Reference #: 01124
The University of South Carolina is offering licensing opportunities for a non-intrusive method for detecting and classifying alkali-silica reaction in concrete structures.
Invention Description:
The invention is an algorithm for the detection and classification of alkali-silica reaction (ASR) in concrete structures. It is the first and only non-intrusive monitoring method that is used for this particular application.
ASR is a chemical reaction occurring between alkaline hydroxides within cement paste and certain types of amorphous silica found in mineral aggregates. It causes an accumulation of internal pressure due to the formation of a hygroscopic gel which leads to expansion and cracking of the concrete. This technology captures and identifies propagating damage from stress waves emitted from a sudden release of energy such as formation of cracks in concrete.
Potential Applications:
Practical applications include monitoring of buildings, highway bridges, nuclear power plants, and hydraulic structures for early damage detection and condition assessment.
Advantages and Benefits:
This technology is able to detect micro-cracks forming prior to macro-expansion, which can be related to the degree of ASR damage. Therefore, it may replace or supplement current practices that involves taking cores from the concrete structures, which may not be feasible in some cases such as in concrete containment structures within nuclear power plants.
Background:
The heterogeneous nature of concrete makes it susceptible to various deterioration mechanisms including corrosion of reinforcement, sulfate attack, alkali-aggregate reaction (AAR), freeze-thaw cycling, leaching, radiation, elevated temperatures, salt crystallization, and microbiological attack. Concrete deterioration may jeopardize the serviceability and safety of structures leading to economic losses and potentially catastrophic failures and fatalities. It is, therefore, necessary to evaluate and monitor the condition of aging concrete structures in order to predict their remaining service life.
Current methods used for assessing concrete damage in a field structure mainly rely on visual inspections performed at regular intervals. These inspections provide critical information on the structural condition; however, this information is limited to surface damage, which is qualitative and strongly depends on the experience and skill of the inspectors. In addition to visual inspection, coring is also usually required. Several tests, such as compressive strength, can be conducted on cores but their sensitivity and reliability regarding ASR may vary significantly. In fact, there is no procedure to assess and quantify damage associated with ASR.
Testing and Development:
An accelerated ASR test was designed to examine the ability of the algorithm to detect this damage mechanism. The results of this study show that this technology is able to detect ASR damage in good agreement with length change measurements. This research program is ongoing and, with the progress of testing, more data will become available to aid in the determination of damage level boundaries.