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Using recycled concrete as coarse aggregate in pavement concrete.

机译：在路面混凝土中使用再生混凝土作为粗骨料。

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摘要

The main objective of this study was to evaluate the effects of using aggregate produced from recycled concrete as a replacement for natural (virgin) coarse aggregate in pavement mixtures. All mixtures containing the recycled concrete aggregate (RCA) were designed to meet the requirements of Indiana Department of Transportation (INDOT) specifications. The scope of the study included evaluation and comparison of several properties of RCA and natural aggregates, evaluation and analysis of the effects of RCA on concrete properties, and modification of aggregate gradations and mixture composition in an attempt to improve the properties of RCA concrete.;A total of ten different concrete mixture types were produced in the course of this study. These included three different RCA replacement levels (30%, 50% and 100% by weight of the natural coarse aggregate) and two different cementitious systems (plain system -- Type I portland cement only and fly ash system -- 80% of Type I portland cement and 20% of ASTM C 618 Class C fly ash). All ten mixtures were first produced in the laboratory (trial batches) and subsequently reproduced in the commercial ready mixed concrete plant. Each mixture produced in the ready mixed plant was used to prepare several types of specimens for laboratory testing. The tests performed on fresh concrete included determination of slump and entrained air content. The mechanical properties of the hardened concrete were assessed by conducting compressive strength, flexural strength, modulus of elasticity and Poisson's ratio tests. The durability of concrete was assessed using wide array of measurements, including: rapid chloride permeability (RCP), rapid chloride migration (RCM), electrical impedance spectroscopy (EIS), surface resistivity, free shrinkage, water absorption test, freeze-thaw resistance and scaling resistance.;The test results indicated that the properties of plain (no fly ash) concrete mixtures with 30% RCA as coarse aggregate were very comparable (in some cases even better) than those of the control concrete (0% RCA). Although mixtures with 50% RCA showed up to 36% reduction in durability and mechanical properties, the test results still met INDOT's specifications requirements. However, the mechanical properties of plain concretes made with 100% RCA were measurably lower (16%-25%) than those of the control concrete. It should be pointed out, however, that these properties were still above the minimum required by INDOT's specification, the only exception being the w/c value that needed to be elevated to 0.47 from the maximum recommended of 0.45.;The use of fly ash improved the quality of RCA concrete, especially at later ages. In particular, the properties of concrete with 50% of RCA were similar to the properties of control concrete. Similarly, the properties of mixture with 100% RCA improved when compared to the same mixture without fly ash and the concrete met minimum requirements imposed by INDOT's specifications. However, when compared to the fly ash concrete with 100% virgin aggregate the mechanical properties of the 100% RCA concrete were up to 19% lower.;The results of all tests performed during this study were used to develop several statistical models which can be used to predict selected properties of the RCA concrete, thus reducing the number of laboratory test required to be performed on the actual mixtures. The developed models can be used to predict the following properties: slump, 7-day flexural strength and 56-day bulk resistance. These models were successfully verified using results from several independent (not used in the original model development) mixtures.;Once the testing of the original ten types of concrete mixtures was completed, six additional concrete mixtures were produced, each with modified (with respect to original mixtures) gradation of aggregate. These mixtures were used to study if the virgin and RCA aggregates can be combined in different proportions to produce the "optimized blend" which will improve one (or more) concrete characteristics. The test results obtained from the six additional mixtures indicated that modifying the aggregate gradation did not have beneficial effects with respect to either compressive or flexural strength values.;Considering limited scope of this study (only one source of RCA aggregate was used) it is recommended that the amount of RCA in plain concrete be limited to 30% and that in the fly ash concrete be limited to 50% to ensure the adequate quality of the pavement concrete.
机译：这项研究的主要目的是评估使用再生混凝土生产的骨料替代路面混合物中天然（原始）粗骨料的效果。所有包含再生混凝土骨料（RCA）的混合物的设计均符合印第安纳州运输部（INDOT）规范的要求。研究的范围包括：评估和比较RCA和天然骨料的几种性能，评估和分析RCA对混凝土性能的影响，以及改变骨料的级配和混合物组成，以改善RCA混凝土的性能。在此研究过程中，总共生产了十种不同的混凝土混合物类型。其中包括三种不同的RCA替代水平（分别为天然粗骨料的30％，50％和100％）和两种不同的胶凝体系（普通体系-仅I型硅酸盐水泥和粉煤灰体系-I型的80％硅酸盐水泥和20％的ASTM C 618 C类粉煤灰。所有十种混合物首先在实验室中生产（试验批次），然后在商业化的预拌混凝土工厂中生产。准备好的混合工厂中生产的每种混合物均用于制备几种类型的标本，用于实验室测试。在新鲜混凝土上进行的测试包括坍落度和夹带空气含量的测定。通过进行抗压强度，抗弯强度，弹性模量和泊松比测试来评估硬化混凝土的机械性能。使用多种测量方法评估混凝土的耐久性，包括：快速氯离子渗透率（RCP），快速氯离子迁移（RCM），电阻抗光谱（EIS），表面电阻率，自由收缩率，吸水率测试，耐冻融性和试验结果表明，含30％RCA的粗骨料的普通（无粉煤灰）混凝土混合物的性能与对照混凝土（0％RCA）非常相似（在某些情况下甚至更好）。尽管含50％RCA的混合物的耐久性和机械性能降低了36％，但测试结果仍符合INDOT的规格要求。但是，用100％RCA制成的普通混凝土的机械性能明显低于对照混凝土（16％-25％）。但是，应该指出的是，这些性能仍高于INDOT规范要求的最小值，唯一的例外是w / c值需要从建议的最大值0.45提高到0.47。改善了RCA混凝土的质量，尤其是在后期使用时。特别是，RCA为50％的混凝土的性能与对照混凝土的性能相似。同样，与不含粉煤灰的相同混合物相比，含100％RCA的混合物的性能得到了改善，混凝土满足了INDOT规范的最低要求。但是，与具有100％原始骨料的粉煤灰混凝土相比，100％RCA混凝土的机械性能降低了19％。；在此研究过程中进行的所有测试结果被用于开发几个统计模型，这些模型可以用于预测RCA混凝土的选定性能，从而减少了对实际混合物进行实验室测试所需的次数。所开发的模型可用于预测以下特性：坍落度，7天抗弯强度和56天抗松强度。这些模型已使用几种独立的混合物（未在原始模型开发中使用）的结果成功验证。;一旦完成对原始十种类型混凝土混合物的测试，便会生产出六种其他混凝土混合物，每种混合物均经过了改良（相对于原始混合物）骨料的级配。这些混合物用于研究原始料和RCA骨料是否可以不同比例混合以产生“优化的混合物”，从而改善一种（或多种）混凝土的特性。从另外六种混合物中获得的测试结果表明，改变骨料的等级对抗压强度或抗弯强度值均无益处。;考虑到本研究的范围有限（仅使用一种RCA骨料）将普通混凝土的RCA含量限制为30％，粉煤灰混凝土的RCA含量限制为50％，以确保路面混凝土的质量。

著录项

  • 作者

    Verian, Kho Pin.;

  • 作者单位

    Purdue University.;

  • 授予单位 Purdue University.;
  • 学科 Engineering Civil.
  • 学位 M.S.C.E.
  • 年度 2012
  • 页码 217 p.
  • 总页数 217
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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