Water. Concrete for MOBS should be of high quality, i. e., low 
slump, low water requirement, and high cement content. Assuming not 
less than 8 sacks of cement per cubic yard of concrete, and a water to 
cement ratio by weight of 0.4, the water required for each 1,000 cubic 
yards of concrete would be: 36,100 gallons. In addition, considerable 
water would be required for washing tools and mixers. In general, water 
for concrete should be of the same quality as drinking water. 
Ready-Mixed Concrete. Depending upon the potentially feasibile 
construction site locations, it may or may not be economical to con- 
struct a new concrete batching plant. In California, as of 1967, there 
were 62 companies operating 274 plants producing 8.8 million cubic yards 
of ready-mixed concrete; Oregon had 17 companies operating 22 plants 
producing 0.5 million cubic yards; and Washington had 21 companies op- 
erating 50 plants producing 1.2 million cubic yards. 
Collectively, the southern coastal and eastern seaboard states 
produce concrete vastly in excess of that produced in the three western 
coastal states; however, California produced 2.75 times more ready-mixed 
concrete than Texas, the second highest producing seaboard state. 
Within the U. S. as a whole, the number of plants producing annual 
quantities in excess of a specified level are indicated below. 
No. of Ready-Mix Plants 
Producing Quantities in Excess of 
134 100,000 cu. yds. 
65 200,000 
34 300,000 
25 400,000 
17 500 ,000 
Based on a 5-day, 40-hour week, each company that produced 500,000 cubic 
yards per year, averaged at least 1,900 cubic yards per day, or 240 per 
hour. 
Transit mixed (truck mounted mixer) concrete accounted for 76 per- 
cent of the total reported production during 1967. Central mixing 
(pre-mixed at plant, agitated in truck enroute), accounted for about 24 
percent. 
In the event that ready-mixed concrete were to be used, the disposal 
of truck mixer wash water and unused concrete may become a problem. A 
solution to this problem is offered by the National Ready-Mixed Concrete 
Association (1964). 
Ready-Mix Concrete Costs. Published data as to costs of various 
motions involved in the production of concrete are not to be found in 
the open literature. In lieu of information of this type which would 
be variable for different types of plant set-ups as well as dependent 
