The resistance to chloride penetration of cement-based material with different curing regimes was investigated by solution titration,XRD,LF-NMR and rapid chloride migration test.The results show that the curing regime...The resistance to chloride penetration of cement-based material with different curing regimes was investigated by solution titration,XRD,LF-NMR and rapid chloride migration test.The results show that the curing regime has influences on the types and structure of the hydration products,which in turn affects their ability to bind chloride ions.The binding capacity of cementitious materials to chloride ions,porosity and chloride ion migration coefficient increased with the increase of water-cement ratio,while steam curing increased the porosity and chloride ion migration coefficient at the same time as it increased the chloride ion binding capacity of the materials.At lower water-cement ratios,the effect of steam curing on the resistance of cementitious materials to chloride ingress is negligible.展开更多
The effects of steam curing on mechanical properties,drying shrinkage,cracking sensitivity,anti-permeability,and carbonation resistance of C50 shield segment concrete were investigated,which were compared with the sta...The effects of steam curing on mechanical properties,drying shrinkage,cracking sensitivity,anti-permeability,and carbonation resistance of C50 shield segment concrete were investigated,which were compared with the standard curing conditions. The results indicated that steam curing could increase early strength of concrete and reduce its drying shrinkage. However,steam curing reduced later strength of concrete,increased its crack sensitivity and deteriorated its anti-permeability and carbonation resistance. Moreover,the incorporation of fly ash could improve the durability of steam-cured concrete.展开更多
The present study focuses on the improvement of pozzolanic reaction of fly ash particles with the cement hydration products.Low and high volume fly ash concrete mixtures were studied systematically with the addition o...The present study focuses on the improvement of pozzolanic reaction of fly ash particles with the cement hydration products.Low and high volume fly ash concrete mixtures were studied systematically with the addition of accelerating admixtures and accelerated curing of the concrete specimens in a steam chamber for 18 h at 75℃.Also,the reinforcing effects of glued steel fibers addition on the compressive and flexural performance of fly ash concrete were investigated.The test results indicated that the addition of accelerator improved the rate of hardening and the inclusion of steel fibers provided higher flexural performance.Also,it can be noted that the high volume fly ash(50%)addition in concrete showed a reduction in strength;however,the addition of accelerator has compensated the deceleration in strength gain.The proper selection of concrete ingredients,addition of accelerator and initial steam curing for 18 h showed better improvement on the engineering properties in fly ash concrete.A maximum increase(41.7%)in compressive strength of fly ash concrete around 52.90 MPa was noticed for 25%fly ash substitution and 1.5%steel fibers addition.Dynamic elastic modulus was also calculated in loaded concrete specimen using ultrasonic pulse velocity test and showed a good agreement with the experimental value.展开更多
基金Funded by the National Natural Science Foundation of China (Nos. 51972249, 52172026, 51772226)。
文摘The resistance to chloride penetration of cement-based material with different curing regimes was investigated by solution titration,XRD,LF-NMR and rapid chloride migration test.The results show that the curing regime has influences on the types and structure of the hydration products,which in turn affects their ability to bind chloride ions.The binding capacity of cementitious materials to chloride ions,porosity and chloride ion migration coefficient increased with the increase of water-cement ratio,while steam curing increased the porosity and chloride ion migration coefficient at the same time as it increased the chloride ion binding capacity of the materials.At lower water-cement ratios,the effect of steam curing on the resistance of cementitious materials to chloride ingress is negligible.
文摘The effects of steam curing on mechanical properties,drying shrinkage,cracking sensitivity,anti-permeability,and carbonation resistance of C50 shield segment concrete were investigated,which were compared with the standard curing conditions. The results indicated that steam curing could increase early strength of concrete and reduce its drying shrinkage. However,steam curing reduced later strength of concrete,increased its crack sensitivity and deteriorated its anti-permeability and carbonation resistance. Moreover,the incorporation of fly ash could improve the durability of steam-cured concrete.
文摘The present study focuses on the improvement of pozzolanic reaction of fly ash particles with the cement hydration products.Low and high volume fly ash concrete mixtures were studied systematically with the addition of accelerating admixtures and accelerated curing of the concrete specimens in a steam chamber for 18 h at 75℃.Also,the reinforcing effects of glued steel fibers addition on the compressive and flexural performance of fly ash concrete were investigated.The test results indicated that the addition of accelerator improved the rate of hardening and the inclusion of steel fibers provided higher flexural performance.Also,it can be noted that the high volume fly ash(50%)addition in concrete showed a reduction in strength;however,the addition of accelerator has compensated the deceleration in strength gain.The proper selection of concrete ingredients,addition of accelerator and initial steam curing for 18 h showed better improvement on the engineering properties in fly ash concrete.A maximum increase(41.7%)in compressive strength of fly ash concrete around 52.90 MPa was noticed for 25%fly ash substitution and 1.5%steel fibers addition.Dynamic elastic modulus was also calculated in loaded concrete specimen using ultrasonic pulse velocity test and showed a good agreement with the experimental value.
