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The effect of superplasticisers on OPC and PPFA concrete

Moffat I., Klemm A. J.

Budownictwo o Zoptymalizowanym Potencjale Energetycznym

2007

nr (4)

219--225

Although the use of superplasticisers within cement is well established, there is still lack of consensus on their effect on the hydration process. The problem complicates even further, when superplastizisers are incorporated into the concrete mix containing Pfa as partial replacement. The aim of the paper therefore was twofold: firstly to assess the effect of partial replacement of OPC by PFa and secondly, to explore the effect of increased lever of superplasticizing admixture and reduced cement content on the PPFA. Comparative studies have demonstrated that improved long-term performance to that of OPC concrete is achievable with the addition of pulverized fuel ash (PPFA). Early strength of the PPFAC concrete is however compromised with parity being obtained after 80 days. Increased level of cement and PFA content does not always provide satisfactory results in terms of the 28 days compressive strength. Increased amount of fines and water content may lead to heaping up of the cement particles and altering workability. Introduction of a superplasticiser reduces water demand without the need to change the cement content. It is possible therefore to produce a concrete of 40 N/mm² strength and reduced level of water absorption.