Search Results (7)

Geopolymer, a sustainable alternative to ordinary Portland cement (OPC), offers reduced embodied energy, lower carbon emissions, enhanced durability, eco-compatibility, and waste valorization potential. In confining structural members, geopolymer still has limitations with respect to its brittleness and other properties. Enhancing the properties of geopolymer by adding banana fibers (BF) and fly ash (FA) to form banana geotextile-reinforced geopolymer mortar (BGT-RGM) as confining material, is investigated in this experimental study. BGT-RGM is a textile-reinforced mortar with varying thickness of BF-reinforced geopolymer mortar (BFRGM) through NaOH-treated 10 mm BFs and 2 mm banana geotextile (BGT) having varied grid spacings. To develop BGT-RGM, the physical, mechanical, and chemical properties of the BFs were determined, while BFRGMs were evaluated for compressive and dog-bone tensile strengths, workability, scanning electron microscopy (SEM) imaging, and thermogravimetric analysis (TGA). The BGT-RGM-confined and unconfined concrete were evaluated, and the strength variations were imparted by the confinement as reflected on the stress-strain curves. The local crack formation mode of failure was also determined through crack patterns during an axial load test. The BGT-RGM with 20 mm thickness of BFRGM with 15 mm and 20 mm geotextile grid spacings, exhibited 33.3% and 33.1% increases in strength, respectively. Future investigations towards the development and application of BGT-RGM are also discussed. Full article

Old structures that are made of adobe or brick walls are usually unreinforced and not designed for lateral forces. In-plane loads applied to unreinforced masonry walls (URM) are the usual cause of damage and failure of old buildings. In this research, small unreinforced brick masonry wallettes, 350 mm × 350 mm and 50 mm in thickness, are strengthened using bamboo fiber textile and plastered to the face of the walls using short bamboo fiber-reinforced geopolymer mortar. The wallettes are subjected to diagonal shear tests as described by ASTM E519 to investigate the in-plane shear performance of the strengthening method. The performances of 5 wallettes strengthened on one-side with mortar only, 5 wallettes on both-sides with mortar only, 5 wallettes with textile plastered on one-side only, and another 5 wallettes with textile plastered on both-sides, are compared to 5 control specimens without any strengthening. It is observed that the wallettes strengthened on one side and both sides with textile yield an increase in shear of about 24% and 35% in average, respectively. Failure modes show that the usual failure for URM is running bond failure and for strengthened URM is columnar failure. The implications of the results can be used in developing textile-reinforced geopolymer mortar systems to strengthen URM walls. Full article

Textile-reinforced mortar (TRM) is an effective method for confining concrete elements to elevate the axial load resistance and upgrade the overall performance of concrete. TRM is a promising alternative to carbon-fiber-reinforced polymers (CFRP) which are commonly used to strengthen concrete and are known to be expensive since they require a huge amount of energy in processing these materials. Green technologies can be applied in this process, following the same TRM principles of confinement, replacing conventional cement or epoxy-based mortars and synthetic textiles towards sustainable concrete strengthening technology. This is through the utilization of a geopolymer mortar reinforced with short banana fibers (BF) and long BFs as textiles. Geopolymer mortar presented in this paper is composed of fly ash and silica fume as the binder, sand as the filler, sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) as the activator and BFs as the reinforcement and textile. Geopolymerization generates significantly less carbon dioxide (CO₂) while BFs are known for having attractive mechanical properties, are cost effective and abundant in nature, and thus the use of this fiber will significantly minimize the huge waste produced from banana plantations after a one-time fruit harvest. The geotextile or geogrid used to wrap the concrete cylinder samples is made up of 2 mm-long BF yarns with weights ranging from 150 to 450 grams per square meter that varies with grid sizes from 10 mm, 15 mm to 25 mm for both orthogonal directions considering the lightweight characteristic of BFs. Twelve TRM designs were used to strengthen the concrete cylinders with three samples each. TRM design parameters vary in the thicknesses of the geopolymer mortar covering and the size of the geotextile grids. Eighteen of the geotextiles used were coated with a polymer to protect the fibers while the other eighteen geotextiles remained uncoated. A total of thirty-nine concrete cylinders with 150 mm base diameter and 300 mm height cured within 28 days were prepared, for which 36 cylinders were confined with green TRM with different parameters while three of the plain concrete cylinders served as the control specimens. This is to maximize the investigation on the potential of green TRM in confining concrete and to determine the variations in compressive strengths and mode of failures of confined and unconfined concrete specimens. Results highlighted notable enhancement in the mechanical properties of the modified plain concrete after 28 days of TRM curing using a universal testing machine (UTM). Likewise, a confinement theory of the optimum TRM design was modeled mathematically to evaluate the effects of concrete confinement and overall load carrying capacity enhancement gained from additional strength transferred by the TRM to the concrete element. Full article

This paper presents an experimental research on the mechanical properties of the hybrid composite thin-plates of the short basalt fibers (CBFs)/carbon textile-reinforced geomortar. The effect of fiber contents and lengths of CBFs on the flexural behavior of carbon textile-reinforced geopolymer specimens (TRGs) was investigated by the four-point flexural strength and Charpy impact test. The experimental results of hybrid TRGs, on the one hand, were compared with reference TRGs, without CBF addition; on the other hand, they were compared with the results of our previous publication. According to the mixing manner applied, fresh geomortar indicated a marked reduction in workability, increasing the CBF loading. Furthermore, using CBFs with lengths of 12 mm and 24 mm makes it easy to form the fiber clusters in geomortar during mixing. According to all the CBF loadings used, it was found that TRGs showed a significant improvement in both static and dynamic flexural strength. However, the failure mode of these TRGs is similar to that of the reference TRGs, described by the process of fiber debonding or simultaneously fiber debonding and collapse. In comparison with our prior work results, neither the CBF dose levels nor the fiber lengths used in this work have yielded a positive effect on the failure manner of TRGs. According to the results of the Charpy impact test, this reveals that the anchoring capacity of textile layers in geomortar plays an important role in specimens’ strength. Full article

Basalt fiber is a novel type of inorganic fiber which is produced from the extrusion of natural vocalnic basalt rocks through their melting process at high temperature. So the quality and strength characteristics of basalt fiber depend mainly on both the quality of raw material and manufacturing processing. Basalt fabric-reinforced cementitious composites (FRCM) are a novel composite and an extensive scientific investigation is still ongoing for geopolymer composite. Based on three types of basalt textile with respect to various net sizes, the aim of this paper is to evaluate the flexural performance of basalt textile-reinforced geopolymer composite through the four-point bending test. The specimens of rectangular form with the dimension of 400 × 100 × 15 mm³, reinforced with one to four layers of each type of basalt textile, were produced. They were then tested at the age of about 40 days after casting. On the other hand, the number of the specimens reinforced with four layers were considered to assess the mechanical strength of the specimens at longer periods of ageing time (60, 90, 150, 180 days). The experimental results showed that with the increasing number of reinforcing layers, the specimens significantly improved the mechanical strength, except for those reinforced with basalt textile of big net size. The specimens reinforced with basalt textile of big net size had no impact on post-crack mechanical strength, however, it helps to arrest the catastrophic brittle failure of the specimens; the failure of these specimens is due to localization of first crack. When the specimens were exposed to the further ageing times, the mechanical strength of the specimens were decreased over time. All the reinforced specimens have the same failure mode by flexural failure due to the rupture of fiber yarn in matrix, and no debonding of fiber yarn or a gradual peeling process of mortar matrix happened during testing. Full article

Textile-reinforced Portland cement-based concrete has been researched and developed over the last few decades. It was widely used in a different range of applications, such as repair and/or strengthening of structural elements, thin walls, lightweight structures, façade elements, and others. Due to its varied application, this study aims to develop the carbon textile-reinforced geopolymer composite. Specimens of rectangular form with the dimensions of 400 × 100 × 15 mm³, reinforced with carbon textile, were produced. Four-point bending test was used to evaluate the effect of carbon textile on the mechanical strength of reinforced geopolymer composite based on the three factors: the different mortar compositions corresponding to the addition of the chopped basalt fiber (BF), the number of carbon textile layers, and the different thicknesses of the mortar cover layer. Besides that, a small part of the pull-out test was also considered to assess the adhesion strength at the interface between carbon textile and geopolymer mortar. The experimental results from the four-point bending test showed that the mechanical strength of composite specimens increased when the content of the chopped basalt fiber increased. With the increasing number of the textile layers, the specimens improved the flexural strength significantly. However, the flexural toughness of the specimens reinforced with three textile layers did not improve, as compared to those reinforced with two textile layers. The experimental results for the specimens related to the mortar cover thicknesses indicated that specimens with the mortar cover thickness of 2 mm provide the best strength. The experimental results from the pull-out tests showed that all the specimens have the same failure mode by slipping of the fiber yarn from the matrix. Full article

Textile reinforced mortar or concrete, a thin cementitious composite reinforced by non-corrosive polymer textile fabric, was developed and has been researched for its role on repair and strengthening of reinforced concrete (RC) structures. Due to embedment of polymeric textile fabric inside the cementitious matrix, many researchers argued the superiority of this technology than the externally bonded fiber reinforced polymer (FRP) sheet in RC in terms of prevention of debonding of FRP and durability in fire. However, due to use of cement rich matrix the existing development of textile reinforced concrete (TRC) need to be more environmental friendly by replacing cement based binder with geopolymeric binder. This paper presents a first study on the flexural behavior of alkali resistant glass fiber textile reinforced geopolymer (TRG). In this study, two types of geopolymer binder is considered. One is fly ash based heat cured geopolymer and the other is fly ash/slag blended ambient air cured geopolymer binder. Both geopolymer types are considered in the TRG and the results are benchmarked with the current cement based TRC. The effect of short polyvinyl alcohol (PVA) fiber as hybrid reinforced with alkali-resistant (AR) glass fiber textile on the flexural behavior of above TRC and TRGs is also studied. Results show deflection hardening behavior of both TRGs with higher flexural strength in heat cured TRG and higher deflection capacity at peak load in ambient air cured TRG. The increase in PVA fiber volume fraction from 1% to 1.5% did not show any improvement in flexural strength of both TRGs although TRC showed good improvement. In the case of deflection at peak load, an opposite phenomenon is observed where the deflection at peak load in both TRGs is increased due to increase in PVA fiber volume fractions. Full article