Study On The Mechanical Properties And Durability Of Basalt Textile Reinforced Alkali-activated Slag-fly Ash Mortar

Alkali-activated material,as a novel type of green building structural materials,with excellent mechanical properties,low energy consumption,corrosion resistance,environment-friendly,good thermal stability and other performance advantages,become one of the central issues in materials engineering currently.However,the alkali-activated material also has the disadvantages of high brittleness,poor toughness and easy cracking.Reinforcement with the basalt textile can improve both the mechanical performance and volume stability of the alkali-activated cementitious materials.Compared with the randomly distributed short fibers,the warp or weft fiber bundles of the textile can be arranged in the main direction of the tensile stress,which significantly improves effectiveness of reinforcement.Alkali-activated slag fly ash mortar and basalt textile combined with each other in this paper,to obtain the building products with light weight,high strength,good reinforcement and crack control performance and meet the demand of the sustainable development strategy of modern society.A series of tests and analytical work about the bonding properties,bending properties at room temperature and at high temperature,and durability performance of basalt textile reinforced alkali-activated slag fly ash mortar have been completed and some conclusions have been obtained.According to pullout testing result,for the coated fabric the filaments within the bundle are glued together;when loaded during pullout test the stresses are efficiently transferred to all reinforcing filaments within the fabric,exhibiti ng high pull out resistance and good bonding.After epoxy impregnation treatment,the weft fiber and strip width can improve the interfacial bonding performance of basalt textile reinforced alkali-activated slag fly ash mortar,and the strip width has a gr eater impact.According to three-point bending testing result,the number of textile layers is a decisive factor on the flexural properties of basalt textile reinforced alkali-activated slag fly ash mortar.With the increasing numeber of textile layers,specimen exhibits better flexural bearing capacity and toughness.The epoxy coating can improve the flexural strength,but lead to a steep drop in the stress-strain curve and reduce the toughness of the specimen.Through the research about flexural behavior of basalt textile reinforced alkali-activated slag-fly ash composite after exposure to elevated temperatures,we find that the flexural strength of basalt textile reinforced alkali-activated slag-fly ash mortar specimens decreased almost linearly with the increase of temperature due to the deterioration of the matrix and basalt textile.And the failure morphology was also transformed from multiple-cracking mode to single-cracking mode.After heat exposure at 800℃ for 1h,the remained flexural strength of the specimens was only 1.67 MPa.Surface coating with epoxy resin enhanced the flexural strength under the exposure temperature below 600℃.Due to the decomposition of epoxy resin and the deterioration of the bond between fiber and matrix,significa nt strength loss can be observed when the exposure temperature was higher than 600℃.Increase the number of textile layers can enhance the mechanical properties of specimens after exposure to elevated temperatures to a certain extent,but the enhancement g radually weakens with the increase of temperature.And the improvement to the flexural bearing capacity became insignificant for the epoxy coated specimen after the exposure temperature reached 600℃.The accelerated aging experimental results indicate that compared with that of Portland cement mortar specimens,the flexural strength of the textile reinforced alkali-activated cement mortar specimens decreased more obviously with accelerated aging.After exposure for 24 days,the strength retention rate of al kali-activated cement mortar specimens and Portland cement mortar specimens are 68.9% and 81.7% respectively.The epoxy coating can improve the flexural strength and mitigate the alkaline deterioration on the flexural strength within the first 6 days.But the effect of the epoxy coating gradually weakens with the increase of the age,and roughly fails at 18 d.Specifically,the reduction degree on the ultimate flexural strain is more obvious compared to that of the flexural strength.The basalt fibers embedd ed in the Portland cement mortars present local pit corrosion,while the wholescale pit corrosion can be found on the surface of those embedded in the alkali-activated cement mortars.These results support that the epoxy coating can effectively protect tex tiles from the alkali solution in matrix,but it degrades gradually during the accelerated aging process.Hence,the development of new surface treatment methods is needed to achieve more durable and effective surface protection for the basalt fiber in alk aline solution.