Investigating pore structure of nano-engineered concrete with low-field nuclear magnetic resonance
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Investigating pore structure of nano-engineered concrete with low-field nuclear magnetic resonance Jialiang Wang1, Sufen Dong2,*, Chunsheng Zhou3, Ashraf Ashour4, and Baoguo Han1,*
1
School of Civil Engineering, Dalian University of Technology, Dalian 116024, China School of Material Science and Engineering, Dalian University of Technology, Dalian 116024, China 3 School of Civil Engineering, Harbin Institute of Technology, Harbin 150090, China 4 Faculty of Engineering and Informatics, University of Bradford, Bradford BD7 1DP, UK 2
Received: 2 July 2020
ABSTRACT
Accepted: 23 August 2020
Pore structure, the most important structural feature of reactive powder concrete (RPC) with nanofillers, is closely related to the dispersion quality, content level and internal structure of nanofillers. In order to characterize the pore structure of RPC and comprehensively understand the effect of nanofillers on the microscopic behavior of concrete, this paper studies the pore structure of RPC containing different types (including zero-dimensional nanoparticles, onedimensional nanotubes and two-dimensional nanosheets) and content (0.25–3%) of nanofillers by using low-field nuclear magnetic resonance. The experimental results show that incorporation of all types of nanofillers reduces the porosity of RPC and causes shrinkage of gel pores and fine capillary pores. Among different types of nanofillers, one-dimensional nanotubes are most beneficial to reduce porosity, and zero-dimensional nanoparticles have a more pronounced effect on reducing pore size. The effect of nanofillers on the pore structure of RPC is mainly attributed to the conversion of pore water inside C–S–H gel, inducing reorganization of gel structure. Specifically, nanoparticles cause the gel layer surrounding the pore water to shrink or even partially collapse, while nanotubes and nanosheets fill the collapsed gel layers with pore water, in turn, producing a slight swell between gel layers. It is the slight changes in the microstructure of C–S–H gel that cause shrinkage and deformation of concrete materials at the macroscopic scale, which, in turn, greatly affects the overall performances of RPC with nanofillers.
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Springer Science+Business
Media, LLC, part of Springer Nature 2020
Handling Editor: M. Grant Norton.
Address correspondence to E-mail: [email protected]; [email protected]
https://doi.org/10.1007/s10853-020-05268-0
J Mater Sci
Introduction Concrete is the most widely consumed construction material. However, it typically exhibits low tensile strength and poor deformability. With the scale of infrastructure and complexity of service environment, problems such as insufficient mechanical properties and poor durability of concrete have become increasingly prominent [1, 2], requiring further attention to improve the fineness and reduce pores and micro-cracks in concrete. Reactive powder concrete (RPC) is an ultra-high-performance concrete, having average particle size of raw materials between 0.1 lm and 1 mm, effectively reducing pore size
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