煤矸石粉混凝土冻融损伤模型与劣化机制

Freeze-thaw Damage Model and Deterioration Mechanism of Coal Gangue Powder Concrete

为促进寒区煤矸石在混凝土中的利用,通过快速冻融实验,研究了冻融循环作用下,不同取代率的机械-微波活化的煤矸石粉混凝土(Coal gangue powder concrete,CGPC)冻融损伤规律,依据波速损失对损伤层厚度进行修正,建立了基于修正后损伤层厚度的冻融损伤方程,并对冻融作用下CGPC的孔结构参数、微观形貌和水化产物进行了测试分析。结果表明:10%和20%掺量的活化煤矸石粉(Activated coal gangue powder,ACGP)能提高混凝土力学性能和抗冻性能,掺量达到30%后的抗冻性能提高效果显著减弱,力学性能有所降低;冻融300次20%和0%掺量组抗压强度分别下降了16.4%和26.5%,质量损失率分别为1.77%、4.03%,相对动弹性模量分别为68.940%、91.321%,损伤层厚度分别达到了11.9 mm和17.4 mm;基于波速差异修正后的损伤层厚度能更准确地表征CGPC损伤程度;ACGP的微粒填充作用以及二次水化作用提升了CGPC的强度和抗冻性能。

To promote the utilization of coal gangue in concrete in cold regions,this work studied the freeze-thaw damage law of mechanically-microwave activated coal gangue powder concrete(CGPC)with different substitution rates under freeze-thaw cycles.The damage layer thickness was corrected for ultrasonic wave velocity loss,and a freeze-thaw damage equation based on the modified damage layer thickness was established.The pore structure parameters,micro morphology,and hydration products of CGPC under freeze-thaw were tested and analyzed.The results show that 10%and 20%of activated coal gangue powder(ACGP)can improve the mechanical properties and frost resistance of concrete,when the content reaches 30%,the improvement effect of frost resistance is obviously weakened,and the mechanical properties are somewhat reduced.After freezing and thawing for 300 times,the compressive strength of 20%and 0%content group decreased by 16.4%and 26.5%respectively,the mass loss was 1.77%and 4.03%respectively,the relative dynamic elastic modulus was 68.940%and 91.321%respectively,and the thickness of damaged layer reached 11.9 mm and 17.4 mm respectively.The thickness of damaged layer modified based on ultrasonic velocity difference can more accurately represent the damage degree of CGPC.The particle filling effect and secondary hydration of ACGP improve the strength and frost resistance of CGPC.