| Cts. per sq. ft. | |
| Cement, at $2 per bbl. | 3.6 |
| Sand and gravel | 1.5 |
| Labor, at $2.30 per day (average) | 2.2 |
| Incidentals, estimated | 0.7 |
| — | |
| Total per sq. ft | 8.0 |
This applies to a walk 4 ins. thick, and includes grading in some cases, while in other cases it does not. Mr. Bingham writes that in this respect the replies were unsatisfactory. He also says that the average wages paid were $2.30 per man per day. It will be noted that a barrel of cement makes 55½ sq. ft. of walk, or it takes 1.8 bbls. per 100 sq. ft. The average contract price for a 4-in. walk was 11½ cts. per sq. ft.
CONCRETE PAVEMENT.
Concrete pavement is constructed in all essential respects like cement sidewalk. The sub-soil is crowned and rolled hard, then drains are placed under the curbs; if necessary to secure good drainage a sub-base of gravel, cinders or broken stone 4 to 8 ins. thick is laid and compacted by rolling. The foundation being thus prepared a base of concrete 4 to 5 ins. thick is laid and on this a wearing surface 2 to 3 ins. thick. As showing specific practice we give the construction in two cities which have used concrete pavement extensively.
Windsor, Ontario.—The street is first excavated to the proper grade and crown and rolled with a 15-ton roller. Tile drains are then placed directly under the curb line and a 6×16-in. curb is constructed, vising 1-2-4 concrete faced with 1-2 mortar. Including the 3-in. tile drain this curb costs the city by contract 38 cts. per lin. ft. The pavement is then constructed between finished curbs, as shown by Fig. 119.
Fig. 119.—Concrete Pavement. Windsor, Canada.
The fine profile of the sub-grade is obtained by stretching strings from curb to curb, measuring down the required depth and trimming off the excess material. The concrete base is then laid 4 ins. thick. A 1-3-7 Portland cement concrete is used, the broken stone ranging from ¼ in. to 3 ins. in size, and it is well tamped. This concrete is mixed by hand and as each batch is placed the wearing surface is put on and finished. The two layers are placed within 10 minutes of each other, the purpose being to secure a monolithic or one-piece slab. The top layer consists of 2 ins. of 1-2-4 Portland cement and screened gravel, ¼ in. to 1 in., concrete. This layer is put on rather wet, floated with a wooden float and troweled with a steel trowel while still wet. Some 20,500 sq. yds. of this construction have been used and cost the city by contract:
| Per sq. yd. | |
| Bottom 4-in. layer 1-3-7 concrete | $0.57 |
| Top 2-in. layer 1-2-4 concrete | 0.32 |
| Excavation | 0.10 |
| —— | |
| Total | $0.99 |
This construction was varied on other streets for the purpose of experiment. In one case a 4-in. base of 1-3-7 stone concrete was covered with 2 ins. of 1-2-2 gravel concrete. In other cases the construction was: 4-in. base of 1-3-7 stone concrete; 1½-in. middle layer of 1-2-4 gravel concrete, and ½-in. top layer of 1-2 sand mortar. All these constructions have been satisfactory; the pavement is not slippery. The cost to the city by contract for the three-layer construction has in two cases been as follows: