423 PNEUMATICALLY APPLIED MORTAR

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423.01 DESCRIPTION.
Remove deteriorated concrete, and furnish and place pneumatically applied mortar.
423.02 MATERIALS.
Curing Materials       902.07
Reinforcing Steel       908.01, 908.02, and 908.08
Anchor Bolts       909.06
Water       921.01
Use Type II cement meeting 902.03, and furnish in the original 94 lb paper sacks supplied from the cement manufacturer.
Use fine aggregate meeting the Fine Aggregate-Portland Cement Concrete requirements of 901.01. Ensure that the maximum moisture content does not exceed 6 percent by weight.
Pneumatically applied mortar shall have a 28 day compressive strength of 5000 to 9000 psi. Ensure that all mixes are approved prior to starting work.
423.02.01 Test Panels. When specified, prepare and cure test panels of various mix combinations, admixtures, and materials. Prepare one test panel for every 100 ft3 of mortar in place. Prepare additional test panels as directed. Panels shall be 36 in. square and 8 in. deep. Include the same reinforcing as the structure in at least half of each panel. A separate panel shall be fabricated by each application crew using the equipment for each mix design, and in each shooting position encountered.
Core each test panel and deliver the cores to the LaboratoryThe testing laboratory of the State Highway Administration (or other Administrations) or any other testing laboratory designated by the procurement officer. for testing. Cores shall have a diameter of at least 4 in. and be at least 8 in. long. Cores will be tested in compression at 7, 14, and 28 days. Core strength correction will be per T 24.
The EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him. will examine the cut surface of each specimen. Expose additional surfaces by sawing or breaking the panel when necessary to check soundness and uniformity of the material. All cut or broken surfaces that are not dense and free from lamination and sand pockets will be rejected.
423.03 CONSTRUCTION.
Submit the proposed methods of protecting the public against injury and damage from demolition operations. When required protective shields shall meet 405.03.01.
Provide safe access to all areas of the existing structure to be repaired. Prior to the start of any repair work, conduct a thorough inspection in the presence of the EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him.. The purpose of this inspection will be to identify the location and extent of concrete deterioration and repair. The EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him. will establish the extent of removal and determine when sound concrete is encountered.
Restrictions. Wait at least 72 hours after completing repairs to a section of a stringer or pier before chipping on any section that has a common side or point.
If at any time an area is identified as having deteriorated concrete beyond the following limits, immediately stop work in these areas. The EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him. will notify the Office of StructuresBridges, culverts, catch basins, drop inlets, retaining walls, cribbing, manholes, end walls, buildings, sewers, service pipes, underdrains, foundation drains, steps, fences, and other features that may be encountered in the work and not otherwise classified.. Do not resume work until after obtaining approval from the Office of StructuresBridges, culverts, catch basins, drop inlets, retaining walls, cribbing, manholes, end walls, buildings, sewers, service pipes, underdrains, foundation drains, steps, fences, and other features that may be encountered in the work and not otherwise classified.:
(a) More than 6 in. beyond the original finish surface.
(b) More than 3 in. beyond the reinforcing steel.
(c) More than 1 in. beneath the bearing.
423.03.01 EquipmentAll machinery, tools, and apparatus necessary for the proper construction and acceptable completion of the work, together with the necessary supplies for upkeep and maintenance.. Ensure that all equipment is calibrated and capable of thoroughly mixing all material.
Use a self-cleaning mixer capable of discharging all mixed material without any carry over from one batch to the next. Clean the mixing equipment at least once a day.
Ensure that the air compressor has ample capacity to maintain a supply of clean, dry air adequate to provide the required nozzle velocity for all parts of the work, while simultaneously operating a blowpipe for cleaning away rebound.
Ensure that the air and water pressure are constant and do not pulsate.
423.03.02 Storage. Store and handle cement as specified in 902.01. Store sand to prevent segregation or contamination of the material.
Store all reinforcing bundles at the site on suitable blocking or platforms at least 4 in. above all type of surfaces and vegetation. Keep the reinforcing free of dirt, oil, grease, paint, and other foreign matter.
423.03.03 Surface Preparation. Remove deteriorated areas of concrete to sound concrete with no more than a 30 lb chipping hammer. Continue chipping to at least 1 in. behind the reinforcing steel and until there is no sudden change in the depth of the cavity. Provide a perimeter having a shoulder perpendicular to the surface of the structure for a depth of at least 1 in.
After the EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him. has determined that it is sound, abrasive blast the cavity surface. Just prior to applying the mortar, thoroughly clean all surfaces followed by wetting and damp drying.
Contain all blast waste and loose concrete, and promptly remove it to an approved disposal site. Keep blast waste and loose concrete out of waterways.
423.03.04 Reinforcement. If sound concrete is encountered before the reinforcing steel is exposed, remove sound concrete to a depth of 1 in. behind the reinforcing steel. If sound concrete is found within 3-1/2 in. of the proposed finished surface, stop the removal and dowel additional No. 4 reinforcing bars installed at 12 in. center to center horizontally and vertically, 2 in. clear of proposed finished surface. Dowel per Section 406 except use any type grout specified in 902.11.
Abrasive blast all exposed existing reinforcing steel that will be incorporated in the new work to a near white finish to remove all rust, dirt, scale, and loose concrete. Cut out reinforcing bars that have lost 20 percent or more of their original dimension. Weld new bars in their place. Dual bars of equivalent or greater section may be used. Weld new reinforcing steel to existing reinforcing steel as specified. The EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him. will establish if reinforcing steel is to be reused or replaced.
In addition to the reinforcing steel, reinforce repaired areas with wire mesh.
For anchoring reinforcing to masonry surfaces, set at least 3/8 in. diameter expansion bolts in drilled holes, or set plain round No. 4 bars in approved dry packed mortar tightly driven in drilled holes. Ensure that drilled holes are at least 3 in. deep. All bolts and bars shall be set in solid masonry (not in mortar, joints, or cracks) and have heads or hooks on their outer ends. Where approved, mesh may be wired to existing reinforcing without the use of expansion bolts.
Cut mesh in sheets of proper size. Bend the separate sheets over templates to follow the outlines of the member or surface to be covered. Securely hold in a uniform position by tying to the bolts or bars with 14 gauge black annealed wire. Space ties at no more than 12 in.
Overlap adjacent sheets of mesh at least two squares. Tie them together with a 14 gauge black annealed wire at intervals not exceeding 18 in.
423.03.05 Guides. Use sufficient guides to obtain the full thickness of mortar specified and to ensure uniform and straight lines.
423.03.06 Mixing and Screening. Uniformly dry mix the cement and sand in a batch mixing machine. Discard mixed materials not applied within one hour. After the materials are dry mixed and before being charged into the placing machine, pass the mixture through a 3/8 in. screen.
423.03.07 Application. Build up each layer by several passes of the nozzle over the working area. Ensure that the mixture emerges in a steady, uninterrupted flow. Should the flow become intermittent for any cause, direct it away from the work until it becomes constant. Hold the nozzle perpendicular to the application surface, and at a distance from the work as required to obtain best results for the conditions. When shooting through reinforcement, hold the nozzle at a slight angle from perpendicular to permit better encasement.
For vertical surfaces, begin application at the bottom. Ensure that the first layer completely embeds the reinforcement.
Do not work rebound back into the construction, nor salvage it to be included in later batches.
Do not permit rebound and overspray to fall into waterways. Dispose of this material in an approved disposal site at no additional cost to the AdministrationShall mean any one of the Administrations within the Maryland Department of Transportation, as listed in GP 1.02..
When a layer of pneumatically applied mortar is to be covered by a succeeding layer, ensure that it has taken its initial set prior to proceeding. Then remove all laitance, loose material, and rebound by brooming. Use abrasive blasting to remove any laitance that has taken final set, and clean the surface with an air water jet. In addition, the EngineerAny person designated by the Administrator or the procurement officer, acting directly or through his duly authorized representative, such representative acting within the scope of the particular duties assigned to him or of the authority given him. will sound the surface with a hammer for hollow sounding areas that indicate rebound pockets or lack of bond.
423.03.08 Curing and Cold Weather Protection. Section 420. Keep mortar continuously wet for at least seven days after application. Liquid membrane forming compound will be permitted with prior approval.
423.03.09 Finishing. Finish the area of repair to match the existing structure.
423.04 MEASUREMENT AND PAYMENT.
Pneumatically Applied Mortar will be measured and paid for at the Contract unit price per cubic foot of mortar in place. The payment will be full compensation for inspections, removal of existing concrete, abrasive blasting, and furnishing all cement, sand, water, test panels, drilled holes, reinforcing bars and wire mesh, mortar, expansion bolts, cores, storage, and for all material, labor, equipment, tools, and incidentals necessary to complete the work.