No abstract

The development and test of a smart RFID-based corrosion sensor is presented. The sensor has a small size (5 cm x 3 cm x 1.8 cm) allowing it to be embedded in concrete or other construction materials. The corrosion sensor is built around a low-power microcontroller which enables multiple and complex measurements to take place. The sensor is totally passive and it does not require batteries. Its power supply is derived from an electromagnetic field transmitted by an external RFID reader. This field is also used for data communication. The sensor contains a potentiostat that is used to perform linear polarization measurements on a corrosion cell. The sensor can also measure temperature and its own supply voltage. Unlike existing embeddable corrosion sensors, the developed sensor can acquire full polarization curves with a resolution of 10 bits. The sensor can communicate with ISO-15693 compliant RFID readers.

Using a dSLR camera with macro LED light, 11 samples containing light and moderately cracked concrete surfaces were imaged with perpendicular and angled illumination. Textural features from gray level co-occurrence matrix statistics were derived, from which 3-6 salient features were selected. Cross validation accuracies were as high as 94% using neural network classifiers, indicating the feasibility of rapid, automatic concrete cracking assessment using COTS digital imaging.

Experience has shown that many aspects of experimental design for studying steel corrosion in cementitious systems may significantly influence the obtained results. In the absence of standardized methods to study steel corrosion in concrete, researchers usually define their own test setups, which partially explains the large scatter and uncertainty in the aggregated published data.

Concrete bridge approach slabs (BASs) are used at the interface between bridge abutments and pavements that rest on compacted embankment. The objective of the research presented here was to develop optimal-cost BAS designs for new and replacement slabs. Two solutions presented here included (a) cast-in-place (CIP) design for new construction and (b) novel, precast, prestressed (PCPS) slab designs for new construction and replacement of BASs. The practices of state departments of transportation (DOTs) with respect to BASs were evaluated and compared with those of the Missouri DOT. On the basis of the practices, a 20-ft span was chosen and finite element models were analyzed to consider different slab lengths, thicknesses, and loss of support conditions to calculate maximum moments, deflections, and end slopes. On the basis of predicted values, CIP and PCPS design alternatives were recommended. Recommended alternatives were estimated to have a lower cost and a performance equal to or better than the current Missouri DOT designs. A new study has been initiated in which the recommended BAS designs are to be implemented in the field.