Following are extracts from the 1908 specifications used in the Borough of Manhattan, City of New York: "The concrete foundation shall be 6 inches thick, including a mortar top surface of one-half inch in thick ness, the concrete proper being 5i inches thick, and shall withstand such tests as the engineer may deem necessary, and the contractor shall furnish such samples as may be required for the purpose.
"Upon the surface of the concrete foundation shall be spread a bed of cement mortar * inch in thickness. This mortar surface shall be composed of a slow setting Portland cement, and clean, sharp sand, free from pebbles, over one-quarter inch in diameter, and mixed in the proportion of one part cement to four parts of sand. This mortar top shall be thoroughly rammed into place with concrete rammers until all the uneven ness in the concrete shall be taken up, and shall then be • struck' to a true surface, parallel to the top of the finished pavement.
"On the surface of the concrete foundation before the mortar bed is laid shall be set strips of wood 4 inches wide by ' inch thick, or strips of steel 4 inches wide by not less than * inch thick, and of the greatest length convenient for handling. These strips shall be care fully set parallel and about 8 or Io feet apart, running from curb to curb, and be imbedded in mortar through out their length so that the top surface shall be 3* inches below and parallel to the grade of the finished pavement. The space between two strips having been
filled with mortar, a true and even top surface shall be struck by using an iron-shod straight edge on the strips as a guide, and as soon as the bed has been struck, the strip which would interfere with laying the block shall be removed and its place carefully filled with mortar with a trowel.
"If the width of the roadway be such that the laying of blocks on a complete section cannot be completed before the mortar takes its initial set, the strips may be placed parallel to the curb, and templates cut to the curve of the desired crown shall be used on these strips to strike the bed.
"On this mortar surface, spread and smoothed as above to the proper crown and grade, the blocks are to be laid with the grain vertical and at such an angle with the curb as the engineer may direct. They shall be laid in parallel courses with as tight joints as possible, each block being firmly bedded in the mortar bed so as to form a true and even surface. A inch paving expansion joint shall be used along each curb and across the street every no feet.
"The joints shall then be filled with cement grout composed of two parts clean sand and one part Port land cement, mixed to a perfectly liquid form, and the surface of the block shall be slushed with same and the joints swept until they are completely filled. The surface shall then be covered with inch of screened sand."