钢筋桁架轻质ECC-混凝土叠合板抗火性能试验研究

Experimental study on fire resistance of lightweight ECC-concrete superimposed slab with steel bar truss

轻质ECC-混凝土叠合板具有自重轻、延性高、抗裂性好等优点,具有良好的应用前景,但其抗火性能存疑。为初步探明轻质ECC-混凝土叠合板的抗火性能,对1块混凝土叠合板、4块轻质ECC-混凝土叠合板以及1块轻质ECC叠合板进行了火灾试验,又对其中的混凝土叠合板及1块轻质ECC-混凝土叠合板进行了火灾后抗弯试验,重点分析其火灾行为、火灾损伤及火灾后的受力性能。试验结果表明:轻质ECC爆裂风险明显高于混凝土,但具有优越的隔热性能,若不发生爆裂,可大大降低试件温度,实现良好的防火保护效果;钢筋桁架对爆裂具有一定的抑制作用,钢筋桁架的钢筋间距越大,钢筋桁架对爆裂的抑制效果越差;底板ECC层越薄,爆裂程度越轻;高温爆裂导致轻质ECC-混凝土叠合板的刚度和延性折减明显,但由于受火时间较短,材料退化程度有限,轻质ECC-混凝土叠合板的极限承载力较混凝土叠合板仅降低3.85%。

Lightweight ECC-concrete composite slab has the advantages of lightweight,high ductility and good crack resistance.It has a good application prospect,but its fire resistance is questionable.In order to preliminarily prove the fire resistance of lightweight ECC-concrete composite slab,fire tests were carried out on one concrete composite slab,four lightweight ECC-concrete composite slabs and one lightweight ECC composite slab,and the post fire bending test was carried out on the concrete composite slab and one lightweight ECC-concrete composite slab,focusing on the analysis of fire behavior,fire damage and mechanical performance after fire.The test results show that the spalling risk of lightweight ECC is significantly higher than that of concrete,but it has superior thermal insulation performance.If there is no spalling,the temperature of the specimen can be greatly reduced and good fire resistance can be achieved.The steel bar truss has a certain suppression effect on spalling.The greater the spacing between the steel bar truss,the worse the suppression effect on spalling.The thinner the ECC bottom layer,the lighter the spalling severity.The fire-induced spalling results in obvious reduction of stiffness and ductility of lightweight ECC-concrete composite slab.However,due to the short exposure time to fire,the extent of material degradation is limited,the residual bearing capacity of lightweight ECC-concrete composite slab is thus only 3.85%lower than that of concrete composite slab.