Microstructure and functional properties of rock materials

doi:10.1016/j.matchar.2007.04.012

Materials Characterization

Volume 58, Issues 11–12, November–December 2007, Pages 1183-1188

https://doi.org/10.1016/j.matchar.2007.04.012 Get rights and content

Abstract

The properties of stone materials maybe divided into intrinsic properties such as chemical and mineralogical composition, grain size and porosity, and into functional properties related to a technical application. The latter describe how the stone responds to conditions in the environment such as mechanical load, freeze–thaw cycles and exposure to moisture, and are controlled by the intrinsic properties. This implies that intrinsic properties can be used in order to assess the functional properties of the stone if it is possible to identify and quantify the related critical parameters. While this is an accepted approach for metals and ceramics, it has not been applied to the same extent to rock materials. The aim of this paper is to demonstrate that this approach also has potential in petrographic analysis.

Introduction

The aim of this paper is to give a short introduction to the relationship between intrinsic properties, such as mineralogy and microstructure, and functional and durability properties of stone and rocks used as construction materials. The emphasis is on properties that can be observed with the naked eye, an optical microscope or with a scanning electron microscope. Properties and relationships that are comprehensively described elsewhere, such as the alkali silica reactivity of rock aggregates in concrete, are not included in this paper. The influence of chemically aggressive environments is only treated briefly. The relation between porosity and fluid flow has been studied extensively by petroleum petrologists; e.g. [1]. The basis for the present paper is the use of quantitative microstructural analysis for the evaluation of functional properties, which is an accepted approach in metallurgy. It is much less widely used on rocks. One obvious reason for this is the complexity of rock materials and the variation in quantitative relationships between different rock types. The application of quantitative microscopic methods in this field has however resulted in much new knowledge, e.g. [2]. The emphasis in this paper is on rock types commonly used as bound and unbound aggregate; however, rock types used as natural stone are also included, although treated more briefly.

The mechanical testing generally applied in this field provides a numerical value directly related to the test method that is assumed to reproduce a degradation mechanism, such as the resistance to fragmentation as tested with the LA-drum. This gives an assessment of the tested material in relation to this process, but it provides no understanding of the mechanism or which parameters have an important influence. The resistance of rocks to different types of chemically aggressive and physically degrading environments is governed by their intrinsic properties, such as mineralogical and microstructural parameters. The limiting properties differ with the environment and type of degradation. Furthermore, cracks and pores also have a strong influence on strength and moisture properties. Different physical and chemical environments cause a wide variety of damage and durability problems. These range from stress that may cause failure and fragmentation or wear that may damage the surface of the stone, to damage due to a chemically aggressive environment. The combination of materials and their compatibility also influence the durability of rock materials in a construction.

The methods applied in petrographic analysis for technical applications are to a large extent based on methods developed for petrogenetic studies. These methods also provide important information for technical applications, but there is a need to develop new tools for technical purposes. One aim of the present paper is to give information that can constitute a step in that direction.

Section snippets

Influence of mineralogy

The properties of the individual minerals that make up the rock are a limiting factor for the physical and chemical properties of the rock. The properties and influences of single minerals are fairly well known and are only briefly treated here. Hardness, defined as resistance to indentation, is a property that is directly related to the average hardness of the minerals in the rock surface. But it is evident that the strength, fracture toughness and modulus of elasticity of the individual

Influence of grain size

It has long been recognised that there is a general trend towards higher strength in finer grained rocks of the same type, and Erkan [4] demonstrated that the compressive strength of granites increased with increasing specific surface. A coarse-grained rock generally has both low strength and low fracture toughness. It is not only the grain size but also the grain size distribution that is important, with the effect that a large size range gives higher strength and better resistance to

Influence of grain and grain boundary shape

The shape of the minerals depends largely on their surface energy and the physical and chemical environment in which the rock was formed. Minerals with high surface energy tend to develop their crystal shapes at the expense of the surrounding minerals. Minerals that form euhedral grains may act as discontinuities in the structure where cracks may initiate.

An increased complexity in the grain shape and grain boundary geometry increases the strength of the boundary. This may consist of a

Influence of mineral orientation and spatial distribution

The properties of a rock with an oriented structure differ from that of a rock with random orientation. There is a difference between the orientation of the mineral grains based on the shape of the different mineral grains, i.e. shape-preferred orientation, and orientation based on the orientation of the atomic lattices of the different mineral grains, i.e. lattice-preferred orientation. Shape-preferred orientation may form planes of weakness in a structure. A foliation defined by micas or clay

Influence of porosity and cracks

The volume of a rock that is not composed of solids, i.e., its porosity, also influences the functional properties. The porosity of rocks is generally low compared with other building materials such as concrete and bricks. The moisture properties are directly related to porosity. Water present in the finer pores is bound tightly to the material and the contribution of the finer pores to capillary transport is more limited. The somewhat coarser pores contribute to capillary water transfer.

Conclusions

Existing knowledge can to a large extent explain and predict the functional properties of rock materials. Quantitative textural and microstructural analysis can thus be used in order to assess functional properties that are important in technical applications. The petrographic analysis performed today is largely based on parameters and methods used for a petrogenetic description of the rock. This gives much information about the technical properties and one aim of this paper is to demonstrate

References (23)

U. Åkesson et al.
The influence of foliation on the fragility of granitic rocks, image analysis and quantitative microscopy
Eng Geol
(2003)
F.S. Anselmetti et al.
Quantitative characterisation of carbonate pore systems by digital image analysis
AAPG Bull
(1998)
W.J. French
Quantitative polarising microscopy applied to concrete, road aggregate and armorstone
E.M. Winkler
A durability index for stone
Y. Erkan
Zum Einf luss einiger Gefygeparameter auf die Wyrfeldruckfestigkeit der Granite
Rock Mech
(1971)
Lundqvist, S., Göransson, M.J., Evaluation and interpretation of microscopic parameters vs. mechanical properties of...
K. Malaga-Starzec et al.
Microscopic and studies on the porosity of marble as a function of temperature and impregnation
P. Sulovský
The postmagmatic alteration of allanite, zircon, and thorite: the role of fluorine
Åkesson U. Microstructures in granites and marbles in relation to their durability as construction materials. Doctoral...
U. Åkesson et al.
Relationship between texture and mechanical properties of granites, central Sweden, by use of image-analysing technique
Bull Eng Geol Environ
(2001)

D.F. Howarth

Experimental study on the relationship between rock texture and mechanical performance

Trans Inst Min Metall (Sect A Mining industry)

(1988)

Cited by (114)

A novel grain growth algorithm for grain-based models for investigating the complex behavior of crystalline rock
2024, Computers and Geotechnics
The mineralogical composition and microstructure of crystalline rock affect its mechanical properties. However, it is challenging to analyze and quantify the associated mechanisms using experimental methods. A potential solution to this problem is to apply microscopic simulation methods, such as a combination of the discrete element method and grain-based model (GBM). A prerequisite for microscopic simulations is to accurately reproduce the microscopic features, especially the interactions between grains. Inspired by the crystallization of polycrystalline rocks, a novel grain growth algorithm that constructs a GBM by simulating the sequential crystallization process is proposed in this paper. The results of comprehensive analyses show that the proposed modeling method can accurately reproduce the mineralogical compositions, euhedral-to-anhedral morphology transitions, and grain size distributions during different crystallization processes. By accurately reproducing the interlocking structure between grains, the proposed method can simulate typical mechanical behaviors, such as the nonlinear strength envelope, uniaxial compressive strength-to-tensile strength ratio, and bimodularity, which are consistent with the experimental findings. The effectiveness of this method in modeling porphyritic structures and grain-scale anisotropic textures is demonstrated, and the microscopic mechanism of fracture mode transition associated with the difference in grain structures is discussed.
Temperature dependence of mechanical properties and damage evolution of hot dry rocks under rapid cooling
2024, Journal of Rock Mechanics and Geotechnical Engineering
Understanding the differences in mechanical properties and damage characteristics of granitoid under high temperatures is crucial for exploring deep geothermal resources. This study analyzes the evolution of the acoustic emission (AE) characteristics and mechanical parameters of granodiorite and granite after heating and water cooling by uniaxial compression and variable-angle shear tests under different temperature gradients. We identify their changes in mesostructure and mineral composition with electron probe microanalysis and scanning electron microscopy. Results show that these two hot dry rocks have similar diagenetic minerals and microstructure, but show significantly different mechanical and acoustic characteristics, and even opposing evolution trends in a certain temperature range. At the temperatures ranging from 100 °C to 500 °C, the compressive and shear mechanical properties of granodiorite switch repeatedly between weakening and strengthening, and those of granite show a continuous weakening trend. At 600 °C, both rocks exhibit a deterioration of mechanical properties. The damage mode of granite is characterized by initiating at low stress, exponential evolutionary activity, and intensified energy release. In contrast, granodiorite exhibits the characteristics of initiating at high stress, volatile evolutionary activity, and intermittent energy release, due to its more stable microstructure and fewer thermal defects compared to granite. As the temperature increases, the initiation and propagation of secondary cracks in granodiorite are suppressed to a certain extent, and the seismicity and brittleness are enhanced. The subtle differences in grain size, microscopic heterogeneity, and mineral composition of the two hot dry rocks determine the different acoustic-mechanical characteristics under heating and cooling, and the evolution trends with temperature. These findings are of great significance for the scientific and efficient construction of rock mass engineering by rationally utilizing different rock strata properties.
Physical weathering of Gobi Desert sediments under different temperature and humidity conditions
2024, Catena
Physical weathering of the Gobi Desert surface sediments involves complex processes. However, our understanding of its main driving factors is still limited, and experimental observations on the weathering intensity of Gobi Desert surface sediments under changing environmental conditions are still insufficient. Surface samples were collected from the Gobi Desert, divided into 0.063–0.125 mm, 0.125–0.25 mm, 0.25–0.5 mm, 0.5–1 mm and 1–2 mm groups, and washed with deionized water. Physical weathering and salt weathering experiments of these groups were conducted under temperature (T) of −40 °C–40 °C and relative humidity (RH) of 20 %–100 %. Salt and mineral analyses, grain size distribution, and morphology analysis of each fraction group before and after the experiments were conducted. The results showed that mean grain sizes for the 0.063–0.125 mm, 0.125–0.25 mm, 0.25–0.5 mm, 0.5–1 mm, and 1–2 mm groups decreased by 0.49 ± 1.09 %, −0.27 ± 2.14 %, 0.41 ± 3.14 %, 2.96 ± 3.14 %, and 0.19 ± 1.29 %, respectively. The mean size of each group decreased ∼ 0.76 ± 1.13 % /10 days, demonstrating a higher physical weathering intensity than the previous estimations. The d_0.1 size (i.e., the grain diameter for which 0.1 % of each grain group is smaller) was more sensitive to physical weathering, and the skewness was a good indicator of physical weathering for groups obeying a normal distribution. Physical weathering was still affected by salt weathering, and there was no regular pattern for physical weathering under variations in salt and mineral contents. At present, there are still difficulties in developing an accurate physical weathering intensity model.
Study of effective elastic properties of heterogeneous materials with an artificial neural network model
2023, Mechanics of Materials
This paper is devoted to the estimation of macroscopic elastic properties of composites containing inclusions and pores. Some representative analytical homogenization models are first recalled and their weaknesses are highlighted by comparisons with the reference numerical results obtained from direct simulations by a Fast Fourier Transform (FFT) method. A large data set is then constructed also based on numerical results obtained from FFT simulations for different types of micro-structures and for a large range of elastic properties of constituents. An artificial neural network (ANN)-based model containing two hidden layers is constructed and trained by using this data set. Different types of validation tests of the ANN model are presented. It is found that the ANN-based model can estimate the macroscopic elastic properties of strongly heterogeneous materials with a very good accuracy, for different types of micro-structures and a large range of porosity and inclusion volume fraction.
Effects of sandstone mineral composition heterogeneity on crack initiation and propagation through a microscopic analysis technique
2023, International Journal of Rock Mechanics and Mining Sciences
Crack initiation and propagation are key scientific questions influencing rock failure. To study crack initiation and propagation during rock failure, CT scanning tests were performed on the sandstone samples. The initiation and propagation stages of sandstone cracks were analysed based on a reconstructed three-dimensional crack structure model. The types of crack initiation and propagation in minerals and the effects of mineral composition heterogeneity on crack initiation and propagation were studied using microscopic analytical techniques. The effect of mineral granularity on crack initiation and propagation was analysed using statistical methods. The results show that crack initiation and propagation can be divided into four stages: microcrack inoculation, mesocrack initiation, mesocrack evolution to macrocrack, and macrocrack penetration. Four cracks are formed at different locations, extending along the mineral edge, deflecting at the mineral edge, bifurcating at the mineral edge, and penetrating through the mineral. The poikilitic texture formed by quartz debris and cement makes it easy for cracks to extend along the mineral edges. In quartz debris with high crystallinity, the crack tends to deflect and bifurcate at the edge of quartz debris. The symbiotic structure of altered quartz and clay minerals easily causes cracks to propagate through the minerals. Furthermore, the distribution of mineral granularity affects crack initiation and propagation. The inhomogeneity of mineral granularity can easily cause the initiation and propagation of cracks. The size of the mineral granularity affects the width of the secondary crack. These research results can provide a basis and reference for predicting and evaluating the stability of rock masses.
Investigating the textural and physico-mechanical response of granites to heat treatment
2023, International Journal of Rock Mechanics and Mining Sciences
This study investigates the petrographic changes associated with heat treatment of texturally variant granites from northwest Pakistan. The corresponding effects on the physico-mechanical properties have also been analyzed. Detailed microscopic observations distinguish collected rocks into (i) Alkali feldspar micro-porphyritic variety of Ambela granite (AFG) (ii) coarse grained Malakand granite (MG) (iii) mega-porphyritic Utla granite (UG). The non-destructive tests including ultrasonic pulse velocity, Schmidt rebound hardness, porosity, specific gravity and water absorption of studied granites are markedly influenced by temperature variation. Particularly at temperature ≥600 ⁰С, a drastic decreasing trend observed with temperature rise. Significant instability in minerals has been noted with increasing temperature shown by the initiation of thermally induced fractures and widening of pre-existing cracks. Pre-existing fractures in major minerals including feldspars and quartz expand with increasing temperature accompanied by the novel fractures induced due to high thermal stresses that also effects the physical and mechanical properties. The relatively more altered UG is more prone to textural changes associated with heat treatment and the effects can be seen at lower temperatures than other studied fresh granites.

View all citing articles on Scopus

View full text

Microstructure and functional properties of rock materials

Abstract

Introduction

Section snippets

Influence of mineralogy

Influence of grain size

Influence of grain and grain boundary shape

Influence of mineral orientation and spatial distribution

Influence of porosity and cracks

Conclusions

Eng Geol

Quantitative characterisation of carbonate pore systems by digital image analysis

AAPG Bull

Quantitative polarising microscopy applied to concrete, road aggregate and armorstone

A durability index for stone

Zum Einf luss einiger Gefygeparameter auf die Wyrfeldruckfestigkeit der Granite

Rock Mech

Microscopic and studies on the porosity of marble as a function of temperature and impregnation

The postmagmatic alteration of allanite, zircon, and thorite: the role of fluorine

Relationship between texture and mechanical properties of granites, central Sweden, by use of image-analysing technique

Bull Eng Geol Environ

Experimental study on the relationship between rock texture and mechanical performance

Trans Inst Min Metall (Sect A Mining industry)