Long-term mechanical properties and durability of high-strength concrete containing high-volume local fly ash as a partial cement substitution

Abstract

High-volume fly ash (HVFA) is a commonly used partial substitution for cement in mortar and concrete production. The present study was developed to examine the potential of using local HVFA as a partial substitution for cement in high-strength concrete (HSC). The effects of FA inclusion on the long-term mechanical properties and durability of concrete were investigated. The HSC samples were prepared with different FA substitution ratios, ranging from 0% to 50% by weight (ratio between FA to total weight of cement and FA) at 10% interval. Long-term properties were evaluated through compressive strength (CS) and ultrasonic pulse velocity (UPV) tests, while durability was examined through water absorption (WA), drying shrinkage (DS), and rapid chloride ion penetration (RCPT) tests. The results indicate that, at 28 and 56 days, higher FA content was associated with lower HSC performance. However, at 120 days, the 30% FA sample achieved the highest performance of all of the samples in terms of long-term mechanical properties and durability. Moreover, higher FA content was associated with less DS. Also, no significant change in the water absorptivity value of the HSC samples was observed. All of the HSC samples at 28, 56, and 120 days of curing age had UPV values of above 4100 m/s, indicating “very good quality” concrete. In addition, all of the HSC samples exhibited “very low” chloride permeability. Finally, the results of the environmental analysis found that incorporating a high volume of locally sourced FA as a partial substitution for cement in HSC reduced both CO2 emissions (CO2-E) and energy consumption (EC), which may help further promote the sustainability of the construction industry.