In order to facilitate self-compacting concrete to be better used in tunnel linings that can resist fires,a SiO_(2) aerogel-cement mortar coating was prepared.Based on the HC curve,a self compacting concrete cube spec...In order to facilitate self-compacting concrete to be better used in tunnel linings that can resist fires,a SiO_(2) aerogel-cement mortar coating was prepared.Based on the HC curve,a self compacting concrete cube specimens coated and uncoated with SiO_(2) aerogel-cement mortar(SiO_(2)-ACM)were heated to simulate tunnel fire for 0.5,1,1.5,2,2.5,3 and 4 h,respectively.The residual compressive strength was tested after the specimens were cooled to room temperature by natural cooling and water cooling.The results show that,the damages of specimens become more serious as fire time goes on,but the residual strength of specimens coated with SiO_(2)-ACM is always higher than that of uncoated with SiO_(2)-ACM.In addition,the residual strength of specimens cooled by water cooling is lower than that of natural cooling.However,for the specimens coated with SiO_(2)-ACM,the adverse effects of water cooling are lessened.With the increase of fire time,the protective effect of SiO_(2)-ACM is still gradually improved.Finally,a formula was established to predict the residual 150 mm cube compressive strength of specimens protected by SiO_(2)-ACM after a simulated tunnel fire.展开更多
To further strengthen the protective effect of aerogel cement paste (ACP) coating on self-compacting concrete (SCC) in tunnel fire under the optimal mix proportion,the effect of curing temperature (from 5 to 80 ℃,bas...To further strengthen the protective effect of aerogel cement paste (ACP) coating on self-compacting concrete (SCC) in tunnel fire under the optimal mix proportion,the effect of curing temperature (from 5 to 80 ℃,based on site construction curing temperature and surrounding rock temperature) on fire insulation of ACP was investigated.The mechanical properties,thermal conductivity and porosity of ACP were tested.The microstructure of ACP was characterized by means of SEM,XRD and TG/DTG.The results reveal that 50 ℃ is the optimal curing temperature for ACP with good mechanical properties and fire insulation.Relatively high curing temperature can facilitate hydration and pozzolanic reactions,contributing to the generation of more stable substances (such as C-S-H gels,tobermorite and thenardite,etc).ACP under excessive low curing temperature brings inhomogeneous microstructure with coarse pores,leading to producing wider and longer microcracks when it is exposed to tunnel fire.The microcracks make the heat convection and thermal radiation more significant and thus accelerate the damage of ACP under fire.In case of the less than 7% difference of thermal conductivity,dense microstructure and stable substances are more conducive to strengthening fire insulation of ACP.In practical engineering applications,the thickness of protective layer of ACP can be further optimized when ACP is cured under about 50 ℃.展开更多
基金Funded by the National Natural Science Foundation of China(No.51678081)Natural Science Foundation of the Jiangsu Higher Education Institution of China(No.18KJB560001)。
文摘In order to facilitate self-compacting concrete to be better used in tunnel linings that can resist fires,a SiO_(2) aerogel-cement mortar coating was prepared.Based on the HC curve,a self compacting concrete cube specimens coated and uncoated with SiO_(2) aerogel-cement mortar(SiO_(2)-ACM)were heated to simulate tunnel fire for 0.5,1,1.5,2,2.5,3 and 4 h,respectively.The residual compressive strength was tested after the specimens were cooled to room temperature by natural cooling and water cooling.The results show that,the damages of specimens become more serious as fire time goes on,but the residual strength of specimens coated with SiO_(2)-ACM is always higher than that of uncoated with SiO_(2)-ACM.In addition,the residual strength of specimens cooled by water cooling is lower than that of natural cooling.However,for the specimens coated with SiO_(2)-ACM,the adverse effects of water cooling are lessened.With the increase of fire time,the protective effect of SiO_(2)-ACM is still gradually improved.Finally,a formula was established to predict the residual 150 mm cube compressive strength of specimens protected by SiO_(2)-ACM after a simulated tunnel fire.
基金Funded by the National Natural Science Foundation of China(No.51678081)Natural Science Foundation of the Jiangsu Higher Education Institution of China(No.18KJB560001)。
文摘To further strengthen the protective effect of aerogel cement paste (ACP) coating on self-compacting concrete (SCC) in tunnel fire under the optimal mix proportion,the effect of curing temperature (from 5 to 80 ℃,based on site construction curing temperature and surrounding rock temperature) on fire insulation of ACP was investigated.The mechanical properties,thermal conductivity and porosity of ACP were tested.The microstructure of ACP was characterized by means of SEM,XRD and TG/DTG.The results reveal that 50 ℃ is the optimal curing temperature for ACP with good mechanical properties and fire insulation.Relatively high curing temperature can facilitate hydration and pozzolanic reactions,contributing to the generation of more stable substances (such as C-S-H gels,tobermorite and thenardite,etc).ACP under excessive low curing temperature brings inhomogeneous microstructure with coarse pores,leading to producing wider and longer microcracks when it is exposed to tunnel fire.The microcracks make the heat convection and thermal radiation more significant and thus accelerate the damage of ACP under fire.In case of the less than 7% difference of thermal conductivity,dense microstructure and stable substances are more conducive to strengthening fire insulation of ACP.In practical engineering applications,the thickness of protective layer of ACP can be further optimized when ACP is cured under about 50 ℃.
