July 2012 - Resolution Comparison on Concrete Porosity
Comparative Resolution Scans of Concrete on the SkyScan 1173 MicroCT
The focus of this preliminary study was to determine the best resolution setting for scanning the concrete samples to optimize scan time and sample throughput in the SkyScan 1173 High Energy Desktop MicroCT. Given the nature of concrete a larger number of samples must be scanned for statistically significant.
"In the future we hope to use computed tomography to scan beams before and after testing to see where cracks originate, and how they propagate through the sample."
----- Brett Williams, U.S. Army Corps of Engineers, U.S. Army Engineer Research & Developement Center (ERDC), Vicksburg, MS
The sample shown is a cross-section of a 1" x 1" x 6" flexure beam made out of self-consolidating concrete (SCC). Self-consolidating concrete, also known as self-compacting concrete, is a highly flowable, non-segregating concrete that spreads into place, fills formwork, and encapsulates even the most congested reinforcement, all without any mechanical vibration. It is defined as a concrete mix that can be placed purely by means of its own weight, with little or no vibration. As a high-performance concrete, SCC delivers these attractive benefits while maintaining all of concrete's customary mechanical and durability characteristics. Adjustments to traditional mix designs and the use of superplasticizers creates flowing concrete that meets tough performance requirements. If needed, low dosages of viscosity modifier can eliminate unwanted bleeding and segregation.
Since its inception in the 1980s, the use of SCC has grown tremendously. The development of high performance polycarboxylate polymers and viscosity modifiers have made it possible to create “flowing” concrete without compromising durability, cohesiveness, or compressive strength. The flowability of SCC is measured in terms of spread when using a modified version of the slump test (ASTM C 143). The spread (slump flow) of SCC typically ranges from 18 to 32 inches (455 to 810 mm) depending on the requirements for the project. The viscosity, as visually observed by the rate at which concrete spreads, is an important characteristic of plastic SCC and can be controlled when designing the mix to suit the type of application being constructed.1