掺粉煤灰和偏高岭土对高强混凝土不同温度下力学性能的影响

Effect of Fly Ash and Metakaolin Mixture on Mechanical Properties of High Strength Concrete at Different Temperature

通过掺加粉煤灰和偏高岭土制备高强混凝土,研究了其在400℃、600℃、800℃、1000℃高温热处理后的力学性能变化,并与相同强度等级的混凝土进行对比,分析其在高温混凝土领域的应用优势。试验结果表明:普通高强混凝土经600℃热处理后,表观裂纹已经非常明显,而掺粉煤灰和偏高岭土的高强混凝土表观破坏温度为800℃;掺粉煤灰与偏高领土高强混凝土的高温力学性能出现先增长后迅速降低的现象,抗压强度最大值达到125. 2 MPa,而普通高强混凝土高温处理后力学性能不断下降;普通高强混凝土随着热处理温度升高,浆体中的水化产物硅钙石、氢氧化钙不断分解,结构劣化严重,而掺粉煤灰和偏高岭土后浆体中会形成大量的耐高温相,而此过程会改善浆体中产生的部分结构缺陷,大幅度延缓力学性能退化,在1000℃热处理后浆体向陶瓷转变;掺粉煤灰和偏高领土的高强混凝土与相同强度等级的混凝土相比,在高温领域内的有着更加明显的优势,应用前景广阔。

High strength concrete( HSC) was prepared by adding fly ash and metakaolin( FAM-HSC). The mechanical properties of FAM-HSC after high temperature heat treatment at 400 ℃,600 ℃,800 ℃ and 1000 ℃ were studied. The advantages of high temperature field were explored by comparison with same strength grade concrete. The results show that apparent cracks of ordinary HSC is obvious after heat treatment at 600 ℃,while the apparent damage temperature of FAMHSC is 800 ℃ . The high-temperature mechanical properties of FAM-HSC increase first and then decrease rapidly,and the maximum compressive strength reaches 125. 2 MPa,while the mechanical properties of ordinary HSC decrease continuously after heat treatment. With the increase of heat treatment temperature,hatrurite and calcium hydroxide are decomposed and the structure of ordinary HSC is deteriorated seriously. The addition of fly ash and metakaolin result in substantial high temperature resistant phases,which improve some structural defects in the slurry. The degradation of mechanical properties is greatly delayed,and the slurry is transformed to ceramic after heat treatment at 1000 ℃ . Compared with same strength grade concrete,FAM-HSC has more mechanical properties advantages and broad application prospects in the field of high temperature.