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Open AccessArticle

Monitoring the Whole Cycle Length Change of Cement Mortar Incorporated with SRA by CMOS Image Sensor

by Hao Wu 1,2, Yan Yao 1,2, Ling Wang 1,2, Ruijun Gao 1,2 and Shuang Lu 1,3,4,*
1
China Building Materials Academy, Beijing 100024, China
2
State Key Laboratory of Green Building Materials, Beijing 100024, China
3
School of Civil Engineering, Harbin Institute of Technology, Harbin 150001, China
4
Key Lab of Structures Dynamic Behaviour and Control of the Ministry of Education, Harbin Institute of Technology, Harbin 150090, China
*
Author to whom correspondence should be addressed.
Sensors 2020, 20(2), 468; https://doi.org/10.3390/s20020468
Received: 2 December 2019 / Revised: 9 January 2020 / Accepted: 11 January 2020 / Published: 14 January 2020
(This article belongs to the Section Sensor Materials)
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. View Full-Text
Keywords: shrinkage-reducing admixture; length change; CMOS sensor; polymerization state; cement mortars shrinkage-reducing admixture; length change; CMOS sensor; polymerization state; cement mortars
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Wu, H.; Yao, Y.; Wang, L.; Gao, R.; Lu, S. Monitoring the Whole Cycle Length Change of Cement Mortar Incorporated with SRA by CMOS Image Sensor. Sensors 2020, 20, 468.

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