions.

Life cycle analysis for concrete beams designed with cross‐sections of equal durability

AbstractDurability at the corners of the cross‐section is relatively weak in the concrete beams of bridges; the reinforcement at the corners therefore corrodes first. In order to delay durability failure at the corners, measures should be taken such as the application of corner concrete coatings or adjustments to the reinforcement at the corners. In this way, the durability resistance would be adjusted to be equal in the section, which is called the equal durability design method. In this paper, the life cycle analyses of a component designed with equal durability and one designed in the traditional way – both in a carbonation environment – are conducted and compared. A probabilistic model of service life is established based on empirical degradation models. Service life distribution is calculated with the Monte Carlo simulation method. Costs associated with durability failure are estimated based on the service life distribution. Related influencing factors are analysed as well. Finally, life cycle cost analyses of the component designed with equal durability and the one designed in the traditional way are conducted and compared. The results show that the component designed with equal durability is more economic over the life cycle if construction cost is kept within about 1.1 times that of the component designed traditionally.

PROCESSES PROCEEDING ON CONCRETE COATING SURFACES IN CASE OF THEIR CHEMICAL PROTECTION AGAINST WINTER SLIPPERINESS

Concrete coatings of road traffic highways along with operational loadings caused by flow of traffic are subjected to weather and climate impacts. These are the following impacts: changes in temperature and air humidity, solar radiation, surface wind speed which is participating in formation of active heat-and-mass transfer in a surface layer of the concrete coating. One of the most complicated and important periods in the road traffic highway operation is so called transitional nature period (from Summer to Autumn and from Winter to Spring). These periods are accompanied by intensive rain and snow fall and possible formation of ice loading on the surface of cement and concrete coatings. These impacts significantly deteriorate friction properties of road pavement (friction factor φ is decreased up to 0.4 and less) that can be a prerequisite to creation of various accident situations due to sharp increase in braking distance. For example, while having dry pavement the friction factor φ is equal to 0.80–0.85, and during icy condition of the road the factor φ constitutes 0.08–0.15 that consequently entails an increase in braking distance from 7.5 up to 20.0 m and more. It is quite possible that ice layer appears on the surface of concrete coatings when road traffic highways are used in winter season. Various methods are applicable to remove ice from the surface they can include also ice-melting chemicals and sodium chloride NaCl in particular. The chemical decreases freezing temperature of the formed brine and causes ice melting at negative temperature. Processes of NaCl dissolution and ice melting have an endothermic character, in other words these processes are accompanied by heat ingress and due to it temperature is sharply decreasing in the surface layer of the concrete coating which is under the melting ice and in this case phenomenon of thermal shock is observed.

Assessing the Extent of Biogenic Sulfide Corrosion in Concrete and Selecting Coatings to Prevent it: Inspection and Testing Principles

Assessing the Extent of Biogenic Sulfide Corrosion in Concrete and Selecting Coatings to Prevent it: Inspection and Testing Principles

Properties of sulfur-extended asphalt concrete

Currently, increased functional reliability of asphalt concrete coatings associated with various modifying additives that improve the durability of pavements. Promising builder is a technical sulfur. Asphalt concrete, made using a complex binder consisting of petroleum bitumen and technical sulfur, were calledsSulfur-Extended Asphalt Concrete. Such asphalt concrete, due to changes in the chemical composition of particulate and bitumen, changes the intensity of the interaction at the interface have increased rates of physical and mechanical properties. There was a lack of essential knowledge concerning mechanical properties of the sulfur-bituminous concrete with such an admixture; therefore, we had carried out the necessary examination. It is revealed that a new material satisfies local regulations in terms of compressive and tensile strength, shear resistance, and internal friction.

Photocatalytic hydrophobic concrete coatings to combat air pollution

Several low cost, user-friendly photocatalytic surface coatings were applied to cementitious surfaces and tested as a remediation technique for transportation NOx emissions and organic pollutants. All of the sols (aqueous suspensions of nanoparticles) coatings showed very high nitrogen oxide (NO) conversion (∼90%) and Methylene Blue dye bleaching when applied to concrete surfaces, even when the coatings were extremely thin or diluted, independently on the deposition method (spraying or dip coating). A novel hydrophobic coating based on photocatalyst nanoparticles suspended in a siloxane sealant showed similar conversion at low NO concentrations but required a greater loading of TiO2. At high NO concentrations the hydrophobic coating was less effective, even at greater TiO2 loadings, suggesting that the adsorption is the rate limiting step in this conversion process. A threshold of 1% TiO2 loading in hydrophilic coating and 5% in the case of hydrophobic was needed to obtain a quantitative NOx conversion. A home-made TiO2 sol showed lower NOx photodegradation but a more homogeneous and bonded layer.

Impact of aggressive exposure conditions on sustainable durability, strength development and chloride diffusivity of high performance concrete

The main objective of this study is to evaluate the long-term performance of various concrete composites in natural marine environment prevailing in the Gulf region. Durability assessment studies of such nature are usually carried out under aggressive environments that constitute seawater, chloride and sulfate laden soils and wind, and groundwater conditions. These studies are very vital for sustainable development of marine and off shore reinforced concrete structures of industrial design such as petroleum installations. First round of testing and evaluation, which is presented in this paper, were performed by standard tests under laboratory conditions. Laboratory results presented in this paper will be corroborated with test outcome of ongoing three years field exposure conditions. The field study will include different parameters of investigation for high performance concrete including corrosion inhibitors, type of reinforcement, natural and industrial pozzolanic additives, water to cement ratio, water type, cover thickness, curing conditions, and concrete coatings. Like the laboratory specimens, samples in the field will be monitored for corrosion induced deterioration signs and for any signs of failureover initial period ofthree years. In this paper, laboratory results pertaining to microsilica (SF), ground granulated blast furnace slag (GGBS), epoxy coated rebars and calcium nitrite corrosion inhibitor are very conclusive. Results affirmed that the supplementary cementing materials such as GGBS and SF significantly impacted and enhanced concrete resistivity to chloride ions penetration and hence decrease the corrosion activities on steel bars protected by such concretes. As for epoxy coated rebars applications under high chloride laden conditions, results showed great concern to integrity of the epoxy coating layer on the bar and its stability. On the other hand corrosion inhibiting admixtures such as calcium nitrite proved to be more effective when used in combination with the pozzolanic additives such as GGBS and microsilica.

Time dependence and service life prediction of chloride resistance of concrete coatings

This study aims to determine the effects of coating category and degradation on chloride resistance and service life of concrete coatings. Four typical coatings were applied on concrete specimens, and aged under outdoor natural climate conditions and indoor artificial accelerated experiments using ultraviolet light radiation and wetting/drying cycle. Coulomb electric fluxes of the specimens were periodically tested to determine their chloride resistance before and during aging. The chloride resistance of concrete is remarkably improved with the use of coatings, and organic film coatings provide superior improvement to infiltrating coatings. The chloride resistance of coatings is time-dependent, and organic film coatings exhibit faster aging than infiltrating coatings. The experimental time needed for coating degradation can be shortened through artificial accelerated aging experiments. The service lives of concrete coatings against chloride resistance are closely related and can be predicted through sunlight irradiance of the service environment.

Technique for quality assessment of external appearance of paint coatings

The data on the regularities of making an external appearance quality of coatings on a cement substrate has been given. The regularities of changing the surface roughness of cement concrete paint coatings, depending on the rheological properties of paints, cement porosity of the substrate, the way of applying paints, have been determined. The increase of the surface roughness of coatings with decreasing conditional dynamic viscosity of paints has been found out. Based on probabilistic and deterministic approaches the model of external appearance quality of coatings, taking into account the surface porosity of the substrate and the surface tension of paint, has been proposed. It has been suggested assessing the quality of paint coating surfaces by a fractal dimension indicator. The relation between numerical values of the fractal dimension indicator and the quality class of external appearance of coatings has been found. The model of profile length of the coating surface from the D fractal dimension has been proposed.

Self-Assembling Particle-Siloxane Coatings for Superhydrophobic Concrete

We report here, for the first time in the literature, a method to synthesize hydrophobic and superhydrophobic concrete. Concrete is normally a hydrophilic material, which significantly reduces the durability of concrete structures and pavements. To synthesize water-repellent concrete, hydrophobic emulsions were fabricated and applied on portland cement mortar tiles. The emulsion was enriched with the polymethyl-hydrogen siloxane oil hydrophobic agent as well as metakaolin (MK) or silica fume (SF) to induce the microroughness and polyvinyl alcohol (PVA) fibers to create hierarchical surfaces. Various emulsion types were investigated by using different mixing procedures, and single- and double-layer hydrophobic coatings were applied. The emulsions and coatings were characterized with optical microscope and scanning electron microscope (SEM), and their wetting properties, including the water contact angle (CA) and roll-off angle, were measured. A theoretical model for coated and non-coated concrete, which can be generalized for other types of materials, was developed to predict the effect of surface roughness and composition on the CA. An optimized distance between the aggregates was found where the CA has the highest value. The maximal CA measured was 156° for the specimen with PVA fibers treated with MK based emulsion. Since water penetration is the main factor leading to concrete deterioration, hydrophobic water-repellent concretes have much longer durability then regular concretes and can have a broad range of applications in civil and materials engineering.

Performance of Steel Pipeline with Concrete Coating (Modeled with Concrete Damage Plasticity) Underseismic Wave Passage

The paper presents the analysis of the dynamic response of a steel pipeline with concrete coating to a real earthquakeregistered in central Poland in 2012. The peak ground acceleration of the shock was scaled up to maximal values predicted for this seismic zone. To represent theinelastic behavior of the material of the concrete coating under dynamic loading, the concrete damaged plasticity constitutive model was assumed.The modelallows to describeplastic strains and irreversible tensile and compression damage that occurs during the cracking process.For seismic analysis two models (uniform and non-uniform) of kinematic excitation were applied. In the modelof uniform excitation it was assumed that the motion of all supports was identical. Inthe model of non-uniform excitation, typical for long structures, the wave passage along the pipelinewith different velocities (500, 400 and 300 m/s) was taken into account. It occurred that for the model of uniform excitation the concrete material of the coating remained elastic with no tensile damage. For the model of non-uniform excitation, inelastic behaviour of the coating was observed. The plastic strain areas appeared above all supports. The tensile damage (cracking) wasalso noticed in these areas: the lower wave velocity was assumed, the greater area of concrete coating was affected by plastic strains and tensile damage (cracking). It was the consequence of the quasi-static effects which resulted from ground deformations imposed on the pipeline during the seismic shock.

Effect of polymer modified cementitious coatings on water and chloride permeability in concrete

Concrete coatings are widely used to improve durability of reinforced concrete structures in order to prevent and control reinforcement corrosion in chlorides containing environment. Cement-based coatings, as well as organic-based coatings, act as a physical barrier to the penetration of water, ions and gases. In this paper, the permeability of concrete, coated with commercial polymer-modified cementitious mortars with two different polymer-to-cement ratios, to water and chlorides was evaluated as a function of water absorption, chloride diffusion, chloride penetration rate and coating adhesion properties. Tests were performed on coated concrete specimens as well as on coating layers. The effect of physical barrier to chloride penetration and the ability to decrease water content into concrete were discussed, as well as the influence on the service life of reinforced concrete structures.

Research on the Formula of Polyaspartic Ester Polyurea Concrete Coating and its Application

Its of great importance to develop various outstanding protective concrete coating with favorable impermeability and crack-resistance properties. In this study, the polyaspartic ester polyurea was prepared, and its adhesion to concrete was evaluated by universal testing machine and SEM technology. The optimal formula of polyurea was obtained by investigating the effects of each component's content on the bonding strength to concrete and the water contact angle. Subsequently, the mechanical and surface properties of these polyurea coating were tested. The results showed that the polyurea was obtained by the following formula: the weight ratio of A1/A2/B was 0.612/ 0.408/ 1, and the fluoride filler content was 3%. The coating exhibited excellent mechanical properties, such as high bonding strength (4.5 MPa), sufficient tensile strength (16.4 MPa) and elongation at break (456%). Meanwhile, the coating showed a hydrophobic surface with its water contact angle of 105°. Hence, the polyurea coating is likely to improve the crack-resistance and impermeability properties of hydraulic concrete. Till now, the polyurea coating has been applied to the concrete repair and protection engineering in the South-to-North Water Transfers Project.

Long-term chloride-induced corrosion monitoring of reinforced concrete coated with commercial polymer-modified mortar and polymeric coatings

The efficiency of four commercial concrete coatings (a polymer modified cementitious mortar and three elastomeric coatings) against chloride-induced corrosion is discussed by means of steel corrosion long-term monitoring and by chlorides penetration profiles in concrete. The cement-based coating shows the best effect on delay chlorides penetration in concrete by acting as a physical barrier in addition to concrete cover. Despite its lower polymer content, the higher thickness guarantees a longer time-to-corrosion with respect to organic coatings. Once corrosion has started, corrosion rate is lower in the presence of coatings, due to their ability to reduce water ingress in concrete.

A Comprehensive Parametric Finite Element Study on the Development of Strain Concentration in Concrete Coated Offshore Pipelines

The strain concentration at the field joint (FJ) of the commonly used concrete coated offshore pipelines is considered and discussed in this paper. The details of a 3D finite element (FE) modeling framework, developed using the commercial software ABAQUS, are presented. The numerical results are verified against the experimental results available in the literature. The FE model considered in this study captures several nonlinear phenomena associated with the problem, including the plastic deformation of the steel and anticorrosion layer (ACL) material, the cracking and crushing of the concrete, and also the large deformation effects. The developed FE framework is subsequently used to perform a parametric study to assess the effect of each influencing parameter on the strain concentration factor (SCF) developed within the FJ region. The influence of the geometric features of the coated pipe and the relevant mechanical properties of the materials as well as various combined loading scenarios are investigated. Results indicate that pipeline diameter, thickness, and coating thickness affect the SCF more than the strength of either concrete coating or ACL. Also, the postyield properties of the steel, especially the strain hardening capacity, may significantly influence the SCF. The combination of the internal pressure loading (causing a biaxial stress state) or tensile loading with the primary bending load is found to also increase the SCF significantly after steel yielding is initiated. Moreover, these combined loading scenarios cause different and more severe plastic deformation patterns in the FJ.

Influence of temperature on crack-bridging ability of coatings for concrete

The crack-bridging properties of different organic coatings have been studied over a range of thicknesses and applied temperatures. In each case the data allowed to determine linear relationships between crack-bridging ability (CBA) and coating thickness. In addition, a direct correlation between crack bridging ability and elongation at break of the unsupported films has been found, once verified that adhesion properties do not change over temperature.

Study on the Influence of Painting Processes on the Protective Property of Concrete Coating

With the development of construction project the durability of concrete is becoming more and more prominent, and surface coating is an effective measure to enhance the durability of concrete. Water-based silicone acrylic emulsion coating and water-based fluorocarbon resin coating were chose as prime and topcoat respectively. The impact of the coating’s thickness and viscosity on the durability of concrete and the relationship between the viscosity of the coating and its penetration depth were testified by chloride ion permeability-resistance property of concrete. The results show that thickness is proportional to the protective performance of the coating, and the penetration depth highly depends on viscosity. And the result of coating-4 viscosity method shows that samples with viscosity between 15 and 25 seconds have better chloride permeability resistance.

Biodeterioration of Pipeline Concrete Coating Material by Iron Oxidizing and Sulphate Reducing Bacteria

Biodeterioration/biocorrosion of concrete pipeline coating material by sulphate reducing bacteria (SRB) and Iron oxidizing bacteria was tested in the laboratory. The sulphate reducing bacteria and the Iron oxidizing bacteria were isolated from water samples collected from a swamp at a depth of 30 cm. The water samples had a viable, culturable, heterotrophic bacterial count of 1.2 x 10 3 cfu/ml for the sulfate reducing bacteria (SRB) and 4.0 x 10 3 cfu/ml for the Iron oxidizing bacteria. A loop-full of discrete colonies of the isolates of the two groups were used to initiate the biodeterioration tests. The pH of the set ups with the SRB showed a change in acidity from 8.24 in the fresh medium to 6.79 after 7 days and moved down to 5.23 in 28 days of incubation. In contrast, the pH of the set ups with Iron oxidizing bacteria showed an increase in alkalinity. The pH of the fresh Winogradsky medium changed from 6.60 to 7.80 in 7 days of incubation and to 9.02 after 28 days. The dissolved Iron II ion in the two set ups showed a gradual decrease in concentration as the time of incubation increased. The conductivity in the SRB set up increased from 0.41 s/m to 1.56 s/m in 28 days of incubation. On the other hand, the Iron oxidizing bacteria set up showed a decrease in conductivity from 1.12 s/m to 0.35 s/m in 28 days of incubation. The surfaces of the coupons of the concrete coating material used in the biodeterioration testing were slimy on touch indicating possible biofilm formation. There were changes in the physical appearance of the materials such as colour and texture. Corrosion rates were 0.6382 mpy and 0.3469 mpy for SRB and Iron bacteria respectively. Concrete coating of pipelines is a good strategy for swamp operations. The low rate of biodeterioration/biocorrosion of the concrete coating as indicated in this study is a useful piece of information for oilfield applications.

Evaluation of Hydrophobic Concrete Coatings in Tropical Marine Environments

This paper reports a six-year field- and laboratory-based study carried out to compare the performance of three proprietary hydrophobic coating systems (silane- and siloxane-based coatings), designed to reduce chloride ingress and reinforcement corrosion. Their behavior in the laboratory was also compared by using concrete of two different mixes (water-to-concrete [w/c] = 0.40 and 0.65). Field tests were carried out on a Portland I cement concrete with a w/c ratio of 0.4 and exposed to a very aggressive tropical marine environment. Six reinforced concrete probes (two per coating) of 15 by 15 by 30 cm were placed in the exposure site. The rebars were placed into the probes to obtain concrete covers of 20, 25, and 30 mm. During the test period, evaluation of the environmental parameters was based on the methodology established by ISO Standard 9233. The evaluations of half-cell potential (Ecorr) and corrosion rates (icorr/linear polarization resistance technique) were determined monthly. Chloride concentration profiles were determined after a 5-year, 8-month exposure. The results showed that when siloxane-based coating is used, there is an improvement in the behavior of the concrete with respect to chloride ion penetration. The behavior of the coatings depends not only on the quality of the concrete, but also on the company who manufactured them.