Emerging Construction Technologies - Bone-shaped Short Fiber Composite

Emerging Technologies outside Civil, Mechanical, and Electrical

Bone-shaped Short Fiber Composite

The Need

Civil engineers use steel, fiberglass and other similar materials to increase concrete's strength and toughness, but using those materials often requires costly construction techniques. Short-wire reinforced concrete should become a favorite technology since the process is compatible with standard construction processes and the steel used for the bone-shaped fibers is relatively cheap. Researchers at Department of Energy's Los Alamos National Laboratory have discovered that enlarging the ends of small fibers mixed into concrete substantially increases the material's overall strength and toughness.

Bone-Shaped Short Fibers

The Technology

The Los Alamos researchers, led by Yuntian T. Zhu, found that adding 1 % bone-shaped fibers to concrete can increase its maximum strength up to 84 percent, and its toughness up to 93 times. The finding has solved a problem of getting effective load transfer between fibers and the surrounding matrix without making the composite more brittle, as happens when the fibers are tightly bonded to the matrix.

The bone-shaped fibers can help concrete to carry the load. This special fibers anchor into the matrix at each end because of their shape but bond only weakly with the matrix along their length. The researchers also optimized the shape and size of the enlarged fiber ends, so they don't experience the stresses that usually snap fibers and limit a short-fiber composite's performance.

Comparison between Straight and Bone-shaped Fiber

Straight fibers can pull free of the matrix material if the fibers bond weakly with the surrounding matrix. On the other hand, if the fibers bond strongly with the matrix, they can snap under the high stresses generated by a crack in the matrix. The bone-shaped fibers connect mechanically with the matrix predominantly at their ends. They have a weak interface, and so don't experience extreme stress, but remain anchored at their ends and so still help carry the load felt by the composite.

The bone-shaped fibers promote significant plastic deformation in bridging ligaments and the formation of multiple cracks. Multiple cracking is another effective mechanism for improving the composite toughness. Distributed multiple cracking allows more bridging bone-shaped fibers to plastically deform.

Good Bridging and Multiple Cracking of Bone-shaped Fibers Composite

The Benefits

Compare to the straight-fiber concrete, the one containing the bone-shaped fibers is significantly much better in both toughness and strength. The bone-shaped fibers concrete resisted the propagation of cracks better. The fibers bridge the crack and refuse to let go. Close inspection showed that even though a crack in the concrete matrix had snaked through the sample, the sample remained intact. The bone-shaped fibers also promote significant plastic deformation in bridging ligaments and the formation of multiple cracks.

Status

Silacon Valley Corporation invented the methods and fixtures that produce bone-shaped fibers in high volume at low cost. Silacon Valley invented Intelligent Concrete based on bone-shape derived extensions of the bone fiber technology as multi-dimensional related smart aggregates. Silacon invented MagneMix, a silane and cement chemistry additive, treated iron ore concentrate, smart bone fibers, and flyash aggregate MagneMix in 55-lb bags. Silacon also added 'intelligence' to bone-shaped fibers and derivatives by applying Giant Magneto Resistance (GMR) sensors to monitor permeability changes due to magnetostriction directly related to stress, cracking, strain, temperature, and chemistry of concrete. The Silacon MagneMix can be conductive and very light in weight due to the light weight flyash aggregate. By its very nature MagneMix absorbs electromagnetic radiation extremely well and is an excellent choice for abatement of nuclear radiation. Silacon hopes to be the world's source of Intelligent concrete mixes and bone shaped fiber derived Smart Aggregates. Patent work is filed with the USPTO.

Silacon sought assistance from Los Alamos National Laboratory and The Department of Energy to develop further high performance concrete. The Government is funding the DOE to provide new technologies to rebuild the Nation's bridges, dams and government structures.

Barriers

Although this technology has been through extensive laboratory testing, no full scale test or project implementing this technology to the real structures reported yet.

Points of Contact

Charles G. Nutter, CEO, Silacon Valley Corporation, Phone: (651) 738-1965, Fax: (651) 738-1636, E-mail: sales@silacon.com
Yuntian T. Zhu, Material Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545, Phone: (505) 667-4029, Fax: (505) 667-8021, E-mail: yzhu@lanl.gov.

References

Innovative Fiber Composites, Los Alamos National Laboratory, http://www.lanl.gov/mst/fibers/fibers.html
Silacon Valley Corporation Home Page, http://www.silacon.com

Disclaimer Statement

Neither the Construction Industry Institute nor Purdue University in any way endorses this technology or represents that the information presented can be relied upon without further investigation.

MA43