REPORT

PROTOTYPE TESTING OF REPAIR TECHNIQUES

FOR REPAIR OF EARTHQUAKE DAMAGE

LOS ANGELES CITY HALL

EXTERIOR WALLS

UNDER

CONTRACT DACW09-72-0067

PREPARED FOR

LOS ANGELES DISTRICT CORPS OF ENGINEERS

PREPARED BY

VTN ORANGE COUNTY

2301 CAMPUS DRIVE

IRVINE, CALIFORNIA 92664

12 MAY 1972

INDEX

SECTION PAGE

1.0 INTRODUCTION 3

2.0 GENERAL 5

2.1 Purpose 5

2.2 Definitions 5

2.3 Existing Wall Condition 7

3.0 CONCLUSIONS 8

4.0 RECOMMENDATIONS 9

5.0 COMMENTS 10

APPENDIX “A” CONTRACT SCOPE OF WORK 11

Annex “A” 11

Figures 1 through 9 See Link

APPENDIX “B” ORIGINAL DEFINITIVE SCOPE OF

WORK AND REQUIREMENTS 12

1.0 VTN ORANGE COUNTY’S SCOPE OF WORK 12

2.0 SERVICES TO BE FURNISHED BY CITY 13

3.0 SAFETY 14

3.1 General 14

3.2 Specifications 14

4.0 SPECIAL REQUIREMENTS 14

5.0 TEST METHODS AND PROCEDURES 15

6.0 TEST PANEL PROCEDURES FOR

INJECTION SUBCONTRACTOR 16

6.1 Concrete Grout and Structural Adhesive 16

6.2 FR-3 Foam and Structural Adhesive 17

SECTION PAGE

APPENDIX “C” FIELD TEST PROGRAM 17

1.0 SCOPE OF WORK 17

2.0 MATERIALS 18

2.1 Non-Structural Foam 18

2.2 Structural Foam 18

2.3 FR-450 Foam 19

2.4 Structural Adhesive 19

2.5 Expansive Cement Grout 20

3.0 INJECTION PROCEDURE 20

3.1 FR-3 Foam and Structural Adhesive Injection 20

3.2 Expansive Cement Grout and Low Viscosity Structure

Adhesive Injection 24

3.3 FR-4 Foam Injection 28

3.4 FR-450 Foam Injection 30

4.0 AUTOMATIC PLACEMENT EQUIPMENT OF FOAM

ADHESIVES 30

4.1 Handling Problems of Foam Adhesives 31

4.2 Structural Adhesive Injection Equipment 32

4.3 FR-3 Foam Injection Equipment 32

4.4 FR-450 Foam Injection Equipment 33

5.0 OCCUPANT DISTURBANCE 33

5.1 Odor 33

5.2 Noise 34

5.3 Work Areas 34

6.0 (NOT USED)

7.0 STRUCTURAL EVALUATION 35

7.1 Observations 35

7.2 Quality Assurance Recommendations 36

7.3 X-Ray Inspection 36

1.0 INTRODUCTION

The Los Angeles City Hall suffered considerable damage during the earthquake which occurred on February 9, 1971.

Under authorization of the Office of Emergency Preparedness, the Corps of Engineers awarded a contract for Field Investigation to VTN Orange County. This Contract was to investigate the manner and extent of damage to this building. Scope of work of investigation included the following:

(a) Taking of high resolution photographs of all the

exterior walls of the City Hall - the majority of

which was accomplished by use of a helicopter and

specially designed long-lens camera.

(b) Visual examination, correlation, and preparation

of tables of the extent of cracks and other damages

was accomplished through study of photographs

taken and checks against existing design drawings

of the structure.

cost of ceramic veneer units.

(d) Preparation of estimates for repairing cracks and

other damaged areas.

The field investigation effort associated with this Contract has been completed. A Contract was also awarded to VTN Orange County for the development of construction drawings and specifications for repair of the City Hall exterior walls. Work is progressing on this Contract.

During the course of the field investigation and development of the construction drawings for repair, it became apparent to the Corps of Engineers that insufficient knowledge existed as to the internal composition, internal damage of the walls, and extent of voids and cracks. In the Investigation Report, prepared by VTN Orange County, a recommendation was made that testing be done on certain materials which, during the investigation phase, showed the most promise of being suitable and acceptable in repairing the exterior walls.

The materials and process testing recommended were developed through conferences with manufacturers, applicators, building officials, and other contractors and engineers.

The materials to bond large cracks and voids which showed the most promise were “FR-3” foam, which is a two component, low unit strength adhesive produced by Delta Plastics Company, Santa Fe Springs, California, and “Expansive Cement Grout” produced by Pressure Grout Supply Company, Los Angeles, California. In addition to these materials, injections with epoxy structural adhesives to bond smaller cracks and voids would be required to complete the job of bonding the walls together.

Test locations were selected on the basis of being able to work on areas of the wall exhibiting light, moderate and severe damage. Further consideration was given to being able to work from roofs of the City Hall without the necessity of using expensive scaffolding. Negotiations were undertaken with applicators, with proven experience in handling the selected materials, to perform tests. A proposal was then submitted to the Corps of Engineers and a Contract subsequently awarded to VTN Orange County for the performance of the materials and process testing program to ascertain the extent of voids, composition of the filler material of the walls, and testing of epoxy compounds and grout material, as detailed more fully in Appendix “A”

This report concerns itself with the occurrences and developments during the accomplishment of the test program.

2.0 GENERAL

2.1 Purpose: The prime purpose of this program was to evaluate repair materials and techniques. The second objective was to determine the internal wall construction, percentage and extent of voids. Walls are nonstructural multi-layer construction of ceramic veneer on the exterior and brick on the inside with the area between filled with rubble cemented together with lime mortar in a haphazard manner.

The material quantity and procedural problems were worked out by utilizing a systematic approach of repair and core drill, with the information gained from the cores taken being used as a guide in the modificaion of material quantity and placement method to be used in work on the next test panel.

As a result of the efforts expended on the field testing of materials and processes, VTN would be better able to develop the Construction Specifications for the repair of the exterior surfaces.

2.2 Definitions:

2.2.1 Automatic Injection: See “In-Line System.”

2.2.2 Batch mix: This is a process of adhesive or foam mixing where the material is mixed in small quantities.

2.2.3 Ceramic Veneer: The exterior layer of the wall is made of this material. These are hand cast, glazed tiles produced by the Gladding-McBean Company, now known as Interpace.

2.2.4 Core Drilling: The process of removing sections of the wall for analysis. This process utilizes a rotating cylindrical (6” diameter), diamond toothed, water cooled cutter which is anchored to the wall during the cutting process.

2.2.5 Crack-void Matrix: The network of interconnected cracks and voids which exist in the wall.

2.2.6 Discontinuous voids: These are voids which exist inside the wall and are not connected to the matrix of cracks and voids.

2.2.7 Dynamic Mixing Head: The mixing in this system is accomplished by a motor-driven mixing device such as that used in the injection head for FR-450 foam.

2.2.8 Epoxy: A family of organic chemicals frequently used as adhesives. These individual compounds have varying properties and must be carefully matched to job requirements.

2.2.9 Expansive Cement Grout: On this program, this is a material having the following formula: cement, water, Expando Group G.A. and Epoweld concrete bonder. The latter two products are produced by Pressure Grout Supply Company.

2.2.10 FR-3 Foam: A proprietary product produced by Delta Plastics Company. This material is a two component low-expansive pressure, non-objectionable odor, non-flammable, low unit strength, foam adhesive.

2.2.11 FR-4 and FR-450 Foams: Proprietary products produced by Delta Plastics Company. The FR-4 was the first material produced with FR-450 being a slight modification to provide a longer pot life. These materials are a two component low expansive pressure, non-objectionable odor, non-flammable, moderate unit strength, foam adhesive.

2.2.12 In Line System: This is a system which pumps, meters, and mixes two component materials in a continuous manner. The mixing may be accomplished using either a static or a dynamic mixing system.

2.2.13 Low Viscosity - “LV”: A two component structural adhesive in liquid form.

2.2.14 Machine Injection: See “In Line System”.

2.2.15 Manual Injection: This refers to the use of caulking guns for the injection of batch-mixed FR-3 or FR-4 foams.

2.2.16 Pot Life: The period of time between the start of mixing the two components and the start of the curing or expansion process. This time depends upon the formulation of the material and temperature.

2.2.17 Pot Mix: See “Batch Mix”.

2.2.18 Pressure Pot: A pressurized container used for injecting low viscosity structural adhesives. The batch mixed material is placed in the pot which is then pressurized forcing the premixed material into the wall.

2.2.19 Semi-Thixotropic: A two component structural adhesive in a thin paste consistency.

2.2.20 Static Mixing Head: The mixing in this system is accomplished by forcing the two components through a maze such as bottle brushes.

2.2.21 Structural Adhesive: A non-proprietary term for a material manufactured by a number of companies. This is normally a material in the epoxy family of chemicals available in many viscosities and having high unit strength.

2.2.22 Thixotropic: A two component structural adhesive in a paste consistency.

2.2.23 Void: A hollow area in the wall apparently resulting from the original construction, which may or may not be interconnected to other voids and cracks.

2.3 Existing Wall Condition: The wall is of a nonstructural multi-layer construction with the ceramic veneer on the exterior, a layer of brick on the inside, and the zone between filled with rubble, cemented together. This rubble filled zone was not completely filled during the initial construction of the building. The exterior walls of the building are nonstructural walls being supported at each floor.

The first real opportunity to examine in detail the interior wall construction was when injection port drilling began. At that time it was possible to observe the varying rate of drill penetration, due to sudden forward motion of the drill caused by voids in the wall interior. These voids were found to be as much as 10 inches in depth. The average thickness of the walls is 13 inches. In most cases, there was a void immediately behind the ceramic veneer.

In at least one occasion during inspection of the interior walls, the fireproofing brick around the structural steel columns of the building had been placed between the flanges without mortar and only the outside course of brick had mortar.

The bond of the existing mortar to brick is such that numerous cores failed at the bond plane during the process of core drilling. In these cases, the bond was tight enough to prevent penetration by the adhesives, but not strong enough to withstand the forces of core drilling.

Some cores have failed in the coring operation after injection when zones of fine rubble and mortar were encountered. The lime mortar does not have sufficient strength to sustain the coring forces. Failures of this nature occurred regardless of the repair method used. The mortar is sufficiently dense that unless injected under pressure for an extended period of time, adhesives will not penetrate deep enough to saturate mortar and give it strength. Cores taken from apparently undamaged wall sections in all cases came out in more than one piece. The bond between the ceramic veneer and the rest of the wall seems to be minimal in the areas tested. This condition verifies the hollow sound when the ceramic veneer on the exterior of the building was tapped. The areas adjacent to windows and under the window sills usually have very large voids, apparently not having been filled during original building construction..

3.0 Conclusions

All of the materials and procedures tested have some merit. All of the three methods tested as described in Appendix “B” appear to satisfy the structural requirements, and the exterior walls can be restored to a pre-disaster condition by the methods tested in this program. Data acquired indicated that the condition of the wall sections were similar. Voids which occur in the rubble

fill section of the wall are frequently not filled by grout or foam material. Insofar as can be determined, these voids have only a very small crack, if any, which connects them to the rest of the crack-void matrix, and thus, to the drilled injection port.

A constraining factor on the construction time required to complete the repair work is the availability of truly qualified and conscientious personnel experienced in handling epoxy and the specialized injection equipment. Access for men and equipment in and around the City Hall is a problem. Parking for Contractor vehicles is very limited and restrictive as to the size of vehicles that can gain access to the building.

When the cost factors are evaluated, however, the superiority of one method becomes apparent. FR-450 Foam was developed as the originally scheduled procedures and materials were being tested. Although the material cost of FR-450 Foam may be more than the other materials, the cost of injection and reduced labor estimated expended per 100 square feet of wall area indicated that this material should be utilized in filling voids in the exterior walls.

Injection of FR-450 foam is structurally acceptable as a method of bonding the existing walls. Comparison of treated samples and untreated samples together with lab testing has demonstrated that treated walls can be restored to a condition that is structurally at least as sound as the walls were prior to the earthquake of February 9, 1971. To insure required penetration of foam, automatic mixing and foam injection equipment should be used which is superior to manual injection.

Repair procedure should be restrictive to insure competitive bidding and prevent the contractors from short-cutting application methods and material quantities.

4.0 RECOMMENDATIONS

After completing the field effort involved with testing materials and processes, some recommendations for the performance of the complete task have evolved. These recommendations are as follows:

(a) The repair material should be an adhesive foam material such as FR-450, as produced by Delta Plastics and that the foam shall be in-line mixed.

(b) Due to the highly technical nature of the handling and injection of the FR-450 foam, and the specialized equipment required to effect the repairs contemplated, and because of the particular nature of this structure, a contractor’s work on other structures is not sufficient proof of his capability to effect an acceptable repair on this building.

(c) It is recommended that the invitations to bid be given to a selected list of contractors and those contractors be required to perform an acceptable test panel as a condition of bid submittal. If the test panel is unacceptable it shall be returned to an acceptable repaired condition by the Contractor.

(d) As an alternative, if open bidding is used, at the very minimum the apparent low bidder shall be required to provide an acceptable test panel prior to Contract award. If the test panel is unacceptable, the Contractor shall forfeit one-half of his bid bond, and another Contractor shall be selected.

(e) Exterior cracks in ceramic veneer should be sealed with a structural adhesive color matched to the buildings exterior prior to foam injection to bond the ceramic veneer, internal rubble and bricks interior together.

(f) The interior plaster on interior brick portions of exterior walls should be removed only when necessary.

(g) None of the damaged areas of the exterior should be removed or replaced. The repair procedure as presently developed and recommended will restore all of them.

(h) The entire exterior wall area between the 5th and 26th floors should be repaired, not just those areas which exhibit visible cracks.

(i) The repair work should have a completion date of not more than 18 months or less than 12 months after award of Contract.

(j) The Contractor shall hire a moving company for all furniture moving.

(k) The Contractor should have all leased equipment moved by the equipment lessor.

(l) Flammable and toxic materials should be stored in metal buildings on the 5th floor roof in locations to be designated. These buildings shall be protected by a locked security fence to prevent public access. The fence and the building shall be signed in accordance with their contents. The buildings containing large quantities of flammable materials should be further protected by an automatic fire extinguisher system of a size and type suitable for the materials contained in the structure, provided fire regulations of the City and State permit storage of flammable materials on City Hall premises.

(m) X-ray techniques should be utilized as the in-process inspection method to determine contractor performance.

5.0 COMMENTS

Of all the materials and processes tested, the last test panel on the 6th floor (see Plate 5) apparently furnished the best repair for the lowest cost.

The material “FR-450” and equipment used in this final test did not exist at the time the test program was initiated, but were developed for use on the City Hall. It was developed and produced by Delta Plastics Company. The automatic injection equipment used for the test was developed and produced by Pressure Grout Supply Company, Los Angeles, California.

When the FR-450 foam material showed promise, VTN and its contractors and suppliers proceeded with additional testing without requesting additional Contract coverage at that time.

A P P E N D I X “A”

Annex “A” - CONTRACT SCOPE OF WORK

ANNEX “A”

1. The test program of certain areas of the City Hall as shown in Figures 1 through 9 is designed to evaluate repair techniques under actual field conditions. The reports prepared as the result of the tests will assist in the preparation of project plans, specifications, estimates and bidding documents for the repairs to the exterior surfaces of the City Hall. The areas to be tested have been selected to furnish data on repairs for all degrees of damage.

2. The Contractor-Engineer shall use no less than two methods for the testing program.

3. The Contractor-Engineer will formulate a schedule of work by areas and floors to be submitted with his proposal.

4. The Contractor-Engineer will be responsible for the following work to be performed under this modification:

a. Drawings indicating panels to be repaired, cored, and tested.

b. specifications describing repair techniques and procedures.

c. Specifications for coring and testing.

d. Supervision of repairs and tests by subcontractors.

e. Define exact test areas for each subcontractor.

f. Define tests to be made.

g. Define exact process for each location.

h. Supervise subcontractor effort.

i. Provide photographic coverage of tests and core drilling.

j. Provide certified laboratory tests.

Figures 1 through 9 as referenced above may be found at

A P P E N D I X “B”

ORIGINAL DEFINITIVE SCOPE

OF WORK AND REQUIREMENTS

1.0 VTN ORANGE COUNTY’S SCOPE OF WORK

The scope of work established by the Contract is detailed in Appendix “A” and includes the following:

(a) Define exact test areas for each subcontractor.

(b) Define tests to be made.

(d) Coordinate buildings, facilities, parking availability with City

(e) Supervise subcontractor effort.

(f) Subcontractor effort:

(1) Prepare areas for injection.

(2) Inject filler material and clean area.

(3) Inject adhesive and clean area.

(4) Take test cores.

(5) Close core holes.

(6) Plug core holes.

(7) Clean up work area and remove contractor’s equipment.

(g) Correlate and report test results.

2.0 SERVICES TO BE FURNISHED BY CITY

For the duration of this test program on the City Hall, certain services were assumed to be available from the City at no cost. These services include:

(a) Sanitary facilities

(b) Water

(d) Parking for contractor’s trucks and equipment which were used for this work.

(e) A 4 to 6 foot wide aisle with guard as required to protect City employees and the general public.

(f) Before each phase, remove furniture and furnishing from immediate area where work is scheduled.

(g) After completion of each phase, return furniture to previous locations.

3.0 SAFETY

3.1 General: Test locations have been selected to minimize staging and scaffolding.

3.2 Specifications: The Contractors shall do their work in accordance with safety requirements of the Los Angeles Department of Building and Safety. The subcontractor shall also comply with applicable sections of the following Codes: EM-385-1-1, dated 1 March 1967, “General Safety Requirements,” Corps of Engineers; “Construction Safety Orders,” State of California, Department of Industrial Relations, dated October 3, 1970; and “Safety and Health Regulations for Construction,” Federal Register, Volume 35 No. 75, Part II, dated April 17, 1971.

The subcontractors shall furnish all necessary safety equipment. Scaffolding is a subcontractor responsibility. In hazardous locations such as on top of the cooling tower on the sloping metal roof at the 26th floor, adequate protection shall be provided. Handrails, toeboards and scaffolding shall be provided as required for each location. All solvents and other flammable and toxic materials must be stored in approved safety containers.

4.0 SPECIAL REQUIREMENTS

Due to the nature of work to be performed under this contract, certain special requirements exist or must be provided. These are as follows:

(a) The building will be occupied during the test program.

(b) The central air-conditioning servicing the areas of work will have to be shut down if odors or fumes prove objectionable.

(d) Accumulation of material and equipment beyond that required for the immediate task will not be permitted in occupied areas of the building.

5.0 TEST METHODS AND PROCEDURES

Tests on the job site shall be conducted to determine the following:

(a) Extent of void filling.

(b) Structural strength of repaired wall.

(d) Expansive pressure of FR-3 foam.

(e) Absorption of adhesive into wall material.

(f) Percentage of wall void volume.

Test cores will be removed from the test panels receiving injections and from four selected locations in unrepaired walls. All cores will be visually inspected to determine extent of void filling. Selected cores will be structurally tested.

All test data and those cores not broken during shear tests by the Testing Laboratory will be made available for inspection by prospective bidders.

6.0 TEST PANEL PROCEDURES FOR INJECTION SUBCONTRACTOR

The following procedure shall be followed by the injection subcontractors. Any deviation from this procedure must be approved by VTN Orange County prior to start of work.

6.1 Concrete Grout and Structural Adhesive as Follows:

(a) Protect surrounding areas and equipment from dust and debris during the injection port drilling process by installing temporary plastic protection floor to ceiling.

(b) Drill grout injection ports on approximately 2 feet on center geometric pattern, beginning approximately 6” above floor.

(d) Seal all cracks over 1/8” utilizing structural adhesive injection.

(e) Inject cement grout, with an expansive admixture to compensate for shrinkage, beginning at the bottom row of holes and working upward.

(f) All water, debris and other wastes resulting directly or indirectly from the grouting operation shall be cleaned up and removed by subcontractor.

(g) Provide temporary ventilation, central air conditioning return-air shutoff, and other precautions, as necessary for the health, safety and comfort of the workmen and occupants of the building.

(h) After the grout has taken a sufficient set (approximately three days), the structural adhesive shall be injected into cracks and holes from both the exterior and interior surface of the wall.

(i) Remove all material and equipment from job site.

(j) Clean area and remove all unsightly sealant material.

6.2 FR-3 Foam and Structural Adhesive as Follows:

(a) Protect surrounding areas and equipment from dust and debris during the injection port drilling process by installing a temporary plastic partition floor to ceiling.

(b) Drill foam injection ports approximately 2 feet on center, in a geometric pattern beginning approximately 6” above floor.

(d) Provide temporary ventilation, center air-conditioning shutoff and other precautions as necessary for the health safety and comfort of the workmen and occupants of the building.

(e) Fill all cracks over 1/8” by injecting high viscosity structural adhesive.

(f) Inject FR-3 foam into wall through previously drilled holes and cracks beginning at the bottom row of holes and working upward.

(g) After completion of the foam injection process, all surplus materials solvents shall be removed from the occupied area of the building.

(h) Inject structural adhesive from both the exterior and interior of the wall if required.

(i) Remove all material and equipment from job site.

(j) Clean area and remove all unsightly sealant material.

A P P E N D I X “C”

FIELD TEST PROGRAM

1.0 SCOPE OF WORK

The Scope of work, as originally envisioned, considered two materials: FR-3 foam and an expansive cement grout, used in conjunction with a structural adhesive. During the course of work on this program, two new materials (FR-4 and FR-450) were developed by Delta Plastics and field tested on the Los Angeles City Hall.

Materials in these test areas were injected by both the Hunt Process Company, Santa Fe Springs, California (FR-3 Foam and structural adhesive) and by Warner Engineering Services, Los Angeles, California (expansive cement grout), with material supplied by the Delta Plastics Company, Santa Fe Springs, California. VTN performed all management and coordination functions with regard to this above scope effort.

2.0 MATERIALS

Materials used in the field test program are as follows:

2.1 Non-Structural foam:

2.1.1 FR-3 Foam: FR-3 Foam is produced by the Delta Plastics company. This material is a two component, light, non-flammable foam with excellent adhesive properties. The material may be either batch or in-line mixed and exhibits excellent penetration and bond characteristics. In the free state, the expansion ratio is approximately 20 to 1. The unit strength, however, is quite low and makes the material unsuitable as a structural material. This low unit strength characteristic does not present a problem if the application of the material is properly engineered. The normal use of the material is to fill voids to prevent the intrusion loss of the structural adhesive or as a fire retardant insulating material. The flame spread rating is less than 19 and smoke density of 50. This material either mixed or in its component form, has a non-objectionable odor. This is a proprietary material and is presently in the process of being patented by the manufacturer.

2.2 Structural Foam:

2.2.1 FR-4 Foam: The FR-4 foam was developed by Delta Plastics during the test program specifically for the particular needs of this job. When the need for a high-unit strength material to restore, at least to a degree, the integrity of the exterior walls became apparent, discussions were held with Delta and, as a result, this new material was developed. It is a two component foam-in-place material, similar to the FR-3. Its expansion ratio in the free state is approximately 6:1 with a strength of approximately 100 psi compressive strength at maximum expansion. It also has a non-objectionable odor.

The fire retardance properties remain the same as the FR-3, with a flame spread of 19 and smoke density of less than 75. The storage of these materials on the job site requires no special precautions because both components are classified as non-flammable. The most flammable ingredient of the “A” component has a flash point in excess of 550°F.

At this time, the FR-4 foam is a proprietary material and is in the process of patent application by the manufacturer.

2.3 FR-450 Foam

The FR-450 foam was developed by Delta Plastics following the testing of FR-4, especially to have a foaming material that would perform the dual role of filling the wall voids and providing a structural strength bond for the walls. The difference between the two materials is that the FR-450 has an extended pot life, 4-1/2 minutes at 70°F.

2.4 Structural Adhesive

2.4.1 Delta Plastics Company: Type TM-15-9018 A&B, pot life 10-20 minutes;

2.4.2 Delta Plastics Company: Type AS13-9010 A&B, pot life 40-50 minutes;

2.4.3 Sika Type Colma Dur LV: pot life 15 to 30 minutes.

2.5 Expansive Cement Grout

Expansive Cement Grout consists of batch mixtures of the following:

6 gallons water

1 sack (94 lbs.) regular Portland Cement

3/4 lb. Expando Grout G.A.

1/2 gallon Expoweld concrete binder

3.0 INJECTION PROCEDURE

Injection of materials was placed in test panels in accordance with the schedule of events, as indicated in Table 1, herein. The injection equipment is described in Paragraph “INJECTION PLACEMENT EQUIPMENT”.

3.1 FR-3 Foam and Structural Adhesive Injection

3.1.1 Location: 5th floor-east wing-east wall-north panel.

3.1.2 Subcontractor: Hunt Process Company

3.1.3 Method of Repair: The method of repair was to inject FR-3 foam followed by Delta TM-15-9018 low viscosity structural adhesive (see Table 1).

3.1.4 Injection Port Spacing: The foam injection port spacing varied from 3 inches to 12 inches, with the majority of this panel being done on a 8” x 12” grid. The holed were 12” deep, 3/8” diameter. The adhesive was injected through open cracks. The cracks were provided with points at 3 to 6 inch intervals, most of which were used to determine how far the adhesive had moved.

3.1.5 Repair: the foam injection ports were drilled in the face of the veneer and around the window casement. There were 12 ports used on the interior in an effort to place foam in the fireproofing around the column. Injection was performed by batch mixing and manual injection.

The structural adhesive was placed in open cracks on the exterior only. The structural adhesive was injected with an in-line mixing and injection system.

3.1.6 Description of Holes:

FR-3 Foam Injection: Holes were drilled with a 5 inch carbide twist drill from the exterior. A drill of this length penetrated the ceramic veneer and the voids immediately behind the tile. Attempts were made to inject the foam. The result of these attempts were judged to be inconsistent and an insufficient amount of material could be injected. The injected material was not penetrating the crack and void matrix. This was determined by drilling test holes to determine the extent of foam distribution. Longer drill bits were obtained and the wall drilled to a depth of 12 inches. The acceptance of material in these holes was much more encouraging. Test drilling indicated that the voids were larger immediately behind the tile unit at the upper portion of the tile. A total of 37 quarts of FR-3 form was placed in this panel, utilizing batch mix and injection with caulking guns. Coring of the wall revealed that penetration of the foam was not sufficiently complete. The dust from drilling had apparently effectively plugged passages and prevented the material from entering the void matrix.

Structural Adhesive Injection: Cracks on the exterior of this test panel were sealed with a resinous thermosetting wax. Injection openings were left in this seal material providing injection ports. All cracks were injected from the exterior through these ports since the cracks at this location were relatively small and intrusion by the expanding foam was not a problem. Interior plaster showing evidence of cracking was removed and the visible cracks were injected. Approximately one quart of material was injected from the interior. With the plaster, it was apparent that much of the plaster was lensed loose from the brick. The gap behind the plaster was up to 1/8 inch. The plaster was removed from the entire panel by simply prying it off.

Injection ports were provided throughout the interior crack matrix and the entire interior surface of the panel was sealed and a low viscosity adhesive injected. Some cores again showed incomplete penetration of the smaller cracks. In some cases what appeared to be cracks were only fractures in the glaze; other cracks came from the back of the ceramic veneer, but failed to penetrate the exterior and therefore, were not injected with structural adhesive. The same problems of window case leaking and ceramic veneer cleanup were evidenced here, only to a greater degree.

3.1.2.8 Core Evaluation: Core removal at this location again revealed failures in the original wall structure. The bonds in the parent material were sufficiently tight to prevent intrusion of the repair material, but were unable to withstand the forces of core drilling or subsequent handling. The foam did not fill a satisfactory percentage of the existing voids nor did the low viscosity adhesive effectively repair enough of the cracks to be considered as having done an adequate job of repair.

3.1.3 Location: 26th Floor-South Wall-West Panel.

3.1.3.1 Subcontractor: Hunt Process Company.

3.1.3.2 Method of Repairs: The method of repair was to inject FR-3 foam by manual injection, followed by Delta TM15-9018 low and moderate viscosity structural adhesives (see Table 1).

3.1.3.3 Injection Port Spacing: FR-3 foam port spacing 15” x 15”, 12” deep, structural adhesive, 8 to 10” along cracks.

3.1.3.4 Repair: Foam injection ports were drilled in the face of the ceramic veneer and in the window casement. Injection of foam was accomplished using batch mixed material and manual injection methods. Adhesive injection was done utilizing existing cracks on both the exterior and interior upper half; the lower half was drilled on a 12” grid. Injection in holes of this grid proved unsuccessful and then injection was performed along the crack lines with success. Low viscosity adhesive was injected utilizing in-line mixing and injection equipment.

3.1.3.5 Description of Injection Procedure.

3.1.3.5.1 FR-3 Foam Injection: Prior to the injection of foam in the 26th floor panel, all exterior cracks were sealed with either a paste or low viscosity adhesive, depending on the size of the crack. Also prior to the injection of foam in this panel, the cores were taken from the 6th floor panel. The holes for injection of foam in this panel were drilled with a 1/2 inch roto-hammer (electric) in lieu of 3/8 inch holes drilled with a conventional drill. This was done for several reasons: (1) to provide a larger injection port; and, (2) the roto-hammer does not produce the quantity of fine dust which apparently plugs the smaller crack channels, preventing foam entry into voids. The condition of the wall is such that when the drill contacted brick on the inner wall, on several occasions the brick was forced from its seal in the mortar bed. This further verifies the minimal bond strength remaining in the mortar.

3.1.3.5.2 Structural Adhesive Injection: The size and extent of cracking and spalling in this test panel made structural repair efforts prior to injection of FR-3 foam mandatory. Cracks in this panel were up to 1 inch wide causing horizontal displacement of walls around window frames. One of the ceramic veneer pieces was severely damaged by spalling and had to be sealed prior to other work. In the larger cracks, a semi-thixotropic adhesive was manually injected. Subsequent investigation revealed that this material penetrated to a depth of 6 to 8 inches.

The smaller cracks (under 1/16 inch) were machine injected with low viscosity adhesive prior to foam injection. The interior of this panel was shattered to a degree that injection ports were placed in cracks in the upper portion of the wall and the entire face coated with a polyester sealer. In the lower portion of the wall, ports were placed in the open cracks and additional ports were placed in holes drilled in the wall between cracks. This portion of the wall was not sealed so that penetration of the material in the wall could be observed. Injection in all cases was started at the bottom of the panel and progressed upward. The ports placed over the cracks accepted material much more readily than did those placed in drilled holes. In fact, the majority (approximately 90%) of the material injected was placed through the ported cracks, with only an occasional drilled port accepting adhesive. This apparently was due to the drilled hole not reaching the crack-void matrix. The injection done on the exterior was done through the ports left in the crack sealant as well as some bonded in ports. The time required to inject low viscosity adhesives into a wall structure like that of City Hall combined with the material quantities seems to indicate that it is not an economical method of repair. The problem of both foam and adhesive leakage around windows became acute at this location. The clean-up problem on panels of this damage level is severe. Any structural adhesive which is allowed to cure on the surface of the ceramic veneer cannot be removed without destroying the ceramic glaze. The residual staining problem resulting from the use of foam on the glazed surface of the ceramic veneer must be resolved. This will be done by changing the sealing procedure.

3.1.3.6 Core Evaluation: Evaluation of cores removed from this test location indicated more than acceptable repair. The foam did not reach all the cracks and voids that it should have, but this may be due to the manual injection method. Because of the insufficient foam placement an excessive amount of low viscosity adhesive was apparent in the cores.

Some of these cores failed from the force of core drilling either in a bond that was too tight to permit repair material intrusion, or in masses of fine rubble and lime mortar.

3.2 Expansive Cement Grout and Low Viscosity Structural Adhesive Injection

3.2.1 Location: 5th Floor-East Wing-East Wall-South Panel.

3.2.1.1 Subcontractor: Warner Engineering services.

3.2.1.2 Method of Repair: Method of repair was to inject expansive cement grout followed by Delta AS13-9010 low viscosity structural adhesive (see Table 1).

3.2.1.3 Injection Port Spacing: Cement grout was injected on a 15” x 15” grid, low viscosity adhesive was batch injected along existing cracks at 8 to 10 inch intervals.

3.2.1.4 Repair: The cement grout injection ports were drilled from the interior surface of the wall. These holes were drilled 12” deep and 1-1/8” in diameter. Low viscosity injection ports were bonded to the open crack at 3 to 4 inch intervals; however, injection was performed at 8 to 10 inch intervals with the remaining ports used to observe the movement of the adhesive. The low viscosity adhesive was injected using batch mixed material in a refrigerated pressure pot.

3.2.1.5 Description of Injection Procedure:

3.2.1.5.1 Expansive Cement Grout Injection: The procedure for injection of expansive cement grout was aided by information from cores removed from the 5th and 6th floor foam injection tests. The holes for injection of cement grout were drilled with a 1-1/8 inch pneumatic drill. Due to the transmitted noise of such an operation, the drilling was conducted after 5:00 p.m. at the request of the City. Dust enclosures were constructed at each location to minimize dust spread. Injection holes were drilled on approximately a 15 inch by 15 inch grid pattern to a depth of approximately 12 inches. Prior to injection with grout, the wall panels were soaked with water. This procedure, though is very messy, is required to prevent premature drying of the grout and thus plugging the cracks through which it must flow. This appears to be the messiest portion of the job due to the problems of water control as it leaks or gushes from the wall. The injection was started with the bottom row of holes and progressed upward until the panel had been completely filled. The injection continued at a port until either a pressure of 18 psig was attained with no apparent flow, or until the grout emerged from a port at least one row above the injection point. In one case, grout leaked from a crack approximately 12 feet laterally from the point of injection. Subsequent cores indicated that the grout traveled more than 15 feet laterally at this location.

Grout was injected from the interior on the 5th floor, from the exterior on the 6th floor and on the 26th floor was injected partly from each side. There seems to be no apparent difference in performance related to whether the injection is done from the inside or the outside. The grout was pumped utilizing an air driven auger pump. A gauge was located at the pump outlet and in the line near the injection point. This gauge setup was used to determine pressure differential and thus refusal. There was little mess associated with this operation; this, however, is attributed to the care exercised by the personnel engaged in the injection operation and should not be considered as normal for a grouting operation.

3.2.1.5.2 Structural Adhesive Injection: Plastic injection ports were bonded to cracks in the exterior and the cracks sealed utilizing SIKA COLMA DUR GEL. These ports were installed at 3 to 4 inch intervals along the crack with injection occurring every third or fourth port. The remaining ports were utilized to check on the progress of the injection. Injection was begun at the bottom of the cracks and progressed upward until the entire crack matrix had been injected. The equipment utilized for the low viscosity adhesive injection was batch mixed and injected, utilizing a refrigerated pressure pot.

3.2.1.6 Core Evaluation: The cores removed from this panel revealed good penetration of cement grout in general. Some of the voids in the wall remained unfilled as did many of the cracks. Cores failed at the bond plane of the inner brick and the rubble from the force of core drilling. Some cores also crumbled when large areas of mortar were encountered in the rubble section of the wall. It was apparent that more low viscosity adhesive was needed.

3.2.2 Location: 6th Floor-North Wing-North Wall-East Panel.

3.2.2.1 Subcontractor: Warner Engineer Services.

3.2.2.2 Method of Repair: Method of repair was to inject expansive cement grout followed by Delta AS13-9010 structural adhesive (See Table 1).

3.2.2.3 Injection Port Spacing: The injection pattern for expansive cement grout was a 15” x 15” grid pattern. The structural adhesive was injected on 8 to 10 inch intervals along the exterior cracks and on a 10” x 10” pattern on the interior.

3.2.2.4 Repair: The cement grout was injected from the exterior through holed drilled 12” deep. The low viscosity adhesive was injected in ports placed on cracks on the exterior surface. There were visible cracks in the interior plaster when the plaster was chipped away. Only a few hairline cracks were visible. The entire wall section was drilled 8” deep on a 10” x 10” grid and low viscosity adhesive injected.

3.2.2.5 Description of Injection Procedure:

3.2.2.5.1 Cement Grout Injection: (See Paragraph 3.2.1.5.1 for description of cement grout injection procedure).

3.2.2.5.2 Structural Adhesive Injection: The cracks on the exterior of this panel were sealed with the SIKA epoxy and plastic ports were bonded in at intervals along the surface. Injection proceeded from the bottom up in the usual manner. There were several cracks visible in the interior plaster, when plaster was removed these cracks were visible in the brick. Ports were then placed over these cracks and the rest of this wall panel was drilled on a regular (10” x 10”) grid pattern, 8” deep and ports bonded at each drilled hole. Injection was begun at the bottom of the panel and the ports installed on cracks again accepted the majority, approximately 90% of the injected material from the interior. Injection pressures had to be reduced to 20 psig from 40 psig, to prevent tearing the ports off the interior brick. These failures occurred in the brick, and not in the epoxy used to bond the ports down.

3.2.2.6 Core Evaluation: The cores removed from this panel revealed good filling with the cement grout, but some voids remained unfilled. Although this panel was injected with low viscosity material from both the interior and the exterior, many cracks remained unfilled. Cores continued to fail in the same manner as on previous panels.

3.2.3 Location: 26th Floor-South Wall-East Panel.

3.2.3.1 Subcontractor: Warner Engineering Services.

3.2.3.2 Method of Repair: The method of repair was to inject expansive cement grout followed by Delta AS13-9010 and SIKA COLMA DUR LV (See Tables 1 and 7).

3.2.3.3 Injection Port Spacing: Cement grout was injected on a 15” x 15” grid. The low viscosity adhesive was injected along existing cracks and on a 6” x 10” grid pattern.

3.2.3.4 Repair: The cement grout on the upper half of the panel was injected through 1-1/8 inch holes drilled 12” deep from the inside, the lower half of the panel was injected in the same manner from the outside surface. Low Viscosity structural adhesive was injected into ports spaced along the cracks on the exterior wall. The interior of the wall was divided vertically, the left half had ports placed only on the cracks, the right half was drilled in the mortar joints on a 6” x 10” grid with ports also bonded to the cracks. There was no significant difference in quantities of material accepted by either half of the wall. As in the past, 95% of the material was injected in the ports placed over existing cracks.

3.2.3.5 Description of Injection Procedure:

3.2.3.5.1 Cement Grout Injection: (See Paragraph 3.2.1.5.1 for description of cement grout injection procedure).

3.2.3.5.2 Low Viscosity Structural Adhesive Injection: The exterior of this panel exhibited severe cracking and extensive sealing was required before injection could begin. Ports were placed on all cracks and the cracks were filled with a thixotropic structural adhesive. Injection at 30 psig was begun in the normal manner from the bottom of the crack working upward. Injection at a single port on the exterior produced leaks over approximately a 10-square-foot area of porosity and fine internal cracking characteristic of the existing wall condition. Leaking was encountered at repointed mortar joints which appeared to be tight but which leaked when internal pressure is applied.

The interior of the panel was divided vertically. The left half of the panel had injection ports installed on the visible cracks only. The right half was drilled on a regular grid pattern with injection ports installed on all drilled holes. Ports were also installed on all cracks to observe material penetration. There was very little of low viscosity structural adhesive accepted by the drilled ports; less than 5% of the total injected.

The amount of low viscosity structural adhesive injected was approximately the same in both halves of the panel. By means of these tests, the theory of being able to drill on a regular pattern and restore the structure was disproved. Severe leaking was again encountered around the windows. It is apparent that the window frames will have to be sealed prior to the injection to prevent the problems and mess associated with these leaks. The interior surface of this panel was sealed using the low viscosity structural adhesive and by painting it over the entire surface. This appeared to be a very effective method of sealing.

3.2.3.6 Core Evaluation: The cores removed from this panel revealed a more than acceptable level of repair. The expansive cement grout did not appear to reach all the cracks and voids that it could have. The low viscosity structural adhesive did an excellent job of filling the crack-void matrix. The low viscosity structural adhesive filled large voids material which is not desirable due to its chemical-physical properties. A few failures occurred in the bond plane of the rubble fill to the inner brick from the force of core drilling.

3.3 FR-4 Foam Injection: During the course of testing work being done at the Los Angeles City Hall, conferences were held with Delta Plastics Company regarding the desirability of having a foaming material that would perform the dual role of filling the wall voids and provide a structural strength bond for the walls. A material FR-4 Foam was developed by the above company to provide a structural strength bond for the walls. FR-4 foam was later modified for a longer pot life and called FR-450, and was tested as hereinafter described.

3.3.1 Location: 26th Floor-South Wall-West Panel.

3.3.1.1 Subcontractor: Hunt Process Company.

3.3.1.2 Method of Repair: The method of repair was to inject FR-4 experimental foam.

3.3.1.3 Injection Port Spacing: Approximately 10” on center in casement and small area on face of veneer.

3.3.1.4 Repair: A small area approximately 8-square-feet, was drilled with 1/2” diameter holes 12” deep from the exterior. The FR-4 foam was batch mixed and manually injected.

3.3.1.5 Description of Injection Procedure: When limited quantities of the FR-4 series material became available, Hunt Process offered to inject this material. This material was placed on the 26th floor; an 8-square-foot area of wall was drilled with injection ports. In this area, six quarts of FR-4 foam was placed. Injection was done using manually operated caulking guns. Severe leaking of FR-4 foam occurred around the window.

3.3.1.6 Core Description: The cores showed fair to good penetration. The differential expansion and hardness properties were apparent in the cores. The foam in the large voids was softer than that in cracks due to differential expansion.

3.3.2 Location: 6th Floor-North Wing-North Wall-West Panel.

3.3.2.1 Subcontractor: Hunt Process Company.

3.3.2.2 Method of Repair: Method of repair was to inject FR-4 foam (pilot production) material.

3.3.2.3 Injection Port Spacing: 10” x 15”

3.3.2.4 Repairs: Injection ports were drilled in the exterior face of the veneer and in the casements. These holes were 1/2” diameter and 12” deep. Approximately 20-square-feet were included in this test area.

3.3.2.5 Description of Injection Procedure: The test area for this material was again selected for a moderate level of damage and accessibility. The injection was done using batch mixed manually injected FR-4 foam. Polyethylene sheet was used to protect the ceramic veneer from contact with the foam and masking tape was used to seal the cracks.

3.3.2.6 Core Evaluation: The cores removed from this location showed very good penetration of the FR-4 material. As has been the case in other locations, some voids were unfilled, apparently these were discontinuous. There was some evidence of uncured resins. This was determined to be the result of incomplete mixing.

3.4 FR-450 Foam Injection

3.4.1 Location: 6th Floor-South Wing.

3.4.2 Subcontractor: Warner Engineering Services.

3.4.3 Method of Repairs: Method of repair was to inject FR-450 machine injected foam (see Table 1).

3.4.4 Injection Port Spacing: Ports were spaced at 15” x 15” grid and in window casement at 8” intervals.

3.4.5 Repair: Cracks in the face of the veneer were sealed with a structural adhesive and the foam then injected at pressures up to 50 psig.

3.4.6 Description of Injection Procedure: The third test panel injected with the structural foam was performed utilizing machine injection techniques. The material used was from a production batch. The machine injection equipment was developed and built by Pressure Grout Supply Company.

There were 14 gallons of material placed in approximately 30-square-feet of wall surface. Three gallons of this material was wasted in flushing the mixing head or in test samples. Injection at a single location continued until either a pressure of 50 psig was reached or leaking on the interior of the wall was so severe as to make further injection impracticable.

3.4.7 Core Description: The cores removed from this test area exhibited excellent crack penetration and void filling. Two of the cores failed at the bond plane of rubble fill to inner brick from the force of core drilling. One core had to be broken to remove it as it was bonded to the steel column. Another core was deliberately broken due to a pipe anchor attached to the inner brick. The differential hardness and expansion ratios were again observed in these cores. The estimated average expansion ratio was between 2-1/3 and 3:1.

4.0 AUTOMATIC PLACEMENT EQUIPMENT OF FOAM ADHESIVES

4.1 Handling Problems of Foam Adhesives: The state of the art at the time the test program began for injecting FR-3 foam was to use a hand operated caulking gun with disposable cartridges. At that time, the FR-450 foam had not yet been developed. There were several problems which had not been overcome that caused this condition, and they follow:

(a) Differential viscosities of A & B component materials.

(b) High friction loss in lines.

(d) Short pot life of mixed material.

(e) Extreme adhesive properties of mixed materials.

With the advent of the FR-450 material, the above handling problems became more pronounced.

The advantages of the caulking gun are obvious as follows:

(a) Small quantity of mixed material.

(b) Throw-away containers.

(d) Easy clean-up.

(e) Highly skilled applicators are not required.

There are certain disadvantages to this process however; they are as follows:

(a) Injection cannot be continuous.

(b) Mixing error probability is greater.

(d0 Low overall injection rate.

(e) Material may react before injection at a particular location is complete.

Automatic equipment also has certain advantages and disadvantages. Some advantages are as follows:

(a) Continuous injection.

(b) Injection at a known flow rate.

(d) Injection at a controlled pressure.

(e) Faster injection.

(f) Good Proportioning and mix controls.

(g) Injection at a particular location can be completed before reaction begins.

Some disadvantages of this process are as follows:

(a) High cost of equipment.

(b) Danger of damaging equipment with both components and mixed materials.

4.2 Structural Adhesive Injection Equipment: There are two basic types of structural adhesive injection equipment in-line mixing and batch mixing. Each of these basic processes have advantages and disadvantages, depending on the job to be performed and the type of material specified for injection. During the test program, both types of equipment were utilized successfully. After cores were removed, there was little apparent difference in them. The batch mix process did, in fact, place more material in the damaged wall. Therefore, no recommendation will be made as to a specific equipment requirement, rather the material will be specified for specific uses and it will be the responsibility of the application contractor to select the equipment for its proper placement.

4.3 FR-3 Foam Injection Equipment: The FR-3 foam used in the test program on the City Hall is a product developed in late 1971, At the time of the test program, as defined in the Scope of Work, no equipment existed to automatically mix and inject this material. Up to the time of this writing, approximately 500 gallons of FR-3 foam has been placed by mixing one quart kits, poured into one quart hand caulking guns and injected into the walls manually. Some of the projects on which this material was used are the Ventura County Court House and a Kraft Dairy in Iowa. After the test program was completed, a contractor who did not perform the previous foam injection developed equipment suitable to handle the FR-450 material.

4.4 FR-450 Automatic Injection Equipment: An acceptable in-line injection unit used by Warner Engineering for FR-450 foam injection was developed for the tests. This equipment consists of two basic components: Model PP-MP-A pumping and metering unit; and Model MH-E-FM mixing and injection head, manufactured by Pressure Grout Supply Company. This will also inject FR-3 and FR-4 foam.

The pumping and metering unit is a portable piece of equipment which is driven by compressed air. Contained in this unit are tanks for the A and B components and purging solvent, together with the metering pump and their associated drive equipment.

The mixing and injection unit is hand held against the injection port and is driven by compressed air. The mixing is accomplished by a dynamic heating process. The injection unit is supplied with metered amounts of the material to be mixed, solvents and air for purging and cleaning and compressed air for power. The exact configuration of this equipment is proprietary.

In its present configuration, the injection is controlled by maintaining close communications between the operator of the pumping unit and the injection unit. Extreme care must be taken to prevent the materials from reacting in, and thus destroying the mixing and injection unit. This care is necessitated by the very high cost of the mixing unit.

5.0 OCCUPANT DISTURBANCE

The considerations for occupant disturbance have been a factor in the selection of materials and processes for use on this building. The factors involved in disturbance include, but are not limited to, the following: odor, noise, and work area.

5.1 Odor: Many of the structural adhesives contain materials which exude offensive odors. Some of these odors are of sufficient strength and character to cause discomfort or illness. In the performance of work on this specific building, where much of the work must be done from the interior, odor is of necessity an item to be considered in material selection. The group of poly-sulfide based materials are generally unacceptable because of this characteristic. The general maximum level of odor tolerable in this job is the SIKA COLMA-DUR LV and Delta AS13-9010. These materials do have a definite odor which is offensive to some people, but may be considered as a standard for maximum odor emission.

There were some objections to the above-specified odor level by City personnel. However, these materials have had extensive use in occupied structures, including hospitals with a minimum of problems; therefore, they are considered to be acceptable for use on the City Hall.

5.2 Noise: Noise levels involved with construction efforts can reach levels which would interfere with the work performance of City personnel and seriously affect tape recording equipment in use during public hearings. The effect upon public hearing is of course the more significant problem in this case.

Since the use of pneumatic drills has been determined as necessary to provide injection ports and this drilling produces an excessive amount of noise, the operation of small air compressors, not to exceed 1 hp appears to be the maximum acceptable noise level in occupied areas. There have been some objections to noise of this level. However, equipment of this type has been in a hospital for some months without problems and is judged not to be excessive.

5.3 Work Area: The work area required for restoration of the exterior walls must be kept to a minimum. Access will be required to the interior surfaces of al exterior walls. Carpets where they exist, adjacent to these walls, must be removed and protected. Nonstructural interior partitions may have to be removed and replaced on the as-required-basis, depending upon the extent of repair required by that particular wall segment.

It appears at this time that a clear area of about 6 feet will be required to perform these repairs. In addition, access will be required from the elevators to the point of work.

Furniture which requires movement for the test program was to have been done by the City. This work was, in fact, done by the contractors. The only assistance received from the City was the removal of a segment of a nonstructural partition. All other work, including removal and replacement of radiators was, in fact, performed by the contractors.

7.0 STRUCTURAL EVALUATION

7.1 Observations: Foam injection has been evaluated by:

7.1.1 Observation and testing of made up samples

7.1.2 Examination of core samples removed from walls, both prior to and subsequent to foam injection observation of field procedures.

7.1.3 Physical testing of core samples and evaluation of test results. Samples were made up with used clay brick and FR-450 foam. One type of sample was made by bonding the faces of two bricks with foam, while another type was made by stacking alternately faced brick in a cardboard box and pouring the foam into the container, allowing the natural expansion of the foam to fill the voids. These samples were then tested to destruction.

7.1.4 Field Methods of Foam Injection are discussed elsewhere in this report; however, two foam injection systems were observed: manual injections, and injection utilizing automatic mixing and injection equipment. Subsequent to injection, cores were removed from both treated and untreated wall areas for laboratory testing. Samples tested were subjected to shearing and compression type loads. In each case they were tested to destruction. Shear tests were made utilizing a specially manufactured collar, which retained one-half of the sample while permitting the other half to slide at failure in such a manner that a shear mode was simulated. compression samples were capped with sulphur prior to testing. All testing was done utilizing the “Tinius Olsen” testing machine, the “Baldwin” testing machine. Both shear and compression test results were wide ranging, and as such, little weight should be ascribed to actual numerical values obtained. Also, it was not possible to obtain “testable” samples from untreated wall areas due to crumbling of the material under the action of the coring machine and the general condition of the wall. Samples of treated wall varied in condition from poor to excellent, In some cases, the samples were composed of approximately 50 percent structural adhesive. Numerical test results do have some correlation to the individual samples tested to the degree that those cores that had good structural adhesive penetration generally tested higher than cores that had poor penetration. As such, numerical values appear to be dependent on degree of penetration, condition of original brick, and condition and quality of original mortar. Failure of samples in every case occurred predominantly in original material.

7.2 Quality Assurance Recommendations: The normal quality control procedure for structural adhesive injection is to take a core at specified frequencies, based on length of cracking. This method does not appear suitable for the specific problems associated with the Los Angeles city Hall structure. In place of the normal frequency of core drilling, a sampling plan is proposed:

(a) Cores shall be drilled per 1,000 square feet of exterior wall surface. These cores shall be located in an area less than 5 percent of the total, selected at random after completion of the area.

(b) If two of the three cores taken are not properly repaired, then three more cores shall be taken. These additional cores shall be taken at the expense of the Contractor.

(c) If two of the three cores taken on the second sample are not properly repaired, then the entire area involved in this inspection shall be reworked by the Contractor at no cost to the Government.

7.3 X-Ray Inspection: The possibility of utilizing X-Ray techniques to determine voids in the unrepaired wall sections and to determine the extent of injection has been discussed with engineers and contractors in the past with little, if any, hope for success. Twining Laboratories expressed a desire to attempt X-Ray evaluations. Initial testing was performed on cores removed from the structure. The results of these tests were sufficiently encouraging to warrant full scale testing on the subject building.

On Friday, March 24, 1972, full scale tests were conducted on wall panels of the City Hall Building. Photos were taken of both unrepaired and repaired segments of the wall. The comparison of the photos of the unrepaired and repaired wall segments showed a marked difference resulting from the intrusion of the foam material.

The X-Ray process seems to be a more economical method than that of removing and replacing cores. If disputes occurred over X-Ray interpretation, cores could still be taken as a final check.