Chemical admixtures are of paramount importance to the performance of modern cement based composites. In this paper, we performed a series of tests to investigate the effects of chemical admixtures on the cement aspha...Chemical admixtures are of paramount importance to the performance of modern cement based composites. In this paper, we performed a series of tests to investigate the effects of chemical admixtures on the cement asphalt mortar(CA mortar), i e, compressive strength, frost resistance, permeability, fatigue resistance, pore structure and microstructure. In particular, two types of chemical admixtures were tested, i e, defoamer(tributyl phosphate(TBP)) and polycarboxylate superplasticizer(PS). The results indicate that the addition of TBP and PS eliminates big bubbles and promotes small non-connected pores forming in matrix. Besides, an optimum dosage of TBP and PS may be determined with respect to the frost resistance, permeability and fatigue resistance of CA mortar. Further elaborative discussions are presented as well as experimental evidences from mercury intrusion porosimetry, scanning electron microscopy and energy dispersive spectroscopy.展开更多
The epoxy resin polymer cement mortars with excellent performances were made up through modifying ordinary Portland cement with emulsified epoxy and micro fine slag.The microstructure of the epoxy resin polymer cemen...The epoxy resin polymer cement mortars with excellent performances were made up through modifying ordinary Portland cement with emulsified epoxy and micro fine slag.The microstructure of the epoxy resin polymer cement materials was studied and their hydration and hardening characteristics were discussed by means of modern analysis measures such as SEM,XRD and Hg intrusion micromeritics.The experimental results indicate that the series effects of water reducing,density,pozzolanicity,filling and solidification crosslinking through the action together with epoxy organism and micro fine slag endowed cement based materials with perfect performances.The main hydration products in the system are C S H gel and hydrated calcium aluminate.At later age,AFt can be in existence,and no Ca(OH) 2 is found.When epoxy resin is solidified,the organism is in a network structure.In the micro pore structure of hydrated cement with modified epoxy and fine slag,big harmful pores were fewer,more harmless abundant micro pores were and the possible pore radius was smaller than that of ordinary Portland cement.展开更多
The compressive strength developing process and the microstructure of cement-asphalt mortar （CA mortar） were investigated.The fluidity of CA mortar has a great influence on its strength.The optimum value of spread d...The compressive strength developing process and the microstructure of cement-asphalt mortar （CA mortar） were investigated.The fluidity of CA mortar has a great influence on its strength.The optimum value of spread diameter of slump flow test is in the range of 300 to 400 mm.The compressive strength of CA mortar keeps a relatively high growth rate in 56 days and grows slowly afterwards.The residual water of hydration in CA mortar freezes under minus environmental temperature which can lead to a significant reduction of the strength of CA mortar.Increasing A/C retards asphalt emulsion splitting and thus prolongs the setting process of CA mortar.The hydration products of cement form the major structural framework of hardened CA mortar and asphalt is a weak phase in the framework but improves the viscoelastic behavior of CA mortar.Therefore,asphalt emulsion should be used as much as possible on the condition that essential performance criterions of CA mortar are satisfied.展开更多
Under repeated train-induced loads, cement and emulsified asphalt mortar(CA mortar) as a viscoelastic material has a time-dependent deformation, part of which is irreversible. This could lead to debonding between the ...Under repeated train-induced loads, cement and emulsified asphalt mortar(CA mortar) as a viscoelastic material has a time-dependent deformation, part of which is irreversible. This could lead to debonding between the mortar layer and the track slab. Based on the theory of viscoelasticity and the analytical method of the time hardening law(THL), the viscoelastic deformation behavior of CA mortar was studied. Using ABAQUS, we established a solid model of China railway track system(CRTS) Ⅰ prefabricated slab track, with CA mortar at different initial Young’s moduli under cyclic loading corresponding to the influence of actual train loads. The results reveal that the fitted parameters of the THL for CA mortar are suitable for describing its viscoelastic deformation. As the initial Young’s modulus increases, the strain difference before and after cyclic loading gradually decreases, and the displacement difference increases from 0.2 mm to 0.6 mm. The deformation mainly occurs at the end of a mortar layer with longitudinal distribution of about 2.5 times the fasteners’ spacing. It follows that the viscoelastic performance of CA mortar is one of the most important reasons that cause debonding underneath the track slab. Therefore, we suggest that the adverse effects of viscoelastic behavior of CA mortar should be considered when researching such deformation and damage.展开更多
基金Funded by the National Natural Science Foundation of China(Nos.U1134206,51178230)the Technological Development Projects of China Railway Engineering Corporation(No.Z2013-038-3)
文摘Chemical admixtures are of paramount importance to the performance of modern cement based composites. In this paper, we performed a series of tests to investigate the effects of chemical admixtures on the cement asphalt mortar(CA mortar), i e, compressive strength, frost resistance, permeability, fatigue resistance, pore structure and microstructure. In particular, two types of chemical admixtures were tested, i e, defoamer(tributyl phosphate(TBP)) and polycarboxylate superplasticizer(PS). The results indicate that the addition of TBP and PS eliminates big bubbles and promotes small non-connected pores forming in matrix. Besides, an optimum dosage of TBP and PS may be determined with respect to the frost resistance, permeability and fatigue resistance of CA mortar. Further elaborative discussions are presented as well as experimental evidences from mercury intrusion porosimetry, scanning electron microscopy and energy dispersive spectroscopy.
文摘The epoxy resin polymer cement mortars with excellent performances were made up through modifying ordinary Portland cement with emulsified epoxy and micro fine slag.The microstructure of the epoxy resin polymer cement materials was studied and their hydration and hardening characteristics were discussed by means of modern analysis measures such as SEM,XRD and Hg intrusion micromeritics.The experimental results indicate that the series effects of water reducing,density,pozzolanicity,filling and solidification crosslinking through the action together with epoxy organism and micro fine slag endowed cement based materials with perfect performances.The main hydration products in the system are C S H gel and hydrated calcium aluminate.At later age,AFt can be in existence,and no Ca(OH) 2 is found.When epoxy resin is solidified,the organism is in a network structure.In the micro pore structure of hydrated cement with modified epoxy and fine slag,big harmful pores were fewer,more harmless abundant micro pores were and the possible pore radius was smaller than that of ordinary Portland cement.
基金Funded by National Natural Science Foundation of China (No.50802050)the Key Research and Development Program of Chinese Ministry of Railway (No.2008G031-18-6)
文摘The compressive strength developing process and the microstructure of cement-asphalt mortar （CA mortar） were investigated.The fluidity of CA mortar has a great influence on its strength.The optimum value of spread diameter of slump flow test is in the range of 300 to 400 mm.The compressive strength of CA mortar keeps a relatively high growth rate in 56 days and grows slowly afterwards.The residual water of hydration in CA mortar freezes under minus environmental temperature which can lead to a significant reduction of the strength of CA mortar.Increasing A/C retards asphalt emulsion splitting and thus prolongs the setting process of CA mortar.The hydration products of cement form the major structural framework of hardened CA mortar and asphalt is a weak phase in the framework but improves the viscoelastic behavior of CA mortar.Therefore,asphalt emulsion should be used as much as possible on the condition that essential performance criterions of CA mortar are satisfied.
基金Project supported by the National Natural Science Foundation of China(No.51578472)。
文摘Under repeated train-induced loads, cement and emulsified asphalt mortar(CA mortar) as a viscoelastic material has a time-dependent deformation, part of which is irreversible. This could lead to debonding between the mortar layer and the track slab. Based on the theory of viscoelasticity and the analytical method of the time hardening law(THL), the viscoelastic deformation behavior of CA mortar was studied. Using ABAQUS, we established a solid model of China railway track system(CRTS) Ⅰ prefabricated slab track, with CA mortar at different initial Young’s moduli under cyclic loading corresponding to the influence of actual train loads. The results reveal that the fitted parameters of the THL for CA mortar are suitable for describing its viscoelastic deformation. As the initial Young’s modulus increases, the strain difference before and after cyclic loading gradually decreases, and the displacement difference increases from 0.2 mm to 0.6 mm. The deformation mainly occurs at the end of a mortar layer with longitudinal distribution of about 2.5 times the fasteners’ spacing. It follows that the viscoelastic performance of CA mortar is one of the most important reasons that cause debonding underneath the track slab. Therefore, we suggest that the adverse effects of viscoelastic behavior of CA mortar should be considered when researching such deformation and damage.
