Abstract
Nowadays, the industrial waste, Fly Ash (FA), as a mineral admixture or a replacement of cement for the production of self-compacting concrete (SCC) has been increasingly used, because of its benefits in enhancing both fresh and long-term concrete properties and in promoting environmental-friendly construction. In this study, the conventional cement was replaced by FA at different rates (0%, 20%, 40%, 60% of the cement mass) for the SCC mixtures. The early-age (0–24 h) SCC hydration, which is a complicated chemical reaction in pozzolanic behavior, was characterized by using a pair of piezoceramic Smart Aggregates (SAs). One SA works as an actuator and the other works as a sensor. A sweep sine signal from 100 Hz to100 kHz was used as the excitation signal, which is helpful to understand the quantitative influence of fly ash on the kinetics of SCC hydration. During the hydration reaction, the received electrical signal was continuously detected by the sensor. The experimental results showed that increasing the volume of fly ash resulted in longer pozzolanic reaction time in SCCs, which successfully reveals the effect of fly ash volume on the hydration behavior in early age (0–24 h) hydration. In order to quantitatively evaluate the hydration in the 0–24 h, based on the wavelet packet energy analysis, the hydration completion index (HCI) and normalized hydration completion index (NHCI) were defined. The experimental results showed that the NHCI can clearly reveal the hydration completion progress during the early hydration age (0–24 h). To validate the accuracy of the test results based on SAs, a series of mechanical tests for penetration resistance of SCCs with different volumes of fly ash were carried out. The results predicted by the signal based on SAs gave reasonable agreement with the test results of penetration resistance. It can be concluded that a successful investigation of the influence of fly ash on early-age SCC hydration response can be achieved based on the analysis of the received electrical signal using the proposed method and the important hydration characteristics, such as initial and final setting time, and can be approximately predicted by NHCI values.
Highlights
Self-compacting concrete (SCC) is a new category of high performance concrete characterized by itsSelf-compacting ability to spread into place itscategory own weight without vibration, and characterized to self-compact concrete (SCC) under is a new of high performance concrete by without [1].high-volume fly ash, and as much as 50%, is without used to its abilitybleeding to spreadand intosegregation place under itsCurrently, own weight without vibration, to self-compact replace the cement in the [1].self-compacting concrete
SCCsResistance with different volume of fly ash, thebased initial setting investigate the of using sensing approach onand
The very early-age hydration characteristics of a series of SCC specimens were monitored by piezoceramic transducers, which enabled the active sensing approach
Summary
Self-compacting concrete (SCC) is a new category of high performance concrete characterized by itsSelf-compacting ability to spread into place itscategory own weight without vibration, and characterized to self-compact concrete (SCC) under is a new of high performance concrete by without [1]. Fresh states The of SCC with high-volume fly ash have been this mineral properties, material plays in concrete mechanical properties, durability and fresh investigated many researchers. It has been revealed experimentally by the[5,6,7]. Kong et al proposed a comparative study of the very early age cement hydration monitoring using compressive and shear mode smart aggregates using the active sensing method [35]. The authors applied an active-sensing approach using SAs based on piezoceramic transducers to monitor very early age hydration characteristics of SCC with different volumes of fly ash. By comparing the results from SAs and penetration resistance, the meaningfulness and feasibility of this test method based on SAs were assessed in the case of hydration characteristics of SCC with high-volume fly ash
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