Concrete Construction: Methods and Costs

by Halbert Powers Gillette; Charles Shattuck Hill

¼ barrel of cement at $2	$0.50
267 lbs. crushed stone	0.01
133 lbs. sand	0.01
1⅓ hours labor at 15 cts.	0.20
⅓ hour carpenter changing letters at 25 cts.	0.08
Coloring cement	0.02
	——
Total	$0.82

BONDING NEW CONCRETE TO OLD.—Concrete which has set hard has a surface skin or glaze to which fresh concrete will not adhere strongly unless special effort is made to perfect the bond. Various ways of doing this are practiced. The most common is to clean the hardened surface from all loose material and give it a thorough wash of cement grout against which the fresh concrete is deposited and rammed before the grout has had time to set. Washing the old surface with a hose or scrubbing it with a brush and water improves the bond, as does also the hard tamping of the concrete immediately over the joint. Mortar may be used in place of grout. The thorough cleansing of the surface is, however, quite as essential as the bonding coat, in fact in the opinion of the authors it is more essential. As a rule, a good enough joint for ordinary purposes can be got by tamping the fresh concrete directly against the old concrete, without grout or mortar coating, if the surface of the latter is thoroughly cleaned by scrubbing and flushing. The secret of securing a good bond between fresh concrete and concrete that has set lies largely in getting rid of the glaze skin and the slime and dust which forms on it. Washing will go far toward doing this. The glaze skin can be removed entirely by acid solutions, but the acid wash must be flushed free from the surface before placing the fresh concrete. Ransomite, made by the Ransome Concrete Machinery Co., Dunellen, N. J., is a prepared acid wash which to the authors' knowledge has given excellent success in a number of cases. The glaze coat can also be removed by picking the hardened surface, but the picking should be followed by washing to remove all loose chips and dust.

DIMENSIONS AND CAPACITIES OF MIXERS.—In planning plant lay-outs it is often desirable to know the sizes, capacities, etc., of various mixers in order to make preliminary estimates. Tables XXII to XXXIII give these data for a number of the more commonly employed machines. The Eureka, the Advanced and the Scheiffler mixers are continuous mixers and the others are batch mixers.

Table XXII—Sizes, Capacities and Weights of Advanced Mixers. Cement Machinery Co., Jackson, Mich.

Height ground to hopper top	3'6"
Width over all	3'6"
Length over all on trucks	10'6"
Capacity per hour, cu. yds.	25 to 75
Horsepower, engine	2
Weight:
On trucks, without power, lbs.	1,700
On trucks, steam engine	2,000
On trucks, gas engine	2,200
On trucks, steam engine and boiler	2,500

Table XXIII—Sizes, Capacities and Weights of Scheiffler Proportioning Mixers. The Hartwick Machinery Co., Jackson, Mich.

Mixer Number.	No. 2.	No. 2½.	No. 3.
Dimensions of hopper, ins.	55×33	53×33	60×40
Height, from ground to top of hopper, ins.	43	43	48
Width over all on trucks, ins.	46	46	46
Length over all on trucks, ins.	126	126	132
Hourly capacity in cubic yards	5-6	8	12-15
Horsepower required, gasoline engine	2	3	4
Horsepower required, steam engine.	3	4
Weights:
On trucks, without power, lbs.	2,400	2,900	3,300
On trucks, gasoline engine, lbs.	3,000	3,600	4,500
On trucks, steam engine, lbs.	2,800	3,330	4,000
On trucks, steam engine and boiler, lbs.	3,500	3,700	4,800

Table XXIV—Sizes, Capacities and Weights of Eureka Mixers. Eureka Machine Co., Lansing, Mich.

Mixer Number		No. 81	No. 82	No. 83	No. 84	No. 25	No. 23
Size hoppers, ins.	Sand	18"×25½"	...	...	18"×25½"	18"×25½"	18"×25½"
	Cement	17"×25½"	do	do	17"×25½"	17"×25½"	17"×25½"
	Stone	30"×25"	...	...	30"×25"	...	...
Height, ground to hopper top		49"	49"	49"	49"	49"	49"
Width over all on trucks		40"	40"	40"	40"	40"	40"
Length over all on trucks		12'-9"	10'-0"	10'-0"	10'-0"	8'-0"	8'-0"
Capacity per hour, cu. yds.		10 to 18	10 to 18	10 to 18	10 to 18	10 to 18	2 to 4
Engine horsepower		3 stm.	3 stm.	3½ gas	3 el. motr	Pulley.	Hand.
Boiler horsepower		4	...	...	1,980	1,400	1,400
Weight on trucks, no power		1,980	1,980	1,980	...	...	...
Weight trucks steam engine		2,800	...	...	...	...	...
Weight trucks gas engine		...	...	2,300	...	...	...
Weight trucks, eng. and boiler		3,000	...	...	...	...	...