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Application design of concrete canvas (CC) in soil reinforced structure
... Its shape is completely the same as the outer profile of the structure or element where CC is covered. Therefore, CC can be quickly, efficiently and widely used in civil engineering such as a cover of prefabricated shelter, a track-way for vehicles or pedestrians, and protection layer [11,12] for slope protection, and pipeline, etc. To use CC in the practice, its mechanical properties should be investigated thoroughly. ...
... The parameters in equation (19) C 1 , C 2 and C 3 can be expressed by equation (11). where v¼E f /E m ; � is the Poisson's ration; and E f and E m are Young's moduli of fiber and matrix, respectively. ...
Tensile behavior of concrete canvas (CC) mainly depends on the geometric patterns of 3D spacer fabric. A lattice model is proposed to model the three-dimensional structure of CC to investigate the influence of geometric patterns of 3D spacer fabric on the tensile behavior of CC. The stress intensity factor is also applied into the lattice model to study the crack development of CC subjected to tensile load. The simulation results are compared to the experiments to verify the model. Finally, the influence of geometric pattern of outer layer and spacer yarns on tensile behavior of CC are simulated based on our proposed lattice model. The results indicate that the tensile strength of CC increases as the loop unit size of outer surface decreases or the amount of spacer yarns increases; the tensile strength of CC with rhombus loop unit of outer surface
... Amzaleg et al. [14] investigated the flexural strength of four-point CC reinforced with 3D warp knitted fabrics and found that the flexural strength and elongation at break of 3D fabric consisting of aramid yarns was greater than 3D polyester fabric. Hui Li et al. [15] investigated the mechanical properties of reinforced cementitious composites with 3D warp knitted fabric. To improve the tensile strength of the composites, they used a modified ultra-high molecular weight polyethylene layer containing carbon nanotubes (CNT). ...
... Still, recently, calcium aluminate cement (CAC) has been widespread. CAC is a particular type of cement considered in CC due to its unique properties [15]. In these composites, CAC is used as an adhesive in the mortar instead of ordinary Portland cement (OPC) [17,18]. ...
Cement composites (CC) are among the composites most widely used in the construction industry, such as a durable waterproof and fire-resistant concrete layer, slope protection, and application in retaining wall structures. The use of 3D fabric embedded in the cement media can improve the mechanical properties of the composites. The use of calcium aluminate cement (CAC) can accelerate the production process of the CC and further contribute to improving the mechanical properties of the cement media. The purpose of this study is to promote the use of these cementitious composites by deepening the knowledge of their tensile properties and investigating the factors that may affect them. Therefore, 270 specimens (three types of stitch structure, two directions of the fabric, three water temperature values, five curing ages, with three repetitions) were made, and the tensile properties, absorbed energy, and the inversion effects were evaluated. The results showed that the curing conditions of the reinforced cementitious composite in water with temperature values of 7, 23, and 50 °C affect the tensile behavior. The tensile strength of the CCs cured in water with a temperature of 23 °C had the highest tensile strength, while 7 and 50 °C produced a lower tensile strength. The inversion effect has been observed in CC at 23 °C between 7 and 28 days, while this effect has not occurred in other curing temperature values. By examining three commercial types of stitches in fabrics and the performance of the reinforced cementitious composites in the warp direction, it was found that the structure of the “Tuck Stitch” has higher tensile strength and absorbed energy compared to “Knit stitch” and “Miss Stitch”. The tensile strength and fracture energy of the CC reinforced with “Tuck Stitch” fabric in the warp direction, by curing in 23 °C water for 7 days, were found to be 2.81 MPa and 1.65 × 103 KJ/m3, respectively. These results may be helpful in selecting the design and curing parameters for the purposes of maximizing the tensile properties of textile CAC composites.
... In regions with heavy traffic, using CC in construction can reduce the occupation of roads, thus effectively lowering construction cost. [10][11][12][13][14][15][16][17][18] However, CC also has some shortcomings such as weak compressive strength, flexural tensile strength, shear strength and penetration resistance. Fiber reinforced composite (FRP) has the advantages of light weight, high strength, good corrosion resistance, large plastic deformation, strong design ability, and good fatigue resistance. ...
... Results revealed that AFRP-reinforced CC could meet the protection requirements of slopes <10 m in height, and that AFRP-reinforced CC would be more suitable for slope protection projects requiring fast construction and facing rain or other severe environments. Li et al. 12 also explored the applicability of CC reinforced by carbon nano tube (CNT)modified ultra-high molecular weight polyethylene (UHMWPE) unidirectional fabric to the design of retaining walls and found that reinforced CC was applicable to reinforced earth retaining walls 3-10 m in height, and a reasonable reinforcement spacing is 0.5-1 m. ...
Concrete Canvas (CC) is a 3D spacer fabric-reinforced cement-based composite, prepared through filling cement-based composite powder into fabric via the porous surface of 3D spacer fabric. When hardened by water, CC forms a water-proof, fire-resistant, and durable concrete layer with outstanding mechanical properties. So far, CC has been applied in inflatable tents, slope protection, structure reinforcement and repair, ditch lining, and other engineering projects, as well as furniture and artwork design. Existing studies on CC primarily focus on the modification and optimization of its component materials, and CC reinforcement using externally bonded FRP and aluminum flakes. CC has a broad application and an enormous application potential in emergency engineering, such as the protection of emergency tents and shelters, emergency repair and construction of airport pavement and positional projects; however, it is necessary to improve the compressive strength, flexural strength, wear resistance, anti-penetration performance, and base course bond performance of CC. To that end, research from the perspectives of modifying CC component materials, reinforcement of CC by externally bonded FRP, the improvement of the anchorage method, and the optimization of anchoring primers can be carried out.
... In recent years, concrete canvas or fabric and fiber reinforced concrete have been developed for application in the geotechnical engineering field (Colombo et al., 2013;Li et al., 2016). Concrete canvas is a flexible cement powder permeated fabric that hardens when hydrated and changes into a thin, durable, waterproof, and fire-resistant concrete layer (Li et al., 2016). ...
... In recent years, concrete canvas or fabric and fiber reinforced concrete have been developed for application in the geotechnical engineering field (Colombo et al., 2013;Li et al., 2016). Concrete canvas is a flexible cement powder permeated fabric that hardens when hydrated and changes into a thin, durable, waterproof, and fire-resistant concrete layer (Li et al., 2016). When a layer of cement-treated sand is placed on the geotextile, the resulting composite material will be similar to concrete canvas but not exactly the same. ...
This paper presents the results of a laboratory and numerical study on the effects of cement treatment of the interface between geotextile and sand on the bearing capacity of a foundation built on geotextile-reinforced sand. The bearing capacity of a 25 cm × 7.5 cm strip footing on a 90 cm × 25 cm × 30 cm sand box reinforced using a single-layer reinforcement of different lengths including, 20, 30, 45, 60, 75 and 90 cm, was studied in a laboratory. A cement-treated zone was created on the geotextile to improve the friction and adhesion of the interface zone. Tests were also conducted on reinforced soil without a cement-treated zone and the results were compared. A finite element model was calibrated and used for further studies. The results of the laboratory tests indicated that cement treatment of the interface between the geotextile and sand increases the bearing capacity of the foundation by 6%–17%, depending on the length of the reinforcement. The effectiveness of the cement-treated interface on improving of the bearing capacity is more evident with shorter-length reinforcements. For a certain bearing capacity, the required length of the reinforcement was reduced by approximately 40% when the interface zone of the sand and reinforcement was cement-treated. The effect of the cement-treated zone on the bearing capacity was more evident in low settlement levels, and decreased as the length of the reinforcement increased.
... Innovation in RC structures has introduced concrete canvas (CC) to civil and military engineering due to its high density, corrosion resistance, and convenient construction. Some beneficial applications of CC include prefabricated shelter coverings, slope protections, tracks for vehicles or pedestrians, lining protections, and utilizations in the defense sector [11]. Chen et al. [12] found that 3D spacer fabric can arrest crack propagation, absorb impact energy, and improve its integrity. ...
To explore the crack behaviors of corroded concrete columns jointly reinforced by concrete canvas (CC) and carbon fiber reinforced polymer (CFRP), a total of six specimen sets with different reinforcement forms and corrosion rates are designed and tested by acoustic emission (AE) technology. The assessed methods are AE characteristic parameters, RA-AF values, b values, and AE event spatial location map. The results show that the presence of CC changes the failure morphology of the specimen and improves the uneven deformation of concrete in the core area, which proves that the jointly reinforced method exhibits high plasticity deformation ability. The crack mode of the jointly reinforced specimen undergoes multiple transformations between tensile cracks and shear cracks, before ending in the final crush failure. The fluctuations in both amplitude and frequency of the b values of the jointly reinforced specimens increase significantly with time. The crack activity of concrete is more intense in this period, which proves that the jointly reinforced method ensures a more complete failure. Moreover, the increases in corrosion rate reduced the probability of shear cracks in the core concrete and further increased the failure degree of the specimen. The present study demonstrated that AE monitoring can effectively capture the characteristics of the cracking process of jointly reinforced concrete.
... The material is a perfect solution for slope protection (Fig. 1, right), and several examinations were made, which gave good results. [19] [20] In place of the shotcrete layer, the CC hardens faster, and the properties are better or the same. The manufacturer shows several case studies on these topics [11]. ...
The Concrete Canvas (CC) material, is a promising material for application in many civil engineering fields, such as, water construction, pipelining, slope protection, military applications, etc. The authors believe that this material has more potential and could be helpful in infrastructure applications. The infrastructure design requirements are known; the CC has to be fit into the track structure. Several relevant investigations were performed to show the materials adequacy, and using collected data, FE (Finite Element) models were built to determine more of the physical parameters. From the results and the hardening experiences, it can be stated, that after the laying of CC and the spraying of water, the material has to be loaded to reach the best shape and push the material down to the supporting protection layer. In FE modeling, it was shown that the material is a
composite structure, i.e. one material's physical properties is not enough for modeling (it has to be improved). Moreover, it means that dynamic examinations can be initiated.
... After bonding, the fiber structure strengthens the concrete, avoiding cracking. Its lifespan is roughly 50 years [42]. Its effectiveness has been presented in several case studies [41]. ...
The construction and maintenance of a railway track is an expensive process. Therefore, nowadays, except for advanced countries, considerable attention must be paid to apply the optimal maintenance of railway lines. In Hungary, until 2020 nearly 11% of railway tracks were renewed and rehabilitated from EU support, which means millions of Euros, i.e. billions of Hungarian Forints. It also follows from the support that planned preventive maintenance works must be performed on the renewed and rehabilitated lines. On the other hand, it takes away significant costs from the non-renewed (non-rehabilitated) lines maintenance works, but naturally, less money does not mean less failures, so cost-effective technologies are needed. A segment of maintenance is the local substructure problem(s). In this article, this segment will be mentioned from the development of the failures, through the applied technologies, to the possible new solutions like injection and the using of geosynthetic cementitious composite mats (so called GCCMs).
... Since the usage of fine particle cement powder and the fully hydrated of cement powder, the matrix of CC after hydration is very dense and the permeability (k-value) of CC can reach between 10 −8 and 10 −9 m/s. More important, CC has a significant advantage for the rapid construction of slope protection [10] when the construction environment is severe and complex (i.e., emergency construction of slope protection or heavy rainfall). ...
Concrete canvas (CC) has the potential to become a widely used slope protection material owing to advantages such as flexibility, fast construction with low labor costs, and quick strength development. This article studies the mechanical properties and stability of CC slope protection by comparing it with conventional material (shotcrete). The compressive strength development and tensile strength of CC are first tested. To further improve the tensile strength of CC, an Aramid fiber reinforced sheet (called AFRP) is glued to the surface of CC. The tensile and shear behaviors of FRP-reinforced CC are investigated as well. Then, a finite element model is used to simulate the stability of the slope of CC (FRP-reinforced CC) and shotcrete with different curing times and the stability of CC slope protection under heavy rainfall. The results indicate that FRP-reinforced CC can satisfy the design requirements of slope protection when the height of the slope is below 10 m. Compare with traditional cementitious material (e.g., shotcrete), CC provides a more suitable solution for the rapid and abominable (e.g., heavy rainfall) construction of slope protection.
... 14 To these ends, the PI filaments may need to be knitted into a fabric formation with different structures to satisfy some specific needs. For example, the tensile strength of widely used polyethylene terephthalate (PET)-based three-dimensional (3D) warp-knitted spacer fabric [15][16][17][18] can be improved by partially or fully replacing PET filaments with PI filaments. However, it is still a problem to evaluate the knittability of PI filaments and some other high-performance fibers. ...
This paper presents an experimental investigation on the knittability of various polyimide (PI) filaments, namely PI-H (high strength and modulus), PI-M (moderate strength and modulus) and PI-L (low strength and modulus) filaments. The tensile strength of the PI-H, PI-M and PI-L filaments is 3.41, 1.65 and 0.88 GPa, and the Young’s modulus is 92.94, 40.71 and 9.43 GPa, respectively. The chemical compositions and structures of various PI filaments were characterized to explain the mechanical performance differences. The results show that the imidization degree, structural crystallinity and orientation have significant effects on the mechanical behaviors of PI monofilaments. The filament forces during the knitting process are simplified into straight tensile, loop tensile and abrasion actions, which have been tested and analyzed on PI monofilaments. A home-made simulative knittability analyzer was designed to test the knittability of the PI filaments. A hand flat knitting machine was used to verify the validity of the simulating methods and the constructed knittability analyzer. The PI-H, PI-M and PI-L filaments have poor, moderate and excellent knittability, respectively. The results also demonstrate that the simulating methods and the constructed simulative knittability analyzer are reasonable and efficient to evaluate the knittability of PI filaments.
... The mesh fabric is made in the same way as the solid fabric but with denser material and threads; this is done in order to allow cement powder to pass through in the manufacturing process. The mesh fabric is covered using a PVC membrane that is impermeable to both water and cement powder resulting in a well packaged product that hydrates the cement without allowing leakage (Hui Li, 2016). Fine Aggregates: Well graded sand was used as fine aggregates, with specific gravity of 2.51 ...
Concrete Cloth (CC) is an innovative material composed of a flexible aluminate cement powder-impregnated fabric that rapidly hardens upon hydration to form a thin, durable, waterproof and fire-resistant concrete layer. The material is delivered in the form of rolls at various thicknesses which allows their placement without a need for a plant or mixing equipment. Their ease and rapid installation facilitates their use in a wide range of applications such as slope stability, ditch lining and fast deploying shelters to name a few. This study aims at achieving a better understanding of the properties and performance of the concrete cloth material particularly when used in repair works. Tests including composition, microscopic analysis, chemical analysis, density and response to moisture were performed on the concrete cloth.
Sets of pre-cracked beams were prepared with crack length-to-beam depth ratio of ¼, ½, and ¾. The cloth material was installed to fortify the beam using three different adhesion techniques; Hilti anchors, epoxy resins and cementitious grout. The beams were tested under a three-point flexural test while deflection was recorded. Results indicate that the concrete cloth can enhance the flexural strength of the beams, although special adjustment needs to be introduced when used in repair works to enhance its benefits compared to other repair techniques.
... Its final shape is exactly same as the outer profile of the structure or element covered by the CC. Due to the flexibility and rapid construction of CC, with low labor cost, and the quick setting of CAC, CC has been applied in civil and military engineering [1], examples of applications including cover for a prefabricated shelter, slope protection [2], a trackway for vehicles or pedestrians, a protection layer for lining, and uses within the defense sector. However, compared to the casting, compacting, and finishing processes of conventional plain concrete or fiber/textile reinforced concrete, the impregnation process of dry cement powder into 3D spacer fabric leads to a relatively lower initial apparent density of CC, around 1300-1500 kg/m 3 , dependent on the geometrical pattern of the spacer fabric and the type of cementitious binder [3][4][5]. ...
Concrete canvas (CC) is a promising material in civil and military engineering due to its flexibility, fast construction with low labor cost, and rapid strength development. However, relatively lower tensile and flexural
strength limit the application of CC products. This paper presents an experimental study of the improvement of
the tensile and flexural strength of CC panels through the employment of external reinforcement by a fiber-reinforced polymer (FRP) sheet. The tensile and flexural behaviors of CC and FRP reinforced CC panels are
investigated through uniaxial tensile and four-point bending tests in both warp and weft directions. The bond
behavior between FRP sheets and CC is investigated through a single-shear pull-off test, by which both strain
distribution and local bond stress-slip relationships are experimentally measured. Experimental results reveal
that the tensile and flexural properties, especially the reinforcing efficiency of flexural strength, are significantly
improved in the FRP reinforced CC samples.
... Liu et al. 9 studied the quasi-static compression behavior of WKSF; the results indicate that WKSF is an ideal energy absorber for cushioning applications. Hanet al. [10][11][12][13] systemically studied the quasi-static mechanical and deformation behaviors of cement powder impregnated WKSF, called concrete canvas; the results revealed that compared with the matrix without fabric, WKSF provided an efficient reinforcement on both compressive and tensile behavior of the composite. In the research of dynamic mechanical properties, WKSF showed a high energy absorption capacity; meanwhile, the structural parameters significantly affect the impact properties of WKSF. ...
The aim of this research was to investigate the low-velocity impact properties of syntactic foam reinforced by warp-knitted spacer fabric (SF-WKSF). In order to discuss the effect of warp-knitted spacer fabric (WKSF) and hollow glass microballoon parameters on the impact performance of composites, eight different kinds of SF-WKSF samples were fabricated, including different WKSF surface layer structures, different spacer yarn diameters and inclination-angles, different microballoon types and contents. The low-velocity impact tests were carried out on an INSTRON 9250 HV drop-weight impact tester and the impact resistances of SF-WKSF were analyzed; it is indicated that most SF-WKSF specimens show higher peak impact force and major damage energy compared to neat syntactic foam. The results also demonstrate that the surface layer structure, inclination-angle of the spacer yarn and the volume fraction and type of microballoon have a significant influence on the low-impact performance of SF-WKSF. In addition, a finite element analysis finished with ANSYS/LS-DYNA and LS-PrePost was used to simulate the impact behaviors of SF-WKSF. The results of the finite element analysis are in agreement with the experimental results.
... 5 Interest has recently increased in the use of 3D spacer fabric as a novel reinforcement for cement-based composite materials, such as prefabricated wall panels, shell concrete members, retaining wall and slope protection, and FRP reinforcement. [6][7][8] In addition to its use in prefabricated elements, 3D spacer fabric presents new opportunities to manufacture more attractive cementitious composite concrete canvas (CC, concept first proposed by Brewin and Crawford in 2005). [9][10][11] Compared with conventional 3D spacer fabric reinforced cementitious composites, CC has a completely different preparation process. ...
A carefully designed formulation of dry cement powder for concrete canvas (CC), which is expected to have both high mechanical strengths and short setting times, is obtained by partially replacing calcium sulfoaluminate(CSA) cement with anhydrite at four levels (0%, 10%, 20% and 30 % by mass of CSA cement). The influence of anhydrite fineness on the mechanical properties of CC and its mechanical anisotropy are both investigated. X-ray diffraction analysis and isothermal calorimetry are used to investigate the underlying mechanism. Results reveal that increasing anhydrite content or fineness improve the mechanical strengths of CC and shorten its setting times. However, a slight decrease of mechanical strength occurrs at the later age when the replacement level reaches 30 wt. %. A large amount of unhydrous particles is found in hardened specimens. The CC shows higher mechanical strengths in the warp direction than in the weft direction, and it exhibits the lowest compressive strength in the through-the-thickness direction.
To evaluate the axial compression performance of corroded concrete short columns reinforced by concrete canvas (CC) and carbon fiber reinforced polymer (CFRP), a total of 16 specimen sets with different reinforcement forms and corrosion rates are designed and examined in this paper. Specimens are subjected to electrochemically-induced corrosion before being mechanically tested under the compressive load. The assessed variables are theoretical corrosion rate (0, 5%, or 10%), number of CFRP wrapping layers (0, 1, 2, or 3), and number of CC layers (0 or 1). Through the signal localization of acoustic emission (AE) and the variation in characteristic parameters, it is found that the presence of CC changes the failure morphology of the specimen and improves the uneven deformation of concrete in the core area. Also, under the same number of CFRP wrapping layers, the peak stress of the CC and CFRP jointly reinforced specimens is reduced by about 10% but has a more than 70% increase in the ultimate strain compared with those of CFRP reinforced only, which proves that the jointly reinforced method exhibits high plasticity deformation ability. With an increase in corrosion rate, compared with the uncorroded specimens, the peak stress of JC specimens decreases by more than 6.9% but the ultimate strain increases by more than 15.4%. The JC specimens’ peak stress and ultimate strain models are then determined through fitting, from which a good correlation with those observed is witnessed. The comparison shows that the model has good accuracy and can provide a theoretical basis for further research for CC- and CFRP-reinforced corroded concrete short columns.
The 3D textile-reinforced cementitious composite applications have various and large area of utilization. The studies have been performed on the 3D spacer fabrics, and its applications are especially on the improvement of the mechanical properties of the fabrics. However, the durability properties of the 3D spacer fabrics are also important for the 3D spacer fabric applications. Due to the lack of studies on this subject, this research attempts to investigate the performance of 3D textile-reinforced cementitious composite under elevated temperature. For this purpose, 3D textile-reinforced cementitious composite specimens were exposed to 150, 200, and 300 °C temperatures for two hours. Tensile and flexural tests were performed for determination of the performance of 3D textile-reinforced cementitious composite specimens before and after exposure to elevated temperatures. Test results indicate that the 3D textile-reinforced cementitious composite lost its bearing capacity at 300 °C.
Concrete canvas (CC) has been studied and applied for more than a decade; it has yet to be substantially studied in the field of water dosage. The unreasonable choice of water to cement ratio (w/c) might affect the quality and performance of CC. Thus, in this study, the experimental tests on the setting time, mechanical properties, X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM) of CC were carried out. The flexural and bursting behaviors in the early curing stage were also illustrated. The selected w/c was based on the water saturation level of CC during spraying. The obtained results indicated that mechanical properties of CC improved with the increase of w/c, while too much water somewhat delayed the hydration process in the first 3 days of curing. On the other hand, the low w/c would lead to insufficient hydration products and large size of loose defective structure in the interlayer of CC. An appropriate overdosage of water is considered suitable for CC solidification by spraying.
Since there is expeditious increase in the materials extensively used in construction, there is a great demand for construction materials in the current generation to follow different conventional methods. There is no provision for very quick and workable concrete installation procedures in the event of an emergency. Concrete as a construction material is well-known around the world, but the hunt to improve its flexibility has always piqued researchers' interest. Although concrete has many advantages, one disadvantage is that it is not flexible when hardened. The rising cost of repair work as a result of weathering, ground surface damage, and seepage in water canals has always been a source of concern. Concrete cloth, a new technology that removes faults from concrete and is flexible and simple to apply, has been invented. Concrete Canvas has a ceramic property which is semi rigid that makes it fire resistant and water proof.
A new geocomposite material introduced by cement treatment of the surfaces of an ordinary woven geosynthetic. Thin layers of cementitious material created on the surfaces of geosynthetic spraying the portland cement on the surfaces of a saturated geosynthetic and coating with sand. The interface behavior of the proposed cement coated geocomposite and sand was investigated in the laboratory using a series of pullout tests. The pullout tests performed on both cement coated geocomposites and pristine geosynthetics then the results were compared. The results of laboratory tests indicated that the interface adhesion, interface friction angle and pullout capacity of cement coated geocomposite is higher than those of pristine geosynthetic. For a similar stress level and thicknesses, the average interface friction angle and pullout capacity of the cement coated geocomposite were 29% and 38% higher than those of pristine geosynthetic which was used to produce the cement coated geocomposite.
In this study, the effect of concrete canvas (CC) panels on retrofitting of buried pipes against surface blast loads in different situations is investigated. The variable parameters studied are CC panels thickness (20 and 30 mm), the number of CC panels (1, 2, 3), soil type (two different soils), and the layout of CC panels (complete wrapping and U-wrap), respectively. For this purpose, the finite element method (FEM) is used to simulate models. In the finite element model, an explosive charge of 45 kg was simulated at a distance of 1 m above the steel pipeline. Validation of FEM used in simulating the present study was examined through comparing with the experimental results, and a good agreement was observed. The most important results show that the maximum stress and displacement in buried pipelines retrofitted with CC panels that are subjected to surface explosive loading are a function of thickness, number, and layout of CC panels, and to achieve optimal performance of CC panels, a combination of these parameters should be evaluated.
Purpose. The authors’ aim is to summarize the results of relevant international publications and, based on these, to give a comprehensive review about the modern ballasted tracks’ substructure. Methodology. This article is a start of a PhD research, which means it was proceeded by a secondary research. At first, the substructure and its protection layers were summarized, after that the geosynthetic cementious composite mat materials, especially the Concrete Canvas are discussed. Findings. The experiences of the geosynthetics’ and other protection layers’ functions, show that a possible using of the GCCM (geosynthetic cementious composite mat) under the ballast can be a good solution for renewing short sections in the railway tracks. Originality. One of the authors – namely Balázs Eller – is a PhD student at Szechenyi Istvan University in Gyor (Hungary). His research topic is the reinforcement possibilities of railway substructure with the usage of special (mainly cement-bonded) layers. This article was written to collect and summarize the up to date knowledge related to modern ballasted railway tracks’ substructure to be able to determine the following research ways and possibilities at this topic. The research plan will be sentenced in the near future, as well as the required laboratory and field tests will be prepared. Practical value. As expectation, after having executed the related research, the advantages and disadvantages of GCCM layers in the railway substructure will be able to defined, as well as factual deterioration process can be determined related to the ballasted tracks and their geometrical stability.
This paper presents the fundamental mechanical properties that characterise constitutive behaviours of GCCM for large-strain problems in unidirectional tensile and axi-symmetry puncture tests. The 2D nonlinear FEA was conducted to simulate the GCCM behaviour. The optimised stiffness parameters can simulate the elastic behaviour of GCCM. The post-cracking governed by inelasticity of woven geotextile is modelled by bilinear stress-strain relationship. The interface between woven geotextile and cement layer is explained by the existing bond-slip model. The analytical results are presented in terms of load-displacement curves as well as the crack patterns, which are similar to the experimental results.
An approach of aligning steel fibers in cement mortar using external uniform electromagnetic field is presented, which is the rotating process of steel fiber driven by magnetic force to overcome the viscous impeding of the mortar. Using the approach, the aligned steel fiber reinforced cement mortar (ASFRC) is prepared. Then the orientation distribution of the steel fibers in ASFRC is measured by X-CT image analysis. The results show that the orientation efficiency factor of the steel fibers in ASFRC reaches around 0.90, while that of ordinary steel fiber reinforced cement mortar (SFRC) is around 0.50. Also, the splitting tensile strength, flexural strength and toughness of the ASFRC are tested. The test results show that, compared with SFRC, the splitting tensile strength and flexural strength of ASFRC increase up to more than 100%, which is attributed to the increase in reinforcing efficiency of aligned steel fibers.
Since the 1960s, retaining structures with reinforced backfill have undergone a remarkable development. Although important progress has been made regarding understanding of their behaviour, much remains to be done, especially on their design. The work described herein aims to contribute to the development of a design method for brick-faced reinforced retaining walls that should be very simple to use. A study was carried out by using some known methods of analysis, and by comparing the results obtained with the behaviour already known for this type of wall from previous laboratory and numerical studies. Both Rankine's and Coulomb's modified approach were used, and also three other methods allowing potential failure surfaces that were planar, circular and bilinear in shape. The comparative studies performed showed good predictions when a circular or a bilinear failure surface was considered, although the latter method allows a more versatile definition of the potential failure surface.
Understanding soil-geogrid interaction is essential for the analysis and design of geogrid-reinforced soil
structures. A first step towards accurate modeling of this interaction is choosing a suitable material
model for the geogrid that is capable of simulating tensile test results. The model should be able to capture
the three-dimensional response of the geogrid considering its exact geometry. Modeling geogrid inclusion
as a continuous sheet has proven to reasonably simulate the overall response of soil-geogrid
systems; however, it does not explain the different sources of interaction between the geogrid layer
and the surrounding soil. To understand the three-dimensional aspects of this complex interaction
problem, a two-phase numerical investigation is developed in this study. The first phase focuses on the
three-dimensional modeling of unconfined biaxial geogrid subjected to tensile loading. Applicability of
the geogrid model in solving soil-structure interaction problems is then demonstrated, in the second
phase, by investigating the response of a reinforced subgrade subjected to a square shaped surface
loading. It is concluded that modeling the three-dimensional geogrid geometry is important to accurately
capture the true response of geogrid under both confined and unconfined conditions. The
modeling approach proposed in this study for the analysis of unconfined and soil-confined geogrid can
be adapted for other reinforced soil applications.
The techniques of soil reinforcement by geotextile are easy and economic solutions that limit the surface settlements of embankments prone to sinkholes. The design of such structures is based on understanding complex mechanisms, such as the tensile geosynthetic behavior under vertical loading, the frictional interaction between the soil and the reinforcement, the load transfer mechanisms and the arching effect in the soil embankment. Recently, significant progress has been made, allowing for improvement of the design methods by taking into account the frictional and sliding effects of the geosynthetic sheet in the anchorage areas and the local increase of the vertical stresses in the vicinity of the edges of the cavity. Nevertheless, the soil dilatancy, or the load transfer mechanisms in the embankment during the formation of the cavity or under static or cyclic loadings, remains unknown. Additionally, the reinforced, treated soil layer has not been specifically studied. To focus on the soil embankment behavior over a void, experimental studies were conducted as part of the FUI research project GéoInov.
A carefully designed formulation of dry cement powder for concrete canvas (CC), which is expected to have both high mechanical strengths and short setting times, is obtained by partially replacing calcium sulfoaluminate(CSA) cement with anhydrite at four levels (0%, 10%, 20% and 30 % by mass of CSA cement). The influence of anhydrite fineness on the mechanical properties of CC and its mechanical anisotropy are both investigated. X-ray diffraction analysis and isothermal calorimetry are used to investigate the underlying mechanism. Results reveal that increasing anhydrite content or fineness improve the mechanical strengths of CC and shorten its setting times. However, a slight decrease of mechanical strength occurrs at the later age when the replacement level reaches 30 wt. %. A large amount of unhydrous particles is found in hardened specimens. The CC shows higher mechanical strengths in the warp direction than in the weft direction, and it exhibits the lowest compressive strength in the through-the-thickness direction.
Since the 1960s, retaining structures with reinforced backfill have undergone a remarkable development. Although important progress has been made regarding understanding of their behaviour, much remains to be done, especially on their design. The work described herein aims to contribute to the development of a design method for brick-faced reinforced retaining walls that should be very simple to use. A study was carried out by using some known methods of analysis, and by comparing the results obtained with the behaviour already known for this type of wall from previous laboratory and numerical studies. Both Rankine's and Coulomb's modified approach were used, and also three other methods allowing potential failure surfaces that were planar, circular and bilinear in shape. The comparative studies performed showed good predictions when a circular or a bilinear failure surface was considered, although the latter method allows a more versatile definition of the potential failure surface.
Concrete canvas (CC) has been taken attentions for their rapidly deployable hardened characteristic property in civil engineering. However, the drying shrinkage of CC has not been addressed yet in the literatures. In this study, a theoretical model was presented for studying influences of 3D spacer fabric on drying shrinkage of concrete canvas (CC). The model was based on assumption that drying shrinkage restraint provided by 3D spacer fabric is joint action of each component of 3D spacer fabric separately. To calibrate this model, the drying shrinkage of two CCs reinforced by PET-based 3D spacer fabric with one solid outer textile substrate was experimented. Moreover, a simplified expression of maximum tensile stress generated in the matrix of both CCs was obtained for evaluating their risk of drying shrinkage-induced cracking. The results showed that drying shrinkage strain of CC samples became lower due to the restraint provided by 3D spacer fabric and a satisfactory correlation between model predictions and experimental results was found at later age. For both CCs, a greater restraint was found in warp direction and thereby resulting in a larger tensile stress generated in the matrix. Furthermore, the restraint on the drying shrinkage of CC was provided mostly by spacer yarns and thereby it contributed to the most of maximum tensile stress generated in the matrix of CC.
In this study, influences of geometric patterns of 3D spacer fabric on the tensile behavior of concrete canvas (CC) were investigated. Five 3D spacer fabrics with different geometric patterns were investigated. Tensile stress-strain curves and crack propagating patterns of CCs were obtained in warp and weft directions through experiments. Experimental results revealed that the CC samples reinforced by the 3D spacer fabrics with one solid outer textile substrate exhibited improved tensile behaviors in terms of tensile strength, reinforcing efficiency factor and crack pattern. Moreover, for CCs, 3D spacer fabric reinforcement was a better option than spacer yarns alone.
Polyvinyl chloride (PVC) and polyvinyl formal (PVF) blend ultrafiltration membranes were fabricated by non-solvent induced phase separation (NIPS) method with different casting solution composition. The PVC/PVF membranes were characterized and evaluated by scanning electron microscopy (SEM), Fourier Transform Infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), water contact angle measurement and performance measurement. The results showed that PVF played the role of pore formation agent during the NIPS process, and both of porosity and the mean pore size of the membranes were increased with the increased dosage of PVF. Simultaneously, PVF was enriched to membrane surface via spontaneous surface segregation and the membrane surface hydrophilicity was greatly elevated, which implied the remarkably enhanced antifouling property. The robust residence of PVF on the membrane surface was confirmed by a long-term test of incubating membranes in deionized water, which revealed the stable antifouling property of PVC/PVF membranes. Therefore, PVF could be explored as a potential versatile modifier for fabricating high performance ultrafiltration membranes.
There have been very few studies on the application of soil-rock mixtures as the backfills of geogrid reinforced soil retaining walls with due concern for their long-term performance and safety. In this study, a 17-m high two-tiered reinforced soil wall backfilled with soil-rock mixture was instrumented for its performance under gravity load after construction. The instrumentation continued for 15 months. It is found that soil-rock mixtures with small rock content (<30%) have the potential to be used as the backfill materials of geogrid-reinforced retaining walls, but special attentions should be given to compaction quality, backfill–geogrid interaction, and installation damage to geogrids. Reinforcement slippage is possible because of the large particles, but it was small in this case and ceased to develop nine months after the end of construction. Compressibility difference between reinforced and unreinforced backfill might led to rotation of the upper tier. Using the estimated soil strength, the predictions of reinforcement loads by the FHWA methods were 100% higher than the estimated ones from measured strains.
An overview of past and recent developments on the subject of seismic earth pressures on yielding, gravity-type walls, retaining cohesionless backfill, is first presented, focusing on available data on the issue of phase difference that develops between the peak values of wall inertia and seismic earth thrust increment. The results of a FEM parametric study are next presented regarding the dependence on the resulting dynamic earth thrust reduction – acting on the time of peak wall inertia – on backfill rigidity, wall height, and shaking characteristics. The reliability of the numerical analyses was verified by modeling centrifuge tests reported by Nakamura [24] and successfully comparing measured vs. computed behavior. The results of the parametric analyses indicate that the seismic active earth thrust, acting on the wall at the time of maximum wall inertia, is significantly reduced (compared to its peak value) with increasing shaking intensity of backfill, increasing wall displacements, increasing wall height, and decreasing backfill rigidity. No systematic dependence on the ratio of input motion frequency to the natural frequency of the backfill (f/f1) was observed. The above findings: (1) verify earlier experimental and numerical results, (2) explain the reported lack of damage to retaining walls under strong ground shaking, and (3) indicate the need for revising the pertinent provisions of current seismic codes. Graphs summarizing the results of the numerical analyses are presented which may be used as a guide for selecting the magnitude of seismic active earth thrust that needs to be taken into account in the design of the examined type of earth retaining walls.
Textile Reinforced Concrete (TRC) is an advanced cement-based material in which fabrics used as reinforcement can bring significant loads in tension, allowing architects and engineers to use thin cross-sections. Previous research projects, developed during the last 10 years mainly in Germany, Israel and the USA, have shown the capabilities of such a material. In this paper an extensive experimental investigation of TRC is presented: tensile tests were carried out to obtain a complete mechanical characterization of the composite material under standard conditions, considering the influence of different variables such as reinforcement ratio, fabric geometry, curing conditions, displacement rate and specimen size.
Three well-defined diblock copolymers of poly(methyl methacrylate-b-methacrylic acid) (P(MMA-b-MAA)) were synthesized using atom transfer radical polymerization method and varying poly(methacrylic acid) (PMAA) chain lengths. These copolymers were blended with PVC to fabricate porous membranes via phase inversion process. Membrane morphologies were observed by scanning electron microscopy (SEM), and chemical composition changes of the membrane surfaces were measured by X-ray photoelectron spectroscopy (XPS). Static and dynamic protein adsorption experiments were used to evaluate antifouling properties of the blend membranes. It was found that, the blend membranes containing longer PMAA arm length showed lower static protein adsorption, higher water permeation flux and better protein solution flux recovery.
A mechanically stabilized earth (MSE) wall behaves as a flexible coherent block able to sustain significant loading and deformation due to the interaction between the backfill material and the reinforcement elements. The internal behaviour of a reinforced soil mass depends on a number of factors, including the soil, the reinforcement and the soil/structure interaction and represents a complex interaction sol/structure problem. The use of parameters determined from experimental studies should allow more accurate modelling of the behaviour of the MSE structures.In this article, a reference MSE wall is modelled from two points of view: serviceability limit state “SLS” and ultimate limit state “ULS”. The construction of the wall is simulated in several stages and the soil/interface parameters are back analysed from pullout tests. An extensive parametric study is set up and permits to highlight the influence of the soil, the reinforcement and the soil/structure parameters. The behaviour of MSE walls with several geosynthetic straps is compared with the metallic one. Several constitutive models with an increasing complexity have been used and compared.The results obtained from stress-deformation analyses are presented and compared. The use of geosynthetic straps induces more deformation of the wall but a higher safety factor. To design theses walls the important parameters are: the soil friction, the cohesion, the interface shear stiffness and the strip elastic modulus.It is shown that for wall construction that involves static loading conditions, the modified Duncan–Chang model is a good compromise but induces slightly lower strip tensile forces due to the fact that it do not take into account of dilatancy before failure.
A method for the internal design of reinforced soil walls based on working stresses is developed and evaluated using measurements from five full-scale structures containing a range of reinforcement types. It is shown that, in general, the stiffer the reinforcement system and the higher the stresses induced during compaction, the higher are the tensile stresses that must be resisted by the reinforcements. Unique features of this method, compared to currently used reinforced soil wall design methods, are that it can be applied to all types of reinforcement systems, reinforcement and soil stiffness properties are considered, and backfill compaction stresses are taken explicitly into account. The method can be applied either analytically or using design charts. A design example is included.
Spacer fabrics have been used in many areas varying from medical applications to protection applications. Especially the three
dimensional characteristic of spacer fabrics presents different opportunities for special applications. The compression resistant
characteristic of spacer fabrics is one of their main properties. In this research the compression behaviour of spacer fabrics
designed for concrete applications has been investigated. The effects of some parameters such as spacer yarn material, pattern
and threading on the compression behaviour of spacer fabrics have been studied. According to the test results it was found
that the material, pattern and the threading of spacer yarns are important parameters for the compression characteristics
of spacer fabrics. It was also observed that the location angle of spacer yarn and the amount of the spacer yarns influence
the compression behaviour of spacer fabrics.
Limit equlibrium methods are evaluated with respect to their ability to predict failure of geosynthetic reinforced slope models tested in a geotechnical centrifuge. The variables considered in the centrifuge testing program were the reinforcement spacing, reinforcement tensile strength, and soil shear strength. Extensive testing was initially conducted to evaluate the strength properties under operational conditions of the backfill material, and model geotextile reinforcements, and the several interfaces in the slope models. Parametric studies were performed to evaluate the effect of the in-soil geotextile tensile strength, nonuniformity of unit weight in the centrifuge models, orientation of reinforcement forces, requirement overlapping layers, lateral friction of the models against centrifuge box, and selected method of slope stability analysis. All centrifuge slope models built using the same backfill soil yield a single Normalized Reinforcement Tension Summation. This normalized value can be interpreted as an earth pressure coefficient that depends on the soil friction angle and on the slope inclination. The evaluation also indicates that limit equilibrium should consider horizontal orientation of reinforcement forces, that significant contribution to stability is provided by the overlapping reinforcement layers, and that different rigorous limit equilibrium methodologies provide equally good results. Very good agreement was obtained between the g-levels at failure obtained experimentally and those predicted by limit equilibrium. Equally good agreement was obtained between experimental and predicted locations of the failure surfaces.
In conventional reinforced soil structures, the reinforcements are often laid horizontally in the soil. In this paper, a new concept of soil reinforced with horizontal–vertical (H–V) orthogonal reinforcing elements is proposed. In the proposed method of soil reinforcement, H–V orthogonal elements instead of conventional horizontal inclusions are placed in the soil. A fundamental difference between the H–V orthogonal reinforcing elements presented in this paper and other forms of inclusions is that the soil enclosed within the H–V orthogonal reinforcing elements will provide passive resistances against shearing that will increase the strength and stability of the reinforced soil. A comprehensive set of triaxial tests were carried out on sand reinforced with multi-layer H–V orthogonal elements and vertical ones. The behavior of sand reinforced with different H–V orthogonal elements was studied in terms of stress–strain relationship and shear strength. Based on experimental results, a strength model of the soil reinforced with H–V orthogonal elements was developed by means of the theory of limit equilibrium. The results of proposed strength model are compared with those obtained from the triaxial tests. It is shown that the results of prediction are in good agreement with those of the triaxial tests.
There is a burgeoning interest in the development, characterization, and implementation of alternatives to Portland cement as a binder in concrete. The construction materials industry is under increasing pressure to reduce the energy used in production of Portland cement clinker and the associated greenhouse gas emissions. Further, Portland cement is not the ideal binder for all construction applications, as it suffers from durability problems in particularly aggressive environments. Several alternative binders have been available for almost as long as Portland cement, yet have not been extensively used, and new ones are being developed. In this paper, four promising binders available as alternatives to Portland cement are discussed, namely calcium aluminate cement, calcium sulfoaluminate cement, alkali-activated binders, and supersulfated cements. The history of the binders, their compositions and reaction mechanisms, benefits and drawbacks, unanswered questions, and primary challenges are described.
Textile Reinforced Concrete shows a complex mechanical behaviour, which arises from the heterogeneity of the cementitious matrix and the reinforcement yarn, as well as different bond conditions inside the yarn. In this contribution, a reduced two-dimensional model for simulating the uniaxial tensile behaviour of Textile Reinforced Concrete is presented. In the model, the longitudinal (loading) direction is discretised over the whole specimen length, while in the cross-sectional direction only the heterogeneity of the reinforcement is modelled by dividing the yarns into homogeneous segments arranged in a regular lattice scheme. The model also includes limited tensile strength for the matrix and the reinforcement, as well as a non-linear bond law with bond degradation between the constituents of the composite. Parametric studies are performed to show how the bond properties, e.g. the maximum bond stresses or the penetration depth of matrix in the yarns, influence the structural behaviour and the local load-bearing behaviour.
This study explored the influences, of different textile characteristics of warp knitted fabrics made from multifilament yarns, on the tensile properties of textile reinforced cement elements and on the bonding quality between the fabrics and the cement matrix. Several parameters such as loop size, bundle size (number of filaments), and fiber type (high density polyethylene, polypropylene, AR-glass and aramid) were examined. In addition, the influence of a hybrid fabric made from polypropylene and aramid was examined and compared to single fabrics made of aramid and polypropylene separately. All the composite elements were produced by the pultrusion technique. It was found that fabric made of combination of a small bundle diameter and a large loop size exhibited the greatest efficiency factor and developed the best bond strengths with the cement matrix, based on improved cement penetrability between the filaments of the bundle. The hybrid composite system showed better mechanical properties and a higher efficiency factor compared to the non-hybrid systems.
At present there is a rising interest of architects and engineers in the application of Textile Reinforced Concrete (TRC) as a construction material. Filigree, self-supporting and ventilated façade systems are state-of-the-art in the application of TRC. In current investigations potentials for light-weight structural members are developed. The required models for a secure design of structural members are deduced within the framework of the research activities in the collaborative research centre 532 at RWTH Aachen University [Collaborative Research Centre 532: Textile Reinforced Concrete–Development of a new technology. RWTH Aachen University, Germany. http://sfb532.rwth-aachen.de]. The article outlines fundamental research results as well as their realisation in first applications.
The design methods used for soil mass structures, such as mechanically stabilised earth (MSE) structures, are based on soil/reinforcement anchorage models which require the knowledge of the soil/reinforcement interface friction capacity. However, different types of reinforcements are used in these structures and present different behaviour. This study concerns two types of strips reinforcements. The first one is metallic and is classically designed using elasto-plastic models (
[21] and [22]). The second type is geosynthetic. The classical anchorage models do not take into account the extensibility of this materiel and do not reproduce its complex behaviour.In the first part this paper presents pull-out tests carried out on the two types of strips reinforcements (metallic and synthetic) subjected to several levels of vertical stresses. The tests are carried out in a metallic tank in controlled and instrumented conditions. In the second part, three modelling processes of the pull-out tests are implemented. The first method takes classical anchorage models into account. The second method improves the friction model using the analysis of the experimental tests. The last method adds the real tensile behaviour of the synthetic reinforcement to the second and assumes an initial strain threshold ɛ0 (Bourdeau et al. 1990) in order to simulate the delayed mobilisation. This analysis leads to parameters which qualify the interaction between metallic or synthetic strips and the soil mass, and enable a better understanding of the behaviour of the structures.
Some experiments utilizing the shear capacity of Engineered Cement-based Composites (ECC) have suggested that elimination of shear reinforcement is feasible when the concrete matrix is replaced by ECC. However, actual application and more rigorous cost analysis are prevented by the fact that the shear stress and strain properties of ECC have not yet been characterized as accurately as the tensile properties. This study focuses on the investigation of the shear property of ECC. The study starts with a survey and comparison of existing shear tests for composite materials. The Iosipescu shear test concept is chosen as the most objective method for ECC, and subsequently, modified for specific application on ECC by simple analytical design and finite element refinement. The modified Iosipescu shear test method is applied on, four types of ECC specimens with different fibre content (0%, 1%, 2%, 2.5% by volume), which have been cast in specially designed moulds and cured in laboratory conditions. Three phases of shear measurements are used to check the shear test appropriateness and study the shear mechanical properties of ECC. The failure mode is verified in the first phase, detailed measurement of the shear strain and shear stress is performed and recorded in the second phase, and in the third phase more information about the ductility of diagonal cracking is obtained by measurement of the tensile principal deformation. By also conducting direct tensile tests on specimens of the exact same mix, information of both uniaxial tension and shear behaviour is available, from which elastic and shear moduli, as well as Poisson’s ratio of ECC are computed. A first step toward application of this knowledge of the shear behaviour of ECC is taken by studying the response of shear-dominated beams and beam-columns of reinforced concrete and reinforced concrete combined with ECC as the outer crusts. These beams were prepared and tested by other members of the research group of the Division for Structural Engineering of the University of Stellenbosch. It is shown that ECC can indeed successfully replace shear reinforcing steel, due to its shear capacity. Thesis (MScEng (Civil Engineering)--University of Stellenbosch, 2006.
Preparation and Performance of Concrete Canvas (in Chinese)
- B C Bao
Bao, B.C., 2013. Preparation and Performance of Concrete Canvas (in Chinese). Msc
Thesis. Southeast University, Nanjing.
Horizontal displacement of the wall with different types of reinforcement elements
- Fig
Fig. 16. Horizontal displacement of the wall with different types of reinforcement elements.
Experimental study on mechanical behavior of FRP reinforced concrete canvas panel
- F Y Zhang
- H S Chen
- L Liu
- T Lv
- W L Zhang
- Y J Yang
Zhang, F.Y., Chen, H.S., Liu, L., Lv, T., Zhang, W.L., Yang, Y.J., 2016. Experimental study
on mechanical behavior of FRP reinforced concrete canvas panel. Compos.
Struct. submitted@2016.01.20.
- I G Colombo
- A Magri
- G Zani
- M Colombo
- M Di Prisco
Colombo, I.G., Magri, A., Zani, G., Colombo, M., di Prisco, M., 2013. Erratum to: textile
reinforced concrete: experimental investigation on design parameters. Mater.
Struct. 46 (11), 1953e1971.