膨胀剂增强地下混凝土结构抗裂效应实测分析

以实际工程为背景,通过比较搅拌站试件试验及实际施工测试结果,分析了混凝土膨胀剂增强地下混凝土结构的膨胀抗裂效应。试件试验结果表明,掺有膨胀剂混凝土的限制膨胀率随时间变化呈现明显规律性,前3 d迅速增长并于第14 d达到峰值,随后随着时间的增加略微降低,第28 d的限制膨胀率基本保持在0.030%。现场实测的混凝土限制膨胀率随时间发展规律与试件试验相同,但其峰值相对较小。现场实测的混凝土膨胀应变相比混凝土限制膨胀率更早达到峰值,但趋势大致相同。掺有膨胀剂的后浇带及后浇式膨胀加强带能有效提高结构混凝土的膨胀应变,增强抗裂效应,距离膨胀加强带和墙体越近膨胀应变值越大。

Measurement and Analysis on Enhancing Anti-crack Property by Utilizing Expansive Agent in Underground Concrete Structure

This paper investigates the anti-crack property of concrete with expansive agents in underground concrete structure based on the comparison of field tests and concrete samples tests.The results of the test for concrete samples indicate that the restrained expansion rate (RER) of the concrete with expansive agent rapidly increases in first 3 days and reaches the peak value after 14 days,then it decreases slightly with time.The restrained expansion rate keeps a value of about 0.030％ after 28 days.Developing trend of the RER by field tests is as same as that by concrete samples tests.But the peak value and the average value of RER by field tests are smaller.Developing trend of expansive strain of concrete is as same as RER.But it is earlier for the expansive strain to reach the peak value than RER.The filed test results also indicate that post-poured strips and post-poured expansion reinforcing band with expansive agents can effectively raise the expansive strain of concrete and enhance the anti-crack property of concrete with expansion agent.The expansive strain of concrete is bigger with the closer distance with expansion reinforcing band or wall.