1. Nanometers? Tiny sensors embedded in concrete will collect physical and chemical data Presented By: Ghada Mohamed Abd ElFattah By: Deborah Snoonian, P.E. Web Address: Architectural Record Digital Practice Tech Briefs Architectural Record Digital Practice Tech Briefs Topic Number: 48 Date: April 2004

2. These mini measuring devices need no external power source—they’re powered by radio waves. INTRODUCTION The National Science Foundation has awarded a grant to Advanced Design Consulting (ADC) of Lansing, New York, to develop tiny passive sensors that can be mixed into concrete to collect data on the physical and chemical characteristics that affect its strength and performance. ADC will manufacture the MEMS devices at nearby Cornell University’s NanoScale Science and Technology Facility.

3. SENSOR’S CONCEPT Microelectromechanical system (MEMS): Each device will consist of four or five MEMS sensors that measure information within concrete such as: pH. moisture. Temperature. Concentrations of chloride, sodium, and potassium ions. 1-Sensor’s Contents Radio frequency Identification Device (RFID): Used for ID and measurement purposes 2-Construction Method The devices will be encapsulated within a durable, noncorrosive material, similar to a pill, that would allow them to be mixed into concrete bridge decks, walls, or forms.

4. 3-Characteristics of the device Detecting physical and chemical changes in concrete as they occur Engineers can head off rebar corrosion and cracking before they become a critical problem.Engineers can head off rebar corrosion and cracking before they become a critical problem. Steel rebar in concrete is protected against corrosion by the high pH of Portland cementSteel rebar in concrete is protected against corrosion by the high pH of Portland cement Deterioration is kick-started when deicing salts penetrate concrete, or when carbon dioxide permeates through concrete’s pores and combines with the lime in cement to create calcium carbonate. Both of these processes upset the pH balance of the mix, which makes the steel vulnerable to decay and compromises concrete’s long-term compressive strength. Deterioration is kick-started when deicing salts penetrate concrete, or when carbon dioxide permeates through concrete’s pores and combines with the lime in cement to create calcium carbonate. Both of these processes upset the pH balance of the mix, which makes the steel vulnerable to decay and compromises concrete’s long-term compressive strength. “These devices will provide critical data for evaluating concrete performance from its freshly mixed stage to its casting, through the concrete’s service life to its period of deterioration and repair” (Eric Johnson, vice president of research at ADC). 4-How The Sensors Work will be in “off” mode when buried in the concrete, until a handheld monitor emitting radio waves passes over them then they will “kick on,” take measurements, and reradiate the information back to the monitor. The sensors will be in “off” mode when buried in the concrete, until a handheld monitor emitting radio waves passes over them then they will “kick on,” take measurements, and reradiate the information back to the monitor. The devices could be mixed randomly within a road deck or form during a pour, but for easier data collection, they would likely be placed along a linear or known distribution pattern (parallel to rebar, for instance).

5. Researchers have previously developed moisture sensors for concrete, but they have limitations when embedded in the material. Most sensors need external power, for instance, which increases their size and shortens their life span. Researchers have previously developed moisture sensors for concrete, but they have limitations when embedded in the material. Most sensors need external power, for instance, which increases their size and shortens their life span. Within the first six months of the grant period, ADC will demonstrate that the sensors can be manufactured and data collected from them without an external power source Moisture Sensors ADC’s work adds to a growing body of nondestructive inspection and measurement technologies in construction, which assess the condition of in-place materials without the need for collecting cores or samples that break the material apart. Reinforced-concrete bridge decks will serve as the first case studies for evaluating the viability of the MEMS sensors; in the future, ADC expects tiny sensors of all stripes to be viable for buildings, roads, and other types of infrastructure. Good things, it seems, will come in small packages. ADC’s work adds to a growing body of nondestructive inspection and measurement technologies in construction, which assess the condition of in-place materials without the need for collecting cores or samples that break the material apart. Reinforced-concrete bridge decks will serve as the first case studies for evaluating the viability of the MEMS sensors; in the future, ADC expects tiny sensors of all stripes to be viable for buildings, roads, and other types of infrastructure. Good things, it seems, will come in small packages. Conclusion 4-Traditional Methods Low –tech physical methods used to predict performance before or while concrete is poured, not during its service life. Slump testSlump test Cylinder testCylinder test