Specification:Restoration of concrete in historic structures

__NUMBEREDHEADINGS__

=GENERAL=

Measurement of Concrete
The quantity of concrete to be paid for will be the number of cubic meters cubic feet placed in the completed and accepted renovated areas.

Payment for Concrete
The quantity of concrete, measured as specified, will be paid for at the contract unit price. The unit price for concrete will include full compensation for furnishing labor; materials; tools and equipment; and for performing work involved in repair of the areas as specified.

SYSTEM DESCRIPTION
The Contractor is responsible for equipment, materials, testing, labor and other items and services required to accomplish the work. Equipment and techniques proposed for use in the work shall not be used until they have been demonstrated and approved. Materials and equipment, which have not been approved for use in the work, shall not be stored or brought on to Government property. Provide equipment, materials, and labor to demonstrate materials, equipment, and techniques proposed for use in the work. Perform the demonstrations at the site, at a time and location as directed. The demonstration shall include surface cleaning, excavation, surface patching (including finishing, texturing, and curing materials and methods), curing, safety procedures, surface finish and appearance. The Contractor's quality control shall conform to Section 01 45 00.00 10 QUALITY CONTROL. All sampling and testing shall be the Contractor's responsibility, and shall be performed by an approved independent commercial testing laboratory, except as otherwise specified.

Compressive Strength
Each class or mixture of concrete and mortar proposed for use in the work shall have a 28-day compressive strength matching the compressive strength of the adjacent existing concrete in the structure as determined by ASTM C39/C39M for concrete and ASTM C109/C109M for mortar. Determine the compressive strength of the existing concrete from testing of samples for each portion of the work in accordance with ASTM C42/C42M. Take test specimens of existing concrete from a sound and intact representative portion of the structure, at locations indicated.

Air Entrainment
Each class or mixture of concrete and mortar proposed for use in the work shall have a total air content matching the total air content of the adjacent concrete. Determine air content of the proposed mixture in accordance with ASTM C231/C231M. When air-entrained concrete is required for resistance to freezing and thawing, the concrete shall contain an air-entraining admixture conforming to ASTM C260/C260M and having an air content as indicated in ACI 301MACI 301, (Table 3.4.1).

Admixtures
Concrete may contain admixtures, such as pigments, water reducers, high-range water reducers, or set retarders to provide special properties to the concrete. Use of admixtures shall be subject to approval.

Cementitious Content
Each class or mixture of concrete and mortar proposed for use in the work shall have a cement content matching the cement content of the adjacent existing concrete in order to provide uniform strength, weathering characteristics, and appearance of repaired surfaces in relation to existing surfaces.

Slump
Determine slump in accordance with ASTM C143/C143M, and within the following limits:

Proportions of Mixtures
 Provide trial batches that contain materials proposed to be used in the project. Make trial mixtures having proportions, consistencies and air content suitable for the work based on methodology described in ACI 211.1, using at least three different water/cement (w/c) ratios. In the case where ground granulated iron blast-furnace slag conforming to ASTM C989/C989M is used, the mass of the slag will be substituted in the equations for the term P which is used to denote the mass of pozzolan. Design trial mixtures for maximum permitted slump and air content.

The concrete and mortar patching mixtures shall be designed using the lowest practical w/c ratio. Report the temperature, slump, and air content of the concrete and mortar mixtures in each trial batch. For each w/c ratio, at least three test specimens for each test age shall be made and cured in accordance with ASTM C192/C192M and ASTM C109/C109M. They shall be tested at 7 and 28 days in accordance with ASTM C39/C39M for concrete and ASTM C109/C109M for mortar. From these test results plot a curve showing the relationship between w/c ratio and strength. For each strength of concrete the maximum allowable w/c ratio shall be that shown by these curves to produce an average strength as specified in paragraph Average Strength. Materials, physical and chemical properties, and composition of concrete and mortar patch mixtures shall match the existing concrete to be repaired, except that patching mixtures shall have the lowest total chlorides content practical and shall conform to ACI recommendation for maximum permitted total chloride content.

Submit the results of trial mixture along with a statement giving the maximum nominal coarse aggregate size, aggregate grading, and the proportions of all ingredients that will be used in the manufacture of each strength of concrete, at least 14 days prior to commencing concrete placing operations. Aggregate quantities (by mass) shall be based on the saturated surface-dry condition. Include in the statement a complete petrographic analysis of the aggregates proposed for use in the concrete. The statement shall be accompanied by test results from an independent commercial testing laboratory, attesting that the proportions selected will produce concrete of the qualities indicated. No substitutions shall be made in the materials used in the work without additional tests to show that the quality of the concrete is satisfactory. 

Average Strength
In meeting the strength requirements specified, the selected mixture shall produce an average compressive strength exceeding the specified strength by the amount indicated below. Where a concrete production facility has test records, establish a standard deviation. Test records from which a standard deviation is calculated shall represent materials, quality control procedures, and conditions similar to those expected; shall represent concrete produced to meet a specified strength or strengths within 3.5 MPa 500 psi of that specified for proposed work; and shall consist of at least 30 consecutive tests. A strength test shall be the average of the strengths of two specimens made from the same sample of concrete and tested at 28 days or at other test age designated for determination of the specified strength.

Test Records Exceeding 29
Required average compressive strength used as the basis for selection of concrete proportions shall be the larger of the specified strength plus the standard deviation multiplied by 1.34 or the specified strength plus the standard deviation multiplied by 2.33 minus 3.5 MPa 500 psi.

Test Records Less Than 29
Where a concrete production facility does not have test records meeting the above requirements but does have a record based on 15 to 29 consecutive tests, a standard deviation may be established as the product of the calculated standard deviation and a modification factor from the following Table:

Sampling and Laboratory Testing of Materials
Sampling and testing shall be performed by an approved independent commercial testing laboratory, or by the Contractor subject to approval. Should the Contractor elect to establish testing facilities, no work requiring testing shall be permitted until the Contractor's facilities have been inspected and approved. All sampling and testing shall be the Contractor's responsibility. Submit certified copies of laboratory test reports on analysis of existing concrete composition and new concrete mixtures, including all test data, for aggregate, admixtures, and curing compound. Perform these tests using an approved commercial laboratory or by a laboratory maintained by the manufacturers of the materials.

Existing Concrete Testing
Take representative samples of existing concrete from areas of the structure to be repaired at indicated locations in accordance with ASTM C42/C42M and ASTM C823/C823M and tested in accordance with ASTM C39/C39M, ASTM C42/C42M, ASTM C295/C295M, ASTM C457/C457M, ASTM C856, ASTM C1218/C1218M, and] [ASTM C642] [ASTM C114 [and ASTM C1084]. Evaluate aggregates in the existing concrete in accordance with ASTM C136 and ASTM C295/C295M. The air content of the existing concrete shall be determined in accordance with ASTM C457/C457M and ASTM C642.

Acceptance of Cement
Test cement for repair concrete and mortars as prescribed in the referenced specification under which it is furnished. Cement may be accepted on the basis of mill tests and the manufacturer's certification of compliance with the specification. The mill test reports and certification of compliance shall clearly reference the applicable ASTM documents and present the test result data. Cement shall conform to the specified requirements, and where the cement consists of a blend of cement and pozzolan, the pozzolan shall conform to the specified requirements for pozzolan, and the blend of cement and pozzolan shall conform to ASTM C1107/C1107M and all other specified requirements.

Aggregate
Take aggregate samples for repair concrete and mortars for laboratory testing in conformance with ASTM D75/D75M and test them in accordance with ASTM C33/C33M, ASTM C136, and ASTM C295/C295M.

Epoxy-Resin Grout
Test epoxy-resin grout for conformance with ASTM C881/C881M.

Concrete Mixture
The concrete mixture shall match that of the existing concrete to be repaired unless otherwise directed and shall be designed in accordance with [ACI 211.1] [ACI 211.2]. The mixture proportions shall include consideration of the finishes required.

Formwork Design
Formwork design shall conform to ACI 301MACI 301 and ACI 347.

Technical Service for Specialized Concrete
Obtain the service of a technical representative to oversee proportioning, batching, mixing, placing, consolidating, and finishing of concrete and mortar, until field controls indicate specialized concrete of specified quality is furnished.

SUBMITTALS
SUBMITTAL PROCEDURES:
 * SD-02 Shop Drawings
 * Detail Drawings
 * SD-03 Product Data
 * Proportions of Mixtures
 * Qualifications
 * SD-04 Samples
 * Materials
 * SD-06 Test Reports
 * Sampling and Laboratory Testing of Materials
 * SD-07 Certificates
 * Materials

QUALITY ASSURANCE
Provide qualifications of workers trained and experienced in restoration of concrete in historic structures for at least 5 consecutive years. Provide a list of similar jobs identifying when, where, and for whom the work was done. Submit a certified statement attesting that the experience and qualification of the workers (journeymen) comply with the specifications.

Sample Panels
Submit for approval sample panels of each mixture proposed for use in the work. No concrete of mortar shall be used in the work until the samples and the represented mixture has been approved. Materials proposed for use in producing concrete and mortar shall not be brought on to Government property until the samples and mixtures have been approved. Evaluate samples for each side of the structure, both close up and at a distance, under both wet and dry conditions. Each patch location and each side of the structure may require a separate or different mixture.

Detail Drawings
Submit detail drawings conforming to ACI SP-66 and ACI 318MACI 318 and showing location of architectural concrete elements in the work, building elevations, formwork fabrication details, reinforcements, embedments, dimensions, concrete strength, interface with adjacent materials, and special placing instructions, in sufficient detail to cover fabrication, placement, stripping, and finishing.

DELIVERY, STORAGE, AND HANDLING
Deliver cement in suitable bags used for packaging cements. Labeling of packages shall clearly define contents, manufacturer, batch identification, etc. Store cement and pozzolan in weathertight buildings, bins, or silos which will exclude moisture and contaminants. Arrange aggregate stockpiles and use them in a manner to avoid excessive segregation and to prevent contamination with other materials or with other sizes of aggregates. Reinforcing bars and accessories shall be stored in such a manner as to avoid contamination and deterioration. Admixtures which have been in storage at the project site for longer than six months or which have been subjected to freezing shall not be used unless retested and proven to meet the specified requirements. Store epoxy in accordance with the manufacturer's recommendations.

ENVIRONMENTAL REQUIREMENTS
Concrete, mortar, and epoxy adhesives shall not be placed when weather conditions detrimentally affect the quality of the finished product. No concrete or mortar shall be placed when the air temperature is below 5 degrees C 40 degrees F in the shade. When air temperature is likely to exceed 35 degrees C 90 degrees F, concrete and mortar shall have a temperature not exceeding 35 degrees C 90 degrees F when deposited, and the surface of the placed concrete shall be kept damp with a water fog until the approved curing medium is applied. Materials proposed for use in the work shall not be produced and placed during periods of rain or other precipitation. Stop material placements and protect all in-place material from exposure during periods of rain or other precipitation.

=PRODUCTS=

MATERIALS
Materials, physical and chemical properties, and composition of new concrete shall match that of existing concrete to be repaired, unless samples and testing determine that existing mixtures and materials are faulty or non-performing. Submit a minimum of 3 sample specimens for each proposed mixture at least 14 days prior to any placements, in order to demonstrate range of variation of each mixture. Submit samples of cured concrete and mortar patching specimens for each mixture for comparison with the cleaned structure. Samples of concrete and mortar shall be approximately 305 by 305 mm 12 by 12 inches in plan dimension and 25 to 38 mm 1 to 1-1/2 inches thick. The samples shall clearly indicate the mixture represented by the specimen, and shall have been produced, placed, finished, textured, and cured in the same manner as proposed for use in the work. Check the samples for matches in color and shade, finish, texture, and surface defects. Compare the samples to that part of the structure on which the mixture is proposed to be used. The samples shall be compared to the thoroughly cleaned structure. The samples and structure surfaces shall be clean and completely dry during the comparison. Following the comparison to dry surfaces, dampen the sample and structure with clean, potable water and compare the surfaces for acceptability to the Contracting Officer. Submit certificates of compliance attesting that the materials meet specification requirements.

Admixtures
Air entraining admixtures shall conform to ASTM C260/C260M, water-reducing or -retarding admixtures shall conform to ASTM C494/C494M, and pigments for integrally colored concrete shall conform to ASTM C979/C979M and ASTM C1017/C1017M. Admixtures shall not contain added chlorides.

Aggregates
Aggregates shall match existing aggregates as determined by samples and testing and shall otherwise conform to ASTM C33/C33M.

Bonding Agents
Bonding agents for use in bonding concrete and mortar patching materials to concrete and steel are specifically prohibited for use in the work.

Cementitious Materials
Provide cementitious materials of one type and from one source when used in concrete which will have surfaces exposed in the finished structure. Cementitious materials shall conform to one of the following:

Cement
Cement composition shall match that of cement used in existing concrete to be repaired as determined by samples and testing and shall conform to the basic requirements of ASTM C150/C150M, Type [I] [II], [low alkali]. Cement shall have non-shrink (shrinkage compensating) properties and shall conform to ASTM C1107/C1107M, Class B or C, expansive cement type.

Pozzolan
Pozzolan shall conform to ASTM C618, Class C or F, including low alkali [multiple factor,] [drying shrinkage,] [uniformity,] [and [moderate] [severe] sulfate resistance requirements] of "Table 2A - Supplementary Optional Physical Requirements." Requirements for maximum alkalis shall apply when used with aggregates listed to require low-alkali cement.

Epoxy Anchor Adhesives
Use an epoxy-resin grout to bond steel anchors to concrete, with a 100 percent solids, moisture insensitive, low creep, structural adhesive. The epoxy shall conform to ASTM C881/C881M, type IV; grade and class selected to conform to the manufacturer's recommendations for the application. The epoxy adhesive shall be conditioned, proportioned, mixed, and applied in accordance with the manufacturer's recommendations, except as otherwise specified herein or indicated on the drawings.

Reinforcing Steel
Reinforcing steel shall conform to ASTM A36/A36M, sizes as indicated, unless otherwise directed.

Tie Wire
Tie wire shall be soft Monel Metal or 18-8 stainless steel.

Metal attachments
Anchors for spall repairs shall be threaded stainless steel, size as indicated. Other plates, angles, anchors, and embedments shall conform to ASTM A36/A36M, and shall be prime painted with inorganic zinc primer.

Formwork
Formwork for special effects shall be as indicated or directed, and shall be subject to specific approval.

Form-Release Agents
Form-release agents shall be the manufacturer's standard, nonstaining, nonpetroleum based, compatible with surface finish and subsequent surface treatments.

Cleaning Solution
The cleaning solution shall consist of a 1:1 to 1:1.5 (water: liquid chlorine bleach) mixture of clean potable water and liquid chlorine bleach. Rinse water shall be clean potable water.

Water
Water used in cleaning concrete surfaces, used in producing concrete and mortars, and used for curing concrete shall be potable.

Burlap
AASHTO M 182.

Impervious Sheets
ASTM C171, type optional, except that polyethylene film, if used, shall be white opaque.

Membrane-Forming Compounds
COE CRD-C 300, non-pigmented, containing a fugitive dye.

Joint Sealing
Provide joint sealing as specified in Section 07 92 00 JOINT SEALANTS.

Epoxy-Resin Grout
Epoxy-resin grout shall be a two-component material, 100 percent solids by weight, formulated to meet the requirements of ASTM C881/C881M, Type I or II. Type I material shall be used when materials or atmospheric temperatures are 20 degrees C 70 degrees F or above. Use Type II material when materials or atmospheric temperatures are below 20 degrees C 70 degrees F. Epoxy-resin grout shall have the ability to structurally rebond cracks, delaminations, and hollow plane conditions in concrete; shall be insensitive to the presence of water; and shall have the capability to penetrate cracks down to 0.12 mm 5 mils in width. Materials shall have been used in similar conditions for a period of at least five years.

Epoxy Injection Ports
Design injection ports for epoxy-resin grout for the intended use as detailed in this section, made according to the recommendation of the epoxy manufacturer.

EQUIPMENT
Assemble equipment, that is dependable and adequate to accomplish the specified work, at the work site in sufficient time before the start of the work to permit thorough inspection, calibration of weighing and measuring devices, adjustment of parts, and the making of any repairs that may be required. Maintain the equipment in acceptable working condition during the life of the project.

Cleaning
Equipment used in cleaning shall not cause staining, erosion, marring, or other damage or changes in the appearance of the surfaces to be cleaned.

Sandblasting
Sandblasting equipment shall not be used in cleaning concrete and other building surfaces; and shall be subject to approval for each other specific applications. Sandblasting equipment permitted for use in cleaning reinforcement and other embedded metal items shall include an air compressor, hose, and long-wearing venturi-type nozzle of proper size, shape and opening. The maximum nozzle opening shall not exceed 6.3 mm 1/4 inch. Provide a portable air compressor capable of furnishing not less than 4.2 cubic meters 150 cubic feet per minute and maintaining a line pressure of not less than 0.620 MPa 90 psi at the nozzle while in use. The compressor shall be equipped with traps that will maintain the compressed air free of oil and water. The nozzle shall have an adjustable guide that will hold the nozzle aligned with the reinforcement and other items to be cleaned, and will maintain the nozzle approximately 25 mm 1 inch above the surface. Adjust the height, angle of inclination and the size of the nozzle as necessary to provide satisfactory results. Provide protective covers and barriers as required to prevent over-spray onto adjacent surfaces.

Water Blasting
Water blasting equipment shall include a trailer-mounted water tank, pumps, high-pressure hose, wand with safety release cutoff control, nozzle, and auxiliary water re-supply equipment. The equipment shall not be operated at a pressure which will cause etching or other damage to the concrete surface, except for the surfaces of the interior of the excavation, where operation at higher pressures may be used, subject to specific approval. Operate the equipment at a discharge capacity of 0.38 MPa 55 psi maximum and 9.5 to 11.4 L/minute 2.5 to 3 gpm for general surface cleaning operations of the structure, and between 3.5 and 7 MPa 500 and 1000 psi and 9.5 to 11.4 L/minute 2.5 to 3 gpm for cleaning of drill holes and surfaces of excavations. The water tank and auxiliary re-supply equipment shall be of sufficient capacity to permit continuous operations. Provide protective covers and barriers as required to prevent over-spray onto adjacent surfaces.

Excavation
The equipment used to excavate concrete shall be handheld manual or power type with a low-impact energy output and shall have gad points. The use of chisel points is prohibited. Surface grinders for use in preparing concrete and metal surfaces shall be small, hand-held equipment with a slow to moderate operating RPM, using stone grinding wheels. Saw cutting equipment shall use circular diamond blades. The blade shall be at least 3.2 mm 1/8 inch thick, with blade diameter selected as appropriate for the application. Excavation equipment shall be subject to approval.

Drilling
Equipment used to drill holes in concrete for patch anchors and other applications shall be standard handheld masonry drills, commonly used for drilling small holes in concrete and masonry. The drill shall be a small, powered, handheld type, using rotary drilling mode only. Impact and rotary impact type drills are prohibited.

Finishing and Texturing
Provide hand tools used for placing, finishing and texturing concrete and mortar which are commercially available and commonly used in concrete construction and repair. Equipment used for finishing and texturing concrete and mortar surfaces shall be a type commonly used in the concrete construction and repair industry for that application. Surface grinders, impact tools, and other equipment shall conform to the requirements specified herein, except as specifically required by the type of finish and texture, and subject to approval.

Compressed Air Supplies
Compressed air shall provide clean, oil and moisture free compressed air at the surface to be cleaned. The compressed air line shall have at least two in-line air filters to remove oil and moisture from the air supply. The compressed air supply shall be tested during each shift for the presence of oil and moisture.

Mixing, Transporting, and Placing
Equipment used for mixing, transporting, placing, and confining concrete and mortar placements shall be suitable for the intended purpose and be capable of satisfactorily mixing material, and supporting placement operations in an uninterrupted manner. Maintain equipment in a clean, good operable condition at all times. Equipment used in the work shall be subject to approval. Defects, and deficiencies in operation or capacity shall be resolved prior to use in the work. Equipment used for batching, mixing, conveying, and placing of materials shall be clean, free of old materials and contaminants, and shall conform to the manufacturer's recommendations.

Associated Equipment
Provide associated equipment such as mixer timing equipment, valves, pressure gauges, pressure hoses, other hardware, and tools as required to ensure a continuous supply of material and operation control. Use mechanical or radio communication systems between elements of mortar production and placement operation which are more than 30 m 100 feet apart.

=EXECUTION=

EVALUATION AND ANALYSIS
Use evaluation and analysis conforming to the requirements specified herein, and in Section 01 45 00.00 10 QUALITY CONTROL.

Existing Concrete
Concrete renovation shall be undertaken only after a complete evaluation and analysis of the areas to be repaired is completed, including sampling and testing of the existing concrete to determine its composition and qualities. A condition survey of the area to be repaired shall conform to ACI 201.1R and ACI 364.1R. Strength evaluation shall be in accordance with ACI 437R. Cracks shall be evaluated in accordance with ACI 224.1R. Examination and sampling procedures shall conform to ASTM C823/C823M.

Frequency of Testing
Take samples for strength, slump, air content, and shrinkage tests of each concrete mixture placed each day not less than once a day, and at least once for each 0.33 cubic meters 10 cubic feet of concrete; nor less than once for each 50 square meters 500 square feet of surface area for slabs or walls. Take samples for strength, slump, air content, and shrinkage tests of each mortar mixture placed each day not less than once a day, and at least for each 0.25 cubic meters 9 cubic feet of mortar. If this sampling frequency results in less than 3 strength tests for a given class of concrete or individual mixture design, tests shall be made from at least 3 randomly selected trucks (or batches) or from each truck (or batch) if fewer than 3 truck loads (or batches) are used. Field cured specimens for determining form-removal time or when a structure may be put in service shall be made in numbers directed to check the adequacy of curing and protection of concrete in the structure. The specimens shall be removed from the molds at the age of 24 hours and shall be cured and protected, insofar as practicable, in the same manner as that given to the portion of the structure the samples represent.

Testing Procedures
Strength test specimens for acceptance tests shall be molded and cured in accordance with ASTM C31/C31M. Strength test specimens and testing for mortar shall conform to ASTM C109/C109M. Cylinders shall be tested in accordance with ASTM C39/C39M and beams shall be tested in accordance with ASTM C78/C78M. A strength test shall be the average of the strengths of two specimens made from the same sample of concrete and tested at 28 days or at another specified test age. Tests for total air content and slump shall be made on fresh samples of the concrete and mortar. Perform tests onsite, on samples taken at the location of placement. Determine slump in accordance with ASTM C143/C143M. Determine air content in accordance with ASTM C231/C231M. Determine testing for shrinkage in accordance with ASTM C1107/C1107M.

Evaluation of Results
Concrete and mortar shall have a compressive strength at 28 days as determined by ASTM C39/C39M and ASTM C109/C109M respectively, which matches the present compressive strength of concrete in the structure within a tolerance of from -0 to +3.5 MPa -0 to +500 psi. Concrete and mortar strengths will be considered satisfactory if the averages of all sets of three consecutive strength test results equal or exceed the specified strength and no individual strength test result falls below the required strength. For flexural strength concrete, the strength level of the concrete will be considered satisfactory if the averages of all sets of five consecutive strength test results equal or exceed the required flexural strength, and not more than 20 percent of the strength test results fall below the required strength by more than 0.35 MPa 50 psi. The required minimum strength shall be the strength determined from testing of samples taken from the structure.

Investigation of Low-Strength Test Results
When any strength test of standard-cured test specimen falls below the specified strength requirement by more than 3.5 MPa 500 psi, or if tests of field-cured specimens indicate deficiencies in protection and curing, steps shall be taken to ensure that load-carrying capacity of the structure is not jeopardized. Nondestructive testing in accordance with ASTM C597, ASTM C803/C803M, or ASTM C805/C805M may be permitted by the Contracting Officer to determine the relative strengths at various locations in the structure as an aid in evaluating concrete strength in place or for selecting areas to be cored. Such tests, unless properly calibrated and correlated with other test data, shall not be used as a basis for acceptance or rejection. When strength of concrete in place is considered potentially deficient, obtain cores and test them in accordance with ASTM C42/C42M. Take at least three representative cores from each member or area of concrete in place that is considered potentially deficient. The location of cores will be determined by the Contracting Officer to least impair the strength of the structure. If the concrete in the structure is dry under service conditions, the cores shall be air-dried (temperature 16 to 27 degrees C 60 to 80 degrees F, relative humidity less than 60 percent) for seven days before testing and shall be tested dry. If the concrete in the structure is more than superficially wet under service conditions, the cores shall be tested after moisture conditioning in accordance with ASTM C42/C42M. Concrete in the area represented by the core testing will be considered adequate if the average strength of the cores is equal to or at least 85 percent of the specified strength requirement and if no single core is less than 75 percent of the specified strength requirement. If the core tests are inconclusive or impractical to obtain, or if structural analysis does not confirm the safety of the structure, load tests may be directed by the Contracting Officer in accordance with the requirements of ACI 318MACI 318. Concrete work evaluated by structural analysis or by results of a load test and found deficient shall be corrected in a manner satisfactory to the Contracting Officer. All investigations, testing, load tests, and correction of deficiencies shall be performed, and approved by the Contracting Officer, at the expense of the Contractor.

Initial Surface Cleaning
The cleaning materials, equipment, and methods shall not result in staining, erosion, marring, or other damage to the surfaces of the structure. Demonstrate the materials, equipment, and methods proposed for use in cleaning in a 1 by 1 m 3 by 3 foot square test section. The location of the test section, and the completed test section shall be subject to approval. The cleaning process shall be adjusted as required and the test section rerun until an acceptable process is obtained. Following an initial inspection and evaluation of the structure and surfaces, give the structure an initial surface cleaning to be completed prior to start of excavation, and sampling and testing for mixtures. The initial cleaning shall provide for the complete cleaning of all exterior concrete surfaces of the structures. The initial cleaning shall thoroughly clean the concrete surface to remove all traces of moss, dirt, and other contaminants. The cleaning shall provide a clean concrete surface to allow determination of the concrete's color and shades, finish and texture, and other properties. The "initial cleaning" shall consist of initial surface washing, followed by treatment with the cleaning solution, and then followed by a final water rinse. The initial surface washing shall consist of washing the surface with clean, low pressure water (pressure of less than 0.38 MPa 55 psi and 9.5 to 11.4 L/minute 2.5 to 3 gpm discharge) and manual surface scrubbing using handheld natural or plastic bristle brushes, followed by a clean water rinse. Following completion of the initial surface washing of the entire structure (or side of structure) dry the concrete prior to application of the cleaning solution. The concrete surfaces of the structure shall be coated with the cleaning solution at an application rate of 3.8 L 1 gal of solution per 1 to 3 square meters 10 to 30 square feet of treated surface using low pressure spraying equipment. Adjust the application rate of the solution as directed to ensure that the entire surface has been thoroughly wetted with the solution. Use a manual surface scrubbing with handheld natural or plastic bristle brushes on heavily soiled areas. Following treatment with the cleaning solution, rinse the treated surfaces with clean, low-pressure water. Water and all liquid materials used in the work shall be contained at the building perimeter and collected and disposed of in an approved manner.

Areas to be Removed
Remove unsound, weak, or damaged concrete. Loose particles, laitance, spalling, cracked, or debonded concrete and foreign materials shall be removed with hand tools unless otherwise noted. Protect surfaces of the structure, and surfaces adjacent to the excavation from damage which may result from excavation, cleaning, and patching operations.

Exposed Reinforcement
Remove concrete from around exposed or deteriorated reinforcing steel. Steel shall stand free of concrete at least 25 mm 1 inch minimum to provide mechanical bond with patch material.

Excavation in Concrete
Excavate deteriorated areas indicated to be repaired to sound concrete. The use of concrete and masonry saws for outlining the excavation shall not be allowed. Accomplish the excavation by means of manual methods and low-energy, handheld equipment. The sides of the excavation shall be approximately perpendicular to the exposed surface, dovetailed back 15 degrees from perpendicular to the exposed surface at the bottom in order to key in the patch. The bottom (or back) of the excavation shall be approximately parallel with the exposed surface of the patch. The surfaces of the excavation shall be finished to remove excessive variations and roughness and shall be shaped to provide a patch with uniform dimensions. Feathering at edges is not permitted. The excavation shall be accomplished to minimize the appearance of bond lines between the patch and the adjacent concrete and other abutting surfaces. Protect surfaces of the structure and surfaces adjacent to the excavation from damage which may result from excavation operations.

Cleaning of Excavations
Clean the surfaces of the excavation by water blasting and manual scrubbing methods. Sandblasting shall not be used to clean concrete surfaces. The surfaces of excavations shall be cleaned of dust, dirt, laitance, corrosion, or other contamination. Cracks and voids shall be flushed out with clean water and allowed to dry. Concrete surfaces to be in contact with the freshly placed concrete shall be maintained in a continuously damp condition for at least 24 hours prior to concrete placement. Immediately before placement, areas to be patched shall be cleaned and rinsed, followed by blowing dry with filtered, dry, compressed air to remove excess water, and to provide a surface in a saturated, surface-dry, damp condition. Protect surfaces of the structure and surfaces adjacent to the excavation from damage which may result from cleaning operations.

Previously Repaired Cracks
Remove old caulking or grout from previously repaired cracks where it is failing. Remove loose particles from cracks. Cracks shall be cleaned, rinsed with water followed by blowing with filtered, dry, compressed air.

Cleaning
Exposed reinforcing steel shall be mechanically cleaned to bare metal. Paint exposed steel in areas to be patched with two coats of zinc-rich primer paint.

Repairing
Notify the Contracting Officer of any steel members which have significant loss in cross-sectional area due to corrosion, cutting, or other damage. Damaged portions shall be mechanically cut away. Install reinforcing steel to match existing, where existing reinforcing is badly corroded or damaged. Lap splices shall be as required by code. If necessary, fasten bars with tie wires.

FORMWORK ERECTION
Erect formwork in accordance with the detail drawings to ensure that the finished concrete members conform accurately to the indicated dimensions, lines, elevations, and finishes. Deflection shall not exceed 1/360th of each component span or distance between adjacent supports. Deflections and tolerance shall not be cumulative. Install form liners as necessary to provide the required finish. Forms shall be coated with form release agents before reinforcement is placed.

General Requisites
Accomplish repairs in accordance with ACI C-10, ACI C-20, ACI 301MACI 301, and ACI 304R. Repair cracks, if required, in accordance with ACI 224.1R. Detailing shall be in accordance with ACI SP-66. Repaired surfaces shall match adjacent existing surfaces in all respects. Provide formwork, as necessary to reconstruct concrete to match adjacent surfaces. Voids shall be filled flush with adjacent surfaces. Use all products in accordance with the manufacturer's instructions.

Spalls
Spalls less than 25 mm 1 inch deep, where indicated to be repaired, shall be drypacked with an approved patching mortar. Spalls greater than 25 mm 1 inch deep shall be excavated and patched with concrete.

Patch Anchors
Surface areas to be patched, which do not have reinforcement or other metal embedments to be placed in the patching concrete and mortar, shall be provided with patch anchors to ensure that the patch is tied to the existing concrete structure. Provide patch anchors within the excavation at a frequency of at least one patch anchor per 0.10 square meter square foot of patch plan surface area; specific locations for patch anchors shall be as indicated. Use small handheld, low-speed rotary masonry drills to produce holes in the existing concrete, within the limits of the excavations for the patch anchor installation.

Holes
Drill holes into the existing concrete substrate material of the excavation using rotary (non-hammer) drills. Holes shall have a diameter 3.2 mm 1/8 inch larger than the anchor diameter. The holes shall be drilled to a depth of 100 mm 4 inch, except as otherwise indicated or directed. Drill holes shall be produced to ensure that the holes do not penetrate completely through the concrete, and will provide at least 25 mm 1 inch of cover around the drill hole. Holes shall be cleaned by water blasting to remove drill dust and other debris and then blown dry with filtered, dry, compressed air. Drill holes shall be conditioned in accordance with the epoxy adhesive manufacturer's recommendations.

Anchor Installation
Clean anchors to remove all contaminants which may hinder epoxy bond. Epoxy adhesive shall be pressure injected into the back of the drilled holes. The epoxy shall fill the holes so that when the anchors are inserted, the epoxy completely fills the holes and excess epoxy is not exuded from the holes. Insert anchors immediately into the holes. The anchors shall be set back from the exterior face at least 25 mm 1 inch. Install anchors without breaking or chipping the exposed concrete surface.

Cleanup
Remove excess epoxy and spills from the surface of the excavation, leaving it in a clean and uncontaminated condition. Spills on adjacent surfaces shall also be removed and surfaces repaired as required.

Mixing Epoxy-Resin Grout Components
Mix epoxy-resin grout components in the proportions recommended by the manufacturer. The components shall be conditioned from 20 to 30 degrees C 70 to 85 degrees F for 48 hours prior to mixing. Mix the two epoxy components with a power-driven, explosion-proof stirring device in a metal or polyethylene container having a hemispherical bottom. The polysulfide curing agent component shall be added gradually to the epoxy-resin component with constant stirring until a uniform mixture is obtained. The rate of stirring shall be such that the entrained air is at a minimum.

Tools and Equipment
Tools and equipment used further in the work shall be thoroughly cleaned before the epoxy-resin grout sets.

Health and Safety Precautions
Provide full-face shields for all mixing, blending, and placing operations as required and protective coveralls and neoprene-coated gloves for all workers engaged in the operations. Supply protective creams of a suitable nature for the operation. Maintain adequate fire protection at all mixing and placing operations. Smoking or the use of spark- or flame-producing devices shall be prohibited within 15 m 50 feet of mixing and placing operations. The mixing, placing, or storage of epoxy-resin grout or solvent shall be prohibited within 15 m 50 feet of any vehicle, equipment, aircraft, or machinery that could be damaged from fire or could ignite vapors from the material.

Epoxy Pressure-Injection of Cracks
Cracks shall be pressure-injected using a two component epoxy system with an in-line mixing and metering capability. System shall be capable of injection pressures up to a maximum of 1 MPa 150 psi to ensure complete penetration of the crack. Apply an adequate surface seal to the crack or joint to prevent the escape of epoxy. Entry points shall be established along the crack. Fill the crack with a 100 percent solid epoxy adhesive. Inject the adhesive into the crack at the first entry point with sufficient pressure to advance the epoxy to the next adjacent port. The original port shall be sealed and injection moved to the port at which the epoxy appears. Continue the process until each joint and crack has been injected for its entire length. Epoxy shall be allowed to cure in accordance with manufacturer's instructions. Sealing materials shall then be removed and surface finished to match adjacent existing surface.

Application of Concrete and Patching Mortar
Place concrete and mortar to rebuild spalled or damaged areas to match the original surface finish, level, texture, and color. Concrete shall be cured as specified herein. The finished appearance of the patch shall match the adjacent existing surface.

CURING AND PROTECTION
Use an approved method for curing concrete and mortar patching for at least 7 days. Immediately after placement, protect concrete from premature drying, extremes in temperatures, rapid temperature change, mechanical injury and injury from rain and flowing water. Maintain air and forms in contact with concrete and mortar at a temperature above 10 degrees C 50 degrees F for the first 3 days and at a temperature above 0 degrees C 32 degrees F for the remainder of the specified curing period. Materials and equipment needed for adequate curing and protection shall be available and at the placement site prior to placing concrete and mortar. No fire or excessive heat shall be permitted near or in direct contact with the concrete and mortar at any time. Accomplish curing by any of the following methods, or combination thereof, as approved:

Moist Curing
Maintain concrete and mortar to be moist-cured continuously wet for the entire curing period. If water or curing materials stain or discolor concrete and mortar surfaces which are to be permanently exposed, the concrete and mortar surfaces shall be cleaned. When wooden forms are left in place during curing, they shall be kept wet at all times. If the forms are removed before the end of the curing period, curing shall be carried out as on unformed surfaces, using suitable materials. Horizontal surfaces shall be cured by ponding, by covering with a 50 mm 2 inch minimum thickness of continuously saturated sand, or by covering with waterproof paper, polyethylene sheet, polyethylene coated burlap, or saturated burlap.

Membrane Curing
Membrane curing shall not be used on surfaces that are to receive any subsequent treatment depending on adhesion or bonding to the concrete; except that a styrene acrylate or chlorinated rubber compound meeting COE CRD-C 300 requirements may be used for surfaces which are to be painted or are to receive bituminous roofing or waterproofing, or for floors that are to receive adhesive applications of resilient flooring. Select a curing compound that is compatible with any subsequent paint, roofing, waterproofing, or flooring specified. Apply curing compound to formed surfaces immediately after the forms are removed and prior to any patching or other surface treatment except the cleaning of loose sand, mortar, and debris from the surface. Surfaces shall be thoroughly moistened with water, and the curing compound shall be applied to slab surfaces as soon as the bleeding water has disappeared, with the tops of joints being temporarily sealed to prevent entry of the compound and to prevent moisture loss during the curing period. Apply compound in a one-coat continuous operation by mechanical spraying equipment, at a uniform coverage of 20 square meters 200 square feet per 3.8 L gallon. Concrete surfaces which have been subjected to rainfall within 3 hours after curing compound has been applied shall be resprayed by the method and at the coverage specified. Keep surfaces coated with curing compound free of foot and vehicular traffic, and from other sources of abrasion and contamination during the curing period.

Epoxy Adhesives
Protect and cure epoxy adhesives in accordance with the manufacturer's recommendations. The adjacent surfaces and ambient conditions shall be maintained within the manufacturer's recommendations. The patch anchors and epoxy adhesive shall be protected from displacement and disturbances.

Matching Adjacent Concrete
Concrete and mortar finishes and color shall match the finish and color of the existing adjacent concrete. Accomplish finishing at the time of concrete placement or immediately after formwork removal.

Non-Standard Finish
The exposed surfaces of concrete and mortar patching shall match the finish, texture, and surface detail of the original surface. Mechanical finishing and texturing may be required to produce the required finish and appearance. The finishing and texturing shall be accomplished in such a way as to help conceal bond lines between the patch and adjacent surfaces. The texturing shall replicate all surface details, including tooling and machine marks. The equipment used in finishing and texturing shall be a low-impact energy type which will not weaken the patch or damage the patch bond and the adjacent concrete. Equipment used for finishing and texturing shall be demonstrated on sample panels of concrete and mortar to demonstrate performance and suitability of the equipment and methods. Equipment and methods shall be subject to approval.

FINAL CLEANING
No sooner than 72 hours after completion of the curing period and after joints are sealed, faces and other exposed surfaces of concrete shall be washed down with water applied with a soft bristle brush, then rinsed with clean water. Discolorations which cannot be removed by these procedures, will be considered defective work. Perform cleaning work when temperature and humidity conditions are such that surfaces dry rapidly. Protect adjacent surfaces from damage during cleaning operations.

PROTECTION OF WORK
Protect work against damage from subsequent operations.

DEFECTIVE WORK
Defective work shall be repaired or replaced, as directed, using approved procedures.

FINAL INSPECTION
Following completion of the work, inspect the structure for damage, staining, and other distresses. The patches shall be inspected for cracking, crazing, delamination, unsoundness, staining and other defects. Inspect the finish, texture, color and shade, and surface tolerances of the patches to verify that all requirements have been met. Repair all surfaces exhibiting defects, as directed.