Study On Carbonization Properties Of Steel-PVA High Toughness Cementitious Composites

Concrete structure is generally exposed to the natural environment,will continue to be carbonized by the carbon dioxide from the atmosphere,long-term sustained carbonization will make concrete structure material neutral,lead to steel corrosion,concrete cracking,thereby making structural strength,service life threat.For a long time the structure of the service request（such as the low and medium radioactive nuclear waste processing unit,the general isolation service life of at least 300）with the outside world,considering the structure itself needed requirements such as strength,impermeability and energy absorption ability,and the natural environment for a long time for its durability,the influence of traditional concrete can meet the requirements,should be considered a new type of cement base material,the durability of the structure,increase its service life.Therefore,a kind of Steel-PVA High Toughness Cementitious Composites（SPHTCC）was proposed to study the mechanical properties and durability of the carbonized steel-PVA High Toughness Cementitious Composites.By testing the compressive strength,splitting tensile strength,bending toughness and carbonization depth of SPHTCC specimens before and after carbonization,and analyzing the test data,the essential effects of carbonization and fibrous materials on the mechanical properties and durability of SPHTCC were expounded.Based on the carbonation test data,the rapid carbonation depth prediction model of SPHTCC was built,and the carbonation depth prediction model of SPHTCC in general atmospheric environment was derived.The carbonation depth of the actual project（the disposal unit of Beilong Nuclear Waste Permanent Storage）was predicted with the environment as an example.The carbonization life was predicted by using rust swelling and cracking life criterion.The main test results show that:（1）Compared with PC（control group,matrix material without fiber incorporation）,SPHTCC has better carbonation resistance,and the carbonation depth of SPHTCC is the least at the same carbonation age.Fiber incorporation improves the carbonation resistance of cement-based materials,and the carbonation resistance of hybrid fiber is better than that of single fiber incorporation,showing a good positive hybridisation effect.（2）The strength and bending toughness of SPHTCC after carbonization are affected by both the fiber volume fraction and the carbonization age.For the post-carbonization compressive strength and splitting tensile strength,the increase of fiber volume fraction and carbonization have a positive effect on the whole,but the strength improvement range is limited by the steel fiber volume fraction.（3）The increase of fiber volume fraction has a positive effect on the bending toughness of SPHTCC,especially the increase of residual toughness,and the steel fiber plays a major role in the improvement of the toughness.Carbonation has a negative effect on bending toughness and the toughness decreases with the increase of carbonization age.（4）The carbonation depth prediction and carbonation life prediction of SPHTCC have a certain degree of accuracy.Compared with ordinary concrete,SPHTCC has a longer carbonation durability life.