Papers by Keyword: Freeze-Thaw Cycles

Abstract: Magnesium phosphate cement concrete (MPCC) has high early strength, which is conducive to achieving rapid repair of winter concrete pavements under no-maintenance conditions. In this paper, we investigated the influence mechanism of four cement antifreeze components on the mechanical and durability properties of MPCC under the severe cold environment, focusing on the development law of the performance of MPCC as a rapid repair material for pavements. The results show that the antifreeze effect of MPCC antifreeze components under severe cold environments is contrasted as MgCl₂ > Mg (NO₃)₂ > Ethylene glycol > Mg (NO₂) ₂. However, the addition of antifreeze components, especially inorganic salt antifreeze components, will also have an adverse effect on the antifreeze resistance of concrete during the service period.

Abstract: Servicing in the natural environment, asphalt pavement is often exposed to the various aqueous solution, however, the effect of different media aqueous solution on road performance of asphalt mixtures remains ambiguous. In this study, the influences of water, acid, alkali and salt solution on volume of air voids (VV), tensile strength rate (TSR), low temperature performance of 70^# asphalt mixtures and SBS modified asphalt mixtures were investigated through freeze-thaw cycles test, void ratio test, Lottman test and Three-point Bending Fracture (TBF) test. The results indicated that freeze–thaw cycles influenced the road performance of asphalt mixtures significantly, increased the air void of asphalt mixtures, and reduced tensile strength ratio and failure strain of asphalt mixtures. Compared with the distilled water, the damage of acid, alkali and salt solution on the road performances of asphalt mixtures were more serious, especially alkali solution to tensile strength rate and failure strains in low temperature, and salt solution to VV. The moisture corrosion resistance of SBS modified asphalt mixtures is better than that of 70^# asphalt mixtures.

Abstract: Geopolymer have gradually become an alternative materials for hazardous and radioactive waste immobilization. However, the compatibility between radioactive waste and geopolymer in various extreme conditions are still not clear. In this study, the thermal stability of geopolymer solidified product of Sr contaminated zeolite A was investigated. For this purpose, the specimens after standard curing were subjected to temperatures of 600, 700 and 800 degrees C for 2h. Freeze-thaw cycles were also employed to test the thermal stability of geopolymer matrices. Meanwhile, changes in the leaching characteristics and physical properties were analyzed. Analysis showed that geopolymer - Sr contaminated zeolite A blends exhibited excellent thermal stability. Although elevated temperature and freeze-thaw cycles led to the deterioration of geopolymer matrices, the leaching rate and mechanical properties of solidified product were still acceptable. The resluts obtained indicated that geopolymer appeared to be very suitable for radioactive waste immobilization.

Abstract: This paper studies on the frost resistance of high-content fly ash concrete which content 52 fly ash in seawater. The uniaxial compressive property test was carried out after the fast freeze-thaw test with 0, 100, 200, 300 and 400 cycles. The research analyzed the influence of the uniaxial strength of the concrete mixed with high-content fly ash after freeze-thaw cycles in seawater. Then established a mathematical expression in a simple way. In the real project, the concrete mixed with fly ash can improve the frost resistance. The dosage of fly ash will directly influence the frost resistance and mechanical property. However, there is less study on frost resistance of concrete mixed with fly ash, especially the test under the seawater environment.

Abstract: Bases on the project of typical natural coarse saline soil area ,Startis from the saline soil salt expansion characteristics of seven cycles of freeze-thaw cycling test and saline soil subgrade model test ,concluses not only the oil can make roadbed fillers for highway and first-class highway directily , but provides experiences for saline land area of natural coarse particles of high highway designs and construction engineering. Meanwhile, this paper also provides reference experiences for the design and construction of high level road engineering at natural coarse saline soil regions.

Abstract: This paper studies the influence on compressive strength, freezing resistance and microstructure of cement mortar with different content of mica in stone powder, in the tests, manufactured sand with high content of mica and natural river sand were mixed with different proportion, and the content of stone powder was the same in mixed sand. Experiment results indicate that, with the increasing of mica content in stone powder, 28d and 60d compressive strength of cement mortar decreases obvious, mass loss rate and strength loss rate with 50 freeze-thaw cycles increase a little. Microstructure of cement mortar with higher content of mica is not compactly by SEM, the internal defects of cement hardened pastes could be increased because of the flake mica which surface is smooth, and it will cause the spread of micro crack.

Abstract: The bonded joints between carbon fiber reinforced polymer (CFRP) and high strength concrete subjected to different freeze-thaw cycles were studied and the results were analyzed. The test results indicate that with the increase of freeze-thaw cycles, effective bond length, ultimate bond load and ultimate global slip response will decrease. But it has little effects on initial stripping load. The failure modes change from adhesive debonding to shear failure of concrete.

Abstract: The aim of this paper is to evaluate the possibility of using the Impact-echo method for assessment of extremely long period of frost resistance of ceramic tiles. Sets of ceramic tiles of the Ia class to EN 14 411 B standard made by manufacture RACOs have been analyzed. The ceramic tiles under investigation have been subjected to 500 freeze-thaw-cycle based degradation in compliance with the relevant EN ISO 10545-12 standard. To verify the correctness of the Impact-echo method results, additional physical properties of the ceramic tiles under test have been measured. To analyze the specimen surface condition, we also used Olympus LEXT 3100 confocal scanning microscope. It has been proved that the acoustic method Impact-echo is a sensitive indicator of the structure condition and can be applied to the ceramic cladding element frost resistance and service life prediction assessment.

Abstract: Statistical methods was combined with micromechanics. Based on the parallel bar system, the damage law of the concrete materials subjected to uniaxial compressive stress was simulated. Furthermore, the meso-statistical damage constitutive of concrete materials was studied base on the Weibull’s statistical theory of the strength of materials. While according to constitutive uniaxial compression test of concrete material after freezing and thawing, the parameters m and ε₀ of the model were fitted. Then the freeze-thaw damage constitutive equation of concrete was proposed base on meso-statistical damage mechanics. Finally, the experimental results was compared with theoretical models, and the rationality of the theoretical model was verified.