高温-水冷却对混凝土抗冲击性能影响试验研究

RESEARCH ON EFFECTS OF HIGH TEMPERATURE-COOLING METHOD ON CONCRETE IMPACT-RESISTANCE PROPERTIES

将C35强度等级混凝土试件在常温20℃及高温加热(200,400,600,800℃)后分别经自然冷却和浸水冷却处理后,利用波形整形器改进后的直径100 mm的分离式霍普金森压杆(SHPB)装置,对其进行不同加载率(冲击速度8.2,14.56,18.78 m/s)下的冲击压缩试验。研究表明:在同一加热温度下,随着加载率的增大,混凝土试件的峰值应力增大,相应破碎程度明显增加;而随着加热温度的提高,试件破碎由劈裂破坏向压酥破坏转变。对比分析自然冷却和水冷却处理试件的试验结果,表明:经过水冷却的试件强度在加热温度为400℃之前,等于或略高于相同加载率下自然冷却的试件强度,而加热温度高于400℃后则明显低于自然冷却的试件,因此可近似取400℃是高温水冷却损伤的阈值。通过物理化学分析得出其动力学特性影响的内在机理,主要体现在内外温差产生的内应力、二次水化反应、化学作用产生的分解和膨胀作用等。

The C35 concrete specimens were cooled by natural cooling or water immersion cooling at indoor temperature 20 ℃ and heated high temperatures（ 200,400,600,800 ℃） respectivelyr. Using improved 100 mm diameter split Hopkinson pressure bar（ SHPB） with waveform shaper,the impact compression tests were carried out under different loading rates（ bullet speeds were 8. 2,14. 56,18. 78 m/s）. The results showed that under certain heating temperature with increasing load rate,the peak stress of concrete specimens increased,meanwhile the corresponding degree of fragmentation increased significantly; and with the increase of heating temperature of the specimen,the failure mode was changed from the splitting failure to press cakes destruction. By comparing and analyzing the test results of natural cooling and water cooling process,it was indicated that before the temperature of the specimen was heated to 400 ℃,the water-cooled specimens stress was equal to or slightly higher than natural cooling specimens at the same loading rate; when heating temperature was above 400 ℃,the water-cooled specimens stress was lower than that of natural cooling specimens. Therefore,400 ℃ could be regarded as high temperature-water cooling damage threshold. Through the physical and chemical analysis,it was concluded that the dynamic characteristics affect the internal mechanism was mainly in the internal stress generated by the temperature difference between inside and outside,the second hydration reaction,decomposition and expansion generated by chemical reactionand so on.