Relationships Between Microstructure and Engineering Properties

1986 ◽  
Vol 85 ◽  
Author(s):  
P. L. Pratt
Keyword(s):  
Fracture Toughness ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Realistic Model ◽  
Engineering Properties ◽  
Bend Strength ◽  
Cement Pastes ◽  
Complex Models

ABSTRACTThe calculation of such macroscopic engineering properties as elastic modulus and compressive strength for cement pastes and concrete depends upon the establishment of a realistic model of the microstructure. Increasingly complex models are considered, which appear capable of predicting the elastic modulus in terms of a modified Rule of Mixtures. The same models are able to account for the broad features of the compressive strength, because strength is always scaled by the elastic modulus of the material. The actual value of the compressive or the bend strength is determined by the mechanics of crack initiation and crack propagation in the particular test used. Crack initiation is controlled by the defects present in the material and crack propagation by the fracture toughness of the different phases and the porosity in the microstructure. Thus the strength depends upon microstructure in a number of different but interrelated ways, determined by the fracture toughness of the material.

scholarly journals Experimental Research on the Mechanical Characteristics and the Failure Mechanism of Coal-Rock Composite under Uniaxial Load

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Ke Yang ◽  
Zhen Wei ◽  
Xiaolou Chi ◽  
Yonggang Zhang ◽  
Litong Dou ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Acoustic Emission ◽  
Elastic Modulus ◽  
Crack Propagation ◽  
Failure Mechanism ◽  
Poisson’S Ratio ◽  
Mechanical Characteristics ◽  
Poisson's Ratio ◽  
Energy Value ◽  
Coal Rock

Due to the influence of the component structure and combination modes, the mechanical characteristics and failure modes of the coal-rock composite show different characteristics from the monomer. In order to explore the effect of different coal-rock ratios on the deformation and the failure law of the combined sample, the RMT rock mechanics test system and acoustic emission real-time monitoring system are adopted to carry out uniaxial compression tests on coal, sandstone, and three kinds of combined samples. The evolution rules of the mechanical parameters of the combined samples, such as the uniaxial compressive strength, elastic modulus, and Poisson’s ratio, are obtained. The expansion and failure deformation characteristics of the combined sample are analyzed. Furthermore, the evolution laws of the fractal and acoustic emission signals are combined to reveal the crack propagation and failure mechanism of the combined samples. The results show that the compressive strength and elastic modulus of the combined sample increase with the decrease of the coal-rock ratios, and Poisson’s ratio decreases with the decrease of the coal-rock ratios. The strain softening weakens at the postpeak stage, which shows an apparent brittle failure. The combined sample of coal and sandstone has different degrees of damages under load. The coal is first damaged with a high degree of breakage, with obvious tensile failure. The acoustic emission energy value presents different stage characteristics with increasing load. Crackling sound occurs in the destroy section before the sample reaches the peak, along with small coal block ejection and the partial destruction. The energy value fluctuates violently, with the appearance of several peaks. At the postpeak stage, the coal samples expand rapidly with a loud crackling sound in the destroy section, and the energy value increases dramatically. The crack propagation induces the damage in the sandstone; when the energy reaches the limit value, the instantaneous release of elastic energy leads to the overall structural instability.

Numerical investigation of micro-cracking behavior of brittle rock containing a pore-like flaw under uniaxial compression

2020 ◽  
Vol 29 (10) ◽  
pp. 1543-1568 ◽  
Author(s):  
Louis Ngai Yuen Wong ◽  
Jun Peng
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Numerical Model ◽  
Crack Initiation ◽  
Uniaxial Compression ◽  
Uniaxial Compressive Strength ◽  
Early Stage ◽  
Brittle Rock ◽  
Cracking Behavior ◽  
Cracking Process

Pore-like flaws, which are commonly encountered in brittle rock, play an important role in the engineering performance of structures constructed in or on rock. Experimental and numerical investigations of micro-cracking mechanism of rock containing a pore-like flaw can enhance our knowledge of rock damage/failure from a microscopic view. In this study, the influences of a two-dimensional circular pore-like flaw with respect to its diameter and position on the strength and micro-cracking behavior of brittle rock under uniaxial compression are numerically investigated. The results reveal that the strength and elastic modulus are significantly affected by the diameter and position in the pore. The uniaxial compressive strength and elastic modulus of the numerical model with a pore diameter of 15.44 mm located in the center of the model are found to decrease by 58.6% and 56.4% respectively when compared with those of the intact model without a pore. As the pore position varies while the porosity remains unchanged, the simulated uniaxial compressive strength and elastic modulus are also found to be generally smaller than those of the intact model without a pore. When a pore-containing numerical model is loaded, the micro-cracks are found to mostly initiate at the top and bottom of the pore, due to the local tensile stress increase. The simulation results of the early-stage micro-cracking process and stress distribution are in a generally good agreement with the analytical solution obtained from the Kirsch equations. The grain-based model used in this study can not only study the crack initiation on the boundary of the pore but also provide a convenient means to analyze and visualize the temporal and spatial micro-cracking process after the crack initiation, which accounts for the variations in the simulated strength and modulus satisfactorily from a micro-cracking view.

Literature Review: Properties of Silica Fume Concrete

2014 ◽  
Vol 1004-1005 ◽  
pp. 1516-1522
Author(s):  
Xi Xi He ◽  
Qing Wang
Keyword(s):  
Fracture Toughness ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Silica Fume ◽  
Water Demand ◽  
Interfacial Transition Zone ◽  
Normal Concrete ◽  
Plastic Shrinkage ◽  
Micro Level

Silica fume (SF) modifies interfacial transition zone between cement paste and aggregate at the micro level. Properties of both fresh and hardened silica fume concrete are affected significantly compared to normal concrete. Experiments indicate that concretes become more cohesive and less prone to segregation in the presence of silica fume, moreover, performance of water demand, setting of time, plastic shrinkage varies respectively from concretes without silica fume. Obvious mechanical enhancement of concrete is observed in the aspects of compressive strength tensile strength, elastic modulus as well as fracture toughness.

Fracture toughness and failure mechanisms in un-vulcanized and dynamically vulcanized PP/EPDM/MWCNT blend-nanocomposites

RSC Advances ◽  
2015 ◽  
Vol 5 (87) ◽  
pp. 70817-70831 ◽  
Author(s):  
Mehrdad Khodabandelou ◽  
Mir Karim Razavi Aghjeh ◽  
Majid Mehrabi Mazidi
Keyword(s):  
Fracture Toughness ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Failure Mechanisms ◽  
The Individual ◽  
P Addition ◽  
Blend Nanocomposites

Addition of MWCNTs into the PP/EPDM blend reduced the we and enhanced the βwp. In the blend-nanocomposites large MWCNT aggregates acted as favored sites for crack initiation, and the individual MWCNT impregnated fibrils arrested the crack propagation.

Fracture Toughness of a Silica-Doped Cubic Zirconia (8Y-CSZ)

2010 ◽  
Vol 638-642 ◽  
pp. 3846-3851 ◽  
Author(s):  
Keijiro Hiraga ◽  
Koji Morita ◽  
Byung Nam Kim ◽  
Hidehiro Yoshida
Keyword(s):  
Fracture Toughness ◽  
Elastic Modulus ◽  
Crack Propagation ◽  
Glass Phase ◽  
Indentation Method ◽  
Grain Sizes ◽  
Pure Silica ◽  
Beam Method ◽  
The Matrix ◽  
A Site

In a high-purity 8Y-CSZ, the doping of 0.15 - 5 mass% pure silica introduces a glass phase dispersing uniformly along grain-boundary facets and at multiple junctions. For materials with grain sizes of 0.75 - 2.4 m, the dispersion of the glass phase decreases the elastic modulus, the Vickers hardness and the elastic modulus-to-hardness ratio, whereas it affects little in the fracture toughness measured by a Vickers-indentation method and a single-crack-precracked-beam method. Inspection of crack propagation paths shows that the glass phase with sizes smaller than those of the matrix grains is not a site for easy crack-propagation, but provides a site for a crack-deflection mechanism.

Determination of Compressive Strength of Cement and Polymer-Modified Cement Pastes with Pozzolans

2015 ◽  
Vol 1122 ◽  
pp. 31-34
Author(s):  
Nikol Žižková ◽  
Patrik Bayer
Keyword(s):  
Fracture Toughness ◽  
Compressive Strength ◽  
Bond Strength ◽  
Ethylene Vinyl Acetate ◽  
Mechanical Parameters ◽  
Cement Pastes ◽  
Pozzolanic Materials ◽  
Acetate Copolymer ◽  
Ethylene Vinyl Acetate Copolymer

The article focuses on the use of tree types of pozzolanic materials in the production of cement pastes and polymer-modified cement pastes. The determined physical-mechanical parameters of the pastes with pozzolanic materials were compared with a pure cement paste. For polymeric modification, ethylene/vinyl acetate copolymer (EVA) was used, which was added to the mortar and concrete during the preparation to improve some properties such as fracture toughness, impermeability and bond strength to various substrates.

Engineering Properties of Controlled Low-Strength Material Made with Residual Soil and Class F Fly Ash

2014 ◽  
Vol 597 ◽  
pp. 345-348 ◽  
Author(s):  
Yeong Nain Sheen ◽  
Li Jeng Huang ◽  
Duc Hien Le
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Fly Ash ◽  
Setting Time ◽  
Engineering Properties ◽  
Residual Soil ◽  
Strength Material ◽  
Low Strength ◽  
Controlled Low Strength Material ◽  
Class F Fly Ash

This paper aims to employ combination of residual soil and Class F fly ash in developing a controlled low-strength material (CLSM), primarily used as backfilling material. In the mixture, surplus soil and concrete sand was blended well together with a given proportion of 6:4 by volume. Three levels of binder content (i.e. 80-, 100-and 130 kg/m3) and different percentages fly ash (i.e., 0%, 15%, 30%, and 45%) substituting to Portland cement were previously chosen for mix design. Several major engineering properties of the CLSM such as fresh density, flowability, setting time, water bleeding, unconfined compressive strength, and elastic modulus were investigated via a laboratory study. Testing results indicate that most of the proposed CLSM mixtures satisfy the requirements of excavatability as the 28-days compressive strength ranges from 0.3 to 1.4 MPa. In addition, increase in FA substituting to OPC resulted in workability improvement, setting time extension as well as compressive strength and elastic modulus reduction.

THE EFFECT OF POROSITY ON ENGINEERING PROPERTIES OF VESICULAR AMYGDALOIDAL BASALTS

2021 ◽  
Vol 5 (11) ◽  
Author(s):  
P .S.K.Murthy ◽  
Sachin Gupta ◽  
Dhirendra Kumar ◽  
Mahabir Dixit
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Uniaxial Compressive Strength ◽  
Modulus Of Elasticity ◽  
Poisson’S Ratio ◽  
Central India ◽  
Poisson's Ratio ◽  
Engineering Properties ◽  
Secondary Minerals

The interconnection of vesicles in basaltic flows greatly affects the engineering properties such as uniaxial compressive strength, modulus of elasticity, Poisson’s ratio, tensile strength and sonic velocities. Sometimes these vesicles are filled with secondary minerals such as quartz/olivine/calcite form as amygdules (which are impermeable). In the present study, to understand effect of porosity, vesicular and amygdular basaltic flows collected from central and west-central India were investigated for these engineering properties and correlated with apparent porosity of core samples. It is observed that a good level of correlation is obtained for uniaxial compressive strength (UCS), elastic modulus (E) and Poisson’s ratio in vesicular basalts when porosity >8-10%. In case of Brazilian strengths a linearly downward trend is observed with the increase in porosity values. And, no significant correlation is observed for waves’ velocities in both variants of basalts.

scholarly journals Crack Initiation Characteristics of Gas-Containing Coal under Gas Pressures

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Zhiqiang Yin ◽  
Zhiyu Chen ◽  
Jucai Chang ◽  
Zuxiang Hu ◽  
Haifeng Ma ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Crack Initiation ◽  
Uniaxial Compressive Strength ◽  
Coal Mines ◽  
Gas Pressure ◽  
Loading Test ◽  
Working Face ◽  
Gas Pressures

In deep coal mines, coal before the working face is subjected to coupled high mining-induced stress and gas pressure. Such condition may facilitate crack formation and propagation in the coal seam, leading to serious coal and gas disasters. In this study, the mechanical properties (i.e., uniaxial compressive strength, tensile strength, and fracture toughness) of gas-containing coal with four levels of initial gas pressure (i.e., 0.0, 0.5, 1.0, and 1.5 MPa) were investigated by uniaxial compression, Brazilian disc, and notched semicircular bending loading test. A newly developed gas-sealing device and an RMT-150 rock mechanics testing machine were used. Fracture modes under different initial gas pressures were also determined. A theoretical method of fracture mechanics was used to analyze crack initiation characteristics under gas adsorption state. Results show that the uniaxial compressive strength, tensile strength, and fracture toughness of gas-containing coal decreased with increasing initial gas pressure. The tensional fracture occurred in gas-containing coal under uniaxial compressive loading with high gas pressure. Cracks in gas-containing coal propagated under small external loads due to the increase in effective stress of crack tip and decrease in cracking strength. This study provided evidence for modifications of the support design of working face in deep coal mines. Furthermore, the correlations between fracture toughness, compressive strength, and tensile strength of gas-containing coal were investigated.

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