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Concrete Cutter
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all surrounding Cities & Towns
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Thus
far the lines are a repetition of those already drawn in Fig. 215, the
remainder of the figure being omitted for simplicity. Since the point n in Fig.
215 is the end of the line from the trial pole o, which is parallel to the
closing line yz, and since the point n is a
definitely fixed point and determines the concrete abutment reactions
regardless of the position of the trial pole o, we may draw from n an
indefinite horizontal line, such as no', and we know that the pole of any force
diagram must be on this line if the closing line of the corresponding
equilibrium concrete polygon is to be a horizontal line. For example, we shall
select a point o' on this line at random.Concrete mills which are used further on in the process are similar in
general to the ball mills. After the raw materials have been drawn from their
respective bins and accurately proportioned by weighing they are delivered to a
screw conveyor which completes the mixing and delivers the combined material to
the tube mills. The tube mills are revolving cylinders half full of flint
pebbles or steel slugs which reduce the material continually being fed, into
practically the fineness of finished cement. At this point we are, however, long
way from the finished product.
All the tube mills deliver to the same conveyor,
which results in uniform product of the raw material mill as a whole. From the
tube 'Mills the material is fed into kilns by a system of conveyors. The kilns
are from 6 to 8 ft. in diameter and average about 125 ft. in length. They are
'lined with fire brick, and revolve at the rate of one revolution a minute and
it is estimated that it takes about one hour for one lot of material- to pass
through. Powdered soft coal, crude oil, or gas is used, as fuel, powdered coal
being most commonly used. It is blown into the kiln at the end opposite that at
which the raw material enters. The raw material entering as a powder is
gradually brought to the point of incipient fusion at a temperature of 25000 to
3200° Fahrenheit, producing clinkers varying in size from 4 in. up to 1/2 in.
in diameter. The clinker is red hot when discharged, but is quickly cooled by
sprays of water or cold air blasts which are played over the elevator and also
upon the clinker when delivered to the storage pile. From the kiln the clinker
may go either to the clinker storage pile or directly to the grinding
department. Before sending to the tube mills for the final grinding gypsum is
added either by hand or automatically. This, material is added to prevent the
cement from setting too quickly. Otherwise the cement would harden quickly and
develop but little strength.
The tube mills grind the clinker so fine that the
particles are less than 1/200 in. in size. It is now placed in storage to
season. Cement is placed on the market in bags weighing 94 lbs. net and barrels
of 376 lbs. net, four bags to the barrel: Cement must be stored in dry place,
for dampness is the one element fatal to its keeping quality. Dampness causes
the cement to become too lumpy and uneven to finish. From the center we shall
draw rays to the points shown. From the point shown, we shall draw a line
parallel to the intersection. Where this line intersects the force, draw a line
parallel to the ray. Where this intersects the force B, draw a line parallel to
the ray or. Where this intersects the force, draw a line parallel to the ray.
This line must intersect the point completely, which is on a horizontal line.
The concrete contractor should make some such drawing as here described, and
should demonstrate for him the accuracy of this law. This equilibrium concrete
polygon is merely one of an infinite number which, if acting as struts, would
hold these forces in equilibrium, but it combines the special condition that it
shall pass through the points y and z'. There are also an infinite number of
equilibrium concrete polygons which will hold these forces in equilibrium and
which will pass through the points y and z'.
Are You in Eliot Maine? Do You Need Concrete Cutting?
We Are Your Local
Concrete Cutter
Call 207-284-0788
We Service Eliot, ME and
all surrounding Cities & Towns
