Concrete Construction Part 48

Several combinations of arrangements were used for molding the columns and girders. For wall columns having one bracket the arrangement shown by Fig. 240 was adopted. The concrete slab molding platform was covered with paper, and on this the two outside and the middle columns were cast in forms. When those columns had set the forms were removed, the intervening s.p.a.ces were papered and the two remaining columns were cast.

Ten columns, five sets of two columns in line, were cast on each base.

The remaining columns were cast in combination with girders as shown by Fig. 241. The two outside lines of columns (1) were molded in forms, allowed to stand until set and then stripped. Using a column surmounted by a shallow side form for one side and a full depth side form for the other side molds were fashioned for the two outside girders, Nos. 2 and 3. One full depth side form and the side of girder No. 2 formed the mold for girder No. 4. Girder No. 5 was then molded between girders No. 3 and No. 4.

[Ill.u.s.tration: Fig. 241.--Arrangement for Molding Four Four-Bracket Columns and Four Roof Girders]

[Ill.u.s.tration: Fig. 242.--Forms for 50-ft. Roof Girders.]

The construction of the girder forms is shown by Fig. 242. This drawing shows one of the four main sections making up a complete form. A full size form of this construction contained about 1,100 ft. B. M. of lumber, and three were built, so that 3,300 ft. B. M. of form lumber were used for molding 20 girders, or 33 ft. B. M. per cubic yard of concrete. A full size column form contained about 225 ft. B. M. of lumber, and eight were constructed, so that 1,800 ft. B. M. of form lumber were used for molding 56 columns, or about 16 ft. B. M. per cubic yard of concrete.

The following was the cost of erecting a full column form including lining, plumbing, bracing and yoking, but excluding lumber and original construction:

1 carpenter, 3 hrs., at $0.25 $0.750 1 helper, 3 hrs., at $0.175 0.525 1 helper, 1 hr., at $0.175 0.175 1-5 boss carpenter, 3 hrs., at $0.30 0.180 ------ Total $1.630

This gives a cost of $7.25 per M. ft. B. M. for erecting column forms.

The cost of erecting a full size girder form including lining, plumbing, bracing and setting six bolts was as follows:

2 carpenters, 5 hrs., at $0.25 $2.50 2 helpers, 5 hrs., at $0.175 1.75 2 laborers, hr., at $0.15 0.15 boss carpenter, at $0.30 0.375 ------ Total $4.775

This gives a cost of $4.35 per M. ft. B. M. for erecting girder forms.

The reinforcement was erected inside the forms for both columns and girders. The cost of erection for one column was:

2 laborers, 4 hrs., at $0.15 $1.20 1/3 foreman, 4 hrs., at $0.225 0.30 ----- Total $1.50

This gives a cost of about 0.22 cts. per pound for erecting column reinforcement, including the bending of the horizontal ties or hoops.

The girder reinforcement was erected by piece work at a cost of $1.80 per girder--or about 0.08 ct. per pound.

The concrete used was a 1-6 mixture of Portland cement and crusher run stone all pa.s.sing a -in. sieve and 10 per cent. pa.s.sing a 200 mesh sieve. No trouble was had in handling this fine aggregate. It was mixed in a Ransome mixer, elevated so as to deliver the batches into cars on a standard gage track. This track ran between the base slabs on which the molding was done. Each car held about 3 cu. yds. and discharged through a side gate and spout directly into the forms, the mixture being made so wet that it would flow readily. The company used its own cement and stone for concrete and charged up the cement at $1 per barrel and the stone at 60 cts. per cubic yard. At these prices, and a.s.suming that a cubic yard of concrete of the mixture above described would contain about 1.25 bbl. of cement and 1.5 cu. yd. of stone, we have the following cost of materials per cubic yard of concrete:

1.25 bbls. of cement, at $1 $1.25 1.5 cu. yds. stone, at $0.60 0.90 ----- Total $2.15

The actual cost of mixing the concrete and delivering it to the cars was as follows:

Item. Per cu. yd.

1 foreman, at 20 cts per hour $0.0300 3 men shoveling stone, at 15 cts. per hour 0.0675 3 men filling hopper, at 15 cts. per hour 0.0675 1 man bringing cement, at 18 cts. per hour 0.0225 1 man dumping cement, at 15 cts. per hour 0.0225 9 h.p., at ct. per h.p. hour 0.0450 Superintendence, repairs, etc. 0.0270 ------- Total $0.2820

The cost of hauling the concrete from mixer to forms ran about 2.7 cts.

per cubic yard, so that we have a cost for concrete in place of:

Concrete materials, per cu. yd. $2.150 Mixing concrete, per cu. yd. 0.281 Hauling concrete, per cu. yd. 0.027 ------ Total cost, per cu. yd. $2.458

The cost, then, per column or girder molded, a.s.suming that it was necessary to erect a full form, was about as follows:

Columns: 2 cu. yds. concrete, at $2.46 $ 4.92 675 lbs. steel, at 2 cts. 16.77 Erecting steel, at 0.22 ct. per lb. 1.50 Erecting forms 1.63 ------ Total $24.82

Girders: 5 cu. yds. concrete, at $2.46 $12.30 2,260 lbs. steel, at 2 cts. 56.50 Erecting steel, at 0.08 ct. per lb. 1.80 Erecting forms 4.77 ----- Total $75.37

[Ill.u.s.tration: Fig. 243.--View Showing Method of Hoisting Molded Columns.]

These figures give a unit cost of $12.41 per cu. yd. for molded columns, and of $15.07 per cu. yd. for molded girders, The columns were erected by a Browning locomotive crane, which lifted and carried them to the work and up-ended them into place. To facilitate lifting the columns from the molding bed a 1-in. pipe 8 ins. long was cast into both ends; pins inserted into these sockets provided hitches for the tackle. The column was lifted off the molding bed and blocked up, then iron clamps were attached, one at each end, as shown by Fig. 243. A gang of 1 foreman and 14 men erected from 5 to 7, or an average of 6 columns per 10-hour day. The average wages of the erecting gang were 21 cts. per hour. The cost then of column erection was (14 $2.10) 6 = $5.25 per column, or $2.63 per cu. yd. of concrete.

[Ill.u.s.tration: Fig. 244.--Sketch Showing Sling for Erecting 50-ft. Roof Girders.]

The roof girders had 1-in. eye-bolts 24 ins. long cast into them vertically about 4 ft. from the ends. They were lifted off the molding bed by tackle by the locomotive crane to these eye-bolts and blocked up to permit the adjustment of the sling. This sling is shown by the sketch, Fig. 244, and as will be observed acts as a truss. At first it was used without the vertical, but the cantilever action of the unsupported ends caused cracks. The girders were loaded onto cars by the locomotive crane and taken to the work, where they were hoisted and placed by a gin pole. The girder erecting gang consisted of 1 foreman and 14 men, working a 10-hour day at 21 cts. per hour. This gang erected four girders per day, at a cost of (15 $2.10) 4 = $7.87 per girder, or $1.57 per cu. yd. of concrete.

The cost of girders and columns in place was thus about as follows:

Columns: Per unit. Per cu. yd.

Molding $25.00 $12.50 Erecting 5.25 2.63 ------ ------ Totals $30.25 $15.13

Girders:

Molding $75.00 $15.00 Erecting 7.87 1.57 ------ ------ Totals $82.87 $16.57

[Ill.u.s.tration: Fig. 245.--View Showing Method of Handling Roof Slabs.]

In this same building the roof was composed of 126 ft.4-in. slabs molded in tiers; a slab was molded and when hard was carpeted with paper and the form moved up and a second slab molded on top of the first. This operation was repeated until a tier of slabs had been molded. By molding each slab with a 3-in. overlap, as shown by Fig. 245, they could be easily separated by lifting on hooks inserted under the overhanging ends. Each slab contained 0.925 cu. yd. of concrete and about 116 lbs.

of reinforcement. The cost of molding one roof slab, including materials, forms and labor, was as follows:

Materials: Per slab. Per cu. yd.

1 bbl. cement, at $1 $1.000 $1.081 1.06 tons stone, at $0.60 0.636 0.687 116 lbs. steel, at 2 cts. 2.647 2.862 ------ ------ Total $4.283 $4.630

Forms: Lumber and making $0.104 $0.112 92 sq. ft. paper, at 33-1/3 cts. per 500 sq. ft. 0.055 0.059 Labor erecting and removing 0.5625 0.608 ------- ------ Total $0.7215 $0.779

Mixing, Hauling and Placing: Mixing $0.222 $0.240 Hauling 0.025 0.027 Placing concrete and steel 0.170 0.183 ------ ------ Total $0.417 $0.450

General Expenses: Housing and heating $0.700 $0.757 Superintendence, power, etc. (10%) 0.612 0.661 ------ ------ Total $1.312 $1.418 Grand totals $6.7335 $7.277

The roof slabs were raised from the casting beds by means of the locomotive crane and hooks, as shown by Fig. 245, and loaded onto cars; eight slabs made a carload. The cars were run to the work, where the gin poles hoisted the slabs one at a time to cars running on a track built on timbers laid on top of the roof girders. A small derrick on rafters picked the slabs from the hand car and set them in place. A gang of 15 men erected from 18 to 20 slabs per 10-hour day. With average wages at 21 cts. per hour the cost of erection was (15 $2.10) 19 = $1.66 per slab, or $1.79 per cu. yd. The total cost of slabs in place was thus:

Item. Per slab. Per cu. yd.

Molding $6.73 $7.27 Erecting 1.66 1.79 ----- ----- Total $8.39 $9.06

In studying these cost figures their limitations must be kept in mind.

Because of the character of the available data quant.i.ties had in several cases to be estimated from the working drawings. The cost of lumber for and of framing column and girder forms is not included, but this is partly balanced at least by the a.s.sumption that each form was erected complete for each column and girder, which was not the case, as has been stated. Cost of plant is not included nor is cost of shoring the columns until girders and struts were placed, nor are several minor miscellaneous items.

~HOLLOW BLOCK WALL CONSTRUCTION.~--Three general processes of molding hollow wall blocks of concrete are employed: (1) A dry mixture is heavily tamped into a mold and the block is immediately released and set aside for curing; (2) a liquid is poured into molds, where the block remains until hard: (3) a medium wet mixture is compressed into a mold by hydraulic presses or other means of securing great pressure. The molds used may be simple wooden boxes with removable sides or mechanical molds of comparative complexity. Generally mechanical molds, or concrete block machines as they are commonly called, will be used. There are a score or more kinds of block machines all differing in construction and mode of operation. None of them will be described here, but those interested may consult "Concrete Block Manufacture" by H. H. Rice or "Manufacture of Concrete Blocks and Their Use in Building Construction"

by H. H. Rice, Wm. M. Torrance and others.

~Factory Buildings, Grand Rapids, Mich.~--The buildings ranged from one to four stories high and altogether occupied some 74,000 sq. ft. of ground.

The owners installed a block making plant fully equipped with curing racks, two Ideal machines, two National concrete mixers, 5 h.p. gasoline engine, platens, tools and a Chase industrial railway.

The walls were constructed of 24-in. square pilasters of blocks arranged as shown by Fig. 246, connected by curtain wall belt courses of single blocks. The blocks were 8816 ins., and after molding the faces were bush hammered and the edges tooled. The pilasters, consisting of four blocks laid around an 88-in. hollow s.p.a.ce, were solidified by pouring the 88-in. s.p.a.ce and all but the three outside block cavities with wet concrete. The interior of the building was of regulation mill construction, and as the pilasters reached the heights for beam supports cast iron plates with downward f.l.a.n.g.es were set in the concrete. These plates had a cast pin projecting upward to fasten the beam end.

[Ill.u.s.tration: Fig. 246.--Concrete Block Pilaster for a Factory Building.]

The materials used for the block were Sandusky Portland cement and -in.

bank gravel well balanced from fine to coa.r.s.e. The blocks were molded with 1-3 mortar faces, the mortar being waterproofed by a mixture of Medusa waterproofing compound. All concrete was machine mixed. The men operating the block machines were paid 1 ct. for each block molded, so that their pay depended upon the energy with which they worked. The men handling materials and engaged in handling and curing the blocks were paid $1.75 per day. The gravel was shoveled from the railway cars onto the screens and from the screen piles to the mixers. The gang was organized as follows: