Performance of high-volume fly ash concrete pavements constructed since 1984

摘要

This investigation was performed to evaluate the long-term performance of concrete pavements made with high volumes of Class F and Class C fly ash. Additional recent field performance investigations (2002) are reported in this paper since the prior publication in the ACI. Six different mixtures, consisting of three mixtures with Class C fly ash having up to 70 percent cement replacement and three mixtures with Class F fly ash having up to 67 percent cement replacement, were used. Two series of tests were conducted to establish the long-term per for mance for all mixtures using core specimens from in-situ pavements. Long-term tests were conducted for compressive strength, resistance to chloride-ion penetration, and density. Test results revealed that both Class C and Class F fly ash contributed to high long-term compressive strength. Generally, the concrete mixtures containing Class F fly ash exhibited higher resistance to chloride ion penetration relative to mixtures containing Class Cfly ash. Long-term compressive strengths of core specimens taken from in-situ pavements ranged from approximately 45 to 59 MPa. The highest long-term compressive strength was achieved by concrete mixtures incorporating 19 percent Class Cfly ash at the age of 12 years (59 MPa) and 67 percent Class F fly ash at the age of 7 years (57 MPa). Visual observations revealed that the concrete pavement sections containing high-volumes of Class F fly ash (35 to 67 percent) performed well in the field with only minor surface scaling. Concrete pavement sections containing up to 70 percent Class C fly ash have experienced some surface damage due to abrasion and scaling, especially in an area where truck traffic makes a 90-degree turn.