MS thesis from Jeff LaHucik, Civil Engineering, University of Illinois at Urbana-Champaign, 2016
Advisor Professor Jeff Roesler, University of Illinois at Urbana-Champaign, and ISCP President
Selecting Material Constituents & Proportions for
Specific Roller-Compacted Concrete Mechanical Properties
Roller-compacted concrete (RCC) is increasingly becoming an alternative pavement type because of its construction expediency, reductions in material and construction costs, sustainability benefits, and overall structural capacity. Current RCC pavement mix design procedures select mix constituents and proportions based on strength requirements, workability, and field density. Discrepancies in mechanical properties are known to exist between field and laboratory compacted specimens. In order to move toward designing and constructing performance-based RCC mixtures, the effects of various mixture constituents, proportions, and compaction methods must be quantified and the gap between laboratory and field properties must be minimized.
A wide range of RCC aggregate gradations were batched, tested, and found to impact RCC properties especially compressive strength. The coarse-fine aggregate ratio was the parameter linked most directly to RCC compressive strength. Aggregate type (recycled aggregates, siliceous rounded sand and gravel, manufacture sand, and crushed aggregates) was also shown to affect aggregate packing density and RCC properties. Fly ash or ground granulated blast furnace slag replacement of cement statistically reduced the early-age RCC strength and likely would delay opening the RCC pavement to traffic. In general, fracture properties of RCC with virgin and recycled aggregates were similar or greater than fracture properties of conventional concrete pavements (PCC) which suggests similar or greater slab capacities and fatigue lives for RCC relative to PCC for the same slab thickness. Several types of macro-fibers embedded in RCC were shown to statistically improve the RCC compressive strength as well as provide residual strength comparable to conventional fiber reinforced concrete.
Past researchers have demonstrated that the gyratory compactor has the potential to be an alternative RCC mix design tool to the modified Proctor procedure. The gyratory compactor provides similar compaction mechanisms and energies relative to construction of RCC (and asphalt) pavements as well as significantly reducing operator error in specimen preparation. The gyratory compactor was employed in this research to evaluate several laboratory mixture proportions and constituents focusing on aggregate gradations and cementitious content as well as comparing companion gyratory results to already constructed RCC pavements. The gyratory compactor was verified to be more sensitive to changes in aggregate gradation and cementitious content compared to the modified Proctor and vibratory hammer, which are commonly used methods for RCC mix design and specimen fabrication, respectively.