United States Department of Transportation
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Abstract:Following specification harmonization for portland cements, FDOT engineers reported signs of
deterioration in concrete elements due to temperature rise effects. One of the main factors that affect
concrete temperature rise potential is the heat generated by portland cement during hydration. This study
was initiated to identify the effect of cement fineness on the heat generated by portland cement. Eleven
cements were selected for this study to address the effects of cement fineness and mineralogy. Several
of the cements came from the same source but had different grinds. This was important in studying the
fineness contribution to heat of hydration while maintaining similar cement mineralogy. The as-received
cements from different suppliers had a wide range of mineralogical compositions which allowed the
study of the effects of mineralogy on the heat of hydration. Cements were characterized through oxide
chemical analysis, x-ray diffraction, Blaine fineness, laser particle size analysis, setting behavior, and
strength measurements. Additionally, limited restrained shrinkage experiments were performed on two
of the cements from the same source to determine the effect of cement fineness on restrained shrinkage.
The findings indicate that cement fineness is better correlated to 7-day heat of hydration than the heat
index expressed as C3S + 4.75 C3A. Additionally, the results indicate that a finer cement experiences
higher shrinkage than a coarser cement. Comparison of activation energies indicates that cements with
higher fineness have lower activation energy. For Type II moderate heat (MH) portland cements that
will be used in structural concrete elements where there is a risk of cracking due to thermal stresses, it
is recommended that limits be placed on the heat of hydration, the Blaine fineness, and the heat index.
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