Carbon nanotubes (CNTs) are being used to enhance properties, including strength, in a variety of materials. For example, Portland cement can include dispersed carbon nanotubes (CNTs) for making high-performance concrete and other cement-based materials. Calcium silicate hydrate (CSH) is the main product of the hydration of Portland cement and is primarily responsible for the strength in concrete. In the cured concrete, the ultra-strong carbon nanotubes (CNTs) form nanostructures that function as nanoscopic reinforcement to strengthen the concrete. CNTs and other nanometer scale carbon particles can provide a very high number of finely-dispersed nucleation sites for CSH formation, which densifies the cured cement matrix in concrete composite materials, further strengthening the material and improving other desirable characteristics, such as lower permeation, higher abrasion resistance, and better bonding between the cement and other aggregate materials in the concrete mix. The carbon nanotubes (CNTs) or other nanocarbon particles can originally be included in an admixture, which is added to the cement. In general, admixtures are the ingredients for the concrete other than the typical cement (and supplementary cementing materials), water, and aggregate (sand and stones). Admixtures are usually liquid additives that are added before or during concrete mixing.
One problem with using carbon nanotubes (CNTs) in admixtures for concrete is that they historically have been expensive to produce. On the other hand, concrete is a bulk material that has to be produced with a low cost. It would be commercially advantageous to have the capability to manufacture admixtures for concrete that contain carbon nanotubes (CNTs), as well as other nanocarbon materials, in a cost effective and efficient manner.
Another problem with using carbon nanotubes (CNTs) in concrete is that they are difficult to effectively incorporate into the cement within the concrete. U.S. Pat. Nos. 9,365,456 and 9,499,439 to Shah et al. disclose a method for making cement compositions that incorporate carbon nanotubes (CNTs) by ultra-sonicating a mixture of a superplasticizer, water and carbon nanotubes (CNTs), to be subsequently mixed with cement. Although effective in a laboratory setting, this method is not generally cost effective for the large-scale production of concrete admixtures. In addition, this method requires additional equipment and processes for ultra-sonicating the mixture of water, superplasticizer, and carbon nanotubes (CNTs) in a relatively short time frame prior to mixing with cement, due to a short time in which the CNT suspension remains stable.
The present disclosure is directed to a method and system for making nanocarbon particle admixtures and concrete that overcomes some of the problems of the related art. The present disclosure is also directed to an improved admixture for concrete that contains de-agglomerated nanocarbon particles as well as a superplasticizer in a well-dispersed suspension that is stable for long-distance distribution and long-term storage. The present disclosure is also directed to improved concrete products made using the methods and admixtures.
However, the foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.