Experimental Study On Salt Corrosion Resistance Of Lightweight Cement Fly Ash Subgrade Filler

Highways in saline soil areas are prone to diseases such as longitudinal cracks,instability and uneven settlement.The saline soil area in Shanxi Province is widely distributed.At the same time,the utilization rate of solid waste materials in Shanxi Province is still low.The comprehensive utilization of solid waste resources is a major economic and technological policy and long-term strategic policy of Shanxi and even the whole country.Therefore,solid waste is applied to saline soil.There are important strategic and practical significance in the district highway.In this paper,solid waste fly ash,cement,air bubble group,early strength agent and water are used as the main raw materials.The lightweight cement fly ash roadbed material must not only meet the roadbed strength standards,but also use waste fly ash.Effectively use as much as possible as the starting point for research.Through laboratory tests,the strength and salt erosion resistance of lightweight cement and fly ash mixtures in roadbed applications are studied.The thermal conductivity and freeze-thaw resistance of lightweight roadbed materials are also studied.The analysis has revealed the influence of salt corrosion on the strength of lightweight cement fly ash roadbed.This article has achieved the following main results:（1）The density of the roadbed can be effectively reduced by increasing the formula ratio of fly ash in the roadbed material and increasing the amount of air bubbles.As the fly ash ratio becomes larger,the slurry and workability become better,and the interior of the light roadbed The better the state of the air bubble group,the lighter the lightness will be;in the process of air bubble filling cement fly ash mixture,with the increase of the amount of air bubbles,the subgrade water absorption rate will first decrease and then increase.（2）The unconfined compressive strength of lightweight subgrade materials increases with the number of days of maintenance.The unconfined compressive strength of lightweight subgrades decreases with the decrease of the mass ratio of cement to fly ash.When the mass ratio of cement to fly ash is greater than 1:3,it can meet the requirements of highway subgrade pavement construction specifications.Requirements.（3）Under the condition that other conditions remain unchanged,the unconfined compressive strength of lightweight roadbed materials is higher in hydroponic conditions than in standard culture conditions.In the case of the same salt solution corrosion,the unconfined compressive strength of the sample decreases with the increase of the salt solution concentration;in the case of the same salt solution corrosion,the unconfined compressive strength decreases with the The proportion of fly ash increases and decreases.Under the same conditions,the light roadbed is most severely corroded in the sodium sulfate solution,followed by the compound salt solution,and the least corroded in the sodium chloride salt solution.（4）In the freeze-thaw cycle test,although the strength of the light roadbed has decreased,it still meets the requirements of highway roadbed specifications.Therefore,light roadbeds can be used in saline soil areas with large temperature differences between day and night.As the bubble content increases,the thermal conductivity gradually decreases;when the bubble content is constant,the higher the temperature,the larger the thermal conductivity;under the same conditions as temperature,bubble content and other conditions,the thermal conductivity increases with pulverized coal The increase in the ash ratio first increased to reach the apex at 1:2,and then decreased as the ash ratio increased.The greater the compactness and strength,the greater the thermal conductivity of the lightweight subgrade sample.In low temperature environment,the thermal conductivity of the sample is greatly affected by the amount of air bubbles.At high temperature,the thermal conductivity of the sample is significantly affected by the compactness and strength of the sample.（5）When the mass ratio of cement to fly ash is 1:3 and it is cured in a 15%sodium sulfate solution for 28 days,its unconfined compressive strength still meets the requirements of<The Code for Construction of Highway Subgrades and Pavements>^[1],and Excellent water resistance,heat insulation and freeze-thaw resistance.Therefore,it is determined that the quality ratio of cement to fly ash is 1:3,and the ratio of the bubble content to 1200L/m3 is the best formula.