Study On Interfacial Enhancement Mechanism And Performance For Modified Rubber-Cement Stabilized Macadams

Rubber is an elastic polymer material.After it is added in the cement stabilized macadams,the stiffness of cement stabilized macadam is decreased.The difference of the stiffness in pavement layer is alleviated.And the cracking of the base is reduced.However,the hydrophilicity of rubber particles is very poor,which leads to the weak at the junction of rubber and cement.To improve the adhesion between rubber and cement mortar,four chemical treatment methods were used to treat the surface of rubber particles.They included oxidizing rubber with sodium hydroxide oxidation(NaOH),oxidizing rubber with sodium hydroxide oxidation and ammoniating rubber with urea(NaOH-Urea),silane coupling agent KH560 and sodium silicate(Na2SiO3)to form Si-O-Si spatial structure on the rubber surface.The rubber-cement interface performance is explored.The strength,rigidity,toughness and fatigue performance of rubber-cement stabilized macadams are analyzed.And its frost resistance and cracking resistance are carried out.The microscopic test results show that NaOH,NaOH-Urea and KH560 increase the hydrophilicity of rubber particles.KH560 and Na2SiO3 graft Si-O bonds and increase the possibility of the formation of Si-O-Si spatial reticulate structure on the rubber surface.But the Si-O feature peaks of Na2SiO3 modified rubber are not obvious.The mechanical property test results show that NaOH-Urea and KH560 can improve the 7d unconfined compressive strength and flexural tensile strength of rubber-cement stabilized macadams.Moreover,their 7d unconfined compressive strength is 1.45 times and 1.38 times that of unmodified rubber cement stabilized macadam,respectively.Their flexural tensile strength is 1.12 times and 1.02 times that of unmodified rubber cement stabilized macadam,respectively.The KH560 and NaOH-Urea can significantly improve the toughness and reduce the stiffness of rubber-cement stabilized macadams.The modification of NaOH and Na2SiO3 reduces the toughness of rubber-cement stabilized macadams.The stiffness of NaOH modified rubber-cement stabilized macadams increases,while the stiffness of Na2SiO3 modified rubber-cement stabilized macadams decreases slightly.The four chemical modification methods all improve the fatigue resistance of rubber-cement stabilized macadams.The crack resistance and frost resistance test results show that the frost resistance and temperature shrinkage performance of KH560 and NaOH-Urea modified rubber-cement stabilized macadams are enhanced,compared to unmodified rubber-cement stabilized macadams.While these performance of NaOH and Na2SiO3 modified rubber-cement stabilized macadams are poor.Rubber is added to cement stabilized macadam after chemical modification,which can improve the dry shrinkage performance of the materials.In conclusion,each performance index is given corresponding weight and score.Then they are carried out weighting summation.The overall performance of five rubber-cement stabilized macadams is evaluated through the total score.That is the comprehensive scoring method.The results show that the best chemical modifier for rubber-cement stabilized macadams is KH560.The overall performance is improved by 17.81%.The second is NaOH-Urea composite modification method.And the overall performance is improved by 13.54%.