Influence of high calcium fly ash on permeability of concrete in respect to aggressive media
Journal Title: Roads and Bridges - Drogi i Mosty - Year 2011, Vol 10, Issue 3
Abstract
The subject of the investigation was evaluation of the permeability of concrete made with high calcium fly ash (HCFA) from brown coal combustion. Raw (unprocessed) and additionally grinded HCFA was tested. The influence of HCFA type and content on the concrete resistance against penetration of aggressive fluids and gases was studied. HCFA was used for partial replacement of cement in concrete mix assuming the efficiency factor [i]k[/i]=0.4. The chloride migration coefficient in non-steady diffusion state, the water- and air-permeability as well as the compressive strength of concrete were measured. The evaluation of microstructure of concrete was performed using SEM and optical microscopy in transmitted light on thin sections. It was been found that partial replacement of Portland cement by HCFA (15% or 30%) with water to binder ratio w/b=0.55 increased the resistance of concrete against water and air ingress. The grinding process of HCFA improved the air-impermeability of concrete. For w/b=0.45 the influence of HCFA on the water permeability of concrete was unnoticeable. A significant influence of partial replacement of cement by HCFA on the chloride resistance of concrete was found. The lowest value of the coefficient of chloride migration was obtained for concrete made with HCFA, for higher values of w/b the penetration of the chloride ions increased. Image analysis performed on thin sections revealed an increased content of unburned carbon particles in the matrix for higher HCFA content in concrete. The size of unburned particles was inversely related to the grinding time of HCFA and this could influence the permeability of concrete.
Authors and Affiliations
Daria Jóźwiak-Niedźwiedzka, Karolina Gibas, Michał Glinicki, Grzegorz Nowowiejski
Keywords
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