【作者】 廖宜顺；

【导师】 张仲先； 魏小胜；

【作者基本信息】 华中科技大学 ， 结构工程， 2013， 博士

【摘要】 电阻率法通过监测水泥基材料在水化过程中的电阻率变化情况，可以用于水泥基材料的水化特性研究。因水泥水化而产生的化学收缩和自收缩是影响水泥基材料体积稳定性的重要因素。矿物掺合料和混凝土外加剂对混凝土的水化过程和体积稳定性也有重要影响。本文以电阻率法为基本研究方法，以水泥浆体为主要研究对象，主要研究内容和结论如下：(1)采用美国标准ASTM C1608-07规定的体积法测试了硅酸盐水泥浆体的化学收缩。研究表明，水泥浆体的化学收缩与水泥的水化度之间具有较好的线性关系；当龄期在12h以上时，水泥浆体的化学收缩与电阻率之间存在较好的线性关系，可以根据水泥浆体的电阻率预测水泥的水化度。(2)研究了粉煤灰对硅酸盐水泥浆体的电阻率和硬化水泥浆体自收缩的影响。结果表明，在水化早期阶段(约12h以前)，随着粉煤灰掺量的增大，水泥浆体的电阻率也逐渐增大；在水化后期阶段(约12h以后)，随着粉煤灰掺量的增大，水泥浆体的电阻率逐渐减小，硬化水泥浆体的自收缩也逐渐减小。(3)研究了萘系高效减水剂对固定水灰比的硅酸盐水泥浆体的凝结过程和电阻率的影响。结果表明，水泥浆体的剪切强度变化曲线与电阻率变化速率曲线的走势基本一致；电阻率变化速率曲线峰值的出现时间与终凝时间存在较好的关系；随着减水剂掺量的增大，硬化水泥浆体的抗压强度逐渐减小，电阻率极大值也逐渐减小。(4)研究了硫铝酸盐水泥水化过程中的电阻率变化规律。结果表明，硫铝酸盐水泥水化时的电阻率变化曲线在1440min (24h)内出现两个峰，峰值的出现时间基本不受水灰比的影响。出现峰值的原因是钙矾石(AFt)与单硫型水化硫铝酸钙(AFm)发生相互转变。对于不同水灰比的水泥浆体而言，在凝结硬化前，水灰比越大时，水泥浆体的电阻率越小；在凝结硬化后，水灰比越大时，水泥浆体的电阻率也越大。在24h龄期时，随着水灰比的增大，硬化水泥浆体的抗压强度逐渐降低，电阻率逐渐增大。更多还原

【Abstract】 The electrical resistivity measurement can be employed to monitor the change ofelectrical resistivity during the hydration of cement and thus can be used to study thehydration characterization of cement-based materials. Chemical shrinkage and autogenousshrinkage caused by cement hydration are the important factors that can affect the volumestability of cement-based materials. In addition, mineral admixtures and chemicaladmixtures can also play an important role in the volume stability of concrete. Theelectrical resistivity measurement was employed as a basic testing method. The maincontent and conclusions can be summarized as follows.(1) Chemical shrinkage of Portland cement pastes was measured by volumetricmethod according to ASTM Standard C1608-07. The results obtained show that therelationship between chemical shrinkage and degree of hydration is linear. Therelationship between chemical shrinkage and electrical resistivity appears to be roughlylinear after12h. It is noticed that the electrical resistivity after12h can be used todetermine the degree of hydration.(2) The evolution of electrical resistivity and autogenous shrinkage of Portlandcement pastes with different dosages of fly ash was investigated. The results show that theelectrical resistivity of the cement paste increased before setting and decreased afterhardening with the increase of dosage of fly ash. The autogenous shrinkage of thehardened cement paste decreased with the increase of dosage of fly ash.(3) The setting process and evolution of electrical resistivity of Portland cementpastes with different dosages of naphthalene superplasticizer was investigated. The resultsshow that the addition of superplasticizer to the pastes with a fixed water to cement ratio(W/C) can cause longer setting time and delay the evolution of electrical resistivity. Thefinal setting time and the occurring time of maximum rate of electrical resistivity were both delayed when the dosage of superplasticizer was increased. The compressive strengthat28days and the ultimate electrical resistivity show a same tendency for the cementpastes with different dosages of superplasticizer.(4) The evolution of electrical resistivity of calcium sulfoaluminate cement (CSA)paste within1440minutes was investigated. The results show that the electrical resistivityversus time curve occurs two peaks up to1440min. The occurring time of the two peaksseems to have no relationship with W/C. The reason for the occurring of the two peaks canbe due to the process of ettringite formation and ettringite transformation to monosulfatein the CSA hydration system. The relationship between W/C and electrical resistivity at1hour follows a negative linear trend but a positive linear trend observed at24hours. Therelationship between the compressive strength and the electrical resistivity at24hours forthe hardened cement paste with different W/C ratios follows a negative linear equation.更多还原