Fabric-reinforced Cement Composites Research Articles

Comparison of commercially available 25OHD and 1,25(OH)2D assays: Experience of pediatric hospital laboratory participating in DEQAS proficiency testing

Textile Reinforced Cement composites (TRCs) have become a key research topic when it comes to lightweight alternative construction materials for traditional concrete industry. While most of the research performed on TRCs combines a cementitious matrix material with 2D textile fabrics, this paper investigates the mechanical behaviour of TRCs reinforced with 3D textile fabrics. The main goal is to investigate the influence of the transversal fibre that is connecting the fibre layers and is typical for 3D textiles, on the tensile and flexural properties of the TRC. Therefore two textile fabric architectures were compared, firstly an unaltered 3D textile fabric and secondly a tensile-equivalent 2D textile fabrics with equal in-plane textile reinforcement. An experimental campaign in tension and bending was performed on four different TRC layups. When comparing the bending behaviour of the unaltered 3D-TRCs with the 2D alternatives, an increase in stiffness in the post-cracking stage was observed, while no influence was observed in tension. The experimental results were also compared with numerical predictions of the 2D-TRCs to put in evidence the influence of the 3D architecture.

Fatigue Behaviour of Textile Reinforced Cementitious Composites and Their Application in Sandwich Elements

Using large lightweight insulating sandwich panels with cement composite faces offers great possibilities for the renovation of existing dwellings. During their lifetime, these panels are subjected to wind loading, which is equivalent to a repeated loading. To guarantee the structural performance of these panels during their entire lifetime, it is necessary to quantify the impact of these loading conditions on the long term. The fatigue behaviour was, therefore, examined in this paper both at the material level of the faces and at the element level as well. plain textile reinforced cementitious composite (TRC) specimens were subjected to 100,000 loading cycles by means of a uniaxial tensile test, while sandwich beams were loaded 100.000 times with a four-point bending test. Results show that the residual behaviour is strongly dependent on the occurrence of cracks. The formation of cracks leads to a reduction of the initial stiffness. The ultimate strength is only affected in a minor way by the preloading history.

Thermomechanical Behavior of Textile Reinforced Cementitious Composites Subjected to Fire

The mechanical behavior of textile reinforced cementitious composites (TRC) has been a topic of wide investigation during the past 30 years. However, most of the investigation is focused on the behavior under ambient temperatures, while only a few studies about the behavior under high temperatures have been conducted thus far. This paper focused on the thermomechanical behavior of TRC after exposure to fire and the residual capacity was examined. The parameters that were considered were the fiber material, the thickness of the concrete cover, the moisture content and the temperature of exposure. The specimens were exposed to fire only from one side and the residual strength was measured by means of flexural capacity. The results showed that the critical factor that affects the residual strength was the coating of the textiles and the law of the coating mass loss with respect to temperature. The effect of the other parameters was not quantified. The degradation of the compressive strength of TRC was quantified with respect to temperature. It was also concluded that a highly asymmetrical design scheme might lead to premature failure.

Bond Strength between Glass Fiber Fabrics and Low Water-to-Binder Ratio Mortar: Experimental Characterization

Full utilization of mechanical properties of glass fiber fabric-reinforced cement composites is very limited due to a low bond strength between fibers and the binder matrix. An experimental setup was developed and evaluated to correlate the mortar penetration depth with several key parameters. The studied parameters included fresh mortar properties, compressive and flexural strengths of mortar, the fabric/mortar bond strength, fabric pullout strength, and a single-lap shear strength. Results showed that an average penetration of mortar did not exceed 100 µm even at a higher water-to-binder ratio. The maximum particle size of the used fillers should be below an average spacing of single glass fibers, which in this case was less than 20 µm to avoid the sieving effect, preventing effective penetration. The pullout strength was strongly affected by the penetration depth, while the single-lap shear strength was also additionally affected by the mechanical properties of the mortar.

Influence of environmental loading on the tensile and cracking behaviour of textile reinforced cementitious composites

In outdoor applications, textile reinforced cementitious composites (TRCs) are susceptible to varying weathering conditions. To guarantee their performance during the entire life-time, it is necessary to evaluate the long-term behaviour. In this paper, the mechanical behaviour of reference specimens is compared to aged specimens, which are subjected to heat-rain and/or freeze-thaw cycles. Results show that subjection to heat-rain cycles leads to a larger degradation of the tensile behaviour compared to subjection to freeze-thaw cycles. Besides the macroscopic tensile behaviour, also the cracking behaviour is evaluated. Analysis shows that cracks are formed at lower stress levels after being subjected to environmental loading.

Polymer Modification of Fine Grained Concretes Used in Textile Reinforced Cementitious Composites

Polymer Modification of Fine Grained Concretes Used in Textile Reinforced Cementitious Composites

Effect of polymer addition on air void content of fine grained concretes used in TRCC

Textile Reinforced Cementitious Composite (TRCC) became the most common construction material lately and have excellent properties. TRCC can be employed in the manufacture of thin-walled facade elements, load-bearing integrated formwork, tunnel linings or in the strengthening of existing structures. These composite materials are a combination of matrix and textile materials. There isn\'t much research done about the usage of polymer modified matrices in textile reinforced cementitious composites. In this study, matrix materials named as fine grained concretes (dmax 1.0 mm) were investigated. Air entraining effect of polymer modifiers were analyzed and air void content of fine grained concretes were identified with different methods. Aim of this research is to study the effect of polymer modification on the air content of fine grained concretes and the role of defoamer in controlling it. Polymer modifiers caused excessive air entrainment in all mixtures and defoamer material successfully lowered down the air content in all mixtures. Latex polymer modified mixtures had higher air content than redispersible powder modified ones. Air void analysis test was performed on selected mixtures. Air void parameters were compared with the values taken from air content meter. Close results were obtained with tests and air void analysis test found to be useful and applicable to fine grained concretes. Air void content in polymer modified matrix material used in TRCC found significant because of affecting mechanical and permeability parameters directly.

Enhanced impact properties of cementitious composites reinforced with pultruded flax/polymeric matrix fabric

Fiber reinforced concrete (FRC) has become increasingly applied in civil engineering in the last decades. Natural fiber fabric reinforced cement composites are considered to prevent damage resulting from an impact loading on the cementite plate. Flax woven fabric that has a high energy absorption capability was chosen. To increase the interfacial shear properties, the fabric was pultruded with different matrix properties that affect the strength and toughness of the pultruded fabric. In this study, three fabric structures are used to increase the anchoring of the cement in the fabric. The compressive strength and the impact energy were measured. The results revealed that pultruded fabric reinforced cement composite (PFRC) absorbs much more impact energy. PFRC under impact loading has more micro cracks, while plain cement specimen shows brittle failure. The compressive test results of PFRC indicate that flax fiber fabric polymer enhanced compressive strength remarkably. Fiber reinforcement is a very effective in improving the impact resistance of PFRC. The study defines the influence factors that control the energy dissipation of the composite, which are the hardness of the polymer and the fabric cover factor. Significant correlation between impact energy and compressive strength was proved.

Development of fine grained concretes for textile reinforced cementitious composites

A new innovative composite material is textile reinforced cementitious composite (TRCC). To achieve high flexural performance researchers suggest polymer modification of TRCC matrices. In this study, nine ready mix repair mortars commonly used in construction industry and the production of TRCC elements were examined. Mechanical properties such as compressive and flexural strength, drying shrinkage were studied. Being a significant durability concern, alkali silica reaction tests were performed according to related standards. Results showed that, some ready repair mortar mixes are potentially reactive due to the alkali silica reaction. Two of the ready mortar mixes labelled as non-shrinkage in their technical data sheets showed the highest shrinkage. In this experiment, researchers designed new matrices. These matrices were fine grained concretes modified with polymer additives; latexes and redispersible powders. Two latexes and six redispersible powder polymers were used in the study. Mechanical properties of fine grained concretes such as compressive and flexural strengths were determined. Results showed that some of the fine grained concretes cast with redispersible powders had higher flexural strength than ready mix repair mortars at 28 days. Matrix composition has to be designed for a suitable consistency for planned production processes of TRCC and mechanical properties for load-carrying capacity.

Effect of calcined nanoclay on the durability of NaOH treated hemp fabric-reinforced cement nanocomposites

Cement nanocomposites reinforced with hemp fabrics and calcined nanoclay (CNC) have been fabricated and investigated. The treated hemp fabric-reinforced cement composites and nanocomposites were subjected to 3 wetting and drying cycles and then tested at 56 and 236days. The influences of CNC dispersion on the durability of these composites have been characterized in terms of porosity, flexural strength, stress-midspan deflection curves and microstructural observation of hemp surface. The microstructure of matrix was investigated using X-ray Diffraction. Results indicated that the CNC effectively mitigated the degradation of hemp fibre. The durability and the degradation resistance of hemp fibre enhanced due to the addition of CNC into the cement matrix and the optimum content of CNC was 1wt.%.

Effect of calcined nanoclay on microstructural and mechanical properties of chemically treated hemp fabric-reinforced cement nanocomposites

The influence of calcined nanoclay (CNC) and chemical treatment on the microstructure and mechanical properties of treated hemp fabric-reinforced cement nanocomposites has been investigated. The optimum hemp fabric content for these nanocomposites is 6.9wt% (i.e. 6 fabric layers). Alkali-treated hemp fabric-reinforced cement composites exhibit the highest flexural strength when compared to their non-treated counterparts. In addition, mechanical properties are improved as a result of CNC addition. An optimum replacement of ordinary Portland cement with 1wt% CNC is observed through reduced porosity and increased density, flexural strength and fracture toughness in treated hemp fabric-reinforced nanocomposite. It is shown that CNC behaves not only as a filler to improve the microstructure, but also as the activator to facilitate the pozzolanic reaction and thus improved the adhesion between the treated hemp fabric and the matrix.

Thermal and mechanical properties of NaOH treated hemp fabric and calcined nanoclay-reinforced cement nanocomposites

Cement nanocomposites reinforced with hemp fabrics and calcined nanoclay (CNC) have been fabricated and investigated. CNC is prepared by heating nanoclay (Cloisite 30B) at 900 °C for 2 h. The influences of CNC dispersion on the mechanical properties and thermal properties of these composites have been characterized in terms of porosity, density, water absorption, flexural strength, fracture toughness, impact strength and thermal stability. The microstructure is investigated using Quantitative X-ray Diffraction Analysis (QXDA) and High Resolution Transmission Electron Microscopy (HRTEM). The effects of alkali (NaOH) treatment of hemp fabric on the mechanical properties of hemp fabric-reinforced cement composites with different fabric contents of 4.5, 5.7, 6.9 and 8.1 wt% are also investigated. Results show that the optimum hemp fabric content is 6.9 wt% (i.e. 6 fabric layers). Results also indicated that physical, mechanical and thermal properties were enhanced due to the addition of CNC into the cement matrix and the optimum content of CNC was 1 wt%. The treated hemp fabric-reinforced nanocomposites containing 1 wt% CNC exhibited the highest flexural strength, fracture toughness, impact strength and thermal stability by virtue of good fibre–matrix interface. This environmentally friendly nanocomposite can be used for various construction applications such as ceilings and roofs.

Effect of textile surface treatment on the flexural properties of textile-reinforced cementitious composites

In this study, the influence of a new surface treatment of the textiles to reinforce concrete materials has been investigated. The short polyvinyl-alcohol fibers were attached to the textile surface to achieve a fluffy textile. The flexural and peel tests were employed to study the effectiveness of the surface treatment on the carbon textile. As a result, the applied treatment considerably improved the bond properties between the textile and cement matrix up to 43%, and enhanced load-bearing capacity of textile-reinforced cementitious composites by up to 56%.

Form finding methodology for force-modelled anticlastic shells in glass fibre textile reinforced cement composites

The reinforcement of a specifically developed fine grained cement matrix with glass fibre textiles in high fibre volume fractions creates a fire safe composite that has–besides its usual compressive strength–an important tensile capacity and omits the need for any steel reinforcement. Strongly curved shells made of textile reinforced cement composites (TRC) can cover medium (up to 15 m) span spaces with three times smaller shell thicknesses than conventional steel-reinforced concrete shells. This paper presents a methodology to generate force-modelled anticlastic shell shapes that exploit both the tensile and compressive load carrying capacities of TRC. The force-modelling is based on the dynamic relaxation form finding method developed for gravity (in this case self-weight) loaded systems. The potential of the presented methodology to develop structurally sound anticlastic shell shapes is illustrated by four case studies.

Dynamic tensile testing of fabric–cement composites

Dynamic tensile tests were conducted using a high speed servo-hydraulic testing machine on three types of fabric reinforced cement composites. The high speed testing procedure and data processing method are presented. Quasi-static tests were also conducted on the composites. Effects of strain rate on the mechanical properties of fabric–cement composites are noted. A good correlation was found between the properties of the fabrics and the composites, with the carbon fabric exhibiting the highest strength and ductility performance in high speed tensile tests. The differences in tensile behavior of the various composites were correlated with the differences in the role of the fabric materials. Composites tested under high speed loading exhibited different responses as compared to similar composites tested under quasi-static condition.

Low velocity flexural impact behavior of AR glass fabric reinforced cement composites

Fabric–cement composites developed using the pultrusion production process have demonstrated impressive tensile and flexural properties. For instance fabric reinforced composites with bonded Alkali Resistant (AR) glass fabrics exhibit strain-hardening behavior, tensile strength in the range of 20–25 MPa, and strain capacity of the order of 2–5% under static conditions. Properties of these composite systems were investigated under three point bending conditions using an instrumented drop weight impact system. Samples were studied from the viewpoint of the variations of impact load, deflection response, acceleration and absorbed energy. Development of the testing system in terms of components and acceleration response are discussed in detail. Methods of the impact load measurement using three different ways of acceleration response, piezoelectric load washer and conventional strain gage based load cell are discussed. Cement composites with two different fabric contents and four different drop heights of hammer (dropping mass) were tested. Experimental results indicate that for the same drop height, the stiffer beam type specimens have a lower ultimate deflection but a higher load carrying capacity than the plate type specimens. The maximum flexural stress and absorbed energy of composites increase with drop height. In beam specimens, complete fracture does not take place as cracks form and close due to rebound and significant microcracking in the form of radial fan cracking is observed, whereas interlaminar shear is the dominant failure mode in the plate specimens.

Geometrical and mechanical aspects of fabric bonding and pullout in cement composites

Fabric reinforced cement composites are a new class of cementitious materials with enhanced tensile strength and ductility. The reinforcing mechanisms of 2-D fabric structures in cement matrix are studied using a fabric pullout model based on nonlinear finite difference method. Three main aspects of the composite are evaluated: nonlinear bond slip characteristic at interface; slack in longitudinal warp yarns, and mechanical anchorage provided by cross yarn junctions. Parametric studies of these key parameters indicate that an increase in the interfacial bond strength directly increases the pullout strength. Grid structures offering mechanical anchorage at cross yarn junctions can substantially increase the pullout resistance. Presence of slack in the yarn geometry causes an apparently weaker and more compliant pullout response. The model was calibrated using a variety of test data on the experimental pullout response of AR-Glass specimens, manufactured by different techniques to investigate the relative force contribution from bond at interface and from cross yarn junctions of alkaline resistant glass fabric reinforced cement composites.

Properties of Fabric–Cement Composites made by Pultrusion

Practical manufacturing and use of thin cement-based elements composites require an industrial cost-effective production process in addition to proper reinforcement materials to improve the tensile and flexural performance. Reinforcement by means of fabric materials is an alternative to the use of short fibers. The objective of this study was to investigate use of pultrusion technique as a cost-effective method for the production of thin-sheet fabric-reinforced cement composites. Woven fabrics made from low modulus polypropylene (PP) and glass meshes were used to produce the pultruded cement composites. The influence of fabric type, PP and glass, processing method, pultrusion vs. cast and cement-based matrix modification were examined. Tensile and pullout tests as well as Scanning Electron Microscopy (SEM) observations were used to examine the mechanical, bonding and microstructure properties of the different composites. The rheology of the mix was correlated with the mechanical behavior of the pultruded composites. The tensile behavior of the pultruded fabric–cement components exhibited strain hardening behavior. The best performance was achieved for the PP pultruded composites.

Pultruded Fabric-Cement Composites

The use of reinforcement in thin cement-based elements is essential to improve the tensile and flexural performance. The reinforcements can be either short fibers or continuous reinforcements, in a fabric form. Practical use of fabric-cement composites requires an industrial, cost-effective production process. The objective of this study was to develop the pultrusion technique as an industrial, cost-effective production method of prefabricated thin-sheet fabric-reinforced cement composites. Woven fabrics made from low-modulus polyethylene and glass meshes were used to produce the pultruded cement composites. The influence of fabric type, cell opening, application of pressure during casting, and cement-based matrix modification were examined. The tensile strength and ductility of the pultruded fabric-cement components were found to be relatively high, exhibiting strain hardening behavior even for fabrics with low modulus of elasticity. The best performance was achieved from glass fabric composites with a high content of fly ash. The mechanical properties were significantly affected by the matrix formulation, rheology of the matrix, and the intensity of the pressure applied after the pultrusion process. The promising combination of fabric reinforcement in cement composite products using the pultrusion process is expected to lead to a new class of high-performance fabric-cement composite materials.

Fabric structure and its reinforcing efficiency in textile reinforced cement composites

In polymer matrices reinforced with fabrics, the effectiveness of the reinforcement is reduced when the yarns do not maintain a straight geometry. In cement composites, this concept may not be adequate since the nature of the interaction between the cement matrix and the fabric and its individual yarns is more complex, as concluded from pullout tests. The present paper discusses the bulk properties and geometrical characteristics of textile fabrics that need to be considered in order to predict the performance of cement composites reinforced with textile fabrics. It was found that the geometry of a given fabric could enhance the bonding and enable one to obtain strain hardening behavior from low modulus yarn fabrics, due to the special shape of the yarn induced by the fabric. On the other hand, variations of the geometry in a fabric could drastically reduce the efficiency, resulting in a lower strengthening effect of the yarns in the fabric, relative to single yarns not in a fabric form. Therefore, in cement composites the fabrics cannot be viewed simply as a means for holding together continuous yarns to be readily placed in the matrix, as is the case in composites with polymer matrix.