Cause Of Premature Deterioration Research Articles

Calibration of ductile and shear damage models for carbon and stainless steel shear studs

AbstractSteel‐concrete composite beams are commonly used in bridge construction. The corrosion of the supporting steel beams and the shear connectors are however known as a major cause of premature deterioration of composite bridges. Stainless steel beams and shear connectors offer a viable alternative solution to the steel corrosion problem in composite bridges located in harsh environmental conditions. This paper presents experimental and numerical investigations of the tensile and shear behaviour of stainless steel welded shear connectors. The results of tensile coupon and double shear tests on stainless steel and carbon steel shear connectors to characterise the tensile and shear response are reported. Numerical modelling is carried out using the ABAQUS finite element software to develop calibrated ductile damage and shear damage fracture models for stainless steel shear connectors. The development and validation of the numerical models together with the calibration of the fracture models are presented and comparisons are made with those of carbon steel shear connectors.

Evaluation of the water penetration depth in mortar using water indicator and hyperspectral imaging

Water penetration is a potential cause of premature deterioration of reinforced concrete structures. The water indicator used for water detection cannot detect water penetration depths in samples containing high amount of blast furnace slag (BFS). Hence, hyperspectral imaging (HSI) was introduced in this study. Mortar specimens with different water-to-binder (w/b) ratios and BFS replacements were prepared. The moisture content distribution, water indicator, and HSI were used to measure the water penetration depth in the samples after water absorption exposure. The effects of the pore size and moisture content on the mechanisms of the water indicator were also investigated. HSI successfully detected the penetration depth of water in all mortar samples, even in those where detection by using the water indicator was not possible. The moisture content distribution and HSI yielded similar results for water penetration depths. The water penetration depths measured by applying the water indicator and HSI were similar in the mortars without BFS substitution. The water indicator underestimated the water penetration depths in the samples that contained BFS. The amount free water in the pores of mortar was the main factor controlling the applicability of the water indicator.

Preventive Measures of Alkali–Silica Reaction in Concrete Buildings: Use of Hybrid Waste Coal Ash and Steel Wire Cut Fibers

The main cause of premature deterioration in concrete buildings is linked with the alkali–silica reaction (ASR) owing to the use of reactive aggregates and severe exposure conditions. This research aimed to explore the mitigation of ASR in concrete buildings using waste coal ash (CA) and steel fibers cut from long wire. CA and SF were acquired from a local market. The studied dosages of CA were 10%, 20%, 30% and 40% by cement weight and steel fibers were added at 0.5% and 1% of the total volume of the mixture. Specimens were cast and immersed in a 1N NaOH solution at 80 °C for 90 days as per ASTM C1260 guidelines. The compressive and flexural strengths of the control mixture without CA and the mixture with 10% of CA had a comparable behavior. A decrease in the compressive and flexural strengths was observed for higher dosages of CA (30% and 40%). Specimens incorporating 30% of CA showed a compressive strength of 24 MPa at 56 days compared to that of 33 MPa for the identical control specimen without CA. This strength decrease was due to the porous nature of the used CA and was compensated for by the incorporation of steel fibers. Specimens with 1% of steel fibers exhibited higher strength properties compared to those with 0.5% of steel fibers for all the tested dosages of CA. The control specimens without CA and steel fibers showed expansions higher than 0.10% and 0.20% at 14 and 28 days, respectively, demonstrating their reactive behavior. The hybrid incorporation of CA and steel fibers decreased the ASR expansion. The mortar bar specimen incorporating 10% of CA and 1% of steel fibers showed an expansion of 0.168% at 28 days compared to that of 0.321% for the control specimen without CA and steel fibers. A decrease in the compressive and flexural strengths was observed for the specimen placed in ASR exposure conditions compared to identical specimens placed in normal water. However, specimens incorporating CA and steel fibers showed relatively fewer effects under the ASR exposure conditions. The control specimens without CA and steel fibers also showed micro-cracking due to ASR exposure, as observed through scanning electron microscopy. This study will assist practitioners to construct a sustainable building using locally available waste materials with the additional advantage of mitigating the ASR-related damages.

Experimental and numerical investigation of the cyclic response of stainless steel reinforced concrete columns

Corrosion of carbon steel reinforcement is the major cause of premature deterioration of reinforced concrete infrastructures. There is increasing interest in the use of maintenance-free materials such as stainless steel reinforcement in concrete, with inherent durability and resistance to various forms of corrosion and favourable mechanical properties, in particular high ductility and substantial strain hardening. This paper presents the results of the first large-scale testing programme on reinforced concrete columns with duplex EN 1.4462 stainless steel rebars. Three cantilever column specimens were tested, two with EN 1.4462 stainless steel reinforcing bars, subjected to constant compressive axial load plus (i) monotonic loading and (ii) lateral cyclic loading, and one B500 carbon steel reinforced control specimen. In addition, conventional pull-out tests and tensile tests were conducted for a comparative assessment of the bond-slip behaviour and mechanical properties of the reinforcing bars. Numerical modelling simulations were carried out with the open-source finite element analysis platform OpenSees to predict the nonlinear response of stainless steel reinforced concrete columns and the results were compared with the measured experimental performance data. The force–displacement global responses and the dissipated energy evolutions of the tested columns from the experimental and numerical models are presented and compared.

Compressive stress–strain behaviour of stainless steel reinforcing bars with the effect of inelastic buckling

The corrosion of steel reinforcing bars due to chloride ingress is the most common cause of premature deterioration of reinforced concrete structures. Stainless steel reinforcement in concrete is a promising solution to address these durability and sustainability issues as it is highly resistant to corrosion from chloride ions, and it does not rely on the high alkalinity of concrete or the presence of concrete cover for protection. Modelling and analysis of the nonlinear behaviour of reinforced concrete structural components relies heavily on the existence of constitutive material models to simulate the stress–strain response of the reinforcing bars and concrete accurately. In this paper, the stress–strain behaviour of stainless steel reinforcing bars with the effect of inelastic buckling is examined experimentally and numerically for the first time. Stainless steel reinforcing bars of 12 mm diameter with various slenderness ratios of austenitic EN 1.4301 and duplex EN 1.4362 grades are tested under tension and compression. A validated finite element model of reinforcing bar in compression is developed which is used to conduct parametric study. A new compressive stress–strain constitutive model for stainless steel reinforcing bars is proposed which is calibrated against the numerical simulation data.

Influence of Repair on Corrosion-Failure Modes of Square-RC Columns Located in Tidal Zone

AbstractChloride-induced corrosion is the main cause of premature deterioration and failure of RC structures in corrosive environments. Therefore, modeling chloride permeation and investigating dif...

Truck Weights on Municipal and National Roads without Weight Enforcement

One of the main causes of premature deterioration in pavement structures is overweight heavy vehicles. To characterize these vehicles, real loads of motor vehicles of more than four tons should be monitored, especially vehicles classified as C2 (2-axles, single units), C3 (3-axles, single units), T3-S2 (5-axles, single trailer) and T3-S3 (6-axles, single trailer) type, as they represent 99.5% of the Costa Rican truck fleet. This study includes six temporal weighing surveys on municipal roads and seven weighing surveys on national roads, comprising the weight of 525 and 554 trucks, respectively. On municipal roads, C2 vehicles with bulk and wagon body types are predominant (67% of surveyed vehicles), whereas on national routes T3-S2 vehicles predominate (42%). Likewise, it was determined that most of exceeding data correspond to vehicles transporting pit material, construction materials, and merchandise on both types of roads. Compared with municipal roads (8%), the percentage of overweight vehicles is more than twice that on national roads (18%) where weight regulations are not enforced. To estimate updated and realistic load data that can be included in pavement design manuals and guides, the same results are provided in parameters such as truck factors and load spectra.

Service Life Prediction of Precast Concrete Structures Exposed to Chloride Environment

Chloride‐induced corrosion is widely accepted as one of the primary causes of premature deterioration for concrete structures in marine or deicing salt environment. For precast concrete (PC) structures, such durability problems may even be severer because defects in joint areas, e.g., cracks caused by grout shrinkage and improper construction, can accelerate chloride ion transportation process and may cause the interface shear failure when subjected to seismic load. By applying the path probability model (PPM) and reliability theory, a probabilistic framework was proposed to predict three limit states of PC structures, including corrosion initiation, serviceability limit state, and ultimate limit state. Using Monte Carlo simulation, a beam‐to‐column joint was further analyzed to illustrate the differences between PC structures and those cast in situ. The analysis indicates that corrosion initiation and serviceability limit state are sensitive to chloride diffusivity at connection area, and the higher pitting factor can significantly influence the bearing capacities of PC structures.

Deterioration of residential concrete foundations: The role of pyrrhotite-bearing aggregate

Premature deterioration of concrete foundations has been reported for a large number of homes in Eastern Connecticut of the United States. The characteristic symptoms are map cracking, whitish deposits at the vicinity of the cracking surface and wide crack opening. It is hypothesized that the volume expansion associated with the oxidation of pyrrhotite-bearing aggregate and the following internal sulfate attack (ISA) due to the delayed secondary mineral formation are the primary causes of premature deterioration. Extensive tests were carried out to validate the hypothesis using a combination of tools such as scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF) and energy dispersive X-ray (EDX).The results showed that pyrrhotite and its oxidation products, such as ferrihydrite, goethite and sulfur, were present in or at the surface of the aggregates of the deteriorated concrete, suggesting the occurrence of pyrrhotite oxidation. Expansive secondary mineral formations (SMF) such as ettringite and thaumasite were also identified. The abundance of these SMFs, their spatial distribution in the open spaces together with their close association with matrix cracking suggest the cause of premature deterioration.

Micro-scale moisture distribution and hydrologically active pores in partially saturated asphalt mixtures by X-ray computed tomography

Moisture distribution is the cause of premature deterioration in asphalt mixtures. However, quantifying of complex moisture distributions and their relationships to hydraulic loading patterns and pore structure remain challenging. This study is aimed to (1) quantify 2D moisture distribution within the pore structure of asphalt mixtures using X-ray computed tomography, and to (2) investigate the hydrologically active pore characteristics related to various hydraulic loadings in asphalt mixtures. A dense-graded asphalt mixture with a maximum aggregate size of 13.2 mm was prepared in the laboratory. X-ray computed tomography technology was used to capture moisture distribution within samples under hydrostatic and hydrodynamic pressures. The characteristics of moisture distribution, including volumetric moisture content, degree of saturation, and void number were quantified by comparing pore structure before and after hydraulic action. Analysis of variance indicated that hydraulic loading pattern, hydraulic gradient, vehicular velocity, and vehicular loading significantly influenced moisture distribution characteristics. Within the same sample, the asphalt mixtures under hydrodynamic pressure had lower void number and greater volumetric moisture content/saturation degrees than those under hydrostatic pressure, especially with higher loading frequency and amplitude, indicating that vehicular loading action aggravates moisture infiltration into pavement and increases the possibility of moisture damage. The hydrologically active pore structure was also analyzed using moisture distribution characteristics under varied levels of hydrostatic/hydrodynamic pressure. Interestingly, the hydrologically active pore sizes of asphalt mixtures under various hydraulic pressures differ from each other and provide various flow pathways for moisture transport, leading to the diversity of moisture distributions. These results provide a quantitative evaluation of microscale moisture distribution characteristics in asphalt mixtures, and these characteristics have significant implications for moisture transport modeling and moisture-induced damage prediction in field asphalt pavement.

Experimental Study on Crack Width Evaluation of R.C Beams and Comparison with Various Codes

Development of cracks is the most common cause of premature deterioration in structures. For the design of reinforced concrete structures, crack width is one of the most important factors to be considered. It also affects the serviceability of reinforced concrete members. This paper presents the experimental study on crack width evaluation of R.C beams and comparison with various international codes. Following international codes: Eurocode2 1992-1 (2009), Egyptian Code ECP203-2007, ACI Code 318-95, 318-05, BS 8110-1997/IS: 456-2000 was used to calculate the crack width for comparison purpose.

Effect of Carbonation and Sulphate on Chloride Ingress in Cement Pastes and Concretes with Supplementary Cementitious Materials

The main cause of premature deterioration of reinforced concrete structures is the corrosion of steel bars, induced by chloride ions (for example in marine environment) and/or by carbonation (atmospheric CO2). At the same time, environmental-induced degradations of concrete can also affect the structure, such as sulphate attack. This can lead to the formation of ettringite, inducing expansion inside the materials and finally degradation. Carbonation, chloride and sulphate ingress are usually studied separately in the literature. This is not representative of in-situ conditions since they can occur at the same time and can have an influence on each other. In this paper, chloride ingress are studied for concretes and cement pastes partially carbonated or/and in presence of sulphate in chloride contact solution. The mixtures contain OPC alone or with supplementary cementitious materials (SCM). SCMs are here pozzolanic materials (Fly Ash or Metakaolin) or alkali-activated materials such as ground granulated blast furnace slag (GGBS). The materials, partially carbonated (2 months in chamber at 1.5 % of CO2) or not, are put in contact with chloride solutions in presence of sulphate. This study focuses on the apparent chloride diffusion coefficients, as well as chloride binding isotherms which are obtained by the profile method. In addition, some aspects of the microstructure and of the pore structure are investigated, by using Mercury Intrusion Porosimetry and 27Al NMR, in order to better understand the results obtained relatively to the apparent chloride diffusion coefficients and to the chloride binding. Chloride ingress increases when sulphates are present in the contact solution for all cement materials tested (partially carbonated or not). In addition, chloride ingress is faster when the material is partially carbonated before contact with chloride solution. It appears that both carbonation or presence of sulphate decrease chloride binding, thus explaining the results. The results show an evolution of the properties as a function of the cement replacement ratio by SCMs.

Sensitivity Analysis of Corrosion Rate Prediction Models Utilized for Reinforced Concrete Affected by Chloride

Chloride-induced reinforcement corrosion is one of the major causes of premature deterioration in reinforced concrete (RC) structures. Given the high maintenance and replacement costs, accurate modeling of RC deterioration is indispensable for ensuring the optimal allocation of limited economic resources. Since corrosion rate is one of the major factors influencing the rate of deterioration, many predictive models exist. However, because the existing models use very different sets of input parameters, the choice of model for RC deterioration is made difficult. Although the factors affecting corrosion rate are frequently reported in the literature, there is no published quantitative study on the sensitivity of predicted corrosion rate to the various input parameters. This paper presents the results of the sensitivity analysis of the input parameters for nine selected corrosion rate prediction models. Three different methods of analysis are used to determine and compare the sensitivity of corrosion rate to various input parameters: (i) univariate regression analysis, (ii) multivariate regression analysis, and (iii) sensitivity index. The results from the analysis have quantitatively verified that the corrosion rate of steel reinforcement bars in RC structures is highly sensitive to corrosion duration time, concrete resistivity, and concrete chloride content. These important findings establish that future empirical models for predicting corrosion rate of RC should carefully consider and incorporate these input parameters.

Dynamic Response Analysis for Two Typical Structures of Saturated Asphalt Pavements with 3D Finite Element Method

The combined effect of moisture and dynamic loading on asphalt mixtures has been recognized as one of the main causes of premature deterioration of flexible pavements. Based on porous medium theory, the asphalt mixture is regard as saturated porous material, and a three-dimensional finite element model is established to investigate dynamic response of two typical asphalt pavement structures, which are the semi-rigid asphalt pavement and the semi-rigid asphalt pavement with flexible base course. Then the spatial and temporal distribution of stress, strain and pore fluid pressure of the two structures are calculated, respectively. Analysis results show the superiority of semi-rigid asphalt pavement structure with flexible base course to the semi-rigid asphalt pavement in aspect of moisture resistance capability.

Effect of ground granulate blast-furnace slag on corrosion performance of steel embedded in concrete

Corrosion of steel in concrete is one of the major causes of premature deterioration of reinforced concrete structures, leading to structural failure. To prevent the failure of concrete structures because of corrosion, impermeable and high performance concretes should be produced various mineral admixtures. In this study, plain and reinforced concrete members are produced with mineral admixtures replacing cement. Ground granulated blast-furnace slag (GGBFS) has replaced cement as mineral admixture at the ratios of 0%, 25% and 50%. The related tests have been conducted at the ages of 28 and 90, after exposing these produced plain and reinforced concrete members to two different curing conditions. The unit weight, ultrasonic pulse velocity, splitting tensile and compressive strength tests are conducted on plain concrete members. Half-cell potential and accelerated corrosion tests are also conducted on reinforced concrete members. According to the test results, it is concluded that the curing age and type are important and corrosion resistant concrete can be produced by using GGBFS mineral admixture at the ratio of 25%.

Coupled Micromechanical Model of Moisture-Induced Damage in Asphalt Mixtures

The combined effect of moisture and mechanical loading on asphalt mixtures has been recognized as one of the main causes of premature deterioration of flexible pavements. This paper presents a micromechanical model of moisture-induced damage in asphalt mixtures. The model couples the effect of moisture diffusion and mechanical loading to quantify the level of damage within the mixtures. The mechanical properties of the materials are defined as a function of the amount of moisture content. The cohesive zone modeling technique is used to simulate adhesive damage at the aggregate-mastic interfaces. Damage is evaluated based on the location and time for crack initiation and propagation at the aggregate-mastic interfaces and on the level of strains and stresses within the bulk of the mastic. Results show that micromechanical models provide a better understanding of moisture damage mechanisms in asphalt mixtures and can guide the development of continuum damage models.

Effect of flexure induced transverse crack and self-healing on chloride diffusivity of reinforced mortar

Cracks in reinforced concrete are unavoidable. Durability is of increasing concern in the concrete industry, and it is significantly affected by the presence of cracks. The corrosion of reinforcing steel due to chloride ions in deicing salts or sea-water is a major cause of premature deterioration of reinforced concrete structures. Although, it is generally recognized that cracks accelerate the ingress of chlorides in concrete, a lack of consensus on this subject does not yet allow reliable quantification of their effects. The present work studies the relationship between crack widths and chloride diffusivity. Flexural load was introduced to generate cracks of width ranging between 29 and 390 μm. As crack width was increased, the effective diffusion coefficient was also increased, thus reducing the initiation period of corrosion process. For cracks with widths less than 135 μm, the effect of crack widths on the effective diffusion coefficient of mortar was found to be marginal, whereas for crack widths higher than 135 μm the effective diffusion coefficient increased rapidly. Therefore, the effect of crack width on chloride penetration was more pronounced when the crack width is higher than 135 μm. Results also indicate that the relation between the effective diffusion coefficient and crack width was found to be power function. In addition, a significant amount of self-healing was observed within the cracks with width below 50 μm subjected to NaCl solution exposure. The present research may provide insight into developing design criteria for a durable concrete and in predicting service life of a concrete structures.

Characterisation of coating on rebar surface using Hot-dip Zn and Zn-4.9Al-0.1 misch metal bath

The corrosion of rebar is one of the primary causes of premature deterioration of the concrete structure. The ideal option to overcome this situation would be to provide corrosion protection right at the time of manufacturing of the rebar before it is encased in the concrete and hence, warrants the use of corrosion resistance rebar. The present paper outlines characterisation of coating obtained on rebar surface from pure Zn and Zn-4.9Al-0.1 misch metal bath. The coating was characterised by SEM, EDS, Galvanostatic and XRD techniques. In case of pure Zn bath, distinct phases such as eta, zeta, delta and gamma 1 and gamma were identified in coating where as in case of Zn-4.9Al-0.1 misch metal bath no such distinctive phases were found. The coating obtained from Zn-4.9Al-0.1 misch metal bath was thinner and consisted of outer Al 2O 3 phase followed Zn–Al phase resulting in better ductility compare to the coating obtained from pure Zn bath. Comparative corrosion resistance performances of both types of coating respect to uncoated rebar were evaluated by salt spray and tafel test. were conducted in simulated aggressive chloride and concrete pore solution of coated and The coating obtained form Zn-4.9Al-0.1 misch metal bath was found to be more anodic and showed 1.5-3 times better corrosion resistance in concrete pore solution and 2.5 times better resistance against aggressive chloride attack compare to the coating obtained from pure Zn bath. Both the coatings dissolved in faster rate in highly alkaline environment (pH = 13.6) where as dissolution rate decreased with decrease of pH in pore solution. The sacrificial as well as barrier protection of Zn–Al alloy coating was found to be more effective than pure Zn coating. Both types of coated bars showed reduction in bond strength in concrete structure. It is attributed by the faster dissolution of the coating, leading to hydrogen gas evolution thereby creating a gap between the rebar surface and concrete structure.

Improving the durability of concrete by using inhibitors

Corrosion of steel in concrete is one of the major causes of premature deterioration of reinforced concrete structures, leading to structural failure. Various methods are being used to extend the service life of reinforced concrete structures, which include surface coatings to concrete surface, coatings to the reinforcement, cathodic protection, chloride removal and corrosion inhibitors. Of these methods, the use of corrosion inhibitors is found to be one of the effective methods to control rebar corrosion. An attempt has been made to study the performance of the anodic inhibitors (sodium nitrite and zinc oxide), cathodic inhibitors (mono ethanol amine, diethanol amine and tri ethanol amine) and mixed inhibitors to control rebar corrosion. Compressive strength test, tensile strength test, chloride diffusion test and macro cell corrosion test were conducted by varying the type of inhibitors and varying the concentration of inhibitors. The addition of inhibitors not only increased the compressive strength of the concrete but also improved the corrosion resistance properties.

Alkali-aggregate reactivity in Newfoundland, Canada

Alkali-aggregate reactivity is a chemical reaction that occurs in some concrete structures. This reaction causes expansion and cracking of concrete. It may not be the main cause of premature deterioration; however, it is often the catalyst for other forms of deterioration. Since 1989, field work and laboratory testing for alkali-reactivity has been undertaken on selected aggregate, rock, and concrete core samples throughout Newfoundland. The field work and laboratory tests consisted of an assessment of the bedrock and aggregate sites to determine their quality and quantity for use as construction material; an examination of existing concrete structures to assess their durability with regard to alkali-aggregate reactivity. The site investigation of the concrete structures consisted of noting their date of construction, the rock and aggregate types used, the types of cracking, and the degree and type of deterioration of each structure. Results from laboratory testing, petrographic examination, and visual observation show that certain sedimentary, igneous, and metamorphic rock types may be potentially alkali-reactive, but the reaction may not always be deleterious to the concrete structure.Key words: alkali-aggregate reaction, concrete structures, laboratory tests, petrographic examination, rock types.