Anthropogenic Carbon Aerosol Induced Carbonation in Reinforced Concrete: Deterioration Effects on Mechanical Properties

The effects of corrosion on the reinforced concrete structure due to carbonation affect its operation life. The research work considers a major critical component causing global warming as it studies the links between reinforced concrete deterioration mechanisms and anthropogenic carbon aerosol (black carbon soot) emissions in the atmosphere. Experimental tests were carried out to study the effect of carbonation caused by the emission of black carbon soot on mechanical properties and durability of reinforced concrete. Mass concrete and reinforced concrete prepared with Ordinary Portland cement (OPC) in water/cement ratios ranging from 0.45 to 0.65 were used to produce concrete samples. Compressive strength tests, tensile strength test, and carbonation depth tests were carried out on concrete to determine its level of deterioration following the carbonation effect. The carbonation chamber was prepared with carbon soot of different concentrations to simulate different levels of black carbon soot in the atmosphere. Results showed that concrete compressive strength was not totally affected by carbonation, but there was reduction in the tensile strength of reinforcing steel. The carbonation depth was observed to progress deeper into the concrete with a longer duration of exposure to carbonation agents in the chamber. The result of this study will serve as a guide during concrete installations.

Durability assessment of concretes reinforced with steel and synthetic fibers in Colombia

In recent years, the use of steel fibers has increased in Colombia, optimizing structure designs, quality specifications and mechanical behavior. However, the concrete durability and resistance to aggressive environments such as sulfates and chlorides are not commonly evaluated. This paper includes results of durability analysis for 21 MPa compressive strength concretes reinforces with steel and synthetic fibers. Performance parameters measured during tests include sulfate resistance, chlorides penetration, and carbonation according to technical standards. The Variables of experimental program were fiber type and fiber dosage. Dosages for synthetic fibers were 1.5 kg/m3, 3.0 kg/m3 and 5.0 kg/m3, and for steel fibers were 5.0 kg/m3, 9.0 kg/m3 and 18 kg/m3. Results of the study were used to propose recommendations for reducing concrete deterioration when exposed to these aggressive environments and for extending the durability service life.

Study on Concrete Deterioration in Different NaCl-Na2SO4 Solutions and the Mechanism of Cl− Diffusion

The diffusion of sulfate (SO42−) and chloride (Cl−) ions from rivers, salt lakes and saline soil into reinforced concrete is one of the main factors that contributes to the corrosion of steel reinforcing bars, thus reducing their mechanical properties. This work experimentally investigated the corrosion process involving various concentrations of NaCl-Na2SO4 leading to the coupled erosion of concrete. The appearance, weight, and mechanical properties of the concrete were measured throughout the erosion process, and the Cl− and SO42− contents in concrete were determined using Cl− rapid testing and spectrophotometry, respectively. Scanning electron microscopy, energy spectrometry, X-ray diffractometry, and mercury porosimetry were also employed to analyze microstructural changes and complex mineral combinations in these samples. The results showed that with higher Na2SO4 concentration and longer exposure time, the mass, compressive strength, and relative dynamic elastic modulus gradually increased and large pores gradually transitioned to medium and small pores. When the Na2SO4 mass fraction in the salt solution was ≥10 wt%, there was a downward trend in the mechanical properties after exposure for a certain period of time. The Cl− diffusion rate was thus related to Na2SO4 concentration. When the Na2SO4 mass fraction in solution was ≤5 wt% and exposure time short, SO42− and cement hydration/corrosion products hindered Cl− migration. In a concentrated Na2SO4 environment (≥10 wt%), the Cl− diffusion rate was accelerated in the later stages of exposure. These experiments further revealed that the Cl− migration rate was higher than that of SO42−.

Effect of the Mechanical Load on the Carbonation of Concrete: A Review of the Underlying Mechanisms, Test Methods, and Results

As one of the major causes of concrete deterioration, the carbonation of concrete has been widely investigated over recent decades. In recent years, the effect of mechanical load on carbonation has started to attract more attention. The load-induced variations in crack pattern and pore structure have a significant influence on CO2 transport which determines the carbonation rate. With different types of load, the number, orientation, and position of the induced cracks can be different, which will lead to different carbonation patterns. In this review paper, the carbonation in cracked and stress-damaged concrete is discussed first. Then, literature about the effect of sustained load during carbonation is compared in terms of load type and load level. Finally, the advantages and disadvantages of possible test methods for investigating the effect of sustained load on carbonation are discussed with respect to loading devices, load compensation, and specimen size.

Deterioration and Protection of Concrete Elements Embedded in Contaminated Soil: A Review

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.

Assessing Deteriorated Concrete Structures

In today’s society, concrete structures are deteriorating for a variety of reasons. In order to properly repair these structures, it is important to completely understand the root cause of each type of deterioration. Over the years, engineers have developed methods for identifying the causes of concrete failure. This paper recognizes the different forms of concrete deterioration, identifies the test methods which have been developed to locate these concrete defects (both non-destructive and destructive), reviews different case studies which have been performed on concrete parking structures implementing these test methods and draws conclusions from surveys which were conducted of professionals in the rehabilitation engineering field. Additionally, this research project develops a strategy which is meant to aid with the selection of concrete test methods to be used in diverse concrete deterioration situations.

A study into the effects of test variables on the results of concrete tests for salt scaling and alkali-silica reaction

The ability to accurately determine in-service deterioration of concrete remains an important facet of research. This research aims to develop more reliable laboratory testing methods to better replicate in-service conditions. Two concrete deterioration modes were studied; Salt Scaling (SS) and Alkali-Silica Reaction (ASR). For SS, wrapping slabs in plastic was adopted to provide the same curing environment as curing compound for comparison to standard moist curing. Slabs with and without supplementary cementing materials were tested. The two curing methods produced different scaling results; however, results of tested samples did not change in terms of meeting or failing the acceptance limit. For ASR, modified tests focused on changing sample size to attempt to reduce alkali leaching during testing, and hence produce results that mimic long term performance of actual structures. Cube moulds were designed, manufactured, and used rather than standard prisms. Increase of specimen dimension appear to reduce leaching at 38°C.

A study into the effects of test variables on the results of concrete tests for salt scaling and alkali-silica reaction

The ability to accurately determine in-service deterioration of concrete remains an important facet of research. This research aims to develop more reliable laboratory testing methods to better replicate in-service conditions. Two concrete deterioration modes were studied; Salt Scaling (SS) and Alkali-Silica Reaction (ASR). For SS, wrapping slabs in plastic was adopted to provide the same curing environment as curing compound for comparison to standard moist curing. Slabs with and without supplementary cementing materials were tested. The two curing methods produced different scaling results; however, results of tested samples did not change in terms of meeting or failing the acceptance limit. For ASR, modified tests focused on changing sample size to attempt to reduce alkali leaching during testing, and hence produce results that mimic long term performance of actual structures. Cube moulds were designed, manufactured, and used rather than standard prisms. Increase of specimen dimension appear to reduce leaching at 38°C.

Assessing Deteriorated Concrete Structures

In today’s society, concrete structures are deteriorating for a variety of reasons. In order to properly repair these structures, it is important to completely understand the root cause of each type of deterioration. Over the years, engineers have developed methods for identifying the causes of concrete failure. This paper recognizes the different forms of concrete deterioration, identifies the test methods which have been developed to locate these concrete defects (both non-destructive and destructive), reviews different case studies which have been performed on concrete parking structures implementing these test methods and draws conclusions from surveys which were conducted of professionals in the rehabilitation engineering field. Additionally, this research project develops a strategy which is meant to aid with the selection of concrete test methods to be used in diverse concrete deterioration situations.