721 SECTION 679 OVERLAYING OF PORTLAND CEMENT CONCRETE BRIDGE DECKS
679.1 -DESCRIPTION : The work shall consist of furnishing and placing a specialized concrete overlay to a designated grade line. Unless otherwise indicated on the plans, the Contractor may place any one of the specialized overlays allowed by the terms of this specification. Only one type of overlay will be allowed on any one structure.
679.1.1 -Other Work: The following work, as required by the contract plans, may also be performed under the terms of this section:
in the plans.)
679.1.2 -Definitions: 679.1.2.1 -Specialized Concrete Overlay: Two types of specialized concrete overlay are permitted as follows: 1) Latex Modified Concrete: A Portland cement concrete to which an approved styrene butadiene latex admixture has been added. 2) Silica Fume Concrete: A Portland cement concrete to which an approved silica fume admixture has been added.
679.1.2.2 -Slab Reconstruction Concrete: Slab reconstruction concrete is that concrete placed completely around exposed reinforcing bars.
679.1.2.3 -Curing Hour: A curing hour is any hour, beginning with the hour of placement, during which the temperature of the concrete surface remains at, or above, 50° F as measured by a recording thermometer.
679.1.2.4 -Curing Temperature: This is the air temperature at the concrete surface, or the air temperature between the concrete surface and its protective covering.
679.2 -MATERIALS : 679.2.1 -General: Materials used in the manufacture of sp ecialized concrete overlays shall meet the requirements specified in Section 601.2 of the Specifications and as required herein.
679.2.1.1 -Fine Aggregate: Fine aggregate shall be silica sand meeting the requirements of Sections 702.1.2 through 702.1.5 a nd 702.6 of the Specifications.
679.2.1.2 -Coarse Aggregate: Coarse aggregate shall be AASHTO Size No. 8 crushed stone or gravel conforming to Section 703 of the Specifications.
722 679.2.1.3 -Latex Admixture: Formulated latex modifier shall meet the requirements of Section 707.5 of the Specifications.
679.2.1.4 -Silica Fume Admixture: Silica fume admixture shall meet the requirements of Section 707.4.3.
679.2.1.5 -Bonding Grout : Bonding Grout shall not be used on Reconstruction Projects. On New Construction Projects Bonding Grout shall consist of the actual modified concrete used with coarse aggregates removed. The consistency of the slurry shall be such that it can be applied to the prepared concrete surfaces with a stiff bristle broom in a thi n, even coating that will not run or puddle. The bonding grout shall be applied using a stiff broom and worked into all areas of the slab. The rate of applying this coating shall be controlled so that the brushed material does not become dry before it is covered with additional material.
679.2.1.6 -Class K Concrete: Class K Concrete shall meet the requirements of Section 601 of the Specifications except that coarse aggregate shall meet the requirements of 679.2.1.2.
679.2.1.7 -Curing Materials: Burlap: This shall meet the requirements of Section 707.7 of the Specifications. Quilted Covers: These shall be clean and free of defects, providing a water retention blanket over the concrete. Acceptance will be based on visual inspection. Polyethylene Curing Covers: These shall meet the requirements of Section 707.6 of the Specifications. Plastic Coated Fiber Blankets: These shall be clean and free of defects, providing a water retention blanket over the concrete. Acceptance will be based on visual inspecti on.
679.2.1.8 -Replacement Bars: Reinforcing bars shall be Grade 60 and shall meet the material requirements of Section 602 of the Specifications. Replacement bars shall be spliced to existing bars using either minimum 30 -bar diameter lap splices or app roved mechanical connectors.
679.2.2 -Specialized Concrete Mix Design and Testing: Specialized concrete shall consist of a homogeneous mixture of cement, fine aggregate, coarse aggregate, latex or silica fume admixture, chemical admixtures and water. The Contractor shall determine mixture proportions in general accordance with ACI 211.1, "Standard Practice for Selecting Proportions for Normal, Heavyweight and Mass Concrete." Establishment of mixture proportions shall be coordinated with the ma nufacturer of the latex or silica fume admixture. Prior to the start of construction, the Contractor shall design and submit to the Engineer for approval the proportion of materials, including admixtures, to be used which will result in a workable concre te having the applicable properties enumerated below, including those of MP 711.03.23.
723 Design mixture testing shall include air content, slump, and compressive streng th results at 28 days and results of rapid chloride permeability tests. Compressive strength cylinders for silica fume concrete shall be cured in accordance with ASTM C192 for 28 days, but compressive strength cylinders for latex modified concrete shall be moist cured in accordance with ASTM C192 for 2 days then air cured in the lab at a temperature between 73.5 ± 3.5 °F for 26 days. For establishment of mixture proportions, rapid chloride permeability tests for silica fume concrete shall be made on represe ntative samples cured for 56 days in accordance with ASTM C192, then allowed to air dry in the lab at a temperature of 73.5 ± 3.5 °F until the time of test. These specimens shall be prepared and tested in accordance with AASHTO T 277 at an age of 56 to 90 days. For establishment of mixture proportions, rapid chloride permeability tests for latex modified concrete shall be made on representative samples moist cured in accordance with ASTM C192 for 2 days, air cured at in the lab at a temperature between 7 3.5 ± 3.5 °F for 54 days, then prepared and tested in accordance with AASHTO T 277 at an age of 56 to 90 days. The final rapid chloride permeability test result shall consist of the average of the two individual test results. This average shall not exceed 750 coulombs. For establishment of mixture proportions, as an alternative to the curing methods for rapid chloride permeability testing outlined in the previous paragraph, silica fume concrete specimens may be moist cured for 7 days in accordance with A STM C192, then cured for 21 days in lime -saturated water at 100.0 ± 3.5 °F, then tested at an age of 28 days. For establishment of mixture proportions, as an alternative to the curing methods for rapid chloride permeability testing outlined in the previous paragraph, latex modified concrete specimens may be moist cured for 2 days in accordance with ASTM C192, then cured for 26 days in air at 100.0 ± 3.5 °F and a minimum of 50% relative humidity, then tested at an age of 28 days. These methods of curing shal l be noted as the accelerated RCPT curing methods. The 28 -day compressive strength of the test mix that satisfies the 750 coulomb threshold shall be used as the basis for acceptance of the Specialized Concrete Overlay permeability requirements. Concrete for any slump test shall be deposited in a manner and location that excludes the effects of vibrations caused by traffic and concrete placement operations. The total concrete constituents shall contribute less than 0.10% water soluble chlorideion by w eight of cement. Use one brand and/or one source for any concrete constituent. The Contractor shall obtain a written statement from the manufacturer of the latex or silica fume admixture that confirms the compatibility of the material combination and the sequence in which they are combined. The written statement, along with the results of all required tests, shall be furnished to the Engineer prior to the pre -construction meeting (refer to 679.2.2.3). Substantiating data showing complia nce with the requirements of this specification shall also be submitted. This data shall also include the sources of coarse and fine aggregates as well as the brands of all admixtures to be used.
Contractor’s Quality Control: Quality control of the spe cialized concrete is the responsibility of the Contractor as designated in MP 601.03.50. The Contractor shall maintain equipment and qualified personnel, including at least one certified Portland Cement Concrete Technician who shall direct all field inspection, sampling, and testing necessary to determine the magnitude of the various properties of concrete governed by the Specifications and shall maintain these properties within the limits of this Specification. The Cont ractor’s personnel who conduct the fi eld sampling and testing shall be a certified Portland Cement Concrete Inspector. The quality control plan designated in MP 601.03.50 shall be submitted to the