【摘 要】
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The rheological behavior of fresh Portland cement (PC) pastes with different chemical and potential mineralogical compositions was analyzed alone and when blended with siliceous mineral additions: sil
【机 构】
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Department of Civil Engineering, Engineering Faculty UNCPBA, Olavarría B7400JWI, Argentine
【出 处】
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The 14th International Congress on the Chemistry of Cement (
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The rheological behavior of fresh Portland cement (PC) pastes with different chemical and potential mineralogical compositions was analyzed alone and when blended with siliceous mineral additions: silica fume,diatomite and quartz, which had a SiO2 content of over 90%.The replacement ratios used were 20 and 40% for mineral additions quartz and diatomite, and 5 and 15% for silica fume, all by Portland cement weight.Trials were conducted during latent hydration at 25 ℃ and were designed to find the most significant thixotropical behavior of all fresh cement pastes.The findings showed that the shear stress in every fresh paste was observed to rise with C3S (%) content of the PC and hence with a decrease in its Na2Oeq.(%) content, which actually proved to be the key determinant for apparent viscosity of both fresh PC pastes.Further, then, to the potential mineralogical composition of the two Portland cements and therefore to the nature and development of the hydration products formed, the PC with higher C3A (%) content, i.e., the one with the higher Na2Oeq.(%) content, performed best in the rheological study, as logical.The siliceous mineral additions were likewise observed to affect fresh paste rheology with both types of PC, depending, firstly, on whether or not they were pozzolanic, and secondly, on their morphology and particle size and the type of PC.Thus, they were observed to stimulate Portland cement hydration differently: directly and non-directly or, if they were very pozzolanic,indirectly above all.In addition, depending of the mineral addition deemed, dilution also had a direct and inevitable effect on the rheological properties of their fresh pastes.
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