Microstructural Gradients in Cement Paste Around Aggregate Particles

1987 ◽  
Vol 114 ◽  
Author(s):  
Karen L. Scrivener ◽  
Ellis M. Gartner
Keyword(s):  
Image Analysis ◽  
Cement Paste ◽  
Interfacial Zone ◽  
Microstructural Investigation ◽  
Analysis Technique ◽  
Single Piece ◽  
Quantitative Image ◽  
Backscattered Electron ◽  
Condensed Silica Fume ◽  
Aggregate Particles

ABSTRACTThe effectiveness of condensed silica fume as a strength enhancing additive in concrete has been attributed to its ability to modify the interfacial zone between paste and aggregate. This paper describes a microstructural investigation of this interface using backscattered electron (bse) imaging combined with quantitative image analysis.Composite specimens were made in which a single piece of aggregate was embedded in cement paste. Granite, dolomite and garnet aggregates were used. After curing, the specimens were sectioned perpendicular to the surface of the aggregate particles and polished. The variation in porosity, amount of anhydrous material and calcium hydroxide (CH), with distance from the aggregate surface was measured. It was found that the porosity increases in the paste close to the interface, while the content of anhydrous grains decreases. No significant increase in CH content was found near the interface.The results confirm the applicability of the bse - image analysis technique, but indicate that the interfaces in specimens prepared in this manner may not be representative of aggregate paste interfaces in concrete.

A Stludy of the Interfacial Region Between Cement Paste and Aggregate in Concrete

1987 ◽  
Vol 114 ◽  
Author(s):  
Karen L. Scrivener ◽  
Alison K. Crumbie ◽  
P. L. Pratt
Keyword(s):  
Image Analysis ◽  
Cement Paste ◽  
Quantitative Image Analysis ◽  
Interfacial Region ◽  
Interfacial Zone ◽  
Preliminary Results ◽  
Quantitative Image

ABSTRACTThe application of quantitative image analysis to the measurenent of microstructural gradients in the interfacial zone in concrete is described. Some preliminary results are presented and discussed.

An Approach to Quantitative Image Analysis for Cement Pastes

1994 ◽  
Vol 370 ◽  
Author(s):  
Yuting Wang ◽  
Sidney Diamond
Keyword(s):  
Image Analysis ◽  
Calcium Hydroxide ◽  
Cement Paste ◽  
Quantitative Image Analysis ◽  
Feature Analysis ◽  
Hole Filling ◽  
Gray Scale ◽  
Cement Pastes ◽  
Quantitative Image ◽  
Average Size

AbstractCement paste microstructure as revealed in backscatter SEM presents a number of inherent difficulties that interfere with implementing quantitative image analysis. An approach to overcoming these difficulties is presented, involving gray scale segmentation coupled with application of a hole filling algorithm. Using this approach it is possible to isolate the unhydrated and hydrated portions of phenograins separately, and to combine them for analysis of combined phenograins. Pores and coarse calcium hydroxide masses may also be isolated for feature analysis. Results are reported on mature cement pastes prepared at two water:cement ratios (w:c 0.45 and w:c 0.30) and with and without superplasticizer. It was found that superplasticizer greatly reduced the content and the average size of “visible pores” and increased the content and the average size of coarse CH particles compared to corresponding plain pastes. The area per hydrated phenograin was much smaller in the lower w:c ratio pastes and higher in superplasticized pastes. Among the solid features measured, unhydrated cement particles had the smallest circularity values (at about 2.7) and were the most circular features; Hydrated phenograins had the largest circularity values (at 3.5) and were the most elongated features.

Digital simulation of the aggregate–cement paste interfacial zone in concrete

1991 ◽  
Vol 6 (1) ◽  
pp. 196-201 ◽  
Author(s):  
Edward J. Garboczi ◽  
Dale P. Bentz
Keyword(s):  
Cement Paste ◽  
Digital Simulation ◽  
Particle Packing ◽  
Diffusion Reaction ◽  
Interfacial Region ◽  
Interfacial Zone ◽  
Two Dimensional ◽  
Portland Cement Concrete ◽  
Quantitative Image ◽  
Characteristic Features

Researchers using backscattered scanning electron microscopy, along with quantitative image analysis techniques, have clearly demonstrated the existence of a highly porous interfacial region between aggregate particles and the cement paste matrix in ordinary Portland cement concrete. This paper presents the results of a digital-image-based simulation model of this interfacial zone. A dissolution-diffusion-reaction-like cycle of hydrating cement particles is directly simulated using cement particles packed around a simple nonreactive aggregate particle. The model is two-dimensional, as we are comparing to experimental results obtained on two-dimensional images of polished sections. The qualitative features seen experimentally, such as large amounts of porosity and calcium hydroxide in the interfacial zone, are accurately reproduced. A new mechanism, one-sided growth, is proposed, along with the more usual particle-packing ideas, as an explanation of the origin of the characteristic features of the interfacial zone.

Mechanical and Microstructural Investigation of the Aggregate and Cement Interface

1994 ◽  
Vol 370 ◽  
Author(s):  
Zongjin Li ◽  
Surendra P. Shah ◽  
Matthew J. Aquino
Keyword(s):  
Closed Loop ◽  
Interface Layer ◽  
Interfacial Zone ◽  
X Rays ◽  
Microstructural Investigation ◽  
Cement Interface ◽  
Backscattered Electron ◽  
Embedment Length ◽  
Electron Imaging ◽  
The Relationship

AbstractThe understanding of the interface between aggregate and cement is crucial in determining the properties of concrete. Recently, a pushout experimental technique and a theoretical model have been developed to determine the stiffness, strength and surface energy of the interface layer. The validity of these material parameters was verified in the present study by examining the effect of diameter and embedment length of aggregate. In addition, the effect of the pretreatment of aggregate surface and various admixtures was investigated. All pushout tests were performed in a closed-loop manner to obtain the load vs. displacement relationship.The interfacial zone was further investigated by using backscattered electron imaging and energy dispersive analysis of x-rays (EDAX) to characterize the microstructure of the interface. The relationship between mechanical properties and microstructure of interfacialzone was studied. It was shown that the microstructure of the interface plays a substantial role in the mechanical behavior of the aggregate/cement bond.

scholarly journals APPLICATION OF IMAGE ANALYSIS TO ASSESSING CRITICAL PORE SIZE FOR PERMEABILITY PREDICTION OF CEMENT PASTE

2011 ◽  
Vol 22 (2) ◽  
pp. 97 ◽  
Author(s):  
Jing Hu ◽  
Piet Stroeven
Keyword(s):  
Image Analysis ◽  
Pore Size ◽  
Cement Paste ◽  
Image Resolution ◽  
Effective Media ◽  
Theory Comparison ◽  
Backscattered Electron ◽  
Image Analysis Techniques ◽  
Insight Into ◽  
Good Agreement

This paper explores image analysis techniques that provide insight into the nature of pore structure as observed in backscattered electron images of polished sections. On the basis of mathematical morphology, the pore size distribution is characterised and the critical pore size is determined for cement paste at different hydration time. The influence of image resolution is investigated. The permeability of cement paste can be predicted according to General Effective Media (GEM) theory. Comparison between permeability estimation and experiment results reveals good agreement.

The Use Of Backscattered Electron Microscopy And Image Analysis To Study The Porosity Of Cement Paste

1988 ◽  
Vol 137 ◽  
Author(s):  
Karen L. Scrivener
Keyword(s):  
Electron Microscopy ◽  
Image Analysis ◽  
Cement Paste ◽  
Serial Section ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Image Analyser ◽  
Backscattered Electron ◽  
Solid Phases ◽  
Serial Section Reconstruction

AbstractIn backscattered electron images of polished sections of cement paste pores can be identified down to a size of about 0.05 microns. Moreover, the contrast between pores and the solid phases is sufficient to allow the pores to be distinguished and quantified by an image analyser. There is a good correlation between measures of porosity obtained by this technique and those obtained by methanol absorbtion methods despite the lower limit to resolution.The bse method can also be used to study the distribution of the porosity in space. However, as only two dimensional sections can be examined, there are difficulties in determining the connectivity by this method. The possibility of using serial section reconstruction is examined and discussed.Despite the difficulty in relating two dimensional characterisation to three dimensional properties, several techniques have been used with some success for sandstones. Results from these techniques for cement paste are presented and discussed.

Characterisation of Microstructure as a Systematic Approach to High Strength Cements

1984 ◽  
Vol 42 ◽  
Author(s):  
Karen L. Scrivener ◽  
K. D. Baldie ◽  
Yick Halse ◽  
P. L. Pratt
Keyword(s):  
Image Analysis ◽  
Fly Ash ◽  
Calcium Hydroxide ◽  
Cement Paste ◽  
Systematic Approach ◽  
High Strength ◽  
Quantitative Image Analysis ◽  
Quantitative Image ◽  
Crack Paths

AbstractUltimately the strength of cement is determined by the properties, amounts and distributions of the phases it contains and by the'way these are bonded together. Here an example is presented of the determination of the amount and distribution of calcium hydroxide, by BEI and quantitative image analysis, in a cement paste and cement/fly ash mixture which had previously been studied by TGA. Examination of crack paths on BEIs of polished cement surfaces gives some indication as to the importance of calcium hydroxide in determining the properties of the cement.

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