Investigation of influence of nano-reinforcement on the mechanical properties of composite materials

Abstract

The present work studies the possibility to decrease the formation of micro and nano cracks around short fibres in fibre-reinforced concrete (FRC) composite with the help of nano-reinforcement, which is carbon nanotubes, or micro reinforcement, which is carbon short fibres and nano-fillers. Tensile and bending strength of FRC depends on the spatial distribution of fibres inside a material, type of fibre and cement matrix, as well as an effective micromechanical work of each fibre while pulling out of the concrete matrix. Shrinkage stresses, acting in the matrix in the vicinity of a fibre, lead to the formation of micro-cracks. Such micro-cracks were observed experimentally and were investigated numerically performing broad modelling based on the finite element method (FEM). The investigation was focused on the micromechanical behaviour of a single steel fibre in a cement matrix. Numerical modelling results demonstrated a high level of shrinkage overstresses around steel fibres in concrete. The role of nano and micro admixtures, nanotubes, short carbon fibres as well as the role of water/cement ratio in a high performance concrete matrix, changing (increasing or decreasing) the friction force between the matrix and the steel fibre, were investigated experimentally by way of performing a single fibre pull-out tests. The high scatters of experimental results were obtained in performed pull-out tests. At the same time, for the same series of samples, a positive role of micro and nano admixtures and carbon nanotubes in the increase of pull-out force was recognised.

Keywords:

• fibre concrete
• pull-out
• nano admixture
• cement matrix

Additional information

Notes on contributors

Olga Kononova

Olga KONONOVA. Dr Sc. Ing. (PhD) in Mechanics received in 2005, professor since 2012. Fields of interest; material mechanics, composite materials, concretes, experimental investigations and numerical modelling. Author of more than 100 scientific publications and 7 invention patents. Participant of four EU research projects and leader of seven domestic research projects. Author and co-author of more than 20 Scopus referenced papers.

Andrejs Krasnikovs

Andrejs KRASNIKOVS. Professor, Corresponding Member of the Latvian Academy of Sciences. Dr Sc. Ing. (PhD) in Mathematics and Physics received in 1986. Head of Concrete Mechanics Laboratory since 2000, professor since 2006. Visiting professor of Virginia Tech (US) (2000); visiting researcher of Lulea Tech (Sweden) (2002). Academic fields of interest: materials mechanics, composite materials, nano-materials, concretes, asphalts, experimental mechanics and numerical investigations. Author of more than 180 scientific publications and 25 invention patents. During the last five years, RTU contractor and tasks leader in three large international and more than ten regional scientific research projects.

Rimvydas Stonys

Rimvydas STONYS. Dr, Senior Researcher, Laboratory of Building Products Technology, Scientific Institute of Thermal Insulation of Vilnius Gediminas Technical University, Lithuania. Research interests: materials science, application of nanotechnologies in cementitious materials, refractory concretes and their application.

Genadijs Sahmenko

Genadijs SAHMENKO. In 1991, he graduated the Faculty of Civil Engineering of Riga Technical University. In 1995, he received the Master's Degree in Engineering Sciences. In 2005, he was awarded the Doctor's Degree in Engineering Sciences in the field of the Construction Science. Currently, he is a leading researcher of the Department of Building Materials and Products. Fields or research: high performance concrete, self-compacting concrete, eco-insulating materials based on natural fibres. He is a member of the Latvian Concrete Society and the Editor-in-Chief of the RTU Scientific Journal “Construction science”.

Renars Vitols

Renars VITOLS. He graduated from the mechanical engineering of Riga Technical University (RTU) in 2012. He is a PhD student in applied mechanics at RTU. His research goal is to develop a new type of continuous contractile dielectric elastomer actuator. Main fields of interest: mechanics of materials, calculation of stress and strain by FEM, morphing structures and smart materials based on electroactive polymers.