Influence of mechanochemical activation on the rheological, fresh, and mechanical properties of one-part geopolymer grout

Abstract

One-part geopolymer (OPG) grout offers advantages over two-part geopolymer grout concerning the handling and storage of feedstocks. This is mainly due to the large quantities of caustic solutions that should be handled for producing two-part geopolymer. However, OPG often suffers from a low degree of reaction, a high number of crystalline byproducts, and as a result, low strength. In this research, one-part geopolymer has been assisted by a mechanochemical activation (MC-OPG) to produce grout. In this method, the precursor material (slag and fly ash) and sodium silicate were mechanochemically activated utilizing co-grinding to produce a geopolymeric precursor, after which water is the only additive required to initiate the geopolymerization reaction. The effects of slag/fly ash ratios on grout mixtures were also investigated. A series of tests were examined, such as rheological characteristics, setting time, bleeding, unconfined compressive strength (UCS), ultrasonic pulse velocity (UPV), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The experimental results showed that the mechanochemical activation technique increased the rheological characteristics and reduced the fresh properties (setting time and bleeding) of geopolymer grout compared to the one-part geopolymer. Considering mechanical properties, the UCS of MC-OPG grout was higher (41%-73%) than that of OPG grout. Furthermore, slag content significantly affected the rheological, fresh, and mechanical properties of all the geopolymer grouts regardless of the activation method.