Abstract
In the paper a low-temperature thermoporometry using differential scanning calorimetry (DSC) was employed for analyse of influence of siliceous fly ash (FA) on pore structure of non-air-entrained mortars (pore size, connectivity). A method of interpreting a heat flux differential scanning calorimetry records in pore structure was used for this purpose. The results demonstrated that the: (i) fly ash mortars have virtually no pores inaccessible to water, unlike the mortars with plain Portland cement in which inaccessible pores constitute a significant fraction, growing with the increase in w/b; (ii) with a decrease in w/b the ink-bottle volume decreases. Fraction of this pore type is relatively larger in fly ash mortars; (iii) Siliceous fly ash increased the volume of pores greater than 8 nm, in particular in the group with radii larger than 20 nm at all w/b ratios.
Highlights
Practical experience and scientific research over the last half-century have provided a wealth of information on the qualitative differentiation of siliceous fly ashes (FA) and their potential for use in concrete technology
This paper reports the influence of siliceous fly ash and w/b ratio on the pore structure in non-air-entrained cement mortars made with CEM I 32,5 and CEM II/B-V 32,5
95% to 100%, while in the mortars with plain Portland cement, it was 77% to 83% - in both cases these values decreased with an w/b increase
Summary
Practical experience and scientific research over the last half-century have provided a wealth of information on the qualitative differentiation of siliceous fly ashes (FA) and their potential for use in concrete technology. Fly ash with finer particles (below 10 μm), less unburnt carbon (coal) and more vitreous phases of increased reactivity improve the properties of blended cements [1]. Experience shows that the frost resistant cement matrix with siliceous fly ash can be obtained with adequately low w/b [2, 3]. In comparison to material containing ordinary Portland cement, fly ash increase the total porosity of hardened cement matrix [4, 5]. It was found that the addition of fly ash in blended cement after a long curing time reduces the cross-section of capillary pores relative to ordinary Portland cement materials [6, 7, 8, 9, 10, 11]. DSC thermoporometry does not have the disadvantages of the MIP method for example allows
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