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  1. Free, publicly-accessible full text available December 1, 2022
  2. The remarkable mechanical properties and piezo-responses of carbon nanotubes (CNT) makes this group of nanomaterials an ideal candidate for use in smart cementitious materials to monitor forces and the corresponding structural health conditions of civil structures. However, the inconsistency in measurements is the major challenge of CNT-enabled smart cementitious materials to be widely applied for force detection. In this study, the modified tapioca starch co-polymer is introduced to surface treat the CNTs for a better dispersion of CNTs; thus, to reduce the inconsistency of force measurements of the CNTs modified smart cementitious materials. Cement mortar with bare (unmodified) CNTs (direct mixing method) and surfactant surface treated CNTs using sodium dodecyl benzenesulfonate (NaDDBS) were used as the control. The experimental results showed that when compared with samples made from bare CNTs, the samples made by modified tapioca starch co-polymer coated CNTs (CCNTs) showed higher dynamic load induced piezo-responses with significantly improved consistency and less hysteresis in the cementitious materials. When compared with the samples prepared with the surfactant method, the samples made by the developed CCNTs showed slightly increased force detection sensitivity with significantly improved consistency in piezo-response and only minor hysteresis, indicating enhanced dispersion effectiveness. The new CNT surface coatingmore »method can be scaled up easily to cater the potential industry needs for future wide application of smart cementitious materials.« less
  3. Weight data of vehicles play an important role in traffic planning, weight enforcement, and pavement condition assessment. In this paper, a weigh-in-motion (WIM) system that functions at both low-speeds and high-speeds in flexible pavements is developed based on in-pavement, three-dimensional glass-fiber-reinforced, polymer-packaged fiber Bragg grating sensors (3D GFRP-FBG). Vehicles passing over the pavement produce strains that the system monitors by measuring the center wavelength changes of the embedded 3D GFRP-FBG sensors. The FBG sensor can estimate the weight of vehicles because of the direct relationship between the loading on the pavement and the strain inside the pavement. A sensitivity study shows that the developed sensor is very sensitive to sensor installation depth, pavement property, and load location. Testing in the field validated that the longitudinal component of the sensor if not corrected by location has a measurement accuracy of 86.3% and 89.5% at 5 mph and 45 mph vehicle speed, respectively. However, the system also has the capability to estimate the location of the loading position, which can enhance the system accuracy to more than 94.5%.
  4. Steel, which has high tension and compression strength, is a widely used civil engineering material in constructing building, bridge, pipelines, and other structures. However, steel has a well-known weakness, which is suspected to corrosion. Steel corrosion would significantly impact the reliability and safety of steel structures. Accurately locating and assessing the corrosion of steel structures would contribute to timely maintenance and thus, extend the service life of the steel structures. Although advances have been made to use nondestructive evaluation (NDE) technologies to locate and assess corrosion on steel structures, due to the lack of labor and budget for frequent NDE assessment on steel structures, remote and real-time approaches to locate and assess corrosion are still in great needs. Fiber optic sensors, especially, fiber Bragg gating (FBG) sensors, with unique advantages of real-time sensing, compactness, immune to EMI and moisture, capability of quasi-distributed sensing, and long life cycle, will be a perfect candidate for long-term corrosion assessment. However, due to the fact that FBG is a localized sensor, it is very challenging to locate corrosion using FBG sensors. In this study, algorithms are developed to locate corrosion on steel structures using FBG sensors. Detail sensing principle, localization algorithm development and calibrationmore »are introduced in this paper together with experimental validation testing. Upon validation, the developed corrosion localization algorithm could give some guidance to locate corrosion using in-situ FBG sensors on steel structures across nation and would possibly reduce the corrosion induced tragedies.« less