How much calcium chloride is allowed in accelerating admixtures?

Calcium chloride is a commonly used accelerating admixture in concrete to speed up the setting time and strength gain. However, its use is regulated due to potential negative effects on concrete durability and reinforcement. It is widely recognized that excessive use of calcium chloride can lead to issues such as corrosion of steel reinforcement, efflorescence, and reduced long-term strength.

The correct answer indicates that the allowable content of calcium chloride in accelerating admixtures should be 0%. This means that when used as an accelerating agent, calcium chloride should be completely avoided in order to maintain the integrity and long-term performance of the concrete. Many standards and guidelines recommend against the use of calcium chloride in certain situations, especially in reinforced concrete structures or in conditions where the concrete might later be exposed to water.

Understanding this guideline is crucial for compliance with industry best practices and building codes, which emphasize durability and safety in concrete construction. The other choices suggest varying percentages of calcium chloride that could be allowed, but the consensus in many standards is to avoid it altogether for the reasons outlined.