New Tech for Acid Attack — Part 5
by Whitney B. Belkowitz and Jon S. Belkowitz, PhD
Summary and Conclusions
To get a better understanding how current and novel technologies influenced the grout mixtures, different dosages and combinations of these technologies were used. Ultimately, the grout specimens were more resistant to acid attack had a combined higher compressive strength and lower permeability. These hardened properties were achieved by reducing the w/c ratio and the cementitious paste content to effectively manipulate the HCM of the grout specimens. Metakaolin effectively increased strength and reduced permeability. Despite the fact that the Metakaolin densified and enhanced the grout to resist acid attack, there was a diminished return when using Metakaolin as a replacement for OPC. Beyond this maximum dosage of Metakaolin, the hardened properties and acid resistance did not seem to be enhanced significantly. With the addition of nano silica, there seemed to be an increase in the degree of hydration for the HCM and a reduction in permeability. This change in the HCM gave the most promising results to increase the strength and durability of grout. Ultimately, this research shows that to effectively increase the strength and durability of grout mixtures, the HCM needs to be densified. Altering the cement paste and aggregate content did not produce significant gains in the hardened properties to increase the resistance to acid attack. The molecular kinetics of cement hydration were effectively manipulated by the nano silica alone and in combination with the Metakaolin to yield a more durable HCM and cementitious grout. With these innovative technologies, it is possible to create a concrete that can resist acid attack for an increased service life.
The authors would like to express their gratitude to AkzoNobel, Inc for supplying the different Levasil CB products for this research project. Intelligent Concrete, LLC was gracious enough to conduct a multitude of experiments to complete the objectives of this research project.