Issue 46

Y. Yanya, Frattura ed Integrità Strutturale, 46 (2018) 343-351; DOI: 10.3221/IGF-ESIS.46.31 347 findings were consistent with the research results of Bhutta MAR et al. [18]. Tab. 3 also demonstrated that the apparent density and stacking density of the recycled aggregate was lower than those of the natural aggregate. The study of Xu et al. [19] suggested that the apparent density and stacking density of the recycled aggregate were between 2310 kg/m 3 and 2620 kg/m 3 and between 1200 kg/m 3 and 1470 kg/m 3 ; and the apparent and stacking density of the recycled aggregate in this study were both within the ranges. Moreover the crushing value of the recycled aggregate was apparently larger than that of the natural aggregate, about 2 times, and the silt content of the natural aggregate was 6 times that of the recycled aggregate. The analysis results of porosity and permeability coefficient A previous study [20] found that the porosity of recycled pervious concrete increased with the increase of replacement rate. The relationship between replacement rate and porosity obtained in this study was in line with that rule. The porosity and permeability coefficient of the recycled pervious concrete are shown in Tab. 4. Moreover it was found that the connected porosity increased with the increase of permeability coefficient (Fig. 2), which was similar to the research results of Zaetang et al. [13]. It was because that concrete with higher porosity had suffered smaller water resistance due to the larger effective wetted area. No. Range of porosity/% Average porosity/% Average permeability coefficient (cm/s) RC0 17.02~19.18 17.8 0.28 RC30 14.56~15.68 14.96 0.26 RC50 14.94~18.55 16.18 0.27 RC100 18.75~22.2 20.43 0.47 RC100D 13.77~14.95 14.20 0.18 Table 4: Porosity and permeability coefficient. 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 14 16 18 20 22 24 26 28 Porosity /% ) ( 149 .0 021 .0 V e W  917 .0 2  R Figure 2 : Porosity and permeability coefficient The analysis of compressive and splitting tensile strength Strength is an important parameter of pervious concrete. The application of recycled aggregate can provide enough strength for pervious concrete. The compressive strength of the recycled pervious concrete was between 3.6 MPa and 9.07 MPa in this study. The variation rule of the compressive strength under different replacement rate is shown in Fig. 3 and 4. It could be noted from Fig. 3 and 4 that the compressive strength of RC30, RC50, RC100 and RC100D were higher than RC0, which was consistent with the current research results [21,22]. It was because that the rough surface and porous internal structure of the recycled aggregate strengthened cementation, and the water absorbed by the aggregate during mixing released to promote the development of the compressive strength. Moreover it was observed that the compressive strength gradually improved with the increase of the replacement rate; the improvement amplitude was the largest when the replacement rate was 30%, but kept unchanged when the replacement rate was higher than 30%. The compressive