708PNEUMATICALLY PLACED MORTAR

708.01Description

This work shall consist of preparing stone, concrete, or other surfaces for and the pneumatic application of mortar as a plain or reinforced coating in accordance with these specifications and as shown on the plans or as directed.

MATERIALS

708.02Materials 10

Materials shall be in acco rdance with the following:

Deformed and Smooth Steel WWR ............................. 910.01(b)5 Fine Aggregate ............................................................ 904.02(d) Fly Ash ........................................................................ 901.02 Portland Ceme nt .......................................................... 901.01(b) Water ........................................................................... 913.01

WWR shall consist of wire, size W 1 or approximately No. 12 gauge or larger, spaced and welded at intervals greater than or equal to 2 in., and no greater than 4 in. 20

CONSTRUCTION REQUIREMENTS

708.03Preparing Surface

The surface of all steel to be covered shall be thoroughly cleaned of all paint, rust, grease, dirt, or other foreign materials. All loose or defective portions of masonry to be covered shall be removed and the surface thus exposed cleaned. The use of a sand blast as an aid in cleaning any surface may be required.

708.04Reinforcement 30

If WWR is required, it shall be cut into sheets of the proper sizes and bent carefully over a template so that the mesh closely follows the outline of the member to be covered. It shall be attached to such members at intervals of not to exceed 2 ft.

When feasible, the mesh shall parallel the surface of steel members 3/4 in. out from the face. Where sheets meet, they shall lap at least 4 in. and shall be fastened together securely.

WWR shall be used in all areas where the thickness of the mortar exceeds 3 in. and if the present steel rein forcement is exposed after the disintegrated concrete has 40 been removed. WWR shall be fastened to the concrete masonry with 1/4 in. machine bolts screwed into lead anchors driven into holes drilled into the concrete, or by pins or nails shot into the concrete by an impact gun. Such bolts or pins shall be spaced on 8 in. centers in each direction and shall be of sufficient length to space the WWR approximately 2 in. from the surface being repaired. Where WWR can be fastened to the reinforcing bars, the bolts, pins, or nails may be omitted.

708.04

708.05Proportioning and Mixing

The dry mixture shall consist of 1 part portland cement to 3 parts sand. The cement and sand shall be dry mixed in an approve d proportioning plant or in batch boxes. 50 Measurement may be by volume or weight. Before placing the proportioned materials in the hopper of the application gun, all lumps 1/4 in. or over shall be removed by screening.

708.06Placing Mortar

This work shall be done only by experienced personnel. No one operating the nozzle will be deemed experienced unless th ey have satisfactorily completed similar work on other structures of like type.

Just prior to placing mortar, the su rface shall be washed with water and 60 compressed air. The mortar shall be placed on a wet surface.

The equipment for placing the mortar sh all be operated in accordance with the recommendations of the manufacturer.

When shooting any surface, the nozzle shall be held at such distance and in such position that the flowing stream of material impinges, as nearly as possible, at right angles to the surface being covered. All deposits of loose sand shall be removed. Shooting shall start on those areas where th e greatest thickness is required. Mortar shall not be applied more than 2 in. thick in one operation. Where a finished thickness 70 of more than 2 in. is required, it shall be obtained in successive operations and enough time allowed to enable the previous layer to set.

During application, the required thickness shall be maintained by shooting strips. A full thickness shall be obtained over thin edges of steel.

After completion of a section of coating, all high spots shall be cut off with a sharp trowel or screeded to a true plane as determined by the shooting strips. Finished edges shall be true and even.

708.07Finishing

After all surfaces have been brought to the required contour and smoothness, they shall be finished with a flash coat approximately 1/8 in. thick. This coat shall produce a uniform color and finish and an ap proved appearance on all exposed surfaces. Proportioning and mixing of the flash coat shall be in accordance with 708.05 except white portland cement shall be used. Before placing the proportioned materials in the hopper of the application gun, all lumps 1/8 in. or larger shall be removed by screening. No less than one bag of the white cement to each 300 sq ft of surface shall be used.

Immediately after completion, the surface shall be covered with wet burlap or wet 90 cotton mats and these shall be kept wet for at least 96 h. No mortar shall be placed when the air temperature is below 50°F or against a surface which contains frost. After 708.05

the work has been completed, all rebound and other debris shall be removed from the work.

708.08Method of Measurement

Pneumatically placed mortar will be measured by the square foot, complete in place. The area measured will be the actual finished surface. WWR, where used, will be measured by the square foot, complete in place.

708.09Basis of Payment

The accepted quantities of pneumatically placed mortar and WWR will be paid for at the contract unit price per square foot, complete in place.

Payment will be made under:

Pay Item Pay Unit Symbol

Pneumatically Placed Mortar..................................................... SFT Welded Steel Wire Reinforcement ............................................ SFT 110

The areas where loose or defective portions of masonry exceed an average of 4 in. in depth will be paid for at a price to be determined by multiplying the contract unit price for pneumatically placed mortar, respectively, by the factors as follows:

than 4 in. but less than 6 in. ................................................ 1.25

than or equal to 6 in. but less than 8 in. .............................. 1.50 120

than or equal to 8 in. but less than 10 in. ............................ 1.75

than or equal to 10 in. but less than 12 in. .......................... 2.00

to 12 in., the work shall be done as extra work. Payment will be made in accordance with 104.03. 130

708.09