Concrete admixtures are substances that are added to the mixture of concrete or mortar during or immediately before its mixing. These materials, which exclude water, aggregates, hydraulic cement, and fiber reinforcement, are used to enhance the properties of concrete or mortar in both its plastic and hardened states.
Various codes, such as ACI, ASTM, and IS, offer specifications for the testing methods, properties, and applications of concrete admixtures. These codes must be followed to ensure that different types of concrete admixtures, including water-reducing admixtures, retarding admixtures, accelerating admixtures, water-reducing and retarding admixtures, water-reducing and accelerating admixtures, water-reducing high range admixtures, and water-reducing, high range, and retarding admixtures, conform to the appropriate standards. Failure to comply with these specifications can result in undesirable outcomes.
Types of Admixtures and Their Standard Codes
Table 1 Types of Admixtures used in concrete and mortar, and Standard Codes Pertaining to each Admixture
| Types of Admixtures | Standard Codes | Notes |
| Water-reducing (WR) | ASTM C 494/C 494M – 99 | This specification covers materials for use as chemical admixtures to be added to hydraulic-cement concrete mixtures in the field. stipulates tests of an admixture with suitable concreting materials or with cement, pozzolana, aggregates, and an air-entraining admixture. |
| WR | ACI 212.3R-10 | It is a complete report about almost all types of admixtures used in concrete and mortar. It discusses the materials, selection, evaluation, applications, proportioning concrete, effects on hardening concrete, effects on fresh concrete, quality assurance, and storage of concrete admixtures. |
| WR | IS:9103 | This standard covers the chemical and air entraining admixtures including superplasticizers, solid or liquid or emulsion, to be added to cement concrete at the time of mixing so as to achieve the desired property in concrete, in the plastic or hardened state. |
| WR | AASHTO M154 | — |
| Retarding (R) | ASTM C 494/C 494M – 99 | See the description in the first row of this table |
| R | ACI 212.3R-10 | Look at the explanation in the second row of this table |
| R | IS:9103 | Look at the explanation in the third row of this table |
| R | BS:5075 part 1 | — |
| Accelerating (A) | ASTM C 494/C 494M – 99 | See the description in the first row of this table |
| A | ACI 212.3R-10 | Look at the explanation in the second row of this table |
| A | IS:9103 and IS:2645 | Look at the explanation in the third row of this table |
| Water-reducing and retarding | ASTM C 494/C 494M – 99 | See the description in the first row of this table |
| Water-reducing and accelerating | ASTM C 494/C 494M – 99 | See the description in the first row of this table |
| Water-reducing high range (WRHR) | ASTM C 494/C 494M – 99 | See the description in the first row of this table |
| WRHR | IS:9103 | Look at the explanation in the third row of this table |
| WRHR | BS 5075: Part 3: 1985 | — |
| Water-reducing, high range, and retarding | ASTM C 494/C 494M – 99 | See the description in the first row of this table |
| Air entraining (AE) | ASTM C 260-00 | This specification covers materials proposed for use as air-entraining admixtures to be added to concrete mixtures in the field. It provides specifications regarding sampling, testing methods, and performance requirements. |
| ` AE | IS:9103 | Look at the explanation in the third row of this table |
| Integral waterproofing admixtures | IS:2645 | This type of admixture can be used with all types of concrete, mortars, masonry works, and guniting works, and shall conform to the specifications of IS:2645 |