The measured air contents of the three mixtures are provided in Table 2, along with their achieved degrees of hydration and compressive strengths. The control mixture exhibits the lowest air content as it was an extremely dry mixture that was somewhat difficult to mix and mold. In comparing the other two mixtures, it is observed that the mixture in which the SRA was added via the prewetted LWA has a significantly higher air content than the mixture where the SRA was added by conventional means. This specific SRA is known to have air detraining properties and the experimental results indicate that FLAIR delivery does have the potential to eliminate or reduce this potentially detrimental side effect of the SRA, when compared to conventional delivery via the mixing water. This example illustrates one potential advantage of FLAIR delivery of chemical admixtures versus conventional delivery in the mixing water, namely the mitigation or avoidance of potentially detrimental interactions between multiple admixtures or detrimental side effects of the admixture in the fresh concrete.
| Table 2- Measured physical properties of mortar mixtures. Numbers in parentheses for air contents and compressive strengths indicate standard deviation between two or three batches and measured coefficient of variation for three specimens, respectively. | |||
|---|---|---|---|
| Physical Property | Mixture 1 CONTROL | Mixture 2 FLAIR | Mixture 3 CONVENTIONAL |
| Air content | 3.4 % (0.6 %) | 8.3 % (0.4 %) | 5.1 % (0.4 %) |
| 7 d compressive strength (MPa) | 38.8 (2.8 %) | 36.5 (4.6 %) | 40.4 (6.0 %) |
| 28 d comp. strength (MPa) | 42.1 (6.7 %) | 41.0 (3.7 %) | 41.0 (4.5 %) |
| 91 d comp. strength (MPa) | 43.7 (4.5 %) | 42.6 (9.9 %) | 42.7 (11.4 %) |
| 7 d degree of hydration | 0.53 | 0.57 | 0.59 |
| 28 d degree of hydration | 0.57 | 0.66 | 0.66 |
| 91 d degree of hydration | 0.59 | 0.68 | 0.68 |