BACKGROUND
Concrete derives its strength from calcium silicate hydrate, a product of the hydration reaction that takes place when water is mixed with cement. A process known as curing, which involves providing continuous moisture and maintaining or providing heat to the concrete mixture, promotes the formation of calcium silicate hydrate. Curing conditions can impact the development of the calcium silicate hydrate microstructure. This in turn affects the properties of the cured concrete, such as porosity, permeability, shrinkage, creep, and strength. To optimize curing conditions, it is beneficial to continuously monitor the conditions of the concrete mixture at various depths to ensure that desirable levels of moisture exist throughout the mixture. This kind of real-time monitoring is difficult to achieve without removing a portion of the curing mixture for testing, which takes time and is destructive to the final concrete structure. Also, these destructive tests measure at one point in time and do not provide insight into the continuous changes of the material. For example, curing conditions can be determined by removing a portion of the structure at a point in time and measuring the porosity, diffusion coefficient, or the degree of saturation at different depths but this is only done after the structure is complete.
SUMMARY OF TECHNOLOGY
OSU Researchers took advantage of a discovery relating to correlations among the physical properties of concrete systems undergoing different curing methods. One of the unexpected results is that the moisture content and other properties in a curing concrete mixture may be instantaneously quantified during the early stages of the reaction. Tests measured the electrical impedance at various depths within curing concrete samples undergoing dry curing, sealed curing, and wet curing. The gradient in the electrical signal correlates to the gradient in the moisture of the samples. Because the moisture content is different at different depths, the properties of the concrete also vary with depth. Various properties of the samples, including porosity, degree of saturation, rate of heat exchange, diffusion coefficient and tensile strength, were compared with the electrical impedance data. A strong correlation was found. One of the unexpected results is that electrical impedance provides a quantitative measurement giving meaningful insight into the characteristics of curing concrete mixtures. Particularly, electrical impedance has the potential to examine curing methods and the corresponding impacts on the concrete microstructure, strength, and other properties.
POTENTIAL AREAS OF APPLICATION
MAIN ADVANTAGES
- Low cost
- Works without the need to remove or otherwise deface or destroy a portion of the curing concrete mixture
STAGE OF DEVELOPMENT
- There is a Working Model for this technology.