常年冻土区混凝土孔隙结冰规律对抗压强度的影响

EFFECT OF FREEZING LAWS FOR CONCRETE PORES ON COMPRESSIVE STRENGTH IN PERMAFROST REGIONS

为了探究常年冻土区混凝土孔隙结冰规律对抗压强度的影响,使用自制低温压力机测试混凝土抗压强度,并借助核磁共振仪测试混凝土中不同孔径的孔隙结冰规律。基于灰色理论分析了孔隙结冰量对抗压强度的影响规律,并建立了孔隙结冰量与抗压强度的关系模型。结果表明:0~-10℃时,混凝土毛细孔和过渡孔由于孔径较大,快速结冰,使得此温度区间内结冰量和抗压强度迅速增长。过渡孔是混凝土的主要孔隙,-10℃时99.7%的毛细孔和55.8%的过渡孔已经结冰,此时凝胶孔占比增大且不易结冰,结冰量和抗压强度增长缓慢。混凝土过渡孔结冰量对抗压强度影响最为显著,其灰熵关联度为0.985 0,基于GM(0,2)模型的混凝土抗压强度计算值与试验值的平均相对误差为3.33%。

In order to study the effect of freezing laws for concrete pores on compressive strength in permafrost regions,a self-made low-temperature compressive testing machine was used to gauge the concrete compressive strength.The laws of ice content in different size pores were measured by nuclear magnetic resonance apparatuses.Based on the grey theory,the effect of the ice content in pores on compressive strength was analyzed,and the relation model between ice content and compressive strength was constructed.The results showed that from 0 ℃ to-10 ℃,the capillary pores and transition pores freezed rapidly due to the larger pore sizes,so the ice content and compressive strength increased rapidly in the temperature range.Transition pores were the main pores of concrete.At-10 ℃,99.7% of the capillary pores and 55.8% of the transition pores had been frozen.At the time,the proportion of gel pore increased and it was hard to be frozen,so the ice content and compressive strength increased slowly.The ice content of the transition pores was the most significant influence on compressive strength,and its correlation degree of grey entropy was 0.985 0.The calculated values of concrete compressive strength based on GM(0,2) Model had an average relative error of 3.33% from the test value.