高强承压多孔混凝土的抗冻融性能研究

Research on Freeze-thaw Resistance of High-strength Porous Concrete

透水混凝土具有较大的孔隙结构和孔隙率,冬季时在孔隙中富集水结冰会对多孔混凝土性能产生较大的影响。参照普通混凝土的抗冻融试验方法给出了多孔混凝土抗冻性试验方法和评价指标,并系统地研究了粉煤灰、矿渣、硅灰、细砂以及抗裂纤维对多孔混凝土的抗冻性能的影响。结果表明:所配制的多孔混凝土28天抗压强度为30.2~35.6 MPa,单掺粉煤灰、细砂和纤维对多孔混凝土抗冻性无改善效果,硅灰有利于提高抗冻性,掺加10.00%的硅灰,当循环次数达到60次时动弹模可达66.80%,质量损失率仅为0.35%,抗冻融指数为12.58。多孔混凝土含有较多的连通孔隙,但仍然有可能遭受水结冰后产生体积膨胀的损害,硅灰的掺入增加了C-S-H凝胶的数量,提高了界面之间的黏结力,强化界面,提高其浆体的抗冻性能。

Because porous concrete is feature with a large pore structure and porosity,the freezing of water enriched in the pores in winter will have a greater impact on the performance of porous concrete.This paper puts forward the test method and evaluation index of the freeze-thaw resistance of porous concrete with reference to those of ordinary concrete,and systematically studies the effect of fly ash,slag,silica fume,fine sand and crack-resistant fiber on the freeze-thaw resistance of porous concrete.The results show that:The compressive strength of the prepared porous concrete is about 30.2~35.6 MPa for 28 days.The addition of fly ash,fine sand and fiber alone has no effect on the freeze-thaw resistance of porous concrete.Silica fume is beneficial to improve the freeze-thaw resistance.After adding 10%silica fume,when the number of cycles reaches 60,the dynamic elastic modulus can reach 66.8%,the mass loss rate is only 0.35%,and the freeze-thaw resistance index is 12.58.The porous concrete contains more connected pores,but it may still be damaged by volume expansion after water freezes.However,after adding silica fume,the freeze-thaw resistance of slurry is improved by increasing the amount of C-S-H gel,enhancing the adhesion between the interface and strengthening the interface.