M 41-10 Page 6-3316-22 Modified Concrete Overlay - Latex
6-22.1 Description
This Section 6-22 is for Contracts with the bid item “Modified Concrete Overlay” when the Contractor elects to use latex modified concrete for the overlay. If the Contractor elects to use microsilica modified concrete or fly ash modified concrete for the overlay, use Section 6-21, Modified Concrete Overlay – Microsilica or Fly Ash. This Work consists of surveying, Scarifying the existing concrete bridge deck, removing and replacing unsound concrete below the Scarification Depth, and placing, finishing, curing, and texturing a modified concrete overlay using latex modified concrete.
6-21.1(1) Definitions
The Contractor shall comply with 6-21.1(1).
6-22.2 Materials
Materials shall meet the requirements of the following sections: High Molecular Weight Methacrylate (HMWM) Resin for Crack and Cold Joint Sealing 6-21.2(3) Sand for Abrasive Finish of Cracks and Cold Joints 6-21.2(3) Portland Cement 9-01.2(1) Blended Hydraulic Cement 9-01.2(1)B Latex Admixture 6-22.2(1)A1 Fine Aggregate 9-03.1 Course Aggregate 9-03.1 Mortar 9-20.4 Burlap Cloth 9-23.5 Admixtures 9-23.6 Water for Concrete 9-25.1
6-22.2(1) Modified Concrete
6-22.2(1)A Latex Modified Concrete
The modified concrete shall be latex modified concrete. Latex modified concrete shall be a workable mix, uniform in composition and consistency. Mix proportions per cubic yard shall be as follows: Type I or II Portland Cement, or Type IL(X) Blended hydraulic Cement 1.00 parts by weight Fine Aggregate 2.40 to 2.75 parts by weight Coarse Aggregate 1.75 to 2.00 parts by weight Latex Admixture 3.50-gallons per bag of cement Water/Cement Ratio 0.33 maximum Air Content of Plastic Mix 6 percent maximum Slump 7 inches maximum The aggregates shall be proportioned such that the amount of aggregate passing the No. 4 sieve is 65 ± 5 percent of the total aggregate (fine plus coarse). All calculations shall be based on dry weights. The moisture content of the fine aggregate and coarse aggregate shall be no more than 3.0 and 1.0 percent, respectively, above the saturated surface dry condition. The maximum allowable and actual water/cementitious ratio shall be calculated using all of the available mix water, including water added at the plant, water added in transit and at the job site, water in all admixtures, 52 percent of the latex admixture, and the free Modified Concrete Overlay - Latex 6-22 Page 6-332 M 41-10water in the aggregates but not the water absorbed by the aggregates. The following are considered cementitious materials: portland cement and blended hydraulic cement. Ground granulated blast furnace slag, fly ash, microsilica fume, and Type 3 portland cement shall not be used in Latex Modified concrete. Fine aggregate shall be Class 1. Coarse aggregate shall be AASHTO grading No. 7 or No. 8. The Contractor shall adjust the slump to accommodate the gradient of the bridge deck, subject to the maximum slump specified.
6-22.2(1)A1 Latex Admixture
Latex admixture shall be a non-toxic, film-forming, polymeric emulsion in water to which all stabilizers have been added at the point of manufacture. The latex admixture shall be homogeneous and uniform in composition, and shall conform to the following: Polymer Type Styrene Butadiene Stabilizers: Latex Non-ionic surfactants Portland Cement Polydimethyl siloxane Percent Solids 46.0 to 49.0 Weight per Gallon 8.4 pounds at 77 ºF Color White PH (as shipped) 9 minimum Freeze/Thaw Stability 5 cycles (5ºF to 77ºF) Shelf Life 2 years minimum Latex admixture will be accepted based on submittal of a Manufacturer’s Certificate of Compliance in accordance with Section 1-06.3.
6-22.2(1)A2 Storing and Handling Latex Admixture
Latex admixture shall be kept in suitable containers that will protect it from freezing and from exposure to temperatures in excess of 85ºF. Containers of the admixture shall not be stored in direct sunlight for periods in excess of 10 days. When stored in direct sunlight the top and sides of the containers shall be covered with insulating blanket material. Storage of the latex admixture may extend over a period greater than 10 days as long as the conditions specified above are maintained and the latex admixture is agitated or stirred once every 10 days. Stirring or agitation of the admixture shall be done mechanically in accordance with the manufacturer’s recommendation. If the ambient temperature is higher than 85ºF at any time during the storage period, the admixture shall be covered by insulated blankets or other means that will maintain the admixture temperature below 85ºF. Latex admixture shall be strained through a Number 10 strainer at the time it is introduced into the mixing tank from the storage containers.
6-22.2(2) Concrete Class M
The Contractor shall comply with Section 6-21.2(2).
6-22.2(3) Materials for Sealing Cracks and Cold Joints
The Contractor shall comply with Section 6-21.2(3).
6-22.3 Construction Requirements
6-22.3(1) Sequence of Work
The Contractor shall comply with Section 6-21.3(1).
6-22 Modified Concrete Overlay - Latex
M 41-10 Page 6-3336-22.3(2) Equipment
6-22.3(2)A Rotary Milling Machines
The Contractor shall comply with Section 6-21.3(2)A.
6-22.3(2)B Hydro-Demolition Machines
The Contractor shall comply with Section 6-21.3(2)B.
6-22.3(2)C Power Driven Hand Tools
The Contractor shall comply with Section 6-21.3(2)C.
6-22.3(2)D Air Compressor
The Contractor shall comply with Section 6-21.3(2)D.
6-22.3(2)E Vacuum Machine
The Contractor shall comply with Section 6-21.3(2)E.
6-22.3(2)F Water Delivery System
The Contractor shall comply with Section 6-21.3(2)F.
6-22.3(2)G Finishing Machine
The Contractor shall comply with Section 6-21.3(2)G.
6-22.3(2)H Mobile Mixer for Latex Modified Concrete
Latex modified concrete shall be mixed and transported in self-contained, self-propelled, continuous-mixing units conforming to the following requirements:
1.The mixer shall be equipped so that it can be grounded.
2.The mixer shall be equipped to provide positive measurement of the portland cement being introduced into the mix. A recording meter, visible at all times and equipped with a ticket printout, shall be used.
3.The mixer shall be equipped to provide positive control of the flow of water and latex admixture into the mixing chamber. Water flow shall be indicated by a flow meter with a minimum readability of ½ gallon per minute, accurate to ± 1 percent. The water system shall have a bypass valve capable of completely diverting the flow of water. Latex flow shall also be indicated by a flow meter with a minimum readability of 2 gallons per minute, accurate to ± 1 percent. The latex system shall be equipped with a bypass valve suitable for obtaining a calibrated sample of admixture.
4.The mixer shall automatically proportion and blend all components of the specified mix on a continuous or intermittent basis as required by the finishing operation.
5.The mixer shall discharge mixed material through a conventional chute directly in front of the finishing machine. Inspection of each mobile mixer shall be done by the Contractor in the presence of the Engineer and in accordance with the following requirements:
1.Check the manufacturer’s inspection plate or mix setting chart for the serial number, the proper operating revolutions per minute (rpm), and the approximate number of counts on the cement meter to deliver 94 pounds of cement.
2.Make a general inspection of the mobile mixer to ensure cleanliness and good maintenance practices.
3.Check to see that the aggregate bins are empty and clean and that the bin vibrators work. Modified Concrete Overlay - Latex 6-22 Page 6-334 M 41-104. Verify that the cement aeration system operates, that the vent is open, and that the mixer is equipped with a grounding strap. Check the cement meter feeder to ensure that all fins and pockets are clean and free from accumulated cement. If the operator cannot demonstrate, through visual inspection, that the cement meter feeder is clean, all cement shall be removed from the bin and the cement meter feeder inspected. The aeration system shall be equipped with a gauge or indicator to verify that the system is operating.
5.Verify that the main belt is clean and free of accumulated materials.
6.Check the latex strainer to ensure cleanliness. The initial calibration shall be in accordance with items 6-22.3(2)H1 through 6-22.3(2)H5 as follows:
6-22.3(2)H1 Cement Meter
a.Refer to the truck manufacturer’s mix setting chart to determine the specified operating rpm and the approximate number of counts required on the cement meter to deliver 94 pounds of cement.
b.Place at least 40 bags (about 4,000 pounds) of cement in the cement bin.
c.Ensure the mixer is resting on a level surface.
d.Ensure the mixer is grounded.
e.Adjust the engine throttle to obtain the specified rpm. Operate the unit, discharging cement until the belt has made one complete revolution. Stop the belt. Reset the cement meter to zero. Position a suitable container to catch the cement and discharge approximately one bag of cement. With a stopwatch, measure the time required to discharge the cement. Record the number of counts on the cement meter and determine the weight of the cement in the container. Repeat the process of discharging approximately one bag of cement until six runs have been made. Reset the cement meter to zero for each run. Example Calibration Record: Run No. Cement Counts Weight of Cement Time in Seconds 1 66 95 31 2 68 96 31.2 3 67 95.5 31.0 4 66 95 29.8 5 67 95.25 30.5 6 66 95 30.8 TOTAL 400 571.75 184.3 Pounds of cement per count on cement meter: Weight of Cement No. of Counts=571.75 400=1.43 LB./Count Counts per bag (94 pounds): 1.43=65.7 Counts Bag Pounds of cement discharged per second: Weight of Cement Time in Seconds=571.75 184.3=3.10 LB./SEC. Required time to discharge one bag: Time =94 3.10=30.32 SEC./Bag
6-22 Modified Concrete Overlay - Latex
M 41-10 Page 6-3356-22.3(2)H2 Latex Throttling Valve
a.Check to be sure that the latex strainer is unobstructed.
b.The latex throttling valve shall be adjusted to deliver 3.5 gallons of latex (29.4 pounds) for each bag of cement. From the above calculation 30.32 seconds are required to deliver one bag of cement.
c.With the unit operating at the specified rpm, discharge latex into a container for 30.3 seconds and determine the weight of latex. Continue adjusting the valve until 29.4 to 29.5 pounds of latex is discharged in 30.3 seconds. Verify the accuracy of this valve setting three times.
6-22.3(2)H3 Water Flow Meter
a.Set the water flow meter by adjusting it to flow at ½ gallon per minute.
b.Collect and weigh the water discharged during a 1-minute interval with the equipment operating at the specified rpm. Divide the weight of water by 8.34 to determine the number of gallons.
c.Repeat items a. and b., above, with the flow meter adjusted to 1½ gallons per minute.
6-22.3(2)H4 Aggregate Bin Gates
a.Set the gate openings to provide the amount of aggregate required to produce concrete having the specified proportions.
b.Discharge a representative sample of the aggregates through the gates and separate on the No. 4 sieve. Aggregates shall meet the requirements for proportions in accordance with Section 6-22.3(3)E.
c.Adjust the gate openings if necessary to provide the proper ratio of fine aggregate to total aggregate.
6-22.3(2)H5 Mobile Mixer Trial Runs and Calibration
Each mobile mixer shall be operated to produce at least ½ cubic yard of concrete, which shall be in compliance with these Specifications, prior to acceptance of the mobile mixer for job use. The Engineer will perform yield, slump, and air tests on the concrete produced by each mixer. Calibration of each mobile mixer shall be done by the Contractor in the presence of the Engineer. A complete calibration is required on each mixer on each concrete placement unless, after the initial calibration, the personnel having the responsibility of mixer calibration on subsequent concrete placement were present during the initial calibration of the mixer and during the concrete placement operations and are able to verify the dial settings of the initial calibration and concrete placement. If these criteria are met, a complete calibration need not be repeated provided that a single trial run verifies the previous settings of the cement meter, latex throttling valve, water flow meter, and aggregate gradations, and that the mixer has not left the project and the Engineer is satisfied that a complete calibration is not needed.
6-22.3(2)H6 Production Mixing Latex Modified Concrete
The mobile mixer shall be operated with strict adherence to the procedures set forth by its manufacturer. A minimum of two mobile mixers will be required at the overlay site for each concrete placement when the total volume of concrete to be placed during the concrete placement exceeds the material storage capacity of a single mobile mixer. Additional mobile mixers may be required if conditions require that material be stockpiled away from the jobsite. The Contractor shall have sufficient mobile mixers on hand to ensure a consistent and continuous delivery and placement of concrete throughout the concrete placement. Charging the mobile mixer shall be done in the presence of the Engineer. Mixing capabilities shall be such that the finishing operation can proceed at a steady pace. Modified Concrete Overlay - Latex 6-22 Page 6-336 M 41-106-22.3(3) Submittals The Contractor shall comply with Section 6-21.3(3), with the following revisions: Item 5 is revised to read: "5. A Type 2 Working Drawing of the mix designs for concrete class M and Letex Modified Concrete. The Contractor's submittal of a mix design shall be on WSDOT Form 350-040 and shall provide a unique identification for each mix design. A unique identification for the mix design is composed of the combination of the Mix Design Number and the Concrete Plant Number". Item 8 is added as follows: "8. A Type 1 Working Drawing of samples of the latex admixture and the portland cement (or blended hydraulic cement) for testing and compatibility."
6-22.3(4) Surveying for Modified Concrete Overlay
The Contractor shall comply with Section 6-21.3(4).
6-22.3(5) Operations on the Bridge Deck
The Contractor shall comply with Section 6-21.3(5).
6-22.3(6) Scarifying Concrete Surface
The Contractor shall comply with Section 6-21.3(6).
6-22.3(7) Deck Repair
The Contractor shall comply with Section 6-21.3(7).
6-22.3(8) Modified Concrete Overlay
6-22.3(8)A Surface Preparation
The Contractor shall comply with Section 6-21.3(8)A.
6-22.3(8)B Restrictions on Other Work
The Contractor shall comply with Section 6-21.3(8)B.
6-22.3(8)C Finishing Machine Setup
The Contractor shall comply with Section 6-21.3(8)C.
6-22.3(8)D Placing Modified Concrete Overlay
The Contractor shall comply with Section 6-21.3(8)D.
6-22.3(8)E Acceptance Testing Latex Modified Concrete
The Engineer will perform slump, temperature, and entrained air tests for acceptance in accordance with Section 6-02.3(5)D and as specified in this section after the Contractor has turned over the concrete for acceptance testing. The Engineer will perform testing as the concrete is being placed. Samples shall be taken on the first charge through each mobile mixer and every other charge thereafter. The sample shall be taken after the first 2 minutes of continuous mixer operation. Concrete samples for testing shall be supplied to the Engineer in accordance with Section 6-02.3(5)E. During the initial proportioning, mixing, placing, and finishing operations, the Engineer may require the presence of a technical representative from the latex admixture manufacturer. The technical representative shall be capable of performing, demonstrating, inspecting, and testing all of the functions required for placement of the latex modified concrete as specified in Section 6-21.3(8)D. This technical representative shall aid in the proper installation of the latex modified concrete. Recommendations made by the technical representative on or off the jobsite shall be adhered to by the Contractor. The Engineer will advise the Contractor in writing a minimum of 5 working days before such services are required.
6-22 Modified Concrete Overlay - Latex
M 41-10 Page 6-3376-22.3(9) Finishing Modified Concrete Overlay The Contractor shall comply with Section 6-21.3(9) and the following: Latex shall not be sprayed on a freshly placed latex modified concrete surface; however, a light fog spray of water is permitted if required for finishing, as determined by the Engineer.
6-22.3(10) Curing Modified Concrete Overlay
The Contractor shall comply with Section 6-21.3(10).
6-22.3(11) Checking for Bond
The Contractor shall comply with Section 6-21.3(11).
6-22.3(12) Sealing and Texturing Concrete Overlay
The Contractor shall comply with Section 6-21.3(12).
6-22.4 Measurement
Scarifying concrete surface will be measured by the square yard of surface Scarified. Type 1 Deck Repair and Type 2 Deck Repair will be measured by the square foot of surface area, below the Scarification Depth, of deck concrete removed in accordance with Section 6-21.3(7). Determination of whether a deck repair is Type 1 or Type 2 shall be in accordance with section 6-21.3(7). Modified concrete overlay will be measured by the cubic foot of material placed. For latex modified concrete overlay, the volume will be determined by the theoretical yield of the design mix and documented by the counts of the cement meter less waste. Waste is defined as the following:
1.Material not placed.
2.Material placed in excess of 6 inches outside a longitudinal joint or transverse joint. Finishing and curing modified concrete overlay will be measured by the square yard of overlay surface finished.
6-22.5 Payment
Payment will be made for each of the following Bid Items that are included in the Bid Proposal: “Surveying for Modified Conc. Overlay”, lump sum. The lump sum contract price for “Surveying for Modified Conc. Overlay” shall be full pay to perform the work as specified, including establishing secondary survey control points, performing survey quality control, creating the Existing Bridge Deck Surface Model, and recording, compiling, and submitting the survey records to the Engineer. “Scarifying Conc. Surface”, per square yard. The unit Contract price per square yard for “Scarifying Conc. Surface” shall be full pay for performing the Work as specified, including: testing and calibration of the machines and tools used; Scarifying to the Scarification Depth; excavation of unsound concrete below the Scarification Depth when such unsound concrete is removed during the pass of the hydro-demolition machine intended to stop at the Scarification Depth; disposal of all debris generated; scarification cleanup. “Type 1 Deck Repair”, per square foot. The unit contract price per square foot for Type 1 Deck Repair shall be full pay for performing the work as specified, including excavating and disposing concrete, and repair of concrete or rebar damaged by the contractor’s operations. Modified Concrete Overlay - Latex 6-22 Page 6-338 M 41-10“Type 2 Deck Repair”, per square foot. The unit contract price per square foot for Type 2 Deck Repair shall be full pay for performing the work as specified, including: excavating and disposing concrete; sandblasting and water-blasting; placing, consolidating, finishing, and curing concrete patches in Type 2 deck repairs; repair of concrete or rebar damaged by the contractor’s operations. “Modified Conc. Overlay”, per cubic foot. The unit contract price per cubic foot for “Modified Conc. Overlay” shall be full pay for furnishing and placing the modified concrete overlay, including the overlay material placed into Type 1 Deck Repairs in accordance with Section 6-21.3(7)G, and preparing the surface for the overlay including cleaning, sandblasting, and water-blasting. “Finishing and Curing Modified Conc. Overlay”, per square yard. The unit Contract price per square yard for “Finishing and Curing Modified Conc. Overlay” shall be full pay for performing all work required under Sections 6-22.3(9), 6-22.3(10),
6-22 3(11), and 6-22.3(12) including finishing the modified concrete overlay, curing the
modified concrete overlay, checking for bond, repairing unbonded areas, sealing all cracks and cold joints, sanding, and providing longitudinally sawn texture. Payment for the following shall be considered incidental to and included in the unit contract items included in the contract:
1.All Work and related costs for implementing the Process Wastewater Containment and Disposal plan
2.All Work and related costs for implementing the debris containment and disposal plan.
3.All Work and related costs for protecting adjacent traffic from flying debris. The unit Contract price per square yard for “Finishing and Curing Modified Conc. Overlay” shall be full pay for performing all work required under Sections 6-21.3(9),
6-21 3(10), 6-21.3(11), and 6-21.3(12) including finishing the modified concrete
overlay, curing the modified concrete overlay, checking for bond, repairing unbonded areas, sealing all cracks and cold joints, sanding, and providing longitudinally sawn texture. Payment for the following shall be considered incidental to and included in the unit contract items included in the contract:
1.All Work and related costs for implementing the Process Wastewater Containment and Disposal Plan.
2.All Work and related costs for implementing the Debris Containment and Disposal plan.
3.All Work and related costs for protecting adjacent traffic from flying debris.
6-22 Modified Concrete Overlay - Latex
Source: Washington Standard Specifications for Road, Bridge, and Municipal Construction, 2024 Edition. Pages 685–692 of 1,151.