New Concrete Technologies

Nanometers? Tiny sensors embedded in concrete will collect physical and chemical data, Architecture Record, 04.04, reports on a National Science Foundation grant for the development of tiny passive sensors for inclusion in concrete to allow long term data collection pertaining to the physical and chemical characteristics of that material.

Each monitoring device consists of four or five sensors, known as micro-electromechanical systems or MEMS. According to the developer, Advanced Design Consulting, each MEMS is no larger than the size of the period at the end of a sentence. Monitoring devices will be added to the concrete mix and can measure properties such as pH, moisture content, temperature, and concentrations of chloride, sodium, and potassium ions throughout the life of the material, starting when it is freshly mixed and up to 100 years in age. The monitoring devices have no internal power source and rather are activated, powered by, and transmit data to a handheld monitoring device.

The goal is to allow more timely and accurate assessment of chemical and physical changes in concrete, such as changes in alkalinity, that can signal the onset of rebar corrosion and deterioration in highway bridges, pavements, and other concrete structures. With early warning of such changes, repairs can be made earlier and more cheaply, thereby extending the life of the concrete structure at lower cost.

Carbon fiber reinforcement requires less cover, Concrete Construction, April 2004, reports on C-Grid, a a new carbon and epoxy based concrete reinforcing material. According to the article, C-Grid can be used for applications ranging from concrete countertops to structural precast double-tees. The product can be used in place of welded wire mesh. Because it is non-corrosive, it requires less concrete cover and therefore permits thinner, lighter concrete sections. Because of its low thermal conductivity, C-Grid is also suitable for connecting the inner and outer portions of precast concrete insulated sandwich panels without loss in R-value. Current applications use C-Grid for secondary reinforcing and shear transfer reinforcing, but not for primary tension reinforcing.

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