Content area
Full text
This paper reports on the development of high-performance fiber-reinforced cementitious composites (HPFRCC), taking into account environmental sustainability considerations. Engineered cementitious composites (ECC), a unique member of HPFRCC featuring high tensile ductility with ultra-high volumes of fly ash (HVFA) replacement (up to 85% by weight) of cement, are proposed in this paper. While micromechanics is applied in many aspects of the material design process, emphasis of this study is placed on the effect of fly ash content on altering material microstructure and mechanical properties. Experimental results show that HVFA ECCs, while incorporating high volumes of recycled fly ash, can retain a long-term tensile ductility of approximately 2 to 3%. Significantly, both the crack width and free drying shrinkage are reduced with an increase of the fly ash amount, which may benefit the long-term durability of HVFA ECC structures. Micromechanics analysis indicates that the increase of fiber/matrix interface frictional bond in HVFA ECCs is responsible for the tight crack width. In addition, HVFA ECCs show a robustness improvement by achieving more saturated multiple cracking while reducing environmental impact through the use of industrial waste stream material instead of cement.
Keywords: engineered cementitious composites; high-volume fly ash; sustainability.
(ProQuest: ... denotes formulae omitted.)
INTRODUCTION
Concrete is the most popular construction material, with more than 11.4 billion tons (10.3 billion tonnes) of concrete consumed annually worldwide.1 It has been reported that 2.2 billion tons (2.0 billion tonnes) of cement was produced in the year 2005.2 The requirement of cement increases with time and it was estimated that each ton of cement produced generates an equal amount of carbon dioxide.3 The production of cement is responsible for 5% of global greenhouse gas emission created by human activities.4 Therefore, incorporating sustainability concerns into the design of civil engineering materials is urgently needed.
High-performance fiber-reinforced cementitious composites (HPFRCC) can significantly contribute to enhancing the service life of civil infrastructure. Among them, engineered cementitious composites (ECC) is a noticeable representative with unique tensile properties. Unlike conventional tension softening concrete and fiber-reinforced concrete (FRC), ECC exhibits metal-like tensile strain-hardening behavior after matrix first cracking. Figure 1 shows the typical tensile stress-strain curve of ECC. The tensile ductility of ECC is several hundred times that of normal concrete and the fracture toughness of ECC...