Mechanical Performance Of Reinforced Concrete Slabs Strengthened With Textile Reinforced Geopolymer Mortar At Ambient And High Temperatures

Textile reinforced mortar(TRM)is a new type of structural strengthening material.Compared with the conventional strengthening material,fiber reinforced polymer(FRP),TRM exhibits better fire resistance.Polymer cement mortar is commonly used in TRM as the binder material,but the production of the cement in the polymer cement mortar consumes a lot of energy and emits large amounts of carbon dioxide,and thus the cement is considered to be one of the main causes of global warming.Geopolymer is a new type of green inorganic cementitious material with good mechanical properties and excellent high temperature resistance.It can be used as the binder matrix in mortar for structural strengthening.In this study,textile reinforced geopolymer mortar(TRGM),in which geopolymer mortar replaces polymer cement mortar as the binder for textile,is used to strengthen reinforced concrete slab,and the strengthening effect and fire resistance of the strengthened slabs are investigated.To this end,the following work has been carried out and some important conclusions have been drawn:1?Five RC one-way slabs strengthened with TRGM were tested under static load,and the influence of the number of textile layers,the spacing of weft fiber bundles and the anchoring measures on the mechanical properties of strengthened slabs were investigated.One unstrengthened slab and two slabs strengthened with textile reinforced polymer mortar(TRPM)were also tested for comparison.The test results show that:(1)TRGM can significantly improve the flexural capacity and post cracking stiffness of RC slabs,and delay the development of cracks.The flexural capacity of TRGM strengthened slabs with one,two and three layers of textile is 26%,53% and 92% higher than that of unstrengthened slabs respectively;(2)the spacing of the weft fiber bundles has a significant effect on the tensile strength of the warp fiber bundles,and the increament of the bearing capacity of the strengthened slabs increases with the decrease of the spacing of the weft fiber bundles;(3)the flexural capacity of slab strengthened with TRGM is slightly higher than that of slab strengthened with TRPM under the same condition.2?The finite element software is used to simulate the static load test process of TRGM strengthened RC slab,and the influence of reinforcement ratio,thickness of the slab and the number of textile layer on the bearing capacity of TRGM strengthened RC slab were investigated.Finally,a calculation formula of bearing capacity of TRGM strengthened RC oneway slab was proposed based on the test results and the finite element analysis results.The test results show that:(1)the bending behavior of TRGM strengthened slabs under static load can be well simulated by setting the cohesion element in the finite element model to consider the bond-slip relationship between textile and mortar;(2)the formula proposed in this paper can accurately predict the flexural capacity of TRGM strengthened slab.3?Fire tests were carried out on five TRGM strengthened RC one-way slabs,and the influence of the number of textile layers,load ratio and thickness of the surface coating of the strengthening layer were investigated.One unstrengthened slab and two TRPM strengthened slabs were also tested for comparison.The results show that:(1)under the same load ratio,the fire resistance of the strengthened slab is higher than that of the unstrengthened slab.The TRGM strengthened slab using 3 mm thick geopolymer mortar as the surface coating,but without any special fire protection measures,can meet the first-class fire resistance requirements on slabs;(2)the fire resistance of TRGM strengthened slab decreases with an increase in the load ratio,but when the load ratio is relatively small,the effect of slightly increasing in the load ratio on fire resistance is not significant;(3)under the same load ratio,increasing the number of textile layer or the thickness of the surface coating of the strengthening layer can improve the fireproof effect,and thus improving the fire resistance of the strengthened slab;(4)the high-temperature bonding performance of geopolymer mortar is better than that of polymer cement mortar,so when exposed to fire for a long time(such as > 90 min),TRGM can continue to play a role,while TRPM may fall off.However,due to the addition of a certain amount of Dula fiber in TRPM,other mechanical properties of TRPM deteriorate slowly in a certain temperature range,so the fire resistance of TRGM strengthened slab is not better than that of TRPM strengthened slab under the same load ratio.