Bamboo fiber textile reinforced geopolymer system in strengthening unreinforced masonry brick walls

Old structures such as historic churches, old school buildings, and arches are often constructed with unreinforced masonry walls (URM), which typically consist of adobe or brick walls. The design of most URM is for gravity loads only and not intended to resist lateral forces induced by seismic activities. Most URM walls fail under in-plane shear. The main objective of this study is to provide an acceptable externally bonded strengthening method for URM brick walls. To maximize the impact of the study in preserving lives, environmentally friendly materials such as mill-scale (MS) waste, flyash (FA), and bamboo fibers (BF), were used to develop the strengthening system. MS powder was used to partially replace FA in geopolymer-making with optimum 1:5 MSto- FA ratio. BF extracted using 5% sodium hydroxide solution from Kawayan Tinik, and treated with additional 10% aluminum sulfate solution, were used as short fiber reinforcement and as BF geotextile to reinforce the MS-FA based geopolymer mortar that is used as the plastering for the strengthening system. Wallette size specimens, 350 mm x 350 mm, were subjected to diagonal shear tests in accordance with modified ASTM E519 guidelines. By strengthening the wallettes on both faces with the geotextile reinforced geopolymer system, their shear capacity improved, resulting in an average increase of 55.78% in the amount of shear force the wallettes can resist. The wallettes that were strengthened on one side only also improved with an average increase of 33.20% in average shear force resisted. The deformability of the wallettes, expressed as pseudo-ductility ratio, improved up to 1.55 ratio compared to 1.04 ratio of the control samples. This suggests that the specimen underwent additional deformation after the initial cracking, indicating that the strengthening method contributes in improving the overall shear performance of the strengthened URM wallette. The resulting modulus of rigidity of each strengthening method and tensile strength of BF textile were used as base values for ACI 549.4R analytical models to compute the nominal shear capacity of the wallettes. The computed nominal shear capacities present the shear contributions of the URM and of the proposed strengthening method

Microstructure and mechanical performance of bamboo fiber reinforced mill-scale—Fly-ash based geopolymer mortars

Natural fiber reinforcement in cementitious matrices is being explored to provide an environment-friendly solution for lowering the overall carbon footprint of construction materials while giving the matrix much-needed tensile strength. Short bamboo fibers extracted from Bambusa blumeana or Kawayan tinik using 5% sodium hydroxide solution and treated with 10% aluminum sulfate solution are used to reinforce zero-cement geopolymer mortars. Bamboo fibers with varying lengths of 10 mm, 20 mm, and 30 mm are mixed with mill-scale – fly ash-based geopolymer in varying 0%, 0.5%, 1%, 1.5%, and 2% fiber loading per weight of specimen sample. Compressive strength and split tensile strength tests are administered to small cylinder samples, 50 mm in diameter by 100 mm in height, in accordance with ASTM C780. An optimum fiber length of 20 mm and fiber loading of 1.4% by weight is determined using Response Surface Methodology (RSM). The addition of bamboo fibers increased the unconfined compressive strength up to 292.41% compared to specimens without bamboo fibers. The split tensile strength also improved by up to a 355.82% increase compared to control samples. The corresponding high-strength and low-strength samples are also subjected to Fourier-transform Infrared Spectroscopy – Attenuated Total Reflectance (FTIR-ATR) to investigate and compare the stretching of bands between the raw materials and tested specimens. Scanning Electron Microscopy – Energy Dispersive X-Ray analysis (SEM-EDX) is used to show microscopic images and the elements present in the selected samples. The implications of the results on the material development of bamboo fiber-reinforced geopolymer mortar for construction are discussed

In-Plane Shear Behavior of Unreinforced Masonry Wall Strengthened with Bamboo Fiber Textile-Reinforced Geopolymer Mortar

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

Geopolymers as sustainable material for strengthening and restoring unreinforced masonry structures:A review

Unreinforced masonry (URM) structures are vulnerable to earthquakes; thus, materials and techniques for their strengthening and restoration should be developed. However, the materials used in some of the existing retrofitting technologies for URM and the waste produced at its end-of-life are unsustainable. The production of ordinary Portland cement (OPC) worldwide has enormously contributed to the global carbon footprint, resulting in persistent environmental problems. Replacing OPC with geopolymers, which are more sustainable and environmentally friendly, presents a potential solution to these problems. Geopolymers can replace the OPC component in engineering cementitious composites (ECC), recommended to strengthen and restore URM structures. In the present paper, the state-of-the-art knowledge development on applying geopolymers in URM structures is discussed. The discussion is focused on geopolymers and their components, material characterization, geopolymers as a strengthening and restoration material, and fiber-reinforced geopolymers and their application to URM structures. Based on this review, it was found that the mechanical properties of geopolymers are on par with that of OPC; however, there are few studies on the mentioned applications of geopolymers. The characterization of geopolymers’ mechanical and physical properties as a restoration material for URM structures is still limited. Therefore, other properties such as chemical interaction with the substrate, workability, thixotropic behavior, and aesthetic features of geopolymers need to be investigated for its wide application. The application method of geopolymer-based ECC as a strengthening material for a URM structure is by grouting injection. It is also worth recommending that other application techniques such as deep repointing, jacketing, and cement-plastering be explored