Flexural Capacity of Rigid Pavement Concrete Slabs with Recycled Aggregates

Few studies have focused on the effect of recycled materials on the concrete slab load capacity. This study used virgin and recycled aggregates—fractionated reclaimed asphalt pavement (FRAP) and recycled concrete aggregate (RCA)—and by-product cementitious materials—ground granulated blast furnace slag and fly ash—to cast and test the load capacity of single- and two-lift concrete slabs. Five concrete mixtures were examined, which were virgin aggregate (the control) and four different replacements of coarse aggregate: 45% FRAP, 45% FRAP with macrofibers, 100% RCA, and a blend of 45% FRAP and 55% RCA. For all laboratory specimens tested, the virgin aggregate concrete had the highest strength (compression, split tension, and flexural) and modulus of elasticity, and the mix with 45% FRAP and fibers resulted in the lowest properties, which was attributed to the relatively high air content of the fresh concrete. With the exception of the mix with 45% FRAP and fibers, the critical stress intensity factor and initial and total fracture energies of the recycled aggregate concretes were not statistically different than the virgin aggregate concrete using the single edge notched beam specimen. For the 16 large-scale concrete slabs (6 ft x 6 ft x 6 in. thick) cast using both single and two-lift designs, the results indicated that the concrete slab load-carrying capacity is significantly underpredicted by the beam flexural strength measurements, and that concrete with recycled aggregates had similar flexural load capacity to the virgin concrete slabs. Using 2D finite element analysis, the ratio between slab flexural capacity and beam strength was found to be significantly higher for the recycled aggregate concrete relative to the virgin aggregate concrete. The concrete slab flexural load capacity was governed more by the concrete fracture properties and slab geometry then by conventional strength criteria. Two additional topics presented in the appendices are a literature review and evaluation of recycled washout water (grey water) from concrete batch plants as mixing water in fresh concrete. Based on the literature, grey water should be suitable for use in fresh concrete, provided that the solids content is not excessive and ASTM C1602 guidelines are followed. A laboratory study evaluating the use of recycled tire cord steel as fiber reinforcement in concrete revealed that the fibers could be beneficial for improving the concrete toughness, but a cost-benefit analysis is required.

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    University of Illinois, Urbana-Champaign

    Department of Civil and Environmental Engineering
    205 North Mathews Avenue
    Urbana, IL  United States  61801-2352

    University of Illinois, Urbana-Champaign

    Illinois Center for Transportation
    1611 Titan Drive
    Rantoul, IL  United States  61866

    Illinois State Toll Highway Authority

    2700 Ogden Avenue
    Downers Grove, IL  United States  60515-1703
  • Authors:
    • Brand, Alexander S
    • Amirkhanian, Armen N
    • Roesler, Jeffery R
  • Publication Date: 2013-5


  • English

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  • Accession Number: 01485061
  • Record Type: Publication
  • Report/Paper Numbers: ICT-13-018, UILU-ENG-2013-2014
  • Files: TRIS
  • Created Date: Jun 27 2013 9:15AM