Study On Durability Of Glass Fiber-Fly Ash Lightweight Concrete Materials

As a new building material,lightweight concrete is widely used in various construction engineering fields due to its excellent physical and mechanical properties.Durability is an important indicator of the service life of a building structure and an important factor in evaluating whether building materials meet the needs of use.In addition to the external load,the lightweight concrete is also affected by various physical and chemical factors in the natural environment.Under the coupling of various factors for a long time,it will cause structural damage or even damage due to poor durability..In this paper,cement-based foam lightweight concrete is used as the base material,and admixtures such as fly ash and glass fiber are selected to replace part of the cement,and the durability problems that may occur in the use stage of the material are tested by means of laboratory tests.The performance evaluation and prediction were improved on the basis of the conventional durability test,and the impermeability test,the dry shrinkage characteristic test and the freeze-thaw cycle test of the lightweight concrete material were carried out.The durability of lightweight concrete materials with different density grades,different fly ash and glass fiber consumption can be studied.The main research contents are as follows:(1)Through the experimental study on the impermeability of lightweight concrete materials,it is found that the penetration time of lightweight concrete increases with the increase of material density,and with the increase of water-cement ratio,it tends to increase first and then decrease.Fly ash has a significant effect on improving the internal structure of lightweight concrete and improving the impermeability of lightweight concrete materials under high wet density.The addition of glass fibers also contributes to the improvement of the impermeability of lightweight concrete materials at high wet densities.(2)Through the experimental study on the shrinkage characteristics of lightweight concrete materials,it is found that with the increase of age,the shrinkage of lightweight concrete increases,and the early stage is higher,and the later stage tends to be stable.With the increase of density,the dry shrinkage value of lightweight concrete is gradually reduced,and the addition of glass fiber can effectively suppress the shrinkage characteristics of the composite material,and there is an optimum dosage.Fly ash can effectively improve the shrinkage performance of lightweight concrete within a certain range of dosage,but excessively high dosage of fly ash will lead to excessive retardation of lightweight concrete,reducing the stability of the slurry and thus not conducive to mitigating materials.Dry shrinkage characteristics.(3)Through the experimental study on the frost resistance of lightweight concrete materials,it is found that with the increase of the density of lightweight concrete,its freeze-thaw resistance is improved.The compressive strength of lightweight concrete decreases with the increase of the number of freeze-thaw cycles.The smaller the density,the more the mass increases in the early stage of freeze-thaw,and the faster the quality loss in the later stage.The addition of fly ash and glass fiber can effectively improve the freeze-thaw resistance of lightweight concrete,and glass fiber can improve the anti-flaking performance of lightweight concrete.