Header image
 
Self-Repairing Matricies  
 
 
 
Download this article as a PDF.
 
Development of a Self-Repairing Durable Concrete
 
Dr. Carolyn Dry
Natural Process Design, Inc.
 
Abstract

The usual approaches for repair of structural concrete are: polymer injection, prestressing, geomembranes, and polymer wraps.[1-7] These techniques seek a ductile, less brittle failure. All of them are based on addition of a repair material to concrete from the outside in; we add the materials from inside the concrete to repair.


Our approach consists of embedding repair material in hollow fibers in the repair matrix, before it is subjected to damage. Therefore, when cracking occurs, this repair material is released from inside the fibers and enters the matrix, where it penetrates into cracks and rebonds to the mother material of the structure being repaired. The cracking and damage, associated with the low tensile strain capacity, triggers the release of the repair material. This is important because in this way, the material acts in an extensible manner. Further, it does crack and show ductile behavior, but the instant repair of cracks and damage assures that deterioration does not accompany this “crack then repair” behavior. Thus, we repair the problem, where it occurs, and just in time, automatically, without manual intervention.


“Long-term durability is achieved by dimensional stability, which means less stress from thermal contraction, autogenous shrinkage, and drying shrinkage. The combination of factors affecting crack resistance is called "tensile strain capacity" or "extensibility". Cracking of concrete can be managed by controlling the extensibility of the material. Cement-based materials with large extensibility can be subjected to large deformations without cracking.”[8] Thus, the technique we utilize does precisely that: it adds more material to the concrete matrix from the inside upon demand when it is triggered by events such as cracking of the matrix or shrinkage. Moreover, it does not sacrifice strength for durability since the fibers and released repair adhesive add to the overall strength.


Various techniques have been proposed for repair, however all of them have been only partial and temporary solutions. Concrete is a brittle material. Also, concrete structures are dimensionally unstable because of movement. Consequently, the usual repairs do not hold. The technique we have developed, self-repair, unites the most crucial qualities necessary for a successful repair system: crack resistance and long-term durability. This approach addresses the bonding problem of repair material from inside the concrete, therefore, it is definitely a better technique compared to other methods, such as the polymer injection method. Furthermore, compared to the use of compressible beads in polymer injection into brittle cracks, to impart flexibility, it is seen that self-repair performs better because the adhesive is flexible itself and keeps on releasing with each brittle failure, i.e. crack. The ability to fill in for dimensional gaps has been shown to work with self-repairing adhesives that grow larger in volume. Even with internally released stiff adhesives, self-repaired matrices are less brittle, more ductile, and yet stronger in tension than controls without adhesives.


The question of whether we could replace the tensile strength given by steel rebar was explored. The research results showed that in the first loading, concrete samples with adhesives and a small amount of metal that provides additional tensile strength were stronger in tension than control samples reinforced with more metal wires, metal mesh or even rebars.


In self-repair of cracks, different types of structural failure require different approaches. For instance, in full scale bridge applications, we addressed surface drying cracks by creating in-situ control joints. We placed scored brittle fibers, which broke at the centerline upon matrix shrinkage, releasing a sealant/adhesive. Furthermore, we repaired shear cracks by chemicals released from fibers buried in the depth of the bridges. We observed that when these broke, the entire bridge performed better than the control one without the embedded adhesive filled fibers. Our approach provided a self-repairing technique that transformed the entire structure into a ductile material, where energy was dissipated all over as cracks formed, and consequently, catastrophic failure, due to the enlargement of any one crack, was prevented.


Furthermore, we made frames to represent bridges and structures subjected to dynamic loads. We demonstrated that, as a result of self-repair with different types and locations of adhesives, there was less permanent deflection, more stiffness in specific locations, where desired (by adding stiff adhesives) or more damping by adding damping chemicals.


Our approach consists of embedding repair material in hollow fibers in the repair cement matrix, before it is subjected to damage. Therefore, when cracking occurs, this repair material is released from inside the fibers and enters the matrix, where it penetrates into cracks and rebonds to the mother material of the structure being repaired.


Further, we have addressed the corrosion problem, by the release of anticorrosion chemicals from hollow porous walled fibers, which are coated with a chemical that dissolves in saltwater. The encapsulated chemical is released onto the metal rebar when the coating is dissolved by the saltwater.

 
The Problem: Damage
in Concrete, Repair Efficacy and Cost

Concrete is inexpensive relative to other construction materials, however, damage can greatly reduce its life cycle. Internal damage is common in concrete. Repair of this type of damage is crucial in preventing failures that can progress to ultimate catastrophic failures. However, it is hard to detect micro scale cracks unless they have developed to macroscopic scale flaws. Non-destructive evaluation techniques have limited ability to detect these microcracks. Also, the damage repaired in the field by hand does not restore the original strength of the material.


Concrete materials have applications in rehabilitation of existing bridges. They are either used for complete structural replacement or new construction [9]. The American Association of State Highway and Transportation Officials (AASHTO) projected that just to maintain current bridge conditions, 200,000 bridges will need to be replaced or repaired during the next two decades [10]. The main problem is quality assurance.


Deterioration of concrete structures is another challenge that we are faced with. The problems in concrete for civil structures are: (1) repair and survival of damage, (2) reliability, comprising over time repairability, durability and health assurance, and (3) first cost, but especially, life cycle costs of repair or replacement. We have focused on improvement of reliability due to damage, durability and design of low cost concrete repair systems for structural use, which have low life-cycle costs, and lower first costs. Various repair chemicals were used which could:

  1. repair different types of damage,
  2. fill different sizes of damage,
  3. repair damage caused by different forces and speed.
 
This research produced a new family of self-healing concrete repair materials, which will solve the problems mentioned above and relieve the fears of some planners. Self-healing solves the quality assurance problem and reduces life cycle costs. The extended life reduces the number of replacements, and thus the future costs. This new family of self-repairing materials is less expensive overall because the repair material is built in and available, wherever and whenever it is needed. Therefore, over-designing for damage protection is eliminated. The life cycle cost (which is usually much more than first costs of construction) will yield the most dramatic savings.
 
The Solution: Self-Repair:
The Answer to Damage in Concrete

“In concrete and other cement-based materials, microcracks already exist at the interfaces of the aggregate-mortar and reinforcement-mortar. When large, visible cracks become interconnected with microcracks, the network of cracks facilitates the transport of aggressive ions and gasses to the embedded reinforcement, leading to premature corrosion and deterioration”[8]. This research addressed the repair of micro damage by the release of chemicals from fibers into matrix microcracks, so that development of further damage can be prevented. The repair fibers also releases chemicals between delaminating layers or re-bonded fibers to the matrix. Two different repair mechanisms for self-repair have been investigated, release from brittle fibers and release from brittle coating over porous walled fibers. Experiments assessed the ability to both re-bond fibers and repair cracks using fiber pull-out tests, impact, and bending tests with successful results.


We investigated the repair of damage, in particular, microcracking, fiber debonding, matrix delamination, fiber breakage, impact damage such as holes, and adhesive debonds and their healing by the release of chemical healing agents from fibers into the matrix. All of the above damage types are affected by interfaces. Reduction of damage in the matrix is done by release of repair chemicals from fibers directly into the interfaces.


In order to be self-repairing, a healing chemical is stored in hollow fiber vessels embedded in the polymer matrix. When the composite is damaged, the crack progresses, breaking the repair fiber, see figure 1. The healing chemical flows into the crack and re-bonds the cracked faces see figure 2. Alternatively, the fiber can also be re-bonded to the matrix and/or to delaminations and holes repaired with the adhesive.

 

Figure 1. Schematic representation of the
self-repair mechanism [11].

Figure 2. A photo, taken under a microscope, of a coated glass pipette releasing it’s repair chemical into the matrix, under tensile stress [11].
 
Design of the Self-Repairing System

We made self-healing repair material consisting of embedded continuous hollow fibers, which contained water proof adhesives that filled cracks, when and where they occur. Continuous fibers with a high aspect ratio give the best composite properties in stiffness and strength [12]. Further, as the volume of fibers increase, the stiffness and strength of the structural system increases [12]. Up to 80% volume fraction of fibers is acceptable, if the fibers can be incorporated into the matrix [12]. To resist corrosion, porous walled fibers coated by a coating that dissolves in salt water, were used which contained anti-corrosion chemical. When the coating dissolved, the chemical was released onto the metal rebar.


In general, materials capable of passive, smart self-repair consist of several parts: (1) an agent of internal deterioration, such as dynamic loading, which induces cracking, (2) a stimulus to release the repairing chemical, (3) a fiber or bead, (4) a coating or fiber wall which can be removed or changed in response to the stimulus, (5) a chemical carried inside the fiber, and (6) a method of hardening the chemical in the matrix or a method of drying the matrix [13].


Further, these systems, capable of passive, smart self-repair, must have the following requirements:

  1. materials should not degrade the matrix properties,
  2. materials must contain enough chemical to repair the damage,
  3. the encapsulator must break in to respond to damage,
  4. the chemical must flow out of the encapsulator,
  5. enough chemical must be released to be able to reach the cracks (in a two part or cross-linking system the released chemical must find the second one),
  6. crack damage must be repaired,
  7. repair must be rapid,
  8. overall catastrophic failure prevented,
  9. overall strength must be restored to 80-100% and above,
  10. in testing, new cracks form before repaired cracks reopen,
  11. additional chemical must be able to be supplied,
  12. damage and subsequent repair must be assessed.
 

Also, the chemicals chosen must withstand ambient heat extremes, have a long shelf life, be of reasonable cost, not environmentally hazardous or have noxious odor.


Several optional unique features have been developed as appropriate for repair materials for concrete in special applications subjected to damage. These features comprise the following:

  1. To address the issue of speed of release, pressure release was developed, in which the repair chemical was kept under moderate pressure, and very rapidly pushed the repair chemical into the crack area. Figure 3 is a photo of proof of concept of pressure release.
  2. Additional repair chemical may be needed to be embedded over time for later self-repair. This can be done with fibers that are exposed at the composite edge. Figure 4 is a photo of the successful vacuum replenishment of repair chemical into the fibers.
  3. Fibers can be interrogated to reveal any cracks in them, but also in the matrix. Fibers that extend to the edge are available for this opportunity. Figure 4 is a photo of this concept in practice. Loss of repair chemical can also indicate the crack volume and where these cracks existed.
  4. Two part epoxies can be the chemicals released without pressure. Dual fibers have been designed to assure proper proportionate release.
 
Figure 3. Demonstration of the pressure release concept. Adhesive in the fiber and a balloon is under pressure. When the specimen cracks, the pressure differential causes the adhesive to flow rapidly into the crack site.
Figure 4. Demonstration of the vacuum concept, filling of embedded repair fibers.  
 

Self-healing/repair or autogenous healing is a concept that Dr. Carolyn Dry, invented. All of the basic patents covering the approach are covered in this intellectual property. There are seven patents issued to Dr. Dry. All embodiments go back to 1990.


This approach, as described in one of the broader patent claims, is “A shaped article comprising: a shaped matrix material having at least one release vessel disposed therein, said release vessel having a releasable modifying agent contained therein and maintaining the modifying agent within the release vessel until released and releasing the modifying agent from the release vessel in the matrix material in response to at least one external stimulus.” [14].

 
Research on Self-Healing Composites Which Are TransparFriday, June 20, 2008

An investigation was made into the development of transparent polymer matrix composites that have the ability to self-repair internal cracks due to mechanical loading. The research focused on the cracking of hollow repair fibers dispersed in a matrix and the subsequent release of repair chemicals in order to visually assess the repair and speed of repair. [15]


Impact tests on polymer specimens revealed repair in less than ten seconds. As seen in figure 5, an Epon epoxy impact sample containing two-part epoxy in small tubes was subjected to impact in a Dynatup machine. The results were dramatic. Within seconds the two part adhesives had filled all contiguous cracks, even though no fibers had been directly hit, the adhesives raced around, and filled the circular crack, an artifact of testing caused by the edge of the impact machine. Adhesive flow, set up and repair was accomplished within less than ten seconds.

 

Figure 5. Photo of a 3 inch diameter impact epoxy matrix sample with double lumen fibers, containing two part epoxy resin, dyed red and black. [11]

 
Research on Self-Repair of Cracks in Concrete
We worked on “butterstick” samples that were 1”x1”x6” in size. We placed 24 small metal reinforcing fibers and 150 ml breakable tubes, which were filled with adhesive, in each of these samples. The control samples did not contain any tubes, but they were reinforced with 24 small metal reinforcements, just like all of the other samples. After tests, we found that in members subjected to bending, the failure mode was more brittle in the first break, and more ductile in the second break, especially when compared to the control ones, see figure 6 left two. Pullout tests also revealed that the fibers were re-bonded to the matrix, after the tubes were broken and the internal adhesive was released. It was again observed that the failure was more ductile after the release of the adhesive, see figure 6, right one.
 

Figure 6. Example of strength increase and more ductile failure due to repair chemical in small concrete test beams, left [16]. Right, the repair fibers were subjected to pull out testing and found to be re-bonded after release of the adhesive into the matrix. The pullout tests show a more ductile release with the fibers that had been adhesively re-bonded than the controls [16].

 
Figure 7. A photo of a beam repaired by intumescent repair adhesive.  
Figure 8. Testing results comparing four reinforcing systems under bending in standard mix concrete composite matrices [10].
 
 

In further tests, the ability of adhesives to fill in for dimensional gaps has been discovered. The self-repairing adhesive that increased in volume were the most successful one, see figure 7. This result was very important because it showed that although concrete was a non-extensible material, it could behave in an extensible way, should the right choice of repairing technique, self-repair, was pursued, and adhesive types were utilized.


Also, four reinforcing systems under bending in standard mix concrete composite matrices were investigated, see figure 8. The question of whether we could replace the tensile strength given by steel rebar was explored. The research results showed that in the first loading, concrete samples with adhesives and a small amount of metal that provided additional tensile strength were stronger in tension than control samples reinforced with rebar, metal wires or metal mesh, see figure 9.

 

 Description

 Test # 1

(kN)

 Test # 2

(kN)

 Change (% ) in load at 2.5 mm. deflection

Wire Only

  22.0, 10.5

16.0, 0.0

-27, -100

Reinforcing Bar #4

12.5, 8.5

8.0, 0.5

-36, -100

Steel Fiber Mat

5.5, 11.0

16.0, 0.0

-97, -100

Wire & Adhesive

19.0, 9.0

  19.5, 1.4

-3, -84

Figure 9. Testing results comparing four reinforcing systems under bending in standard mix concrete composite matrices [17].
 
Finally, we compared our results of internal self-repair, in which we addressed the bonding problem from inside the concrete, to the polymer injection method, which was done from outside to inside. It was shown that the self-repair technique that we utilized, repaired better, when it was compared to the polymer injection method, see figure 10 [18]. Furthermore, compared to the use of compressible beads in polymer injection and regular polymer injection into brittle cracks, in which there is a need for flexibility, self-repair was again better in repairing because the adhesive itself is flexible, and kept on being released with each brittle failure i.e., crack.
 

Sample Type

Modulus of

Elasticity

Cracking Load Increment (%)Average Values

Results or polymer injection from outside to inside

High

56*, 65*, 83, 102

Low

103

Results of internal self-repair from inside to outside

High

121, 123

Low

88, 119, 132

Figure 10. Comparison of internal self-repair and outside resin injection specimens in terms of ability to carry a load before cracking, * indicates that ribbed bars were used [18].
 
Self-Repairing Concrete Frames
Which Represent Buildings and Bridges
The self-healing method investigated for this project utilized the timed release of adhesive into the member at the time of cracking. We constructed concrete frames that simulated buildings and bridges. Chemically inert tubing was cast within the cross section of the member and then was filled with adhesive, see figure 11. At the onset of cracking, the tube wall was fractured, allowing adhesive to exit the tubing and penetrate the developing crack. Two sets of static loading were applied, in which failure modes were checked for each sample to determine either the frame failed at crack sites sealed by the flexible adhesives, or crack sites sealed by adhesive. Then the frames were subjected to cyclic loading (repetitive static loading, not dynamic), immediately after the third test in order to examine whether or not each experimental adhesive was able to exhibit elastic or inelastic behavior in the frame [19].

 

Figure 11. Design of test frames with tubes containing adhesives at joints and element midspan. [19]

 

It was seen that in self-repairing frames, high modulus of elasticity adhesives (stiff adhesives), released at the structural points, repaired the initial damage in critical regions. These stiff adhesives allowed damaged points to regain stiffness, preventing future damage at the joints, while transferring forces to other portions of the structure, preventing catastrophic failure, see figure 12. However, the control frames with no internal adhesive were catastrophically damaged, see figure 13.


The self-repairing frames deflected more than the control ones, while resisting larger loads, see figure 14. The self-repairing frames had fewer reopened old cracks than controls, and the self-repairing frames with stiff adhesives were stiffer than the controls, the ones without adhesives, see figure 15. Furthermore, testing on the hysteresis effects showed that the frames with repair chemical, see figure 16, on the right, more nearly returned to their original configuration that those without repair chemicals, on the left.

 
Figure 12. Photo of frame containing internal self-repairing adhesives, cracking in the third static test, which shows cracking all over, but no catastrophic failure [19].
 
Figure 13 Photo of control frame with no internal self-repairing adhesives, which shows catastrophic failure after testing [19].
 

Bending tests at 3mm.

Bending tests at 0.6 kN.

Sample

Increase (%)

Sample

Increase (%)

Control

-52.38

Control

20.00

101 b

-45.45

101 b

71.43

101 c

-9.09

101 c

29.03

101 d

16.67

Figure 14. Results indicating that the self-repairing frames can carry more load and deflect more than the control ones [19].
 

Sample Type

Avg. change (%) in stiffness form test 1 to 2 (kN/mm)

Ratio

(new/reopened cracks)

Control

97.6

0.55

129

1.80

Repair chemical 1, stiff

104

0.80

112

2.50

Repair chemical 2, flexible

97.8

0.22

109

0.14

Repair chemical 3, flexible

141

0.22

Figure 15. Chart showing the stiffness of frames which released various types of adhesives, the self-repairing frames had fewer reopened old cracks than controls [19].
 

Figure 16. Hysteresis results of test on self-repairing frames on the right, versus frames without repair chemical on the left [19].

 
Thus, we successfully demonstrated the control of structural damage by strategic release of appropriate internal repair adhesives in critical locations of the frame. There was less permanent deflection and more stiffness in locations where stiff adhesives were used and more damping where damping chemicals were added to the matrix. It was proved that structural damage, namely cracking, can be directed to the members themselves, where cracks can be repaired by flexible adhesives which allow some flexibility in the members for energy dissipation, necessary for resisting dynamic loading failure and recovery from deformation. The most interesting result of these experiments was the visual assessment in transparent frames that the adhesive was being pumped further with each crack opening and closing due to reloading, see figure 17.
 

Figure 17. Test frames containing fibers filled with adhesive. Not only do such frames repair cracks all over the matrix, but also it was observed that crack opening and closing (caused by load application and removal) drove the adhesive deeper into the matrix with each action, like a bellows.

 
Self-Repair of Cracks in Full-Scale
Concrete Bridge Decks
Different types of cracking require different approaches. This research, sponsored by NCHRP of the Transportation Research Board and Natural Process Design, and done at the University of Illinois, focused on the repairing of drying shrinkage cracks and on repair of structural load-induced cracks in four full-scale bridge decks. Dr. Dry was the principal investigator on this project. Fibers were thrown into the cement mixer to prove that they could survive the mixing intact, see figure 18.
 

Figure 18. Fibers being thrown into the cement mixer at the site, on the left, and they survive after mixing in the bridge concrete, on the right.

 

In these large bridges, interior shear cracks were repaired by chemicals released from fibers buried in the depth of the bridges [21]. Long capsules containing strong, high modulus adhesives were placed below the surface in areas of tension caused by bending, for example the top of the section over the supports, see figure 20. When these broke, the entire bridge performed better than the control one without embedded adhesive filled fibers. Figure 21 shows the release of an adhesive after testing. Structural cracks, induced by loading, were successfully repaired. This was evidenced by the higher strength of the bridge decks that contained adhesives, when compared to the control deck. Also, we observed that new cracks formed in certain locations, and consequently, this prevented reopening of any of the previously repaired cracks [21].


The most impressive evidence of the structural crack repair capabilities of this system are the diverted cracks in the second loadings of decks #2 and #4 that contained adhesives. In both cases, original cracks from the first loading were repaired so successfully that secondary cracks opened and only later did the original cracks reopen with the applications of additional load. The control deck without adhesive had no such occurrence. Compared to the second and third loadings of the control deck, deck #1, which contained no repair adhesives, decks #2, #3, and #4 all showed signs of bending strength re-gain in their later tests.


In all of the decks containing repair adhesives, subsequent loadings revealed additional adhesive release all along the reopened cracks. These adhesives survived for over 3 years in field conditions ranging from below freezing to over 100ºF in central Illinois [21].

 
 
 
 
 
Figure 19. Photo of fabrication of bridge decks
Figure 20. Photo of released repair adhesive [21].
 
 

Regarding these results, it is seen that our approach provided a self-repairing technique that transformed the entire structure into a ductile material, where energy was dissipated all over as cracks formed, and consequently, catastrophic failure, due to the enlargement of any crack, was prevented. Cracks were repaired as they formed, so that further crack damage in those locations, intrusion of water or chemicals were prevented at that site


Testing revealed that internal release of adhesives in the three tests increased the modulus of elasticity, the stiffness, and reduced the strain of the three decks, as compared to the control deck, see figure 21

 

Figure 21. Chart indicating the changes in modulus of elasticity, stiffness and strain of the four decks, that were tested three times. Deck # 1 is the control.

 
Research on Prevention and Delay of Corrosion

“Deterioration and distress of repaired concrete structures in service are a result of a combination of physical and chemical processes, such as the corrosion of embedded reinforcing steel, alkali-aggregate reaction, delayed ettrringite formation, etc. These processes are accelerated by the cracking of the repair materials, thus allowing the ingress corrosive elements such as water, salts, carbon dioxide, sulfates and oxygen, into the concrete”[8].


The time of corrosion onset and severity can be improved by the release of anticorrosion chemicals from hollow porous fibers. These fibers are coated with a chemical which dissolves in saltwater. The encapsulated anti-corrosion chemical is released onto the metal rebar when the salt water dissolves the coating. We have demonstrated this method in the laboratory using ASTM tests for corrosion. The release of the corrosion inhibitor chemical is at the portion of the reinforcing bar in danger of corrosion when conditions would allow corrosion to initiate. In a series of tests with concrete samples containing either no protection or the conventional freely mixed calcium nitrite, this system of internal release from fibers performed well. It delayed the onset of corrosion by at least three weeks, in the laboratory specimens, and reduced the amount of total corrosion by more than half. Figure 22 shows the data before conversion to times and severity in real time and space, and figure 23 shows the visual inspection and assessment of the corrosion samples [22].

 

Figure 22. Comparison of onset and severity of corrosion, for fibers containing anticorrosion chemical, on the right, versus those without, on the left [22].

 

Figure 23. Corrosion samples broken for visual inspection, left, the assessment of them on right[22].

 
Factors Involved in Parameter Selection
for Any Particular Application
To look at an optimum design, the following technical questions need to be addressed:
  • Does the concrete repair work?
  • What are the best repair chemicals, encapsulators and system to be used in the type and use of concrete?
  • What type of fiber and release mechanism works the best to release and to introduce the repair chemicals into the repair material for various types of damage?
  • Does the repair systems cause any unforeseen detriment to the mechanical properties?
  • What strength does the repaired product have?
  • Does the self-healing repair matrix, repair damage and restore lost strength?
  • Does the self-repair prevent water and chemical and gas intrusion and debonding?
  • Is the use of the self-healing system justified by the improvement in life cycle costs?
 
To refine the theoretical basis of the parameters needed for fabrication of self-healing components there must be a capacity for self-repair by internal just in time release of chemicals. The parameters to refine are matrix choice, fiber chemistry and ability to bond with the matrix, fiber volume, internal diameter, wall thickness, stiffness, brittleness and its change over the process of formation of the composite, insertion onto and into an array and a prepreg, trigger rate, viscosity and flow rate of release chemical, total time to repair, ability of chemical to repair damage types, restore strength of the composite and resist environmental degradation due to temperature change.
 
References
  1. Brady, Pamalee A.; Marshall, Orange S.,“  Shear Strengthening of Reinforced Concrete Beams Using Fiber-Reinforced Polymer Wraps”  Construction  Eng. Lab., Army, Champaign, Il., Feb., 1999
  2. Alexander, Michel; et. al., “Technologies for Improving the Evaluation and Repair of Concrete Bridge Decks: Ultrasonic Pulse Echo and Polymer Injection” Army WES, Vicksburg, Ms., Oct.., 14, 1998
  3. Anderton, Gary L.; Ahlrich, Randy C., “Design, Construction and Performance of Resin Modified Pavement at Fort Campbell Army Airfield, Kentucky”, Army WES, Vicksburg, Ms. , March 1994
  4. Muszynski, L. C. , “Durability of Expedient Repair Materials”, Applied Research Associates, Inc., Panama City, Fl., March 19933
  5. Vaysburd, Alexander M “Performance Criteria for Concrete Repair Materials, Phase II Laboratory Results”, Structural Preservation Systems, Inc., Baltimore, Md., June 3, 1998
  6. Miles, William R., “Comparison of Cast-in-Place Concrete Stay-in-Place Forming Systems for Lock Wall Rehabilitation”, Donald Bergman Associates, Rochester, N.Y., Oct.1993
  7. Pace, Carl E., “The Structural and Durability Properties of Various Concrete Repairs” Army Engineer Waterways Experiment Station, Vicksburg, Ms., Sept. 1979
  8. Navy SBIR 03-35
  9. The American Association of State Highway and Transportation Officials (AASHTO) web site
  10. A. Nanni, “Concrete Repair with Externally Bonded FRP Reinforcement: Examples from Japan,’’ Concrete International: Design and Construction, Vol. 17, pp. 22-25, 1995
  11. Dry, C. M., and N. Sottos, “Passive Smart Self-Repair in Polymer Matrix Composite Materials,” Proceedings Conference on Smart Structures/ Materials, Vol. 1588, SPIE 2/1/93
  12. Adanur, Sabit, Wellington Sears Handbook of Industrial Textiles, Technomic Publishing Company, Lancaster, Pa., 1995,
  13. Dry, C. M., "Passive Smart Materials for Sensing and Actuation."  Proceedings:  Conference on Recent  Advances in Adaptive and Sensory Materials and Their Applications, edited by C. A Rogers and R. C. Rogers, VPI &SU, Blacksburg, Virginia, April 27-29, 1992, Lancaster, England, pp. 207-223
  14. Dry, Carolyn M., Self-Repairing, Reinforced Matrix Materials, U.S. Patent # U.S. 6,261,360,B1
  15. Dry, C. M. Procedures developed for self repair of polymer matrix composite materials In Composite Structures, 35 (1996) 263-269 Elsevier, London
  16. Dry, C. M., "Timed Release of Chemicals into Cementitious Material after the Material has Hardened to Repair Cracks, Rebond Fibers, and Increase Flexural Toughening,” Fracture Mechanics: 25th Volume, ASTM STP 1220, F. Erdogan, Ed., A.S>T.M., Philadelphia, Pa., 1994.
  17. Dry C.M., A Comparison Between Adhesive and Steel Reinforced Concrete in Bending," Journal of Cement and Concrete,1998
  18. Dry, C.M., Melinda Corsaw, Ertan Bayer,“A Comparison of Internal Self-Repair with Resin Injection in Repair of Concrete”, Journal of Adhesion Science, 2002
  19. Dry, C.M., "Smart Bridge and Building Materials in Which Cyclic Motion is Controlled by Internally Released Adhesives,"  SPIE's Smart Structures/Materials Conf., San Diego, CA, February 1996
  20. Dry, C.M., "Repair and Prevention of Damage Due to Transverse Shrinkage Cracks in Bridge ," SPIE Conference on Smart Bridges Structures, Highways, Newport Beach, Ca., March 1 5, 1999
  21. Dry, C.M.,  "Repair of Highway Bridges by Internal Time-Release of Repair Chemicals," Proceedings of Engineering Mechanics:  A Force for the 21st Century, La Jolla, California, May 17-20, 1998
  22. Dry, C.M., and Melinda Corsaw "A Time Release Technique for Corrosion Prevention," Journal of Cement and Concrete, July1999
  23. Dry, C. M., "Adhesive Liquid Core Optical Fibers for Crack Detection and Repairs in Polymer and Concrete Matrices," in Smart Structures and Materials 1995:  Smart Sensing, Processing and Instrumentation, Proceedings SPIE 2444, W. B. Spillman, Jr., Editor, 1995, pp. 410-413
  24. Dry, C.M. and William  McMillan, "Three Part Methylmethacrylate Adhesion System as an Internal Delivery System for Smart Responsive Concretes," Smart Materials and Structures, 1996, pp. 297-300
Last Updated:  Friday, June 20, 2008
All Material Copyright 2005 Carolyn Dry and Natural Process Design Inc.