Glass Fibre Reinforced Cement Research Articles

The Influence of Additions in the Use of Glass Fibre Reinforced Cement as a Construction Material

Although in recent years glass fibre reinforced cement (GRC) has been used in buildings and infrastructure, its application in structural elements has been somewhat restricted due to the worsening of its mechanical properties with ageing and the limited data available related with its fracture energy. With the aim of developing existing knowledge of GRC, the fracture energy in an in-plane and out-of-plane direction of the panel has been obtained. Three types of GRC with different formulations have been tested. The results showed that the fracture energy of a GRC with a 25% addition of a pozzolanic admixture is 40% and 8% higher than a standard GRC in, respectively, in-plane and out-of-plane directions. Similarly, an addition of 25% of thermal-treated kaolin to a standard GRC increases its fracture energy up to 490% and 400%, to the corresponding orientation. The use of digital image correlation (DIC) in the fracture test analysis has permitted a description of the damaging patterns and explanation of the behaviours identified in the fracture tests performed. The multi-cracking process that appears explains the higher fracture energy found in the GRC with an addition of 25% of the aforementioned thermal-treated kaolin. The analysis performed by means of DIC and the results obtained showed GRC with an addition of 25% of thermal-treated kaolin to be the most suitable formulation for possible future structural applications with a short life span in horizontal and vertical elements.

Microstructure of interface between fibre and matrix in 10-year aged GRC modified by calcium sulfoaluminate cement

Time-dependent property changes in glass fibre reinforced cement (GRC) mainly result from a combination of the alkalinity of the matrix and densification of the matrix (e.g. due to calcium hydroxide precipitation) within and around the glass fibre strands. The microstructure of the interface between matrix and fibres in GRC has a significant impact on its durability. This paper describes a study of two GRC formulations (with OPC, and OPC plus calcium sulfoaluminate based matrices) aged for 10years at 25°C. Thin-section petrography (TSP) and SEM are used to compare the microstructure of both polished surfaces and fractured surfaces. The aged OPC/GRC demonstrates significantly brittle behaviour with substantial densification of C–S–H/CH intermixture occurring around glass fibres. In contrary, the aged composite made with the OPC plus calcium sulfoaluminate shows greatly retained toughness, accompanied by considerably flexible interfacial and interfilamentary areas around the glass fibres.

Ultrasonic characterization of GRC with high percentage of fly ash substitution

New applications of non-destructive techniques (NDT) with ultrasonic tests (attenuation and velocity by means of ultrasonic frequency sweeps) have been developed for the characterization of fibre-reinforced cementitious composites. According to new lines of research on glass-fibre reinforced cement (GRC) matrix modification, two similar GRC composites with high percentages of fly ash and different water/binder ratios will be studied. Conventional techniques have been used to confirm their low Ca(OH)2 content (thermogravimetry), fibre integrity (Scanning Electron Microscopy), low porosity (Mercury Intrusion Porosimetry) and good mechanical properties (compression and four points bending test). Ultrasound frequency sweeps allowed the estimation of the attenuation and pulse velocity as functions of frequency. This ultrasonic characterization was correlated successfully with conventional techniques.

Multimodal analysis of GRC ageing process using nonlinear impact resonance acoustic spectroscopy

Glass fibre Reinforced Cement (GRC) is a composite material composed of Portland cement mortar with low w/c (water/cement) ratio and high proportion of glass fibres. This material suffers from the ageing process by losing its strength with time because of its exposure to severe weather conditions. Ageing process damages the fibre surface and decreases the mechanical properties of the structural components made of this material. It reduces the elastic modulus and toughness of GRC. Fracture toughness is traditionally measured by four point bending tests. In a previous study by the authors it was observed that ageing related deterioration or damage of GRC could be monitored by Non Destructive Testing (NDT) techniques such as Non-linear Impact Resonance Acoustic Spectroscopy (NIRAS) and other ultrasonic techniques. The scope of this paper is to corroborate previous investigations and offer early damage detection capability by generating more experimental data points by optimizing location of the point of strike and thus generating more resonance vibration modes in NIRAS tests.

Analysis of fracture tests of glass fibre reinforced cement (GRC) using digital image correlation

In the last decades GRC has been used in buildings and infrastructure, although there is insufficient data available related with its fracture energy. In order to expand knowledge in the field, the fracture energy in perpendicular and parallel directions with respect to the fibres is obtained. Three types of GRC with different formulations are tested. The results show that the fracture energy of a GRC with a 25% addition of a pozzolanic admixture is 40% and 8% higher than a standard GRC in, respectively, each orientation. Similarly, an addition of 25% of heat-treated kaolin to a standard GRC increases its fracture energy up to 490% and 400% depending on the given orientation. Moreover, the applicability of digital image correlation (DIC) to GRC fracture tests is shown. The use of DIC enables a description of the damaging patterns and explanation of the behaviours identified in the fracture tests performed.

Investigation of Glass Fibre Reinforced Cement (GFRC) Material Exposed to High Temperatures

In this paper we present the tests of high temperatures resistances of glass fibre cement plates. The aim of the research was to determine the values of tensile strength in bending for samples subjected to annealing at temperatures 200, 300, 400 and 500 °C in endurance at the highest temperature level for 24 hours. The bending strength was performed according to the norm EN 1170-4. The thermal dilatometric analysis was performed in the temperatures till 540 °C.

Self-cleaning and depollution of fiber reinforced cement materials modified by neutral TiO2/SiO2 hydrosol photoactive coatings

Environmental pollution has an evidently adverse impact on the buildings that are constructed by the glass fiber reinforced cement (GRC) materials. In the present work, the stable, neutral TiO2/SiO2 hydrosols were prepared by using the Ti(SO4)2 as titanium source, HNO3 as peptizing agent, and SiO2 as stabilizer through a simple and low cost process. The morphologies and structures of TiO2/SiO2 hydrosol were further characterized by the TEM, SEM, XRD, and FTIR measurement. In the synthetic hydrosol, lots of nanoparticles with the diameters in the range of 10–20nm can be observed. TiOSi band were formed, as observed from the FTIR spectrum. The Na2O·SiO2 was detected from the SEM. After drying the TiO2/SiO2 hydrosol, the XRD shown that the TiO2 has an anatase structure and the SiO2 is amorphous. The TiO2/SiO2 hydrosol can be compactly coated on the GRC surface due to the existence of Na2O·SiO2 binder and exhibited high photocatalytic activity and stability in the degradation of Rhodamine B.

Nondestructive Monitoring of Ageing of Alkali Resistant Glass Fiber Reinforced Cement (GRC)

Glass fiber reinforced cement (GRC) is a composite material made of portland cement mortar and alkali resistant (AR) fibers. AR fibers are added to portland cement to give the material additional flexural strength and toughness. However, ageing deteriorates the fibers and as a result the improvement in the mechanical properties resulted from the fiber addition disappears as the structure becomes old. The aim of this paper is monitoring GRC ageing by nondestructive evaluation (NDE) techniques. Two different NDE techniques—(1) nonlinear impact resonant acoustic spectroscopy analysis and (2) propagating ultrasonic guided waves—are used for this purpose. Both techniques revealed a reduction of the nonlinear behavior in the GRC material with ageing. Specimens are then loaded to failure to obtain their strength and stiffness. Compared to the un-aged specimens, the aged specimens are found to exhibit more linear behavior, have more stiffness but less toughness. Finally, undisturbed fragments on the fracture surface from mechanical tests are inspected under the electron microscope, to understand the fundamental mechanisms that cause the change in the GRC behavior with ageing.

Dynamic performance characteristics of an innovative Hybrid Composite Floor Plate System under human-induced loads

This study explored the dynamic performance of an innovative Hybrid Composite Floor Plate System (HCFPS), composed of Polyurethane (PU) core, outer layers of Glass–fibre Reinforced Cement (GRC) and steel laminates at tensile regions, using experimental testing and Finite Element (FE) modelling. Experimental testing included heel impact and walking tests for 3200mm span HCFPS panels. FE models of the HCFPS were developed using the FE program ABAQUS and validated with experimental results. HCFPS is a light-weight high frequency floor system with excellent damping ratio of 5% (bare floor) due to the central PU core. Parametric studies were conducted using the validated FE models to investigate the dynamic response of the HCFPS and to identify characteristics that influence acceleration response under human induced vibration in service. This vibration performance was compared with recommended acceptable perceptibility limits. The findings of this study show that HCFPS can be used in residential and office buildings as a light-weight floor system, which does not exceed the perceptible thresholds due to human induced vibrations.

Flexural performance of an innovative Hybrid Composite Floor Plate System comprising Glass–fibre Reinforced Cement, Polyurethane and steel laminate

This study explored the flexural performance of an innovative Hybrid Composite Floor Plate System (HCFPS), comprised of Polyurethane (PU) core, outer layers of Glass–fibre Reinforced Cement (GRC) and steel laminates at tensile regions, using experimental testing and Finite Element (FE) modelling. Bending and cyclic loading tests for the HCFPS panels and a comprehensive material testing program for component materials were carried out. HCFPS test panel exhibited ductile behaviour and flexural failure with a deflection ductility index of 4. FE models of HCFPS were developed using the program ABAQUS and validated with experimental results. The governing criteria of stiffness and flexural performance of HCFPS can be improved by enhancing the properties of component materials. HCFPS is 50–70% lighter in weight when compared to conventional floor systems. This study shows that HCFPS can be used for floor structures in commercial and residential buildings as an alternative to conventional steel concrete composite systems.

Influence of curing conditions on durability of alkali-resistant glass fibres in cement matrix

Glass fibres in concrete material often increase the flexural strength. However, these fibres when in contact with cement are altered by alkali reactions due to the presence of portlandite. This study presents the results of investigation to show the effect of curing conditions on the durability of alkali-resistant glass fibres in cement matrix. Test results show that even alkali resistant fibres treated with zirconium oxide present the same degradation phenomenon. They also show that the nature of the cement has a large influence on the protection of the fibres: the Portland CEM II is less damaging than the CEM I. The substitutions of a part of cement by silica fume gave no substantial improvements to the mechanical strength of the glass fibre reinforced cement (GFRC). However, the observed microstructures in the samples show that the degradation is weakened with the addition of silica fumes. The analytical techniques used in this study are scanning electron microscope (SEM) and X-ray diffraction.

Failure and impact behavior of facade panels made of glass fiber reinforced cement(GRC)

GRC is a cementitious composite material made up of a cement mortar matrix and chopped glass fibers. Due to its outstanding mechanical properties, GRC has been widely used to produce cladding panels and some civil engineering elements. Impact failure of cladding panels made of GRC may occur during production if some tool falls onto the panel, due to stone or other objects impacting at low velocities or caused by debris projected after a blast. Impact failure of a front panel of a building may have not only an important economic value but also human lives may be at risk if broken pieces of the panel fall from the building to the pavement. Therefore, knowing GRC impact strength is necessary to prevent economic costs and putting human lives at risk. One-stage light gas gun is an impact test machine capable of testing different materials subjected to impact loads. An experimental program was carried out, testing GRC samples of five different formulations, commonly used in building industry. Steel spheres were shot at different velocities on square GRC samples. The residual velocity of the projectiles was obtained both using a high speed camera with multiframe exposure and measuring the projectile’s penetration depth in molding clay blocks. Tests were performed on young and artificially aged GRC samples to compare GRC’s behavior when subjected to high strain rates. Numerical simulations using a hydrocode were made to analyze which parameters are most important during an impact event. GRC impact strength was obtained from test results. Also, GRC’s embrittlement, caused by GRC aging, has no influence on GRC impact behavior due to the small size of the projectile. Also, glass fibers used in GRC production only maintain GRC panels’ integrity but have no influence on GRC’s impact strength. Numerical models have reproduced accurately impact tests.

Analysis of glass fiber reinforced cement (GRC) fracture surfaces

Glass fiber reinforced cement (GRC) is a composite material produced by the union of a cement mortar matrix and chopped glass fibers. Its good mechanical properties deteriorate with time. This phenomenon has been studied performing a tensile test program on both young and aged samples of GRC produced by using different chemical additives. Once the tests were carried out, a microstructural analysis of fracture surfaces was performed using a scanning electronic microscope (SEM). Pictures taken showed that the addition of metakaolin enables more fibers to be pulled out from the matrix instead of being broken in aged GRC samples. However, the increase in the number of such fibers pulled out did not prevent the embrittlement of GRC. Also, all the other chemical additions used did not show any improvement in the mechanical properties of GRC.

Strengthening Masonry Arches with Composite Materials

The aim of this study was to compare the effects of strengthening masonry arches using two different composite materials. To this end, an experimental analysis was carried out on models of arches that were first damaged, then strengthened by applying composite material sheets to the surface of the intrados, and last, subjected to a loading process until the point of collapse. One arch was strengthened with carbon fiber-reinforced polymer, the other with glass fiber-reinforced cement matrix. Results collected during the experimental analysis were significant in assessing the capability to support horizontal load, in increasing the collapse load, stiffness, and ductility, and in assessing the different fracture patterns and collapse modes of the arches strengthened with different fiber-reinforced composites. The comparison will be useful for establishing the physical-mechanical and aesthetic compatibilities between the original construction and the strengthening matrix polymeric or cementitious, particularly with reference to the safeguarding of historical buildings.

New applications of calcium sulfoaluminate cement

This paper presents four innovative utilizations of calcium sulfoaluminate (CSA) cement:–development of concrete with high early strength: 40 MPa, 6 h after its preparation, and higher than 55 MPa after 24 h,–design of self-leveling screed with limited curling, when unbonded to its support,–design of self-leveling topping mortar presenting the following properties: time of workability higher than 30 min, set within 75 min, and low drying shrinkage (<250μm/m).–glass-fiber-reinforced cement (GFRC) composites that can be demolded 4 h after casting and present high ductility and durability after aging in different weathering conditions.

Enhancement of aging resistance of glass fiber reinforced cement

Long-term weathering tests revealed that glass fiber-reinforced cement (GFRC) might exhibit tensile strength reduction and ductility loss with aging. The main goal of this research was to assess the effectiveness of polyvinyl alcohol (PVA) powder in enhancing the durability characteristics of GFRC sheets. Accelerated aging was achieved by using low pressure steam curing. The strength and ductility of GFRC sheets were measured by the direct tension test. The test results show that the incorporation of PVA powder into GFRC improves the mechanical behavior and changes the failure mode from brittle to ductile. To investigate the mechanism of the enhancement, the fiber-matrix interface was examined by polarizing optical microscopy and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDAX). It was found that the addition of the PVA powder results in the deposition of a polymeric film on the fiber surface and thus prevented the accumulation of calcium hydroxide in the interfacial zone. The use of the PVA powder led to a more ductile interfacial microstructure and to better bonding between fiber and matrix, which is believed to be responsible for the tensile property enhancement.

Development of a New Alkali Resistant Coating

The effect of different new sol-gel BaO—TiO2—SiO2 and CaO—BaO—TiO2—SiO2 coatings on long-term durability of glass fiber reinforced cement (GRC) was examined. Flexural strength of GRC was measured after curing for 7 to 150 days. Significant improvement was observed for coated GRC in this study and discussed in terms of the hydrate formation at interface. Concerned with the alkali resistance, CaO—BaO—TiO2—SiO2 coating was more effective than BaO—TiO2—SiO2 coating. In special, the 10CaO—10BaO—60TiO2—20SiO2 coating, prepared by sol-gel method, was recommended for the highest flexural strength of GRC and least corrosion at surface of E-glass fiber.

Preliminary investigations of the dimensional stability of super-critically carbonated glass fibre reinforced cement

The dimensional changes occurring during the super-critical carbonation of glass fibre reinforced cement (GRC) and its subsequent environmental exposure have been investigated. Sheet samples, with embedded stainless steel pins 200 mm apart, were fabricated and then subjected to super-critical carbonation. Test coupons were subsequently exposed to a range of environments including continuous immersion in water, cyclic wetting/drying and outdoor exposure. The super-critical carbonation process resulted in a slight expansion of GRC. This is contrary to the behaviour observed during natural carbonation where irreversible shrinkage normally occurs. Exposure to the various environments mentioned above showed that super-critically carbonated samples had much greater resistance to swelling and shrinkage than uncarbonated specimens. These observations are particularly significant in relation to the practical application of GRC in environments of fluctuating moisture content.

Enhancement of durability of glass fiber-reinforced cement with PVA

Enhancement of durability of glass fiber-reinforced cement with PVA

Enhancement of durability of glass fiber-reinforced cement with PVA

The main thrust of this research was to determine the effectiveness of polyvinyl alcohol (PVA) powder in enhancing the durability of short GFRC materials. Accelerated aging of the materials was achieved through low\|pressure steam curing in a moist chamber. The strength and ductility of GFRC were measured by the direct tension test, which showed that incorporation of PVA powder into GFRC could improve its mechanical behaviour and turn it from brittle to ductile. To investigate the mechanism of the tensile strength enhancement, the fiber\|matrix interface was examined by polarizing optical microscopy and scanning electron microscopy (SEM) with energy dispersive X\|ray analysis (EDAX). It was found that PVA powder tended to migrate to the fiber\|matrix interfacial zone and thus prevented the accumulation of calcium hydroxide in this area. PVA film around the fiber resulted in a more ductile interfacial microstructure and better bonding between fiber and matrix, which should be responsible for enhancing the tensile property and preventing the aging of GFRC. Furthermore, PVA powder reduced the microhardness and brittleness at the interface.