The Missouri Department of Transportation (MoDOT), USA, has released a report that evaluates the feasibility of using high-volume recycled materials for concrete production in rigid pavement. The research investigates whether 50 percent of the solids may be replaced with recycled materials and industrial by-products.
The goal was to replace 50% of the solids with recycled materials and industrial by-products. The performance of concrete mixtures made with different fine and coarse recycled concrete aggregate (RCA) contents and binder types was investigated. Both single-layer rigid pavement and two-lift concrete pavement (2LCP) were considered. The optimized mixtures developed 91-d compressive strength results from 5,900 to 8,600 psi. Flexural strength was mostly higher than 600 psi at 28 d. The modulus of elasticity ranged from 4.7 to 6.7 ksi at 56 d. Using the optimized binder incorporating 35% Class C fly ash and 15% slag reduced the 150-d drying shrinkage to values less than 350 to 500 με. However, an increase in fine RCA content from 15% to 40% resulted in increased shrinkage values (up to 650 με). The optimized mixtures exhibited frost durability factor higher than 88%. De-icing salt scaling ratings were limited to 3 for all mixtures, except the mixture with 15% GP and 35% FA-C. All mixtures exhibited comparable coefficient of thermal expansion (CTE) values, ranging from 4.8 to 5.2 E-6 in/in/°F. Incorporation of RCA did not have a significant effect on CTE values.
Based on the obtained data, it was concluded that concrete mixtures incorporating high- volume recycled aggregate and SCMs can present viable choices for sustainable pavement construction. The following four mixtures exhibited satisfactory performance and can be used for construction of the single layer pavement:
- MoDOT PCCP as the reference concrete
- Concrete incorporating the optimized binder (15% slag and 35% Class C fly ash replacements), 0.40 w/cm, without any RCA
- Concrete incorporating the optimized binder, 0.40 w/cm, and 30% coarse RCA (30C)
- Concrete incorporating the optimized binder, 0.37 w/cm, and 50% coarse RCA (50C-37).
The following three mixtures can be incorporated for construction of the top layer of the 2LCP systems:
- MoDOT PCCP as reference
- Concrete incorporating the optimized binder, 0.40 w/cm, without any RCA
- Concrete incorporating the optimized binder, 0.40 w/cm, and 30% coarse RCA (30C).
The following two mixtures can be employed for construction of the bottom layer of the 2LCP systems:
- Concrete incorporating the optimized binder, 0.37 w/cm, 50% coarse RCA, and 15% fine RCA (50C15F-37)
- Concrete incorporating the optimized binder, 0.37 w/cm, and 70% coarse RCA (70C-37).
To view and download the PDF of this report, please go to: https://library.modot.mo.gov/RDT/reports/TR201502/cmr17-006.pdf
Also available through TRB: http://www.trb.org/main/blurbs/176123.aspx