The Experts below are selected from a list of 9462 Experts worldwide ranked by ideXlab platform
Christopher Hall - One of the best experts on this subject based on the ideXlab platform.
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Hygric properties of porous building materials (VI) : a round robin campaign
Building and Environment, 2020Co-Authors: Chi Feng, Christopher Hall, Ana Sofia Guimarães, Nuno M.m. Ramos, Lixin Sun, Dariusz Gawin, Piotr Konca, Jianhua Zhao, Hauke Hirsch, John GrunewaldAbstract:Abstract Hygric properties of porous building materials are important for hygrothermal analysis. Their experimental determination is however not always reliable, shown by the discrepant results from different laboratories on the same materials. In this study, a recent round robin campaign initiated by KU Leuven (Belgium) and participated in by eight institutes from different countries is reported. Ceramic brick was selected as the target material. The bulk density and open porosity from vacuum saturation tests, the Capillary Absorption coefficient and Capillary moisture content from Capillary Absorption tests, and the vapor permeability from cup tests were measured. Results were analyzed statistically and compared with a previous round robin project, EC HAMSTAD. The reproducibility errors for determining the Capillary Absorption coefficient were noticeably reduced when compared with the EC HAMSTAD project, and the different laboratories in the present study obtained similar results from vacuum saturation tests and Capillary Absorption tests without a common protocol. For cup tests, large inter-laboratory discrepancies still exist. However, with a stringent common protocol different laboratories achieved consistent results. For all properties a common protocol did not change the average results of all laboratories.
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Capillary Absorption of water and n decane by autoclaved aerated concrete
Cement and Concrete Research, 2008Co-Authors: Ioannis Ioannou, Andrea Hamilton, Christopher HallAbstract:Abstract An autoclaved aerated concrete was one of three construction materials used in the round-robin study of hygral properties carried out in the European Commission funded Heat, Air and Moisture Standards Development [HAMSTAD] project (Roels S et al., Journal of Thermal Envelope and Building Science 2004 27 307–325). The material has fine micron-scale matrix porosity generated by the packing of thin tobermorite 11A plates; and coarse mm-scale aeration pores arising from the foaming of the wet mix. We treat the material as having a strongly bimodal pore size distribution. Capillary Absorption does not obey simple t1/2 kinetics. We report here the results of liquid uptake tests using both water and n-decane to investigate the cause of the imbibition behaviour. The transport properties are modelled in a Sharp Front analysis as a parallel combination of Absorption into the coarse aeration pores and into the fine matrix pores. The aeration pores have weak Capillary suction and Absorption into these pores reaches Capillary rise equilibrium during the test. The Sharp Front model is applied here for the first time separately to subsets of the total porosity. The matrix sorptivity of the autoclaved aerated concrete studied (density 450 kg m− 3, porosity 0.82) is about 0.23 mm min− 1/2.
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A sharp wet front analysis of Capillary Absorption into n-layer composite
Journal of Physics D, 1996Co-Authors: Christopher Hall, Kim Green, William D. Hoff, Moira WilsonAbstract:New analytical results are found for the Capillary Absorption of a liquid into a porous (sorptive) composite solid composed of n parallel layers of arbitrary thickness and material properties. The analysis is based on the `sharp wet front' model (also known as the the Green - Ampt model) and the results are exact for that model. A contact impedance acting at the interface between layers is included. The physical approximations of the model are discussed. The cumulative Capillary Absorption as a function of time is expressed in terms of the sorptivity, permeability and porosity of the materials of the individual layers. Experimental data obtained on composite bars of gypsum plaster and plaster/sand materials agree well with model predictions, although they test the model over only a limited range of parameter values. For these composite specimens, there is no evidence of a hydraulic contact impedance at the interface between layers. An asymptotic expression is given for the effective sorptivity of an alternating composite ABAB....
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Effect of non-sorptive inclusions on Capillary Absorption by a porous material
Journal of Physics D, 1993Co-Authors: Christopher Hall, William D. Hoff, Moira WilsonAbstract:The Absorption of water into a porous material containing non-sorptive inclusions is analysed in terms of unsaturated flow theory. Expressions are obtained for the effect of inclusions on the permeability, the hydraulic conductivity, the hydraulic diffusivity and the sorptivity. New data on the water sorptivity S of gypsum plaster containing additions of sand ranging from 0 to 0.49 volume fraction alpha support the theoretical relation S'/S=1-1.25 alpha +0.26 alpha 2 approximately for the sorptivity. This result provides indirect confirmation of the expressions for the other quantities on which the sorptivity relation depends.
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Water anomaly in Capillary liquid Absorption by cement-based materials
Journal of Materials Science Letters, 1993Co-Authors: Christopher Hall, William D. Hoff, Moira Wilson, S C Taylor, Beom-gi Yoon, Hans-wolf Reinhardt, M Sosoro, Paul Meredith, Athene M. DonaldAbstract:The paper shows that the rate of Capillary Absorption of water in cement-based materials is anomalous when compared with that of other liquids.
Licheng Wang - One of the best experts on this subject based on the ideXlab platform.
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Experimental Study on the Influence of Curing Conditions on Capillary Absorption of Concrete
Proceedings of the 5th International Conference on the Durability of Concrete Structures, 2016Co-Authors: Licheng Wang, Jiuwen Bao, Bao-juan ChengAbstract:Both the hardening process and formation of microstructure of concrete are significantly influenced by the curing condition. The Capillary Absorption of concrete is closely related to the structure and distribution of the pores within the material. This paper presents an experimental study on the influence of four curing conditions, i.e., standard curing, natural curing, water curing, and sealed curing, on the Capillary Absorption of normal concrete. Compressive strength tests on the cylinder specimens that are core drilled from concrete slabs are carried out. The “pie” samples cut from three different locations along the height direction of cylinder specimens are then conducted to measure the ultrasonic pulse velocity (UPV) and porosity, which quantitatively characterize the internal state of concrete after 28 days initial curing. In order to realize the continuous observation of water Absorption testing, an improved gravimetrical test setup for measuring the sorptivity (the rate of water Absorption) of concrete is designed to investigate Capillary Absorption of the “pie” samples. The experimental results indicate that the curing condition has an important influence on compressive strength, ultrasonic pulse velocity, and porosity of concrete. The temperature and relative humidity are the key factors to ensure strength development during the curing procedure and to determine the internal pore structure and the compactness of concrete. For the same curing conditions, the cumulative water content, sorptivity, and porosity of concrete gradually decrease with the increase of distance from the surface, but the ultrasonic pulse velocity reverses.
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Capillary Absorption of unsaturated concrete subjected to sustained compressive loading
Proceedings of the Second International Conference on Performance-based and Life-cycle Structural Engineering (PLSE 2015), 2015Co-Authors: J. W. Bao, Licheng Wang, B. J. ChengAbstract:Water penetration into concrete is one of the main factors to cause the deterioration of structures and chloride-induced reinforcing steel corrosion. External sustained mechanical loadings can substantially change the internal pore-structure of concrete and then lead to microcracks, which play a critical role in the durability of concrete because of the provision of additional pathways for aggressive agents (such as chloride ions, sulfate, oxygen, carbon dioxide etc.) to ingress into concrete. This paper presents an experimental investigation into Capillary Absorption of unsaturated concrete subjected to sustained compressive loading. In order to realize the couple of loading and water Absorption process, the hollow cylinder specimens were loaded to different compressive loading levels, and simultaneously tested by an improved device for cumulative absorbed water measurement to conduct a series of water Absorption experiments. The focus of this paper is to analyze the experimental results and quantify the influence of external loading and load-induced microcracks on the water Absorption of concrete. According to unsaturated flow theory of concrete, the functional relationship with the stress level and sorptivity, which can characterize the tendency of concrete to absorb and transmit water by the Capillary mechanism, is reasonably proposed for analyzing the effect of different compressive loading levels on water transport properties. The experimental results indicated that with the increase of applied compressive stress, the rate of Capillary Absorption of load-damaged concrete initially decreases, and with a further increase in stress level, one markedly increases.
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Capillary Absorption of concrete after mechanical loading
Magazine of Concrete Research, 2014Co-Authors: Licheng WangAbstract:Microcracks, which are always present in concrete, play a critical role in the durability of concrete because they provide additional pathways for aggressive agents such as chlorides to penetrate into the material. A thorough understanding of the transport properties of cracked/damaged concrete is thus essential for predicting its long-term durability. In addition, for concrete in an unsaturated state, water acts as the main medium for the ingress of chloride ions into concrete. This paper presents an experimental investigation into the Capillary Absorption of concrete after being subjected to compressive or tensile loading. Sorptivity is chosen as a parameter to describe the rate of water penetrating into concrete since it can characterise the tendency of cementitious materials to absorb and transmit water by the Capillary mechanism. A series of water Absorption experiments were conducted on concrete samples after being subjected to uniaxial compressive or tensile loading. Three load levels were consider...
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Numerical Solutions for Capillary Absorption by Cementitious Materials
Applied Mechanics and Materials, 2011Co-Authors: Licheng WangAbstract:Capillary Absorption is essential to mass migration in cementitious materials. Based on previous studies, Capillary rise involving gravity effects is of much greater interest in porous building materials because equilibrium is attained at the wetting front when gravitational force balance the Capillary force. In this paper, two different solution forms, semi-analytical and numerical, are presented to account for the gravity effect for realistical prediction of water penetration process. The former is stable against small perturbation proved by Stepanyants [1]. The comparison of predicted results by the two methods confirms the reliability of the technique in estimating water transport.
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Mesoscale modeling of water penetration into concrete by Capillary Absorption
Ocean Engineering, 2011Co-Authors: Licheng Wang, Tamon UedaAbstract:Abstract Water penetration into concrete by Capillary Absorption plays a very important role in the ingress of contaminative substances when the structures are built in aggressive environments. In the present paper the lattice network model is proposed based on the unsaturated flow theory to predict the water penetration into concrete. On the mesocale level, concrete is treated as a three-phase composite. By means of the Voronoi diagram meshing strategy, the lattice network model of concrete with different types of lattice elements is developed. The corresponding transport properties are assigned to the lattice elements in the network falling in different phases. As a result, the lattice elements are idealized as conductive “pipes” in which uni-directional flow can be realized between the two nodes of the elements. Parameters in the lattice network model, such as the sorptivity and porosity of the mortar and the ITZs are quantitatively determined. With help of the approach, the water content distribution within a concrete sample after any elapsed time, especially the penetration depth of water frontier, can be easily predicted. The cumulative water Absorption calculated by the lattice network model is shown to be well agreed with the experimental results.
Ivan Anžel - One of the best experts on this subject based on the ideXlab platform.
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Capillary Absorption in concrete and the lucas washburn equation
Cement & Concrete Composites, 2010Co-Authors: Lucija Hanzic, Ladislav Kosec, Ivan AnželAbstract:Abstract Capillary Absorption kinetics of concrete–ethylene glycol system was studied with respect to concrete matrix porosity and liquid viscosity. Porosity of specimens was altered by air-entraining agents and superplasticizers. Liquid which doesn’t react with cement gel was chosen for the experiment in order to study the reasons for deviation from Lucas–Washburn equation observed in concrete–water system. Viscosity of ethylene glycol changes from ∼23 to 2 mPa s in the temperature range from 20 to 100 °C. The values of the Capillary coefficient were determined at 20, 60 and 100 °C using Neutron Radiography and were found to be in the range from ∼1.5 to 4.9 mm h −1/2 . The results show that the Lucas–Washburn equation in concrete–ethylene glycol system is valid only for ∼25 h, which indicates that swelling and rehydration of cement gel are not the main reasons for deviation observed in concrete–water system.
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Capillary Absorption in concrete and the Lucas–Washburn equation
Cement & Concrete Composites, 2009Co-Authors: Lucija Hanzic, Ladislav Kosec, Ivan AnželAbstract:Abstract Capillary Absorption kinetics of concrete–ethylene glycol system was studied with respect to concrete matrix porosity and liquid viscosity. Porosity of specimens was altered by air-entraining agents and superplasticizers. Liquid which doesn’t react with cement gel was chosen for the experiment in order to study the reasons for deviation from Lucas–Washburn equation observed in concrete–water system. Viscosity of ethylene glycol changes from ∼23 to 2 mPa s in the temperature range from 20 to 100 °C. The values of the Capillary coefficient were determined at 20, 60 and 100 °C using Neutron Radiography and were found to be in the range from ∼1.5 to 4.9 mm h −1/2 . The results show that the Lucas–Washburn equation in concrete–ethylene glycol system is valid only for ∼25 h, which indicates that swelling and rehydration of cement gel are not the main reasons for deviation observed in concrete–water system.
Biqin Dong - One of the best experts on this subject based on the ideXlab platform.
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Water distribution characteristics and research with Capillary Absorption for magnesium phosphate cement-coated cement pastes
Construction and Building Materials, 2020Co-Authors: Zhu Ding, Shuxian Hong, Yan-shuai Wang, Biqin DongAbstract:Abstract Magnesium phosphate cement (MPC) is a cementitious material formed by an acid-base reaction, which has usually developed as repair material for rehabilitation engineering. It also has the potential as coating materials for fire-resistance and for corrosion protection. In this study, the effect of magnesium phosphate cement as an inorganic coating on the water permeability of cement-based material is studied. X-ray computed tomography (XCT) was used to track the Capillary adsorption process of hardened cement non-destructively. The results showed that magnesium phosphate cement as the coating of cement-based materials has an excellent resistance to water penetration, and the quantitative and qualitative analysis of XCT water penetration was conducted. The microstructure analysis showed that the MPC matrix has much smaller porosity and pore sizes than the OPC matrix, and the interphase of OPC and MPC is dense and continuous, which may provide a remarkable effect on the Capillary Absorption blocking process. According to the Lucas-Washburn equation, a linear relationship between water Absorption height and the square root of time was established to verify the experimental results measured/calculated by XCT.
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Inverse modeling deduction of pore distribution in cement materials from Capillary Absorption features
Cement & Concrete Composites, 2020Co-Authors: Jianchao Zhang, Biqin Dong, Luping Tang, Chen Lin, Shuxian HongAbstract:Abstract The moisture transport performance of concrete is a vital factor that affects its durability, and this performance is closely related to the pore structures of the porous materials. In this study, water content profiles of Capillary Absorption were obtained using X-ray computed tomography technology. Based on the Lucas–Washburn equation, an inverse model was established to deduce the pore size distribution from the water content profiles. The feasibility of the proposed method was demonstrated using a size distribution model of the cement samples with different water-to-cement ratios. The obtained results were compared with the cumulative pore size distribution measured by mercury intrusion porosimetry, which indicated that the two methods exhibited satisfactory consistency.
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Water distribution characteristics in cement paste with Capillary Absorption
Construction and Building Materials, 2020Co-Authors: Shuxian Hong, Biqin Dong, Chen Lin, Wanqiong Yao, Bangwen Guo, Dongshuai Hou, Feng XingAbstract:Abstract Water penetration is important to the durability deterioration of concrete structures. This study provides X-ray computed tomography (XCT) to nondestructively trace the Capillary Absorption process in hardened cement and investigate the influence of water-cement (w/c) ratio. With our proposed data analysis procedure, the changes of water Absorption front position and the water content profile during the Absorption process can be obtained. The results show that the w/c ratio not only influences the Capillary coefficient and sorptivity, but also changes the absorbed water distribution. The obtained results are verified and further used to investigate the influence of the w/c ratio on the Capillary Absorption features.
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Visualized tracing of Capillary Absorption process in cementitious material based on X ray computed tomography
Cement & Concrete Composites, 2020Co-Authors: Shuxian Hong, Wanqiong Yao, Bangwen Guo, Dongshuai Hou, Shaofeng Qin, Yuxin Zhang, Wei Liu, Biqin DongAbstract:Abstract Moisture is one of the major deterioration factors of concrete. In this study, the Capillary Absorption process, which is one of the major transportation mechanism in cement paste, is non-destructively investigated by using X-ray computed tomography (XCT). A novel image processing procedure is proposed to correct the XCT image artifacts and calibrate the results of different measurements. The proposed image processing procedure allows for 3D visualization of the Absorption process and additional information can be obtained, including the height of the water Absorption front and the water content gradient.
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Water distribution modelling of Capillary Absorption in cementitious materials
Construction and Building Materials, 2019Co-Authors: Jianchao Zhang, Shuxian Hong, Biqin Dong, Luping Tang, Chen Lin, Zhichao Liu, Feng XingAbstract:Abstract In this paper, a novel Capillary Absorption model is proposed to investigate the Capillary Absorption process of cementitious materials. This model mainly consider the influence of tortuosity of the Capillary pores of cement paste, which is the key factor affecting the Capillary Absorption process. The proposed model is verified by the Capillary Absorption process of paste samples with different water/cement ratios. The Absorption height and water content profile of testing samples are measured by X-ray computed tomography. The results show that the proposed Capillary Absorption model that takes the tortuosity of Capillary pores into consideration is suitable for investigating the Capillary Absorption process of water in cementitious materials.
Shuxian Hong - One of the best experts on this subject based on the ideXlab platform.
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Water distribution characteristics and research with Capillary Absorption for magnesium phosphate cement-coated cement pastes
Construction and Building Materials, 2020Co-Authors: Zhu Ding, Shuxian Hong, Yan-shuai Wang, Biqin DongAbstract:Abstract Magnesium phosphate cement (MPC) is a cementitious material formed by an acid-base reaction, which has usually developed as repair material for rehabilitation engineering. It also has the potential as coating materials for fire-resistance and for corrosion protection. In this study, the effect of magnesium phosphate cement as an inorganic coating on the water permeability of cement-based material is studied. X-ray computed tomography (XCT) was used to track the Capillary adsorption process of hardened cement non-destructively. The results showed that magnesium phosphate cement as the coating of cement-based materials has an excellent resistance to water penetration, and the quantitative and qualitative analysis of XCT water penetration was conducted. The microstructure analysis showed that the MPC matrix has much smaller porosity and pore sizes than the OPC matrix, and the interphase of OPC and MPC is dense and continuous, which may provide a remarkable effect on the Capillary Absorption blocking process. According to the Lucas-Washburn equation, a linear relationship between water Absorption height and the square root of time was established to verify the experimental results measured/calculated by XCT.
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Inverse modeling deduction of pore distribution in cement materials from Capillary Absorption features
Cement & Concrete Composites, 2020Co-Authors: Jianchao Zhang, Biqin Dong, Luping Tang, Chen Lin, Shuxian HongAbstract:Abstract The moisture transport performance of concrete is a vital factor that affects its durability, and this performance is closely related to the pore structures of the porous materials. In this study, water content profiles of Capillary Absorption were obtained using X-ray computed tomography technology. Based on the Lucas–Washburn equation, an inverse model was established to deduce the pore size distribution from the water content profiles. The feasibility of the proposed method was demonstrated using a size distribution model of the cement samples with different water-to-cement ratios. The obtained results were compared with the cumulative pore size distribution measured by mercury intrusion porosimetry, which indicated that the two methods exhibited satisfactory consistency.
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Water distribution characteristics in cement paste with Capillary Absorption
Construction and Building Materials, 2020Co-Authors: Shuxian Hong, Biqin Dong, Chen Lin, Wanqiong Yao, Bangwen Guo, Dongshuai Hou, Feng XingAbstract:Abstract Water penetration is important to the durability deterioration of concrete structures. This study provides X-ray computed tomography (XCT) to nondestructively trace the Capillary Absorption process in hardened cement and investigate the influence of water-cement (w/c) ratio. With our proposed data analysis procedure, the changes of water Absorption front position and the water content profile during the Absorption process can be obtained. The results show that the w/c ratio not only influences the Capillary coefficient and sorptivity, but also changes the absorbed water distribution. The obtained results are verified and further used to investigate the influence of the w/c ratio on the Capillary Absorption features.
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Visualized tracing of Capillary Absorption process in cementitious material based on X ray computed tomography
Cement & Concrete Composites, 2020Co-Authors: Shuxian Hong, Wanqiong Yao, Bangwen Guo, Dongshuai Hou, Shaofeng Qin, Yuxin Zhang, Wei Liu, Biqin DongAbstract:Abstract Moisture is one of the major deterioration factors of concrete. In this study, the Capillary Absorption process, which is one of the major transportation mechanism in cement paste, is non-destructively investigated by using X-ray computed tomography (XCT). A novel image processing procedure is proposed to correct the XCT image artifacts and calibrate the results of different measurements. The proposed image processing procedure allows for 3D visualization of the Absorption process and additional information can be obtained, including the height of the water Absorption front and the water content gradient.
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Water distribution modelling of Capillary Absorption in cementitious materials
Construction and Building Materials, 2019Co-Authors: Jianchao Zhang, Shuxian Hong, Biqin Dong, Luping Tang, Chen Lin, Zhichao Liu, Feng XingAbstract:Abstract In this paper, a novel Capillary Absorption model is proposed to investigate the Capillary Absorption process of cementitious materials. This model mainly consider the influence of tortuosity of the Capillary pores of cement paste, which is the key factor affecting the Capillary Absorption process. The proposed model is verified by the Capillary Absorption process of paste samples with different water/cement ratios. The Absorption height and water content profile of testing samples are measured by X-ray computed tomography. The results show that the proposed Capillary Absorption model that takes the tortuosity of Capillary pores into consideration is suitable for investigating the Capillary Absorption process of water in cementitious materials.
