Characterizing the nano and micro structure of concrete to improve its durability

Monteiro, Paulo J.M.; Kirchheim, Ana Paula; Chae, Sejung Rosie; Fischer, Peter; MacDowell, Alastair A.; Schaible, Eric; Wenk, H. R.

doi:10.1016/j.cemconcomp.2008.12.007

Cited by 97 publications

(37 citation statements)

References 34 publications

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“…To allow for sufficient transmission of the soft X-rays, a small droplet-containing small solid particles-was taken from the supernatant solution and assembled in a specialized sample holder, comprising of two silicon nitride windows, where the solution is squeezed in between to an appropriate thickness and then imaged. This procedure is described in detail in Silva and Monteiro [16] and Monteiro et al [17].…”

Section: H S Cmentioning

confidence: 99%

Real-Time High-Resolution X-ray Imaging and Nuclear Magnetic Resonance Study of the Hydration of Pure and Na-Doped C₃A in the Presence of Sulfates

et al. 2011

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This study details the differences in real-time hydration between pure (cubic) and Na-doped (orthorhombic) C 3 A. First, pure phases were synthesized in the laboratory to develop an independent benchmark for the reactions, then the reactions of others phases were isolated. Because the kinetics of this reaction moves extremely quickly, most methods are not adequate to study the reactions in the early phases. Here, a high-resolution full-field soft X-ray imaging technique operating in the X-ray water window was used to capture the mechanism of the C 3 A hydration. The results show that there are differences in the hydration mechanism of each type of C 3 A, dependent on the concentration of sulfates ions in solution. The reactions with cubic C 3 A (pure) seems to be more susceptible to higher concentrations of sulfate ions by forming smaller ettringite needles at a slower pace than the orthorhombic C 3 A (Na-doped) sample.Keywords: tricalcium aluminate, hydration, hydration products, ettringite, image analysis IntroductionThe properties of clinkers are strongly affected by the quantity and composition of the clinker phases [1], which can drive the kinetic process of hydration. The hydration of C 3 A is an important stage in the overall hydration of cement because it has considerable influence on its setting and early hardening. The hydration of C 3 A is far more strongly affected by environment conditions than that of C 3 S and, in particular, by the presence of other substances with which it can react [8]. The reaction of C 3 A with water is a primary consideration. Calcium aluminate hydrates (e.g., C 3 AH 6 , C 4 AH 19, and C 2 AH 8 ) form quickly and liberate large amounts of heat [9]. If the very rapid and exothermic hydration of C 3 A is allowed to proceed unhindered in cement, then the setting occurs too quickly and the cement paste does not develop strength. Therefore, calcium sulfate is added to slow down the C 3 A hydration. In the presence of gypsum, C 3 A forms needle-like ettringite. Thus, for practical purposes, it is not the hydration reaction of C 3 A alone that is important but the hydration reaction of C 3 A in presence of gypsum (sulfates). The reactivity of C 3 A in clinker and the availability of sulfate in solution control the setting characteristics of concrete, making these compounds ideal for addressing probable setting problems.Because of the high contents of C 3 A in some cement, special attention must be paid to the mineralogy and reactivity of this phase. Industrial clinkers and their phases contain minor elements such as Na 2 O, K 2 O, SO 3, and Cl -, which may be attributed to several sources, such as raw materials, fuel and/or the lining of the kilns. Alkalis can be incorporated into a number of phases of the clinker and often Na 2 O is

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Section: H S Cmentioning

confidence: 99%

Real-Time High-Resolution X-ray Imaging and Nuclear Magnetic Resonance Study of the Hydration of Pure and Na-Doped C₃A in the Presence of Sulfates

et al. 2011

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“…Beckmann et al, 2007;Meirer et al, 2011), concretes (e.g. Monteiro et al, 2009), fossils (e.g. Gai et al, 2011) and food products (e.g.…”

Section: Introductionmentioning

confidence: 99%

A comparative study of X-ray tomographic microscopy on shales at different synchrotron facilities: ALS, APS and SLS

Kanitpanyacharoen

Parkinson

Carlo

et al. 2012

J Synchrotron Radiat

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Synchrotron radiation X-ray tomographic microscopy (SRXTM) was used to characterize the three-dimensional microstructure, geometry and distribution of different phases in two shale samples obtained from the North Sea (sample N1) and the Upper Barnett Formation in Texas (sample B1). Shale is a challenging material because of its multiphase composition, small grain size, low but significant amount of porosity, as well as strong shape-and lattice-preferred orientation. The goals of this round-robin project were to (i) characterize microstructures and porosity on the micrometer scale, (ii) compare results measured at three synchrotron facilities, and (iii) identify optimal experimental conditions of high-resolution SRXTM for fine-grained materials. SRXTM data of these shales were acquired under similar conditions at the Advanced Light Source (ALS) of Lawrence Berkeley National Laboratory, USA, the Advanced Photon Source (APS) of Argonne National Laboratory, USA, and the Swiss Light Source (SLS) of the Paul Scherrer Institut, Switzerland. The data reconstruction of all datasets was handled under the same procedures in order to compare the data quality and determine phase proportions and microstructures. With a 10Â objective lens the spatial resolution is approximately 2 mm. The sharpness of phase boundaries in the reconstructed data collected from the APS and SLS was comparable and slightly more refined than in the data obtained from the ALS. Important internal features, such as pyrite (high-absorbing), and low-density features, including pores, fractures and organic matter or kerogen (low-absorbing), were adequately segmented on the same basis. The average volume fractions of low-density features for sample N1 and B1 were estimated at 6.3 (6)% and 4.5 (4)%, while those of pyrite were calculated to be 5.6 (6)% and 2.0 (3)%, respectively. The discrepancy of data quality and volume fractions were mainly due to different types of optical instruments and varying technical set-ups at the ALS, APS and SLS.

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“…Classical studies of the microstructure of cement paste and concrete have been largely done using various techniques [1]. techniques has divided these into two categories, direct and Recently, some researches on the artificial neural network (ANN) in data processing are introduced in the field of durability and they are very efficient compared with simple regression method obtained from experimental data [3].…”

Section: Introductionmentioning

confidence: 99%

Modeling The Microstructure Of Slag Blended Cements Using Artificial Neural Network

Ahmed¹

2015

Third International Conference on Advances in Civil, Structural and Construction Engineering - CSCE 2015

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This paper proposes the artificial neural network (ANN) as a numerical technique to simulate the microstructure of slagblended cements. The ANN model adopted in this research consists of three neurons in the input layer which represent contents of both water-cooled slag (WCS) and OPC and WCS finenesses and three neurons in the output layer which represent calcium silicate hydrate (C-S-H), Portalndite (CH), and capillary porosity. Back Propagation algorithm was employed for the ANN training in which a Tansig function was used as the nonlinear transfer function. Thermogravimetric analysis and de-sorption approaches were performed to study the microstructure of the different OPC/slag pastes. The results obtained from experiments agreed with that predicted by ANN, where, the prediction ANN model gives very close estimates of C-S-H, CH, and capillary porosity of OPC/WCS pastes. Therefore, the developed ANN model can be used as an alternative approach to evaluate the microstructure of slag-blended cements.

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Characterizing the nano and micro structure of concrete to improve its durability

Cited by 97 publications

References 34 publications

Real-Time High-Resolution X-ray Imaging and Nuclear Magnetic Resonance Study of the Hydration of Pure and Na-Doped C₃A in the Presence of Sulfates

Real-Time High-Resolution X-ray Imaging and Nuclear Magnetic Resonance Study of the Hydration of Pure and Na-Doped C₃A in the Presence of Sulfates

A comparative study of X-ray tomographic microscopy on shales at different synchrotron facilities: ALS, APS and SLS

Modeling The Microstructure Of Slag Blended Cements Using Artificial Neural Network

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Characterizing the nano and micro structure of concrete to improve its durability

Cited by 97 publications

References 34 publications

Real-Time High-Resolution X-ray Imaging and Nuclear Magnetic Resonance Study of the Hydration of Pure and Na-Doped C3A in the Presence of Sulfates

Real-Time High-Resolution X-ray Imaging and Nuclear Magnetic Resonance Study of the Hydration of Pure and Na-Doped C3A in the Presence of Sulfates

A comparative study of X-ray tomographic microscopy on shales at different synchrotron facilities: ALS, APS and SLS

Modeling The Microstructure Of Slag Blended Cements Using Artificial Neural Network

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Real-Time High-Resolution X-ray Imaging and Nuclear Magnetic Resonance Study of the Hydration of Pure and Na-Doped C₃A in the Presence of Sulfates

Real-Time High-Resolution X-ray Imaging and Nuclear Magnetic Resonance Study of the Hydration of Pure and Na-Doped C₃A in the Presence of Sulfates