SubstiwoodTM - Concrete Lumber

The Need

In the United States, wood lumber products have always formed the primary (and secondary) elements of many types of construction, especially in the single-and multi-family housing sector. A huge segment of the U.S. economy (on the order of 7 to 8 billion U.S. dollars per year in single-family housing alone) revolves around the common wood framing systems for walls (2x4’s or 2x6’s) and floors (2x10's, etc.). However, with the growth of the economy, the dwindling forest resources, and the emerging significance of global environmental issues such as the greenhouse effect, a need to re-assess the widespread use of wood lumber products has emerged.

The Technology

A new cementitious material, 'concrete lumber' products (Substiwood^TM) developed by Substiwood Inc. is structurally strong, durable, nailable with conventional screws and nails, and sawable using hand or electric saws. Unlike other construction alternatives to wood framing, the Substiwood^TM products essentially maintain the existing wood frame construction methods, processes, equipment, and skilled labor. They also minimize changes to the existing plumbing, electrical, and insulation procedures, materials and equipment used in wood frame construction. Substiwood products include two basic grades of "structural" and "non-structural", and a number of sub-categories within each grade. As a minimum, the allowable stresses for the structural grade products meet or exceed the corresponding allowable stresses for the STUD grade wood lumber commonly used in construction. Substiwood^TM products allow the existing methods and tools of wood frame construction (including plumbing, electrical work, etc.) to remain essentially unchanged while replacing wood lumber with an environment-friendly cementitious material based product.

Flexural load test in 16 inch span length

The Benefits

• Can be made in a great variety of colors, sizes and shapes including all dimensional lumber sizes.
• Not affected by common wood defects such as knots, bowing, etc.
• Not susceptible to termites or rotting.
• Excellent strength (flexural, compressive and shear) properties to serve as structural members and can be considered as lightweight concrete.
• Are sawable using hand or electric saws and also can be drilled.
• Could make available the highly-efficient wood-frame housing in areas of the world not possessing forest resources (such as desert areas).
• Environment friendly.
• Offer new possibilities regarding pre-fabricated panels for assembly at the building site.
• Can be utilized in a variety of applications including framing, fencing, decking, landscaping timbers, playground structures, railroad ties, etc.

Based on features above, FRP bars appear to be promising alternative to steel reinforcement in concrete structures such as marine structures, parking structures, bridge decks, highway under extreme environments, and structures highly susceptible to corrosion and magnetic fields.

Status

Substiwood, Inc. was formed in 1999 to produce, market and license a series of patent-pending cementitious material based products that replace wood lumber in construction and other applications. The company plans to begin commercial production of Substiwood for non-structural applications by approximately the end of 2000.

Barriers

Due to extensive and lengthy processes of independent testing and code approvals for structural (framing) applications of these products, the initial emphasis of the company is being focused on production and marketing for non-structural applications such as landscaping timbers, fencing, etc. However, work on the process of acquiring the necessary code approvals for structural applications will continue.

Bone-shaped Short Fiber Composite

Bone-Shaped Short Fibers

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.

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

Charles G Nutter of Silacon Corporation invented the processes and technology that produce bone-shaped fibers in high volume at low cost. verified by independent university testing that confirms the superiority of the Silacon/LANL fibers. Nutter, in addition invented Intelligent sensors for concrete and other purposes based on bone-shape derived extension of the Los Alamos National Laboratory/Silacon technology applied as multi-dimensional sensors with 'intelligence' based on magnetostriction of small linear ferrite toroidal transformer nodules and electronics that sense concurrently cracking, strain, temperature, and dielectric chemistry in concrete or plastics. The fiber and sensing technology underwent university testing at South Dakota School of Mines and Technology and University of Minnesota physics department. A patent recently issued (2011) in Nutter's name as primary inventor and James Wahlstrand as co-inventor, Lino Lakes MN. find data at http://www.silacon.com

The rest of the status can be deleted. Please correct this as several years passed without corrections after several notices. Please delete the fax number as well. I will call to follow up on the corrections. Also, your link http://rebar.ecn.purdue.edu/ect/links/tools/contact.aspx was not working.... we are trying to be helpful. What is written by your staff makes no sense.

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.

SIMCON: Slurry Infiltrated Mat Concrete

SIMCON: Continuous fiber-mat High-Performance Fiber Reinforced Cementitious Composites

First Step: Re-bars wrapped in SIMCON are put along the column to provide moment continuity through the joint region, as well as replacement of concrete with SIMCON in the anchorage region of the discontinuous bottom beam reinforcement.

Second Step: Additional layers of SIMCON mat are added to increase moment capacity at the column and beam zones facing the joint.

Third Step: the entire column (and portion of adjacent beams) is jacketed with SIMCON. Formwork is put next and mat is injected with a high-strength slurry (say 14,000 psi).

The Need

The cost of civil infrastructure constitutes a major portion of the national wealth. Its rapid deterioration has thus created an urgent need for the development of novel, long-lasting and cost-effective methods for repair, retrofit and new construction. A promising new way of resolving this problem is to selectively use advanced composites, such as High-Performance Fiber Reinforced Cementitious Composites (HPFRCCs). With such materials, novel repair, retrofit and new-construction approaches can be developed that would lead to substantially higher strengths, seismic resistance, ductility, durability, while also being faster and more cost-effective to construct than conventional methods.

The Technology

The investigations conducted in North Carolina University have demonstrated that a special type of continuous fiber-mat HPFRCC, called SIMCON which stands for Slurry Infiltrated Mat Concrete, is well suited for the development of novel repair, retrofit and new-construction solutions that lead to economical and improved structural performance.

SIMCON, uses a manufactured continuous mat of interlocking discontinuous steel fibers, placed in a form, and then infiltrated with a flow able cement-based slurry. The use of continuous mats, typically made with stainless steel to control corrosion in very thin members, permits development of high flexural strengths and very high ductility with a reduced volume of fibers.

The experimental results demonstrate that SIMCON exhibits improved properties in tension, compression, flexure and shear even when comparatively low fiber volume fraction fiber-mats are used. Furthermore, since fiber-mats are pre-packed in the plant, distribution and orientation of fibers can be more accurately controlled, than is the case with short discontinuous fiber HPFRCs. These characteristics allow for the manufacturing of a unique cement-based fiber composite that can have different yet easily controllable properties in the longitudinal and transversal directions. These material characteristics are desirable in repair/retrofit of structural elements such as columns, which require a high increase in strength and toughness in the transverse direction while increasing only ductility but not strength in the longitudinal direction (i.e., "moment-carrying" direction).

The investigations also demonstrate that SIMCON has considerable potential for both seismic repair/retrofit, as well as the development of novel, high-performance composite structural systems.

In a retrofit situation continuous SIMCON fiber-mats, delivered in large rolls, can be easily installed by wrapping around members to be rehabilitated. In new construction of high-performance composite frames SIMCON is well suited for manufacturing high strength, high ductility, and thin stay-in-place formwork elements that eliminate the need for secondary and most of the primary reinforcement.

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.

The Benefits

The presence of a SIMCON layer led to: (a) both improved structural performance and durability of the member, and/or (b) optimization of member dimensions, amount of reinforcement and member weight.

A two-dimensional layout of SIMCON and its unique manufacturing properties related to its fiber-mat configuration, open up novel possibilities for a cost-effective and improved structural performance that were not previously possible using other HPFRCCs, FRCs or any other conventional construction materials. Construction with SIMCON was also found to be simpler than if other HPFRCs, reinforced concrete, steel plates or different non-cement based composites were used. It is thus anticipated that when used in repair, retrofit, or new construction, the proposed approach will be less labor and equipment-intensive and more economical than conventional methods.

Manufacturing of SIMCON is based on the use of widely available construction equipment and building expertise, and can thus be relatively easily introduced into the field without major re-training and changes in existing construction practices. Hence, this novel type of HPFRCC provides some unique new ways of developing durable and cost-effective high-performance infrastructural systems, essential for the economic well-being of the nation in the next century.

Status

New generation of HPFRCCs made with continuous fiber-mats, called Slurry Infiltrated Mat Concrete (SIMCON) can be used in: (1) seismic retrofit, (2) the development of a novel, partially-cast-in-place High Performance Composite Frame, and (3) the development of a "self-stressing" SIMCON stay-in-place formwork that can provide active confinement after the core of the member has been cast-in-place.

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

The use of SIMCON in seismic retrofit and for new construction, and the development of self-stressing SIMCON are still under investigations. It is anticipated that, if successful, the investigations could open a new approach in developing durable and cost-effective solutions to the problems of the aging civil infrastructure, essential for the economic well-being of the nation in the next century.