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2023 | Buch

Mechanical Properties of Cementitious Materials at Microscale

verfasst von: Ya Wei, Siming Liang, Weikang Kong

Verlag: Springer Nature Singapore

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This book provides information on characterizing the microstructure and mechanical properties of cementitious materials at microscale. Specifically, with the intention to provide the methods of preparing the samples for the micro-scale mechanical testing, to address the techniques for measuring and analyzing the elastic modulus, the stiffness, and the fracture toughness of cementitious materials at micro scale by instrumented indentation, to describe a method for measuring and interpreting creep behavior of cementitious materials at micro scale, and to demonstrate the homogenization method for obtaining the mechanical properties of cementitious materials across scales. The information in this book is helpful to a wide readership in the field of civil engineering and materials science working with cementitious materials and other composite materials.

Inhaltsverzeichnis

Frontmatter
Chapter 1. Introduction
Abstract
Currently, cementitious materials have become the most widely-used civil engineering materials around the world, which have been used to construct concrete structures such as buildings, dams, tunnels, bridges, and roads, etc.
Ya Wei, Siming Liang, Weikang Kong
Chapter 2. Samples Preparation
Abstract
Sample preparation is the first step and the prerequisite for successfully conducting the micro scale tests. This chapter summarizes the key points during the preparing process of cementitious materials samples in terms of the procedures of mixing, casting, curing, hydration stoppage, epoxy impregnation, grinding, polishing, and storage. The major conclusions include but not limited to which the epoxy impregnation is encouraged to be used in preparing the samples for NI test, but not for MI test and for characterizing the ITZagg-paste properties by using SPM test, especially for high w/cm ratio cementitious materials. The fine grinding process should adopt less vertical force, lower grinding rate, and shorter grinding time as possible until a slight reflection phenomenon is observed, etc. The content of this chapter can serve as a detailed guidance for preparing qualified cementitious materials samples for the microstructure and the mechanical tests conducted at micro scale.
Ya Wei, Siming Liang, Weikang Kong
Chapter 3. Experimental Techniques
Abstract
In recent years, the advanced techniques have provided powerful tools for characterizing materials at micro- and nanoscales. This chapter reviews the developing history, test principle, parameter setting, and data analysis of a few techniques for measuring the microstructures and the small-scale mechanical properties of cementitious materials, including NI/MI, SPM, nanoscratch, SEM, X-ray CT, and MIP techniques. The instrumented indentation techniques can measure the mechanical properties at the micrometer and nanometer scales. The SPM technique can characterize the mechanical properties as well as the thickness of individual phases under the non-destructive high-resolution conditions. A new loading mode of the constant vertical loading rate is proposed for continuous fracture properties measurement by nanoscratch technique. The content of this chapter can deepen the understanding of current advanced techniques applied to cementitious materials for testing conducted at micro scale.
Ya Wei, Siming Liang, Weikang Kong
Chapter 4. Phase Quantification by Different Techniques
Abstract
It is of significance to identify different phases and quantify the small-scale mechanical properties and microstructure morphology of individual phases in cementitious materials in order to effectively characterize and predict the macroscale response of concrete structures. This chapter illustrates the existing methods of identifying individual phases and quantifying their size and micromechanical properties by using the advanced techniques introduced in Chapter 3. The SPM technique can characterize the mechanical property and distinguish phases as the static NI technique does, but with more attractive features in the form of SPM images. A new method for quantifying ITZ thickness is proposed based on the fracture toughness distribution tested by the nanoscratch technique. The key to identifying phases by the X-ray CT and the BSE techniques is segmenting the phases by the gray level threshold method. This chapter provides detailed and useful methods for quantifying individual phases in cementitious materials
Ya Wei, Siming Liang, Weikang Kong
Chapter 5. Porosity Characterization and Permeability Prediction of Cementitious Materials
Abstract
In view of the difficulty and limitation of the direct experimental measurement of water permeability, particularly for high-strength modern dense concrete, this chapter summarizes the existing techniques and methods to measure the pore parameters and to predict the intrinsic permeability of cementitious materials, including the MIP, BSE, X-ray CT scanning pore measuring techniques, and the Katz-Thompson, the general effective media (GEM), and the Navier–Stokes method for permeability prediction. The predicted intrinsic permeabilities based on the measured microstructure parameters are compared to the experimental results, and the applicability of different techniques and prediction methods are discussed. It is noted that the computed permeability is more suitable as a comparison tool for selecting mixture under the conditions of using the same technique and calculating method. The content of this chapter can provide an insight into the feasibility of the measuring techniques and the predicting method for quantifying the permeability of cementitious materials.
Ya Wei, Siming Liang, Weikang Kong
Chapter 6. Testing and Analysis of Micro Elastic Properties
Abstract
Elastic modulus is one of the key mechanical properties which determines the magnitude of the stress and strain of the structures. This chapter reviews the existing methods to measure the elastic modulus of cementitious materials at both macro and micro scales. The macroscale methods fail to measure the local mechanical properties which instead can be accurately measured by both quasi-static and dynamic indentation techniques. The CSM can assess whether the measured results reflect the homogeneous properties of cementitious materials. The MI test with a load larger than 2 N and a holding period with sufficient duration (generally large than 180 s) is necessary to obtain the homogeneous elastic properties of cementitious materials without the creep effect. This chapter provides various details on measuring the local elastic modulus of cementitious materials.
Ya Wei, Siming Liang, Weikang Kong
Chapter 7. Testing and Analysis of Micro Fracture Properties
Abstract
The fracture properties of cementitious materials have been mainly investigated at macro scale in the last several decades. In view of this, the existing methods for the fracture toughness measurement of the film materials and the rock materials at the micro scales are first summarized in this chapter, including the Lawn–Evans–Marshall (LEM) method and the energy-based method. As a different technique from the LEM method and the energy-based method, the nanoscratch method measures and calculates the fracture properties of individual phases based on the linear elastic fracture mechanics assumption, which is verified to perform well when characterizing the fracture properties of cementitious materials. The fracture toughness can be quantified for individual phases, including the ITZ phase between the unreacted grain and the surrounding hydrate. A linear relationship exists between the macro fracture properties of the paste and the micro fracture properties of the ITZ and the hydrates phases. The nanomaterials such as carbon nanotubes and nanosilica can improve the fracture toughness of both the hydrates and the ITZ phase. The content of this chapter provides guidance on evaluating the fracture behavior of cementitious materials at micro scale.
Ya Wei, Siming Liang, Weikang Kong
Chapter 8. Testing and Analysis of Micro Creep
Abstract
Creep can be beneficial or detrimental for a concrete structure, the fundamental mechanism of which has not been fully understood due to the complex microstructures of cementitious materials. This chapter aims to summarize the current research efforts concerning the testing and analysis of the creep and the creep recovery of cementitious materials at both macro and micro scales. The instrumented indentation technique is used to evaluate the creep behavior of cementitious materials at both nano and micro scales. A strong analogy of the logarithmic creep behavior is found between the cementitious materials and the soils, and the creep modulus is an intrinsic parameter that reflects the long-term creep rate of cement paste. A dashpot with a variable viscosity that increases linearly with time can capture the logarithmic creep behavior. In addition, the ratio of the recoverable creep to the total creep can be obtained based on the measured results using two indentation schemes, i.e., the “loading-holding-unloading-reholding” scheme and the “loading-unloading-reholding” scheme, and the recoverable creep can account for up to 0.41 of the total creep. The content of this chapter is expected to provide an in-depth understanding of the testing and analysis of micro creep and creep recovery of cementitious materials.
Ya Wei, Siming Liang, Weikang Kong
Chapter 9. Multiscale Prediction of Elastic Modulus of Cementitious Materials
Abstract
This chapter discusses the existing multiscale models to predict the elastic modulus of cementitious materials across scales by the micromechanics-based homogenization method, including the Mori–Tanaka method, the self-consistent method, the generalized self-consistent method, and the differential method. To predict the elastic properties, the cementitious materials are usually divided into 3 to 5 scales, and the volume fraction of different phases at different scales can be determined from both the experimental and the theoretical methods. Since the interactions between different phases are not the same among the different homogenization methods, the predicted results may vary accordingly. The imperfect interface is an important factor that affects the accuracy of the multiscale prediction of the elastic property of cementitious materials. However, limited research has been conducted to investigate the actual mechanical properties and thickness of the imperfect interface between different phases in cementitious materials, which deserve systematic research in the future.
Ya Wei, Siming Liang, Weikang Kong
Chapter 10. Multiscale Prediction of Creep Property of Cementitious Materials
Abstract
The existing multiscale models to predict the creep property of cementitious materials by micromechanics-based homogenization are reviewed in this chapter. Since the creep problem is time-dependent, creep prediction of cementitious materials cannot be conducted directly by the micromechanics-based homogenization methods. Both Laplace-Carson transformation and the elastic–viscoelastic correspondence principle are required to transform the creep problem from the time domain to the elastic-like problems without time-dependent features in the Laplace-Carson domain. Based on the micromechanics-based homogenization scheme, the influence of the imperfect interface, the inclusion geometry, the damage condition, and the aging property on the creep development of cementitious materials can be quantified. It is shown that the imperfect interface has a significant effect on the overall creep of cementitious materials. The content of this chapter can provide an in-depth understanding of the multiscale prediction of the creep behavior of cementitious materials.
Ya Wei, Siming Liang, Weikang Kong
Metadaten
Titel
Mechanical Properties of Cementitious Materials at Microscale
verfasst von
Ya Wei
Siming Liang
Weikang Kong
Copyright-Jahr
2023
Verlag
Springer Nature Singapore
Electronic ISBN
978-981-19-6883-9
Print ISBN
978-981-19-6882-2
DOI
https://doi.org/10.1007/978-981-19-6883-9

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