Abstract
Concrete is a complex building material. Under normal curing conditions, concrete strength shows a nonlinear development process at an early age (1∼28 d). In the first few days after the completion of pouring, the strength of concrete increases slowly. Subsequently, the strength of concrete increases rapidly, reaching about 90% of its age strength. Finally, its strength gradually stabilizes. This paper introduces the experiment of 28-day concrete age strength monitoring based on embedded piezoelectric smart aggregate (SA). Two piezoelectric SAs were embedded in a concrete-filled GFRP (glass fiber reinforced polymer) tube column, one of which emitted a sinusoidal sweep signal and the other SA received the signal. With the hydration reaction of concrete, the stress wave would be significantly different when passing through concrete, and the received signal is changing constantly. Through power spectral density and wavelet packet energy analysis, the monitoring signal of concrete age within 28 days was analyzed. The experimental results show that the wavelet packet energy and power spectral density of the sensor monitoring signal show a nonlinear growth trend with time during the concrete target age. It can be divided into three stages, and the fifth day and the fourteenth day are the demarcation point of energy growth. And the trend of energy change corresponds well with the change of actual concrete strength and age. Comparing and analyzing the received signal energy of the sensor and the power spectral density function of the stress wave signal of the concrete specimen, the trend of the amplitude in the natural frequency domain is found to be the same in the three stages.
Highlights
Concrete is one of the most widely used building materials in modern buildings due to its relatively low material cost, high durability, and versatility, and its material strength is directly related to the safety of buildings
Erefore, strengthening the early strength monitoring of concrete to ensure the efficiency and effectiveness of consolidation and curing procedures are critical for attaining the full potential of a concrete mixture
From the perspective of energy and power analysis, this paper describes the combination of wavelet packet energy and power spectral density analysis in concrete age strength monitoring. rough the comparative analysis of the strength development of the whole hydration process of concrete, the early strength growth period of the three stages of concrete was found. is shows that the analysis method combining wavelet packet energy and power spectral density analysis is accurate and efficient. e result shows that it is a signal analysis method with high application value and can provide a basis for determining the strength of concrete age in engineering practice
Summary
Concrete is one of the most widely used building materials in modern buildings due to its relatively low material cost, high durability, and versatility, and its material strength is directly related to the safety of buildings. Concrete is a heterogeneous material with a complex microstructure, mainly composed of water, cement, sand, stones, and other additives. The conventionally used methods for detecting the strength of concrete mainly include the rebound method, ultrasonic-rebound method, core drilling method, pulling-out method, postanchoring method, and decompression method [2,3,4]. These methods are simple and reliable, they often cause some damage to the structure
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