Smart concretes and structures are intelligent systems that have properties different from normal concrete, such as self-sensing and self-healing properties, or have the ability to react upon an ex

Smart concretes and structures: A review:

A review of some advanced sensors used for health diagnosis of civil engineering structures

Electrostatic self-assembled CNT/NCB composite fillers with high CNT aspect ratio and large NCB size is incorporated into cement-based materials to develop smart cement-based composites. The mechanical, electrical and piezoresistive properties of the cement-based materials with CNT/NCB composite fillers are investigated. Percolation equation is used to describe electrically conductive property. Electrochemical impedance spectroscopy and equivalent circuits are used to explore the conductive and mechanical mechanism. The research results show that cement-based materials with CNT/NCB composite fillers at low content present acceptable mechanical property, high conductive property and stable and sensitive piezoresistive property. The fractional change of electrical resistivity, stress and strain sensitivity of cement-based materials with 1.41 vol.% CNT/NCB composite fillers can reach 13.4%, 3.12%/MPa and 521, respectively. It is concluded that high CNT aspect ratio and large NCB size in CNT/NCB composite fillers are beneficial for improving the properties of smart cement-based composites.

Effect of characteristics of assembly unit of CNT/NCB composite fillers on properties of smart cement-based materials

The load-bearing capacity of concrete is highly influenced by the initial cement hydration process, especially in its very early age (0–48 h). Due to the rapid and intense chemical reactions between the cement and the water in the very early hydration process, it is still a challenge to monitor the cement hydration process in real time. In this paper, we investigated a stress wave-based active sensing method to monitor the cement hydration process using piezoceramic-based transducers, called smart aggregates. Using different types of the embedded piezoceramic patches, including $\text{d}_{33}$ and $\text{d}_{15}$ modes, smart aggregates can function as both the compressive and shear wave transmitters and receivers. In each mode of the smart aggregate, the active sensing approach that uses a pair of smart aggregates, one as a wave transmitter and the other one as a wave receiver, was employed. A comparative study was conducted to investigate the performance of monitoring the very early age cement hydration process by using compressive wave (P-wave) and shear wave (S-wave). A frequency domain analysis of the received signal was performed during the very early age cement hydration process. Experimental results reveal the differences of the received signal strength, valid monitoring period, and the effective frequency range by using both P-wave and S-wave.

A Comparative Study of the Very Early Age Cement Hydration Monitoring Using Compressive and Shear Mode Smart Aggregates

An experimental study on the concrete hydration process using Fabry–Perot fiber optic temperature sensors

Experimental studies on fiber optic sensors embedded in concrete

Long-term structural monitoring has become an important requisite to ensure structural and operational safety for critical civil infrastructures. Long-term structural monitoring by acquiring data c...

Development of a Real-time Remote Structural Monitoring Scheme for Civil Infrastructural Systems

In this study, stochastic analyses of pre-stress losses in two pre-stressed concrete beams are carried out, and the results of the analyses are compared with those obtained from the laboratory experimental investigations. The deterministic models given in ACI 209 (with modelling error) are used for predicting the pre-stress losses. The compressive strength of concrete, water–cement ratio, coarse aggregate–cement ratio, fine aggregate–cement ratio, cement content, initial stress in steel and relative humidity are considered as random variables. Monte Carlo simulation technique is used to determine the statistical properties of pre-stress losses at different times. From the results obtained, it is noted that while the relaxation strain can be assumed to follow a normal distribution, the frequency distributions of creep and shrinkage strains are not uni-modal. A relation for estimating total losses is also proposed in the article. The stochastic analysis approach presented in the article would be useful in the assessment of pre-stress losses in existing pre-stressed concrete members in a more rational way.

S. Sridhar

Papers

Experimental studies on fiber optic sensors embedded in concrete

Development of a Real-time Remote Structural Monitoring Scheme for Civil Infrastructural Systems

Assessment of Pre-Stress Losses in Instrumented Pre-Stressed Concrete Beams Using Stochastic Analysis