Properties of concrete containing high volume fly ash

Abstract

The utilization of waste materials in concrete is one of the best value added solutions can be provided to the construction industry. To realize this aim, waste of coal combustion from power plant, known as fly ash is used. Although various researches conducted on the properties of fly ash concrete with fly ash, very little is known on high volume substitution of cement with Class F fly ash particularly for concrete with common water to cement ratio and strength in the concrete application in Malaysia. This research was dedicated to investigate various fresh and hardened state properties of concrete containing high volume fly ash (HVFA). In this investigation, the HVFA were tested in mortar and concrete, and both specimens were tested by substituting 40 to 60% of OPC with fly ash. Properties studied in this research includes fresh concrete properties, mechanical properties and durability properties of concrete exposed to chloride, acid and sulphate solutions. The test result indicates that HVFA positively influenced the workability; however the setting times of the concrete were retarded. The development of strength of HVFA concrete was relatively slower, but the strength development of HVFA concrete after 28 days was greater than concrete with OPC cement. In-terms of durability, the HVFA concrete demonstrated better resistance to destructive chemical penetration and attacks such as chloride, acid and sulphate. Additionally, the test results on the concrete temperature rise suggests that the replacement of cement with HVFA is advantageous, particularly for mass concrete where thermal cracking is of a major concern. However, the performance of concrete at elevated temperatures reveals that concrete without any fly ash has better resistance than HVFA concrete at high temperature. Conclusively, high volume fly ash integration as partial cement replacement increases the resistance of concrete towards chloride penetration, acid and sulphate attack and reduces the temperature rise while obtaining good strength and modulus properties.