Effect Of Freeze-thaw Cycle On The Properties Of Geopolymer Cement Stabilized Macadam And Its Mechanism

Geopolymer is a new type of inorganic cementing material with hydrohard activity,which is produced by using silica-aluminum raw material under the action of alkali activator.It has shown superiority in many properties and has a broad application prospect.There are relatively few studies on the application of geopolymers in cement stabilized base aggregate,and systematic and scientific studies on the damage law and mechanism of geopolymer cementing material cement stabilized gravel under freeze-thaw conditions are lacking.Research on the freeze-thaw resistance of geopolymer cementing material cement stabilized gravel is carried out to explore its failure mechanism.It is of great significance to the durability of ground polymer cementified material cement stabilized gravel and its application in practical engineering.In this thesis,based on the basic performance test of mineral powder,fly ash,calcium carbide slag,aggregate and cement,the principle of alkali excitation was used to configure the geopomer cementitious material,and finally formed the optimal ratio of geopomer cementitious material.The determined geopolymer cementing material was used to replace part of the cement to design the mixture ratio of geopolymer cementing material cement stabilized gravel.The unconfined compressive strength,compressive rebound modulus,indirect tensile strength and flexural tensile strength tests were carried out on the geopolymer cementing material cement stabilized gravel to explore the change law of the freeze-thaw resistance of the mixture with the dosage of geopolymer.Fatigue data of different mixtures under different freeze-thaw cycles were obtained by fatigue experiments.Fatigue life of mixtures was evaluated by establishing fatigue equations.The freeze-thaw damage mechanism of cement stabilized crushed stone was analyzed by scanning electron microscope and mercury injection apparatus.The results show that with the increase of freeze-thaw cycles,the unconfined compressive strength,compressive rebound modulus,indirect tensile strength and flexural tensile strength of cement stabilized crushed stone with different polymer contents decrease with the increase of freeze-thaw cycles,and the attenuation reaches the maximum after 10freeze-thaw cycles.When the content of geopolymer is 20%,the mechanical properties and anti-freezing properties of the mixture are better under the action of freeze-thaw cycle.Under the same freezing-thawing cycles,the fatigue performance of the mixture containing 20%geopolymers is better.Under different freezing-thawing cycles,the fatigue performance of the cement stabilized gravel with geopolymers presents a decreasing trend.With the increase of freezing-thawing times,cracks on the surface of the mixture increased.After 10 freezingthawing times,the growth rate of multi-damage pores of the mixture was the largest,but the addition of 20% geo polymers could effectively reduce the growth of harmful pores and improve the anti-freezing property of the mixture.