The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
En-hua Yang - One of the best experts on this subject based on the ideXlab platform.
-
quantitative characterization of anisotropic properties of the interfacial transition zone itz between microfiber and Cement paste
Cement and Concrete Research, 2019Co-Authors: En-hua YangAbstract:Abstract A new approach to characterize ITZ between microfiber and Cement Matrix is reported. Results show that microstructure of hydrated Cement paste is highly modified in the vicinity of microfibers, with higher porosity and less anhydrous Cement. ITZ can extend up to 100 μm from the interface into the Matrix. The larger extent of ITZ suggests that perturbation due to inclusion of microfibers to packing of Cement grains is severer than that due to inclusion of aggregates. Furthermore, ITZ between microfiber and Cement Matrix is highly heterogeneous along its axial direction. Existing ITZ analysis methods performed on 2-D cross-sectional plane intersecting with fiber axis thus can lead to errors and uncertainties. Mechanical properties of ITZ between microfiber and Cement Matrix are anisotropic. Stiffness and ductility of ITZ in the radial direction are 31% and 28% higher than that in the tangential direction, respectively.
-
Fatigue-induced in-situ strength deterioration of micro-polyvinyl alcohol (PVA) fiber in Cement Matrix
Cement and Concrete Composites, 2017Co-Authors: Jishen Qiu, Xin Ni Lim, En-hua YangAbstract:Abstract For soft fiber and brittle Matrix system such as polymeric fiber-reinforced Cementitious composites, the fiber strength deterioration dominates the performance of composites subject to fatigue loading. The fatigue-induced in-situ fiber strength deterioration in brittle Matrix, however, has rarely been studied. In this paper, fatigue-induced in-situ strength deterioration of micro-polyvinyl alcohol (PVA) fiber in Cement Matrix was experimentally investigated. The effects of fiber embedment, fiber inclination, and fiber surface treatment on the in-situ strength of micro-PVA fibers are reported. The results show that fiber embedment into Cement Matrix not only reduces the in-situ strength of fiber but also changes the fatigue stress-cycle (S-N) curve and failure mode of fiber. Fiber inclination further decreases the in-situ strength of embedded fiber due to local stress concentration of bent fibers. Oil-treatment on fiber surface can effectively delay fatigue-induced in-situ strength deterioration of micro-PVA fiber.
-
fatigue induced deterioration of the interface between micro polyvinyl alcohol pva fiber and Cement Matrix
Cement and Concrete Research, 2016Co-Authors: Jishen Qiu, Xin Ni Lim, En-hua YangAbstract:Abstract Quality of interfacial bond between fibers and Matrix determines the post-cracking behavior of fiber-reinforced composites. Fatigue-induced interface deterioration between fibers and Matrix has not been investigated systematically which prevents understanding of premature failure of fiber-reinforced composites subject to fatigue. This study experimentally investigated the deterioration mechanism of flexible fibers in brittle Matrix subject to fatigue load. Specifically, the effect of fatigue-induced deterioration of interface between micro-PVA fiber and Cement Matrix was studied through the single fiber fatigue pullout tests and the micro-structural deterioration mechanism of the fiber-Matrix interface under fatigue load was unveiled. It was found that fatigue load leads to fiber debonding which can be described by an empirical relation similar to the Paris' law. Fatigue-induced interface hardening can occur during fiber debonding stage as well as fiber slippage stage. Oil-treatment on surface of micro-PVA fiber was demonstrated as a mean to mitigate such fatigue-induced interface hardening.
Deborah D.l. Chung - One of the best experts on this subject based on the ideXlab platform.
-
comparative evaluation of Cement Matrix composites with distributed versus networked exfoliated graphite
Carbon, 2013Co-Authors: Pohsiu Chen, Deborah D.l. ChungAbstract:Abstract Cement with distributed exfoliated graphite (isotropic) is made by incorporating exfoliated graphite in the wet Cement mix; Cement with networked exfoliated graphite (anisotropic) is made by compressing a dry mixture of exfoliated graphite and Cement particles, followed by curing with water. The graphite layers in the latter are preferentially oriented in the plane perpendicular to the compression direction; the in-plane electrical resistivity is much lower than the out-of-plane resistivity and the loss tangent, storage modulus and loss modulus are much higher for out-of-plane flexure than in-plane flexure. The latter gives higher density, lower electrical resistivity, higher compressive strength and superior vibration damping than the former. Compared to plain Cement, it gives higher density and higher compressive strength. In contrast, Cement with distributed exfoliated graphite gives lower density and lower compressive strength than plain Cement, though it gives lower resistivity and superior damping. Distributed exfoliated graphite is detrimental when silica fume is present. The high damping of Cement with networked exfoliated graphite is attributed to the effective sandwiching of the network ligaments by the Cement Matrix (constrained-layer damping); the high density and compressive strength are attributed to the low porosity caused by the compression of the exfoliated graphite during composite fabrication.
-
battery in the form of a Cement Matrix composite
Cement & Concrete Composites, 2010Co-Authors: Qiaoli Meng, Deborah D.l. ChungAbstract:Abstract Reported here is a battery in the form of a Cement-Matrix composite, with Cement paste as the Matrix, the pore solution in Cement as the electrolyte, zinc particles dispersed in the Matrix as the anode, manganese dioxide particles dispersed in the Matrix as the cathode, and carbon black dispersed in the Matrix as the conductive additive in both anode and cathode regions. The electrolyte is continuous throughout the battery, which consists of successively cast and co-cured anode, electrolyte and cathode layers. The anode layer (4 mm thick) comprises Cement and zinc particles. The cathode layer (8 mm thick) comprises Cement and manganese dioxide particles. The electrolyte layer (2 mm thick) is Cement with an embedded piece of tissue paper for drying shrinkage control. The battery attained open-circuit voltage up to 0.72 V, current up to 120 μA (current density up to 3.8 μA/cm2), power output up to 1.4 μW/cm2, capacity up to 0.2 mA h, and fraction of zinc consumed up to 5 × 10−5.
-
unprecedented vibration damping with high values of loss modulus and loss tangent exhibited by Cement Matrix graphite network composite
Carbon, 2010Co-Authors: Sivaraja Muthusamy, Shoukai Wang, Deborah D.l. ChungAbstract:Abstract This paper reports a material with unprecedented vibration damping ability, as shown by high values of both the loss tangent (vibration amplitude decay rate) and the loss modulus (energy dissipation ability, equal to the product of the storage modulus and the loss tangent) under flexure at 0.2 Hz at room temperature. The loss modulus (7.5 GPa) exceeds that of any previously reported material, including the best metal-based material, which suffers from a low loss tangent. The loss tangent (0.81) is comparable to or exceeds that of any previously reported material, including rubber, which suffers from a low loss modulus. This material is a Cement–Matrix graphite network composite containing 8 vol.% graphite and made by compressing a mixture of Cement particles and exfoliated graphite, which binds by mechanical interlocking, followed by curing in water. The graphite network structure is supported by microscopy and the low electrical resistivity of the composite (0.04 Ω cm perpendicular to the compression direction and 0.5 Ω cm in the compression direction). The composite is much more conductive than the most conductive Cement–Matrix composite containing a conductive admixture. The high loss tangent is attributed to the graphite network, while the high storage modulus is attributed to the Cement Matrix.
-
Cement-Matrix structural nanocomposites
Metals and Materials International, 2004Co-Authors: Deborah D.l. ChungAbstract:This paper reviews Cement-Matrix structural nanocomposites, including those with particulate and fibrous reinforCements. Silica fume is valuable for improving numerous mechanical properties, in addition to enhancing the freeze-thaw durability, the vibration damping capacity, the abrasion resistance, the bond strength with steel rebars, the chemical attack resistance and the corrosion resistance of steel rebars. Furthermore, silica fume decreases the alkali-silica reactivity, the drying shrinkage, permeability, creep rate and thermal expansion. On the other hand, carbon nanofiber is not attractive, as it fails to compete with conventional discontinuous carbon fiber as a reinforCement.
-
Functional properties of Cement-Matrix composites
Journal of Materials Science, 2001Co-Authors: Deborah D.l. ChungAbstract:The functional properties of Cement-Matrix composites are reviewed. The functions include strain sensing, damage sensing, temperature sensing, thermal control, vibration reduction and radio wave reflection. The functions are rendered by the use of admixtures, such as short carbon fibers, short steel fibers and silica fume.
Gengying Li - One of the best experts on this subject based on the ideXlab platform.
-
pressure sensitive properties and microstructure of carbon nanotube reinforced Cement composites
Cement & Concrete Composites, 2007Co-Authors: Gengying Li, Pei Ming Wang, Xiaohua ZhaoAbstract:Abstract Carbon nanotubes (CNTs) treated by using a mixed solution of H2SO4 and HNO3 were uniformly dispersed into Cement paste by means of ultrasonic energy. Electrical resistivity and pressure-sensitive properties under cyclic compressive loading of this composite were analyzed and compared to that of untreated-CNT reinforced Cement paste. Results show that the addition of treated or untreated CNTs to Cement paste leads to a notable decrease in volume electrical resistivity and a distinct enhanCement in compressive sensitivity. The microstructures of these Cement composites were analyzed by using scanning electron microscope. The microscopic observation reveals that both treated and untreated CNTs were dispersed homogenously in the Cement Matrix. For untreated CNT-reinforced Cement composites, the CNTs with glossy surface were zigzag and cling to Cement Matrix; the bridging of cracks and a well three-dimensional meshwork were also observed. For treated-CNT reinforced Cement composites, the surface of CNTs was covered by C–S–H, which leads to a higher mechanical strength. The contact points of the treated-CNTs in composites were much fewer than that of the untreated-CNTs in Cement Matrix composites, which leads to a higher compressive sensitive properties and a lower electrical conductivity.
-
mechanical behavior and microstructure of Cement composites incorporating surface treated multi walled carbon nanotubes
Carbon, 2005Co-Authors: Gengying Li, Pei Ming Wang, Xiaohua ZhaoAbstract:Abstract Multi-walled carbon nanotubes after modified by using a H2SO4 and HNO3 mixture solution were added to Cement Matrix composites. The mechanical properties of the newly formulated composites were analyzed, and the results show that the treated nanotubes can improve the flexural strength, compressive strength, and failure strain of Cement Matrix composites. The porosity and pore size distribution of the composites were determined by using Mercury intrusion porosimetry, and it is observed that the addition of carbon nanotubes can fine the pore size distribution and decrease porosity. The phase composition was characterized with Fourier transform infrared spectroscopy. It is found that there are interfacial interactions between carbon nanotubes and the hydrations (such as C–S–H and calcium hydroxide) of Cement, which will produce a high bonding strength between the reinforCement and Cement Matrix. The mineralogy and microstructure were analyzed by using scanning electron microscope. It is shown that carbon nanotubes act as bridges across cracks and voids, which guarantees the load-transfer in case of tension.
Xiaohua Zhao - One of the best experts on this subject based on the ideXlab platform.
-
pressure sensitive properties and microstructure of carbon nanotube reinforced Cement composites
Cement & Concrete Composites, 2007Co-Authors: Gengying Li, Pei Ming Wang, Xiaohua ZhaoAbstract:Abstract Carbon nanotubes (CNTs) treated by using a mixed solution of H2SO4 and HNO3 were uniformly dispersed into Cement paste by means of ultrasonic energy. Electrical resistivity and pressure-sensitive properties under cyclic compressive loading of this composite were analyzed and compared to that of untreated-CNT reinforced Cement paste. Results show that the addition of treated or untreated CNTs to Cement paste leads to a notable decrease in volume electrical resistivity and a distinct enhanCement in compressive sensitivity. The microstructures of these Cement composites were analyzed by using scanning electron microscope. The microscopic observation reveals that both treated and untreated CNTs were dispersed homogenously in the Cement Matrix. For untreated CNT-reinforced Cement composites, the CNTs with glossy surface were zigzag and cling to Cement Matrix; the bridging of cracks and a well three-dimensional meshwork were also observed. For treated-CNT reinforced Cement composites, the surface of CNTs was covered by C–S–H, which leads to a higher mechanical strength. The contact points of the treated-CNTs in composites were much fewer than that of the untreated-CNTs in Cement Matrix composites, which leads to a higher compressive sensitive properties and a lower electrical conductivity.
-
mechanical behavior and microstructure of Cement composites incorporating surface treated multi walled carbon nanotubes
Carbon, 2005Co-Authors: Gengying Li, Pei Ming Wang, Xiaohua ZhaoAbstract:Abstract Multi-walled carbon nanotubes after modified by using a H2SO4 and HNO3 mixture solution were added to Cement Matrix composites. The mechanical properties of the newly formulated composites were analyzed, and the results show that the treated nanotubes can improve the flexural strength, compressive strength, and failure strain of Cement Matrix composites. The porosity and pore size distribution of the composites were determined by using Mercury intrusion porosimetry, and it is observed that the addition of carbon nanotubes can fine the pore size distribution and decrease porosity. The phase composition was characterized with Fourier transform infrared spectroscopy. It is found that there are interfacial interactions between carbon nanotubes and the hydrations (such as C–S–H and calcium hydroxide) of Cement, which will produce a high bonding strength between the reinforCement and Cement Matrix. The mineralogy and microstructure were analyzed by using scanning electron microscope. It is shown that carbon nanotubes act as bridges across cracks and voids, which guarantees the load-transfer in case of tension.
Xueqing Qiu - One of the best experts on this subject based on the ideXlab platform.
-
The feasibility of synthetic surfactant as an air entraining agent for the Cement Matrix
Construction and Building Materials, 2008Co-Authors: Xinping Ouyang, Yongxia Guo, Xueqing QiuAbstract:Abstract The effect of the synthetic surfactant combining 50 wt% of polyoxyethylene nonylphenolether (TX-10) with 50 wt% of sodium dodecyl sulfate (K12) on the compressive strength of the Cement mortar was investigated in order to explore the feasibility of the synthetic surfactant as an air entraining agent (AEA). The fluidity of the mortar, the process of the Cement hydration and the pore size distribution of the hardened mortar were determined for the purpose of analyzing the effect of the AEA on the strength of the hardened mortar. It is found that the suitable dosage of the synthetic surfactant based AEA incorporated with modified lignosulfonate superplasticizer can improve the compressive strength of the Cement Matrix. The AEA contributes to a better dispersion of Cement particles in water, and hence the Cement mortar can generate more nuclei and form finer ettringite needles during the Cement hydration, resulting in an increase in porosity percentages with small-size pore and a decrease in those with large-size pore. Therefore, the synthetic AEA shows a compressive strength enhanCement unless its dosage is excessive.