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Variability of Fresh and Hardened Voids of Pervious Concrete

机译：渗透混凝土的新鲜和硬化空隙的变异性

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ASTM C1688-08 currently contains only a single-operator standard deviation for the density criterion for determining allowable range. The adequacy of this criterion was put to the test in recent research undertaken for the Tennessee Concrete Association (TCA). Twenty replications of three pervious mixtures were used. The control mixture had 356-kg/m~3 (600-lb/yd~3) of cementing materials with a 0.3 w/cm ratio, 1533-kg/m~3 (2584-lb/yd~3) of No. 89 limestone coarse aggregate and no fine aggregate. The second mixture had 3.5 % river sand replacement of the coarse aggregate (by total aggregate volume) and a 0.31 w/cm ratio. The third mixture had 7 % river sand in the combined aggregate gradation and a w/cm ratio of 0.32. Coarse aggregate content was reduced to accommodate the changes in the second and third mixtures. Twenty replications of each TCA mixture yielded coefficients of variation of ASTM C1688 density values of 0.3, 0.5, and 0.7 %, respectively for the control mixture, the 3.5 % sand mixture, and the 7 % sand mixture. All three mixtures met current allowable ASTM C1688 range criteria based on ASTM C670-03 multipliers. However, the variability in density increased substantially as sand and w/cm ratios were increased, possibly indicating that the variability criterion for density may need to be revised. Other findings include a good correlation between C1688 voids and pervious properties such as effective (water accessible) voids (ASTM D7063-05) and compressive strength (ASTM C39-06) indicating that C1688 voids may be useful as a mix design and adjustment tool. Twenty replications of each TCA mixture yielded coefficients of variation of ASTM C1688 void values of 1.1, 2.5, and 3.6 %, respectively, for the control mixture, 3.5 % sand mixture, and 7 % sand mixture. Information on compressive strength and effective void variability is also provided.
机译：ASTM C1688-08当前仅包含用于确定允许范围的密度标准的单操作者标准偏差。田纳西州混凝土协会（TCA）最近进行的研究对该标准的适用性进行了测试。使用了三个透水混合物的二十次重复。对照混合物具有356-kg / m〜3（600-lb / yd〜3）的胶结材料，比例为0.3 w / cm，1533-kg / m〜3（2584-lb / yd〜3）的No. 89石灰石粗骨料，无细骨料。第二混合物具有3.5％的河砂替代粗骨料（按总骨料体积计）和0.31w / cm的比率。第三混合物在合并的骨料中具有7％的河沙，w / cm比为0.32。降低粗骨料含量以适应第二种和第三种混合物的变化。对于对照混合物，3.5％的沙子混合物和7％的沙子混合物，每种TCA混合物进行20次重复复制后，ASTM C1688密度值的变异系数分别为0.3％，0.5％和0.7％。这三种混合物均符合基于ASTM C670-03乘数的当前允许的ASTM C1688范围标准。但是，随着沙和w / cm比的增加，密度的变异性也显着增加，这可能表明可能需要修改密度的变异性标准。其他发现包括C1688空隙与透水性之间的良好相关性，例如有效（水可及）空隙（ASTM D7063-05）和抗压强度（ASTM C39-06），表明C1688空隙可用作混合物设计和调节工具。对于对照混合物，3.5％的沙子混合物和7％的沙子混合物，每种TCA混合物进行20次重复试验，得出ASTM C1688空隙值的变异系数分别为1.1％，2.5％和3.6％。还提供了有关抗压强度和有效空隙变化的信息。

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