Every evening, Wilmington daily commercial., 1922-02-04
HANDLING Of
Cement BRINGS Loss
n. c. Boyden In Address Makes
Plea for Mixing Of Good
Concrete Only.

H. &. Boyden during tho course OF
his address In the Levy Court room
last night on recent developments in
concrete. made a definite plea for the
mixing Of good concrete only. Ho
pointed out that over one billion dol
lars wna spent annually for cement
alone during each yenr and that. un-
der present conditions. a very large
percentage OF tho potential strength
which could be developed by this ce-
nent was lost. due to careleasness on
the part OF those handling II.
He deplored tho somewhat general
impression that a hit-or- miss COM
bination OF cement, sand, stone and
water produces concrete. whereas the
making OF concrete waA really an ex-
act science.
Mr.. Boydcn took up tho ingredients,
cement, aggregate and water, In turn,
and discussed the necessary quality OF
these for a proper and successful con-
crete. He told us that Portland ce-
ment w%s now being manufactured
by all the standard companies. to meet
the specifications OF the Society for
Testing Materials, and that, there
fore. the purchase OF any OF these
standard brands inSures tho purchaA-
or that this material met the require
ments. as the requisites for member
ship in the Portland Cement Asso-
citation was bound to produce cement
meeting these specifications.
As to sand. there was choice
necessary and he quoted the usual
specifications for sand as clean. sharp
and coarse. free from silt and loan
saying that recent tests from the lab
oratory would show that rounded par
ticles roll into place better than
sharp parishes and that the suh<ti-
tute OF the word hard" for sharp
In these specifications would produc,
: equally good results. Also, that IL hao
been found that flno sand which, how
ever. must be free from silt and loan
produces concrete to test as we'll n,
tho coarser material, A content OF {
10 per cent Of material passing III.
zoo mesh sieve was considered 10 b,
allowable. but n very small percent
, age OF vegetable matter or loan wa.
a found 20 greatly weaken the strength
/ OF the mixture. The presence OF thl
material can be determined by col
ourametric test, which calls for tn,
4 - - WI Hsssh btahlllf VI fEtllO ~
: proportion TO a definite quantity O
' sodium hydroxidc. allowed TO stan,
Tor "a hours, the result being deter
mined by the color Of the fluid abov
the sand after this period OF time. IL
!, recommended the use of sand whicl
: did not disoolor the fluid, or whicl
!, gave light straw color, but empha
!, sized tho danger OF using sand. part.c
!, ularly Of the dark brown color.
Coarse aggregate IN the usual speci
iications has been required to Be OF
:. hard substance. This, also, Mr.. Boy
den reported could be modified souaa
), what TO allow a general use Of Ioc1
materials and the consequent lower
Ing OF the cost of concrete for all pur
poses except where direct abrasiu
would be upon the surface OF the cor
creto ae In floors. sidewalks and roas
, ways. Concrete for use In these place
should contain a coarse axyreeai
having a French coefficient OF wear {
, not less than 6.
! The last element entering in N
~ makeup OF concrete. which has so O.
! ten been omitted from q specification
Is water. which has been proven
De one OF the most important ell.
ments or the concrete makeup. II
10 Tatio or cement-water content is n
real determination Of the concrei
! strength, not the proportions Of G.
y menr, sand and stone. only insofar /.
the greater proportion Of sand al
. stone requires the higher water COZ
tent to obtain the same plaotic:ty.
- Other details emphasized by n,
u Boyden were time OF mixing 81,
&c curing Of the final concrete as We
's important factors OF its streny,h