Experimental Study On Mechanical Properties And Durability Of Lignin Fiber Composite Cement Soil

Cement soil is an environmentally friendly building material with a wide range of applications and economical rationality,which is widely used in infrastructure.With the improvement of national economic strength,the number of infrastructure constructions has gradually increased,the requirements for the mechanical properties and durability of cement and soil have gradually expanded,and the degree of environmental impact has gradually deepened.In order to implement the green building action,this article applies industrial byproducts fly ash,lignin fiber,and metakaolin to cement soil.Study the mechanical properties and durability of lignin fiber composite cement soil formed by mixing lignin fiber,fly ash and metakaolin.(1)First,through a single factor test,study the strength characteristics of loose and granular lignin fiber cement soil,lignin fiber fly ash cement soil and metakaolin cement soil,choose the lignin fiber morphology and the best components Dosage.Synthesizing the test results:the optimal dosage of the components of the lignin fiber composite cement soil prepared in this paper is:cement 15%,loose lignin fiber 0.4%,fly ash 12%,and kaolin 4%.(2)Secondly,carry out unconfined compressive strength test and microstructure test such as FTIR,XRD and SEM on lignin fiber composite cement soil.The macro-mechanical performance test shows that with the extension of curing age,the strength difference between lignin fiber composite cement soil and ordinary cement soil becomes larger.The microstructure test shows that the admixture of the mixture exerts the micro-aggregate effect in the cement soil and forms a fiber network,which enhances the compactness and integrity of the cement soil structure.(3)The freeze-thaw cycle test was carried out on the lignin fiber composite cement soil again,the morphological changes and strength loss after the freeze-thaw cycle were analyzed,and the freeze-thaw resistance was evaluated.The test results show that with the increase of the number of freeze-thaw cycles,the strength loss of lignin fiber composite cement soil is small.When the freeze-thaw cycle is 16 times,some holes appear in the lignin fiber cement soil.There are obvious cracks,therefore,the lignin fiber cement soil has better freeze-thaw resistance.(4)Finally,an erosion test under the environment of sodium sulfate and sodium chloride was carried out on the lignin fiber composite cement soil to analyze the strength change and hydration degree of the cement soil after salt intrusion.The test results show that in the sodium sulfate environment,the compressive strength of lignin fiber composite cement soil increases first and then decreases with the increase of sodium sulfate concentration.The high concentration sodium sulfate environment has little effect on the degree of cement soil hydration.In the sodium chloride environment,the compressive strength of lignin fiber composite cement soil decreases with the increase of sodium chloride concentration,and the sodium chloride environment has little effect on the degree of cement soil hydration.