Thermal Cracking in Early-age Low-clinker Concrete - A Parametric Study on the Early-age Behavior of Concrete With Supplementary Cementitious Materials

Abstract

This study is a master thesis at Chalmers University of Technology and aims to investigate which material parameters have the greatest impact on early-age thermal cracking in low-clinker concrete. It is a continuation on previous research conducted by collaborators from Chalmers University of Technology, NCC, Thomas Concrete Group and RISE, who identified which material parameters have the greatest impact on thermal cracking in concrete with ordinary Portland cement. The same material model and constitutive relations were adopted in this study. Prior to the parametric analysis, a literature study was performed that provided important background information about the subject. The input data was provided by Thomas Concrete Group and contained four different C35/45 concrete mixes. The four mixes had 0, 16, 32 and 50 % slag as part of the binder. This enabled analyzing the impact of slag content in the analysis. The model was validated to ensure reliability using the program Produktionsplanering Betong, a program developed for planning during construction of concrete structures. With the model verified and with material input data from Thomas Concrete Group, One-Factor-at-a-time (OFaT) analyses and Monte Carlo simulations were used to evaluate the influence and sensitivity of individual parameters on the development of temperature and stress in low-clinker concrete. The results showed the binder content and the heat of hydration to be the parameters with the most significant impact on thermal cracking, regardless of the slag content. Furthermore, the results showed greater sensitivity to large variations of the most significant parameters the more slag the mix contained. When comparing the results to the previously mentioned study, the parameters considered to have the most impact were nearly the same. One major difference was that the thermal expansion and contraction coefficient showed larger impact on thermal cracking for the mixes studied in this thesis, whereas it was not among the parameters with the most impact in the previous study