The Experts below are selected from a list of 5730 Experts worldwide ranked by ideXlab platform
Enhua Yang - One of the best experts on this subject based on the ideXlab platform.
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Strain hardening ultra high performance concrete shuhpc incorporating cnf coated polyethylene fibers
Cement and Concrete Research, 2017Co-Authors: Shan He, Junxia Li, Enhua YangAbstract:Abstract A novel idea of using carbon nanofibers (CNFs) to strengthen the interface transition zone (ITZ) and to enhance the interface frictional bond strength between polyethylene (PE) fibers and cement-based matrix was proposed and realized by coating CNFs on surface of PE fibers through hydrophobic interactions. A Strain hardening ultra-high performance concrete (SHUHPC) incorporating such CNF-coated PE fibers was developed. The resulting CNF-SHUHPC has a compressive strength over 150 MPa and exhibits 15% enhancement in Tensile strength, 20% improvement in Tensile Strain Capacity, and reduced cracking spacing. Single fiber pullout tests showed the interface frictional bond strength of the CNF-coated PE fiber was increased by 22%, which is attributed to CNFs strengthening the ITZ by filling nano-pores and bridging nano-cracks resulting in denser microstructure and higher crack resistance against fiber pullout as revealed by the micrographs. The increased interface frictional bond strength leads to higher Tensile strength and increased Tensile Strain Capacity as predicted by the micromechanical model.
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micromechanics based investigation of a sustainable ambient temperature cured one part Strain hardening geopolymer composite
Construction and Building Materials, 2017Co-Authors: Behzad Nematollahi, Jishen Qiu, Jay G. Sanjayan, Enhua YangAbstract:Abstract Geopolymer composite research is aimed to make sustainable alternatives to Portland cement-based composites. However, the two main obstacles for commercialization are the use of large quantities of user-hostile liquid activators and heat curing. This study is aimed to overcome these obstacles by developing an ambient temperature cured “one-part” Strain hardening geopolymer composite (SHGC). The developed composite as a “dry mix” uses a small amount of solid activator and eliminates the necessity for heat curing. The quantitative influences of curing condition and type of slag on the composite Tensile performance were evaluated. The developed composite demonstrated strong Strain hardening behavior comparable to typical Strain hardening cementitious composite (SHCC) with high Tensile strength of 4.6 MPa and very high Tensile Strain Capacity of 4.2%. A micromechanics-based investigation was performed to explain the experimentally observed macroscopic high Tensile ductility of the developed composite. The investigation involved determination of the matrix fracture properties and the fiber-matrix interface properties using fracture toughness tests and single-fiber pullout tests, respectively. The crack-bridging relation of the developed composite, computed via a micromechanics-based model, satisfied the necessary strength and energy-based conditions of steady-state flat crack propagation, which result in sequential development of multiple cracking. The material sustainability evaluation verified that the developed ambient temperature cured one-part SHGC is a promising sustainable alternative to typical SHCC offering 76% less carbon emissions and 36% less energy consumption. This research presents the rational basis for design of such cement-less composites with both high Tensile ductility and high material sustainability.
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Microscale investigation of fiber-matrix interface properties of Strain-hardening geopolymer composite
Ceramics International, 2017Co-Authors: Behzad Nematollahi, Enhua Yang, Jishen Qiu, Jay G. SanjayanAbstract:Abstract This study reports the microscale investigation of a short fiber-reinforced fly ash-based Strain-hardening geopolymer composite (SHGC), which possesses high Tensile strength (4.7 MPa) and very high Tensile Strain Capacity (4.3%). The investigation involved determination of the quantitative influences of the type of activator, water to geopolymer solids ratio and fiber surface oil coating on the microscale fiber-matrix interface properties using single-fiber pullout tests. The effects of the measured interface properties on the crack bridging σ(δ) relation of the composites were investigated using a micromechanics-based model to explain the experimentally observed macroscopic Tensile ductility of the composites. The computed σ(δ) relation of fly ash-based SHGCs satisfied the necessary micromechanics-based conditions of steady-state flat crack propagation, which result in Strain-hardening behavior. This research provides an in-depth understanding of fundamental fiber-matrix interaction properties and mechanisms, and their consequent effects on crack-bridging and Tensile performance of the developed fly ash-based SHGCs. This understanding presents the rational basis for design of such cement-less composites.
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Strain rate effects on the Tensile behavior of Strain hardening cementitious composites
Construction and Building Materials, 2014Co-Authors: Enhua YangAbstract:Abstract This paper investigated the Strain-rate effects on the Tensile properties of Strain-hardening cementitious composite (SHCC) and explored the underlying micromechanical sources responsible for the rate dependence. Experimental studies were carried out to reveal rate dependence in component phases, i.e. fiber, matrix, and fiber/matrix interface. A dynamic micromechanical model relating material microstructure to SHCC Tensile Strain-hardening under high loading rates was developed. It was found fiber stiffness, fiber strength, matrix toughness and fiber/matrix interface chemical bond strength were loading rate sensitive and they increase with loading rates in a polyvinyl alcohol fiber-reinforced SHCC (PVA-SHCC) system. These changes in component properties result in the reduction of Tensile Strain Capacity of PVA-SHCC as the Strain-rate increases from 10−5 to 10−1 s−1.
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autogenous healing of engineered cementitious composites under wet dry cycles
Cement and Concrete Research, 2009Co-Authors: Yingzi Yang, Michael D Lepech, Enhua YangAbstract:Abstract Self-healing of Engineered Cementitious Composites (ECC) subjected to two different cyclic wetting and drying regimes was investigated in this paper. To quantify self-healing, resonant frequency measurements were conducted throughout wetting–drying cycles followed by uniaxial Tensile testing of self-healing ECC specimens. Through self-healing, crack-damaged ECC recovered 76% to 100% of its initial resonant frequency value and attained a distinct rebound in stiffness. Even for specimens deliberately pre-damaged with microcracks by loading up to 3% Tensile Strain, the Tensile Strain Capacity after self-healing recovered close to 100% that of virgin specimens without any preloading. Also, the effects of temperature during wetting–drying cycles led to an increase in the ultimate strength but a slight decrease in the Tensile Strain Capacity of rehealed pre-damaged specimens. This paper describes the experimental investigations and presents the data that confirm reasonably robust autogenous healing of ECC in commonly encountered environments for many types of infrastructure.
Jeong Il Choi - One of the best experts on this subject based on the ideXlab platform.
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Control of Tensile Behavior of Ultra-High Performance Concrete Through Artificial Flaws and Fiber Hybridization
International Journal of Concrete Structures and Materials, 2016Co-Authors: Su-tae Kang, Jeong Il Choi, Burak FelekoğluAbstract:Ultra-high performance concrete (UHPC) is one of the most promising construction materials because it exhibits high performance, such as through high strength, high durability, and proper rheological properties. However, it has low Tensile ductility compared with other normal strength grade high ductile fiber-reinforced cementitious composites. This paper presents an experimental study on the Tensile behavior, including Tensile ductility and crack patterns, of UHPC reinforced by hybrid steel and polyethylene fibers and incorporating plastic beads which have a very weak bond with a cementitious matrix. These beads behave as an artificial flaw under Tensile loading. A series of experiments including density, compressive strength, and uniaxial tension tests were performed. Test results showed that the Tensile behavior including Tensile Strain Capacity and cracking pattern of UHPC investigated in this study can be controlled by fiber hybridization and artificial flaws.
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hybrid effects of steel fiber and microfiber on the Tensile behavior of ultra high performance concrete
Composite Structures, 2016Co-Authors: Su-tae Kang, Jeong Il ChoiAbstract:Abstract Ultra-high performance concrete (UHPC) has ultra-high material performance including high strength and high flowability. However, its Tensile Strain Capacity is generally lower than that of high ductile cementitious composite. This study experimentally investigated the effect of hybrid combinations of straight 0.2 mm diameter steel fiber and various microfibers on the mechanical properties of UHPC. Four types of hybrid fiber reinforced UHPCs including steel, basalt fibers, polyvinyl-alcohol, and polyethylene fibers were designed and then compressive strength, density, and Tensile behavior were investigated. Test results showed that combining a synthetic fiber with high strength, such as PE fiber, and steel fiber can improve the Tensile behavior of UHPC and basalt fiber was effective for improving the Tensile strength of UHPC.
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composite properties of high strength polyethylene fiber reinforced cement and cementless composites
Composite Structures, 2016Co-Authors: Jeong Il Choi, Keumil Song, Jinkyu Song, Bang Yeon LeeAbstract:Abstract This paper presents an experimental study of the composite properties of cement based- and alkali-activated ground-granulated blast furnace slag (GGBS) based composites reinforced by high-strength polyethylene fibers and a discussion of the different behaviors of the two types of binder-based composites. A series of experiments, including those to test the density, compression, and uniaxial tension, was performed to characterize the mechanical properties of the composite. The test results indicated that an alkali-activated GGBS composite shows a higher Tensile Strain Capacity with smaller crack widths and crack spacings than a cement-based composite, although the alkali-activated GGBS composite showed lower compressive and lower Tensile strength than the cement-based composite with the same water-to-binder ratio. It was also observed that the alkali-activated GGBS-based composite has higher ratio of the Tensile strength to the compressive strength than the cement-based composite.
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Ultra-high-ductile behavior of a polyethylene fiber-reinforced alkali-activated slag-based composite
Cement and Concrete Composites, 2016Co-Authors: Jeong Il Choi, Bang Yeon Lee, Ravi Ranade, Yun LeeAbstract:Abstract This paper presents an experimental study of the meso-level composite properties of an ultra-high-ductile polyethylene-fiber-reinforced alkali-activated slag-based composite. Four mixtures with 1.75 vol% of polyethylene fibers were prepared with varying water-to-binder ratio. The viscosity of the matrix was controlled to ensure a uniform fiber dispersion. A series of experiments, including density, compression, and uniaxial tension tests, was performed to characterize the mechanical properties of the composite. The test results showed that the average Tensile strength to compressive strength ratio of the composites was 19.8%, nearly double that of normal concrete, and the average crack width was 101 μm. It was also demonstrated that Tensile Strain Capacity and Tensile strength of up to 7.50% and 13.06 MPa, respectively, can be attained when using the proposed polyethylene-fiber-reinforced alkali-activated slag-based composites.
Ravi Ranade - One of the best experts on this subject based on the ideXlab platform.
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significance of the particle size distribution modulus for Strain hardening ultra high performance concrete sh uhpc matrix design
Construction and Building Materials, 2020Co-Authors: Ketan Ragalwar, William F Heard, Brett A Williams, Ravi RanadeAbstract:Abstract The distribution modulus, q, of the composite particle size distribution is a key parameter in the particle packing models that are typically used to achieve dense particle packing in ultra-high performance concretes (UHPC). While there are a few studies on the influence of q on the compressive strength of a UHPC in the literature, the effects of q on matrix fracture toughness, workability, and plastic viscosity have not been investigated. These properties are highly important for the micromechanics-based design of Strain-hardening UHPC (SH-UHPC) that possess significant uniaxial Tensile Strain Capacity. In this study, the central composite design (CCD) of experiments along with the modified Andreasen and Anderson (A&A) particle packing model were used to investigate the effects of q on the aforementioned matrix properties of SH-UHPC. Along with q, the effects of the type and content of the supplementary cementitious material (SCM) and water/cementitious (w/cm) material weight ratio on the matrix properties were also investigated. A second-order regression model was used to fit the results and identify important trends. Significant effects of q on the matrix properties were observed, mainly due to the influence of q on the particle packing and the aggregate/cementitious paste volumetric ratio. It was concluded that the value of q should be chosen based on the ingredients to achieve target rheological and mechanical properties of the SH-UHPC matrix. The knowledge developed in this study is vital for developing a rational design methodology for SH-UHPC class of materials.
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influence of high temperatures on the residual mechanical properties of a hybrid fiber reinforced Strain hardening cementitious composite
Construction and Building Materials, 2019Co-Authors: Alok A Deshpande, Dhanendra Kumar, Ravi RanadeAbstract:Abstract Recent studies have shown improved mechanical performance of Fiber-Reinforced Concretes (FRC) compared to conventional concrete at high temperatures. While polymer fibers in FRC improve the compressive behavior by providing pathways for moisture to escape through melting of fibers at high temperatures, steel fibers in FRC improve the Tensile behavior through crack-bridging at high temperatures. The goal of this research is to investigate the influence of utilizing both polymer and steel fibers in a single FRC for improving compressive and Tensile properties at high temperatures, simultaneously. For this purpose, a Polyvinyl Alcohol (PVA)-steel Hybrid Fiber-Reinforced Strain Hardening Cementitious Composite (HFR-SHCC) was developed. SHCC is a special class of FRC with Strain-hardening behavior under direct uniaxial tension. The residual compressive and Tensile properties of HFR-SHCC after being subjected to temperatures of up to 800 °C were experimentally determined. Additional FRCs, including a conventional SHCC with only PVA fibers and a fiber-reinforced concrete with only steel fibers (steel FRC), as well as conventional concretes of two different compressive strengths were tested with the same protocol for a comprehensive comparison. The HFR-SHCC shows clear improvement over conventional SHCC, steel FRC and conventional concretes in terms of residual Tensile strength after exposure to high temperatures, while simultaneously retaining the benefits of conventional SHCC, which include high Tensile Strain Capacity and microscopic crack widths at normal temperatures and improved retention of compressive strength after exposure to high temperature.
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Ultra-high-ductile behavior of a polyethylene fiber-reinforced alkali-activated slag-based composite
Cement and Concrete Composites, 2016Co-Authors: Jeong Il Choi, Bang Yeon Lee, Ravi Ranade, Yun LeeAbstract:Abstract This paper presents an experimental study of the meso-level composite properties of an ultra-high-ductile polyethylene-fiber-reinforced alkali-activated slag-based composite. Four mixtures with 1.75 vol% of polyethylene fibers were prepared with varying water-to-binder ratio. The viscosity of the matrix was controlled to ensure a uniform fiber dispersion. A series of experiments, including density, compression, and uniaxial tension tests, was performed to characterize the mechanical properties of the composite. The test results showed that the average Tensile strength to compressive strength ratio of the composites was 19.8%, nearly double that of normal concrete, and the average crack width was 101 μm. It was also demonstrated that Tensile Strain Capacity and Tensile strength of up to 7.50% and 13.06 MPa, respectively, can be attained when using the proposed polyethylene-fiber-reinforced alkali-activated slag-based composites.
Victor C Li - One of the best experts on this subject based on the ideXlab platform.
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development of reactive mgo based engineered cementitious composite ecc through accelerated carbonation curing
Construction and Building Materials, 2018Co-Authors: Haoliang Wu, Brian R Ellis, Duo Zhang, Victor C LiAbstract:Abstract The use of reactive magnesium oxide (MgO) is widely recognized in carbonated concrete formulations associated with permanent sequestration of CO2. Engineered Cementitious Composite (ECC) is an advanced fiber reinforced cement-based composite with high Tensile ductility and intrinsically tight crack width. In this paper, we investigate an alternative binary binding system for ECC: reactive MgO and fly ash cured with an accelerated carbonation process. Compressive strength, density, carbonation depth, Tensile performance and crack pattern of the carbonated reactive MgO-based ECC were investigated at various curing ages. In addition, the CO2 uptake and materials sustainability, in terms of energy consumption, net CO2 emission and cost of the newly developed ECC were assessed. The objective of this research is to further advance the application of reactive MgO and utilization of CO2 in the construction industry through novel ECC material. It was observed that carbonation curing densifies the binding system, thus leading to an increase in both compressive and first cracking Tensile strengths of ECC. The Tensile Strain Capacity of the carbonated reactive MgO-based ECC achieved up to 6% with an average crack width below 60 μm after 1-day carbonation. Compared to conventional ECC (M45) and concrete, the 1-day carbonated reactive MgO-based ECC could reduce the net CO2 emission by 65% and 45%, respectively. It is concluded that environmental and technical benefits could be simultaneously achieved for the 1-day carbonated reactive MgO-based ECC incorporated with 50% fly ash. The findings of this research shed light on further applications of reactive MgO cement in the precast industry.
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improved fiber distribution and mechanical properties of engineered cementitious composites by adjusting the mixing sequence
Cement & Concrete Composites, 2012Co-Authors: Jian Zhou, Shunzhi Qian, Klaas Breugel, Guang Ye, O Copuroglu, Victor C LiAbstract:Abstract Engineered cementitious composites (ECC) is a class of ultra ductile fiber reinforced cementitious composites, characterized by high ductility and tight crack width control. The polyvinyl alcohol (PVA) fiber with a diameter of 39 μm and a length of 6–12 mm is often used. Unlike plain concrete and normal fiber reinforced concrete, ECC shows a Strain-hardening behavior under Tensile load. Apart from the mix design, the fiber distribution is another crucial factor for the mechanical properties of ECC, especially the ductility. In order to obtain a good fiber distribution, the plastic viscosity of the ECC mortar before adding fibers needs to be controlled, for example, by adjusting water-to-powder ratio or chemical admixtures. However, such adjustments have some limitations and may result in poor mechanical properties of ECC. This research explores an innovative approach to improve the fiber distribution by adjusting the mixing sequence. With the standard mixing sequence, fibers are added after all solid and liquid materials are mixed. The undesirable plastic viscosity before the fiber addition may cause poor fiber distribution and results in poor hardened properties. With the adjusted mixing sequence, the mix of solid materials with the liquid material is divided into two steps and the addition of fibers is between the two steps. In this paper, the influence of different water mixing sequences is investigated by comparing the experimental results of the uniaxial Tensile test and the fiber distribution analysis. Compared with the standard mixing sequence, the adjusted mixing sequence increases the Tensile Strain Capacity and ultimate Tensile strength of ECC and improves the fiber distribution. This concept is further applied in the development of ECC with high volume of sand.
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simplified inverse method for determining the Tensile Strain Capacity of Strain hardening cementitious composites
Journal of Advanced Concrete Technology, 2007Co-Authors: Shunzhi Qian, Victor C LiAbstract:As emerging advanced construction materials, Strain hardening cementitious composites (SHCCs) have seen increasing field applications recently to take advantage of its unique Tensile Strain hardening behavior, yet existing uniaxial Tensile tests are relatively complicated and sometime difficult to implement, particularly for quality control purpose in field applications. This paper presents a new simple inverse method for quality control of Tensile Strain Capacity by conducting beam bending test. It is shown through a theoretical model that the beam deflection from a flexural test can be linearly related to Tensile Strain Capacity. A master curve relating this easily measured structural element property to material Tensile Strain Capacity is constructed from parametric studies of a wide range of material Tensile and compressive properties. This proposed method (UM method) has been validated with uniaxial Tensile test results with reasonable agreement. In addition, this proposed method is also compared with the Japan Concrete Institute (JCI) method. Comparable accuracy is found, yet the present method is characterized with much simpler experiment setup requirement and data interpretation procedure. Therefore, it is expected that this proposed method can greatly simplify the quality control of SHCCs both in execution and interpretation phases, contributing to the wider acceptance of this type of new material in field applications.
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high performance fiber reinforced cementitious composites as durable material for concrete structure repair
2004Co-Authors: Victor C LiAbstract:This paper addresses the property requirements of repair materials for high durability performance for concrete structure repair. It is proposed that the high Tensile Strain Capacity of High Performance Fiber Reinforced Cementitious Composites (HPFRCC) makes such materials particularly suitable for repair applications, provided that the fresh properties are also adaptable to those required in placement techniques in typical repair applications. A specific version of HPFRCC, known as Engineered Cementitious Composites (ECC), is described. It is demonstrated that the fresh and hardened properties of ECC meet many of the requirements for durable repair performance. Recent experience in the use of this material in a bridge deck patch repair is highlighted. The origin of this article is a summary of a keynote lecture with the same title given at the Conference on Fiber Composites, High-Performance Concretes and Smart Materials, Chennai, India, Jan., 2004. It is only slightly updated here.
Yichao Wang - One of the best experts on this subject based on the ideXlab platform.
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mechanical properties of high ductile magnesium oxychloride cement based composites after water soaking
Cement & Concrete Composites, 2019Co-Authors: Yichao Wang, Jiangtao Yu, Kequan YuAbstract:Abstract Applications of magnesium oxychloride cement-based concrete in civil engineering are limited due to material's poor water resistance and inherent brittleness. For improvement, a new kind of material, magnesium oxychloride cement-based engineered cementitious composite (MOC-ECC), was developed. This paper introduces the effects of fly ash and polyethylene fibers incorporations on the fluidity, Tensile behavior and compressive properties of MOC-ECC. The test results indicated that MOC-ECC exhibits outstanding Strain hardening and multi-cracking characteristics with Tensile Strain Capacity up to 8% and Tensile strength over 7 MPa. More importantly, to explore the combined influences of fly ash and polyethylene fiber on the water resistance of MOC-ECC, XRD and SEM were used to analyze the variations of chemical composition and microstructure, and three-point bending test and single crack tension test were conducted to obtain the fracture toughness and fiber bridging Capacity, respectively. An explanation to the mechanisms of the enhanced mechanical property and water resistance is presented at microscopic and mesoscopic scales.
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Using Green Supplementary Materials to Achieve More Ductile ECC
MDPI AG, 2019Co-Authors: Yichao Wang, Zhigang Zhang, Jianzhuang XiaoAbstract:To improve the greenness and deformability of engineered cementitious composites (ECC), recycled powder (RP) from construction and demolition waste with an average size of 45 μm and crumb rubber (CR) of two particle sizes (40CR and 80CR) were used as supplements in the mix. In the present study, fly ash and silica sand used in ECC were replaced by RP (50% and 100% by weight) and CR (13% and 30% by weight), respectively. The tension test and compression test demonstrated that RP and CR incorporation has a positive effect on the deformability of ECC, especially on the Tensile Strain Capacity. The highest Tensile Strain Capacity was up to 12%, which is almost 3 times that of the average ECC. The fiber bridging Capacity obtained from a single crack tension test and the matrix fracture toughness obtained from 3-point bending were used to analyze the influence of RP and CR at the meso-scale. It is indicated that the replacement of sand by CR lowers the matrix fracture toughness without decreasing the fiber bridging Capacity. Accordingly, an explanation was achieved for the exceeding deformability of ECC incorporated with RP and CR based on the pseudo-Strain hardening (PSH) index
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feasibility of using ultra high ductility cementitious composites for concrete structures without steel rebar
Engineering Structures, 2018Co-Authors: Jianzhuang Xiao, Yichao WangAbstract:Abstract To verify the feasibility of using the ultra-high ductility cementitious composites (UHDCC) for construction without steel reinforcement, the mechanical properties of UHDCC was experimentally tested at material, structural member and structure levels. The Tensile strength of UHDCC was from 5 MPa to 20 MPa, the average Tensile Strain Capacity was 8% with the maximum value up to 12%. Four-point bending tests demonstrated that the plain UHDCC beams can match the loading Capacity of conventional reinforced concrete beams with the steel reinforcement ratio of 0.5–1.5%. The deflection-span ratio of all the plain UHDCC beams exceeded 1/50 at the peak load. The eccentric compressive loading tests showed that the loading Capacity of plain UHDCC column was close to that of RC column with a steel ratio of 0.8%. Additionally, shaking table tests were implemented on a RC frame (steel reinforcement ratios of columns were about 2.0%) and a plain UHDCC frame. The UHDCC frame survived 3 kinds of earthquakes with the peak ground acceleration from 0.105 g to 1.178 g, and exhibited excellent inter-story drift control under extremely strong earthquakes. The performance of the UHDCC frame fulfilled the requirements of various seismic codes. The feasibility of non-steel reinforced UHDCC structure was preliminarily confirmed by this study.
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feasibility study of Strain hardening magnesium oxychloride cement based composites
Construction and Building Materials, 2018Co-Authors: Yichao Wang, Jiangtao Yu, Jianzhuang Xiao, Shilang XuAbstract:Abstract Magnesium oxychloride cement (MOC) has been studied as an alternative to the ordinary Portland cement. Although MOC based concrete has good strength, early hardening and high bond strength, the applications have been limited due to its disadvantageous chemical nature to steel reinforcement and the natural brittleness. In order to extend this material to wider applications, MOC based engineered cementitious composites (MOC-ECC) was developed. The present paper introduces the fabrication of MOC-ECC with 4 different mixture proportions and a series of tests on the mechanical properties. The tests indicated that the MOC-ECCs have the Tensile Strain Capacity ranging from 5% to 7%, and the Tensile strength about 5 MPa. Furthermore, tight crack width control and exceeding compressive ductility were experimentally demonstrated. The addition of fly ash is proved of significant effect on the mechanical properties, including compressive strength, Tensile strength, Tensile Strain Capacity, matrix fracture toughness and fiber bridge Capacity. The fracture toughness and fiber bridge Capacity were used to explain the influence of fly ash to the Tensile Strain Capacity of MOC-ECC in a mesoscopic scale.
