Study On Mechanical Properties And Hydration Mechanism Of Eggshell Powder-waste Glass Dust Modified Concrete

Nowadays,the green,carbon dioxide and sustainability have become the theme of development.In order to decrease the pressure of gradual depletion of resources and increase the secondary use of solid waste,this thesis adds waste glass（GP）and waste eggshell（ESP）to concrete as auxiliary cementing materials.Therefore,a new auxiliary cementitious material for application in concrete is established,which not only has good environmental benefits and considerable economic benefits but also can improve the performance of concrete.In addition,according to the principle of efficient use of cement,the composite cementitious material composition design for which improve the performance of hardened slurry as the goal,and ameliorating the mechanical properties of concrete as the guidance.And the basic mechanical properties and hydration properties of concrete with composite cementitious material as the core were studied experimentally.The main research contents and relevant conclusions are as follows.（1）The addition of ESP and GP to the concrete resulted in a significant increase in compressive strength.To some extent,the compressive strength was enhanced with the increase of ESP-GP content.Compared with ordinary concrete 28d compressive strength of78.8MPa,the compressive strength of E10G10（10%ESP content and 10%GP content）and E20G20（20%ESP content and 20%GP content）increased by 21.41%and 14.0%.The 28d compressive strength of ESP-GP concrete E30G30（30%ESP content and 30%GP content）with a large number of eggshell particles is 67.55MPa,which has reached the target design concrete compressive strength requirements.Among the 12 groups of concrete mix ratios,E10G10 is the best admixture,ESP dosage is 10%and GP content is 10%.（2）The hydration reaction of eggshell particle–waste glass powder–cement ternary cementitious system in concrete and the microstructure of hydration products at different stages were revealed.Eggshell particles（ESP）and waste glass particles（GP）have a hysteretic effect in the initial stage of hydration,which decreases the overall hydration reaction rate.In the hydration process of concrete,the activity of ESP is greater than that of GP.And the ESP and GP are mutually reinforcing.The hydration reaction of ESP-GP-cement composite cementitious material consumes Ca（OH）₂,which does not reduce the alkali content of the system at low dosage（<40%）,while high dosage will decrease the alkali content of the system.In the ternary cementing system of eggshell particles,waste glass powder and cement,the reaction degree of cement is the highest,the eggshell particles are the weaker,and the waste glass is the lowest.（3）Under high temperature and high humidity curing,eggshell particles and waste glass powder are more beneficial to stimulate the volcanic ash effect,increase the hydration reaction rate and improve the hydration activity.Compared with the compressive strength of ESP-GP concrete under standard curing conditions,the overall strength of ESP-GP concrete under high temperature and high humidity curing conditions is higher.In contrast to ordinary concrete,which achieves 90%of its 28d compressive strength at 3d,ESP-GP concrete achieves 70%.In the late curing period,the strength of ESP-GP concrete is higher than that of ordinary concrete.（4）Eggshell particles and waste glass powder added into concrete can decrease the porosity of concrete and optimize the pore structure of concrete.This will increase the number of harmless holes,so that more harmful holes into harmful and less harmful holes.There is a strong linear correlation between the chemical bound water and the concrete compressive strength.The content of the chemical bound water characterizes the enhancement degree of the chemical action on the concrete compressive strength during the hydration process.The composite cementitious system concrete with high dosage of 40%cement has reached the expected design strength,and the concrete with this dosage has good mechanical properties.