R3 Revealed – Inside Views from Calcined Clay Calorimetry Brews

The R3 test method is currently experiencing rapid adoption worldwide as an essential tool for the assessment of potential supplementary cementitious materials for use in concrete. Originally developed for calcined clays, the resultant hydration phase assemblages have been well characterized by bulk techniques such as X-ray diffraction, thermogravimetric analysis, and nuclear magnetic resonance, but relatively less work has been dedicated to seeing, microscopically, the inner workings of the method. With this in mind, this foray into the formerly private world of calcined clay pastes was undertaken, to see what goes on behind those closed calorimeter chamber doors. Like some sort of scientific construction materials conference proceedings click-bait, this abstract is intended to whet the appetite of those who demand to know more about such elusive and camera-shy phases as monocarbonate and katoite. And for those who choose to turn the page, and succumb to such temptations: buckle your seatbelts for a twisted tortuous ride through hydrated paste pore structure, as revealed by fluorescent epoxy impregnation and scanning electron microscope images.