Sandberg – The Use of Isothermal and Semi-Adiabatic Calorimetry to Study Cement Hydration Kinetics-Pros and Cons
Paul Sandberg (firstname.lastname@example.org)
Isothermal calorimetry has, because of its ease to use, become standard equipment in many laboratories researching cementitious systems. ASTM C1679 was recently published as a standard practice for the use of isothermal calorimetry to research the effect of admixtures and other ingredients on cement hydration kinetics. The temperature control enables easy testing of temperature effects on hydration kinetics, which is critical not only for understanding causes of cement-admixture interactions but even more so when high levels of cement replacement materials and admixture are used to reduce the CO2 footprint of concrete. The need for easy and practical test methods for the concrete practitioner led to several attempts to develop low-cost “field” calorimeters for quality control and testing of the effect of material changes on the rate of temperature rise as an indication of the onset of development of mechanical properties. Fundamental modeling of portland cement hydration with water is promising – but the industry needs practical tools for easy testing while the science is developing for an increasingly complex material. A recent Round Robin study on the use of semi-adiabatic calorimetry to estimate setting time in concrete attracted more than 50 participants from 12 laboratories, which underscores the need for simple and practical test methods in the field. An ASTM standard practice for the use of semi-adiabatic calorimetry is currently under development. This presentation discusses some evolving calorimetry applications for testing hydration kinetics of cementitious systems in the lab and the field, and also discusses some limitations of its use.