Tareen Najeebullah, Kim Junkyeong, Kim Won-Kyu, Park Seunghee
Department of Civil, Architecture & Environmental System Engineering, Sungkyunkwan University, Gyonggi-do 16419, Korea.
Research Strategy Team, Advanced Institute of Convergence Technology, Gyonggi-do 16229, Korea.
Micromachines (Basel). 2019 Aug 23;10(9):559. doi: 10.3390/mi10090559.
Recently, the early-age strength prediction for RC (reinforced concrete) structures has been an important topic in the construction industry, relating to project-time reduction and structural safety. To address this, numerous destructive and NDTs (non-destructive tests) are applied to monitor the early-age strength development of concrete. This study elaborates on the NDT techniques of ultrasonic wave propagation and concrete maturity for the estimation of compressive strength development. The results of these comparative estimation approaches comprise the concrete maturity method, penetration resistance test, and an ultrasonic wave analysis. There is variation of the phase transition in the concrete paste with the changing of boundary limitations of the material in accordance with curing time, so with the formation of phase-transition changes, changes in the velocities of ultrasonic waves occur. As the process of hydration takes place, the maturity method produces a maturity index using the time-feature reflection on the strength-development process of the concrete. Embedded smart temperature sensors (SmartRock) and PZT (piezoelectric) sensors were used for the data acquisition of hydration temperature history and wave propagation. This study suggests a novel relationship between wave propagation, penetration tests, and hydration temperature, and creates a method that relies on the responses of resonant frequency changes with the change of boundary conditions caused by the strength-gain of the concrete specimen. Calculating the changes of these features provides a pattern for estimating concrete strength. The results for the specimens were validated by comparing the strength results with the penetration resistance test by a universal testing machine (UTM). An algorithm used to relate the concrete maturity and ultrasonic wave propagation to the concrete compressive strength. This study leads to a method of acquiring data for forecasting in-situ early-age strength of concrete, used for secure construction of concrete structures, that is fast, cost effective, and comprehensive for SHM (structural health monitoring).
最近，钢筋混凝土（RC）结构的早期强度预测一直是建筑行业的一个重要课题，这与缩短项目工期和结构安全有关。为了解决这个问题，人们采用了大量的破坏性试验和无损检测（NDT）来监测混凝土的早期强度发展。本研究详细阐述了利用超声波传播和混凝土成熟度的无损检测技术来估计抗压强度的发展。这些比较估计方法的结果包括混凝土成熟度法、抗渗性试验和超声波分析。随着养护时间的变化，混凝土浆体中的相变会随着材料边界限制的改变而变化，因此随着相变的形成，超声波速度也会发生变化。随着水化过程的进行，成熟度法利用混凝土强度发展过程中的时间特征反映来生成成熟度指数。嵌入式智能温度传感器（SmartRock）和压电（PZT）传感器用于采集水化温度历史和波传播的数据。本研究提出了波传播、渗透试验和水化温度之间的一种新关系，并创建了一种依赖于混凝土试件强度增加引起的边界条件变化所导致的共振频率变化响应的方法。计算这些特征的变化提供了一种估计混凝土强度的模式。通过将强度结果与万能试验机（UTM）的抗渗性试验结果进行比较，验证了试件的结果。一种用于将混凝土成熟度和超声波传播与混凝土抗压强度相关联的算法。本研究得出了一种获取数据以预测混凝土现场早期强度的方法，该方法用于混凝土结构的安全施工，快速、经济高效且对结构健康监测（SHM）具有全面性。
