基于电阻率法的水泥水化与收缩特性研究

发布时间：2018-08-25 11:02

【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。
[Abstract]:The resistivity method can be used to study the hydration characteristics of cement-based materials by monitoring the change of resistivity during hydration. Chemical shrinkage and autogenous shrinkage due to cement hydration are important factors affecting the volume stability of cement based materials. Mineral admixtures and concrete admixtures also have important effects on the hydration process and volume stability of concrete. In this paper, the resistivity method is taken as the basic research method and the cement paste as the main research object. The main contents and conclusions are as follows: (1) the chemical shrinkage of silicate cement paste has been measured by the volume method specified in the American standard ASTM C1608-07. The results show that there is a good linear relationship between the chemical shrinkage of cement paste and the hydration degree of cement, and when the age is more than 12 hours, there is a good linear relationship between the chemical shrinkage and the resistivity of cement paste. The hydration degree of cement can be predicted by the resistivity of cement paste. (2) the effect of fly ash on resistivity and autogenous shrinkage of Portland cement paste is studied. The results show that at the early stage of hydration (about 12 h before), the resistivity of cement paste increases with the increase of fly ash content, and at the later stage of hydration (about 12 h), with the increase of fly ash content, The resistivity of cement paste decreases and the self-shrinkage of hardened cement paste decreases gradually. (3) the effect of naphthalene superplasticizer on the setting process and resistivity of silicate cement paste with fixed water-cement ratio is studied. The results show that the shear strength curve of cement paste is basically consistent with the trend of resistivity change rate curve, the time of peak value of resistivity change rate curve has a good relationship with the final setting time, and with the increase of water reducer content, The compressive strength of hardened cement paste decreases and the maximum resistivity decreases gradually. (4) the variation of resistivity during hydration of sulphoaluminate cement is studied. The results show that the resistivity change curve of sulphoaluminate cement during hydration has two peaks within 1440min (24 h), and the time of peak value is not affected by the ratio of water to cement. The peak value is due to the mutual transformation between ettringite (AFt) and monosulfide calcium sulphoaluminate (AFm). For cement paste with different water-cement ratio, the resistivity of cement paste is smaller when the ratio of water to cement is higher before setting and hardening, and the resistivity of cement paste also increases when the ratio of water to cement increases after setting. The compressive strength and resistivity of hardened cement paste decreased gradually with the increase of water-cement ratio at 24 h.
【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TQ172.1

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