Issue 36

P. Jinchang et alii, Frattura ed Integrità Strutturale, 36 (2016) 130-138; DOI: 10.3221/IGF-ESIS.36.13 130 Improvement of performance of ultra-high performance concrete based composite material added with nano materials Pang Jinchang, Liu Ronggui School of Civil Engineering and Architecture, Nantong Institute of Technology (NIT), Nantong, Jiangsu, 226000, China pjcpangjc@163.com A BSTRACT . Ultra-high performance concrete (UHPC), a kind of composite material characterized by ultra high strength, high toughness and high durability. It has a wide application prospect in engineering practice. But there are some defects in concrete. How to improve strength and toughness of UHPC remains to be the target of researchers. To obtain UHPC with better performance, this study introduced nano-SiO 2 and nano-CaCO 3 into UHPC. Moreover, hydration heat analysis, X-Ray Diffraction (XRD), mercury intrusion porosimetry (MIP) and nanoindentation tests were used to explore hydration process and microstructure. Double-doped nanomaterials can further enhance various mechanical performances of materials. Nano-SiO 2 can promote early progress of cement hydration due to its high reaction activity and C-S-H gel generates when it reacts with cement hydration product Ca(OH) 2 . Nano-CaCO 3 mainly plays the role of crystal nucleus effect and filling effect. Under the combined action of the two, the composite structure is denser, which provides a way to improve the performance of UHPC in practical engineering. K EYWORDS . UHPC; Composite material; Nano material; SiO 2 . I NTRODUCTION ith the continuous development of human society, living space of human is constantly narrowed and buildings tend to be high-rise and long-span. Moreover, concrete structure is increasingly threatened by harsh environment such as ocean and salt lake [1, 2]. Therefore, requirement on performance of concrete materials becomes higher and higher. Ultra-high performance concrete composite (UHPCC) featured by high strength, high toughness, high durability and strong deformation resistance is applied more extensively in harsh environment mentioned above and areas which have special requirements on structure; moreover it shows excellent performance in service process [3, 4]. As to research on UHPC, three international conferences concerning UHPC have been held in Kassel University in German, in September 2005, March 2008, and March 2012 respectively. In the first two conferences, participants illustrated their own research achievements and experience, which mainly include composition and ratio of raw materials, preparation condition, performance, characteristics, strength and toughness of microstructure, design and construction as well as application cases of UHPC in practical engineering worldwide [5]. In addition, multiple international technical standards was discussed. In the third international conference, nanotechnology and nanomaterials were proposed to be introduced into UHPC and the latest research progress of UHPC was also discussed. Nanomaterials as a fine particle between macro substance and cluster possesses small size effect, surface effect, quantum graining effect and macroscopic tunneling effect. How to introduce nanomaterials into concrete has become an issue W