How do you reduce sulfate attacks?
Protection against sulfate attack can be achieved by using concrete with low [P NO 247] permeability, using cements with a low C3A content and blends of Portland cement with pozzolans (thus reducing the available Ca(OH)2).
Which compound is mainly responsible for sulphate attack?
The compounds responsible for sulfate attack on concrete are water-soluble sulfate-containing salts, such as alkali-earth (calcium, magnesium) and alkali (sodium, potassium) sulfates that are capable of chemically reacting with components of concrete.
What is sulphate attack on brickwork?
SULPHATE ATTACK ON BRICKWORK. Sulphate attack in masonry is evident by horizontal cracking within mortar joints, and expansion of mortar causing disruption or even bowing of brickwork, plus crumbling of mortar. Sulphate attack on mortars is very rare and slow to develop, but can be costly to remedy.
How does gypsum form during sulfate attack?
Sulfate attack on Portland cement concrete is often said to arise from each of two major sulfate reactions: (1) The sulfate ions react with C3A and its hydration products to form ettringite with an increase in volume that results in expansion and subsequent cracking of the concrete; (2) The sulfate ions react with …
What is sulfate resistance?
Sulfate Resisting Cement is a blended cement designed to improve the performance of concrete where the risk of sulfate attack may be present. It also provides improved durability for concrete in most aggressive environments, reducing the risk of deterioration of the structure and structural failure.
How do you increase sulfate resistance in concrete?
To improve the sulfate resistance of concrete, lower C3A cements are available. ASTM C 150 Type II cement (MSR) with <8% C3A, and Type V cement (HSR) with <5% C3A are typically specified in sulfate environments.
What is internal sulphate attack?
Sulfate attack can be ‘external’ or ‘internal’. External: due to penetration of sulfates in solution, in groundwater for example, into the concrete from outside. Internal: due to a soluble source being incorporated into the concrete at the time of mixing, gypsum in the aggregate, for example.
Why do bricks fail?
The main cause of failures is rusting of metal ties, although there can be other causes, such as failure to properly bed the tie in the mortar joint, poor quality mortar reducing the bond between tie and mortar, or not installing the requisite number of ties.
What can I do about efflorescence?
Regular white vinegar with 5% acidity works fine. With a sponge, apply vinegar to the area with efflorescence and clean it a circular motion. Leave the solution on the area for 10 minutes before rinsing the area thoroughly with water. Vinegar works best on surfaces like stucco, but can also work on concrete and bricks.
Is sulphate attack covered by insurance?
Sulphate attack is not normally covered by buildings insurance as it tends to be excluded by means of a clause exempting all forms of chemical attack. However, where it is possible to prove that an escape of water such as a cracked drain has triggered the reaction the insurance claim may be successful.
Why is sulfate resisting cement used?
When do you use sulphate resisting cement?
Sulfate-resisting cement is recommended for use in all concrete, mortar and grout below ground or where sulfates are present in concentrations likely to lead to deterioration as described previously (except for class DC-4m).
What’s the process and control of a sulphate attack?
Sulphate Attack on Concrete – Process and Control of Sulphate Attack. Home/ Concrete Technology / Sulphate Attack on Concrete – Process and Control of Sulphate Attack. Sulphate attack on concrete is a chemical breakdown mechanism where sulphate ions attack components of the cement paste.
What does sulfate attack mean in concrete terms?
Sulfate attack is a common form of concrete deterioration. It occurs when concrete comes in contact with water containing sulfates (SO4).
Are there any documented cases of sulfate attack?
In a small number of documented cases worldwide, 317–320 a particular form of sulfate attack has been reported where concrete had been designed to resist sulfates.
Is the sulphate attack a cosmetic or physical problem?
It is not only a cosmetic problem, but it is the visible displaying of possible chemical and microstructural problems within the concrete matrix. Both chemical and physical phenomena observed as sulphate attack, and their separation is inappropriate.