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AN EXPERIMENTAL smn'vor THE . .
' mm on CONCRETE or. HEATING.
AGGREGATES T0 man TEMPERATUR£S

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An Experimental Stuéy of the Effect on

Concrete of H,ct1ng Aggregates

to High Temperatures

A Thesis Submitted to

The Faculty of
FICHIGAH STATE COLLEGE
of

fiGRICULTURE AID AP?LJ?D SCIEXCE

DYw

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H; R. “33306

Candidate for the Degree of

Bachelor of Science

June 1933

JHESIE.

Acknowledgment

The author of this Thesis is greatly indebted to
L. J. Rothgery, Pref. C. L. Allen, and to those other
members of the richigan State College Faculty, without
whose advice and valuable assistance these experiments

would have been impossible.

Introduction

During the last few years there has been more and
more winter construction taking place. There have been
various methods of heating aggregates for this winter
construction. some of which heat the aggregate in the near
vicinity of the heating elements to a very high temperature.
There have been no extensive experiments to determine the
effect of this heating to a high tcmnerature on the strength
of the finished concrete. The purpose of these experiments
was to determ no the effect, if any, of this heating on

the strength of the finished concrete.

Test Specimens

The concrete used in the sneciaens was desimned for a
strength of fifteen pounds oer square inch according to the
water cement ratio theory. The sand used was a graded clean
sand with a gratin: between 0" and 1/4" and with a fineness
modulus of 1.99. The course agareaate used was made up by
mixing 3/4" and 1/2" stone in equal parts, which gave a
fineness modulus of 7.54. The mixing for the cylinders was
done in a mixing pan by hand. The mixing for the beans was
done in a 2 1/2 cutie foot faith mixer. Curve "a" was used
in the desirn of the mix. Each hatch was tested for slump,
and a consistency of 5" to 6" slump was maintained.

The molds for the beams were made from 8" channel
sections to give a beam 6" x 8“ x 36" beam. This was long
enough to give two breaks on each.bea1. The teams were broken
with the 8" side vertical. One break was made with the top
as poured and the other with the top down. This method of
breaking would tend to eliminate any irregularity that might
be due to segregation or variation in the concrete in the
beam. The cylinders were the standard cylinders, 6" in
diameter and 12" hifih.

all of the beams and cylinders were cured in the moist
curing room. All of the beams were cured for seven days only,
and part of the cylinders were cured for seven days, he rest
of them heinfi cured for twenty eifiht days. Before brcahing
the test pieces were allowed to dry for a few hours and then

brushed clean. The cylinders were canned on both ends in a

canning machine with leedite to insure an even hearing
over the whole surface. An Olson Universal Testing
finchine of 150,000 pounds Genocity was used. The beams
were festened in place between the steel plates of th
testing machine that was built as osrt of s thesis in

1930.

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Oven

The Oven

The even that was used for heating the aggregates was
built according to the enclosed droning. It is composed of
fire brick laid uo with snnll angles inhedded in the brick
at intervals to supeort the pans in which.the aggregates
were placed for heating. The inside dimensions of the oven
were 18" x 27" x 30" with the angles inbedded in every third
leyer of brick. The too of the oven was connosed of brick
held up by more smell angles, the creeks between the brichs
being greeted full of morter. The cement used to lay up
the oven was a soeciel heat resisting cement that would
stand a tennersture of about tnenty~five hundred degrees
fehrenheit. The door of the oven was hung with hinges from
the ten of the oven. It one mode up of a host insuleting
board and e pen of sheet iron with the two inch specs between
then filled with fingnesin.

The pens in which the aggresste use heated were made up
of eighteen gouge sheet iron. They were made 3" x 10" x 14"
so that all of the material placed in then would heat through
uniformly.

The oven was hosted with gas, the burners being mode of
pipe fittings. The gee was drnnn into, he burnerrnnd burned
zith.eir. The air was blown into the burner mixing chamber
through a smell Jet in sue. a say that the pressure in the
gee line was reduced and thus more gee was fed into the burner
than would otherwise have entered it. The details of this

n King chamber are shown on the enclosed shetch.

The temnerature in the oven was rend with the aid of a
thermocevnle and a millivelt meter along with a cali‘ration
curve for the ceuple used.The theraoceuele was inserted into
the oven throunh a hole left for that nernese in the top of

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fiethod of treating egaremctes

The aggregates to he used in a batch of concrete to be
made into test snecinens was weighed out nsvrexinetely and
p seed in the pens for heating. Each type of aggregate was
kept in a pan by itself during heating. The pens were then
placed in the oven, the name with the sand being placed or
the bottom angles and the ceérse stone was nut on the angles
n,xt to the tee of the oven. The burners were then lit and
turned un until a long flame with a light blue inner cone
wee nroduced. Tle temperature was checked from time to time
as the oven would not rise at too fast a rate. When the oven
and contents had reached nearly the desired heat the burners
were turned down so that the tensernture would come up to
the desired value very slowly. Then the oven and contents
had reached the desired temnerature, the burners were turned
down very low and the temeerature in the oven was held cons-
tant for a period of twenty minutes. The object of doing this
was to mare sure that ell of the segregate in the even had
reached the desired temnerature.

After the even had been heated to the desired temnereture
it was hon allowed to cool off with all of the contents still
inside. The heating of a batch.was dens one day and the cool—
ing off was nllened to go on over night and the batch was

nixed up the next day.

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.1en the treated agrregstes were ready to be mixed they
were again weighed out very accurately and then dumped in the

mixing pan and nixed into concrete. in the concrete for the

twenty eiiht day cylinders all of the hatches were made
with the echo amount of mixing ester. In the case of the
seven dcy cylinders and the test teens, the betches were

all made with a slump of five inches and he amount of
water used to do this was recorded. It use found that the
snnnles that had been heated to the higher teneersture
rejuired more mixing enter to give the same slums than did
the ssnnles that were heated to the lower tennerctures.

This would mean that when materials are heated to high tenn—
erstures they will reeuire more water to give that same
workability es when hosted to low temnerstures or when they
vre not heated at all. The results of the strength tests
show that there is no definite reletien between the tester:-
tu.es that the aggregates are heated to, and the strength

of the finished concrete.

Temperature

12000

11000

Control

p’
51
.h' -
52

Total
0013:) a

55.910
59.140
47,610
4&,100
49,700
47.720

9,030
43,190
39.690
47.530
43.750
43.570
38,610
42,610

force

Twenty eight day cylinders

Lbs 0 per
sq. in.

1.980
2.100
1,690
1,565
1.760
1,695
1,335
1.530
1;#05
1.685
1,550
1.545
1.370
11510

Average 1,627

Percent
variation from
average
19.2
29.0
3.9
3.8
8.2
4.2
14.8
6.1
13.6
3.5
4.7
5.0
15.8
7.2

Seven any cylinders

 

Fercent Water
Cylinder Total load Lbs. nor variation from
sq. in. average gals. per sack
12000 51 45,150 1,635 11.7 9.54
#2 53,050 1,875 23.1
11000 $1 23,550 1,010 30.9 9.00
$2 30,100 1,065 27.2
9500 f1 45,110 1,600 9.4 8.86
f2 40.650 1,440 1.6
800° $1 25.500 905 33.1 8.73
£2 25,310 897 38.7
650° 51 44,780 1,590 8.8 8.44
#2 45,830 1,625 11.1
5000 f1 99,820 1,710 23.7 8.15
£2 52,150 1,850 26.4
Control f1 40,850 1,450 .9 8.58
£2 45,830 1,625 11.0
Average 1,463

Beams

Eodulue of Percentage Water gale.
Beam Break rupture lbs. variation from per sack
per sq. in. average
1200 $1 291 ' 13.4 8.68
$2 313 5.4
1100 $1 319 5.1 8.29
£2 378 12.5
950 f1 3&2 1.8 7.92
#2 300 10.1
800 5’1 368 9.5 7.97
5:32 360 7.1
650 $1 555 5.6 7-49
#2 320 4.8
500 51 366 9.0 7.27
52 320 4.8
Control 51 342 1.8 7.72

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Conclueien

220 time that was available for these experiments was
not 1023 enough for 2 very comerehoneive study of the prob-
lem envelved. It was found that at some temrcrtturee there
was a ver1 *“r ed effect on the strength of the concrete.
its Gene temeerntures there 238 a marked increase in the
stren3th of the concrete but on other strengths there was
2 very 222291 decrease in the ctren3th of the concrete. The

r12t1.en3 in the etren3th 2t fiiT erent teewerfi eree did
not seem to follow 2n1y def in1te order or system. Pram the
above it will be see :1 tbfi t env definite concln- .2212 as to
the fitrengtll of co wrote, *21.th t‘ne cenait en enccmntered
would be superficial end probably erroneous.

It L29 founfi thet the heetln3 of the "3‘re"‘tee to the
higher temeereturee 22d the effect of incre22113 the 2:0unt
of mixing water required to give a definite slump. This
incre220 in the amount of mixing water nigh decrease the
stren3t11 of the conczete but the exeerimente did not Show

peeitivelv any such decreeee in the 0tren3th.

Riblio3rephy

Thesis: A Compnrieon of Concrete in Comwreesion
and in Flexure, and the construction of 2 Beam Testing
Ihchine.

Zenlon 2nd Jennings. 1930

 

 

 

 

 

 

mmHGAN STATE l,'I‘JI~.‘ERS|T‘.’ LIRPLHIES