WEBB P (US)
| US3860433A | 1975-01-14 | |||
| US3973978A | 1976-08-10 | |||
| US4058407A | 1977-11-15 |
| 1. | A hudraulic cement composition comprising from about 3.75% to about 40% of 3CaO.3A10 .CaSO , from about 0.1% to about 5% of lime, from about 3% to about 35% of calcium sulfate, dicalcium silicate, from about 0.1% to about 2% of a hydroxy polycarboxylic acid, and from about 0.25% to about 4% of sucrose, said amounts being based upon the total dry weight of said compo¬ sition. |
| 2. | The composition of Claim 1 wherein the acid is citric acid. |
| 3. | The composition of Claim 2 wherein the amount of citric acid is from about 0.25% to about 1%, the amount of sucrose is from about 0.25% to about 4%, and the sucrose to acid ratio is from about 1:1 to about 6:1. |
| 4. | The composition of Claim 2 wherein the amount of the citric acid is abo 0.5% and the ratio of sucrose to acid is from about 1:1 to about 8:1. |
| 5. | The composition of Claim 2 wherein the amount of citric acid is from abo 0.1% to about 0.25% and the amount of sucrose is from about 0.25% to about 0. |
| 6. | The composition of Claim 2 wherein the amount of citric acid is about 1% and the amount of sucrose is from about 1% to about 3%. |
| 7. | The composition of Claim 4 wherein the amount of citric acid is about 0. and the sucrose to citric acid ratio is from about 1:1 to about 6:1. |
| 8. | The composition of Claim 2 wherein the amount of citric acid is about 1% and the amount of sucrose is about 4%. |
| 9. | The composition of Claim 2 wherein the amount of citric acid is about 2% and the amount of sucrose is about 2%. |
| 10. | The composition of Claim 2 wherein the amount of citric acid is about 2% and the amount of sucrose is about 4%. |
| 11. | A method for preparing a cement composition comprising mixing from about 375% to about 40%, based on the total dry weight of the composition, of 3CaO3Al„0_,.CaSOy, with from about 0.1% to about 5% of lime, from about 3% to 2 3 4 about 35% of calcium sulfate, from about 0.1% to about 2% of a,hydroxy poly¬ carboxylic acid, from about 0.25% to about 4% of sucrose, and dicalcium sili¬ cate as the substantial remainder. |
| 12. | The method of Claim 11 wherein said acid is citric acid. |
| 13. | A method for retarding the setting of a cement composition comprising fr about 4% to about 40% of the ternary compound 3C.aO.3A10 .CaSO , from about 0 to about 5% of lime, from about 3% to about 35% of calcium sulfate and dicalc silicate as the substantial remainder, said method comprising the addition to said cement of the combination of admixtures consisting of from about 0.25% t about 1% of citric acid and from about 0.25% to about 4% sucrose, based on the total dry weight of said cement and said admixtures, in which combination the ratio of sucrose to acid is from about 1;1 to about 6:1. |
| 14. | A method for reducing the demand for water in the formation of easily placeable cement/water mixes from a cement comprising from about 5% to about 40% of the ternary compound 3CaO.3A1 0 .CaSO , from about 0.1% to about 5% of lime, from about 3% to about 35% of calcium sulfate, and dicalcium silicate as the substantial remainder, said method comprising the addition to said cement of a combination of admixtures consisting of about 0.5% citric acid and from about 0.5% to about 4% sucrose, based on the total dry weight of said ce¬ ment and said admixtures. |
| 15. | A method of reducing the demand for water in the formation of easily place able cement/water mixes from a cement comprising from about 4% to about 40% of the ternary compound 3CaO.3Al O_.CaSO , from about 0.1% to about 5% of lime, and about 3% to about 35% of calcium sulfate and dicalcium silicate as the substantial remainder, said method comprising the addition to said cement of a combination of admixtures consisting of about 1% citric acid and from about 2% to about 4% sucrose, based on the total dry weight of said cement and said admixtures. |
| 16. | A method for reducing the demand for water in the formation of easily placeable cement/water mixes from a cement comprising from about 4% to about 40% of the ternary compound 3CaO.3A10 .CaSO., from about 0.1% to about 5% of lime, from about 3% to about 35% of calcium sulfate, and dicalcium silicate as the substantial remainder, said method comprising the addition to said cement of a combination of admixtures consisting of about 2% of citric acid and 2% of sucrose, based on the total dry weight of said cement and said admixtures. |
| 17. | A method for increasing the compressive strength, upon full or partial hydration, of a hydraulic cement comprising from about 4% to about 40% of 3Ca0.3Al 0 .CaSO , from about 0.1% to about 5% of lime, from about 3% to about 35% of calcium sulfate, and dicalcium silicate as the substantial remainder, said method comprising the addition to said cement of a combina¬ tion of admixtures consisting of about 1% citric acid and from about 1% to about 3% sucrose, based on the total dry weight of said cement and said ad¬ mixtures. |
| 18. | A mortar comprising the hydraulic cement composition of Claim 1 or Claim 2. OIΛPI />, WIPO » . |
| 19. | A concrete prepared from the composition of Claim 1 or Claim 2. |
| 20. | A grout comprising the hydraulic cement composition of Claim 1 or Claim 2. |
This invention relates to high aluminate cements which produce upon hy- dration a substantial amount of tricalcium aluminosulfate hydrates. It par¬ ticularly relates to cement compositions of this type which contains a syner- gistic combination of a saccharide and a hydroxy polycarboxylic acid. Fur¬ ther, it relates to high aluminate cements which may be handled and transported for a longer period of time before setting than is usual with such cemen * cs. More particularly, it relates to cements containing the ternary compound. 3 CaO » 3A1 O •CaSO , hereinafter referred to as CSA.
The economy and versatility of Portland cements, along with their high ultimate strengths, have made them pre-eminent among hydraulic cements despite their practical limitations of being slow to set and slow to develop the strength necessary to be self-supporting. The development of Type III Portland cement was an early response to the need for a faster. setting, early strength cement. Calcium halo-aluminates have been incorporated into Portland cement compositions to achieve shortened but controllable setting times. Mixtures of a halo-aluminate cement and a calcium sulfate anhydrite have been offered as early strength cements. Cement mortars containing CSA, calcium sulfate and dicalcium silicate set quickly and develop compressive strengths of about 2900 psi and higher within 24 hours after mixing with water.
The setting times for many of these early strength cements however, is too fast - not enough time is allowed for mixing, transporting, and proper placing. This problem was addressed by Nakagawa et al in U.S. Patent No., 3,973,978. The solution proposed therein was to prepare two separate mixtures - a Portland cement paste and a quick hardening agent - and then mixing the two at the job site. The need for special equipment such as a Y-tube, metering apparatus and an additional mixer is apparent from the description of the patented method.
The quick hardening agent of Nakagawa et al optionally contains a serting retarder and/or a quick hardening accelerator. The setting retarders listed are the organic carboxylic acids conventionally used, such as gluconic, tar- taric salicylic, citric, and malic acid. The hydroxides and carbonates of alkaline earth metals and alkali metals are described as quick hardening accel ators.
In U.S. Patent No. 3,860, 433, Ost et al teach that very high early stren cements containing CSA, calcium sulfate and dicalcium silicate usually can be produced to have an initial set in about 20 minutes but that conventional re¬ tarders such as sucrose, boric acid, and mucic acid (i.e. tetrahydroxyadipic acid) may be added.
A water-repelling and set-retarding admixture for incorporation in Portla cements and other hydraulic cements is taught by Serafin et al in U.S. Patent No. 3,885, 985. Serafin et al teach the use of many various materials and mix tures thereof as set-retarding agents. Included among these are polyhydroxy polycarboxylic compounds and saccharides such as glucose, fructose, lactose, sucrose, starch and cellulose.
According to U.S. Patent No. 4,058,407, combinations of admixtures are frequently used in hydraulic cements to achieve certain results or overcome inefficiencies, such as where an admixture does not produce a sufficient im¬ provement in the compressive strength or does not effect the desired degree of retardation. Several admixtures, such as lignosulfonates, salts of hydroxycarboxylic acids, sugars and polysaccharides are listed as having the multiple effects of water reduction, set retardation and compressive strength improvement.
Now, it has been discovered, however, that sucrose accelerates the settin of the very high early strength cements containing CSA taught by Ost et al. It also has been discovered that a combination of sucrose and a hydroxypoly- carboylic acid reverses the effect of the sucrose and that the setting time is longer, than would have been expected from a consideration of the sum of the individual effects. In further contrast to the teachings of the prior art, the hypothetical cumulative effect of the sucrose/hydroxy polycarboxylic acid combination would be a lower compressive strength of the cement than that of the cement with neither admixture whereas the observed effect of the com¬ bination is a greater compressive strength. Finally, the sucrose/acid com¬ bination synergises the water-reducing effect of each agent.
It is an object of this invention, therefore, to provide a hydraulic cement composition having a high early strength when hydrated but whose
initial setting time is retarded sufficiently to allow proper placing after mixing it with water and transporting the mixture to a job site.
It is another object of this invention to provide such a cement compo¬ sition having a compressive strength which is synergistically increased by a combination of admixtures whose hypothetical cumulative effect would be to decrease the compressive strength.
It is a further object of this invention to provide a cement composi¬ tion which is very fluid and essentially self-leveling without sacrificing strength.
These and other objects which will become apparent from the following disclosure are achieved by a cement composition which comprises, on a dry weight basis, from about 3.75% to about 40% of CSA, from about 0.1% to about 2% of a hydroxy polycarboxylic acid, from about 0.25% to about 4% of sucrose, from about 0.1% to about 5% of lime, from about 3% to about- 35% of calcium sulfate, and dicalcium silicate to make up the substantial remainder.
The dicalcium silicate generally is present in amounts ranging from about 20% to about 90% of the total dry weight of the composition.
A preferred composition comprises from about 10% to about 30% of CSA. Par¬ ticularly preferred is a composition comprising from about 15% to about 25% CSA.
The hydroxy polycarboxylic acid contemplated in the invention is exempli¬ fied by citric acid, tartaric acid, malic and mucic acid. It contains up to about 6 carbon atoms and up to about 4 hydroxyl groups. Citric acid is pre¬ ferred. The admixtures may be used in their solid forms but also as aqueous solutions. Dilute aqueous solutions of the admixtures may be used as all or part of the mix water when the cement is used to make a paste, grout, mortar or concrete.
It is evident that the introduction of the acid into a system containing basic calcium will result in the in situ formation of the calcium salt. There¬ fore, other soluble sources of the carboxylate ion are contemplated as an ad¬ mixture in this invention.
The setting of the cement compositions is retarded by the presence of from about 0.25% to about 1% of the hydroxy polycarboxylic acid .and from about 0.25% to about 4% of sucrose when the weight ratio of sucrose to the acid is from about 1:1 to about 6:1. Among the preferred compositions having a retarded set are those comprising about 0.25% citric acid and from about 0.25% to about 0.5% sucrose, those comprising about 0.5% citric acid and from about 0.5% to about 3% sucrose, those comprising about 1% citric acid and from about 1% to
about 2% sucrose, and those comprising about 1% citric acid and about 4% sucrose.
The water reducing effect of the sucrose/hydroxy polycarboxylic acid combination is greater than the sum of the individual effects at three differ¬ ent levels of concentration: (1) at about 0.5% of the acid and a sucrose/acid ratio of from about 1:1 to about 8:1; (2) at about 1% of the acid and a sucros acid ratio of from about 2:1 to about 4:1; and (3) at about 2% each of the aci and sucrose. A composition containing about 0.5% of citric acid is preferred.
The early and the ultimate compressive strengths of a hydrated cement com position of this invention are increased by the presence of from about 0.1% to about 2% of the hydroxy polycarboxylic acid and from about 0.25% to about 4% of sucrose regardless of the ratio of one to the other. Preferred for this pu pose are compositions comprising from about 0.1% to about 0.25% citric acid an from about 0.25% to about 0.5% sucrose, compositions comprising about 0.5% cit acid and from about 0.5% to about 4% sucrose, and compositions comprising abou 1% citric acid and from about 1% to about 3% 'sucrose. Especially preferred ar compositions comprising from about 0.1% to about 0.25% citric and from about 0.25% to about 0.5% sucrose.
The composition contemplated in the invention includes the dry cement com position, neat pastes thereof, grouts, mortars, and concrete mixes. The addit of the admixture may be made, according to whether the admixture is in its sol form or in solution, at the time of preparing the dry- cement or when the com¬ position is mixed with water at a mixing plant or at the job site.
The following specific examples illustrate further the method and com¬ position of this invention. All concentrations stated herein are in terms of percentage based upon the total weight of the dry cement composition unless otherwise indicated.
EXAMPLE 1 Water Demand Reduction
Sand and cement at a ratio of 2.75 to 1 are charged to a mixer. The cal¬ culated compound composition of the cement is 18.9% CSA., 22.2% calcium sulfate, 46% dicalcium silicate and 1.6% tetracalcium aluminoferrite, and 4.4% lime. I oxide analysis is as follows: 53.1% CaO, 9.8% Al O , 0.5% Fe 0 , 16.1% SiO , 15.6% SO , 0.7% Na 0 and minor amounts of the oxides of magnesium, titanium an potassium. Granular sucrose is added and the dry materials are mixed for two minutes before the mix water and an aqueous solution of citric acid are added. Mixing is continued for three minutes.
- REAC OMPI
The flow is measured 4 minutes after the addition of water. Because the water/cement ratio (W/C) varies from one mortar to another and the flow is roughly proportional to that ratio, the effect of the admixtures is deter¬ mined by comparing the "fluidity factor" (4 minute flow value -~ W/C) of the treated mortars with that of the control (i.e., containing neither admixture).
The percentage of citric acid and sucrose, the W/C, and the test re¬ sults are given in Table I.
EXAMPLE 2 Set Retarding Effect
The time of initial set of the mortars described in Example 1 is determined by placing a Gillmore initial set needle on a set pat of the mortar and noting the time, measured from the addition of water, at which the needle fails to leave a mark on the surface of the pat. The test results are given in Table II.
For testing purposes it is desirable to have a 4 minute flow value of about 110. To achieve that goal the water/cement ratio is varied. It is generally accepted that the compressive strength of a hydrated cement composition is roughly inversely proportional to the water/cement ratio. To compensate for the differing water/cement ratios used, therefore, the observed compressive strength values shown in Tables III and IV are adjusted to indicate what the strengths would be at constant ratios of 0.623 and 0.56, the ratios used in the respective control compositions.
It is recognized that the relation of compressive strength to the water/ cement ratio is not fully linear but the adjusted strength values do indicate the relative ability of an admixture to affect the strength development of the cement composition. The large differences between the adjusted values for the combination and those for the hypothetical cumulative effect shewn in Tables III and IV are greater than the divergence from linearity.
EXAMPLE 3 Effect on Compressive Strength
Each mortar of Example 1 is cast into two-inch cubes and the cubes are cured while in the mold under a moist atmosphere for 3 hours, at which time they are stripped from the molds. The compressive strength of one cube from each mortar is determined 24 hours after the addition of the mix warer. Curing of the re¬ maining cubes is continued under water for 182 days, at which time the compres¬ sive strengths are deteπnir.ed again. The amounts of each admixture and the water/cement ratio for each mortar is indicated in Table III.
% Flow Fluidity Difference (x - A ) Actual emula ive
Citric Acι= Sucrose W/C (4 πin. ) Factor
0 0.623 10S.7 174 .5
+10
0.5 0 0.547 100.9 134.5
0.5 0.577 104.1 180.4 + 5.9 +15.9
0
0.533 104.2 195.5 +21.0 0.5 0.5
100.9 184. Ξ + 10.0
Q.5 0 0.547
1 0.550 100.3 179.1 + 4.6 +14.6
0 +39.6 0.5 1 0.517 110.7 214.1
0.547 100.9 134.5 +10
0.5 0 .541 90.3 166.9 - 7.6 + 2.4
0 2.00 0 +27.4 0.5 2.00 0.4B1 97.1 201.9 ■
0 0.547 100.9 184.5 +10.0
0.5 +30.2
3.00 0.552 107.5 194.7 +20.2
0
115. S 235.8 +61-3 0.5 3.00 0.491
134.5 +10.0
0.5 0 0.547 100.9
4.00 0.540 103.8 192.2 +17.7 .21.1
C
0.473 100.9 213.3 +38.8 0.5 4.00
+30.1
1 0 0.561 114.8 204.6
0.5 0.577 104.1 130.4 + 5.9 0
0.505 9S« 4 194.8 +20.3
1 0.5
0 0.577 126.6 219.4 +44.9 + 5.9 +50. ε
C 0.5 0.577 104.1 130.4
0.5 0.509 95.8 188.2 +13.7 s
0 0.561 114.8 204.6 +30.1
1 0.560 100. 3 179.1 + 4.6 + 34.7
0 1 1 0.491 95.5 194.5 +20
1.0 0 0.561 114.8 204.6 +30.1
0 2.0 0.541 90.3 166.9 - 7.6 +22.5 1.0 2.0 0.493 110.5 224.1 +49.6
1.0 0 0.561 114.8 204.6 +30.1
0 3.0 0.552 106.5 194.7 +20.2 +50.3 1.0 3.0 0.467 110.6 236.8 +62.3
1.0 0 0.561 114.8 204.6 +30.1
0 4.0 0.540 103.8 192.2 +17.7 +47.8 1.0 4.0 0.483 120.1 248.6 +74.1
2.0 0 0.577 126.6 219.4 +44.9
0 1.0 0.560 100.3 179.1 + 4.6 +49.5 2.0 1.0 0.541 116.1 214.6 + 40.1
R 2.0 0 0.577 126.6 219.4 +44.9 G 0 2.0 0.541 90.3 166.9 - 7.6 +37.3 y 2.0 0.519 116.8 225.0 +50.5
O I
-7-
TABI.E II
% Initial Set Ci ric Difference (x - A) Mortar Acid W/C Actual Cumulative
0.623 29
B 0.5 0 0.547 34 + 5
C 0 0.5 0.577 24 - 5
D 0.5 0.5 0.533 38 + 9
B 0.5 0 0.547 34 + 5 - 2
E 0 1 0.560 22 - 7
F 0.5 1 0.517 36 + 7
B 0.5 0 0.547 34 + 5 - 4
G 0 2 0.541 20 - 9
H 0.5 2 0.481 34 + 5
B 0.5 0 0.547 34 + 5 - 2
J 0 3 0.552 22 - 7
K 0.5 3 0.491 39 +10
B 0.5 0 0.547 34 + 5
L 0 4 0.540 28 - 1
M 0.5 4 0.473 32 + 3
N 1 0 0.561 52 +23 +18
C 0 0.5 0.577 24 - 5
P 1 0.5 0.505 48 +19
R 2 0 0.577 77 +48 +43 c 0 0.5 0.577 24 - 5 ε 2 0.5 0.509 51 +22
N 1 0 0.561 52 +23 +16
E 0 1 0.560 22 - 7
T 1 1 0.491 51 +22
N 1 0 0.561 52 +23
G 0 2 0.541 20 - 9
U* 1 2 0.493 68 +39
N 1 0 0.561 52 +23 +16
J 0 3 0.552 22 - 7
V* 1 3 0.467 44 +15
N 1 0 0.561 52 +23 +22
L 0 4 0.540 28 - 1
W* 1 4 0.4H3 70 +41
B 0.5 0 0.547 34 + 5 ε 0 1 0.560 22 - 7
FF 0.5 1 0.493 21 - 8
N 1 0.561 52 +23 +14
G 0 0.541 20 - 9 uu* 1 0.493 36 + 7
T ixotropic »
NOTE: Sucrose added as a solution in samples FF and UU.
TABLE III COMPRΞSSIVE STRENGTH ( PΞI )
Cirric % 24 Hr . Difference (x - A) 182 Day Difference (x
Mortar Acid Sucrose W/C 24 Hr. at W/C=0. 623 Actual Cumulative 182 dav at W/C=0. 623 Actual Cuπula 0. 623 3845 3845 5781 5781
B 0.5 0 0.547 3950 3468 - 377 -1105 5819 5109 - 672 5
C 0 0.5 0. 577 3365 3117 - 728 6325 5858 + 77
D 0.5 0.5 0.533 4800 4106 + 261 7038 6021 + 240
B 0.5 0 0.547 3950 3468 - 377 -1251 5819 5109 - 672 -12
E 0 1.0 0. 560 3305 2971 - 874 5762 5179 - 602
F 0.5 1. 0 0.517 4865 4037 + 192 7825 6494 + 713
B 0.5 0 0.547 3950 3468 - 377 -1174 5819 5109 - 672 -10
G 0 2.0 0.541 3510 3048 - 797 6245 5423 - 358
H 0.5 2.0 0.481 5685 4389 + 544 8475 6543 + 762
3 0.5 0 0.547 3950 3468 - 377 -1537 5819 5109 - 672 -14
J 0 3.0 0.552 3030 2685 -1160 5700 5050 - 731
K 0.5 3.0 0.491 5168 4073 + 228 7519 ' 5926 + 145
B 0.5 0 0. 547 3950 3468 - 377 -1418 5819 5109 - 672 -16
L 0 4.0 0. 540 3235 2804 -1041 5512 4778 -1003
H 0.5 4.0 0.473 5623 4269 + 424 8112 6159 + 378
C 0 0.5 0. 577 3365 3117 - 728 -1048 6325 5858 + 77 8
N 1.0 0 0.561 3915 3525 - 320 5369 4835 - 946
P 1.0 0.5 0.505 4725 3830 - 15 7150 5796 + 15 c 0 0.5 0.577 3365 3117 - 728 -1105 6325 5858 + 77 -11
R 2.0 0 0.577 3745 3468 - 377 4938 4573 -1208
S 2.0 0.5 0. 509 4763 3891 + 46 7112 5810 + 29
E 0 1.0 0. 560 3305 2971 - 874 -1194 5762 5179 - 602 -154
N ' 1.0 0 0.561 3915 3525 - 320 5369 4835 - 946
T 1.0 1. 0 0.491 5075 4000 + 155 8075 6364 + 583
G 0 2.0 0. 541 3510 3048 - 797 -1117 6245 5423 - 3 ' 58 -13
N 1.0 0 0. 561 3915 3525 - 320 5369 4835 - 946
U 1.0 2.0 0. 493 5525 4372 + 527 7938 6281 + 500
J 0 3.0 0.552 3030 2685 -1160 -1480 5700 5050 - 731 -16
N 1.0 0 0.561 3915 3525 - 320 5369 4835 - 946
V 1.0 3.0 0.467 6419 4812 + 967 8531 6395 + 614
0 4.0 0. 540 3235 2804 -1041 -1361 5512 4778 -1003 -19
N 1.0 0 0. 561 3915 3525 - 320 5368 4835 - 946
1.0 4.0 0.483 5525 4283 + 438 7489 5805 + 24
E 0 1. 0 0.560 3305 2971 - 874 -1251 5762 5179 - 602 -18
R 2.0 0 0.577 3745 3468 - 377 4938 4573 -1208
X 2.0 1. 0 0.541 4113 3572 - 273 6762 5872 + 91
G 0 2.0 0.541 3510 3048 - 797 -1174 6245 5423 - 358 -156
R 2.0 0 0.577 3745 3468 - 377 4938 4573 -1208 y 2.0 2.0 0. 519 4763 3968 + 123 6931 5774 7 j 0 3.0 0.552 3030 2685 -1160 -1537 5700 5050 - 731 -193
R 2.0 0 0.577 3745 3468 - 377 4938 4573 -1208 z 2.0 3.0 0.487 5388 4212 + 367 7256 5672 - 102
L 0 4.0 0.540 3235 2804 -1041 -1418 5512 4778 -1003 -221
R 2.0 0 0.577 3745 3468 - 377 4938 4573 -1208
ZZ 2.0 4.0 0.475 5925 4516 + 671 8356 6370 + 589
L 0 4.0 0.540 3235 2804 -1041 -1418 5512 4778 -1003 -221
R 2.0 0 0.577 3745 3468 - 377 4938 4573 -1208
ZZ* 2.0 4.0 0.480 4790 3690 - 155 6825 5258 - 523
3 0.5 0 0.547 3950 3468 - 377 -12S1 5819 5109 - 672 -127 ε 0 1.0 0.560 3305 2971 - 874 5762 5179 - 602
FF* 0.5 1. 0 0.493 5055 4000 + 155 7819 6187 + 406
G 0 2.0 0. 541 3510 3048 - 797 -1117 6245 5423 - 358 -130
K 1.0 0 0. 561 3915 3525 - 320 5369 4834 - 947 uu« 1.0 2.0 0.493 5170 4091 + 246 7475 5915 + 134
Sucrose added as a solution
EXAMPLE 4 The mortars shown in Table IV comprise a cement having the following analysis:
CaO 51.7%
A1 2 0 3 12.3%
SiO 16.0%
SO 14.1% e 2 0 3 2.3%
Na O 0.1%
MgO Minor
TiO Minor
K O Minor and the calculated compound composition: 21.6% CSA, 17.6% calcium sulfate, 45.9% dicalcium silicate, 7.1% tetracalcium al ' uminoferrite. These mortars are mixed according to the general procedure of Example 1 except that the sucrose, as well as the citric acid, is added as an aqueous solution along with the mix water. The compressive strengths given in Table IV are deter¬ mined in the same manner as in Example III but not beyond the 7 day curing period.
The time of initial set of the mortars described in Example 4 and Table IV is given in Table V. The results show that the citric acid/sucrose combination synergistically retards the set at concentrations of 0.25% acid/0.25% sucrose and 0.25% acid/0.5% sucrose.
0_ * _FI
WIPO -
TABLE IV COMPRESSIVE STRENGTH (PSI)
% Citric % 24 Hr . Difference (x - A ) 7 Day Dif ference ( x - A )
Mortar Acid Sucrose W/C 24 Hr , at W/C=0. 56 Actual Cumulative 7 day at W/C=0. 56 Actual Cumulative
AA 0 0. 56 4210 4210 .4350 4350
BZ 0.13 0 0.51 4465 4067 -143 -406 5050 4601 +251 +350
CZ 0 0.25 0.52 4250 3947 -263 4790 4449 + 99
DZ 0.13 0.25 0.49 4580 4008 -202 5480 4795 +445
BZ 0.13 0 0.51 4465 4067 -143 -667 5050 4601 +251 + 52
E2 0 0.50 0.52 3970 3686 -524 4470 4151 -199
VZ 0.13 0.50 0.48 4530 3883 -327 5375 4608 +258
CZ 0 0.25 0.52 4250 3947 -263 -124 4790 4449 + 99 54
GZ 0.25 0 0.50 4870 4349 +139 4700 4197 -153
HZ 0.25 0.25 0.48 4700 4029 -181 >6000 >5000 >650
GZ 0.25 0 0.50 4870 4349 +139 -385 4700 4197 -153 -252
EZ 0 0.50 0.52 3970 3686 -525 4470 4151 - 99
JZ 0.25 0.50 0.47 4790 4020 -190 5738 4817 +467
TABLE V
% Iniial Set Citric % Difference (x -A) Mortar Acid Sucrose W/C Actual Cumularive
AA 0.53 27
EZ 0.25 0 0.50 59 +32 +35
CZ 0 0.25 0.50 30 + 3
FZ 0.25 0.25 0.50 72 +45
EZ 0.25 0 0.50 59 +32 ÷39
GZ 0 0.50 0.50 34 + 7
JZ 0.25 0.50 0.50 73 +46
OMPI
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