Pick up the incorrect statement from the following:
(A) Admixtures accelerate hydration
(B) Admixtures make concrete water proof
(C) Admixtures make concrete acid proof
(D) Admixtures give high strength
The correct answer and explanation is :
The incorrect statement from the given options is:
(B) Admixtures make concrete waterproof.
Explanation:
Admixtures are materials added to concrete during the mixing process to modify its properties. However, the statement that admixtures make concrete waterproof is not entirely accurate. Let’s analyze each option one by one:
(A) Admixtures accelerate hydration:
This statement is correct. Some admixtures, specifically accelerators, speed up the hydration process of concrete. These are often used in cold weather conditions to ensure that concrete sets quickly, which is essential for early strength development. By accelerating the hydration reaction, these admixtures help concrete to harden and gain strength faster.
(B) Admixtures make concrete waterproof:
This statement is incorrect. While some admixtures can improve the water resistance of concrete, they do not make concrete entirely waterproof. Waterproofing concrete is typically achieved through the use of special admixtures, coatings, or membranes that are designed for that specific purpose. These are often referred to as waterproofing admixtures, but they do not guarantee absolute impermeability. Concrete’s inherent porosity, which allows water to seep through, can only be reduced but not entirely eliminated by general admixtures.
(C) Admixtures make concrete acid-proof:
This statement is correct in a specific context. Some chemical admixtures, like those based on silica fume, fly ash, or special additives, can enhance the durability of concrete and provide resistance to acidic conditions. These admixtures help reduce the permeability of the concrete, making it more resistant to acid attack. However, concrete will still need proper mix design and curing to achieve acid resistance effectively.
(D) Admixtures give high strength:
This statement is generally true. Certain admixtures, such as superplasticizers, can improve the workability of concrete without adding extra water. This allows for a denser mix with less porosity, which results in higher strength concrete. Additionally, pozzolanic materials like fly ash or silica fume can also contribute to increased strength over time by reacting with lime to form more durable products.
Conclusion:
Admixtures alone do not guarantee that concrete will become waterproof. Therefore, option (B) is the incorrect statement.