China Building Materials Academy, Beijing 100024, China.
State Key Laboratory of Green Building Materials, Beijing 100024, China.
Sensors (Basel). 2020 Jan 14;20(2):468. doi: 10.3390/s20020468.
This paper introduces a new method to measure whole cycle length change non-destructively and continuously using a digital image analysis system. The macroscale length changes of mortars containing different shrinkage-reducing admixture (SRA) dosages (0%, 1%, 2% and 5% by cement weight) were first determined using a complementary metal oxide semiconductor (CMOS) image sensor under alternating dry and wet curing conditions After that, the length change was calculated using developed digital image processing technology (DIPT) software. After that, several significant conclusions could be drawn by combining with the results of systematic tests of the macroscopic and microscale physical properties of the cement mortar using X-ray diffraction, scanning electron microscopy, mercury intrusion porosimetry (MIP) and nuclear magnetic resonance (NMR) methods. The test results indicated that SRAs exhibited significant effects on the shrinkage inhibition of cement mortars, whereas the shrinkage reduction behaviour was also affected by varying the curing conditions. The MIP and NMR analyses demonstrated that SRAs reduced the irreversible shrinkage of the cement mortars by decreasing the volume percentage of the 3-50 nm pores and promoting the conversion of calcium silicate hydrate gel from an oligomeric to a high polymerization state thereby improving the volume stability of cement mortars.
本文介绍了一种使用数字图像分析系统无损、连续测量全周期长度变化的新方法。首先，采用互补金属氧化物半导体（CMOS）图像传感器，在干湿交替养护条件下，测定含不同减缩剂（SRA）掺量（水泥质量的 0%、1%、2%和 5%）的水泥砂浆的宏观长度变化。然后，使用开发的数字图像处理技术（DIPT）软件计算长度变化。之后，结合 X 射线衍射、扫描电子显微镜、压汞法（MIP）和核磁共振（NMR）等方法对水泥砂浆宏观和微观物理性能进行系统测试的结果，得出了一些重要结论。试验结果表明，SRA 对抑制水泥砂浆收缩具有显著效果，而收缩减少的行为也受到养护条件变化的影响。MIP 和 NMR 分析表明，SRA 通过降低 3-50nm 孔的体积百分比和促进硅酸钙水化物凝胶从低聚合态向高聚合态的转化，减少了水泥砂浆的不可逆收缩，从而提高了水泥砂浆的体积稳定性。
