300 SECTION 650
650.01 Description
This work consists of removing and replacing unsound concrete and/ or chloride contaminated concrete and resurfacing a bridge deck.
650.02 Equipment
A.General. Equipment Section Bridge Deck Overlays Finishing Equipment 155.07 D Sawing 155.09 Grinding 155.11 Concrete Buggy 155.12 Fogger 156.02 Milling Machine 156.03
B.Sandblasting Equipment. Use sandblasting equipment that removes rust scale, oil, and concrete lattice from the surface of the bridge deck and uncoated reinforcing bars . Do not use equipment that employs the wet sandblasting method. Equip airlines with filters that remove all oil from the air used by the sandblaster.
C.Pneumatic Hammers. Use hammers that ar e no larger than the nominal 30 pound class. Use chipping hammers no larger than the nominal 15 pound class to remove concrete around or beneath reinforcing bars. Pointed bits for pneumatic hammers may only be used when performing Class 4 removals.
D.Hand Tools. Provide hand tools, such as hammers and chisels, for the removal of final particles of unsound concrete or to achieve the required depth.
E.Hydrodemolition Equipment. Use hydrodemolition equipment with a water filter and pumping unit that operates in conjunction with a remotely controlled robotic water jet unit. Use equipment that produces high velocity water streams capable of removing concrete to the specified depth and is capable of removing rust and concrete from reinforcing bars. Use potable water. Calibrate the equipment by adjusting water pressure, robot speed, and jet oscillation speed to achieve the required depth of removal.
F.Placing and Finishing Equipment. Placing and finishing equipment includes hand tools used for placing and brushing mixed mortar and for distributing concrete to a depth sufficient for the concrete to be struck off with a screed. 301 650.03 MATERIALS
A.General. Item Section Concrete Admixtures 808 Burlap Cloth 810.01 A Water 812
B.Deck Concrete. Use Class AAE -5 Concrete that meets Section 802, “Portland Cement Concrete ,” except the design compressive strength required will be 4, 000 psi at 28 days.
C.Overlay Concrete.
1.General. Item Section Fine Aggregate 802.01 C.3 Coarse Aggregate – Size 5 802.01 C.2 Use cement that meets the requirements of AASHTO M 85, Type I or Type IA. Use coarse aggregate composed of crushed stone. Use crushed stone that has at least one fractured face on 75 percent of the particles retained on the number 4 sieve. Entrain air within the concrete as specified in Section 802.01 H, “Air Content” , except supply concrete with an air content between 5.0 and 7.0 percent of the volume of the conc rete at the time of placement. Produce concrete that has a slump of 1 inch or less, when determined according to ND T 119.
2.Mix Design. Use a mix design that has the percentages by volume shown in Table 650-01. Table 650 -01 Coarse Aggregate 31% ±1% Fine Aggregate 31% ±1% Air 6% ±1% Water 16% ±1% Cement 16% ±1% Total 100% 302 D. Bonding Grout. Produce grout for bonding the new concrete with existing deck concrete consisting of equal parts, by weight, of cement and fine aggregate mixed with water. Produce grout with a consistency that allows application with a stiff brush or broom and that does not puddle or run. Thin the grout as necessary when used for sealing construction joints.
650.04 Construction Requirements
A.General. Operate removal equipment without cutting, stretching, or damaging reinforcing steel remaining in place. Do not allow loads on the portion of the deck from which concrete has been removed, other than the equipment needed to remove and replace concrete. Use a buggy or pump to place concrete on the bridge deck. Do not open the overlay concrete to traffic until the curing period is complete.
B.Removals with Mechanical Equipment.
1.General. Angle pneumatic hammers at 65 degrees or less, as measured from the slab. Use non-powered hand tools to remove fine particles of concrete or to reach the required depth.
2.Class 1. Use a milling machine or grinding equipment to remove deck concrete to the depth designated in the plans for Class 1 removals.
3.Class 2. The Engineer will chain the deck after Class 1 removals are complete to determine the Class 2 removal ar eas. Remove concrete using a 30 pound pneumatic hammer or a combination of pneumatic hammers and grinding or milling.
4.Class 2-A. The Engineer will determine the amount of Class 2-A removal after C lass 2 removal is complete. The Engineer will direct Cl ass 2 -A removal when more than one-half of the circumference of a bar has lost bond with the surrounding concrete. The Engineer may direct Class 3 removals in place of Class 2-A removal if unsound concrete is encountered between reinforcing layers . Use 15 pound pneumatic hammers and hand tools to remove concrete around the periphery of the reinforcing steel. Obtain a minimum clearance of 3/4 inch around the bar.
5.Class 3. The Engineer will chain the deck after Class 2 removals are complete to determine the Class 3 removal areas. Remove concrete using 15 pound pneumatic hammers. 303 6. Class 4. The Engineer will chain the deck after Class 3 removals are complete to determine Class 4 removal areas. Remove concrete using 15 pound pneumatic hammers , through the full depth of the deck. Leave the edges of the hole tapered inward from top to bottom.
C.Removals with Hydrodemolition Equipment.
1.General. Immediately after performing each class of removal, use hand or mechanical means to remove loose debris from the deck to prevent debris from adhering to the surface. In areas inaccessible for using hydrodemolition equipment, remove concrete using mechanical equipment as specified in Equipment” or handheld hydrodemolition equipment.
2.Class 1H. The Engineer will designate a trial area of 30 square feet representing sound concrete. Use the trial area to set the hydrodemolition equipment to remove 1/2 inch of sound concrete. After calibrating the equipment, remove deck concrete to a depth of 1/2 inch below the existing surface. Clean the deck after performing Class 1H removals.
3.Class 2H. The Engineer will chain the deck after Class 1H removals are complete to determine the Class 2H removal areas that will receive a second pass from the hydrodemolition equipment.
4.Class 3H. The Engineer will chain the deck after Class 2H removals are complete to determine the Class 3H removal areas that will receive a third pass from the hydrodemolition equipment.
D.Final Preparations Prior to Deck Concrete and Overlay Concrete. At longitudinal construction joints, saw the previously placed overlay concrete to produce a straight vertical edge before placing the adjacent overlay concrete. Sandblast the deck and clean the deck surface with compressed air before placing concrete. Sandblast all exposed reinforcing steel to remove rust scale, oil, and concrete lattice from the surface of the bridge deck and reinforcing bars . Remove reinforcing bars which have lost 25 percent or more of the original cross section and replace with a new lap -splice bar. If a lap- splice is needed, contact the Engineer of Record to determine the required lap length. Us e an epoxy coated lap-splice bar only if tying to existing epoxy reinforcing steel. Include fabricating, transporting and installing new lap-splice bars in the bid item “Deck Concrete”. Repair any damaged epoxy coating on reinforcing steel according to AS TM D3963. Remove rust before making repairs. Protect the concrete surface from contamination during rebar coating repairs. After all preparations are complete, notify the Engineer a minimum of 24 hours before placing concrete.
E.Mixing of Materials. Set up concrete mixing equipment at the bridge site. Operate the concrete mixer at a rate that allows the finishing operation to proceed at a steady rate. Perform a yield box test before each pour to determine if the mobile mixer meets the manufacturer’s calibration requirements. Perform the yield test as follows: − Use a 1/4 cubic yard yield box; − Set the cement meter to zero; − Discharge concrete until the yield box is full, but not overflowing; and − Determine the cement meter count for the full yield box. If the meter count is within 1 percent of the previous meter count, it becomes the new calibrated meter count. If the meter count is not within 1 percent of the previous meter count, recalibrate the mixer as specified by the manufacturer. Do not use the material placed in the yield box in the deck.
F.Placing, Curing, and Finishing.
1.General.
a.Surface Preparation. Dry the deck surface, without the use of an open flame. Evenly and thoroughly coat all vertical and horizontal surfaces with a bonding grout using a brush, broom or sprayer system. Do not allow the bonding grout to dry before covering with new concrete. Place and cure deck concrete prior to placing overlay concrete.
b.Weather Requirements. Place deck concrete and overlay concrete when the ambient air temperature is 45°F and rising and below 80°F.
c.Curing Deck and Overlay Concrete. Use a curing period of at least 5 days and maintain the temperature of the concrete above 55°F during the curing period. Place a double thickness of burlap over the concrete within 15 minutes of the screed passing over the concrete. If the wet cure is not applied within 15 minutes of the passing of the finishing equipment, remove and replace the affected concrete. Use a work bridge to place burlap without marring the concrete. Prewet the burlap before placement and keep the burlap continuously moist for the duration of the curing period. Burlap may not be covered by other materials. Do not perform work or allow vehicles and equipment on the concrete during the curing period. 305 If enclosures are used to maintain curing temperatures, heat the enclosure with an electric heater or properly vented combustible heater. Before removing the enclosure, decrease the concrete’s surface temperature to the air temperature at a rate not to exceed 15°F per hour. If concrete is exposed to air temperatures below freezing during the curing period, the Engineer and the Department’s Bridge Division will perform an evaluation of the in- place concrete to determine serviceabili ty. The results of the evaluation may require remedial action up to and including removal of affected material. Perform remedial action at no additional cost to the Department.
2.Deck Concrete.
a.General. Use mixing equipment that meets Section 155.03, “Mixers” . Fill up removal areas to the bottom of the Class 1 or 1H removal. Strike off concrete at the bottom of the Class 1 or 1H removal . Leave the top of the deck concrete surface rough. If the deck conc rete placement is less than 1 inch in depth, place deck concrete with overlay concrete, using the material specified in Section 650.03 C, “Overlay Concrete” .
b.Full Depth. If removal is full depth, provide forms to facilitate placement of new concrete. Leave the underside of the deck with a neat and smooth appearance.
3.Overlay Concrete. Use mixing equipment that meets Section 155.03 C, “Mobile Mixers” . Before concrete placement, move the finishing machine across the rails to check and adjust the screed to ensure proper concrete overlay thickness. Consolidate the concrete and screed to final grade. Complete placement before September 15 unless preauthorized by the Br idge Engineer. Place overlay concrete in one operation leaving no transverse construction joint. After machine finishing is completed, hand finish with a wood float to produce a tight, uniform surface. Seal all vertical joints by painting the joint with a thinned grout prior to placing overlay concrete.
G.Surface Tolerances. After the concrete has cured, the Engineer will test the bridge deck and approach slabs or adjacent pavement, if applicable, for surface irregularities with a 10 foot straightedge. The Engineer will check the profile by performing the following: 306 “Check the profile using a 10 foot straightedge oriented in the longitudinal direction and starting at one end of the deck, move the straightedge transversely across the deck to the other edge with constant contact with the deck. Repeat this process in 5 foot intervals from one end of the deck to the other. Check the cross slope using the 10 foot straightedge oriented in the transverse direction and starting at one end of the deck, move the straightedge longitudinally from one end of the deck to the other end with constant contact with the deck. Repeat this process in 5 foot intervals from one side of the deck to the other.” Grind areas with a deviation greater than 1/8 inch, but less than or equal to 1/2 inch, until the deviation is 1/8 inch or less. The Engineer will apply a contract price reduction as specified in Section 650.06 B, “Surface Tolerance”. The Engineer will make a serviceability determination as specified in Section 105.07, “Conformance with the Contract Requirements” for any deviations greater than 1/2 inch.
H.Grooving. Perform grooving according to Section 602.04 D.3, “Deck and Approach Slab Grooving” .
I.Sealant. Apply a silicone sealant that meets the requirements of Section 826.02 B.1, “Sealant” to the joint where the deck overlay meets the barrier.
J.Penetrating Water Repellent Treatment . After grooving operation is complete and the silicone sealant is applied, apply penetrating water repellent solution that meets the requirements of Section 822, “Penetrating Water Repellent” a minimum of 21 days after placement of the concrete deck overlay according to Section 602.04 J, “Penetrating Water Repellent Treatment” .
650.05 Method of Measurement
The Engineer will measure as specified in Section 109.01, “Measurement of Quantities” and as follows:
A.Class 2-A Removal. Class 2 -A removal is paid for along the upper bar in the top mat of reinforcing only. If a bar that is identified for 2-A is in an area that becomes Class 3 or Class 4, it will not be paid for as 2-A removal.
B.Overlay Concrete.
1.General. The Engineer will measure overlay concrete at plan quantity unless it is the only concrete material placed due to the thickness requirement specified in “General” . In that instance, the Engineer will measure overlay concrete based on Section
650.05 B.2, “Yield Box Method” .
2.Yield Box Method. The Engineer will measure overlay concrete based on the mobile mixer count and the yield box. The Engineer will obtain counter readings from the mixer before and after each placement and multiply the readings by the meter count determined by the yield test, to determine the concrete quantity . The Engineer will deduct was te concrete from the measured quantity. The Contractor and Engineer will agree upon the amount of waste, including the material used in the yield test, at the end of each day.
650.06 Basis of Payment
A.General. Pay Item Pay Unit Deck Concrete Cubic Yard Overlay Concrete Cubic Yard Class 1 Removal Square Yard Class 2 Removal Square Yard Class 2 -A Removal Linear Foot Class 3 Removal Square Yard Class 4 Removal Square Yard Class 1H Removal Square Yard Class 2H Removal Square Yard Class 3H Removal Square Yard Such payment is full compensation for furnishing all materials, equipment, labor, and incidentals to complete the work as specified.
B.Surface Tolerance. The Engineer will process a contract price adjustment for overlay concrete based on the surface tolerance measurements determined in Section 650.04 G, “Surface Tolerances” . The amount of the contract price adjustment will be determined by multiplying the contract unit price for “Overlay Concrete” by the area ground, measured in square yards, by the appropriate Contract Price Reduction Factor in Table 650-02 . Table 650-02 Deviation Contract Price Reduction Factor > 1/8 inch and ≤ 1/4 inch 0.6% > 1/4 inch and ≤ 1/2 inch 1.8 % Section 702 308 SECTION 702 MOBILIZATION
702.01 Description
Mobilization consists of costs incurred for preparatory work and operations that must be performed before beginning work on the project site.
702.02 Equipment
Reserved.
702.03 Materials
Reserved.
702.04 Construction Requirements
Prepare and move personnel, equipment, and materials to project site.
702.05 Method of Measurement
The Engineer will measure as specified in Section 109.01, “Measurement of Quantities”.
702.06 Basis of Payment
Payment for mobilization will be based on Table 702-01: Table 702-01 Original Contract Amount Earned Payment will be the Lesser of: Mobilization Bid Amount Original Contract Amount 5% 25% 2.5% 10% 50% 5.0% 50% 100% 7.5% 75% 100% 10.0% Upon completion of all work on the project, the Department will make payment for any amount bid for Mobilization in excess of 10 percent of the original Contract amount. Such payment is full compensation for furnishing all materials, equipment, labor, and incidentals to complete the work as specified. Pay Item Pay Unit Mobilization Lump Sum
Source: North Dakota Standard Specifications for Road and Bridge Construction, 2022 Edition. Pages 335–342 of 550.