Study On Alkali Resistance Of Basalt Fiber And Long-term Mechanical Properties Of Its Reinforced Cement-based Composite

In recent years,with the improvement of basalt fiber manufacturing technology,the combination of basalt fiber and cement-based materials has achieved good strengthening effect.At present,the alkali resistance of basalt fiber is controversial.When it is used as reinforcement material in cement-based composite,it will face the problem of being in cement-based alkali environment for a long time.If it does not have good alkali resistance,it will be corroded,which will reduce the tensile capacity of fiber,thus reducing the strengthening effect on cement-based composite and the service life of composite.Therefore,on the basis of understanding the tensile properties of basalt fiber,it is very important to study the alkali resistance of basalt fiber and its long-term strengthening effect on cement-based composite.Based on this,the main contents of this paper are as follows:(1)Fiber static tensile test: The static tensile tests of basalt fiber(BF)with different stress directions and forms were carried out,and compared with alkali-resistant glass fiber(AR-glass)and medium alkali glass fiber(C-glass).The results show that under tensile load,the surface setting glue of fiber sample is cracked first,then the internal fiber filaments are broken,the fiber sample is broken at the intersection of warp and weft;the load-displacement curve of the BF bundle in the weft direction is in the form of "single triangle",while the warp is in the form of "double triangle";the breaking strength of the fiber bundle and the fiber strip is not a simple superposition relationship;the tensile strength of fiber bundle is: weft BF > warp BF > C-glass > AR-glass.(2)Study on the alkali resistance of fiber: The BF bundle and precursors were soaked in ordinary portland cement(OPC)filtrate,high belite sulphoaluminate cement(HB-CSA)filtrate and sulphoaluminate cement(CSA)filtrate.Tensile test was carried out on the soaked BF bundle,and compared with AR-glass and C-glass fiber bundle.The BF precursors were analyzed by SEM.The results show that the alkali resistance of BF bundle is better than C-glass fiber bundle,and is equivalent to AR-glass fiber bundle;the higher the p H value of filtrate,the more serious the fiber bundle tensile strength loss;when the BF precursor was soaked by OPC filtrate,its surface appears "spot" corrosion damage,while the precursor was soaked by the other two kinds of cement filtrate,there is no obvious damage on the fiber surface.(3)Long-term mechanical properties and mechanism of BF textile reinforced cement-based composite: The aging treatment and bending test under different ages were carried out for BF textile reinforced cement-based composite with various cementitious materials,such as OPC,HB-CSA and CSA,and compared with AR-glass fiber textile reinforced cement-based composite and C-glass fiber textile reinforced cement-based composite.The mechanical properties of composite board under different aging time were compared,the mechanism was analyzed by microscopic test.The results show that after long-term aging,the strengthening effect of BF textile and AR-glass fiber textile on composite board is equivalent;using HB-CSA or CSA as cementitious material can significantly improve the long-term mechanical properties of BF textile reinforced cement-based composite;during the whole aging period,CH is not found in hydration products of HB-CSA and CSA,therefore,the corrode of HB-CSA and CSA on the fiber is weakened,which makes the composite board with HB-CSA or CSA as cementitious materials have better long-term mechanical properties than with OPC as cementitious materials.The composite with HB-CSA or CSA as cementitious materials can be recommended as engineering materials.