Consolidating stiff concrete mold
Hydration of cement produces a rigid, heterogeneous microstructure.
As water is introduced to cement to make a paste, which hardens over time, the main microstructural phases in the hydrated cement paste are: (1) calcium silicate hydrate gel, C‑S‑H; (2) calcium hydroxide, CH; (3) ettringite (a sulfoaluminate hydrate); (4) monosulfate; (5) unhydrated cement particles; and (6) air voids.
At all scales, concrete is a heterogeneous material.
At the normal scale, this is similar to a strength test and modulus of elasticity run on concrete pavement cores or molded cylinders made with the mixture.
In the recent research, the first theme involved understanding the micro- and nanostructures of concrete using advanced experimental tools such as atomic force microscopy, which uses a high-resolution probe to measure properties, and nanoindentation, which consists of a set of tests for investigating hardness and other mechanical properties of materials in small dimensions.
The second theme is development of a new type of self-consolidating concrete (SCC) for slipform (SF) paving processes by adding materials such as nanoclays (very small, plate-like, water-absorbent minerals) and fly ash to the composition.
The research project, which started in September 2004 and ended in August 2006, was funded by FHWA and involved a number of research themes.
The outcomes of this project led to further research focused on additional themes that are supported by multiple organizations.