Statistical Modeling of Cement Heat of Hydration Using Phase and Fineness Variables (2010) / Chapter Skim
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1 CHAPTER 1- INTRODUCTION AND RESEARCH APPROACH 1.1 Background Hydraulic cements react with water through a process called hydration via a series of chemical reactions, ultimately resulting in the precipitation of interlocking hydration products that provide strength to the structure. The hydration process produces heat that in some concrete placements may cause expansion and, potentially, cracking upon cooling to ambient conditions.
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2 the heat of hydration. Type II cement with the moderate heat option has restrictions on either the sum of C3S+4.75*
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3 349.3 342.5 263.2 370.3 232.9 310.5 200 220 240 260 280 300 320 340 360 380 400 1 Cement Type Type I Type II Type II MH Type III Type IV Type V Figure 1-2- The dependence of heat of hydration, with +- 1s uncertainties indicated, on cement Type for a limited sampling of cements produced between 1992 and 1997 [1] As the specifications recognize the influences of cement phase composition on heat of hydration, a more accurate and more complete characterization of a cement's mineralogical and textural characteristics should provide an improved data set to evaluate their influences.
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4 cubic form)
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5 Figure 1-3- SEM backscattered electron micrograph of polished cement grains embedded in an epoxy illustrates the complicated shapes and multiphase particles typical of a portland cement. Phase code is: alite = A, belite = B, aluminate = Al, ferrite = F, alkali sulfate = Alk, and gypsum = G
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6 Table 1-1- Heat of hydration values for clinker phases, and coefficients at 7 d and 28 d. From Taylor [3]
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7 1.4 Problem Statement The heat of hydration of hydraulic cements results from the complex sets of phase dissolution and precipitation activity accompanying cement hydration. This process generates heat, as well as an increased potential for thermal cracking in some concrete structures.
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