Sulfate and Chloride Resistance Properties of Portland Cement Blends

About 53% area of Bangladesh is alluvial deposited and affected by sulfate, salinity and chloride in water and soil. Existing sulfate and chloride can severely damage the building in coastal regions. In this paper durability of cement is evaluated on the basis of strength of mortar cube, concrete cylinder test. Besides the sulfate resistance is measured by change of length of the mortar bar specimens during exposure to sulfate solution and the attacking chloride properties by Rapid chloride ion penetration test using OPC, PCC, 20% FA, 30% FA and 40% FA. The strength was observed in cube sample about 40.65, 37.2MPa after 13 weeks in sulfate solution and linear expansion was obtained about 0.28% and 0.133% for OPC and PCC cement with reference to the water. The compressive strength of the cylindrical specimens was about 16.96, 18.34 MPa for OPC and PCC, respectively at the age of 28 days. The permeability of chloride ion of OPC sample was 22.8% higher than the PCC at this age. Journal of Engineering Science 12(1), 2021, 69-75

Effect of Curing Temperature on the Durability of Concrete under Highly Geothermal Environment

To determine the durability of concrete in the actual temperature and humidity of the tunnel environment, this study investigates the mechanical properties, permeability of chloride ion, relative dynamic elastic modulus, and mass loss ratio of concrete specimens cured in the temperature which varied from normal, 40, 60, 75, and 90°C, and the humidity was kept at 90% continuously. Experimental results reveal that the hot temperature curing environment may benefit early stage strength development but reduce the long-term strength. It is proved that 60°C is a critical point. At above 60°C, the strength of the concrete material and its resistance to chloride ion permeability showed a decreasing trend; however, in the appropriate temperature range, the frost resistance properties of the concrete are improved with increasing temperature.

Chloride Ion Diffusion Model of the Concrete under Multiple Factors

Durable life of concrete structures under the chloride environment depends on the permeability of chloride ion, and the chloride ion diffusion coefficient is the main indicator that reflects the permeability of chloride ion. Based on the Fick’s second law, a multi-factor model of the chloride ion diffusion is established. In this model, the influences of temperature, humidity, age of the concrete, fly ash and carbonation are taken into consideration. And the model is verified by engineering test data from the concrete structure under the wet and dry areas of marine. The results show that the calculated and measured values of the chloride ion content agree well, the actual situation of the project could be basically reflected. The multi-factor model of the chloride ion diffusion is practical.

Experiment Study on Concrete Resistance to Chloride Ion Penetration

The influence law of permeability of chloride ion in concrete of load level, curing condition under the sustained pressure load and the corrosion environment interaction is researched in this article, which is through natural diffusion method. Experimental results show that as the load level increases, there is a tendency of the chloride ion content after the first increase and then decrease, the turning point in the middle remains to be further studied. Good conservation condition reduces large holes and harmful holes in concrete block, thereby reduce the porosity and improve resistance to chloride ion erosion.

The Law of Penetration Research of Chloride Ion in Concrete under Chloride Environment and Sustained Load

This paper studies theinfluence law of permeability of chloride ion in concrete of experiment time,load level, curing condition under the sustained pressure load and thecorrosion environment interaction, which is through natural diffusion method.Experimental results show that with the extension of the test time, chlorideion permeability increases. As the load level increases, there is a tendency ofthe chloride ion content after the first increase and then decrease, theturning point in the middle remains to be further studied. Sufficient waterretention curing conditions, making holes in concrete block unhydratedparticles can continue to get the necessary hydration water, thus continuoushydration leads to increased porosity of roughness, but reduces the resistanceto chloride ion erosion.

The Experimental Research on the Anti-Corrosion Performance of Concrete with Different Mineral Admixtures under Sulfate and Chloride Environment

The performance of resistance to sulfate attack and permeability of chloride ion on concrete with different mineral admixtures (fly ash, slag single or both adding) under sulfate and chloride environment were discussed. The results indicated the performance of resistance to salt attack on concrete with appropriate mineral admixtures was improved. Under chloride environment, the resistance to sulfate attack coefficient of testing mortars descended, and compressive strength loss rate of concrete was raised after dry-wet cycles. Therefore, the performance of resistance to salt attack on concrete was decreased in this environment. Besides, on the initial stage of corrosion, the ability to resist chloride ion penetration of concrete was improved under sulfate environment, while the penetrating of chloride ion was accelerated on the later stage.

Influence of Splitting Load and Polypropylene Fiber on Permeability of Chloride Ion in Concrete

Orthogonal experiment is used to study the influence of splitting load and mixing of polypropylene fiber of different volume fraction, different length and different mass ratio of long and short fiber on permeability of chloride ion in concrete. The results show that the chloride ion diffusion coefficient increases as the stress ratio increasing, and the relationship between them approximately agrees with exponential function. The influences of fiber volume fraction and fiber length on permeability of chloride ion in concrete are significant, and using shorter polypropylene fiber in the range of low volume fraction can lower permeability of chloride ion in concrete, whereas long fiber and large volume fraction will increase the permeability. The effect of lowering permeability of chloride ion in concrete is most obvious, when the fiber volume fraction is 0.1%, the fiber length is the combination of 6mm and 9mm, and the mass ratio of long and short fiber is 1:2.

Influence of Flexural Loading on Permeablility of Chloride Ion and Diffusion Coefficients in RC Beams

The permeability of chloride ion in concrete can be studied using the accelerated aging method in a short period, but the influence of loading characteristic on chloride ion permeability and diffusion coefficients is not considered generally. Three RC beam (120 mm×240 mm×2400 mm) specimens with different flexural loading state are exposed in an artificial corrosion container filled with salt-fog of 5.0 % sodium chloride for 40 days, the chloride ion concentration in different depths of compressive and tensile region are measured, diffusion coefficients of different region concrete are fitted on the basis of Fick’s second law, the effect of flexural loading on chloride ion concentration and diffusion coefficients of concrete are analyzed. The results show that the effect of the flexural load influences permeability of chloride ion and diffusion coefficients of concrete, content of chloride and diffusion coefficients of concrete are controlled by loading level, and the bending load is one of the important factors that can not be ignored in the study of concrete durability.