Hydration Mechanism of Low Quality Fly Ash in Composite Cementitious Materials

【Author】

Shuhua Liu;Yaning Kong;Lu Wang;

【Abstract】

<正>The hydration mechanism of low quality fly ash in composite cementitious materials was investigated in this paper.To this aim,blended with limestone powder is a comparison reference to highlight the effect of low quality fly ash in blended cement.Through the analysis of paste compressive strength to analyse the influence of low quality fly ash on mechanics performance in cementitious material system;The effect on the properties of composite cementitious material hydration were measured by X-ray diffraction (XRD),thermal gravity analysis(TGA) and hydration heat determination;Using mercury injection test hole(MIP) and scanning electron microscopy(SEM) to reveal the influence of low quality fly ash on paste microstructure. The results showed grinding fine low quality fly ash represented the physical effect, namely filling effect,and in the late compared with limestone powder showed prominent pozzolanic activity.Grinding fine low quality fly ash and limestone powder contributed to the early formation AFt converting to AFm and AFmc.Although grinding firm low quality fly ash delayed the induction period,but shortened the accelerator period,and not delayed the second exothermic peak Cementitious material blended with limestone powder generated a large number of gel around the particles of limestone powder with compact structure,lending to weak hydration and low combined water gel.But in 7d, grinding fine low quality fly ash showed pozzolanic activity,generated high combined water gel,late sharply lowered more than 50nm pore,made the pore structure more uniform density.

【Keywords】

low quality fly ash;;hydration mechanism;;hydration products;;pore structure;;limestone power

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