The following method has been adopted by the New York Central Railroad for giving a good finish to exposed concrete surfaces:

The forms of 2-inch tongued-and-grooved pine were coated with soft soap, all openings in the joints of the forms being filled with hard soap. The concrete was then deposited, and, as it progressed, was drawn back from the face with a square-pointed shovel, and 1: 2 mortar poured in along the forms. When the forms were removed, and while the concrete was green, the surface was rubbed, with a circular motion, with pieces of white firebrick, or brick composed of one part cement and one part sand. The surface was then dampened and painted with a 1: 1 grout, rubbed in, and finished with a wooden float, leaving a smooth and hard surface when dry.

The following method of placing mortar facing has been found very satisfactory, and has been adopted very extensively in the last few years: A sheet-iron plate 6 or 8 inches wide and about 5 or 6 feet long, has riveted across it on one side angles of 3/4-inch size, or such other size as may be necessary to give the desired thickness of mortar facing, these angles being spaced about two feet apart (Fig 116). In operation, the ribs of the angles are placed against the forms; and the space between the plate and forms is filled with mortar, which is mixed in small batches, and thoroughly tamped. The concrete back-filling is then placed; the mould is withdrawn; and the facing and backfilling are rammed together. The mortar facing is mixed in the proportion of one part cement, to 1, 2, or 3 parts sand; usually a 1:2 mixture is employed, mixed wet and in small batches as used. As mortar facing shows the roughness of the forms more readily than concrete does, care is required in constructing, to secure a smooth finish. When the forms are removed, the face may be treated either in the manner already described, or according to the following method taken from the "Proceedings" of the American Railway Engineering and Maintenance of Way Association:

Fig. 116. Mould for Mortar Facing.

Fig. 116. Mould for Mortar Facing.

"After the forms are removed, any small cavities or openings in the concrete shall be filled with mortar, if necessary. Any ridges due to cracks or joints in the lumber shall be rubbed down; the entire face shall be washed with a thin grout of the consistency of whitewash, mixed in the proportion of 1 part cement to 2 parts of sand. The wash shall be applied with a brush."