Section 560 — Removal of Concrete By Hydrodemolition

Description

560.01This work consists of removing concrete with high- pressure water jets.

Material

560.02Conform to the following Subsection: Water for construction 725.01(c)

Construction Requirements

560.03Submittals. At least 30 days before starting hydrodemolition work, submit the following according to Subsection 104.06:

(a)Sequence and schedule of work;

(b)Concrete removal procedures; and

(c)List of equipment to be used.

560.04General. Provide water required to operate the hydrodemolition equipment. Protect adjacent property from dislodged concrete during operations. Construct debris shields to prevent debris and wastewater from entering waterways, travel lanes open to p ublic traffic, or areas designated not to be disturbed. Dispose of wastewater and debris according to Subsection 203.07.

560.05Equipment.

(a)Hydrodemolition system. Provide a self -propelled and completely programmable hydrode molition system designed for concrete removal.

(b)Vacuum system. Provide a vacuum system equipped with:

(1)Fugitive dust control devices that can remov e wet debris and water in the same pass; and

(2)A pressurized washing system that can clean the concrete surface d uring the vacuum operation to dislodge debris and slurry.

560.06Calibration. Calibrate equipment to remove concrete to the required dimensions before starting hydrodemolition production work. If hydrodemolition equipment cannot remove concrete to the required dimensions, remove equipment and provide another hydrodemolition system. Verify operation of equipment at the start of each day on an area of representative concrete designated by the CO before starting operations. Recalibrate during the work if concrete conditions, including degree of deterioration and strength, or dimensions change. Record the following settings at each calibration and notify the CO:

(a)Water pressure gauge;

(b)Water usage in gallons per minute;

(c)Machine staging control (step) – feet per minute forward travel;

(d)Nozzle size;

(e)Nozzle speed (revolutions per minute);

(f)Transverse nozzle travel speed. Only applicable if hydrodemolition nozzle is not fixed and moves transversely on a track between stops before staging to the next step. Report transverse nozzle travel speed in feet per second; and

(g)Effective pass width of hydrodemolition unit. Effective pass width is defined as the width of hydrodemolition that has uniform pressure, water, and dwell time per machine staging control (step). Report effective width in feet.

560.07Concrete Removal. Remove concrete as follows:

(a)Concrete scarification. Scarify to the depth shown in the plans. If no depth is shown, remove at least ¼ inch of material. Clean the surface by an approved method of water blasting with 7000 pounds per square inch minimum pressure until sound concrete is exposed.

(b)Concrete removal. Remove concrete to the depth shown in the plans or down to sound concrete. Provide at least 1 inch below the bottom of the exposed reinforcing steel. Do not damage remaining sound concrete or reinforcing steel. If the bond between existing concrete and reinforcing steel is destroyed, remove the concrete adjacent to the reinforcing steel to a depth that allows new concrete to bond to the reinforcing stee l. Remove loose and unsound concrete resulting from the hydrodemolition operations below the minimum depth. Verify depth of concrete removal at least every 30 feet along the cutting path. In areas inaccessible to the hydrodemolition equipment, use approved hand- held water blasting equipment or power -driven hand tools such as jackhammers, mechanical chipping tools, or chipping hammers. Do not use jackhammers heavier than nominal 30- pound class or chipping hammers heavier than 15-pound class. Operate mechanic ally driven tools at a maximum angle of 45 degrees from the concrete surface. If necessary, use hand tools such as hammers and chisels to remove the final particles of concrete to achieve the required depth. Leave a rough surface after the concrete is remo ved. Immediately remove residue, water, dust, and concrete to prevent rebonding to the surface or reinforcing steel.

560.08Reinforcing Steel. Do not cut or damage reinforcing steel designated to remain. Inspect the reinforcing steel with the CO after th e concrete has been removed. Clean exposed reinforcing steel of rust, loose and rebounded material, and other contaminants that may inhibit bonding to new concrete. Tie new reinforcing steel to the existing reinforcing steel if more than 10 percent of its section is lost. If the deteriorated portion of the reinforcing steel is closer to the edge of the patch than the overlap distance designated in the plans, extend the limits of the patch to provide the required overlap distance with acceptable reinforcing steel. Provide a minimum 2 -inch clearance between the ends of new reinforcing steel and the existing slab face. Match the number, type, and spacing of the new reinforc ing steel to the existing reinforcing steel.

560.09Acceptance. Removal of concrete by hydrodemolition will be evaluated under Subsections 106.02 and 106.04.

Measurement

560.10Measure the Section 560 pay items listed in the bid schedule according to Subsection 109.02 .

Payment

560.11The accepted quantities will be paid at the contract price per unit of measurement for the Section 560 pay items listed in the bid schedule. Payment will be full compensation for the work prescribed in this Section. See Subsection 109.05 .