【摘 要】
：
Ordinary portland cement (OPC) is prone to react with water, even upon premature contact as may occur during storage or handling.Such contact with water, in the liquid or vapor states, results in chem
【机 构】
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Department of Civil and Environmental Engineering, University of California Los Angeles, 90095, Unit
【出 处】
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The 14th International Congress on the Chemistry of Cement (
论文部分内容阅读
Ordinary portland cement (OPC) is prone to react with water, even upon premature contact as may occur during storage or handling.Such contact with water, in the liquid or vapor states, results in chemical reactions.Such early reaction, termed as pre-hydration, is known to reduce cement reactivity and ultimately mechanical property development during its end use.In spite of its obvious impacts, prehydration and its effects have not been rigorously quantified.This study studies the impacts of prehydration on cement powders which were intentionally exposed to either water vapor or liquid water, to investigate the extents to which such premature contact can induce changes in surfaces, and reaction and mechanical property behaviors ofprehydrated systems.Results obtained using isothermal calorimetry, thermogravimetric analysis, and compressive strength measurements are correlated to a pre-hydration index, i.e., a measure of the extent of pre-hydration which is established for the first time.Boundary nucleation and growth (BNG) simulations and kinetic cellular automaton (KCA) simulations are used to evaluate hypotheses of mechanisms which affect pre-hydration.It is noted that systems exposed to water vapor, versus liquid water show dramatically different influences of prehydration, due to the formation of different types, and extents of surface coverage produced on the cement grains in each case.Reductions in mechanical properties noted in prehydrated systems are linearly correlated with the prehydration index.This provides for a method for screening cements known to have been prehydrated, to determine whether the associated effects can be mitigated.Significantly, the catalytic properties of fine limestone are highlighted as being valuable to offset the effect ofprehydration, with increasing success at low(er) levels ofprehydration.
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