Concrete Admixtures

SELECTION & SPECIFIC APPLICATIONS OF CONCRETE ADMIXTURES

Admixtures shall be selected carefully to alter the concrete properties to the requirement of job at site and shall be used judiciously according to specification and method of application to avoid adverse effect on concrete properties at fresh and hardened strata. After selecting the product, one should carefully choose the supplier, who can supply quality(…)

ADVERSE EFFECT OF CONCRETE ADMIXTURE

Adverse effects due to improper application : Admixtures are used extensively to produce high workable, high strength high performance and highly durable concrete with minimum cost. However, these admixtures are not used judiciously and with the poor knowledge of admixture among engineers at site results in the following adverse effect on concrete. Rapid slum loss(…)

CONCRETE CHEMICALS AND APPLICATIONS

Concrete Chemicals (Admixtures) and Applications Admixtures are materials other than cement, aggregate and water that are added to concrete either before or during its mixing to alter its properties, such as workability, curing temperature range, set time or color. Some admixtures have been in use for a very long time in concrete construction, such as(…)

FACTORS AFFECTING CONCRETE ADMIXTURES PERFORMANCE

The various factors which affect the performance of concrete admixtures are: 1. Type of super-plasticizer: The admixture will be more effective if molecular weight of the super-plasticizer is high. 2. Dosage: The quantity of admixture should be optimum. Excess of admixture may cause segregation or bleeding. It may also cause excessive retardation. The optimum does(…)

STANDARD CODES FOR CONCRETE ADMIXTURES

Standard Codes for concrete admixtures: Admixtures used should conform to the following relevant  standard codes. In reinforced concrete, the chloride ion of any admixture used should not exceed 2% by weight  of the admixture as determined in accordance with IS:6925 and the total chloride ion in all admixtures used in concrete mi shall not exceed(…)

PROPERTIES AND USES OF CONCRETE ADMIXTURES

What are Concrete Admixtures? Ingredients other than cement, water, and aggregates that impart a specific quality to either plastic (fresh) mix or the hardened concrete (ASTM C496) is called concrete admixture. Why use Concrete Admixtures? 1. Reduce cost of concrete construction 2. Achieve specific concrete properties more effectively 3. Ensure quality of concrete during mixing,(…)

FUNCTIONS OF CONCRETE ADMIXTURES

Concrete admixtures are added to change the properties of concrete to make it function as required. Admixtures are used to modify properties of both fresh and hardened concrete as discussed below: Functions of admixtures to modify fresh concrete properties: a) To increase workability without increasing water content or to decrease the water content at the(…)

ACCELERATING WATER-REDUCING CONCRETE ADMIXTURES

Accelerators increase the initial rate of chemical reaction between the cement and the water so that the concrete stiffens, hardens, and develops strength more quickly. They have a negligible effect on consistence, and 28-day strengths are seldom affected. Accelerating admixtures have been used mainly during cold weather when the slowing down of the chemical reacting(…)

RETARDING WATER-REDUCING CONCRETE ADMIXTURE

Retarding water-reducing admixtures are chemicals that slow down the initial reaction between cement and water by reducing the rate of water penetration to the cement and slowing down the growth of the hydration products. The concrete therefore stays workable longer than it would otherwise. The length of time during which a concrete remains workable depends(…)