Monday, July 16, 2012

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.

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.

Alternative Material Dowel Bars for Rigid Pavement Joints

Alternative material for composite dowel bar

The Need

Over the last thirty to forty years, dowel support of the joint in Rigid Joint Pavement (RJP) has been widely used. Because the joint dowels are at the edge of the slab, they are subject to drainage exposure of the metal to road salts and moisture. The exposure often results in corrosion of the metallic dowel itself. As the dowel must be free moving to transfer the wheel loads of traffic from one slab to the next, corrosion product can lock the dowel in place defeating its purpose. This forces the load onto the concrete itself at the slab edge resulting in excessive stresses which crack and spoil the joint edges. The cracking and deterioration of the joint eventually results in the replacement of the entire slab or the replacement of the concrete near the joint area. If corrosion damage to the dowel bar could be eliminated, pavement life could be extended with major cost savings accruing to the owner from reduced rehabilitation costs and/or replacement of the pavement.

The Technology

The problem of deterioration of concrete pavement joints has resulted in the search for alternate solutions. Fiber-reinforced polymer (FRP) and stainless steel represent corrosion resistant alternatives to conventional galvanized steel in this application. Stainless steel have very good resistance to chlorides. This is a necessity since heavy use of road salts in the northern United States and Canada have resulted in pavement and joint deterioration. States such as Ohio, New Jersey and Pennsylvania during the l980s and early 1990s had limited experimentation with stainless or stainless clad dowel bars. However, no fully encompassing performance analysis of the performance of these joints was done relative to alternative materials. The recently study by the FHWA of Alternative Materials for Highway Construction demonstrated the outstanding corrosion resistance of stainless steel as compared to many other construction alternative materials such as copper, galvanized, nickel coated and epoxy coated products. Further, as this is a moving part the material used must have good abrasion resistance. Coated products run the risk of the outer corrosion resistant layer of material being worn away or otherwise damaged. The study demonstrated that even with extended wet-dry cycles of exposure to fluids of high chloride content, at various temperatures and PH levels, stainless steel had corrosion resistance hundreds and in many cases thousands of times the corrosion resistance of the alternative materials tested. The ongoing nature of the corrosion problem in highway joints and dowel bars and the recently reported results of the study has renewed interest in using stainless steel in this application.

The Benefits

High General Corrosion Resistance Chloride Resistance
Ductility at low temperatures
Fire and Heat resistant
Superior Shock and Seismic Loading Resistance
Minimum Maintenance
Resistant to Localized Corrosion
Mechanisms (Crevice, pitting, stress corrosion)
Superior Strength Levels
Ease of Storage in field
No Special Coating Required
Abrasion Resistant
Long Shelf and Service Life

Status

Several states including Wisconsin, Iowa, Illinois, Kansas and Ohio have volunteered to put in significant runs of pavement using solid stainless bars or a dowel consisting of a welded tube (0.165 inches thick) filled with a grout center. The program will be run in conjunction with the Federal Highways Administration High Performance Concrete Program. In 1998 and 1999 installations of dowel bars have been completed in various states. Additional installations are expected in Kansas, Pennsylvania and Minnesota.

Barriers

The barriers to further and continued use of stainless dowels bars are primarily two.

Obvious higher initial cost of stainless steel whether supplied as a solid stainless bar or a composite material with a stainless outer shell and a center of grout, concrete or carbon steel.
Difficulty of assessment on the breath and cost of current practices: Although corrosion of the dowel and freezing of the dowel within the joint is recognized as a primary cause of joint failure and distressed joints in rigid joint pavement, there are other factors involved in many failures.

Due to the lack of data in most DOTs to make an engineering assessment of the cost of corrosion associated with the failures and subsequent repairs, it makes it difficult to present a savings figure to offset the higher initial cost of stainless. In addition the availability of composite products has not been widespread until recently and even then carbon steel centered products must be imported.

Snap Joint Technology for Composite Structures

Snap Joint Design

Composite Transmission Tower

Truss Joint

Eighteen Story All-Composite High Rise

The Need

For the past few decades, the Aerospace industry was the major users for polymer composites. In the majority of the aircraft composite structural components, both bolted and/or adhesive bonded joint was used. Most of the details are similar to those for metal joints. It was shown from extensive testing on bolted composite joints that failure always occurs in a catastrophic manner due to high stress concentration developed at the bolt locations. Due to the inherent low bearing and interlaminar shear strengths of composites, these stress concentrations threaten the downfall of ever piece of the composite structure.

The Technology

The optimum composite joint design is the one capable of distributing stresses over a wide area rather than to concentrate them at a point. Adhesively bonded joints can satisfy these requirements, however, most of the adhesives are brittle, and brittle failure is unavoidable. This was the motivation of developing what is called the SNAP joint.

The snap joint technology developed by W. Brandt Goldworthy & Associates, Inc. The concept is based on similar joining technology used for connecting wooden parts (wood is considered as natural orthotropic composites). Also, this technique is very similar to techniques which were used a decade or so again for plastic.

The following figure shows a pultruded structural composite member (A) with one end shaped as a fir-tree, and therefore has a large load bearing area. In this figure, part (A) has been snapped into another structural shape (B). From these figures, on can see that the later shape has been designed to combine its structural shape with functionality that allows for the engagement of the load-bearing surface of member (A). It is possible to "snap" joint both parts together since part (A) has been cut for a short distance along it length to provide enough lateral flexibility to move out of the way when entering part (B). In order to make this joining concept successful, the fiber architecture of part (A) must be designed in such a way that the load bearing surfaces have higher interlaminar shear strength capacity. Also, it can be noticed from the figure, that a circular hole was introduced at the end of the horizontal slot of part (A) to inhibit the crack propagation along the length of the pultruded member.

Snap Joint Concept

Hardware for fasternerless snap joint

The Benefits

The applications of this technology in composite structures will have benefits as follow:

The structures are easy to assembly.
Installation of structure members become faster.
Installation needs smaller number of labor and equipment.
Since it use composite materials, its weight is less than traditional structures.

Status

The first prototype or "Demonstration project" using this joining method was in designing and construction of three Transmission Tower Structures near Los Angeles by W. Brandt Goldworthy & Associates, Inc. and Ebert Composites Corporation. The 1999 CERF Charles Pankow Award for Innovative Applications was granted to the developers for this innovative composite transmission tower.

The developers have also proposed an 18-story all-composite structure as a stack & checkout tower for rockets at Commercial Spaceport, USKA, Vandenberg Airforce Base, California. According to the developers, the estimated cost of this structure is about 20 million dollars including machinery cost.

This year, through California Department of Transportation (Caltrans), they have proposed the design and the construction of a truss structure to carry highway singes. The project was submitted as a part of the Federal Highway T-21 program.

More details discussion on this emerging joining technique as well other similar techniques will be presented in the separate Chapter in the ASCE Connection Design Manual which I am writing, and which is expected to be published by the Middle of year 2000.

Barriers

The snap joining technique is considered to be one of the optimum techniques to join composite structural members. However, it has a major limitation, and can only be used in specific applications. That is, this method can only be used to transmit axial loads, which make it ideal for truss-type structures. However, in my opinion, this method should NOT be recommended when out-of-plane loads or any shear loads are introduced since the connection is not design to carry any major bending moments. Under flexural loads, it is expected that the joint will be very flexible, and the artificial cracks introduced to members will propagate and a complete failure will occur even under moderate service flexural and/or shear loading.

More details discussion on this emerging joining technique as well other similar techniques will be presented in the separate Chapter in the ASCE Connection Design Manual, and is expected to be published by the Middle of year 2000.

CP40: FRP/Concrete Piles

CP40 piles used for Berths 20A and 20B and FRP bracing for Pier C at the Brooklyn Navy Yard.

Fabricated Near-Site, Handled & Installed Using Conventional Equipment & Techniques

US Naval Base, Ingleside TX. Fendering & Load-Bearing Applications, EMR Facility Pier.

The Need

CP40 is a FRP/concrete composite post, pole, or pile which matches the strength of traditional materials -- metal, wood, or concrete -- without sharing their vulnerability to corrosive factors in their site environments.

CP40 is a round, vertical, structural element for use in corrosive outdoor environments. Strong, corrosion-resistant marine piling (8” to 24” outside diameter, and larger) is needed in waterfront infrastructure & structures such as locks/dams, canals, docks, piers, marinas, etc. Strong, corrosion-resistant fence and sign posts (2” to 4” outside diameter) are needed for facility/property perimeters and highway applications where groundwater, shorefront, de-icing, etc. conditions rust, rot, or corrode traditional materials.

The Technology

CP40 consists of three components, namely, a hollow fiberglass-reinforced-plastic (FRP) tube, a concrete core, and a durable environmentally-neutral coating. The core and tube contribute compressive and tensile strength respectively to the structural element. Since the core is expanded in the tube, sufficient bond is produced for the two materials to act in a composite manner. In brief, the core prevents crush/buckle of the tube, and the tube protects the core from corrosive factors in the environment. The durable coating serves as a redundant defense of the FRP against ultraviolet rays.

CP40 can be fabricated, handled, driven, and connected using industry standard equipment, tools, hardware, and techniques.

The Benefits

CP40 has the strength required of traditional materials, but serves longer in harsh conditions such as those of the marine environment. CP40's advantages over traditional piling materials (wood, concrete, steel, aluminum) include:

cannot rot, rust, or corrode
not subject to marine borers and ship worm damage
uniform piles available in any length, in any quantity
easy to handle and drive
electromagnetically invisible
no hazmat
low/no maintenance
color available
greatly extended service life
reliable design loads
off-the-shelf product with established standard performance

Status

By 1997 R&D goals were essentially achieved and preliminary commercialization began with a focus on demonstration type projects. Lancaster concentrated on marketing large diameter piles, primarily for marine applications where steel, aluminum or wood products are seriously deficient. Lancaster has developed extensive awareness of CP40 marine piling among buying agencies and designers of waterfront structures. Many waterfront structures have been built using CP40. Through these successful installations, Lancaster has demonstrated that the large diameter CP40 product has sufficient structural integrity to serve as both a fender pile for large vessel docks and as a load-bearing structural pile for major piers, etc. New application-specific engineering and the development of even larger outside diameter piling is ongoing.

The piling market offers proven, immediate, and significant opportunities for Lancaster's CP40. To date $4.2 million in sales have been booked and produced.

Patent protection has been achieved and is being expanded. A total of five patents have been issued and presently control the strategic intellectual property necessary for full commercialization in North America and Europe.

Lancaster Composite has developed, patented, and demonstrated markets for CP40. Lancaster is now launching the full-scale commercialization of CP40 piling. Lancaster Composite is seeking a partner or partners who can join this full-scale commercialization campaign on a national and international level.

Barriers

Engineers are unfamiliar with the new material. Though CP40 offers many advantages over traditional piling materials, it often carries an initial price premium. Procurement is often not based on life-cycle values.

For any new material to gain a large market position, it must ultimately be included in standard guide specifications and on pre-approved product lists. In 1995, Lancaster began a campaign to overcome this barrier by presenting CP40 to master specification organizations and buying agencies. To date the composite post has been specified by dozens of different agencies including, the Federal Highway Administration, the Federal Aviation Administration, the United States Navy, the U.S. Army Corps of Engineers, State Departments of Transportation and many other large using agencies such as ports.

Demand exists in the U.S.A. and abroad for large quantities of CP40 posts and piles to be used on many separate structural and infrastructural projects. This large, wide-spread potential in itself constitutes a barrier to full-scale commercialization. Fortunately, since CP40 can best be made available through near-site production rather than from a central location, all that is required to overcome this barrier is the participation of a national firm, or team of firms, with existing channels to the waterfront (and foundation) markets for construction materials.

Superpave System

The Superpave Gyratory Compactor (SGC) specimens are sawn to produce 150 millimeter diameter by 50 millimeter thick test specimens.

The Indirect Tensile Tester (IDT) measures the creep compliance and tensile creep of hot mix asphalt. These test results can be related to low temperature and fatigue cracking.

The Need

The Superpave is the acronym for 'SUperior PERforming Asphalt PAVEments' system. It was developed by Strategic Highway Research Program (SHRP) to give highway engineers and contractors the tools they need to design asphalt pavements that will perform better under extremes of temperature and heavy traffic loads. Using the Superpave system, materials and mixes can be designed to reliably perform under any conditions of load and environment. The Superpave system was developed under three objectives: 1) to investigate why some pavements perform well, while others do not, 2) to develop tests and specifications for materials that will outperform and outlast the pavements being constructed today, and 3) to work with highway agencies and industry to have the new specifications put to use. Asphalt Pavements account for more than 90 percent of all paved highways in the United States, and annual expenditures for asphalt pavements top $10 billion. If asphalt pavements can be designed to last longer, we stand to reap substantial benefits

The Technology

The Superpave system consists of three interrelated elements: 1) asphalt binder specification, 2) volumetric mixture design and analysis system and 3) mix analysis tests and a performance prediction system that includes computer software, weather database, and environmental and performance models. Superpave includes a new mixture design and analysis system based on performance characteristics of the pavement as a multi-layers system with a tiered approach based on expected traffic. Superpave system primarily addresses three pavement distresses: 1) permanent deformation, which results from inadequate shear strength in the asphalt mix at high pavement temperatures, 2) fatigue cracking, which occurs mainly because of repeated traffic loads at intermediate pavement temperatures, and 3) low temperature cracking, which is generated when an asphalt pavement shrinks and the tensile stress exceeds the tensile strength at low pavement temperatures. For the design of asphalt paving mixtures under heavy traffic loading, the Superpave system uses different performance-based tests and distress prediction models to supplement volumetric mix design procedures.

The Benefits

The Superpave system selects materials and designs the mixture to minimize permanent deformation, fatigue cracking, and low temperature cracking in the Hot Asphalt Mixtures (HMA). Implementation of the Superpave technology offers significant potential for mitigating pavement performance problems such as extreme temperatures, environmental conditions, traffic impacts of transit operations, and frequent stopping and turning maneuvers. The potential cost savings, improvement in service levels and the extension of pavement service life is great. Superpave improves the correlation between material properties and pavement performance. And the Superpave binder grading system is a useful tool for predicting the performance of flexible pavements. The system evaluates the binders' abilities in resisting rutting, fatigue and low temperature cracking based on their theological properties at the anticipated pavement temperatures.

Status

The SHRP introduced the Superpave system in 1992. The Federal Highway Administration (FHWA) assumed responsibility for further development and validation of the Superpave specifications and test procedures, and initiated a national program to encourage the adoption of the Superpave system. Most highway agencies have indicated that they intend to implement the Superpave asphalt binder specification in 1997. The final developments of the binder specification and equipment specifications are still underway. This development work should not impede the implementation process. As the Superpave specification is evaluated minor changes and refinements will be made to correct errors and omissions. This will be a continuing process. The Superpave system offers a major improvement in asphalt materials evaluation and mix design. Superpave binder and mixture specifications are currently being reviewed for their applicability to modified asphalt binders and for especial asphalt mixtures such as asphalt recycled materials.

Barriers

The Superpave technologies is under development by many research organizations such as regional superpave centers, FHWA, Asphalt Institute, NCAT, NAPA. As Superpave technology is based on the more restricted properties and specification of aggregate and binder than traditional methods, it needs to be implemented by more exact procedure, QA/QC for keeping quality and training for Superpave system users. Accordingly, cost is relatively expensive than traditional one.

Modular FRP Composite Bridge Deck

Beams are installed at site

High performance adhesive bonding is applied to beam surface

Prefabricated SuperdeckTM is installed using minimal equipment

On-site assembly takes only a few hours

The Need

The bridge infrastructure of the United States is in constant need of repair and rehabilitation. It is reported that 43% of the bridges in the USA have been identified as being structurally deficient or functionally obsolete due to corrosion. Corrosion is a major problem specially when deicing has to be done. The repair of concrete and timber bridge decks is a time consuming and costly exercise. Bridge repairs also causes safety hazards and traffic delays. The need for a cost effective and efficient method for replacing and repairing bridges cannot be overemphasized.

The Technology

Superdeck^TM, a non-corrosive fiber reinforced polymer (FRP) composite bridge deck. The Deck is designed and engineered into a lightweight, strong and rigid structure that will not corrode. The deck sections, composed of hexagon and double-trapezoid profiles, are bonded with a high-strength adhesive under controlled conditions in the manufacturing plant.

The H-deck components are placed transversely to the traffic direction and supported by longitudinal steel or composite beams. Beams can be spaced up to nine feet apart.

The Benefits

It can replace deteriorated concrete or timber bridge deck.
Cost effective on an installed cost basis.
Field assembly of deck modules takes only hours to complete.
Safety is enhanced as minimal equipment and formwork is needed, and long traffic delays are eliminated.
Good fatigue resistance and high strength-to-weight ratios yield high durability.
Corrosion-resistant and maintenance free material eliminates the number of future replacements.
Contains zero metal reinforcements eliminating corrosion due to deicing materials.
Complies with the American Association of State Highway & Transportation Officials (AASHTO) HS 25 Highway Bridge Design.

Status

This technology was honored as one of 1999 Nova Award Finalists by Construction It won the Industry Recognition Awards as finalist, the CERF Charles Pankow Award for Innovation in 1997, and the Market Viability Award from the Composite Fabricators Association in 1997.

It has being installed in many locations: County Road 26/6, Lewis County, Virginia; The Ohio to Erie trail, Xenia, Ohio; County Road 26, Taylor County, West Virginia; Route 4003, off Route 31, Somerset County, Pennsylvania.

Superdeck^TM is currently undergoing a Highway Innovative Technology Evaluation Center (HITEC) product evaluation. HITEC is Civil Engineering Research Foundation (CERF)'s service center and clearinghouse for implementing highway innovation.

Barriers

There are no long-term studies on the performance of the bridge since it is a new construction material and technology.

Composite Materials

SNAP-TITE Composite Column Reinforcement

Beams are installed at site

High performance adhesive bonding is applied to beam surface

The Need

Recent earthquakes throughout the world have demonstrated the vulnerabilities of older reinforced concrete columns to seismic deformation demands. During earthquakes, seismic forces cause concrete to crack and expand. Steel rings inside the column must resist these forces, but have failed during recent earthquakes. These reinforced concrete columns with substandard reinforcement details and major corrosion problems must be strengthened.

Previous technology consisted of concrete or steel jackets. Although effective, these techniques are costly, time consuming, and require their own maintenance as well. Following major earthquake damage to bridges and overpasses in 1989, the California Department of Transportation identified 1,039 bridges that were in need of seismic retrofitting to prevent spalling and catastrophic failure during earthquakes. After the 1994 Northridge earthquake, another 1,325 bridges were added to the list. The need for a more cost effective and user friendly system was imminent.

The Technology

The Snap Tite Composite Column Reinforcement strengthens a concrete column by confining it in an external composite jacket, which prevents the concrete from expanding during seismic activity or prolonged freeze-thaw cycles. The pre-manufactured fiberglass jacket is comprised of glass fibers and corrosion resistant isopolyester resins. The resin completely encapsulates the reinforcing fiber network, which, for most applications, is conventional E-glass woven roving and bi-directional fabric. Each Snap Tite component is a single-seamed, cylindrical jacket that "snaps on" the column. The column is cleaned and prepared with a high performance urethane adhesive before the first jacket is applied. More jackets are applied until the desired thickness for the job is achieved. Adhesive is applied between layers, and the vertical and horizontal jacket seams are symmetrically alternated. A typical column will require 3 to 4 layers of jackets, with a nominal jacket thickness of around 1/8 inch thick. Each nested jacket is bound with belt clamps until the adhesive cures.

The Benefits

Snap Tite is recognized as one of the most cost effective and user friendly solutions for rehabilitating or upgrading existing steel reinforced concrete columns or structures. Snap Tite replaces steel, the conventional material used for column reinforcement, reducing installation and long-term maintenance costs. For example, Snap Tite, because of its light weight, can typically be installed in three hours vs. three days for steel, and can be lifted in place by workers using only a few pieces of light, mobile equipment. Snap Tite won't rust and never needs to be painted, even when installed in corrosive environments.

The other market challenge to Snap Tite is the epoxy resin composite column wrap. Although this composite does meet performance requirements, it is much more expensive to manufacture. The current manufacturer of this resin also uses extensive equipment for installation, Snap Tite does not.

Full-scale tests at two major universities have verified that columns reinforced with Snap Tite withstand three-to-eight times the deflection of columns without reinforcements. Preliminary tests indicate that Snap Tite can improve earthquake capability three times beyond that of a steel jacket.

Status

Snap Tite has been tested and approved by the California Department of Transportation to retrofit 3,480 steel reinforced columns on the Yolo Causeway in northern California. It was the natural choice for this project because the columns are submerged under water for several months each year. The technology is also being evaluated to rehabilitate other structures such as wooden utility poles, wooden pier pilings, and parking structures.

Composite Materials

Rapid In-situ Load Testing

Beams are installed at site

High performance adhesive bonding is applied to beam surface

The Need

Load tests and structural monitoring are used to gain information regarding the health and performance of an existing structure. Both are more representative than analytical approaches to evaluate the structure, especially when little is known about the structure's geometry and composition. For structures using relatively new materials, such as fiber reinforced polymer, the use of load tests can answer the question of structures' capability. Yet to justify the time and expense associated with full-scale load testing is difficult since it needs a long period of time over a large portion of the structures.

The Technology

Rapid in-situ load testing is intended to be much simpler and can be carried out in a fraction of the time and at a much lower cost. The testing procedure was originally developed at Center for Infrastructure Engineering Studies, University of Missouri-Rolla to offer a non-destructive yet conclusive demonstration of the performance of new construction techniques and technologies.

The key concept of this technique is the identification of the structural component and its response. The load test involves applying loads to the structural component through the use of hydraulic jacks. To gain critical responses in the structure without doing any permanent damage, the location and magnitude of loads are carefully designed. Deflections and strains induced are measured, and the structure's performance is evaluated based on the linearity of its response to loading.

This rapid in-situ load test system is easily shipped to a site; the equipment contains two gang boxes. The boxes include hydraulic jacks and a remotely controlled hydraulic pump for applying loads; several instruments for measuring deflections, strains, elongations, and slopes; and a digital data acquisition system that records data to a portable computer.

The Benefits

This rapid load test system can be a powerful tool for the assessment of new construction technologies and for evaluation of structure when little is known about the structure's geometry and composition. The system also provides the information of structure with less risk of damage to the entire structure.

The system's approach allows a much simpler evaluation of structures and can be carried out in a fraction of the time and at a much lower cost. The installation of the system may take 3 to 4 hours depending on the applications. The actual test takes less than one hour.

Status

Currently the rapid in-situ load test system has been implemented to evaluate seven different structures with bonded carbon fiber reinforcement. This system is being considered as way of testing fiber reinforced concrete, concrete structures reinforced with carbon fiber rods, and pultruded glass fiber reinforced plastic bridge sections.

Composite Materials

Carbon Fiber Reinforced Polymer (CFRP) Laminates for Structural Strengthening

Carbon 3-D Fabric, developed by Kajima (above), was used in the curtain-wall panels of the Sea Fort Square building in Japan's demanding coastal environment.

The Need

Strengthening measures are required in structures when they are required to accommodate increased loads. Also, when there are changes in the use of structures, individual supports and walls may need to be removed. This leads to a redistribution of forces and the need for local reinforcement. In addition, structural strengthening may become necessary owing to wear and deterioration arising from normal usage or environmental factors.

Concrete structures need to be strengthened for any of the following reasons:

Load increases due to higher live loads, increased wheel loads, installations of heavy machinery, or vibrations.
Damage to structural parts due to aging of construction materials or fire damage, corrosion of the steel reinforcement, and/or impact of vehicles.
Improvements in suitability for use due to limitation of deflections, reduction of stress in steel reinforcement and/or reduction of crack widths.
Modification of structural system due to the elimination of walls/columns and/or openings cut through slabs.
Errors in planning or construction due to insufficient design dimensions and/or insufficient reinforcing steel.

The Technology

The pultruded CFRP laminate reinforcing consists of bonding the CFRP strip with the concrete structure using a high-strength epoxy resin as the adhesive. The CFRP strips are manufactured using a pultrusion process. The pultrusion principle is comparable with a continuous press. Normally 24,000 parallel filaments are pulled through the impregnated bath, formed into strips under heat, and hardened. These strips are uni-directional; the fibers are oriented only in the longitudinal direction. Correspondingly, the strip strength in this direction is proportional to the fiber strength and, thus, very high. Strips are produced with strengths of approximately 3,000 MPa in the longitudinal direction, and with a thickness of up to 1.5 mm and widths of up to 150 mm.

In order to achieve an optimum composite action, the preparation of the bonding surfaces of the strip and concrete is critical. The strips must have the outermost layer of their bonding face, normally matrix-rich, removed to expose the fibers. Just before the bonding, the bonding surface is carefully cleaned with acetone. The concrete surface is treated by sand blasting, high pressure water jets, stoking, or grinding. Shortly before the bonding, it is cleaned with a vacuum cleaner. Concrete must be at least 6 weeks old, and have a minimum tensile strength of 1.5 MPa. Highly filled epoxy resin adhesive is used for the bonding.

The Benefits

CFRP laminate reinforcing technology provides a solution for strengthening problems of concrete structures. It provides great strength, high modulus of elasticity, and outstanding fatigue resistance It is a very lightweight non-corrosive material, that requires minimal preparation of laminates, and it's alkali resistant. It is an economic method that requires very short contract times.

Status

Based on the worldwide research and development work, the use of CFRP strips to rehabilitate structures is already routine for many firms in Western Europe and Japan. In the U.S., Sika has introduced Sika CarboDur, which is a CFRP laminate used to strengthen concrete, steel, or wooden structures. CFRP materials will not replace traditional construction materials, but will be used increasingly to supplement them as needed.

A research team led by Dr. Abdul-Hamid Zureick, Professor of Civil and Environmental Engineering at Georgia Institute of Technology, Atlanta, GA, has performed an integrated field/laboratory approach to rehabilitate the Lee Road Bridge over Interstate 20 in Douglas County, GA, using CFRP. This project is funded by the Georgia Department of Transportation (GDOT) in cooperation with the Federal Highway Administration (FHWA). The project took workers less than a day to complete what could have taken several weeks to do traditionally and, so far, laboratory tests have determined that CFRP can make bridges 30 to 40 percent stronger than the original design.

Barriers

Although this technology has been used successfully in Japan and Europe, the usage of composite materials like CFRP is still not widely recognized in the industry. The lack of knowledge of the technology and the simplicity of it will make some people hesitant to use it.