Table of Contents
What is chloride diffusion test?
The chloride diffusion coefficient is an indication of the capacity of any type of concrete to resist chloride penetration and is used to predict the service life of reinforced concrete structures.
How do you test for chloride in concrete?
Salt solution is drawn quickly in to the pores of the concrete. Also, the exposure of the bottom face to a 50 percent relative humidity environment during the test causes chlorides to be drawn into the concrete through a mechanism other than pure diffusion.
What is the permeability of concrete?
Permeability is a measure of the amount of water, air, and other substances that can enter the concrete matrix. Concrete contains pores that can allow these substances to enter or depart.
What is the durability of concrete?
Durability of concrete may be defined as the ability of concrete to resist weathering action, chemical attack, and abrasion while maintaining its desired engineering properties. Different concretes require different degrees of durability depending on the exposure environment and properties desired.
What is the effect of chloride on concrete?
At low concentrations, chloride ion has little or no effect on the physical stability of concrete structure but it causes the corrosion of the reinforcing steel in the concrete but at high concentration’ especially at low temperature, it causes expansion and cracking in the concrete.
How much chloride is cement?
The amount of chloride in the cement is controlled during the manufacturing process and is defined as 0.01% or less by weight of cement and also specified in the literature as 0.01% (Neville, 2004).
Does carbonation increase pH?
When you add carbon dioxide gas to it, it lowers the pH, making it acidic. For comparison purposes, water’s pH is 7, and seltzer or sparkling water with nothing added has a pH between a 3 or 4.
How can you reduce carbonation?
Carbonation can also be reduced by low water/cement ratio[1]. Low water/cement ratio and high strength concrete are possible by Self Compacting Concrete (SCC) where effect of carbonation is less comparatively. The carbonation is found to have tremendous impact on some of the engineering properties of concrete.
What factors affect permeability of concrete?
There are three major factors that influence the permeability of concrete :
- Water to Cement ratio. Ad.
- Compaction of Concrete. When concrete is adequately compacted, air-voids and trapped bleed water in concrete are eliminated.
- Curing of Concrete.
- Other Factors.
What is the pH of fresh concrete?
approximately 12 to 13
The pH of new concrete will be approximately 12 to 13 mostly due to calcium hydroxide, which is a normally by-product of cement hydration. As a concrete surface reacts with carbon dioxide in air, the pH of the surface gradually is reduced to about 8.5 through a process called carbonation.
Why does chloride cause corrosion?
road de-icing salts, etc. The chloride ions attack the passive layer and catalyze the corrosion process. Chloride ions breakdown the passive layer and cause pitting of the steel reinforcement.
What is chloride diffusion coefficient?
The chloride diffusion coefficient is an indication of the capacity of any type of concrete to resist chloride penetration and is used to predict the service life of reinforced concrete structures. Its determination has been subject of intense study in the last 50 years and today there is no complete agreement in the methodologies used.
What is the difference between diffusion and migration of chlorides?
Thus, while in diffusion, there is binding from when small quantities of chlorides are present, however in migration, only for chloride amounts higher than 20-30 gr/l reaction with cement phases starts to be significant, and only the isotherms equal when the external testing solution is 1M in NaCl (0.5% by concrete weight in the sample). OH-Ca++
Chloride Diffusion Test. The sawn surface of 100 mm diameter and 100 mm high concrete cylinders were placed in contact with a solution of sodium chloride. To prepare the samples, the curved surface of each cylinder was covered with a rubber coating in order to avoid moisture exchange and carbonation during the test.
What determines the rate of chloride ingress in concrete?
CONCEPTS ON THE CHLORIDE DIFFUSION COEFFICIENT C. Andrade Institute of Construction Science “Eduardo Torroja”, CSIC, Madrid, Spain Abstract Diffusion coefficient D, is considered the rate determining parameter of chloride ingress in concrete.