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UNITED STATES DEPARTMENT OF LABOR
L. B. Schwellenbach, Secretary
BUREAU OF LABOR STATISTICS
Ewan Clague, Commissioner
Labor Requirements for Construction
Materials
P A R T I.—PORTLAND CEMENT
Bulletin 7S[o. 888-1
UNITED STATES
GOVERNMENT PRINTING OFFICE
WASHINGTON : 1947
For sale by the Superintendent o f Documents, U . S. Governm ent Printing Office
Washington 25, D . C« ~ Price 15 cents
Letter o f Transmittal
U n it e d S t a t e s D e p a r t m e n t o f L a b o r ,
B u r e a u of L abor St a t is t ic s ,
Washington, D. C., November 5, 1946.
T h e S ecretary of L a b o r :
I have the honor to transmit herewith a report on the labor requirements in
cement production, a summary of which was published in the Monthly Labor Re
view for September 1946.
This is the first o f a series of reports covering those industries which supply
essential building materials. This study was made in order to measure the
amount of “ behind-the-line” employment which would result in the cement in
dustry from any given level of construction activity.
This study, under the direction of Brunswick A. Bagdon, is based upon plant
data collected by the field personnel assigned to the Labor Requirements Survey
in the Regional Offices; the report was written by Alfred W. Collier and Clyde
Stone in the Bureau’s Division o f Construction and Public Employment.
E w a n C l a g u e , Commissioner.
Hon. L. B. SCH W ELUENBACH,
Secretary of Labor.
hi
Preface
This study, the first o f a series covering those industries which sup
ply essential building materials, has been made in order to measure
the amount o f “ behind-the-line” employment which would result in
the cement industry from any given level of construction activity.
Previous studies o f man-hour requirements made by the Bureau in
1933, as a part of the program of the Federal Emergency Administra
tion o f Public Works, included steel, cement, lumber, and plumbing
and heating supplies. For these products, information was collected
from the primary sources for raw materials, transportation, manu
facturing, and delivery to the construction site.
From 1935 to 1939 comparable studies were also made covering the
following industries: Clay products, the transportation o f construc
tion materials, and the manufacturing and distribution of electrical
goods. Today these studies, while of historical significance, have
several serious limitations; namely, (a) new products have been de
veloped which were not included in the previous report, (&) manufac
turing methods have, in several instances, changed considerably, and
(o) variations in volume o f output as between the period o f the thirties
and the current time would result in marked variations in man-hour
requirements.
Building construction was greatly hindered during the period fol
lowing VJ-day, and by the middle of 1946 building activity still had
not shown marked headway. However, the forecasts, both public and
private, indicate peak activity in the months ahead. Housing pro
grams are under way. Federal subsidies are being appropriated to
speed up and increase the volume o f the production o f essential build
ing materials. Construction workers are being demobilized from the
armed services. Thus, everything points to a high level of activity in
the building construction industry for some time to come.
This series o f reports will provide accurate data on the man-hours .
required per unit o f output and per unit o f dollar value, for each of
50 important construction and building materials—both traditional
materials such as dimension lumber, cement, and reenforcing steel,
and newer materials such as plywood (included only incidentally in
the previous reports), insulating material, and the commoner fabri
cated steel products for residential buildings. For each o f the prod
ucts included, comprehensive field data will be collected on the direct
and overhead man-hours in production during a recent period, the
output during this period, the quantities or value o f materials, sup
plies and fuel consumed, in-bound and out-bound freight expenses,
and, wherever possible, sales both directly to contractors and through
distributors and dealers. From these data, total man-hour require
ments, from extraction o f raw materials to delivery o f completed
materials at the construction site, will be obtained for an extensive
series o f materials representative of the requirements for most types
o f construction; in addition, the data will permit reasonable estimates
o f man-hour requirements for a large number o f other materials
generally similar to those studied, but not sufficiently important for
individual study (primarily highly specialized materials, and customorder variants o f common materials).
v
B ulletin 7v[o. 888— 1 o f the
U nited States Bureau o f Labor Statistics
{Reprinted from the M onthly L abor R eview , September 1946, with additional material]
C ontents
Page
Introduction___________________________________________________________
Characteristics and background of the industry_____________________
Manufacturing processes_________________________________ - ________
Industry coverage and methods of data collection___________________
Man-hour requirements in manufacturing and milloperations.
______
Quarrying operations______________________________
Processing department_____________________________________________
Shipping department____ __________________________________________
Maintenance and overhead_________________________________________
Administrative department________________________________________
Variations in labor requirements:
By rate of operation and plant capacity____________________________
By geographic areas______
_ . ______________________________ Total man-hour requirements for production and transportation.
Production of raw materials______________________
Gypsum_______________________________________________
Coal_____________________________________________________
Power_____________________________________________________
Transportation of raw materials________________________________
Coal_______________________________________________________
Gypsum____________________
Transportation of finished cement___
Plant to railhead______
Railhead to construction site.
Trend of productivity, 1930 to 1945-------------------------------------------------------
VII
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BY C O URTESY O F M A R Q U E TTE C E M E N T
M A N U F A C T U R IN G
CO-
Fig. 1.— Inspector checking “ crusher-run” cement making materials being delivered into
a crane-way storage.
Labor Requirements for Construction
Materials
P art I.— P ortland Cement
Introduction
One o f the basic materials used in any construction program is portland cement. Because of this and because the industry was in a most
favorable position to resume peacetime operations, the Bureau o f
Labor Statistics has selected the cement industry for its first in a series
of studies of labor requirements for construction materials.
The first study o f labor requirements in cement production made by
the Bureau of Labor Statistics covered the man-hours required to
manufacture 100 barrels o f portland cement in 1934.1 The current
study revises these data for the year 1945 and the first quarter of 1946.
This study derives special significance from the fact that there is an
anticipated large volume o f construction of all types in 1946. Con
struction needs for 1946 are estimated to be approximately 131 million
barrels o f cement. The annual capacity o f the cement industry is esti
mated at 220 million barrels, which could be increased to 280 million
barrels by increasing the number of work shifts.2 It is noteworthy
that no apprehension regarding availability of cement as needed has
been expressed in public or private analyses of the building material
shortages.
CHARACTERISTICS AND BACKGROUND OF THE INDUSTRY
Portland cement is the product obtained by mixing proper propor
tions o f finely ground materials containing calcium, silica, and alu
mina, burning the mixture until it approaches the melting point, then
grinding the resulting material into a fine powder. Before or during
the grinding process about 4 percent of gypsum or calcium sulphate
is added for the purpose of regulating the hardening period o f the
cement when it is mixed with water.
The calcium-bearing materials may consist of limestone, cement
rock, marl, oyster shell, chalk, or caustic soda waste; the silica-bearing
materials may consist of clay, shale, blast-furnace slag, slate, or cement
rock.
1 See M onthly Labor Review, M arch 1936 (pp. 56 4-57 7) : Labor Requirements in Ce
ment P roduction, by Bernard H. Topkis (reprinted as a separate, Serial No. R. 358).
2 U. S. Departm ent o f Commerce, Construction and Construction M aterials, May 1946
(p. 3 7 ). Estimates are based on maximum attainable production with allowances for
maintenance, repairs, and unavoidable shut-downs.
722455°— 47------ 2
1
2
LABOR REQUIREMENTS FOR CONSTRUCTION MATERIALS
Portland cement is one of a family o f hydraulic cements which
produces an artificial stone when hardened by combining with water.
Since more than 98 percent o f the cement produced in the United States
is portland cement, this report will deal with that product only. More
over, it was not found practicable to obtain separate data for the dif
ferent types o f portland cement, such as the general use, moderate
heat, high early strength, low heat, sulphate resisting, oil well, white
cement, portland-puzzolan, etc. All of these types with the exception
o f the general use and moderate heat cements are known as specialpurpose cements, embodying certain special characteristics, and require
special treatment in manufacture. The special purpose cements ac
count for less than 10 percent of the total production of portland
cement, and their effect upon man-hour requirements are relatively
minor.
Among new trends in the cement industry is the growing interest in
air-entrained cement. A ir entrainment may be obtained by the use of
regular or general use cement with an interground air-entraining agent
or by means of an air-entraining agent added to the concrete at the
mixer. A feature of air-entrained concrete is its greater resistance to
disintegration and scaling, caused by freezing and thawing and salt
applications, as compared with normal portland cement concrete. Its
disadvantages lie in its somewhat lower flexural and compressive
strength. In tests of concrete pavement the loss in strength was not
great enough to cause failure while considerable durability was added
by use o f air-entraining agents.3 New trends during the war years
were directed toward uses of cement products as a substitute for scarce
materials, for example, concrete beams, tanks, and joists to replace
steel.4
Portland cement derives its name from its resemblance, when set,
to a famous English building stone quarried in the Isle of Portland.5
The name was first suggested by Joseph Aspdin, an English bricklayer,
who is credited with discovering the principle of artificially mixing
limestone and clay to form a product similar to portland stone. He
was granted a patent for its manufacture by George IY in 1824.6
For nearly 43 years after the patent was granted to Joseph Aspdin,
portland cement was manufactured only in England and on the Con
tinent, and its entire production was consumed there. The first drib
ble of portland cement was imported from Europe to the United
States in 1868. The imports increased rapidly and amounted to 92,000
barrels in 1878. By 1885 the imports reached 554,000 barrels.7
The first manufacturer o f portland cement in the United States was
David O. Saylor of Allentown, Pa., who was granted the first United
States patent in 1871. The cement was so successful that by 1878 the
United States Government specified Saylor’s cement for the Eads
Jetties at the mouth o f the Mississippi River, the first important public
works where domestic portland cement was used. Within 20 years
after Mr. Saylor’s original venture (by 1891), 16 portland cement mills
3 Barbee, J. T., in Rock Products, Vol. 49, No. 3, pp. 69, 70.
4 U. S. Bureau o f Mines, Minerals Yearbook, 1944 (Cem ent).
5 Hadley, Earl J . : The M agic Powder. New York, G. P. Putnam 's Sons, 1945, p. 4.
6 Idem, p. 13.
7 Idem, p. 4.
PORTLAND C EM E N T
3
were in operation in different parts of the country, especially in Penn
sylvania, New York, Indiana, Texas, Oregon, and Michigan.8
In the two decades, 1900 to 1920, the complete mechanization o f the
industry was achieved. The introduction of the rotary kiln was
perhaps the largest single factor. The dome kiln, into which a charge
of raw materials was placed for burning and then withdrawn before the
introduction o f a succeeding charge, required excessive amounts o f
labor and delivered a product of varying quality. The shaft kiln
provided continuity o f operation but did not improve the quality
of the product. The rotary kiln enabled continuous operation with
a higher rate o f production, eliminating shut-down periods for re
charging, made possible an improved product of uniform quality as
a result o f better temperature control, and reduced labor and fuel
requirements in the burning process. It also acted as an impetus
to mechanization in other operations of the cement plant.
By 1920 the establishment of all basic techniques had been com
pleted, and during the following 20 years efforts were directed toward
improving these techniques for the purpose of reducing costs and
producing cement of higher strengths and more uniform quality.
The refinements in technique have been of little importance individu
ally, but collectively have made possible substantial reductions in
labor and fuel costs, and increased the efficiency of existing plants.9
MANUFACTURING PROCESSES
About 80 operations are necessary for the production of portland
cement which meets modern specifications,1 and throughout all opera
0
tions careful checks are made to insure the uniformity and quality
o f the product. The initial step is the quarrying o f the raw materials.
The crushing o f the quarried minerals, which initially may be of tre
mendous size, is done by self-contained units which reduce the minerals
to about 3 to 4 inches in diameter.
After the crushing, the material is taken to the raw mill for raw
grinding. This step is really a continuation of the crushing process,
but because of the smaller size of the material, the machines are of
a different type and may operate on a different principle from that
used in the initial crushing. In raw grinding the material is reduced
to such a degree of fineness that 95 percent of it will pass through
a 200-mesh screen (40,000 openings per square inch). It is then con
veyed to storage bins or silos where it is kept until ready for burning.
Rotary kilns are the most widely used in this country for the manu
facture o f cement. The kilns operate at a speed range o f 1 to 3 minutes
for each revolution. The slope o f the kiln is pretty well fixed at onehalf inch per foot. The raw material is fed into the upper end,1 and
1
the kiln is fired from the lower end.
■ Hadley, E arl J . : The M agic Powder, New York, G. P. Putnam ’s Sons, 1945, p. 23.
*
9 M echanization in the Cement Industry, Report No. M -3, W ork P rojects Administration,
1939, p. 33.
1 M onthly Business Review, Federal Reserve D istrict No. 4 (C leveland), Vol. 28, No. 5
0
p. 2.
11 Pit and Quarry Handbook, 37th ed., 1944, p. 351.
4
LABOR REQUIREMENTS FOR CONSTRUCTION MATERIALS
Kilns range in size from 6 feet in diameter and 60 feet in length to
12 feet in diameter and 475 feet .in length. The raw material, either
in the form of a dry powder or a slurry containing from 30 to 50 per
cent o f water, is fea into the upper end of the kiln, where intense heat
(about 2,750° F.) produced either by powdered coal, gas, or fuel oil
calcines the materials to unite them in a new chemical product, portland cement in clinker form.
As the clinker leaves the kiln it is sometimes air cooled or “ quenched”
by being passed over grates through which air is forced under pressure.
This air “ quenching” enables the clinker to be ground soon after leaving
the kiln and assures a more uniform and better finished product. The
cooler also serves to preheat the combustion air, resulting in a substan
tial fuel saving in firing the kiln.
The next step, sometimes referred to as finish grinding, reduces the
clinker to extreme fineness. The grinding is done by ball, pebble, or
tube mills. The ball mill is a cylindrical, horizontal, slow-speed rotat
ing drum containing a mass o f metal balls as grinding media. The
pebble mill uses flint or other ceramic pebbles as the grinding media.
The tube mill is so referred to because it is long in proportion to its
diameter and, when first used in the industry, it used chiefly stone or
ceramic linings and pebbles as grinding media. The diameter of the
balls and pebbles is determined by the size of the feed and the fineness
o f the product desired.
Two methods are used in the manufacture of portland cement—the
dry process and the wet process. In the dr}^ process the materials are
dried either separately or after proportioning and are then ground
to a fine powder. Air separators or classifiers are sometimes used to
segregate the coarse material from the fine particles, and the coarse
material is returned to the mill for further grinding. The fine par
ticles are conveyed to multiple storage bins or blending tanks ready
for kiln burning.
In the wet process, instead of drying the raw materials, water is
added at the time of grinding and the materials are reduced to a slurry.
The exact chemical mixture for the desired quality of clinker is
obtained by proportionate mixing or blending of different slurries in
correction or blending tanks, and the mixture is then passed into
storage tanks from which it is fed into the kilns.1
2
Industry opinion is divided as to the relative advantages o f either
the wet or the dry process. It would appear that the choice o f methods
is governed by the type of materials used. The wet process may be
preferable where the materials are so wet as to make drying costly,
where the materials may be so variable that an unusually good mix is
required, and where the plant may be so located that suppression o f
dust may be imperative.
On the other hand, the advocates of the dry process claim that less
power is needed for grinding where the dry process is utilized, that
less fuel is needed for kiln burning, and that methods of suppressing
the dust have been perfected.
ia Hadley, Earl J . : The Magic Powder, New York, G. P. Putnam ’s Sons, 1945, p. 310.
PORTLAND CEMENT
BY C O U R TESY O F
Fig. 2.— Miller watching performance of one of the large raw grinding mills.
M ARQ UETTE C EM EN T
M A N U F A C T U R IN G
CO.
Ox
LABOR REQUIREMENTS FOR CONSTRUCTION MATERIALS
BY C OURTESY O F
Fig. 3.— Kiln burner checking critical burning operation in the largest cement kiln.
M ARQ UETTE C E M E N T
M A N U F A C T U R IN G
CO.
7
PORTLAND CEM ENT
INDUSTRY COVERAGE AND METHODS OF D ATA COLLECTION
The data presented in this report are based on a field survey o f 52
plants. These constitute a stratified sample with respect to geographic
location, size o f plant, process of manufacture, source o f electric
power, and type o f fuel consumed.
Data were collected for periods in 1945 and the first quarter of 1946.
The characteristics of the sample are measured by comparison with
those o f the industry in 1945. The sample of 52 plants represents an
annual production of 47,543,037 barrels, as compared with 102,804,884
barrels produced in 141 active plants in 1945. O f the 81 wet process
plants and 60 dry process plants, active in 1945,28 and 24, respectively,
are included in this survey. In addition, 21 plants included in the
sample generated 37.7 percent of all electric power produced in the
cement industry and 38 plants accounted for 49.8 percent o f all power
purchased by the industry. Seven plants in the sample both purchased
and generated their power requirements.
Upon selection o f the sample, data were collected by field representa
tives located in the regional offices of the Bureau of Labor Statistics.
These representatives made the necessary contacts with plant officials
and, in the case of multiplant organizations, with management execu
tives at the central office, in obtaining labor requirements data and
valuable background information.
A normal period of the, company’s operation was decided upon and
for the most part this was the calendar year 1945. However, because
some companies had not resumed peacetime production and distribu
tion until the latter part o f 1945, a representative period was studied
in 1946.
M a n -H ou r Requirements in M anufacturing and M ill Operations
The 52 plants surveyed in the study, forming the basis for this
article, represent an aggregate annual rate of production of 47,543,037
barrels of cement, requiring a total of 23,020,523 man-hours of labor.
Table 1 shows total man-hours, for each of the major departments
of the plants, and the man-hours required to produce 100 barrels of
cement in 1945-46. Comparative data on man-hours per 100
barrels are also given for 1934.1
3
T able
1.—Man-Hour Requirements in Cement Manufacture, 1934 and 1945-46
Major departments of plants
Total man
hours (in
thousands)
Man-hours per 100 barrels
1945-46
1945-46
1934
All departments.........................
23,021
48.4
55.0
Quarrying....................................
Processing...................................
Shipping......................................
Maintenance..... .........................
M ill overhead...... .......................
Administration..........................
2,689
8,733
2,581
2,629
3,442
2,947
5.7
18.4
5.4
5.5
7.2
6.2
7.7
18.0
6.3
16.0
i 9.6
7.4
1 Adjusted for transfer of yard operation from maintenance to mill overhead
3 F or 1934 study see M onthly Labor Review, M arch 1936 (pp. 5 6 4 -5 7 7 ).
3
8
LABOR REQUIREMENTS FOR CONSTRUCTION MATERIALS
In general, fewer man-hours were required to produce 100 barrels of
cement in 1945-46 than 12 years earlier. There were wide deviations
from the average in some plants. The basic factors affecting labor
requirements— such as rate of production, size of plant, age of plant,
number and size of kilns, and degree of mechanization—in 1945-46
remain the same as pertained to the study made in 1934. Certain
functions necessary for operation of the cement plant are performed
by plant employees in some cases and thus appear as man-hour re
quirements, but in other instances appear only as cost items (for ex
ample, purchased electric power, purchased quarry materials, and
contracts for shipping).
QUARRYING OPERATIONS
The materials obtained from the quarry are usually located on or
adjacent to the plant site and man-hours necessary for delivery of
these materials to the plant are included in the requirements shown
for this department. Estimates of man-hours required for produc
9
PORTLAND CEM ENT
tion and transportation of raw materials other than those obtained
from the quarry are presented in a following section.
A substantial reduction in quarrying operations of 2.0 man-hours
per 100 barrels of finished cement was effected between 1934 and
1945-46. In the 52 reporting plants, total man-hours in the 1945-46
period were 2,688,858, and the average per 100 barrels was 5.7 man
hours. The range in individual plants was from 1.2 to 19.7 man
hours per 100 barrels.
One reason for the reduction in man-hours in the past 11 years, as
well as for the variation in man-hour requirements in this study, was
the improvement in quarrying machinery. More general use of elec
tric and Diesel-powered shovels with increased capacity and greater
mobility was largely responsible. Steam shovels, which require an
extra man for firing in addition to the operator are gradually being
discontinued. In some plants the use of Diesel trucks has resulted
in greater efficiency and flexibility in the quarrying operation.
PROCESSING DEPARTMENT
In 1945-46, 52 plants accounted for 8,732,921 hours of employment
in the processing department. To process 100 barrels of cement re
quired an average of 18.4 man-hours for all plants, an increase of 0.4
man-hours since 1934.
The data presented reflect only a slight change in man-hour require
ments since 1934. This tends to understate the actual change in
productivity, because specifications became more exacting in the
intervening period. Technical improvements have kept pace with
changes in specifications which required improvement in quality of
the finished product, thus holding down the man-hour requirements
per unit produced near the level shown for 1934. Considering the
more exacting specifications, the fact that the data show little change
in man-hour requirements in the two periods studied is indicative of a
marked improvement in productivity for the processing department.
Labor turn-over and labor shortages were felt by all plants in this
department until late in 1945. The effects of the war in drawing off
trained men created acute labor shortages, which resulted in the use
of inexperienced labor in semiskilled and skilled jobs and tended to
limit reductions in man-hour requirements which might normally
have occurred in processing operations. The trend is now being re
versed as discharged servicemen return to their former employers
and as activities in war industries terminate.
The processing department is divided into five operational functions
or sections. The average number of man-hours expended per 100
barrels in 1945-46, by processing functions, as compared with the
earlier study in 1934, were as follows:
Man-hours per 100 barrels
1945-46
1994
All sections_______________ ______ 18.4
18.0
Raw department__________ ______"575
Clinker department_______ ______ 5.2
Finishing department_____ ______ 3. 1
Coal mills_____ __ _ __ ______ 1.3
Power department________ ______ 3.3
~5~2
46
3.1
1.5
3.6
10
LABOR REQUIREMENTS FOR CONSTRUCTION MATERIALS
The raw department man-hour requirement per 100 barrels in
1945-46 was 5.5. This exceeded the requirement in 1934 by 0.3
man-hour. In the clinker department, where the raw materials are
burned in the kiln, man-hours increased 0.6; and in the finishing de
partment, where the clinker is finally pulverized, gypsum is added,
and the finished product is produced, no change occurred in the man
hour requirement.
chart
z
MAN-HOURS REQUIRED
BY OPERATIONAL FUNCTIONS
IN PROCESSING DEPARTMENT
TO
PRO DUCE
IOO B A R R ELS
OF CEM ENT
MAN-HOURS PER IOO BARRELS
5______________ 10______________ 15
TOTAL
PROCESSING
RAW
DEPARTMENT
CLINKER
DEPARTMENT
FINISHING
DEPARTMENT
COAL M IL L S
POWER
DEPARTMENT
UNITEO STATES DEPARTMENT OP LABOR
BUREAU OF LABOR STATISTICS
For each 100 barrels of output, 1.3 hours were expended in the coal
mills, where coal is treated and prepared for firing of the kilns. This
average is based on tbe production of all plants, without regard to
type of fuel used. Variations are considerable among the cement
plants, depending upon the type of fuel used. In plants where gas or
oil is the primary fuel, there are no requirements for fuel preparation.
A break-down was prepared showing man-hours required for those
plants which used coal exclusively as compared with those which used
natural gas, fuel oil, or combinations thereof with coal. Plants which
used coal exclusively required 2.0 man-hours of employment per 100
PORTLAND CEM E N T
11
barrels, while those which used, in addition to coal, fuels which did
not have to be treated (for example, oil and natural gas), had 1.1
man-hours per 100 barrels.
In the power department, 3.3 man-hours were needed for each 100
barrels of output. The average decrease since 1934 in this depart
ment was 0.3 man-hour. Data for this department can be separated
into plants which generate their own power and plants which pur
chase power from a utility. The latter plants, in which the functions
of the power department are limited to distributing the purchased
energy, require relatively fewer man-hours.
Analysis of 43 reporting plants showed that 12 plants generated
all the power they consumed. To produce 100 barrels of cement,
these 12 plants required an average of 7.4 man-hours in the power
department. Twenty-five plants purchased their power supply from
local utilities and, accordingly, only 2.1 man-hours were required in
their power departments. In addition to these two groups of plants,
there were six which generated part of their power requirements. In
most cases the amount of purchased power was considerably less than
that generated and the man-hour requirement, was 6.0 per 100 barrels
of cement produced.
SHIPPING DEPARTMENT
The shipping department has two main functions: (1) Packing and
loading and (2) bag handling and repairs. Upon completion of the
manufacturing process, cement is stored in bulk in bins and silos and
held for shipment. Depending upon instructions from the customer,
shipments may be made in bulk, or in paper or cloth bags. Infor
mation gained in the field indicates that the trend among most cement
plants is to increase shipments in bulk and in paper bags and to de
crease shipments in cloth bags, eliminating not only some adminis
trative expense involved in the accounting procedure for cloth-bag
refunds and returns but also the cost of sorting, cleaning, and repair
ing returned bags.
In a special study of a portion of the sample, the shipments of 31
plants were analyzed. The total shipped by these plants during the
period studied was 24,080,787 barrels. Of this total, 27.6 percent
was shipped in bulk, 50.1 percent in paper bags, and only 22.3 percent
in cloth bags. The above figure of 24,080,787 barrels represents
48.0 percent of the total shipments from the 52 plants.
In terms of man-hours of employment per 100 barrels of cement,
5.4 hours were required in the shipping operation during 1945-46.
This is a decrease of 0.9 from the 6.3 man-hours reported in the 1934
study. Bag handling and repair accounted for 0.8 man-hour per 100
barrels, and packing and loading for 4.6 man-hours. Total man-hours
in the shipping department for the 52 plants studied were 2,581,387.
The range between plants was from 0.6 to 15.9 man-hours.
MAINTENANCE AND OVERHEAD
Maintenance.— In general, maintenance work includes the labor of
the shop and repair gangs which overhaul the machinery during periods
of shut-down. In 1945-46 yard employment data have been trans-
12
LABOR REQUIREMENTS FOR CONSTRUCTION MATERIALS
ferred to the mill overhead department.
maintenance operations are as follows:
The man-hours required for
Man-hours per 100 barrels
1945-46
1934
Total maintenance_______ ________5.5
6 .0
.S h op ____________________ ________ 2 .0
Repair gang______________________ 3.5
2. 4
3 .6
Man-hour requirements per 100 barrels for this department de
creased 0.5 since 1934. This can be attributed largely to labor short
ages and curtailment of maintenance operations during the war years,
as well as through 1945. Information collected in the field indicates
that plans for extensive maintenance operations on the part of many
cement manufacturers will increase the man-hour requirements for
this department in the immediate future.
M ill overhead.— Data showing the average number of man-hours
charged to overhead, as compared with the 1934 survey, are given
below:
Man-hours per 100 barrels
1945-46
1964
Total mill overhead______________ 7. 2
9. 6
MH1 office_________________________ 1.4
Storeroom_________________________ .5
Laboratory_______________________ 1. 5
Superintendents and foremen ____ 1.2
Watchmen________________________
.6
Yard______________________________ 1.6
Miscellaneous labor___ ____________ .4
1.5
.6
2. 1
1.5
.8
2.5
.6
The labor shortage during the period studied was, as in the mainte
nance department, a large contributing factor in the decrease as com
pared with 1934. Greater reductions in employment can be expected
in overhead operations than in production operations when labor
shortages develop. Should an adequate labor supply lead to in
creased employment in this department, average requirements per
unit produced may remain stabilized near the level here shown
for 1945-46, if anticipated increases in the production of cement
materialize.
ADMINISTRATIVE DEPARTMENT
This department includes the employment necessary to operate
the general offices and selling organizations. Because many plants
kept inadequate man-hour records for these employees, a special
study of 23 plants was made. Upon this basis, it was estimated that
the average number of man-hours required per 100 barrels of produc
tion was 6.2, and that 2,946,633 hours of employment were required
for the administrative functions in the 52 sample plants.
Variations in Labor Requirements
BY RATE OF OPERATION AND PLANT CAPACITY
In determining the man-hours necessary to produce 100 barrels of
cement, the rate of operation and the plant capacity should be taken
13
PORTLAND CEM ENT
CHART 3
MAN-HOURS REQUIRED
BY ANNUAL PLANT CAPACITY
TO
PRO DU CE 1 0 0 B A R R E LS
1945 — 1946
OF
C EM EN T
MAN-HOURS PER 100 BARRELS-^
CAPACITY
(THOUSANOt
OF 0BLS.)
ALL
PLANTS
UNDER
1,000
1,000
AND UNDER
1.500
1.500
AND UNDER
2,000
2,000
AW
N
E
R
2 .5 0 0
AND
OVER
QUARRYING
SHIPPING
MANUFACTURING
UNITED STATES DEPARTMENT OF LABOR
BUREAU OF LABOR STATISTICS
P d o e s NOT INCLUOE
ADMINISTRATIVE LABOR
into account. From table 2, it is apparent that as percent of capacity
utilized approaches the maximum, the total man-hours required in
all departments are generally lower. From table 3, it appears that
the larger producers tend to show greater efficiency in manufacturing
operations.
T a b l e 2 . —Average
Number o f Man-Hours Required to Produce 100 Barrels of Cement
in 1945-46, by Rate of Operation
Man-hours per 100 barrels
Percent of capacity utilized
Number of
plants
Total i
Quarrying
Manufac
turing i
Shipping
All plants......................................................
52
42.2
5.7
31.1
5.4
Less than 40 percent.....................................
40 to 60 percent.............................................
60 to 80 percent------- -----------------------------80 to 100 percent.......................... ......... .. -
12
24
9
7
49.6
50.3
38.9
25.4
5.4
6.8
4.9
4.6
38.5
37.2
29.0
16.6
5.7
6.3
5.0
4.2
>Does not include administrative labor.
14
LABOK REQUIREMENTS FOR CONSTRUCTION MATERIALS
The greatest variation in man-hours exists in the manufacturing
process. In plants operating at more than 80 percent of capacity, as
shown in table 2, only 16.6 man-hours per 100 barrels of production
were required in manufacturing, whereas those operating at less than
40 percent of capacity required 38.5 man-hours. The average re
quirement for all plants was 31.1 man-hours.
Table 3 furnishes a break-down of the 52 plants of the sample accord
ing to capacity in 1945-46. Again, a wide range occtirs in the manu
facturing departments, with the largest producers reporting 24.7
man-hours per 100 barrels and the smallest 39.9.
T a b l e 3 . —Average
Number o f Man-Hours Required to Produce 100 Barrels of Cement
in 1945-46, by Annum Plant Capacity
Man-hours per 100 barrels
Number of
plants
Capacity
T otal1
All p lants.._________________________ _
Quarrying
Manufac
turing i
Shipping
1,500,000 to 2,000,000 barrels.......................
1,000,000 to 1,500,000 barrels. ....................
Under 1,000,000 barrels. _
____________
52
42.2
5.7
31.1
5.4
8
O ver 2,500,000 barrels
2,000,000 to 2,500,000 harrp.la
33.1
37.4
44.9
51.0
54.2
4.1
5.5
5.5
24.7
26.7
33.9
37.1
39.9
4.3
5.2
5. 5
7.3
5.0
5
10
17
12
6 .6
9.3
1 Does not include administrative labor.
BY GEOGRAPHIC AREAS
The variations in labor requirements among geographic areas, for
the 52 plants studied, are shown in table 4. Plants in the Pacific
States lead in productivity, with the plants in the Southeast next in
order. On the basis of productivity, the relative position of plants
in the Pacific States remains unchanged since 1934. Plants in the
Mountain States show the highest man-hour requirements, 60.2
man-hours per 100 barrels. Plants in the Lehigh Valley area are
nearest the average of all plants included in the survey with 41.1 man
hours per 100 barrels. Among the factors which affect the range of
man-hour requirements by geographic areas are production rate, size
of plant, age of plant and equipment, process of manufacture, and
type of fuel used.
T a b l e 4 . —Average
Number o f Man-Hours Required to Produce 100 Barrels o f Cement
in 1945-46, by Geographic Area
Area
Number
Annual
of
plants production
Man-hours per 100 barrels
Total i
Quarrying
Manufac
turing i
Shipping
All areas_____________________
52
Barrels
47,543,000
42.2
5.7
31.1
5.4
Pacific
__ _ _ .
Snnthpast
Lehigh Valley________________
Middle West...............................
Northeast...... .............................
Southwest................. .................
Mountain...................................
6
5
4
15
6
11
5
9.012.000
5.955.000
5.485.000
14,334,000
3.887.000
6.649.000
2.221.000
24.6
38.7
41.1
45.8
47.4
53.8
60.2
4.8
5.7
5.3
5.9
4.9
6.5
7.5
16.0
27.0
29.8
34.5
37.0
40.9
46.1
3.8
6.0
6.0
5.4
5.5
6.4
6.6
i Does not include administrative labor.
15
PORTLAND CEM ENT
Total M a n -H ou r Requirements fo r Production and Transportation
The preceding sections have developed in detail, from basic plant
records, the man-hours required at the plant to manufacture 100 barrels
of cement. The following section estimates the additional man
hours required to extract those raw materials not hitherto considered,
to haul these materials to the plant, and to transport the finished
cement to the construction site.
CHART 4
MAN-HOURS REQUIRED TO PRODUCE
100 BARRELS OF CEMENT
MAN-HOURS PER 100 BARRELS
PRODUCTION.
RAW MATERIALS
H
H
TRANSPORTATION. R K 3 R
RAW MATERIALS BSSI
QUARRYING. MANUFACTURING.
SHIPPING AND ADMINISTRATION
TRANSPORTATION
FINISHED CEMENT
DEPARTMENT OF LABOR
BUREAU OF LABOR STATISTICS
These operations (production of additional raw materials, and
transportation), as indicated below, require an estimated 52.1 man
hours in addition to the 48.4 required at the plant. Thus, 100 barrels
of cement delivered to a job site represent an over-all investment of
approximately 100.5 man-hours of labor.
Man-hours per 100 barrels
1984
ms-46
Total production and transportation------------------------------- 100. 5
126. 4
Raw materials, production______________________________ 1 13. 0
Raw materials, transportation---------- ------------------------------ 10.6
Quarrying, manufacturing, shipping and administration. _ 48. 4
Transportation, finished cement_________________________ 28. 5
1 14. 1
6.6
55. 0
50. 7
i Includes purchased electric power.
PRODUCTION OF RAW MATERIALS
The materials used in cement manufacture are in the main (1)
limestone, shale, clay, and other materials obtained from the plant's
quarry, (2) gypsum, and (3) coal. Usually the first of these materials
is obtained from a quarry located on or adjacent to a plant site, and
this operation is covered in the man-hours required for the manufac
turing process.
16
LABOR REQUIREMENTS FOR CONSTRUCTION MATERIALS
Required quantities (to produce 100 barrels of cement) of the mate
rials not considered under manufacturing and mill operations, includ
ing power are shown in the statement following.
Requirements per 100 barrels, 1945-46
Man-hours
to produce
Amount of
quantities
materials
consumed
Materials:1 T o ta l-...............................................
Gypsum.............. .......... ............................ 0. 66 ton
Coal------------------------------------------------- 6. 29 tons
Power (purchased)_________ ________ 1,355 kw.-hr.
13.0
.6
8. 3
4.2
1 Steel, for which requirements were indicated in the 1934 study, is not represented here because its use in
the finish grinding and cloth-bag tying operations has substantially decreased.
Gypsum.—The amount of gypsum—0.66 ton consumed per 100
barrels—was obtained by dividing 683,158 tons, the amount used
in 1945 in cement manufacture, by the total 1945 production of cement,
102,804,884 barrels.1 The man-hour requirements for producing 1
4
ton o f raw gypsum, which were obtained by dividing total man-hours
used in the production o f gypsum (2,616,928) by the total number o f
short tons produced (3,761,234)1 are 0.70. On this basis, the man
4
hour requirements for the gypsum used in 100 barrels o f cement are
0.46.
Goal.— The amount of coal consumed per 100 barrels o f cement
was obtained by dividing the total amount used in 1945 in those
cement plants using coal only (3,481,492 tons) by the total amount
o f cement produced in those plants (55,347,915 barrels1 ) . The aver
4
age coal consumption to produce 100 barrels of cement was 6.29 tons,
or 125 pounds per barrel.
The U. S. Bureau of Mines estimates that 1.32 man-hours were
required per ton for bituminous coal production in 1945. (The de
crease from the 1.65 man-hours required in 1934 is confirmed by the
Bureau o f Labor Statistics productivity index for bituminous coal.)
Thus, 8.30 man-hours were needed to produce the coal consumed in
manufacturing 100 barrels o f cement. This represents a slight over
statement-of average fuel requirements, however, since some plants
use natural gas and oil, the labor requirements for which it is assumed
are less than those for coal.
Pow er.—The use of electric power is a vital factor in the production
o f cement. Power used in cement plants is either generated at the
plant or purchased from utilities. The man-hour requirements for
power generation at the cement plant are already included in cement
plant operations. An estimate, however, is necessary for the amount
o f labor required to produce the energy purchased from utilities.
O f the 2,512,083,5041 kilowatt-hours used in cement manufacture
4
in 1945, 1,393,234,2101 were purchased. Thus, although 2,445 kilo
4
watt-hours o f electric power were used per 100 barrels of cement
produced, the average requirement in all plants for purchased power
only was 1,355 kilowatt-hours.
The Bureau of Labor Statistics estimates that the average 1945
employment in privately operated electric energy generation and
14 S o u rce : U. S. Bureau o f Mines.
PORTLAND CEMENT
BY C O U R TE S Y O F
M ARQ UETTE C E M E N T
M A N U F A C T U R IN G C O .
Fig. 4.— Attendant checking the important vacuum on a big turbogenerator. (A cement plant of average size consumes as
much power as a city of 30,000 population.)
18
LABOR REQUIREMENTS FOR CONSTRUCTION MATERIALS
distribution stations was 205,000. These employees averaged 45.5
weekly hours for the year. The amount of power generated by
privately operated plants during 1945 was 180.9 billion kilowatthours.. Thus, the labor requirements for electric power were 2.681
5
man-hours per thousand kilowatt-hours, or 3.63 man-hours for the
amount o f power necessary to produce 100 barrels o f cement.
The total amount o f coal used in electric power generation in 1945
was 74,747,968 short tons,1 and the total power generated (all types of
6
prime mover) was 222,433,981,000 kilowatt-hours.1 Therefore, the
6
average coal consumption was 0.33605 ton per 1,000 kilowatt-hours.
Thus, it was estimated that 0.601 man-hour was expended on the fuel
requirements for generating the electricity purchased to produce 100
barrels o f cement. This fuel requirement is somewhat understated
because substantial amounts of natural gas and oil are used in power
generation, but no data were available to determine the man-hour re
quirements for gas and oil production. It is believed, however, that
omission o f these should introduce a comparatively slight error.
A total o f 4.23 man-hours was thus required to produce the quantity
o f purchased electrical energy necessary to manufacture 100 barrels of
cement.
Data were not available to estimate the employment created by all
the purchases o f cement mills for materials used in small quantities,
such as sacks, lubricants, explosives, and repair parts. Inasmuch as
quantities o f these materials were very small in relation to total pro
duction o f cement, the lack of these man-hour estimates would have
negligible effect on the total estimate of labor requirements.
TRANSPORTATION OF RAW MATERIALS
In addition to the labor involved in extracting the raw materials,
a substantial number of man-hours are required to transport them
from their source to the cement plant. No direct measurement of
these man-hours was attempted in the present survey, but published
data o f the Bureau afford a basis for computing rough estimates.
These indicated that; the requirements for the transportation of raw
materials were as follow s:
Estimated
man-hours per 100
barrels, 1945-46
Materials: Total_____________________ 10.63
’C oal______________ ,___________________
Gypsum------------------------------------------ -
9.62
1.01
Coal.—An analysis, in 1937,1 of the railway statistics of the Inter7
State Commerce Commission and the Bureau of Kailway Economics
1 This exceeds the estimate o f 1.64 man-hours per kilowatt-hour fo r electrical energy
5
generated in 1934, in spite o f a sharp rise in the productivity index fo r electrical energy
production over the 10-year period. However, the first survey took into account only gen
erating plant employees, whereas the 1945 figure includes the requirements fo r all workers
employed by pow er companies, including generating, distribution, maintenance, and other
employees.
16 Source : U. S. Federal Power Commission.
17 See M onthly Labor Review, October 1937 (pp. 846-853) : Labor Requirements in R ail
T ransportation o f C onstruction M aterials, by John A. B all (reprinted as a separate, Serial
19
PORTLAND CEM E N T
indicated that approximately 1.531 man-hours were needed in 1935
8
to transport one ton o f bituminous coal for its average haul o f 364
miles. Thus, the 6.29 tons of coal required in the manufacture of 100
barrels o f cement (see p. 16) necessitates about 9.62 hours o f labor
by railroad workers.
Gypsum.—The labor requirements for the transportation of gypsum
were not determined in the 1937 study. Therefore, to complete the
estimate for the materials transportation requirements, it was assumed,
from the distribution of gypsum deposits and the nature of the ma
terial, that the man-hours factor for bituminous coal could be substi
tuted. On this basis, hauling to the plant the 0.66 ton of gypsum used
in the production of 100 barrels of cement necessitated about 1.01 man
hours of labor. The total requirements for materials transportation
to the plant were, therefore, approximately 10.63 man-hours.
TRANSPORTATION OF FINISHED CEMENT
The man-hours needed to transport finished cement from the plant
to the point o f use are summarized below:
Man-hours for 100
barrels* 1945-46
Total transportation__________________ 28.47
From plant to railhead________________ 16.17
From railhead to construction site___ 12.30
Plant to railhead.—Finished cement is transported from the plant
by road, water, or rail. However, about 80 percent is currently hauled
by ra il1 and, therefore, in the absence of data relating to the other
4
carriers, the outbound transportation requirements are estimated solely
with reference to the rail study previously cited. That study indicated
that 0.86 man-hour was needed to move 1 ton o f cement over its average
haul of 198 miles. Thus 18.8 tons, the weight of 100 barrels of cement,
require an average of 16.17 man-hours of employment for the haul
from plant to construction site railhead. It will be noted that this
represents a marked decrease from the 38.4 man-hours estimated in the
earlier study of labor requirements in cement production. It appears,
however, that this decrease is attributable chiefly to the inadequacy of
the data on which the previous estimate was necessarily based, rather
than to a sharp increase in freight-handling productivity. The trans
portation study referred to in this report was not then available, and
the earlier estimate was therefore based on the freight charge statistics
of the Interstate Commerce Commission.
Railhead to construction site.—In addition to the man-hours ex
pended in the rail haul of the finished cement, labor was required to un
load it from the freight car and to truck it to the construction site. The
earlier estimates for these operations were 10.0 and 2.3 hours, respec
tively. Since no basis for revising these estimates are available, they
1 S o u rce : U. S. Bureau o f Mines.
4
1
8 T w o series o f index numbers relating to productivity in railroad freight transportation
are m aintained by the Bureau. One o f these describes the changes in productivity in terms
o f the tons o f freight m oved per man-hour, and the other in terms o f the car-miles o f freight
handled per man-hour. Since the form er o f these measures increases in the 10 years
1935-45, and the latter decreases, and since neither measure is applicable, in the absence of
additional inform ation, to the transportation requirements data developed in the 1937 sur
vey, it seemed inadvisable to try to adjust this figure (1.53) for the change in productivity
since the original study.
20
LABOR REQUIREMENTS FOR CONSTRUCTION MATERIALS
have been incorporated unchanged in the current survey. The total
labor requirements for the haul from the railroad to the job site are
therefore 12.3 man-hours.
Trend o f Productivity, 1930 to 1945
According to data prepared by the U. S. Bureau of Mines, output
per man-hour of quarrying and manufacturing labor in the cement
industry increased from 1.79 barrels in 1930 to 2.59 barrels in 1942,1
9
the year in which the highest rate of productivity has been achieved.
The rather steady trend toward greater productivity was interrupted
during the depression of the thirties and again during the war years.
Construction of new plants and modernization of many old ones
appear to be largely responsible for the increase in output per man
hour during the first 8 years of the series shown below. Changes in
productivity in recent years, however, tend to vary directly with the
rate of capacity utilization. In 1942, when the highest rate of
capacity utilization was reached, the number of barrels produced per
man-hour was 2.59, whereas in 1944, when capacity utilization dropped
sharply, the number of barrels produced was 1.99. In 1945, however,
with increased production and plant utilization, output per man-hour
again increased, reaching 2.10 barrels per man-hour.
The average number of barrels of cement produced per man-hour
and the number of man-hours required in the production of 100
barrels for each year, 1930 to 1945, are shown below:
Average number o
B a rrd s
produced
p er m an
hour
i
1930______ _ ___ _______1.7 9
1931....................... _______2 .0 7
1932___________ _______2 .0 0
1933___________ _______2.0 1
1934....................... _______2 .0 6
1935___________ ............. 1 .9 6
1936___________ _______2. 19
1937___________ ............. 2. 12
* Data are from U. S. Bureau of Mines.
administrative,
a Preliminary.
f
M an -h ours
required to
produce 100
barrels
A
v
e
r
a
g
e
Barrels
produced
per m an
hour 1
number of—
M a n -h ou rs
required to
produce 100
ba rrels
*
1
5 6 .0 1938.................. _________ 2 .2 1
45. 3
48. 2 1939_________ _________ 2 .3 8
42. 0
50. 1 1940_________ _________ 2 .4 0
41. 7
49. 7 1941_________ _________ 2. 57
38. 9
48. 6 1942_________ _________ 2 .5 9
38. 5
51. 1 1943_________ _________ 2. 25
44. 4
45. 6 1944_________ _________ 1 .9 9
5 0 .3
47. 1 1945 2_______ _________ 2. 10
47. 6
Includes quarrying labor and all manufacturing labor except
1 Except for materials quarried by cement plants, these data do not include the labor required in the
9
production and transportation of raw materials, administrative labor in cement plants, or the labor
required in transportation of the finished product to the construction site.
21
PORTLAND CEM ENT
CHART S
PRODUCTIVITY IN
CEMENT MANUFACTURE
MAN
HOURS
M AN
HOURS
60
60
50
50
40
AA
30
30
20
20
10
10
__ 1_ 1__ 1__ 1__
_
a
1930
1935
A
1940
IN C L U D E S Q U A R R YIN G L A B O R AND A L L M A N U F A C TU R IN G
L A B O R E X C E P T A D M IN IS T R A T IV E
UNITED STATES DEPARTMENT OF LABOR
BUREAU OF LABOR STATISTICS
1945
