| Abstrakt: |
Pervious concrete is considered an advanced pavement material in terms of environmental benefits resulting from its basic feature - high water permeability. While natural aggregate is a standard component for permeable concrete production, the paper presents the potential of air-cooled blast furnace slag aggregate. The aggregate is specific for its open internal structure and at the same time high hardness and strength, which was assumed to be advantageous for this type of concrete. As permeable concrete is characterized by a specific structure and low amount of binder, it needs for optimization of kind and composition of aggregate, as well as the quantity and quality of the binder. In the experiment, following variables of composition were applied: a ratio of binder to aggregate b/a (0.28 and 0.36), a ratio of fine to coarse aggregate f/c (0.1, 0.2 and 0.3), and a set of blended cements. Experimental results point to the specific benefit of slag aggregate for permeable concrete production. The values of total porosity (30-38%) and permeability (4.6-17.5 mm/s) are higher than those recommended by most publications, as well as than those of concretes with natural aggregates. The compressive strength runs from 7.5 MPa to 15.0 MPa depending on the variables, while the effect of fine aggregate portion on both compressive strength and hydraulic conductivity is found to be much greater than that of the amount of binder. An important aspect is that, due to the nature of the aggregate, sufficient permeability is maintained even with higher proportion of fines. The range and variance values of the individual properties indicate that a change in the quality of the binder causes less variation in the results than a change in the composition of the mixtures. |
