Concrete Construction Part 58

Figure 285 is a section of the concrete lining; the bottom layer for the floor was a 1-2-5 natural cement concrete, and for the sides a 1-2-6 Portland cement concrete; the top layer on both floor and sides was a 1-2-4 Portland cement concrete; 2-in. stone was the maximum size allowed in any concrete and 1-in. the maximum allowed in the top layer.

Smaller stone was used for special surface work, as noted further on.

The stone was cobbles turned up in the excavation work and had to be gathered from scattered piles and washed before crus.h.i.+ng. A 915 Farrel crusher, operated by a 12 HP. engine did the crus.h.i.+ng; it was rated at 125 tons a day, but averaged only about 40 tons. The fine dust was screened out and the remainder discharged into a 30-cu. yd., three-compartment bin, one compartment for stone less than 1 ins., another for 1 to 2-in. stone and a third for returns. The stone had 46 per cent. voids and weighed 95 lbs. per cu. ft. The sand was of excellent quality. Atlas and Beach's Portland and Hoffman natural cement were used.

All concrete was mixed and placed by hand, the concrete gang consisting generally of 1 sub-foreman, 2 men measuring materials, 2 men mixing mortar, 3 men turning concrete three times, 3 men wheeling concrete, 1 man placing concrete and 2 men ramming concrete. Two gangs were ordinarily employed, each mixing and placing about 20 cu. yds. per day, or 1.43 cu. yds. per man per day. The materials (sand and stone) were measured in bottomless boxes, the following sizes being used:

--Sand Box-- --Stone Box--

Prop. of Mix. Size. Vol. cu. ft. Size. Vol. cu. ft.

1-2-4[H] 2'9"2'1'8" 9.25 5'4'5" 14.8 1-3-6[H] 2'9"2'2' 11.1 5'6'8" 22.2 1-2-5 2'9"2'1'4" 7.4 5'6'6-5/8" 18.5 1-2-6 2'9"2'1'8" 9.25 5'7'2" 24.05

[Footnote H: These mixtures were used for gate house and standpipe foundation work.]

The bottom layer was placed in a continuous sheet; the top layer was laid in 10-ft. squares on the floor and in 810-ft. squares on the sides; these squares alternated in both directions, one-half being first laid and allowed to set. In laying the sides the surface was left 1 in.

low and then before the concrete had set was brought to plane by a 1-in.

layer of 1-2-4 mixture using stone and stone dust less than 3/8 in. The concrete for the floor was mixed rather wet and rammed until it quaked; on the sides a drier mixture was necessary to prevent flow. The cost of the lining concrete was as follows:

Bottom Layer on Floor: 1-2-5 Mixture: 1.25 bbls. natural cement at $1.08 $1.350 0.34 cu. yd. sand at $1.02 0.347 0.86 cu. yd. stone at $1.57 1.350 4 ft. B. M. lumber at $20 per M. 0.090 Labor, on forms 0.100 Labor mixing and placing 1.170 Labor general expenses 0.080 ------ Total $4.487

Bottom Layer on Sides: 1-2-6 Mixture: 1.08 bbl. Portland cement at $1.53 $1.652 0.37 cu. yd. sand at $1.02 0.377 0.96 cu. yd. stone at $1.57 1.507 Lumber for forms (about 1 ft. B. M.) at $20 0.016 Labor, on forms. 0.121 Labor, mixing and placing 1.213 Labor, general expenses 0.177 ------ Total $5.063

Top Layer on Floor and Sides: 1-2-4 Mixture: 1.37 bbls. Portland cement at $1.53 $2.09 0.47 cu. yd. sand at $1.02 0.48 0.75 cu. yd. stone at $1.57 1.17 12 ft. B. M. form lumber at $20 per M. 0.25 Labor, on forms 0.26 Labor, mixing and placing 1.530 Labor, general expenses 0.150 ------ Total $5.93

The side finish with 1-2-4 concrete of 3/8-in. stone cost $0.154 per sq. yd. 1 in. thick. This work was done by a gang of 3 plasterers and 3 helpers.

The layer of plaster between the concrete layers was put down on 4-ft.

strips and finished similarly to the surface of a granolithic walk. This layer consisted of 1-2 mortar finished with a 4-1 mortar. To keep the plaster from cracking it was covered with strips of coa.r.s.e burlap soaked in water; this precaution was not entirely successful, some cracks appeared and had to be grouted. Three gangs, each consisting of 1 plasterer and 1 helper, did the plastering, each gang laying about 700 sq. yds. per day. The cost of the plaster layer was as follows:

Item. Per 100 sq. ft. Per sq. yd. Per cu. yd.

Cement at $1.53 $1.15 $0.103 $7.42 Sand at $1.02 0.13 0.012 0.86 Burlap 0.02 0.002 0.14 Labor 0.92 0.083 6.00 ----- ------ ------ Totals $2.22 $0.200 $14.42

It will be noted that it took over 5 bbls. of cement per cubic yard, and that the labor cost was $6 per cubic yard.

~RELINING A RESERVOIR, CHELSEA, Ma.s.s.~--The following account of relining the Powder Horn Hill Reservoir at Chelsea, Ma.s.s., is taken from a paper by Mr. C. M. Saville. This reservoir which holds about 1,000,000 gallons is oval in shape, 98175 ft. at the top, 68148 ft. at the bottom and 15 ft. deep, with side slopes about 1 on 1. The work was done by day labor.

For sake of completeness the costs of excavation and back-filling are given here as well as the concrete costs.

The top of the bank was too narrow to allow the use of carts and an 18-in. gage railroad was decided upon as most convenient for handling materials. A 65-ft. boom derrick with a 70-ft. mast was used for removing the excavated material and for depositing concrete. The derrick was operated by a 15-h.p. double drum hoisting engine, was held in place by six wire guy ropes, and had a reach such that only one moving was necessary after it was placed. The engine and derrick were set up on the floor of the reservoir, and the work of excavation was begun at about the middle of the south side. In order to facilitate the work, a platform supported on A frames was set up. These frames were s.p.a.ced about 15 ft. apart and rested on the bottom and slope of the reservoir, being held in place by bolts driven into the floor.

The paving blocks on the top of the slope were removed and piled up to be taken away. The old lining and the material excavated from the bank were shoveled into the scale pan of the derrick, hoisted to the cars on the top of the bank, and then run by gravity to a dump a short distance down the hillside. Here the cars were run out on a rough trestle, the load dumped, and the empties hauled back to the work by a rope carried through pulleys to the winch head on the hoisting drum of the engine.

For the storage of some of the materials, two small portable storehouses were set up--one 8107 ft., the other 1116 x 7 ft. The bulky portions, such as cement, sand, and stone, were delivered as necessary, a few days' supply only being kept on hand. A branch from the railroad was so arranged that it pa.s.sed the storehouses and stone piles, while the sand was piled close to the concrete mixing board. The intention on the work was to do nothing by hand that could possibly be done by steam, except that all of the concrete was mixed by hand. As great a proportion of water was used as could be done without causing the material to slide when rammed in place.

The lower layer of concrete was of the proportion by volume of 1 cement, 2 sand, and 6 crushed stone (sizes from to 1 ins.). This was rather a lean mixture, and as it could not be rammed enough to flush all over, the surface was finished where necessary by a thick mortar made in the proportion of 1 cement to 6 sand, and applied with heavy brushes. Before placing any of the concrete, the bank back of the old concrete left in place was thoroughly rammed with iron railroad tampers, and the edge of the old concrete was scrubbed with water and a stiff brush and then coated with 1 to 4 grout, which was allowed to fill in the angle between the concrete and the slope. Just before placing the concrete the earth bank was well wet in order that moisture might not be drawn from the concrete while it was soft.

In order to make the new lining as waterproof as possible, a layer of asphalt was placed on top of the lower layer of concrete and brought up on the exposed edge of the old layer at the bottom of the new work.

This, it was expected would make an elastic and watertight joint between the new and the old work.

Venezuela asphalt, "Crystal Brand," was used, being poured upon the top of the concrete layer and allowed to run down the slope, care being taken that the concrete was entirely and perfectly covered. After the first layer of asphalt was cool, a second layer was similarly applied, and the resulting sheet was about in. thick. Any inclination to crawl down the slope when exposed to the sun was readily stopped by throwing on a pailful of cold water. A most particular part of this work was to get the asphalt as hot and liquid as possible and yet not burn it. All of the concrete was protected from the sun and kept damp by being covered with strips of burlap, which were moistened by sprinkling.

The upper layer of concrete was composed of a much richer mixture of concrete than that used in the bottom layer, the proportions by volume being 1 cement, 1 sand, 1 stone dust, and 4 broken stone of the sizes mentioned above. On account of the steep slope it was possible to do only a little ramming, and the material was laid as wet as possible. To make this layer more impervious and also to obtain a smooth surface, the concrete was left about an inch below and a finish coat applied by expert granolithic finishers. This coating was applied as soon as it was possible to do so after the main layer was in place, but on account of the steepness and the liability of the wet concrete to flow, care had to be taken not to begin work too soon.

The top finis.h.i.+ng coat was made in the proportion of 1 part cement, 1-2/3 part sand, and 3-1/3 parts stone dust. In order to help in bonding, the last ramming on the concrete was done with rammers studded with pieces of iron about 1 in. long and in. deep.

The finis.h.i.+ng was done in three operations: The material was spread on the concrete and thoroughly worked into it by the finishers, using rough wooden floats; after this it was gone over and partially smoothed down with a thin steel float; and finally it was worked to give the finished appearance and an impervious surface.

The under layer of concrete was placed in a continuous sheet. The upper layer was put down in alternate strips, 10 ft, long (the whole length of the layer) and 5 ft. wide. These blocks were built up in forms, which were not removed until the concrete had set. Finally, the back or edge of the block toward the bank was well wet and thoroughly plastered, to prevent, as far as possible, the infiltration of any water. The plaster was mixed in the proportion of 1 part cement to 4 parts sand. When the forms were wholly removed, the s.p.a.ce between the concrete and the bank was refilled, to within about 6 ins. of the top, with a clayey material previously excavated, and the s.p.a.ce was filled and graded to the top of the bank with loam. During the work two holidays intervened; the men were also transported to and from the work. Charges were made for these items, amounting to $209.77, and this sum, together with the cost of installing the plant ($716.03) are proportionally charged against the work as follows:

Per cent. Total. Per cu. yd.

Excavation 70.3 $651 $2.17 Lower concrete 12 111 1.16 Upper concrete 15.4 143 1.11 Back fill 2.3 21 .28

The detailed cost of repairing the reservoir lining is given in the following tabulations:

Excavation.

Rate. Per cu. yd.

Foreman 9 5/9 days $4.00 $0.13 Engineman 12 3/9 days 3.00 .12 Carpenter 2 days 2.67 .02 Laborers 9 6/9 days 2.25 .07 Laborers 110 2/9 days 2.00 .73 Laborers 46 5/9 days 1.75 .27 Derrick 12 3/9 days 3.75 .15 Rails and cars 11 2/9 days 0.40 .02 Stove coal 3.05 tons 6.50 .07 Egg coal .95 tons 6.25 .02 ---- Total, 300 cu. yds. 1.60

Estimated proportionate charge for plant installation and holidays 2.17 ---- Grand total 3.77

Lower Layer Concrete.

Rate. Per cu. yd.

Foreman 3-7/9 days $4.00 $0.16 Engineer 2-3/9 days 3.00 0.07 Carpenters 7 days 2.67 0.20 Laborers 1-7/9 days 2.25 0.06 Laborers 89 days 2.00 1.87 Laborers 4 days 1.75 0.07 Derrick and engine 2-3/9 days 3.75 0.08 Rails and cars 2-2/9 days 0.40 0.01 Cement 106-3/8 bbls. 1.35 1.50 Sand 37.4 cu. yds. 1.10 0.43 Broken stone 117.9 tons 1.35 1.67 Egg coal .41 tons 6.25 0.03 Lumber 1.3 M. ft. 21.00 0.28 ---- Total, 95.5 cu. yds. $6.43

Estimated proportionate charge for plant installation and holidays 1.16 ---- Grand total $7.59

Upper Layer Concrete.

Rate. Per cu. yd.

Foreman 6-7/9 days $4.00 $0.21 Engineer 1-8/9 days 3.00 0.04 Carpenter 18-5/9 days 2.67 0.38 Laborers 1-7/9 days 2.25 0.03 Laborers 119-5/9 days 2.00 1.85 Derrick and engine 1-8/9 days 3.75 0.05 Rails and cars 8-3/9 days 0.40 0.03 Cement 176 bbls. 1.35 1.86 Sand 30.2 cu. yds. 1.10 0.26 Stone dust 41.6 tons 1.50 0.48 Broken stone 122.8 tons 1.35 1.28 Egg coal .2 tons 6.25 0.00 Lumber 4 M. ft. 21.00 0.65 Burlap 300 yds. 0.04 0.10 Nails 170 lbs. 0.05 0.03 ----

Total, 129.2 cu. yds. $7.25 Estimated proportionate charge for plant installation and holidays 1.11 ---- Grand total $8.36

Back Plaster.

Rate. Per cu. yd.

Plasterer 3-8/9 days $5.40 $0.08 Plasterer 8/9 days 6.00 0.02 Plasterer 5-5/9 days 4.50 0.09 Laborers 9-3/9 days 2.25 0.08 Laborers 3/9 days 2.00 0.00 Cement 6 bbls. 1.35 0.03 Sand 3.3 cu. yds. 1.10 0.01 ---- Total, 262 sq. yds. 0.32

Surfacing.

Rate. Per cu. yd.

Plasterer 7-6/9 days $5.40 $0.09 Plasterer 2-1/9 days 6.00 0.03 Plasterer 9-4/9 days 4.50 0.09 Laborers 12-8/9 days 2.25 0.06 Laborers 2-4/9 days 2.00 0.01 Cement 22 bbls. 1.35 0.06 Sand 5.07 cu. yds. 1.10 0.02 Stone dust 14 tons 1.50 0.04 ---- Total, 460 sq. yds. $0.40

Asphalt.

Rate. Per cu. yd.

Foreman 1/9 day $4.00 $0.00 Asphalt man 11 days 2.00 0.05 Laborers 6 days 2.00 0.02 Asphalt kettle 11 days 1.50 0.03 Asphalt 3.9 tons 30.00 0.25 Asphalt mops 3.00 0.01 ---- Total, 464 sq. yds. $0.37

Back Filling.

Rate. Per cu. yd.

Foreman 1-3/9 days $4.00 $0.07 Laborers 23-3/9 days 2.00 0.62 Laborers 9 days 1.75 0.21 Rails and cars. 2-2/9 days 0.40 0.02 Loam 27-5/9 cu. yds. 1.25 0.46 ----- Total, 75 cu. yds. $1.38