Sand-Cement (Mortar) Bed. - Upon the concrete foundation shall be spread a layer of mortar 3/4 inch in thickness and made of one part of Portland Cement and three parts of sand. Only sufficient water shall be added to this mixture to insure a proper setting of the cement, the intention being to produce a granular mixture which may be raked to the desired grade. The mortar shall be thoroughly mixed and shall be spread in place on the foundation immediately in advance of the block laying to such a thickness that when the blocks are set and properly bedded in the mortar, their tops shall conform accurately to the finished grade of the roadway. The concrete foundation shall be cleaned and swept and shall be thoroughly dampened immediately in advance of placing the mortar bed. The mortar bed shall be struck by templates to a surface parallel to the grade and contour of the finished pavement.

Laying. - Upon the bed thus prepared, the blocks shall be carefully set with the fiber of the wood vertical, in straight parallel courses, leaving a space next the curb one (1) inch (or more if the Engineer shall direct) in width for an expansion joint. Strips of wood with wedges behind shall be used to keep the expansion joint even. The courses will usually be laid at right angles to the curb lines, but the Engineer will give directions for the angle to be used from time to time.

The blocks shall be laid close together on the prepared bed with joints not less than three-sixteenths (3/16) inch and not more than one-quarter (1/4) inch in width. If the blocks used are ordinary rectangular blocks without lugs or other provisions for spacing, no joint shall exceed one-eighth (1/8) inch in width.

Nothing but whole blocks shall be used, except in starting a course or in such other case as the Engineer may direct, and in no case shall less than one-third of a block be used in breaking joints. Closures shall be carefully cut and trimmed by experienced men. The portions of the blocks used for closures must be free from check or other fracture and the cut end must have a surface perpendicular to the top of the block and cut to the proper angle to give a close, neat joint.

Immediately after the pavement is laid the strips in the expansion joint shall be removed and the joint filled to a depth of one-half (1/2) inch with clean, dry, fine sand and then to an additional depth of one (1) inch with paving pitch as specified below. At the same time the entire surface of the pavement shall be swept clean and covered with a light layer of clean, fine, dry sand which shall be broomed into the joints so as to fill same to a depth of not less than one-quarter (1/4) nor more than one-half (1/2) inch. If too much sand is gotten into any of the joints, such places shall be taken up and repa'ved.

The blocks shall then be immediately rolled both parallel and diagonal to the curb, by a tandem roller of approximately five tons weight, until the surface is smooth and true to the grade and contour of the pavement.

The entire operation of block laying, sand filling and rolling must proceed in such rapid sequence that the rolling is completed before the mortar bed has set. If any of the mortar bed has set before the completion of the rolling, the blocks shall be taken up, the old mortar bed removed and the blocks repaved on a fresh mortar bed.

Pitch-Mastic Filler. -Immediately after the completion of the rolling, the joints between the blocks shall be filled with a pitch-mastic filler, complying with the following:

The mastic filler shall consist of a mixture of Paying Pitch of a quality hereinafter described and hot, dry sand of fineness hereinafter specified in the proportion of---------part pitch and---------part sand by volume, or as much sand up to that proportion as the pitch will carry.

The paving pitch shall be a straight run residue obtained from the distillation of coal tar. Its specific gravity at 77 degrees F. shall not be less than 1.22 nor more than 1.30. It shall have a melting point of not less than 135 degrees F. nor higher than 150 degrees F. by the cube method of testing, and shall have a free carbon content of not less than 20 per cent. nor more than 30 per cent.

On distilling 100 grams of the material, no distillate shall come over below 336 degrees F. (169 deg. C). On continuing the distillation to 600 degrees F. (315 deg. C.) not more than 15 per cent. of distillate shall come over, and the specific gravity of the entire distillate shall not be less than 1.03 at 60 degrees F. (15.5 deg. C).

The residue from the foregoing distillation shall have a melting point not greater than 165 degrees F. (74 deg. C.).

The sand shall be fine, clean and moderately sharp. All of it shall pass a 16 - mesh screen and not more than 6 per cent. shall pass a 200-mesh screen.

The sand shall be thoroughly mixed with the paving pitch either by hand stirring or by a mixture machine of approved construction. At the time of mixing, the sand shall be heated to a temperature of 400 degrees F., and the pitch to a temperature of 360 degrees F.

Alter mixing thoroughly the mastic filler shall be immediately flushed into the joints to the full depth thereof by means of approved squeegee or push brooms. The joints shall be filled flush with the surface of the pavement and shall be repoured where settlement occurs.

The pavement will then be given a top dressing of clean, coarse, sharp sand, spread uniformly to a depth of about one-eighth {1/8) inch over the entire surface.

Method of Testing. - All tests of materials required by the above specifications shall be carried out exactly in accordance with the methods adopted by the Society of Municipal Improvements at the 1916 meeting.

Payment. - The price bid per square yard will include furnishing and laying the mortar cushion, all wood block and all other materials and labor necessary to complete the pavement above the concrete foundation as specified. It will also include all work under "Grading," Item 1, where no bid is requested for the grading item