Section 571 — Ultra-High Performance Concrete

Description

571.01This work consists of providing, placing, finishing, and curing ultra -high performance concrete (UHPC).

Material

571.02Conform to the following Subsections: Curing material 711.01 Reinforcing fibers 711.06 Sealants, fillers, and seals 712.01 Water for cementitious materials 725.01(a)

Construction Requirements

571.03Qualifications. A t least 30 days before starting UHPC work, submit the following for approval:

(a)On-site technical representative. A résumé describing experience supervising on-site UHPC related activities including mixing, placement, and process control of the UHPC test section and UHPC production pours; and

(b)UHPC manufacturer. Documentation describing at least 3 years ’ experience on UHPC projects of similar size and scope. Include project names, construction dates, locations, and contact information for the project owners.

571.04Composition (Ultra- High Performance Concrete Mix Design). Submit written concrete mix design and test results at least 14 days before test section. Include the following:

(a)Material certifications;

(b)Mass of mixing water per cubic yard of concrete; and

(c)Test results from within the last 12 months . Produce U HPC mixtures that conform to Table 571-1 and are suitable for the application shown in the plans. 626 Table 571-1

Properties of UHPC

Property Test Method Performance

Compressive strength ASTM C1856 ≥ 13,000 psi at 4 days ≥ 18,000 psi at 28 days Effective cracking strength AASHTO T 397 ≥ 1100 psi Peak tensile strength AASHTO T 397 ≥ 1250 psi Direct tension bond strength ASTM C1583 100% failure in substrate concrete Modulus of elasticity ASTM C1856 ≥ 6500 ksi Long- term drying shrinkage ASTM C1856 ≤ 800 microstrains at 28 days Chloride ion penetrability ASTM C1856 ≤ 250 coulombs Abrasion resistance ASTM C1856 < 0.025 oz. lost Freeze thaw resistance ASTM C1856 RDME > 95% Flow(1) ASTM C1856 Between 7 to 10 in ASR(2) ASTM C1567 ≤ 0.10 percent at 16 days after casting

(1)Flow property is only applicable to closure pour application.

(2)Performed on approved mix design mass percent combinations.

571.05Placement Plan. At least 14 days before starting the test section, submit the following according to Subsection 104.06:

(a)Responsible personnel and hierarchy;

(b)Type, size, location, and number of equipment;

(c)QC of batch proportions. Include dry ingredients, fibers, water, and admixtures;

(d)QC of mixing time and batch times;

(e)Batch procedure sequence;

(f)Test section construction sequence and drawings;

(g)Form work including materials and removal;

(h)Placement procedure. Include surface preparation of existing concrete surfaces, prewetting of existing concrete surfaces to a saturated surface dry (SSD) condition before placement of UHPC, handling, transporting, placing, finishing, curing protection, and overall sequencing of placement procedure. Include provisions for acceptable ambient conditions and batch temperatures and corrective measures as required;

(i)Threshold limits for ambient temperature, ambient relative humidity, batch consistency, batch temperature, batch times, and relative corrective action;

(j)Spill prevention and cleanup plan;

(k)Cold weather placement plan including if cold weather placement is expected during placement of UHPC;

(l)Contingency plan including contingency procedures for interruption of operations by weathe r, equipment malfunctions, or other issues; and 627 (m) Sampling and testing procedures.

571.06Production Start- up Procedures.

(a)Preparatory phase meeting. Conduct a pre -UHPC preparatory phase meeting according to Subsection 153.06(a) at least 7 days before the start of UHPC operations . In addition, be prepared to discuss the approved Placement Plan.

(b)Test section. Complete a test section at least 30 days before production according to the a pproved Placement Plan. For overlays, bridge decks, and other flatwork, construct a 9- by 9- foot test section at the same thickness as the production placement. For closure pours, construct a 9- foot-long test section. For other structural elements, constru ct a 3 - by 3- by 3- foot test section. Use the approved UHPC mix design and the same methods of handling, placing, finishing, and curing intended for production placement. Sample and test according to Table 571-2. Construct the test section formwork according to Subsection 571.14 and as shown in the plans. Construct the test section to represent prepared surfaces and reinforcement bars in the production placement and the steepest grade and cross slop e of the finished surface. Complete the test section at the project site in a location that allows the CO access to all sides. Construct the test section in the presence of the manufacturer’ s technical representative and the CO. Use the same staff, equipment, forming, mixing, placing, and curing procedures as the production pour. Include all steps necessary to replicate a production UHPC pour. After the UHPC has taken its initial set, strip the forms to allow the CO to evaluate the test section. Demonstrate the placement plan and methods for surface preparation and compliance with temperature and finishing requirements. Verify fresh and hardened concrete properties. Repeat the test section process until an acceptable test section is produced. If desired results are not achieved as determined by the CO, modify the process accordingly and complete another UHPC test section. Continue until a UHPC test section is completed successfully. Document the procedures, tools, forms, and any other equipment im plemented in this successful completion. Use the same in completing production UHPC pours. Provide a revised Placement Plan as directed before production UHPC pours based on the test section results.

571.07Handling and Storing Material. Handle and store material to ensure uniformity of mixture at time of use and to prevent loss of physical and mechanical properties, according to the manufacturer’s recommendations. Do not use UHPC materials containing evidence of moisture contamination.

571.08Batching. B atch the concrete according to the manufacturer’s recommendations.

571.09Equipment. Do not use equipment with aluminum parts that contact the UHPC. 628 (a) Mixers. Provide mixers capable of uniformly mixing the UHPC, according to the manufacturer’s recommendations. Provide documentation that mixers are rated for use with UHPC mixtures. Provide at least two portable mixing units.

(b)Vibrating screed. When constructing UHPC overlays, use an approved power -driven finishing machine equipped w ith a screed that oscillates in a transverse direction.

571.10Mixing. Ensure the manufacturer’s representative is present during all UHPC mixing. Maintain the mixture at an ambient temperature below 85 °F or according to the manufacturer’s recommendation s. Ice may be added to the mix if recommended by the manufacturer ’s representative. Mix the concrete in a portable mixer according to the manufacturer’s recommendations. If multiple portable mixers are used, stagger the batching operations so that a consta nt supply of fresh concrete is available for placement. Operate equipment within the manufacturer’s recommended capacity. Add UHPC materials according to the manufacturer’s recommendations. Produce concrete of uniform consistency. Remove the contents of a mixed batch before a succeeding batch is charged into the mixer. Regulate the delivery of the UHPC to the site so that the placing and finishing operations can proceed at a uniform rate.

571.11Quality Control of Mix. Submit and follow a QCP according to Section 153. Mix and place UHPC according to the manufacturer’s recommendations. Designate at least one laborer to monitor the UHPC placement for concrete leakage. Identify materials to be kept on hand and procedures to be implemented to stop any UHPC leaking from forms.

571.12Temperature and Weather Conditions. Protect the UHPC from precipitation during and after placement. Maintain the temperature of the UHPC mixture before placement according to the manufacturer’s recom mendations. During curing, maintain the temperature of the UHPC’s outermost surfaces according to the manufacturer’s recommendations or the following:

(a)Cold weather. Conform to Subsection 552.07(a) , except as follows:

(1)Place UHPC when the ambient air temperature is 45 °F and rising, and the substrate temperature is 40 °F and rising;

(2)Maintain a minimum concrete temperature of 50 °F during curing. Protect UHPC until the concrete minimum 4 -day compressive strength is attained ; and

(3)Remove protection only when the average wind speed is less than 10 miles per hour as measured 3 feet from the UHPC surface.

(b)Hot weather. Conform to Subsection 552.07(b) , except as follows:

(1)Place UHPC when the ambient air temperature is less than 85 °F, and the substrate temperature is less than 80 °F; and 629 (2) Do not remove curing material until the minimum 4 -day compressive strength is attaine d and the average wind speed is less than 10 miles per hour as measured 3 feet from the UHPC surface.

(c)Evaporation. Conform to Subsection 552.07(c) .

(d)Precipitation. Protect UHPC from precipitation during and after placement.

571.13Surface Preparation.

(a)UHPC overlay. Conform to Subsection 569.06(b) .

(b)UHPC closure pour and other structural elements. Sandblast concrete surfaces to exposed aggregate surface finish. Clean concrete surfaces by flushing with clean water from a high- pressure water jet or compressed air. Clean exposed steel. Remov e any dirt, rust, oil, grease, coating material, or other contaminants which may inhibit UHPC bonding. If compressed air is used, provide a filter to deliver oil- free compressed air.

571.14Formwork. Design and construct falsework, shoring, and bracing according to Section 562. Provide watertight formwork with a non- absorbing finish. Use an approved form release agent to produce a minimum of staining, air holes, and hydration discoloration. Fasten formwork to existing concrete using adhesives or other approved methods that do not damage the existing concrete. Do not use drilling, nailing, or post anchor systems to fasten temporary works or formwork to existing concrete. Provide formwork according to the manufacturer’s recommendations for construction of concrete elements.

571.15Placing Ultra- High Performance Concrete.

(a)General. Ensure the manufacturer’s representative is present during handling and placing of the UHPC. Prepare surfaces according to Subsection 571.13. Monitor the UHPC handling and placement for concrete leakage.

(b)Sequence of placement. Sequence UHPC placement according to the construction stages shown in the plans. Finish placing UHPC in each overlay lane or closure pour before starting placement in successive overlay lanes or closure pours. Thoroughly moisten the forms and wet existing concrete surfaces to an SSD condition immediately before placing UHPC. Remove excess water by approved methods before placing UHPC. Do not place concrete until the forms have been inspected and approved. (c) Placing methods. Place UHPC according to the manufacturer’s recommendations. Handle and place concrete by methods that do not cause segregation and results in dense homogenous concrete that is free of voids. Do not pump UHPC unless it was demonstrated and approved in the test section. If ambient temperature during the UHPC placement is at least 7 °F greater than during the test section, perform another test section at the higher temperature according to Subsection 571.04. Cast UHPC continuously without interruption. Add UHPC behind the leading edge of the flow. Do not use cold joints unless shown in the plans. 630 For UHPC closure pours, place UHPC using chimneys, ports, or other approved equipment that maintain a positive head of material to the flowing UHPC, according to the manufacturer’ s recommendations. Provide equipment with a minimum discharge opening of 3 inches. Install chimneys, ports, or other a pproved equipment at the highest point of each joint and at intervals no more than 10 feet. Fill the joint from the low point. Maintain a continuous head of pressure sufficient to fill the joint to just beyond the next uphill chimney or port. Fill successi ve chimneys or ports in the same manner until UHPC emerges from the one placed at the highest point of the joint. Monitor UHPC for subsidence and maintain a positive head of material to the UHPC in all chimney or ports until the UHPC has taken initial set.

(d)Consolidation. Consolidate UHPC according to the manufacturer’s recommendations.

(e)Compressive strength. Remove and replace concrete represented by cylinders having a compressive strength less than 90 percent of the minimum 28 -day strength.

571.16Construction Joints. Do not use construction joints unless shown in the plans.

571.17Expansion and Contraction Joints. Provide expansion and contraction joints as shown in the plans. 571.18 Curing Ultra- High Performance Concrete. Start curing immediately after consolidation during placement operations. Apply a curing compound to the UHPC surface and cover the UHPC surface with waterproof plastic sheeting. Ensure the UHPC surface is continuously covered by the waterproof sheeting until the UHPC has attaine d the 4 -day minimum compressive strength shown in Table 571-1. Cure UHPC according to the manufacturer’s recommendations.

571.19Finishing Ultra -High Performance Concrete. Overfill the UHPC at least ½ inch. Perform diamond grinding of UHPC surfaces after the UHPC has attaine d the 4 -day minimum compressive strength shown in Table 571-1.

(a)UHPC overlay. Where UHPC is the final riding surface, diamond grind the entire top surface of the overlay in the direction parallel with the centerline to provide a uniform longitudinal corduroy grooved texture. Space fins ½ to ¾ inch on centers. Cut the grooves between ⅟ 16 inch and 3/16 inch wide and ⅟ 16 to 3/16 inch deep. Discontinue grooving 12 inches from curb face and provide a flat ground finish on the surface of gutters. For bridge decks, do not groove within 6 inches of joint blockouts and bridge ends. Check the entire surface parallel to the centerline with a 1 0-foot metal straightedge. Overlap the straightedge at least one-half of the length of the previous straight edge placement. Correct deviations more than ⅛ inch from the testing edge of the straightedge.

(b)UHPC closure pour. Diamond grind the top surface of the UHPC closure pour to match the existing grade and cross slope within ¼ inch. 631 571.20 Loads on New Ultra -High Performance Concrete Structures. Do not allow traffic or other loading, including construction loading, on UHPC decks until the deck concrete has attained the 4 -day compressive design strength and the finished surface (and diamond grinding) has been approved to allow vehicular traffic.

571.21Acceptance. See Table 571-2 for sampling, testing, and acceptance requirements. Material for UHPC will be evaluated under Subsections 106.02 and 106.03. Provide production certifications with each shipment of UHPC mat erial. UHPC mix properties will be evaluated under Subsections 106.02 and 106.04. Construction of UHPC will be evaluated under Subsections 106.02 and 106.04. Temporary works will be evaluated under Section 562.

Measurement

571.22Measure the Section 571 pay items listed in the bid schedule according to Subsection 109.02 and the following as applicable: When measuring UHPC by the cubic yard, measure in the structure. Do not measure test sections not incorporated in the work.

Payment

571.23The accepted quantities will be paid at the contract price per unit of measurement for the Section 571 pay items listed in the bid schedule. Payment will be full compensation for the work prescribed in this Section. See Subsec tion 109.05 . Table 571-2 Sampling, Testing, and Acceptance Requirements

Material or

Product

(Subsection) Type of

Acceptance

(Subsection) Characteristic Category Test Methods

Specifications Sampling

Frequency Point of

Sampling Split

Sample Reporting

Time Remarks

Source

UHPC Measured &

tested for conformance (106.04) Chloride ion penetrability(1) – ASTM C1856 1 per material type Source of material No 14 days minimum before test section – Production Start -up (Test Section)

UHPC Measured &

tested for conformance (106.04 ) Compressive strength(2) – ASTM C1856 1 set per test section Discharge stream at point of placement Yes Upon completing tests –

Effective

cracking strength – AASHTO T 397 " " No " –

Peak tensile

strength – AASHTO T 397 " " " " –

Direct tension

bond strength – ASTM C1583 " " " " –

Modulus of

elasticity(3) – ASTM C1856 " " " " –

Long- term

drying shrinkage – " " " " " – Abrasion – " " " " " –

Freeze thaw

resistance – " " " " " – Table 571- 2 (continued) Sampling, Testing, and Acceptance Requirements

Material or

Product

(Subsection) Type of

Acceptance

(Subsection) Characteristic Category Test Methods

Specifications Sampling

Frequency Point of

Sampling Split

Sample Reporting

Time Remarks

Production Start -up (Test Section) (continued)

UHPC Measured &

tested for conformance (106.04 ) Temperature – ASTM C1064 1 per batch Discharge stream at point of placement No Upon completing tests – Flow – ASTM C1856 " " – " –

Production

UHPC Statistical

(106.05) Compressive strength(2) II ASTM C1856 1 set per 30 yd3 but not less than 1 per day Discharge stream at point of placement Yes Upon completing tests –

UHPC Measured &

tested for conformance (106.04 ) Temperature – ASTM C1064 1 per batch " No Upon completing tests – Flow(4) – ASTM C1856 " " " " –

Surface

tolerance – Straightedge measurement,

Subsection

571.19Continuous after concrete has hardened Finished surface " 24 hours –

(1)Cast at least three, 4 - by 8- inch maximum chloride permeability cylinders per set and carefully transport the cylinders to the job site curing facility. A single maximum chloride permeability test result is the average result from three cylinders cast from the same lo ad.

(2)Cast at least six, 3- by 6- inch compressive strength cylinders per set and carefully transport the cylinders to the job site curing facility. Test compressive strength at 4 and 28 days. A single compressive strength test result is the average result from three cylinders cast from the same load.

(3)Cast at least one, 3 - by 6-inch modulus of elasticity cylinder per set and carefully transport the cylinder to the job site curing facility.

(4)Perform flow test only for UHPC closure pour.