Engineered cementitious composites with low volume of cementitious materials

Engineered cementitious composite (ECC) is an ultra ductile cement-based material reinforced with fibers. It is characterized by high tensile ductility and tight crack width control. Thanks to the excellent performance, ECC is emerging in broad applications to enhance the loading capacity and the durability of structures. However, ECC also faces a limitation on dimensional stability and on economical and sustainable is- sues. In general, a large amount of cementitious materials, often more than 70% by weight, is used in ECC and no coarse aggregate is allowed to be added. The high volume of cementitious materials in ECC results in a large drying shrinkage and negative effects on material cost and material greenness. In this paper, a new ver- sion of ECC is designed with low volume of cementitious materials about 25% by weight, including Portland cement, blast furnace slag and silica fume, and a large amount of filler and aggregate, including limestone pow- der and river sand. In this mix, only 1.2% of fibers by volume is mixed, which is 60% dosage of standard ECC. Experimental study reveals that the newly developed ECC shows tensile ductility of 2% and relatively low shrinkage. Considering the low cementitious material and fiber contents, the newly developed ECC might have a reduced cost and increased material greenness. 1 INSTRUCTION emerging in broad applications, such as ECC link slab on bridge decks (Michigan DOT 2005), ECC ECC, short for Engineered Cementitious Compos- coupling beam in high-rise buildings to enhance their ites, is a class of ultra ductile fiber reinforced cemen- seismic resistance, composite ECC/steel bridge deck titious composites originally invented at the Univer- and some concrete repair applications (Kunieda & sity of Michigan in the early 1990s (Li 1993). This Rokugo 2006). group of materials is characterized by high ductility in the range of 3-7% and tight crack width of around 60 µm.