CAST-IN-PLACE CONCRETE
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CAST-IN-PLACE CONCRETE
PART 1 - GENERAL
APPLICABLE PUBLICATIONS
The following publications of the issues listed below, but referred to elsewhere by basic designation only, form a part of this specification to the extent indicated by the references thereto.
QUALIFICATION OF TESTING LABORATORY
The testing laboratory must be an established commercial laboratory which is equipped and manned for testing cement, concrete, and masonry materials. The laboratory must be able to prove that it has been engaged in this type of testing during a period of not less than one year in order to be considered qualified and must be approved by the Contracting Officer.
SUBMITTALS
Manufacturer's Catalog Data
Printed Installation Instructions of the following:
a. Chemical Floor Hardener. Shop Drawings.
b. Reinforcing Steel
Submit shop drawings for reinforcing steel, prepared to indicate bending diagrams, assembly diagrams, splicing and laps of bars, shapes, dimensions and details of bar reinforcing and accessories and concrete cover. Do not use scaled dimensions from structural drawings to determine lengths of reinforcing rods. Shop drawings are defined as original drawings. Reproductions of contract drawings will not be accepted in lieu of shop drawings.
Design Data. Contractor Concrete Mix Design Submit for approval a mix design for each type of concrete, including a complete list of materials and the applicable reference specifications, and copies of test reports showing that the mix has been successfully used to produce concrete with the properties specified. Submittal shall clearly indicate where each mix design will be used when more than one mix design is submitted.
Test Reports. Concrete mix design
Submit copies of test reports showing that the mix has been successfully tested to produce concrete with the properties specified and that mix will be suitable for the job conditions. Test reports shall be submitted along with the concrete mix design. Obtain approval before concrete placement. Field Test Reports. Laboratory test reports as specified in the article entitled "Sampling and Testing."
Proofs of Compliance
The Contractor shall submit proofs of compliance as specified in the “General Paragraph” and as follows: Certificates of conformance for all materials, except materials requiring a laboratory test report. Mill certificates of tests on bar steel.
DELIVERY AND STORAGE OF MATERIALS (EXCEPT READY-MIX CONCRETE)
Packaged materials shall be delivered to the project site in their original, unopened package or container bearing label clearly identifying manufacturer's name, brand name, material, weight or volume and other pertinent information. Packaged materials shall be stored in their original, unbroken package or container in a weathertight and dry place, until ready for use in the work. Unpackaged aggregates shall be stored in a manner to avoid excessive segregation or contamination with other materials or with other sizes of like aggregate, and to protect from freezing.
Reinforcement shall be stored in a manner that will avoid excessive rusting or coating with grease, oil, dirt, and other objectionable materials. Storage shall be in separate piles or racks so as to avoid confusion or loss of identification after bundles are broken. Concrete shall not be delivered until forms, reinforcement, and embedded items are in place and ready for concrete to be placed.
CONCRETE QUALITIES
General
Concrete will be in strict accordance with applicable portions of Law 1086 and D.M. 9 Jan.1996. The concrete shall have a 28-day compressive strength (Rck, Resistenza Caratteristica) as follows:
Type of Construction Rck (kg/cm2)
Lean concrete 200
Rigid Pavements including 250 sidewalks, curbs and equipment pads
Drainage and Sanitary Sewer 250 Appurtenances
Thrust blocks, Pipeline 300 Encasements
Foundations, Grade Beams and 300 Grade Walls
Floor Slabs on Grade 250
Columns, Beams Above Grade Slabs 350 and Walls
All other concrete 300
Maximum aggregate size shall be 30 millimeters, except 25 millimeters for walls and slabs on grade. The maximum water cement ratio, by weight, for all concrete with Rck of 350 kg/cm2 shall not exceed 0.40.
Concrete Consistency
Concrete consistency shall be such that no air bubbles nor paste reflow will occur when the pouring and setting operations are finished regardless of placing method used. Generally, the slump shall fall within the following limits, provided the required strength is obtained: Type of Structure Slump in cm for Vibrated Concrete Minimum Maximum General building construction and rigid pavements 5.0 7.5
Reinforced walls 5.0 10.0
Heavy-duty floor and slab
construction 5.0 7.5
Shimmy tests shall be made in accordance with UNI EN 206-1.
Admixtures
Calcium chloride shall not be used as an admixture. Air-Entrained Concrete. Provide for all concrete exposed to the weather. Air-entrainment shall be accomplished by using an air-entraining admixture, not air-entraining cement. If the entrained air content falls below the specified limit, an air-entraining admixture shall be added in sufficient quantity to bring the entrained air content within the specified limits. Air-entraining admixtures shall be added in solution in a portion of the mixing water by means of a mechanical batcher in a manner that will ensure uniform distribution of the agent throughout the batch.
The air content of freshly mixed air-entrained concrete shall be as follows:
Amount of air (percent Maximum aggregate size volume of concrete) 25 mm. 5 + 1
The percentage of air shall be determined by UNI EN 12350-7 on samples taken before placing of the concrete in the forms. Accelerating, Retarding and Water Reducing Admixtures Do not use unless prior approval is obtained from Contracting Officer.
READY-MIXED CONCRETE (UNI EN 206-1)
For ready-mixed concrete works, the mixing and transporting equipment and the method of placement shall be subject to approval. Ready-mixed concrete shall have a mixing time for mixers having capacities of 0.76 cu.m or less, not less than one minute. For mixers over 0.76 cu.m capacity, mixing time shall be increased 15 seconds for each additional 0.38 cu.m or fraction thereof of material mixed.
READY MIXED MORTAR (SHOTCONCRETE)
The mortar shall be a cement mortar ready to be placed, single component, containing microsilica. Mortar shall be dry applied, by means of a compressed air spray machine, on the interior face of Building No. 147 perimeter walls. Mortar shall be delivered to the site in factory sealed bags, bearing the manufacturer’s name, batch number and expiration date of the product.
PART 2 – MATERIALS
Materials shall conform to the requirements and reference documents listed.
CONCRETE
Contractor Furnished Mix Design
Concrete mix shall satisfy the requirements specified herein and indicated on the drawings. Materials shall conform to the requirements and reference documents listed.
CEMENT
Portland Cement. Portland type R-325 shall be the minimum used.
Storage
Immediately upon receipt at site of work, the cement shall be stored in a dry, weathertight, properly ventilated structure, with adequate provisions for prevention of absorption of moisture from both walls and floor.
Testing
Cement will be accepted on the basis of mill or laboratory tests and the manufacturer's or laboratory certification of compliance with above. When so directed by the Contracting Officer, the Contractor will furnish certificates of laboratory test reports of compliance to Contracting Officer for each mill lot of cement supplied from different mills in mixed shipment and for each separate shipment from the same mill, prior to using the cement in the work. Testing of the cement shall be the responsibility of the Contractor. Testing agency will be subject to approval of the Contracting Officer.
WATER
Water for mixing and curing, including free moisture and water in the aggregate, shall be fresh, clean and potable. Turbidity of the water shall not exceed 2,000 parts per million.
AGGREGATES
Aggregate shall conform to UNI 8520.
Fine Aggregates
Shall be free from clay, organic materials, water soluble alkali and free from substances which might cause expansion in the concrete from reaction with alkali in the cement. Sand shall be sharp, fine granular, composed of hard, strong, durable, uncoated particles. Grading shall conform to the following:
Total passing laboratory sleeves having sieve opening mm Percentage by weight
9.5 100
4.75 95-100
2.36 80-100
1.18 50-85
0.60 25-60
0.30 10-30
0.15 2-10
The fineness modulus of fine aggregate shall be not less than 2.40 or greater than 2.90. The fineness modulus shall be defined as the sum of the cumulative percentages retained on sieve sizes 4.75, 2.36, 1.18, 0.60, 0.30 and 0.15 divided by 100. Aggregate which shows a variation in fineness greater than 0.20 more or less than that of the representative sample submitted, will be rejected, unless, at the option of the Contracting Officer, it is accepted subject to such changes in the concrete proportions as may be directed, for which no change in the Contract price will be made.
Coarse Aggregate
It shall consist of crushed stone, or gravel, or subject to approval, other inert materials having similar characteristics. Grading of coarse aggregate shall be in accordance with UNI EN 206-1.
ADMIXTURES
Admixtures shall comply with UNI EN 934-2 and the following requirements. Air-entraining admixture for concrete shall conform to UNI EN 934-2.
REINFORCEMENT
Reinforcing bars 26 millimeters in diameter and smaller shall be high strength helically deformed bars conforming to UNI ENV 10080 and D.M. 9 Jan. 1996, designation FeB44K with a minimum yield strength of 430 N/mm2. Reinforcing bars 28 millimeters in diameter and larger shall be high strength factory designed helically deformed bars conforming to UNI 6407, designation FeB38 with a minimum yield strength of 3,800 kilograms per square centimeter.
Welded Wire Fabric
Welded wire fabric shall be electrowelded netting for concrete reinforcement, conforming to D.M. 9 Jan. 1996, and shall have the following minimum characteristics:
Yield Stress, fyk or 390 N/mm2
f (0.2)k
Breaking Stress, ftk 440 N/mm2
Ratio of Diameters of 0.60
Intersecting Wires Elongation, A10 8%
Minimum Ratio for ftk/fyk 1.10
Supports for Reinforcement
Supports for reinforcement shall include bolsters, chairs, spacers, and other devices suitable for proper spacing, supporting, and fastening reinforcing bars and welded wire fabric in place. The legs of supports in contact with formwork shall be hot-dip galvanized after fabrication, plastic coated, or corrosion-resisting chromium-nickel steel.
JOINT MATERIALS
Preformed Joint Filler Strips
Preformed joint filler strips shall be nonextruding and resilient bituminous type, approved by the Contracting Officer
Joint Sealing Compound
Joint sealing compound shall be cold-applied, mastic, single-or multiple component type sealing compound.
MATERIALS FOR CURING CONCRETE
Impervious Sheeting
Waterproof paper, polyethylene sheeting, or polyethylene coated burlap.
Liquid Membrane-Curing Compound
White-pigmented, free of paraffin or petroleum.
Liquid Chemical Compound
A suitable sealer-hardener designed for sealing and hardening in addition to curing of the concrete, applied by the method and at the rate recommended by the manufacturer. It shall not reduce the adhesion of tile, paint, roofing, waterproofing or other material to be applied to the concrete. The chemical compound shall be free of petroleum resins or waxes.
Waterproof Paper
It shall consist of two sheets of Kraft paper cemented together with bituminous material in which are embedded strands of fiber running in both directions.
Burlap
Commercial quality, two or more layers having a combined weight of 475 grams or more per square meter when clean and dry. Polyethylene-Coated Burlap shall be a laminate of burlap weighing not less than 400 grams per square meter and a white opaque polyethylene film, not less than 0.1 millimeters thick. The polyethylene film shall be permanently bonded to the burlap.
VAPOR BARRIER MATERIAL
Polyethylene sheeting of not less than nominal 0.20 millimeters thickness.
FLOOR FINISH MATERIALS
Liquid Chemical Floor Hardener
Liquid chemical floor hardener shall be a colorless aqueous solution containing a blend of magnesium fluorosilicate and zinc fluorosilicate combined with a wetting agent. The solution shall contain not less than 250 grams of fluorosilicates per liter. A proprietary chemical hardener of proven and satisfactory performance may be used provided the hardener is delivered to the project site ready for use in the manufacturer's original containers.
Epoxy Floor Coating
Epoxy floor coating shall be a two component epoxy resin for the hardening impregnation of concrete. Coating shall be an amber colored transparent liquid with good capillarity action, capable of being applied with a brush or a roller.
FORMS
General
Provide forms for all concrete not indicated or specified otherwise. Set forms true to line and grade and maintain so as to insure completed work within the allowable tolerances specified, and make mortar-tight. The Contractor shall be responsible for the adequacy of forms and form supports. Construct forms so that they can be removed without damaging the concrete. All exposed joints, edges, and external corners of concrete shall be chamfered 15 millimeters unless otherwise shown. In excavations without forms, the dimensions of excavations in earth shall be not less than 6 centimeters outside of the concrete lines indicated.
Materials for Forms
Wood, plywood, steel, or other suitable material. Wood forms, for surfaces exposed to view in the finished structure, shall be boards or plywood. Boards shall be dressed to a uniform thickness, evenly matched, and free from loose knots, holes, and other defects. Plywood shall be concrete-form plywood with a minimum thickness of 15 millimeters. Surfaces of steel forms shall be free from irregularities, dents, and sags.
Design of Forms
Form facing materials shall be supported by structural members spaced sufficiently close to prevent deflection of the form facing material. Forms placed in successive units for continuous surfaces shall be fitted to accurate alignment to assure a smooth completed surface free from irregularities within the tolerances specified. Where necessary to maintain the tolerances specified, such as long spans where intermediate supports are not possible, the formwork shall be chamfered for anticipated deflections in the formwork due to the weight and pressure of the fresh concrete and due to construction loads.
Shores and struts shall be provided with a positive means of adjustment capable of taking up all formwork settlement during concrete placing operations. Adjustment shall be obtained with wedges or jacks, or a combination thereof. When adequate foundations for shores and struts cannot be secured, trussed supports shall be provided. Temporary openings shall be provided in wall forms, column forms, and at other points where necessary to permit inspection and to facilitate cleaning. Forms shall be readily removable without impact, shock or damage to the concrete.
Forms for Standard Smooth Form Finish
Form facing material for formed surfaces to have standard smooth finish as specified, shall be the specified overlaid concrete form plywood or other approved form facing material that is nonreactive with concrete and that will produce concrete surfaces equivalent in smoothness and appearance to that produced by new overlaid concrete form plywood panels.
The maximum deflection of the form facing material between supports, and the maximum deflection of form supports, such as studs and wales, shall not exceed 0.005 times the span. The arrangement of form facing sheets shall be orderly and symmetrical, and the sheets shall be in as large sizes as are practicable. Panels shall be arranged to make a symmetrical pattern of joints. All horizontal and vertical joints shall be solidly backed and butted tight to prevent leakage and fins.
Form Ties
Form ties shall be factory-fabricated, adjustable in length, removable or snap-off metal type of design that will not allow form deflection or will not spall concrete upon removal. The portion of the form ties remaining within the concrete after removal of the exterior parts shall be at least 4 centimeters back from the concrete surface. Form ties shall be free of devices that will leave a hole larger than 25 millimeters or less than 10 millimeters in diameter in the concrete surface. Form ties fabricated at the project site or wire ties of any type are not acceptable.
Coating
Before placing the concrete, coat the contact surfaces of forms with a non-staining mineral oil, non-staining form coating compound or two coats of nitro-cellulose lacquer. Mineral oil shall not be used on forms for surfaces to be painted.
Tolerances and Variations
Set and maintain concrete forms to ensure that after removal of the forms no portion of the concrete work will exceed any of the tolerances. Variations from the plumb. a In the lines and surfaces of piers, walls, and in arises
In any 3.0 m of length.......... 6 mm
Maximum for entire length....... 25 mm
b. For exposed control-joint grooves and other conspicuous lines
In any 6.0 m of length.......... 6 mm
Maximum for entire length....... 12 mm
Variation from the level or from the grades indicated on the drawings.
a. In slab soffits, ceilings, beam soffits, and arises
In any 3.0 m of length......... 6 mm
In any bay or in any 6.0 m of length......................... 10 mm
Maximum for entire length...... 20 mm
b. In exposed lintels, sills, parapets, horizontal grooves, and other conspicuous lines
In any bay or in any 6.0 m of length......................... 6 mm
Maximum for entire length...... 16 mm
Variations of distance between walls, columns and beams. 6 mm per 3.0 m of distance, but not more than 12 mm in any one bay, and not more than 25 mm total variation. Variation of linear building lines from established position in plan............................... 25 mm
Variation in the sizes and locations of sleeves, floor openings, and wall openings.
Minus.............................. 6 mm
Plus............................... 15 mm
Variation in cross-sectional dimensions of piers, columns and beams and in the thickness of slabs, pavements, and walls.
Minus.............................. 6 mm
Plus............................... 15 mm
Footings.
a. Variation in dimensions in plan
Minus............................ 15 mm
Plus............................. 50 mm
when formed, or plus 75 mm when placed against unformed excavation
b. Misplacement or eccentricity 2 percent of the footing width in the direction of misplacement but not more than.................... 50 mm
c. Reduction in thickness.
Minus............................ 5 percent of specified thickness
Variation in steps.
a. In a flight of stairs
Rise............................. 3 mm.
Tread............................ 6 mm.
b. In consecutive steps
Rise............................. 2 mm.
Tread............................ 3 mm.
GROUT
Grout shall be non-shrink, Portland cement grout with a minimum compressive strength of 25 mPa (Rck cube) and 20 mPa (fck cylinder).
REINFORCED READY MIXED MORTAR
MORTAR
Mortar shall have the following technical characteristics::
- Color: Gray
- Granulometry: 0-2,5 mm
- Specific gravity: 2,200 ± 0,10 kg/l (mixed product)
- Resistances: 28 days
- Compressive strength >40 N/mm2
- Resistance to bending stress >70 kg/cm2
- Adhesion at 28 days: ≥15 kg/cm2 direct traction on concrete plate
- Elastic module (static): ≥ 250.000 kg/cm2.
STEEL REINFORCEMENT MESH
Ready mixed mortar shall be reinforced with 10 millimeter diameter, 15x15 centimeter Feb44K steel wire mesh. Mesh shall be anchored to the wall to be coated by steel nails.
PART 3 – EXECUTION
The work shall conform to Law 1086 and D.M. 9 Jan. 1996.
PLACING REINFORCEMENT AND MISCELLANEOUS MATERIALS
General
Contractor will coordinate the work of all trades to insure that all embedded items such as anchors, pipe sleeves, reglets, conduits, electrical outlet boxes, etc., are properly installed to serve intended functions and, at the same time, are so located that they will not unduly weaken the strength of any structural member. Suitable templates or instructions, or both, will be provided for setting items not placed in the forms.
Where conflicts occur between the location of reinforcing and embedded items, the Contracting Officer shall be notified so that conflicts may be reconciled before placing concrete. Anchors and other embedded items shall be positioned and supported with appropriate accessories. Embedded items shall have been inspected and approved before concrete is placed.
Placing Reinforcement
Shall be in strict accordance with applicable portions of Law 1086 and the following: General Requirements. The Contractor shall furnish and place all reinforcement bars, stirrups, hanger bars, wire fabric, spirals, and other reinforcing materials as indicated on the project drawings or required by the project specifications, together with all necessary wire ties, chairs, spacers, supports, and other devices necessary to install and secure the reinforcing properly.
All reinforcement shall, when placed, be free from rust, scale, grease, clay and other coatings and foreign substances that would reduce or destroy the bond. Reinforcement which has bends not shown on the project drawings or on approved shop drawings or which is reduced in section by rusting shall not be used. Bending. Bars shall be bent as indicated on the contract drawings. Generally this operation can be cold, or hot if action is taken for not reaching temperatures greater than 800-830 degrees Centigrade (cherry red color). Hot bar bending shall not be authorized for cold drawn or cold rolled bars or for heat-treated bars.
Placing. Reinforcing shall be placed accurately and secured. It shall be supported by concrete or metal chairs, by metal spacers or by metal hangers. For slabs on grade (over earth or over capillary water barrier) and for footing reinforcement, bars or mesh shall be supported on precast concrete blocks, spaced at intervals required by size of reinforcement used, to keep reinforcement the minimum height specified above the underside of slab or footing.
For slabs other than on grade, supports for which any portion will be less than 2 centimeters from concrete surfaces that will be exposed to view or will be painted shall be of plastic-coated steel; or nonferrous metal that is not reactive with concrete. For beams, columns, and other structural members, all reinforcement shall be supported and secured together to prevent displacement by construction loads or by the placing of wet concrete, and as follows:
Supports for reinforcement shall be sufficient in number and sufficiently heavy to carry the reinforcement they support. No reinforcing bar shall be placed more than 8 centimeters beyond the last leg of any continuous bar support. Supports are not intended to, and shall not be used to, support runways for concrete conveying equipment and similar construction loads.
Welded wire fabric shall be supported as required for reinforcing bars. Reinforcement shall be secured to supports by means of tie wire. Wire shall be black, soft iron wire, not less than 1.2 millimeters in diameter. With the exception of temperature reinforcement, which shall be tied to main steel approximately 60 centimeters on center, reinforcement shall be accurately placed and securely tied at all intersections with 1.2 millimeters in diameter annealed wire and held in position during the placing of concrete by spacers, chairs, or other approved supports. Wire-tie ends shall point away from the form. Welding of crossing bars shall not be permitted for assembly of reinforcement unless specifically authorized by the Contracting Officer.
Splices in Reinforcement. No splices of reinforcement shall be made except as indicated on the drawings, splices shall comply with D.M. 9 Jan. 1996, or as specified, or as authorized by the Contracting Officer. Welded wire fabric reinforcement in slabs shall have joints lapped at least one full mesh plus 10 centimeters. Lapping of wire fabric sheets shall be staggered to avoid a continuous lap in either direction.
Concrete Protection for Reinforcement. Concrete protection for reinforcement shall be as indicated. For areas not specifically indicated, use the following:
a. Concrete deposited against the earth: 80 mm
b. Concrete deposited against forms and exposed to weather 40 mm
c. Concrete deposited against forms and not exposed to weather 20 mm
d. All other areas 25 mm
Tolerances and Variations. The minimum concrete cover for reinforcement specified in the contract documents takes precedence over all permissible reinforcement-placement variations; nothing in the variations listed below is to be construed as permitting violation or compromise thereof:
a. Height of bottom bars plus or minus 6 mm above form
b. Lengthwise positioning plus or minus 50 mm of bars
c. Spacing bars in walls plus or minus 25 mm and solid slabs
d. Spacing bars in joists, minus 0mm or plus 6 mm beams, and footings
e. Height of top bars minus 0mm or plus 6 mm
f. Stirrup spacing
(1)For any one stirrup plus or minus 25 mm
(2)For over-all group plus or minus 25 mm of stirrups
Installation of Anchorage Devices
General
All anchorage devices and other embedded items required for other work that is attached to, or supported by, cast-in-place concrete shall be set and built-in as part of the work of this section, using the setting drawings, instructions, and directions for the work to be attached thereto. Placing Anchorage Devices. Anchorage devices and other embedded items shall be positioned accurately and supported against displacement. Openings in anchorage devices, such as slots and threaded holes, shall be filled temporarily with an approved removable material to prevent the entry of cement paste into the openings.
CONSTRUCTION JOINTS
General
Construction joints not indicated on the drawings shall be made and located so as not to impair the strength and appearance of the structure, and shall be approved by the Contracting Officer. Construction joints, if required but not indicated, shall be located as follows: In walls, at midheight for horizontal joints, at maximum 6 meters on centers for vertical construction joints. In columns, piers, and walls at the top of footing; at the top of slabs on grade; and at the underside of the deepest beam or girder framing into column or pier.
In slabs and pavements on grade, so as to divide the slab or pavement into areas not in excess of 50 square meters. Keyways at least 4 centimeters deep shall be provided in all construction joints in walls and slabs and vertical construction joints in walls, approved bulkheads designed for the purpose may be used for slabs. Construction joints shall be perpendicular to the main reinforcement. All reinforcement shall be continued across construction joints, unless otherwise indicated.
Isolation Joints in Slabs and Pavements on Grade Isolation joints in slabs or pavement on grade shall be provided at all points of contact between slabs or pavement on grade and vertical surfaces, such as column pedestals, foundation walls, grade beams, and elsewhere as indicated, unless otherwise detailed. Isolation joints shall be filled with premolded joint filler strips, of thickness as shown on drawings and extending the full slab depth unless otherwise indicated.
Filler strips shall be installed at the proper level below the finish floor elevation with a slightly tapered, dressed-and-oiled wood strip temporarily secured to the top of the filler strip to form a groove not less than 15 millimeters in depth where the joint will be sealed with sealing compound, and not less than 5 millimeters in depth were joint sealing is not required. The wood strip shall be removed after the concrete has set. Clean groove of foreign matter and loose particles after the surface has dried.
Control Joints in Slabs and Pavement on Grade Control joints in slabs and pavement on grade shall be provided to form panels as indicated. Joints shall follow lines indicated on the drawings, and shall be straight and true. Under and on the exact line of each control joint 50 percent of the strands of the welded wire fabric reinforcement shall be cut before placing the concrete. Control joints shall be 5 millimeters wide by 1/5 to 1/4 of the slab depth, and shall be formed by inserting a premolded hardboard or fiberboard strip into the fresh concrete until the top surface of the strip is flush with the slab surface or formed in.
After the concrete has cured for at least 7 days, remove inserts and clean groove of foreign matter and loose particles. An appropriate manufactured plastic control joint former may be used as an option to the above. Control joints may also be made by saw cutting the slab. Joints shall be cut using a power saw with the appropriate masonry cutting blade. Cutting should be done as soon as possible after hardening, and shall be made within 24 hours of placing concrete. In slabs on grade provide joints so as to divide the slab into areas not to exceed 60 square meters.
Sealing Joints in Slabs or Pavement on Grade
Isolation and control joints in slabs or pavement on grade which will not be covered with finish flooring material shall be sealed with joint sealing compound after the concrete curing period. The groove shall be slightly underfilled with joint sealing compound to prevent extrusion of the compound. Any excess material shall be removed as soon after sealing as possible. Sealing shall not be required for isolation and control joints in slabs on grade which will be covered with finish flooring material. The groove shall be left ready to receive the filling material that will be provided as a part of the finish floor covering work.
PROPORTIONING, MEASUREMENT AND MIXING
Concrete mixes shall be prepared in permanent concrete mixing plants, and their consistency and workability shall be suitable for the type placing they are intended for.
Ready Mix Concrete
Ready mix concrete furnished in revolving concrete mixers on trucks will be acceptable provided the requirements of UNI EN 206-1, and the following: The ready-mixed concrete manufacturer shall furnish duplicate delivery tickets with each load of concrete delivered to the site of the work, one for the Contracting Officer and one for the Contractor. Delivery notes shall provide the following information:
Type and Brand of Cement Cement Content per cubic meter of Concrete Maximum Size of Aggregate Amount and Brand Name of Air Entraining Admixture Amount and Brand Name of Water Reducing and/or other Admixtures Total Water Content Expressed by Water/Cement Ratio. Ready-Mixed Concrete. Ready-mixed concrete may be used provided that: (a) the plant is equipped properly in all respects for the accurate proportioning and proper mixing and delivery of the concrete, including accurate water measurement and control;
(b) the interval between batches for a pour shall not exceed 30 minutes; and (c) the time elapsing between the introduction of the mixing water to the cement and aggregates, or the cement to the aggregate, and placing of the concrete in final position in the forms shall not exceed one hour. Ready mixed concrete shall be mixed and delivered by means of one of the following methods:
a. Central Mixing: Central mixing by mixing the concrete completely in a stationary mixer at the plant and transporting the mixed concrete to the site of the work in a truck agitator or a truck mixer operating at agitating speed. Mixing in the stationary mixer shall be as specified herein.
b. Shrink Mixing: Shrink mixing by mixing the concrete partially in a stationary mixer at the plant and completing the mixing in a truck mixer. Each batch of concrete shall be mixed in the stationary mixer a sufficient time to intermingle the ingredients and in the truck mixer nor less than 50 nor more than 100 revolutions of the drum or blades at mixing speed. Any additional mixing in the truck mixer shall be at agitating speed.
c. Transit Mixing: Transit mixing by mixing completely in a truck mixer. Mixing shall be in accordance with the requirements for truck mixing specified hereinbefore under shrink mixing. Mixers and agitators shall be operated within the limits of capacity and speed of rotation designated by the manufacturer, and shall be capable of reproducing a homogeneous mixture of uniform color. Weighing and moisture determination shall be as specified herein.
Proportioning of the Concrete Mix
Mix Design
Mix design will be in accordance with the applicable portions of Law 1086 and the following specification. Prior to starting actual work, the Contractor shall obtain the services of a licensed civil engineer. Said engineer shall design the concrete mix, or mixes (established proportions) to meet strength requirements called for on structural drawings and shall submit three certified copies of the design to the Contracting Officer. Once mixes have been approved, the Contractor shall adhere to the design mixes unless otherwise directed, in writing by the Contracting Officer.
Determination of Maximum Water Content Allowable. The strength quality of the concrete proposed for the use shall be established by tests made in advance of the beginning of operations, using the consistencies suitable for the work. The maximum quantity of water allowed by the ratio shall include the free water in the aggregate. However, moisture absorbed by the aggregates that is not available either for hydration of the cement or for lubrication of the mixture shall not be included.
Volumetric Proportioning
Where volumetric proportioning is permitted by the Contracting Officer or where the failure of equipment necessitates the temporary use of volumetric proportioning, the weight proportions indicated in the tables shall be transposed into equivalent volumetric proportions by weighing representative samples of the aggregates in the condition in which they will be measured. In determining the true volume of the fine aggregate, allowance shall be made for the bulking effect from the moisture contained therein. Suitable allowances shall also be made for variations in the moisture conditions of the aggregates.
Mixing of Concrete
Shall be in strict accordance with the applicable portions of Law 1086 and the following specification. Measurements of Materials, Mixing and Equipment All concrete shall be machine-mixed, except that in emergencies the mixing way may be by hand in wooden or steel boxes. Except when readymixed concrete is used, the Contractor shall provide, at the site of the work, an approved type of batch mixer equipped with an accurate water measuring and control device, and capable of producing a homogeneous concrete mixture of uniform color.
The apparatus provided for weighing the aggregates and cement shall be designed especially for this purpose. The fine aggregate, each size of coarse aggregate, and cement shall each be weighed separately, cement in standard packages (sack) need not be weighed, but bulk cement or non standard packages shall be weighed. The accuracy of all measuring devices shall be such that successive quantities can be measured to within 5 percent of the desired amount.
All measuring devices shall be subject to approval. The volume of the mixed material per batch shall not exceed the manufacturer's capacity of the mixer. The time of mixing at the rated speed after all cement and aggregates are in the mixer drum shall not be less than one minute for mixers having a capacity of 750 liters or less; for mixers of larger capacities, the minimum time shall be increased by 15 seconds, for each 400 liters or fraction thereof of additional capacity.
All mixing water shall be introduced in the drum before one-fourth of the mixing time has elapsed. The mixer drum shall rotate at a peripheral speed of about 60 meters per minute throughout the mixing period. The entire contents of the mixer drum shall be discharged before recharging. The Contractor shall furnish the necessary equipment and shall establish accurate procedures, subject to approval, for determining the quantities of free moisture in the aggregates, volumetric determinations shall be made at intervals as directed.
The retempering of concrete which has partially hardened, i.e., mixing with or without additional cement, aggregate or water will not be permitted. Generally, mixing of materials in the concrete mixer shall be done in the following order
1st - Part of the total water to be used in the mixture.
2nd - The cement and sand simultaneously.
3rd - The gravel.
4th - The rest of the necessary water to complete the specified proportions. Water shall be added by a continuous supply.
Except in special contingencies, and if it is approved by the Contracting Officer, temperature of water for mixing shall not exceed 35 degrees Centigrade. Different types of cement shall not be used in mixing one concrete batch. Prior to start of mixing with a new type of agglomerate, mixer shall be thoroughly cleaned.
Insulating Lightweight Concrete
Proportion and Mixes. The insulating lightweight concrete shall be proportioned and mixed so as to have an homogenous concrete with the following characteristics:
a. Density: Shall not exceed 600 kg/cu.m. with dry air conditions.
b. Compressive Strength: Shall not be less than 50 kg/sq.cm.
PREPARATIONS FOR CONCRETE PLACING
General
All surfaces against which concrete is to be placed, shall be free of debris, loose material, standing water, snow, ice, and any other deleterious substances before the start of concrete placing. Standing water shall be removed without washing over freshly deposited concrete. Any flow of water shall be diverted through side drains provided for such a purpose.
Subgrade Under Foundations and Footings
The subgrade under foundations and footings shall be undisturbed clean surfaces, free from frost, ice, and mud, and water before concrete is deposited. When the subgrade material is semi-porous and dry, the subgrade surfaces shall be sprinkled with water as required to eliminate suction, at the time the concrete is deposited. When the subgrade material is porous, the subgrade surface shall be covered with the specified water barrier subgrade cover; this may also be used over semiporous, dry subgrade material instead of water sprinkling.
Subgrade Under Slabs on Grade, Pavement, Sidewalk and Curb. Before construction of slabs on grade, underground work on pipes and conduits shall have been completed and approved. The previously constructed subgrade or fill shall be cleaned of all foreign material and shall be inspected by the Contractor in the presence of the Contracting Officer for adequate compaction and surface tolerances as specified. The finished surface of drainage fill under interior slabs on grade shall not show any deviation in excess of 10 millimeters, when tested with a 3 meter straightedge, parallel with and at right angles to the building lines.
The finished surface of subgrade or fill under exterior slabs on grade shall not be above, nor more than 3.0 centimeters below, the elevations indicated, and shall be graded to prevent ponding of water after rain. The drainage fill surface under interior slabs on grade shall be covered with the specified water-vapor barrier subgrade cover, immediately prior to placing reinforcement. The subgrade cover shall be carefully installed to avoid puncture or tear.
Punctures or tears occurring during subsequent operations shall be patched. The subgrade cover sheets shall be laid with not less than 15 centimeters lap at edges and ends, and in the direction in which concrete is to be placed. Patches and lapped joints shall be sealed with a vapor barrier adhesive or pressuresensitive vapor barrier tape not less than 5 centimeters wide. The subgrade or fill surface under exterior slabs or pavement on grade shall be prepared as hereinbefore specified for the subgrade under foundations and footings.
CONVEYING AND PLACING CONCRETE
It will be in strict accordance with the following:
Conveying
Concrete shall be conveyed from the mixer to the forms as rapidly as practicable by approved methods that will not cause segregation or loss of ingredients. It shall be deposited as nearly as practicable in its final position to avoid rehandling. At any point in conveying, the free vertical drop of the concrete shall not exceed one meter. Chuting will be permitted only where the concrete is deposited into a hopper before it is placed in the forms.
Conveying equipment shall be cleaned thoroughly before each run. All concrete shall be deposited as soon as practical after the forms have been coated and the reinforcement placed. It shall be placed before the initial set and in any event not later than 30 minutes after mixing or agitating. Concrete segregated in conveying shall not be used.
Placing
All concrete shall be placed in the dry, except when differently permitted by the project specification, and all necessary trenching, damming, draining and pumping shall be done. Fresh concrete shall be protected at all times from running water. Before placing concrete on porous subgrades, they shall be dampened as directed. Forms shall be cleaned of dirt and construction debris, water drained, and snow and ice removed. After the forms have been inspected and approved, the concrete shall be deposited in approximately horizontal layers to avoid flowing along the forms.
All concrete will be deposited continuously or in layers of a thickness such that no concrete will be deposited on concrete which has hardened sufficiently to cause the formation of seams and planes of weakness within the sections; a monolithic structure, the component parts of which are bonded together shall be produced. The method of depositing concrete shall be such as to avoid displacing the reinforcement. During placing, the concrete shall be compacted by puddling with approved tools and shall be worked around the reinforcement and imbedded fixtures and into corners and angles of the forms, care being taken to avoid over-working which may result in segregation.
The placing of concrete shall produce exposed surface of uniform color and appearance, free from pits and honeycomb. Where the congestion of reinforcing makes placing difficult, working of the concrete into place shall be accomplished by tapping or hammering the forms at the level of the concrete being placed with rubber hammers, wood mallets, or light mechanical hammers. Water accumulating on the surface of the concrete during placing shall be removed by absorption with porous materials in a manner that prevents removal of cement. Where the accumulation of water is excessive, adjustments shall be made in the quantity of fine aggregate, in the concrete proportion, or in the rate of placing, as directed.
Slab Placement
In addition to the requirements specified herein, placement of slabs shall be made in a checkerboard pattern. A minimum of 48 hours shall elapse between adjacent pours.
Vibration
All concrete with the exception of concrete slabs 10 centimeters or less in depth, shall be compacted with high frequency, internal, mechanical vibrating equipment supplemented by hand spading and tamping. Concrete slabs 10 centimeters or less in depth shall be compacted by wood tampers, spading, and settling with a heavy leveling straightedge. Vibrators shall be designed to operate with vibratory element submerged in the concrete, and shall have a frequency of not less than 6,000 impulses per minute when submerged. Vibration shall be discontinued when the concrete has been compacted thoroughly and ceases to decrease in volume.
Cold Weather Placement
Except when authorized specifically by the Contracting Officer, do not place concrete when the atmosphere temperature is below 5 degrees Centigrade or when the concrete is likely to be subjected to freezing temperatures within 48 hours. When so authorized, if concrete is likely to be subjected to freezing within 48 hours after placing, heat concrete materials so that temperature of the concrete when deposited shall be between 18 and 27 degrees Centigrade.
Methods of heating materials shall be subject to approval of the Contracting Officer. Do not heat mixing water above 35 degrees Centigrade. Remove lumps of frozen material and ice from the aggregates before placing aggregates in the mixer. Remove concrete damaged by freezing and replace with new concrete.
Hot Weather Placement
Reduce the temperature of the concrete being placed and prevent rapid drying of newly placed concrete. When the outdoor ambient temperature is more than 25 degrees Centigrade, the temperature of the concrete as placed shall not exceed 32 degrees Centigrade; shade the fresh concrete as soon as possible after placing; and start curing as soon as the surface of the fresh concrete is sufficiently hard to permit curing without damage to the concrete. When the outdoor ambient temperature is more than 40 degrees Centigrade, do not place concrete.
SURFACE FINISHES
General Requirements
As soon as the forms are removed all defective areas shall be patched and all the holes shall be filled with cement mortar of same composition as that used in the concrete, except that for exposed surfaces part of the cement shall be white Portland cement to provide a finish color matching the surrounding concrete. Defective areas shall be cut out to solid concrete but to a depth of not less than 25 millimeters. The edges of the cut shall be perpendicular to the surfaces of the concrete.
They are to be patched and at least 15 centimeters adjacent thereto shall be saturated with water before placing the mortar. The mortar shall be mixed approximately one hour before placing and shall be remixed occasionally during this period with a trowel without the addition of water. It shall be compacted into place and screeded slightly higher than the surrounding surface. Patches on exposed surfaces shall be finished to match the adjoining surfaces after they have set for a period of one hour or more. Patches shall be cured as specified for the concrete. Tie holes shall be wetted with water and filled solid with mortar. Holes extending through the concrete shall be filled by means of a plunger type gun or other suitable device from the unexposed face. The excess mortar shall be wiped off the exposed face with a cloth.
Standard Finish
Standard Smooth Finish. Standard smooth finish shall be the as-cast concrete surface as obtained with the form facing material for standard smooth finish, defective areas repaired and patched as specified hereinbefore, and all fins and other projections on the surface completely removed. Standard smooth finish shall be given all concrete formed surfaces that are to be exposed to view unless otherwise indicated, or that are to be covered with a coating material applied directly to the concrete or with a covering material bonded to the concrete, such as waterproofing, dampproofing, painting, or other similar coating system.
Rubbed Finish Provide for all concrete exposed to public view. Construct exposed concrete with a smooth form finish. Finish as follows:
a. Smooth Rubbed: Provide on newly hardened concrete within 24 hours following form removal. Wet surfaces and rub with an abrasive tool to produce uniform color and texture. Use only the cement paste drawn from the concrete rubbing process.
Related Unformed Surfaces
The tops of walls, horizontal offsets, and similar unformed surfaces occurring adjacent to formed surfaces shall be struck off smooth after the concrete is placed and shall be finished to a texture matching that of the adjacent formed surfaces. The final surface treatment on formed surfaces shall continue uniformly across the adjacent uniformed surfaces. Tops of foundations need only receive a screed finish.
Floor and Slab Finishes
General Requirements
Where drawings call for a finish floor of concrete, the type of floor finish, unless otherwise indicated on the drawing or specified, shall be a smooth steel troweled monolithic finish.
Float Finish
Float finish shall be given monolithic slab surfaces that are to receive trowel finish and other finishes as specified. After placing concrete slabs as hereinbefore specified, the concrete shall not be worked further until ready for floating. Floating shall begin when the bleed water has disappeared, or when the concrete mix has stiffened sufficiently to permit the proper operation of a power-driven float, or when both conditions have occurred. The surface shall then be consolidated with power-driven floats.
Hand floating shall be used in locations inaccessible to power-driven floats. Trueness of surface shall be checked at this stage with a 3 meter straightedge. The surface shall be plane to a tolerance not exceeding 5 millimeters in 3 meters when tested with a 3 meter straightedge placed on the surface at not less than 2 different angles. All high spots shall be cut down and all low spots shall be filled. Surfaces shall be uniformly sloped to drains. Immediately after the completion of leveling the surface shall be refloated to a uniform, smooth, granular texture.
Trowel Finish
Trowel finish shall be given all monolithic slab surfaces that are to be exposed to view, unless otherwise indicated, and slab surfaces that are to be covered with resilient flooring, carpet, paint or other finish coating system. After the completion of the float finish as specified above, the surface shall receive a trowel finish. The first troweling after the completion of the float finish shall be done by a power-driven trowel and shall produce a smooth surface which is relatively free of defects but which may contain some trowel marks.
Additional trowelings shall be done by hand after the surface has hardened sufficiently. The final troweling shall be started when a ringing sound is produced as the trowel is moved over the surface. The surface shall be thoroughly consolidated by the hand troweling operation. The finished surface shall be free of any trowel marks, uniform in texture and appearance, and be plane to a tolerance not exceeding 3 millimeters in 3 meters when tested with a 3 meter straightedge placed anywhere on the surface in any direction. Any surface defects of sufficient magnitude to show through the floor covering shall be removed by grinding.
Chemical –Hardener Finish
Chemical-hardener finish shall be applied to the interior floor surfaces of all monolithic slab surfaces that are exposed to view. The liquid chemical floor hardener shall be applied after complete curing and drying of the concrete surface. Approved proprietary chemical hardeners shall be applied in 3 coats and in accordance with the manufacturer’s printed directions. After the final coat of chemical hardener solution is completed and dry, any surplus hardener shall be removed from the surface by scrubbing and mopping with water.
Non-Slip Broom Finish
Non-slip broom finish shall be given the surfaces of exterior concrete unless otherwise indicated. Non-slip broom finish shall also be given to steps and platforms, sidewalks, curbs, equipment pads and elsewhere where indicated. Immediately after the completion of trowel finish, the surface shall be slightly roughened by brooming with a fiber-bristle brush in a direction transverse to that of the main traffic. The surface shall be broomed only when the troweled surface is sufficiently hardened to retain the scoring or ridges.
Epoxy Floor Coating
An epoxy floor coating shall be applied where shown on drawings. The two component epoxy floor coating shall be applied after complete curing and drying of the concrete for a minimum of 28 days. The epoxy floor coating shall be mixed and applied in accordance with the manufacturer’s written instructions.
Edging
After concrete finishing has been completed, the edges of slabs along the forms and at the joints shall be carefully finished with an edging tool to form a smooth rounded surface having a radius not greater than 4 millimeters. Tool marks shall be eliminated, and the edges shall be smooth and true to line. Tooled Joints. Sidewalk joints shall be carefully finished with an edging tool to form a smooth rounded or chamfered surface. Sealer\Hardener. Provide on all slabs that are not to receive other floor finishes such as tile or carpet.
PROTECTION AND CURING
General Requirements
Concrete, including that to be given a special finish, shall be protected adequately from injurious action by sun, rain, flowing water, frost, and mechanical injury, and shall not be allowed to dry out from the time it is placed until the expiration of the minimum curing period specified hereinafter. Water curing shall be accomplished by keeping the surface of the concrete continuously wet by covering with water or with approved water saturated covering, or by spraying. All water used for curing shall be fresh water.
Where water curing is not used, curing shall be accomplished by sealing in the water carried by the concrete so that it cannot evaporate. This may be done by leaving the forms in place or by other means, such as covering with an approved waterproof material for curing concrete as specified herein. Coating shall not be used, however, where its appearance would be objectionable. Seal coverings and coatings shall provide not less than 90 percent water retention for 72 hours of the water contained within the concrete at the time the covering or coating was applied.
Seal coverings and/or coatings shall not be used on floor receiving a chemical floor hardener. Floors to receive a chemical floor hardener shall be water cured and covered with an approved waterproof material as specified herein. Where wood forms are left in place for curing, they shall be kept sufficiently damp at all times to prevent opening at the joints and drying out the concrete. All portions of the structure shall be kept moist and at a temperature of not less than 10 degrees Centigrade for the full curing periods specified hereinafter, and all portions of the time during which either moisture or warmth is lacking shall not be counted effective for curing.
When membrane curing compound is used, the surface of the concrete shall be protected from traffic or other abrasive action that may break the membrane, for the full period of equivalent water curing.
Curing Period Shall be as Follows
All concrete shall be cured for 14 days unless otherwise noted. When the compressive-test cubes representative of parts of the structure already placed show strengths more than 10 percent below the required 7 day strengths, those parts of the structure shall be given additional water curing, as directed by the Contracting Officer.
REMOVAL OF FORMS AND PROTECTION
Form Removal
D.M. 9 Jan. 1996 unless specified otherwise. Results of suitable control tests will be used as evidence that concrete has attained sufficient strength to permit removal of supporting forms. Test specimens shall be removed from molds at the end of 24 hours and stored in the structure as near points of sampling as possible; shall receive insofar as practicable the same protection from the elements during curing as is given those portions of the structure which they represent; and shall not be removed from the structure for transmittal to the laboratory prior to expiration of three-fourths of the proposed period before removal of forms.
Supporting forms or shoring shall not be removed until strength of control-test specimens has attained a value of at least 200kg/square centimeter. In the absence of specific proof of the concrete resistance, under normal working and environmental conditions for pouring and curing, the following minimum periods of time should be observed before form removals for pours performed with concrete mixed with normal cement:
- Side forms for beams and columns: 3 days
- Slabs having short spans: 10 days
- Shoring for beams: 28 days
- Cantilevered structures: 28 days
The Contractor shall exercise care to assure that the newly constructed portions of the structure are not subjected to heavy construction or material loading. Tie-rod clamps to be entirely removed from the wall shall be loosened 24 hours after concrete is placed, and form ties, except for a sufficient number to hold forms in place, may be removed at that time. Ties wholly withdrawn from wall shall be pulled toward inside face. Whenever the formwork is removed during the concrete curing period, the exposed concrete shall be cured as specified.
Re-Use of Forms
The surfaces of forms that are to be re-used shall be thoroughly cleaned and repaired except that split, frayed, or delaminated form facing material shall not be re-used. The contact surfaces of re-used forms shall be coated as specified.
Protection
Protection from Mechanical Injury. During the curing period, the concrete shall be protected from damaging mechanical disturbances particularly load stresses, heavy shock, and excessive vibration and from damage caused by rain or running water. Protection After Curing. All finished concrete surfaces shall be protected from damage by construction operations.
MISCELLANEOUS CONSTRUCTION
Concrete Sidewalks
Unless otherwise indicated, concrete sidewalks shall not be less than 10 centimeters thick and shall have contraction joints every 2 linear meters, cut to a depth of 2 centimeters with a jointing tool after the surface has been finished. Transverse expansion joints shall be installed at all returns and shall be made with preformed joint material. Walks shall receive a broom finish as specified hereinbefore.
Edges of the sidewalks and joints shall be edged with a tool having a radius not greater than 4 millimeters. Walks shall have a transverse slope of 2 percent. The surface of the concrete shall show no variation in cross section in excess of 6 millimeters in 3 meters.
Splash Blocks
Splash blocks shall be provided at outlets of downspouts emptying at grade; they shall be of precast concrete with countersunk dishes finished smooth and sloped to drain from the building. The earth shall be compacted to provide firm bases for the blocks.
Sidewalks and Patios
Provide concrete base for precast concrete pavers for patios and, where indicated, for sidewalks. Transverse expansion joints shall be installed at changes in direction, where sidewalk abuts curb, rigid pavement or similar structures or in straight runs every 15 meters maximum. Walks shall have a transverse slope of 2 percent unless otherwise indicated.
Cast-in-place Concrete Curbs
Shall be as indicated on the plans. The curbs shall be poured continuously with cutter plates used to separate sections into individual lengths of 4 linear meters, maximum. The curb joints shall align with the sidewalk joints where the curb is adjacent to sidewalk. Provide expansion joints as indicated.
Concrete Lintels, Copings and Sills
Concrete lintels, copings and sills shall be either cast-in-place or precast concrete. All exposed surfaces shall be smooth and true, with sharp edges. If precast concrete is used, it shall be damp-cured for not less than 7 days and allowed to dry out before being moved. Steel reinforcement shall be provided in copings and sills. If precast concrete is used, suitable provisions shall be made for anchoring the sections to the walls, and each section shall be set in a full bed of Portland cement mortar.
All vertical joints shall be grouted solidly except for a 2 centimeter depth at front, back and top surfaces; the front and back, shall be tuckpointed, and the top surface shall be filled with a non-staining and nonshrinking caulking compound. Copings and sills shall be provided with seats, washes, lugs, and drips, where indicated and/or necessary to provide proper drainage.
Pits and Trenches
Pits and trenches shall have the bottom slabs and walls keyed and bonded together properly. Where practicable, the bottom slabs and walls shall be placed integrally. Slabs forming covers for pits and trenches shall have the openings formed to suit the installation of equipment and apparatus.
Miscellaneous Concrete
Concrete for valve box collars, sanitary sewage and storm drainage clean out collars, steps and guard post footings shall be cast-in-place in accordance with Paragraph 1.5 of this specification section.
Reinforced wall with ready mixed mortar (SHOTCONCRETE)
The interior face of the perimeter walls shall be coated with the application of 10 centimeter thick layer of ready mixed mortar, reinforced with 10 millimeter diameter, 15x15 centimeter Feb44K steel wire mesh. Prior application of the mortar the walls shall be blast clean and shall be sound, compact and free from oil or grease. Furthermore prior mortar application walls shall be wetted to refusal.
Ready mixed mortar shall be placed with a dry jet spraying machine, operated by compressed air. The water for the mixing is added at the spraying nozzle output. Mortar shall be placed in layers of thickness not above four centimeters. Mortar coated surface shall be kept humid for at least twelve hours to avoid fissures due to the mixing water quick evaporation. Mortar can be trowel finished as necessary.
SAMPLING AND TESTING
Sampling
Samples of fresh concrete shall be collected in accordance with UNI 6126 during each working day as required to perform all tests specified herein. Test specimens shall be made and cured in accordance with UNI EN 12390-2 and UNI EN 12390-1.
Consistency Tests
Slump shall be determined in accordance with UNI 6126. Samples for slump determination will be taken from the concrete while it is being placed. Tests shall be made at the beginning of a concrete placement operation and at subsequent intervals to insure that the specification requirements are met. In addition, tests shall be made each time test cylinders are made.
Air Content
Air-entrained concrete shall be tested for air content at the same frequency as specified for slump tests in accordance with UNI EN 12350-7.
Compressive Tests
Testing of specimens for compressive strength shall be in accordance with UNI EN 12390-3, and D.M. 9 Jan. 1996, Control Type A. Tests will be made at 7 and 28 days from time of molding. When a satisfactory relationship between 7-day and 28-day strengths has been established, the 7-day test results may be used as an indicator of the 28-day strength. Each test shall be the average of the strengths of the four test specimens of a set except that if one specimen in a set of four shows evidence, other than low strength, of improper sampling, molding, handling, or curing, the remaining three specimens shall be considered the test result.
Not more than 10 percent of the specimens tested shall have compressive strengths of less than that specified. Four test specimens shall be made for each set of tests. Two specimens shall be tested at 7 days and the other two at 28 days. Frequency of compressive tests on concrete specimen shall be as follows:
a. Not less than 8 test specimens for each 150 cubic meters or fraction thereof.
b. Not less than 4 test specimens for each day of concrete places that day.
c. Space testing so that no more than 4 of the test specimens are taken from any one batch.
INSPECTION AND ACCEPTANCE PROVISIONS
Evaluation of Concrete Quality Control Test Results. The concrete quality control tests will be evaluated as specified. Concrete delivered to the point of final placement having a slump or total air content outside the values specified, shall not be used in the work. Compressive strength tests will be considered satisfactory if the average of any group of 5 consecutive compressive strength tests which may be selected is in each instance equal to or greater than the 28-day compressive strength of the class of concrete, and if not more than one compressive strength test in 10 has a value less than 90 percent of the 28-day compressive strength.
On job tests will be in strict accordance with UNI EN 12390-3. If either 7-day or 28-day tests are below specified strengths, the Contractor will take immediate action to correct any defective mixing practices and, if necessary, to adjust design mix.
Strength of Concrete Structure
The strength of the concrete structure in place will be considered potentially deficient if it fails to comply with any of the requirements which control the strength of the structure, including the following conditions:
Failure to meet compressive strength tests as evaluated herein. Reinforcement not in accordance with the requirements specified on the drawings. Concrete which differs from the required dimensions or location in such a manner as to reduce strength. Concrete curing, and protection of concrete against extremes of temperature during curing, not conforming to the requirements specified. Concrete subjected to damaging mechanical disturbances; particularly load stresses, heavy shock, and excessive vibration. Poor workmanship likely to result in deficient strength.
Test of Hardened Concrete in, or Removed from, the Structure
When the results of the strength tests of the control specimens indicate that the concrete as placed does not meet specification requirements or where there is other evidence that the quality of the concrete is below specification requirements, core-boring tests shall be made in conformance with UNI 6131. The cost of such tests shall be borne by the Contractor. Strength of cores from each member or area will be considered satisfactory if their average is equal to or greater than 90 percent of the 28-day design compressive strength of the class of concrete.
Core tests shall be made by a concrete testing service approved by the Contracting Officer. Test results shall be reported in writing to the Contracting Officer on the same day that tests are made. Reports shall contain the project name and number, date, name of contractor, name of concrete testing service, location of test core in the structure, concrete class represented by core sample, nominal maximum size aggregate, design compressive strength of the concrete class, compression breaking strength and type of break, length of core test specimen before capping, compressive strength after correcting for length-diameter ratio, direction of application of the load on the core test specimen with respect to the horizontal plane of the concrete as placed, and the moisture condition of the core test specimen at time of testing.
Core holes shall be filled solid with patching mortar and finished to match the adjacent concrete surfaces. If the results of the core tests are unsatisfactory or if core tests are impracticable to obtain, static load tests shall be made. If the proposal is approved, the load tests shall be made by the Contractor and the test results shall be evaluated by the Contracting Officer. The costs of the load tests shall be borne by the Contractor. If any concrete shows evidence of failure during the load test or fails the load test as evaluated, the deficiency shall be corrected.
Any deficiency shall be corrected in a manner approved by the Contracting Officer and at no additional cost to the Government. The tests noted herein are separate from and in addition to the requirements for load tests as required by applicable portions of Law 1086.
Contractor Furnished Mix Design
If test results of any concrete used in the project show that the concrete strength is below the specified limits and does not meet other requirements of this specification, the Contractor shall make all necessary adjustments, at his expense. Concrete that does not meet the specified strength at the end of 60 days after placement shall be removed or otherwise corrected at the Contractor's expense.