PORTLAND CEMENT Effects of Catalysis and Dispersion n. L.KENNEDY Dewey and Afmy Chemical Company, Cambridge, M a s .
The application of catalytic and dispersing phenomena to cement is described. The results show that advantages are to be obtained by such catalytic and dispening agents and that, without changing the nature of cements themselves, the technic of the manufacture of cement and concrete, like that of many other branches of industry, can be improved by the addition of minute amountsof properly chosen materials.
ECA CSE oi t l i e eiioniioiw benefits whicli otlier industries have derived from the use of ratalyzing, dispersing, and wetting agents, a luge amount of research ha.s been undertaken during receut years to ascertain wliether similar advantages could be obtained by tlrc aiklitim of such agents to cement. Xotablr results Irave her11 obtained. Desirable properties of concrete xvhicli, assuming that wellgraded sound aggreg:stt: is used. depend upon certnin usiiaI1y unnieasirrt~dproperties of cr~iientare: (a) high strength at all ages, ( h ) rliirability, (c) good u-orkability, (a) iirgligihle bleeding, aiid ( e ) impenncability. In addition, it is iniportant that a reinent sliould be rnpable of being strrrwl over estended pcrioils without rxressive deterioration. In an rlrort to imidify ceinents so as to errliance these properties, the research laboratories of this c o m ~ ~ a nhave y made exhaustive studies of the effects on cement of catalysts and of dispersing und wett,ing agents. These studies ha7.e led to the development of a catalytic and dispersing agent which, when interground wibli cement, improves the desired qoalitie,?. Tlris catalytic and dispersing agent is VdllCd TDA.
Description of TDA 111 cmriiectioii with other lines of research, these Ialnmtories haye had :is a niajor problem tlie inipruvement of the dispersion of pigmerits in aqueous suspensions, especinlly in connection with rubber latex and rubber dispersions. Early in t,his work it becanre evideiit that e ~ e nwell-trained scientists often confuse the wetting and dispersiiig properties of various agents sild also fail to rccogniae tirat air agent whieli will disperse one pipilent will not necessarily disperse anotlier. As a result of these studies severd dispersing agents with a wide range of usefulriess were developed. The idea X B S then conceived that some of these dispersing agents miglrt be of value in aiding the disiiersion of cements in the water used to make concretes. Microscopic examinations showed that, when xetted with usater, the smaller particles of ordinary Port,land cement have a strong tendency to agglomerate and act as a large clunip rather than as individual particles. Figure 1 shows a dilute suspension of a standard Portland cement in water. Tests showed that the addition of a small amount of the sodium salt of certain polymers of condensed naphthalene sulfonic acid (in the case of the early work, all-
proxinjutdy 0.1 per cent of tlie m i g h t of tlie ceinent) resulted ill alnrost coinplete dispersion of the particlcs as shown in Ilirirre 2 , ii photorrricrogralih of the sanie cement at the same fiireness and niagiiificrttirin as Figure 1 but with the dispersing agent riddnrl to tlie mixing water. Tlie pesence of this dispersing agent iiicreased the workaldit,y r i f the resulting concrete aiid, by taking advantage of the watsr reduction this made possible, resulted in coircretes of greater strength. Obviously, if it were possible to utilize workability vc&hout a rater reduction and ater strength, a decided advance in concrete technic would resolt. An extensive organic research program was iindcrt.akeu to develop such ti reagent. It was at first ainceircd tlint additions which would aid the wetting of the M e r foonil that such particles tiiigiit be of help. But it was irtit iiecessarily the case and that tliose agents which proveil successful in solving tlic problem probably owed their e&ts to catalysis and not to wetting. Triethauolamine was eventually selected as an almost ideal agent wliicdi is effective at. conceutratimis in the neighborhood of 0.025 per cent of the weight of the cenient.. The action ,ifsuch catalyst,s WILS foorril to be additive, tlre catalytic strength-pro(~rici~g agent functioiii~igtis such either with or without tire dispersing agent. It was furt.her found that not only was tlre rievelopinent of early strength brought ahoiit by catalysis but that an increase in strength was maintained at all ages. studies of the various properties of the resiilting concrete resulted iir blie forinulation of a mixture of sodiirrn and trietliunolaniine salts of the polymers of condensed nnpbtlialeire sulfonic acids, to wliielr as given the naiire "TUA." The prihlern then arose as to Iiow this early form of TllA should be added to cement. Altliougli effective \ h e n added to tlic gage water at the mixer, when added to the clinker during the griri~idingoperation, TUA vas iiot oiily unifor~nly and easily distribiitetl throughout tile ccinent but its presence WBS a distinct aid to the grirriliiig of the cement since it kept the grinding n r d i a cleaner arid more effect.ive and resulted in lower mill temperatures. I n its presence, mith a given rate US cliiiker input, the mills ground finer; conversely, with a
1 h U H B 1. DILUTE SUSPENFlGURE 2. SAME ARFIGURE 1 BION OF STANDAKD PORTLLND WITH DI~PERSIXQ AQENT ADDEU ( X 500) CEMENT IN WATER 500)
(x
963
IKDUSTRIhL AND ENGINEERISG CHEMISTRY
964
larger input and the same power consumption, the mills ground more clinker to the same fineness. To ensure its proper distribution and adsorption on all the cement particles (which is essential in order to realize its maximum efficiency), to prevent the removal of dry TDA in the dust that is usually drawn out from the mills, and also to facilitate the measuring of the comparatively minute quantities of TDA used, it was found advantageous to add the TDA to the clinker in an aqueous solution. This is the present practice. With a background of exhaustive laboratory tests, involving the breaking of more than ten thousand cylinders, actual mill tests with representative clinkers from the various manufacturing districts were then undertaken for the purpose of determining the action of this TDA under both favorable and adverse commercial conditions. Approximately 0.5 pound of this original compound was used per barrel of cement. However, although the dispersing agent itself had little or no effect upon the surface tension of its water solution, indications were found that, in the case of some cements, concretes made with it had slightly lower weights per cubic foot than those made with corresponding untreated cements. It is well known that ordinary concretes usually contain about 1 per cent by volume of included air. The observed differences were approximately 0.7 per cent by volume-i. e., differences of about 1 pound in the weight of a cubic foot of the concretes. Although the large amount of
TABLE Plant So.
1
2 3 4 5 2 6 7 8 8 9 9 10 11
12 13 14 15 16 17 18 19 4 20 21 13
_47 ,I.,
Location
Hudson Valley East Southwest Midwest Pacific Coast East Hudson Valley Southwest Midwest Midwest Southwest Southwest East East Pacific Coast Midwest Pacific Coast Pacific Coast Midwest East Midwest Midu-est Midwest Midwest Southwest .Midwest Midwest Southwest
Date Made
8/33 10/33 3/34 3/34 7/34 8/34 12/34 1/35 1/35 2/35 2/35 2/35 8/35 8/35 9/35 9/35 10/35 11/35 12/35 11/35 3/35 1/36 5/36 5/36 4/36 3/36 1/36 2/36
Average Minimum .\Iasimum 1
2
22
13 24 .I 5 11 .I 7 28 "9 17 30 22
East East Midwest Southwest Lehigh Valley East East East East East Southwest Lehigh Valley L e h i ~ hValley Midwest
9 133 10/33 5/34 12/34 8/35 8/35 8/35 8/35 10/35 11/35 11/35 12/35 12/35 1/36
A \ erage Minimum Maximum a
I.
air included when agents such as stearates and rosin are added is unquestionably detrimental, there is no evidence that any harmful effects are ever found t o be due to a slight increase in air inclusion. Severtheless, it was recognized that the ideal was a product which, while possessing all of the virtues of this original TDA, would not increase included air. Consequently, a search for a new dispersing agent, which involved a study of the properties and economic possibilities of many organic compounds, finally resulted in the selection of a derivative of lignin. I n combination with the original catalytic agent, this lignin derivative resulted in a new and doubly effective material which retained all the properties of the old TDA without including additional air. Only 0.25 pound of this material per barrel of cement is as effective as was 0.5 pound of the former modification. This new TDA, a mixture of triethanolamine salts and highly purified soluble calcium salts of modified lignin sulfonic acids, a t first known as "double-strength TDA," was offered t o cement manufacturers only after a thorough testing program including the breaking of over twenty thousand additional cylinders representing typical mixes with cements of widely varying characteristics and analyses, from mills in all sections of the country. Comniercial experience resulted in the elimination of the older type early in 1935 and the adoption of this new formula as standard. While a detailed discussion of all of the ways in which the
COMMERCIAL
TD-4 CEMESTS
Wagner Surface -Tensile StrengthCompressive Strengtha Area 1-day 3-day 28-day 1-day 3-day 28-day Slump" S q . cm./ gram --Pounds per square inch-TDA High Early-Strength Cements 2270 2500 2390 2330 2100 2310 2345 2110 2310 2470 2560 2550 2550 2620 2340 2840 2420 2600 2740 2840 2630 2910 2640 2530 2400 2780 2640 2340 2500 2100 2910
305 370 340 315 315
390 390 435 395 405
325 315 335 365 370 305 305 345 335 360 310 285 350 415 350 356 368 330 328 390 353 320 340 285 415
455 425 465 425 430 390 450 440 400 395 405 430 445 447 454 423 422 445 424 405 425 390 465
1970 2140 2190 1910 1540 1700 1870 2000 2170 1770 1920 1980 1570 1750 1890 1540 2190
240 305 250 205 180 170 200 175 200 215 260 250 190 193 215 170 305
365 370 360 310 255 255 295 280 290 280 365 335 310 297 310 255 370
515 455
. ,,
. ., ... ...
... ...
...
...
...
495
...
480 515 440
...
545
...
. .. .. . ... ,,,
..,
... 495 440 545
1535 1245 1720 1875 1790
3415 3370 3180 3745 3090
5390 5275 5630 6235 4515
1960 1730 2405 1380 2000 1790 1545 1860 1550 1900 2270 2300 2160
3Y25 2710 3640 3690 4375 3500 3720 3005 3370 3785 3450 3340 3415 3980 3500
5Y10 5110 5050 5520 6395 5550 5130 5465 5690 5615 4950 4550 5585 5465 5820
..
1815 1815 1230 1790 1230 2405
..
3900 3529 2525 3490 2525 4375
.. ..
5470 5450 4890 5425 4515 6395
TD.i Xormal Cemen t s 4900 420 630 2320 5275 ,, . 1245 3370 5545 ... 1850 3710 3830 ... 810 1960 3875 860 1880 4425 . ., 735 1900 4020 400 730 2090 3975 430 820 1900 5540 465 1125 2370 3105 ... 815 1875 4180 , ,. 935 2345 4910 . ., 1180 2595 4995 385 530 1950 .. .. 502 4505 945 2330 435 3105 530 1875 385 5545 3710 502 1850
...
VOL. 28, NO. 8
6.5 4.0 3.0 4.0 4.0 2.5
$.?
3.0
5.0 4.5 5.0 4.0 4.5 4.5 3.0 4.0 3.5 6.5 3.5 5.5 4.0
...
5.0
...
... ...
4.0 5.0 4.5 2.5 6.5
i CI 4 .0 4.6 4.0 4.0
!;! 6.. 0 5.5 5.5 3.0 4.0 3.0 4.5 4.6 3.0 7.0
Bleedinga
-Potential Ca.4 C13
P e r cent
7
0.0 0.0 0.0 0.0 1.8 0.0 0.0 0.0 0.0 0.0 0.0 3.0 0.0 0.0 1.0 0.0 0.0 0.7
CompositionC?S C A F CaSOr
22.5 12.5 19.5 18.7 16.2 33.5
13.1 8.5 12.0 12.4 9.0 8.2 12.1 10.8 8.8 8.9 10.9 10.9 9.1 10.5 8.1 8.0 6.4 6.8 7.0 12.2 9.5 11.1 10.7 10.0 9.5 9.5 9.6 6.9
3.0 3.7 4.1 4.4 4.6 4.2 4.7 4.0 3.7 3.7 2.7 3.7 3.6 2.7 3.7 3.4 3.5 3.7 5.4 4.2 3.6 4.0 4.0 2.9 3.9 3.7 3.7 3.8
25.8 23.8 26.8 20.5 12.4 21.7 20.1 32.0 18.5 21.0 17.8 14.8 17.2 23.6
8.6 8.6 12.7 10.8 10.8 8.5 9.0 15.1 11.8 9.2 9.0 9.2 7.3 11.6
3.1 3.7 2.7 4.0 3.3 2.8 3.2 2.7 2.8 2.9 3.2 3.5 3.7 3.0
5 7 10.1 12,s 8.7 8.8 13.1 4.1 12.7 10.1 10.7 13.4 14.9 11.5 11.0 12.6 10.5
51.2 47.f 46.7 48.7 56.5 53.8 62.5 48.1 60.5 46.2 56.9 57.6 55.4 45.0 47.2 46.5
23.8 24.0 26.3 18.4 16.7 15.3 13.4 20.5 11.4 24.5 11.3 16.7 18.2 28.0 30.7 20.1
11 6 10.7 11.9 10.1 9.7 15.4
47.4 60.4 56.3 53.0 56.8 37.1
11 6
45.9 47.8 50.1 48.1 60.4 52.8 48.2 38.6 55.0 54.0 50.4 54.5 51.4 52.0
0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.0 0.7 0.5 0.3 0.0 3.0 0 0 0.0 0.3 0.0 1.0 2.1 0.0 0.0 0.0 0.0 6.7 0.0 0.0 1.5 0.8 0.0 6.7
10 2 6.3 12.7 7.2 10.6 13.0 8.6 8.2 9.5 16.4 12.7 15.0 6.4
SO,
-
1.5 2.2 "4 2.6 2.7 7.5 2.8
2.6 2.-
2 2 1.6
2''
2.1 1 6 2'' 2.0 2.1 2 2 3.2 2.5 2.1 2.3 2.3 2.4
2.3 2 2 .> 2 2 2
1.8 2 " 1.6 2.4 1 9 1.7 1.6 1. 6.
:.:
1.6 2 1
- . -.> .)
1.8
Concrete mixes, all identically graded Scituate sand and gravel, 1 t o 6 b y weight; nater-cement ratio (by volume), 0.80; bleeding a6 meaaured by Brou II water-cement ratio of 1.00.
$11 a t
INDUSTKIIL AND ENGINEERING CHEMISTRY
AUGUST, 1936
963
SURFACE AREAS DETERMINED E Y WAGNER METHOD
-n I
7000
la -
6000
w E
4000
rn w
> cn m
5000
3000 2000 S.A
MIX X SLUMP UNTRIATLD
2
IOoo
-
S.A. MIX % SLUUP 1600 1.5.;.7C 2.1
S.A. MIX X SLUMP UNTREATED I600 1-6.
S.A. MIX "h SLUMP
S A . MIX X SLUMP
4
7000 6000
0 0
5000 4000 3000 2000 1000
lDAY
3D.
28D.
6MO.lYFi 2 Y R .
30.
ZED.
6MO.IYR.ZYR.
3D.
280.
30,
6MO.IYR.2YR.
280. 6MO.IYR.ZYR.
30.
3
5
28D.
6MO. I Y R . 2 Y R .
AGE previously described effects can be used by the ilianufact urers of cement and concrete is outside t'he scope of this paper, it, is essential to recognize that the use of a cat,alptic and dispersing agent from the manufacturing point of \*iew is of special value in two situat'ions. In the first place, without recourse bo double burning or other expensive additional operations, it permits the manufacture of high early-strength cements by fine grinding of niost standard clinkers containing 45 per cent or more of tricalcium silicate. I n the second place, TT-hen a cement which passes all of the specifications for high early-strength cement is not required, a catalytic and dispersing agent may be used to make cements of exceptional a-orbability and very low bleeding tendency which hare many of the advantages of standard high early-strength cements. Since TDA is now being used in approximately 100,000 barrels of ceiiient per rnonth and has already been used in over 1,500,000 barrels, the best way to measure the extent to which it is of value is t.o analyze data collected (luring the testing of commercial TD.1 cements ground a t n-idely scattered mills. The follon-ing mill tests are reported, and, unless otherwise noted, these inill data represent rwis of ilom 2000 to 50,000 barrels at a time.
Strength a t All Ages High early strength is a desirable characteristic for all types of concrete. The niore completely a concrete cures during the time the mixing water is present, the stronger and inore durable it hecomes. On many johs thig period is limited t o the tirile necessary to empirate the iiiixiiig water. This i n all too h i r t in hot n-eather xiid dry climates. Cell-~entsv-ith
I
2
4
6
7
SAMPLE NUMBER
FIGL-RE 4. DURABILITY DAT~
high early-qtreiigtli characteristics cure iiiucli further during this limited time than do norinal cements. Furthermore, xvhere concrete is kept moist, it should continue to develop strength over long periods, and the ideal is realized n hen the early strengths increa>e constantly nith continued curing.
INDUSTRIAL AND EKGINEERING CHEMISTRY
966
VOL. 28, NO. 8
sive strengths of the treated high early-strength cements are in every case higher than those of the untreated. Kagner -Tensile Strength- -Compressive StrengthBleedComparing the treated and untreated normal Surface llrea 1-day 3-day 28-dag 1-day 3-day 28-day Slump ing Sq. cm./oram Pounds p e r square m c h cements, the strengths are again in favor of the treated cements. I n this case, however, the Commercial High Early-Strength Cements Untreated 2510 315 424 488 1740 3435 5285 3.5 average surface area of the treated cements was Av. Min 2260 170 350 450 670 2835 4480 2 o oo nearly 300 sq. cm. per gram higher than that of Max 2700 385 470 510 "O0 3890 5925 the untreated cements. This increase in surface Treated. Av. 2500 340 425 495 1790 3490 5425 4 5 0 3 area may be attributed to the presence of the Min. 2100 285 390 440 1230 2525 4515 2 5 0 0 Max. 2910 415 465 545 2405 4375 6395 6 5 18 TDA, which acts as an efficient grinding aid and Commercial Normal Cements permits of the production of a cement with a Untreated. 1630 160 285 420 635 1865 3710 higher surface area a t the same mill output. Av. Min. 1250 50 185 345 375 1315 2635 15 0 0 C o n s e q u e n t l y , only part of the increase in Max. 2120 230 345 515 990 2740 2840 7 1 22 0 strengths obtained is due to the presence of the Treated .4 >fin v 1530 l8'' :$! catalyst; the remainder is due to this increase in Max 2190 305 370 502 1850 3710 5545 7 0 6 i surface area. Figure 3 shows that the development of compressive strength over extended moist curing Table I shows data for typical high early-strength and norperiods for various treated cements is comparable to that of mal cements treated by adding TDA to the clinker before untreated cements made from the same clinkers. It also grinding. These were made a t various times since August, s h o w that the early-strength advantages realized by the 1933, a t thirty different plants, widely scattered oaer the combined effect of finer grinding and presence of catalyst are country. All tensile data have been made in accordance maintained. with A. S. T. M. standard procedure. ,411 compression Table I11 shows typical mill data from five different plants data were obtained using well-graded sound aggregate and, in the East and in various parts of the Midwest, which are unless otherwise noted, with a water-cement ratio of 0.80 by using TDA in their manufacturing procedure. I n every case volume. the 1- and 3-day tensile strengths are uniformly high and The tensile strengths of the high early-strength cements greatly in excess of the A S. T. 11.high early-strength tentashow that the use of a catalyst permits the manufacture of tive specification requirements, in spite of the xide variation high early-strength cements from widely varying raw main the average composition and fineness of the cements from the different plants. terials, plant locations, and potential compositions. It is interesting to note that, with the same mix and water Durability ratio, eight commercial untreated high early-strength ceDurability is perhaps the most desirable property of conments and twenty-two untreated normal Portland cements tested under identical conditions gave the results shown in Crete. Freezing and thawing tests are being more and more accepted as an accelerated means of duplicating the neatherTable 11. For convenience this table also reproduces the ing conditions to which concrete is subjected in the field. averages shown in Table I. Though the average surface areas of the treated and untreated high early-strength ceIf a concrete is not homogeneous, continued freezing and thawing inevitably cause its disintegration. If voids due ments are about the same, the average tensile and conipresTABLE11.
C O M P 4 R I S O N O F RESULTSON T R E 4 T E D .4ND TREdTED CEMESTS
EN-
I
iii ii:
gi!
FIGURE 5.
E
COMPARATIVE
BLEEDISGD.4T.4
AUGUST, 1936
INDUSTRIAL AKD EXGINEERING CHEMISTRY
t o water gain under the aggregate are present, water fills these channels during the thawing cycles and, upon freezing, causes strains which hasten disintegration. Figure 4 compares graphically the resistance to freezing and thawing of several typical concretes made with TDA cements and of those made with normal cements of identical or less fineness from the same clinkers. These data are presented
967
I FI GURE 6. BILITY
I
uwrwmv 7DCLIC”
100 ,n
I I
2100
34
. , A *
PERMEADATA
C C. OF WATER THROUGH;
TABLE111. TYPICAL MILL D A T . ~ TVagner Surface Setting Time Area Initial Final Date. 1936” Sq.
cm./
Lb.p e r
gram
Plant 22 (Midwest). CsS 56.6%. CIS le.;%; C d , 9.71 C A F , 9.6; CaSO1, 3.7;SOa, 2 . 2 %
P l a n t 17 (Lehigh Valley). CaS, 59.5%; c 4 9.4. C2S 10.2. d k f , li2; dasor: 4.2; SOa, 2.4%
1/16 D 1/15 D 1/15 D 1/15 D 1/14 D 1/14 D 1/14 D 1/14 D 1/14 D 1/14 D 1/14 D 1/15 D Average Minimum Maximum
2475 2475 2520 2570 2585 2520 2410 2470 2500 2450 2580 2450 2500 2410 2585
2:lO 2:15 2:15 2:15 2:lO 2:lO 2:lO 2:lO 2:20 2:20 2:20 2:lO
4:40 4:40 4:40 4:25 4:20 4:35 4:35 4:35 4:15 4:20 4:20 4:25
.. ..
.. ..
1/16 D 1/13 D 1/14 D 1/14 D 1/15 D 1/16 D 1/16 D 1/16 D 1/17 D Average Rlinimuni A1axi mu m
2650 3900 2800 2705 2800 2840 2750 2780 2790 2780 2650 2900
3:OO 3:40 3:OO 3:45 3:25 3:20 3:OO 2:lO 3:lO
4:45 6:lO 6:15
1:45 1:45
3:45 3:30
1:45 2:OO 1:45 1:45 1:45 1:45
3:15 3:30 3:45 3:30 3:30 3:30
Average Minimum hlaximum
2425 2403 2587 2704 2780 2630 2699 2760 2751 2572 2660 2515 2624 2403 2780
3/4 D 3/4 D 4/4 D 3/4 D 3/5 D 3/5 D 3/5 D 3/10 D 3/11 D Ax-erage Minimum hfasimum
2890 2880 2850 2820 2780 2850 2720 2780 2830 2820 2720 2890
4/29 D 4/30 D 4/30 N 5/l D 5/1 S 5/2 D 5/2 N 5/3 D 5/3 N
2860 2808 2808 2948 2948 3051 3051 2895 2895 2844 2844 2889 2889 2950 2950 2941 2941 2944 2944 2966 2966 2900 2900 2910 2808 3051
P l a n t 4 (Midwest). Cas, 47.5%; CtS, 22.5’CIA 1 1 1. c a ~ O 4 4.6; , &h, 10.7; Sos, 2.3%
Plant 18 (Midwest). (239, 56.7%; Ca4, 13.4; CxS, 14.4: CIAF. 9.5: CaSOa, 3.6; 803, 2.1%
Plant 19 ( M i d n e s t ) , cas 570%. CxS, 14.0’.c h io.0. CaSO4, 4.6;CIAF, 11.1%; So3, 2.3%
s:; : 5/5 D
5/5
s
5/6 D 5/6 S 5/7 D 5/7 9 5/8 D 5/8 s 5/9 D 5/9 s 5/10 D 5/10 s Arerage Minimum Maximum a
D = d a y ; S = night.
Tensile Strength I-day 3-day
..
.. .. ..
.. .. ..
2:lO 2:15 2:50
2:30 2:45 2:40 3:55 3:20 3:35 *.
.. ..
..
5:50
6:OO 5:40 4:50 4:lO 5:05
.. .. ..
..
.. .. 4:50 5:OO 5:35 5:30 6:OO
5:OO 7:OO 6:30 6:35
..
.. ..
1:40 1:30 1:30 1:30 1:lO 1:30 1:30 1:25 1:30 1:30 1:30 1:20
2:30 2:30 2:40 2:40 2:50 2:50 2335
1:3O 1:30 1:30 1:45 1345
3:OO 2:45 2:45 3:OO 3:OO
..
..* .
3:OO 2:30 2:30 2:30 2:oo
.. ..
..
336 343 362 374 404 384 310 370 371 321 320 346 353 310 404
in. 413 430 426 450 452 425 402 436 406 396 409 445 424 396 452
sq.
325 410 440 440 357 402 3.52 422 .~~ ~~355 445 339 430 325 404 359 445 358 448 345 , 427 325 402 359 448 323 340 375 375 372 363 380 380 377 385 385 342 368 323 385
423 437 447 457 467 467 468 468 452 44s 460 417 454 417 468
390 340 380 390 335 37.5 365 378 350 367 335 390
475 470 490 440 445 4717 495 455 455 466 440 495
370 345 325 303 337 327 353 342 343 343 345 353 325 375 350 342 367 372 400 393 367 400 408
462 428 447 422 428 425 430 425 433 408 440 425 447 463 460 432 437 457 492 473 463 482 470 447 408 49‘7
,356
303 408
SAMPLE NUMBER with full appreciation of the fact that they are far from complete and in the expectation that a future paper will deal exhaustively with this property and its relation to bleeding. However, preliminary work carried on by several independent laboratories shows definitely that concretes made with TD-4 cements are much more resistant to freezing and thawing than are concretes made with corresponding untreated cements ground to the same or lesser fineness.
Workability There is probably more controversy over the measurement of “Workability” of concrete than over that of any other characteristic of concrete. Several methods of testing workability have been devised, but unfortunately results obtained from these different methods frequently fail to check each other in actual practice. Consequently, as is generally admitted, no satisfactory and accurate method of measuring workability of concrete is yet available. Much research is now under way, and it is hoped that a satisfactory test procedure will shortly ’be developed and that a separate paper devoted exclusively to this subject can be presented in the near future. hlthough physical measurements are not available because of the above-mentioned situation, those who have used TDA-treated cements in the field (whether ground very fine to pass high early-strength specifications or ground less fine) agree that they are very workable.
Negligible Bleeding The cause of “bleeding,” a detrimental characteristic of concrete only recently fully appreciated, is today the subject of much discussion. Throughout this paper the term “bleeding” is used to designate the phenomenon of separation of
968
I\ DLSTliI 4 L .4\D E\ GI\EEHI\G
CH E\lISTHl
VOL. 2 8 . 3 0 . 0
water from the cement paate before the cement i. hard. Brown ( 1 ) ha. puhlished a full discu-1011 of the subject. Bleeding. a. discil-et1 quantitatively here, refers only to this characteristic of cement itself. It is reflected in the bleeding of the resulting concrete. Up to a certain point the bleeding tendency of a cement is usually reduced by increasing the fineness, hut in many cases, after coiiiniercial finenew is obtained, bleeding is still excessive. Excessive bleeding results in three objectioiiable characteristics of concrete: (a) the formation of voids under the aggregate, sometimes called "water gain" under the aggregate; ( b ) nonhomogeneous concrete, due to the difference in density between the top and bottom of a section of concrete cau+ed by the rise of water towards the surface; arid (c) excessive laitance. The beneficial effect of TDA is especially notable d h cenieiits of high bleeding characterktic.. Figure 5 contrasts graphically the bleetliiig characteristics of various cement paPtes made with ten typical treated and untreated but otherwise identical cements. However, in studying these data it is to be remembered that there are a few norinal untreated cements and a larger number of untreated high early-strength cement: which chow negligible bleeding characteriqtics.
Permeability to Passage of Corrosive and Pure Waters Methods of quantitati7-ely measuring water percolation through concrete are not fully developed, but progress in this direction is being made. There is already evidence that permeability t o transverse flow is greatest n here high bleeding tendencies have accentuated IT nter-gain layers under the aggregate. Figure 6 conipares graphically the relative permeability of Seven typical treated cement and the corresponding untreated normal cements. The method used to obtain these results was to pour 2 X 4 inch porous mortar cylinders, haying a mix of 1 to 5 by weight, around the ends of 0.5-inch steel tube3 10 inches in length. After hardening, these porous cylinders were cast inside of 8 X 12 inch concrete cylinders. After curing for 28 days, water a t a pressure of 50 or 100 pounds per square inch mas forced into the projecting tubes. The permeability of the concrete specimens was measured by the amount of water forced into the cylinders. This method is as yet far from completely satisfactory; many cylinders are prone to ' 0 niuch leakage along the tubes that the data froni such tests must be discarded. However, the data shown here are from only such tests as were free from such leakage, and in each of them the concretes iiiade with treated cement.. n ere much less permeable than those made xith the corresponding untreated cements.
Warehousing Qualities K h e n qtoretl in m-arehouses in bag
