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Gu C.-P.,Nanjing Southeast University | Gu C.-P.,Technical University of Delft | Ye G.,Technical University of Delft | Sun W.,Nanjing Southeast University | And 2 more authors.
Journal of Zhejiang University: Science A | Year: 2015

Chloride transport property is very important for the durability and service life of reinforced concrete structures subjected to marine environments and de-icing salt. In reality, for different reasons, concrete structures are frequently cracked, and cracks can alter the chloride transport properties of concrete. Recently, several studies have been conducted by both experiment and simulation on the influence of cracks on the chloride transport properties of concrete. The aim of this paper is to review these research efforts. The experimental methods and simulation approaches on the chloride transport properties of cracked concrete are introduced. Detailed discussions on the findings from these experimental and simulation studies are given. The chloride transport properties of cracked concrete are influenced by various factors, such as crack geometry, concrete composition, and load condition. Research in this area is still on-going, and many problems need to be settled before proposing reliable models for predicting the service life of real cracked concrete structures in chloride environments. Hence, some further research topics are recommended. The influences of other factors, such as carbonation, freeze-thaw, fatigue, and saturation degree, on the transport properties of cracked concrete should be revealed. © 2015, Zhejiang University and Springer-Verlag Berlin Heidelberg. Source


Gu C.P.,Nanjing Southeast University | Gu C.P.,Technical University of Delft | Ye G.,Technical University of Delft | Sun W.,Nanjing Southeast University | And 2 more authors.
Science China Technological Sciences | Year: 2015

Over the last twenty years, remarkable advances have taken place in the research and application of ultra-high performance concrete (UHPC), which exhibits outstanding mechanical properties and excellent durability. It has shown great potential for the next generation infrastructure construction from the sustainability point of view. This paper will give an overview on UHPC, with particular focus on the properties, applications and perspectives. After several decades of development, several types of commercial UHPC materials are available in the market, and the properties of UHPC have been characterized by numerous experimental and field tests. Generally speaking, the performance (e.g. mechanical properties and durability) of UHPC is much better than normal concrete (NC) and high performance concrete (HPC). Therefore, the uses of UHPC are growing all over the world, in both fields of new construction and retrofitting. Nevertheless, it is still a special material and technology, which is not worldwide accepted. So some application prospects of UHPC are briefly introduced in the paper, and the efforts, which have to be made to turn UHPC into a widespread ‘regular’ technology, are discussed. This paper aims to help designers, engineers, architects and infrastructure owners to know the capacities of UHPC and thus to increase the applications of this material. © 2015, Science China Press and Springer-Verlag Berlin Heidelberg. Source


Guo L.P.,Nanjing Southeast University | Guo L.P.,Collaborative Innovation Center for Advanced Civil Engineering Materials | Guo L.P.,Jiangsu Key Laboratory of Construction Materials | Sun W.,Nanjing Southeast University | And 4 more authors.
Science China Technological Sciences | Year: 2015

We introduce a low-cost and effective technique that can transform waste cement-based dust into a superhydrophobic coating with dirt pickup resistance. An organic-inorganic hybrid superhydrophobic coating is prepared by the sol-gel method using methyltriethoxysilane as a precursor and waste cement-based dust as a film-forming material. Orthogonal experiments and a comprehensive scoring method were used to optimize the composition and production technologies. Our results show that this superhydrophobic organic-inorganic hybrid coating has an average static contact angle of 151.65° and low water adhesion. Related tests reveal that the dirt pickup resistance, washing resistance and film-substrate cohesion of this coating are also outstanding. The multi-scale physical and chemical mechanisms behind the properties of the coating are investigated. This recycled cement-based coating can be used as the external cover of engineering structures to protect them from corrosion. © 2015, Science China Press and Springer-Verlag Berlin Heidelberg. Source


Zhang L.,Nanjing Southeast University | Guo L.,Nanjing Southeast University | Guo L.,Collaborative Innovation Center for Advanced Civil Engineering Materials | Guo L.,Jiangsu Key Laboratory of Construction Materials | And 5 more authors.
Kuei Suan Jen Hsueh Pao/Journal of the Chinese Ceramic Society | Year: 2014

In order to investigate the mechanical property and evolution mechanism of ecological high ductility cementitious composites (ECO-HDCC) after subjected to high temperature, the effect of temperature on the compressive strength of ECO-HDCC was analyzed. The micro-morphology and phase composition of the ECO-HDCC subjected at various high temperatures were investigated by scanning electron microscopy, thermogravimetry-differential scanning calorimetry and X-ray diffraction, respectively. The experimental results show that the compressive strength of ECO-HDCC decreases after exposed to 300℃. After 500℃, the compressive strength loss ratio of ECO-HDCC increases from 32.6% to 58.0%. The compressive strength loss ratio of ECO-HDCC after subjected to 800℃ increases from 58.9% to 77.8%. The ECO-HDCC has little load-bearing capacity, and the compressive strength loss ratio is up to 92.5%. It is revealed that the melting and evaporation of PVA fibers at high temperature have pathways for the vapor and the decomposition of hydration products coarsen the microstructure, resulting in the decrease of the compressive strength of ECO-HDCC, and the release of the internal stress of pores in the ECO-HDCC after heat treatment at 1100℃ for 180 min. Source


Gu C.,Nanjing Southeast University | Gu C.,Jiangsu Key Laboratory of Construction Material | Sun W.,Nanjing Southeast University | Sun W.,Jiangsu Key Laboratory of Construction Material | And 6 more authors.
Journal Wuhan University of Technology, Materials Science Edition | Year: 2016

We experimentally investigated the effect of curing conditions on the durability of UHPC under flexural load. Moreover, the mechanisms of the effect of curing conditions were revealed from the microstructural point of view with environmental scanning electron microscopy (ESEM) and X-ray computerized tomography (X-ray CT). The experimental results show that the flexural load has negative influence on the durability of UHPC, but UHPC still exhibits excellent durability under flexural load. Besides, the curing conditions do show influences on the durability of UHPC. Compared with standard and steam curing, oven curing led to a lower chloride resistance and freeze-thaw performance of UHPC. The microstructure of UHPC paste was detected with ESEM. It is revealed that, compared with standard and steam cured UHPC, the lower reaction degree and internal microcracks are the causes for the lower chloride resistance of oven cured UHPC. The defects distribution in UHPC before and after freeze-thaw action was investigated with X-ray CT. The number of defects in oven cured UHPC increases the fastest during the freeze-thaw action due to its more defective microstructure © 2016, Wuhan University of Technology and Springer-Verlag Berlin Heidelberg. Source

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