Recent University of Ottawa research demonstrates the effectiveness of Kryton International’s hydrophilic waterproofing products in critical conditions, including those where concrete mix designs must account for the risk of alkali-silica reaction (ASR) due to the presence of highly reactive aggregates. The four-year study investigates the performance of mix designs containing reactive aggregates, designated TX and SPH, along with Kryton’s products and supplementary cementitious materials (SCM). Investigators sought to evaluate or improve existing commercial products and develop new product(s) for preventing and/or mitigating concrete deterioration caused by ASR in its initial, moderate and advanced phases. They conclude:
- ASR kinetics, mechanical properties and microscopic changes are dependent on the aggregate’s type (i.e., fine vs. coarse aggregate). Samples incorporating the highly reactive TX sand were more damaged than SPH samples. Those containing TX developed more cracks in shorter periods due to their faster ASR-induced kinetics.
- The use of hydrophilic waterproofing crystalline admixture, either commercially available or modified versions, could change ASR kinetics and distress for both reactive aggregates used. It is believed that crystalline admixtures can start healing cracks, modify ASR kinetics and curtail further deterioration as soon as the cracks reach the cement paste.
- The combined use of different SCMs and crystalline admixtures is highly effective in mitigating ASR. Although the SCMs’ chemical composition plays a major role in the mitigation of ASR, the use of crystalline admixtures enhances the healing properties of the SCM-bearing concrete.
- The use of a crystalline admixture in combination with metakaolin and silica fume yields the best results, even better than the samples containing lithium nitrate.
Due to laboratory conditions and test method requirements, investigation samples were placed in a high humidity environment and the internal humidity did not decrease—counter to the usual field conditions. Hence, the research demonstrates the worst-case scenario for ASR development. Real-world results are expected to include hydrophilic waterproofing crystalline admixture’s ability to lower interior humidity and, therefore, enhance even more ASR mitigations.
Adapted from a University of Ottawa Structure report by Alireza Biparva, technical director of Kryton International Inc., Vancouver, B.C., www.kryton.com.
