ADMIXTURES AND METHOD FOR ACCELERATING THE SETTING OF PORTLAND CEMENT COMPOSITIONS

ADJUVANTS DE CIMENT PORTLAND ET METHODE POUR ACCELERER LE DURCISSEMENT

English Abstract

ADMIXTURES AND METHOD FOR ACCELERATING THE
SETTING OF PORTLAND CEMENT COMPOSITIONS
ABSTRACT OF THE DISCLOSURE
A method of and compositions for accelerating the
setting time of portland cement compositions are disclosed. Cer-
tain admixtures, comprising water-soluble carbonates and .alpha.-
hydroxy carbonyl compounds, are employed as accelerators. Pre-
ferred accelerators further comprise water-soluble organic com-
pounds having a plurality of hydroxyl groups. The concentration
of admixture relative to cement necessary to achieve acceleration
depends upon the identity of the admixture, the water-cement
ratio, and the amount and type of aggregate in the composition,
among other factors.

Claims

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. An admixture for accelerating the setting time of
portland cement compositions consisting essentially of a mixture
of:
(a) a first amount of a water-soluble carbonate compound
selected from the group consisting of sodium carbonate
and potassium carbonate;
(b) a second amount of an .alpha.-hydroxy carbonyl compound
selected from the group consisting of dl-mandelic
acid and the water-soluble salts of hydroxy-acetic
acid, lactic acid, 2-methyllactic acid, and dl-mand-
elic acid; and
(c) a third amount of a water-soluble organic retardant
selected from the group consisting of retarding or-
ganic compounds having a plurality of hydroxy groups,
citric acid, and the sodium, potassium, and calcium
salts of citric acid.
2. The admixture of claim 1 in which the water-soluble
carbonate compound is sodium carbonate.
3. The admixture of claim 2 in which the .alpha.-hydroxy
carbonyl compound is sodium hydroxyacetate.
4. The admixture of claim 3 in which the water-sol-
uble organic retardant is sodium gluconate.
5. An admixture for accelerating the setting time of
portland cement compositions consisting of a mixture of:
(a) a first amount of a water-soluble carbonate compound
selected from the group consisting of sodium carbonate
and potassium carbonate; and
(b) a second amount of an .alpha.-hydroxy carbonyl compound se-
19

lected from the group consisting of dl-mandelic acid
and the water-soluble salts of hydroxy-acetic acid,
lactic acid, 2-methyllactic acid, and dl-mandelic
acid.
6. The admixture of claim 5 in which the water-soluble
carbonate compound is sodium carbonate.
7. The admixture of claim 6 in which the .alpha.-hydroxy
carbonyl compound is sodium hydroxyacetate.
8. A method for accelerating the setting time of a
quantity of portland cement composition comprising mixing with
the composition:
(a) a first amount of a water-soluble carbonate compound
selected from the group consisting of sodium carbonate
and potassium carbonate; and
(b) a second amount of an .alpha.-hydroxy carbonyl compound se-
lected from the group consisting of hydroxy-acetic
acid, lactic acid, 2-methyllactic acid, dl-mandelic
acid and their water-soluble salts, the second amount
being effective to accelerate the portland cement
composition in the absence of any other admixture;
the first and second amounts being effective in combination to
accelerate the portland cement composition, and essentially the
only constituents of the accelerated portland cement combination
affecting its setting time being the water-soluble carbonate
compound, the .alpha.-hydroxy carbonyl compound, and portland cement.
9. The method of claim 8 in which the carbonate com-
pound is sodium carbonate.
10. The method of claim 9 in which the .alpha.-hydroxy car-
bonyl compound is sodium hydroxyacetate.

11. The method according to claim 8 in which the
first amount of water-soluble carbonate compound and the second
amount of .alpha.-hydroxy carbonyl compound are such that the final
setting time of the portland cement composition containing the
two amounts is greater than the final setting time of a corres-
ponding control portland cement composition in which the water-
soluble carbonate compound is omitted, the final setting times
being measured by the Vicat Needle test.
12. A method for accelerating the setting time of a
quantity of portland cement composition comprising mixing with
the composition:
(a) a first amount of a water-soluble carbonate compound
selected from the group consisting of sodium carbonate
and potassium carbonate; and
(b) a second amount of an .alpha.-hydroxy carbonyl compound
selected from the group consisting of hydroxy-acetic
acid, lactic acid, 2-methyllactic acid, dl-mandelic
acid and their water-soluble salts, the second amount
being effective to accelerate the portland cement
composition in the absence of any other admixture;
the first and second amounts being effective in combination to
accelerate the portland cement composition, and essentially the
only constituents of the accelerated portland cement composition
affecting its setting time being the water-soluble carbonate
compound, the .alpha.-hydroxy carbonyl compound, portland cement, and
water.
13. The method of claim 12 in which the carbonate
compound is sodium carbonate and the .alpha.-hydroxy carbonyl compound
is sodium hydroxyacetate.
14. The method according to claim 12 in which the
first amount of water-soluble carbonate compound and the second
21

amount of .alpha.-hydroxy carbonyl compound are such that the final
setting time of the portland cement composition containing the
two amounts is greater than the final setting time of a corres-
ponding control portland cement composition in which the water-
soluble carbonate compound is omitted, the final setting times
being measured by the Vicat Needle test.
15. A method for accelerating the setting time of
a quantity of portland cement composition comprising mixing with
the composition:
(a) a first amount of a water-soluble carbonate compound
selected from the group consisting of sodium carbonate
and potassium carbonate;
(b) a second amount of an .alpha.-hydroxy carbonyl compound
selected from the group consisting of hydroxy-acetic
acid, lactic acid, 2-methyllactic acid, dl-mandelic
acid and their water-soluble salts; and
(c) a third amount of a water-soluble organic retardant
selected from the group consisting of retarding or-
ganic compounds having a plurality of hydroxy groups,
citric acid, and the sodium, potassium, and calcium
salts of citric acid;
the amounts being effective in combination to accelerate the
portland cement composition, and essentially the only constit-
uents of the accelerated portland cement composition affecting
its setting time being the water-soluble carbonate compound,
the .alpha.-hydroxy carbonyl compound, the water-soluble organic
retardant, and portland cement.
16. The method of claim 15 in which the carbonate
compound is sodium carbonate, and the .alpha.-hydroxy carbonyl com-
pound is sodium hydroxyacetate.
17. The method of claim 16 in which the water-soluble
organic retardant is sodium gluconate.
22

18. The method of claim 17 in which:
(a) the ratio of the weight of the sodium carbonate to
the weight of the cement in such composition is in
the range of from about 6 x 10-4 to about 2 x 10-2;
(b) the ratio of the weight of the sodium hydroxyacetate
to the weight of the cement in such composition is in
the range of from about 6 x 10-4 to about 5 x 10-2;
and
(c) the ratio of the weight of the sodium gluconate to
the weight of the cement in such composition is in
the range of from about 8 x 10-5 to about 3 x 10-2.
19. The method according to claim 15 in which the
first amount of water-soluble carbonate compound and the second
amount of .alpha.-hydroxy carbonyl compound are such that the final
setting time of the portland cement composition containing the
first, second, and third amounts is greater than the final set-
ting time of a corresponding control portland cement composition
in which the first amount of the water-soluble carbonate compound
is omitted, the final setting times being measured by the Vicat
Needle test.
20. A method for accelerating the setting time of a
quantity of portland cement composition comprising mixing with
the composition:
(a) a first amount of a water-soluble carbonate compound
selected from the group consisting of sodium carbonate
and potassium carbonate;
(b) a second amount of an .alpha.-hydroxy carbonyl compound
selected from the group consisting of hydroxy-acetic
acid, lactic acid, 2-methyllactic acid, dl-mandelic
acid and their water-soluble salts; and
(c) a third amount of a water-soluble organic retardant
selected from the group consisting of retarding or-
23

ganic compounds having a plurality of hydroxy groups,
citric acid, and the sodium, potassium, and calcium
salts of citric acid;
the amounts being effective in combination to accelerate the
portland cement composition, and essentially the only constit-
uents of the accelerated portland cement composition affecting
its setting time being the water-soluble carbonate compound,
the .alpha.-hydroxy carbonyl compound, the water-soluble organic re-
tardant, portland cement, and water.
21. The method of claim 20 in which the carbonate
compound is sodium carbonate, and the .alpha.-hydroxy carbonyl com-
pound is sodium hydroxyacetate.
22. The method of claim 21 in which the water-soluble
organic retardant is sodium gluconate.
23. The method of claim 22 in which:
(a) the ratio of the weight of the sodium carbonate to
the weight of the cement in such composition is in
the range of from about 6 x 10-4 to about 2 x 10-2;
(b) the ratio of the weight of the sodium hydroxyacetate
to the weight of the cement in such composition is
in the range of from about 6 x 10-4 to about 5 x 10-2;
and
(c) the ratio of the weight of the sodium gluconate to
the weight of the cement in such composition is in
the range of from about 8 x 10-5 to about 3 x 10-2.
24. The method according to claim 20 in which the
first amount of water-soluble carbonate compound and the second
amount of .alpha.-hydroxy carbonyl compound are such that the final
setting time of the portland cement composition containing the
first, second, and third amounts is greater than the final set-
24

ting time of a corresponding control portland cement composition
in which the first amount of water-soluble carbonate compound
is omitted, the final setting times being measured by the Vicat
Needle test.
25. A fast-setting, premixed portland cement compos-
ition comprising:
(a) portland cement;
(b) aggregate;
(c) a first amount of a water-soluble carbonate compound
selected from the group consisting of sodium carbonate
and potassium carbonate; and
(d) a second amount of an .alpha.-hydroxy carbonyl compound
selected from the group consisting of dl-mandelic
acid and the water-soluble salts of hydroxyacetic
acid, lactic acid, 2-methyllactic acid, and dl-mandelic
acid, the second amount being effective to accelerate
the portland cement and aggregate mixture in the ab-
sence of any other admixture;
the first and the second amounts being effective in combination
to accelerate the portland cement and aggregate mixture, and
essentially the only constituents of the accelerated portland
cement composition affecting its setting time being the water-
soluble carbonate compound, the .alpha.-hydroxy carbonyl compound,
and portland cement.
26. The composition of claim 25 in which the carbon-
ate compound is sodium carbonate.
27. The composition of claim 26 in which the .alpha.-hy-
droxy carbonyl compound is sodium hydroxyacetate.
28. The composition of claim 25 in which the first
amount of water-soluble carbonate compound and the second amount
of .alpha.-hydroxy carbonyl compound are such that the final setting

time of the portland cement composition containing the two amounts
is greater than the final setting time of a corresponding control
portland cement composition in which the water-soluble carbonate
compound is omitted, the final setting times being measured by
the Vicat Needle test.
29. A fast-setting, premixed portland cement compos-
ition comprising:
(a) portland cement;
(b) aggregate;
(c) a first amount of a water-soluble carbonate compound
selected from the group consisting of sodium carbonate
and potassium carbonate;
(d) a second amount of an .alpha.-hydroxy carbonyl composition
selected from the group consisting of dl-mandelic
acid and the water-soluble salts of hydroxy-acetic
acid, lactic acid, 2-methyllactic acid, and dl-mande-
lic acid; and
(e) a third amount of a water-soluble organic retardant
selected from the group consisting of retarding or-
ganic compounds having a plurality of hydroxy groups,
citric acid, and the sodium, potassium, and calcium
salts of citric acid;
the first, the second, and the third amounts being effective in
combination to accelerate the portland cement and aggregate mix-
ture, and essentially the only constituents of the accelerated
portland cement composition affecting its setting time being
the water-soluble carbonate compound, the .alpha.-hydroxy carbonyl
compound, the water-soluble organic retardant, and portland
cement.
30. The composition of claim 29 in which the carbon-
ate compound is sodium carbonate.
26

31. The composition of claim 30 in which the .alpha.-hydroxy
carbonyl compound is sodium hydroxyacetate.
32. The composition of claim 31 in which the water-
soluble organic retardant is sodium gluconate.
33. The composition of claim 32 in which:
(i) the ratio of the weight of the sodium carbonate to the
weight of the cement is in the range of from about
6 x 10-4 to about 2 x 10-2;
(ii) the ratio of the weight of the sodium hydroxyacetate
to the weight of the cement is in the range of from
about 6 x 10-4 to about 5 x 10-2; and
(iii) the ratio of the weight of the sodium gluconate to
the weight of the cement is in the range of from
about 8 x 10-5 to about 3 x 10-2.
34. The composition of claim 29 in which the first
amount of water-soluble carbonate compound and the second amount
of .alpha.-hydroxy carbonyl compound are such that the final setting
time of the portland cement composition containing the first,
second, and third amounts is greater than the final setting
time of a corresponding oontrol portland cement composition in
which the first amount of the water-soluble carbonate compound
is omitted, the final setting times being measured by the Vicat
Needle test.
35. A fast-setting, premixed mortar consisting essen-
tially of the following ingredients in approximately the propor-
tions recited:
<IMG>
27

36. The mortar of claim 35 further including approx-
imately 0.05 parts by weight of stone dust.
37. A method for accelerating the setting time of a
quantity of portland cement composition comprising mixing with
the composition:
(a) a first amount of a water-soluble carbonate compound
selected from the group consisting of sodium carbonate
and potassium carbonate; and
(b) a second amount of an .alpha.-hydroxy carbonyl compound se-
lected from the group consisting of hydroxy-acetic
acid, lactic acid, 2-methyllactic acid, dl-mandelic
acid and their water-soluble salts, the second amount
being effective to accelerate the portland cement
composition in the absence of any other admixture;
the first and second amounts being effective in combination to
accelerate the portland cement composition, and the only consti-
tuents of the accelerated portland cement composition being the
water-soluble carbonate compound, the .alpha.-hydroxy carbonyl com-
pound, portland cement, and aggregate.
38. A method for accelerating the setting time of a
quantity of portland cement composition comprising mixing with
the composition:
(a) a first amount of a water-soluble carbonate compound
selected from the group consisting of sodium carbonate
and potassium carbonate; and
(b) a second amount of an .alpha.-hydroxy carbonyl compound
selected from the group consisting of hydroxy-acetic
acid, lactic acid, 2-methyllactic acid, dl-mandelic
acid and their water-soluble salts, the second amount
being effective to accelerate the portland cement
composition in the absence of any other admixture;
28

the first and second amounts being effective in combination to
accelerate the portland cement composition, and the only consti-
tuents of the accelerated portland cement composition being
the water-soluble carbonate compound, the .alpha.-hydroxy carbonyl
compound, portland cement, aggregate, and water.
39. A method for accelerating the setting time of a
quantity of portland cement composition comprising mixing with
the composition:
(a) a first amount of a water-soluble carbonate compound
selected from the group consisting of sodium carbon-
ate and potassium carbonate;
(b) a second amount of an .alpha.-hydroxy carbonyl compound
selected from the group consisting of hydroxy-acetic
acid, lactic acid, 2-methyllactic acid, dl-mandelic
acid and their water-soluble salts; and
(c) a third amount of a water-soluble organic retardant
selected from the group consisting of retarding or-
ganic compounds having a plurality of hydroxy groups,
citric acid, and the sodium, potassium, and calcium
salts of citric acid;
the amounts being effective in combination to accelerate the
portland cement composition, and the only constituents of the
accelerated portland cement composition being the water-soluble
carbonate compound, the .alpha.-hydroxy carbonyl compound, the water-
soluble organic retardant, portland cement, and aggregate.
40. A method for accelerating the setting time of a
quantity of portland cement composition comprising mixing with
the composition:
(a) a first amount of a water-soluble carbonate compound
selected from the group consisting of sodium carbonate
and potassium carbonate;
29

(b) a second amount of an .alpha.-hydroxy carbonyl compound
selected from the group consisting of hydroxy-acetic
acid, lactic acid, 2-methyllactic acid, dl-mandelic
acid and their water-soluble salts; and
(c) a third amount of a water-soluble organic retardant
selected from the group consisting of retarding or-
ganic compounds having a plurality of hydroxy groups,
citric acid, and the sodium, potassium, and calcium
salts of citric acid;
the amounts being effective in combination to accelerate the
portland cement composition, and the only constituents of the
accelerated portland cement composition being the water-soluble
carbonate compound, the .alpha.-hydroxy carbonyl compound, the water-
soluble organic retardant, portland cement, aggregate and water.
41. A fast-setting, premixed portland cement composi-
tion consisting of:
(a) portland cement;
(b) aggregate;
(c) a first amount of a water-soluble carbonate compound
selected from the group consisting of sodium carbonate
and potassium carbonate; and
(d) a second amount of an .alpha.-hydroxy carbonyl compound
selected from the group consisting of dl-mandelic
acid and the water-soluble salts of hydroxy-acetic
acid, lactic acid, 2-methyllactic acid, and dl-mande-
lic acid, the second amount being effective to accel-
erate the portland cement and aggregate mixture in
the absence of any other admixture;
the first and the second amounts being effective in combination
to accelerate the portland cement and aggregate mixture.
42. The composition of claim 41 in which the carbon-

ate compound is sodium carbonate and the .alpha.-hydroxy carbonyl
compound is sodium hydroxyacetate.
43. The composition of claim 41 in which the first
amount of water-soluble carbonate compound and the second amount
of .alpha.-hydroxy carbonyl compound are such that the final setting
time of the portland cement composition containing the two
amounts is greater than the final setting time of a correspond-
ing control portland cement composition in which the water-
soluble carbonate compound is omitted, the final setting times
being measured by the Vicat Needle test.
44. A fast-setting, premixed portland cement comp-
osition comprising of:
(a) portland cement;
(b) aggregate;
(c) a first amount of a water-soluble carbonate compound
selected from the group consisting of sodium carbon-
ate and potassium carbonate;
(d) a second amount of an .alpha.-hydroxy carbonyl compound
selected from the group consisting of dl-mandelic
acid and the water-soluble salts of hydroxy-acetic
acid, lactic acid, 2-methyllactic acid, and dl-mande-
lic acid; and
(e) a third amount of a water-soluble organic retardant
selected from the group consisting of retarding or-
ganic compounds having a plurality of hydroxy groups,
citric acid, and the sodium, potassium, and calcium
salts of citric acid;
the first, the second and the third amounts being effective in
combination to accelerate the portland cement and aggregate
mixture.
45. The composition of claim 44 in which the carbonate
31

compound is sodium carbonate, the .alpha.-hydroxy carbonyl compound
is sodium hydroxyacetate, and the water-soluble organic retar-
dant is sodium gluconate.
46. The composition of claim 45 in which:
(i) the ratio of the weight of the sodium carbonate to
the weight of the cement is in the range of from
about 6 x 10-4 to about 2 x 10-2;
(ii) the ratio of the weight of the sodium hydroxyacetate
to the weight of the cement is in the range of from
about 6 x 10-4 to about 5 x 10-2; and
(iii) the ratio of the weight of the sodium gluconate to
the weight of the cement is in the range of from
about 8 x 10-5 to about 3 x 10-2.
47. The composition of claim 44 in which the first
amount of water-soluble carbonate compound and the second amount
of .alpha.-hydroxy carbonyl compound are such that the final setting
time of the portland cement composition containing the first,
second and third amounts is greater than the final setting time
of a corresponding control portland cement composition in which
the first amount of the water-soluble carbonate compound is
omitted, the final setting times being measured by the Vicat
Needle test.
32

Description

107 ~ 1 5
`~ 7~
' 101
12
13
14 I
15 I - :
16 FIELD OF TtlE I~IVENTION .;
17 ¦ This invention relates to a method of accelerating the
18 ¦sett-ng time of concretes, mortars, and other compositions con-
lg ¦taining portland cement ~i.e. 'Iportland cement compositions").
20 ¦ . ~ACKGROUN~ dF THE INVENTION
I . . .
21¦ Additi~es for modifying the setting time and other ~`
22.1 properties of portland cement composition.s have been employed
231 ~ir~ually since the beginning of cement technology in ~he 1870's.
24 Cement itself, a mixture of (l) a lime-containing material such
2~ as limestone, shell or Chalk, and (2) clay or a source of clay
261 such as shalQ or slate, flash sets in a matter of seconds or
27¦ minute~ when mixecl with water, leaving virtually no time for ade- I
28¦ quat~ mixing, pouring, or other necessary processing operations
291 To make it commerc:ially useul, ~herefor~, essentially all cement
301 as sold contain~ a ~w percent gypsum, which delays setting for
.. l ~ , . :"''
- 2 - ~
. ' ' '' ' .'
: ~ ., . ' . '
, . . , , . ~ .,, : .
... . ~ .

` " 1C~7841~
a number of hours. In order to shorten or lengthen the setting
time for specific applications, accelerating or retarding ad-
mixtures are employed. Such admixtures are defined by ASTM
publication C 494-71, which also defines "water reducing" ad-
mixtures as those which reduce the amount of water necessary
to produce concrete of a given consistency. Both accelerating
and retarding admixtures are known which also effect water
reduction.
The setting times for commercially available cements vary
10 fairly widely, but are typically on the order of three hours
as determined by the final setting time of the Gillmore or
Vicat Needle methods (ASTM C 266 or ASTM C 191). The setting
times of mortars made with such cements measured by the initial
setting time of the Proctor Needle test (ASTM C 403) is about
seven hours. These setting times must be significantly reduced,
for example, in the manufacture of molded concrete products such
as concrete blocks, in the manufacture of pavements and bridge
surfaces, and in the construction of concrete buildings. In
numerous applications, the impetus for shortening the setting
2~ time is at least in part the high cost of overtime labor.
As is widely recognized in this art, the Gillmore Needle,
the Vicat Needle, and Proctor Needle tests may be used to de-
termine setting times of portland cement compositions of various
proportions and are not restricted to the specific compositions
and proportions of ingredients, e.g. water-cement ratios, recited
in ASTM C 266, ASTM C 191, and ASTM C 403. As used herein the
terms "Gillmore Needle test", "Vicat Needle test" and "Proctor
Needle test" refer to carrying out generally the procedures
specified in the ASTM references on the particular sample of
portland cement composition of interest.
One application which inherently demands very short
: . .: , . . : . .
- . , : ': -
... ..

7~41~;
- setting times is shotcreting, a process of spraying mortar on
a supporting surface to obtain both structural strength and
desired surface properties. Shotcreting is employed for example
in the construction of tunnels drilled through rock, and the
concrete must achieve a high percentage of its ul~imate strength,
after it is sprayed on, in a shorter period than the relaxation
time of the rock in order to prevent the tunnel from collapsing.
There are both so-called wet and dry shotcrete processes.
~; In the wet process, the cement mixture including water is fully
prepared and then sprayed on the tunnel wall or other surface
f~om a nozzle. In the dry process, all the dry ingredients are
mixed and fed to the nozzle, and the water is added in the nozzle.
Note that greater acceleration of setting time can be achieved
generally with the dry process because there is no risk of the
mixture setting up in the equipment prior to being sprayed. In
either process the shotcrete must harden in less than fifteen
minutes, as measured by the Proctor Needle test final setting
time, in order that a useful thickness of shotcrete may be
; applied to a surface without its sloughing off.
Accelerating admixtures for shotcreting in general
` commercial use today are mixtures of sodium carbonate and sodium
aluminate. While they afford acceptable early strengths relat-
ive to plain mortar, they typically reduce the ultimate strength
of the mortar by more than half, requiring the use of thicker
- layers~of mortar than would be necessary in the absence of the
accelerator to achieve the same structural strength. Addition-
ally, these admixtures are highly caustic and great care must
be taken in handling them. Only a limited degree of acceler-
ation can be achieved with sodium carbonate-sodium aluninate
accelerators without reducing the ultimate strength of the
shotcrete to an ~;
.
-4-
.
- ~: : : . . :. : ,
: . . . - - , . . ~ .
,: ,

3L~7~
unacceptable level. There exist applications requiring shorter
setting times and rapid early strength development for which no
satisfactory accelerating admixtures have been available.
A second application which requires very fast setting
times is the use of portland cement plugging compounds. Plugging
compounds consist of portland cement~ fine aggregate such as
mason's sand, and an accelerator and are used to repair broken
' or cracked concrete when water is leaking through the fracture.
Plugging compounds must have a final setting time as measured
by the Vicat Needle test of less than fifteen minutes in order
to ensure that the compound will harden and stop the leak before
it is washed away.
Portland cement compositions used to repair damaged con-
crete articles and structures must harden quickly so that the
- time taken to make the repair will be short. Quick-setting-
mortar compounds generally consist of portland cement, fine
aggregate, and an accelerator and are used for repairing chipped
or cracked concrete and other small jobs. They require final
setting times of thirty minutes or less as measured by the
Vicat Needle method. Concrete patching compounds contain cement,
coarse and fine aggregate, and an accelerator and are generally
used for making larger repairs such as filling potholes in con-
crete pavement. Concrete patching compounds must have final
setting times of one hour or less as measured by the Vicat test.
Their setting times typically are somewhat longer than those of
quick-setting-mortar compounds because of the longer time re-
quired to mix and apply the larger quantities of concrete patch-
ing compound. The Vicat Needle test may be carried out directly
on samples of mortar. In the case of concrete, the Vicat test
is carried out on the mortar of the sample, which may be sep-
arated from the coarse aggregate

~784~5
by sieving, as provided in ASTM C 403.
Perhaps the most widely used accelerator for most con-
crete applications is calcium chloride. Although it does not
accelerate setting times sufficiently for use in shotcrete
processes, it is used for most other applications and has the
advantage of being very inexpensive. It is severely limited,
however, in that chloride ion is highly corrosive in contact
with ferrous metals, and also promotes an electrochemical re-
- action between dissimilar metals. Hence calcium chloride gen-
erally cannot be used as an accelerator for reinforced concrete
or other applications involving concrete-metal interfaces.
A review of the prior art relating to accelerators in
general and to hydroxy-carbonyl retarders demonstrates that it
is difficult to make generalizations about the effect of broad
classes of compounds on the setting times of portland cement.
For example, although the essentially ionic salt calcium chlor-
ide is an efficient accelerator, sodium chloride and potassium
chloride, also ionic chlorides, are substantially less efficient
accelerators. Moreover, merely because a particular compound
functions as an accelerator does not imply that there are
concentrations at which it will shorten setting times sufficient-
ly to be used in applications such as shotcrete and plugging com-
pounds, which require particularily short setting times. As
noted above, for example, calcium chloride is a widely used
accelerator for portland cement, but it does not shorten setting
times sufficiently to be used for shotcreting.
The problems of making generalizations about the effects
of an admixture on the setting times of portland cement composi-
tions are compounded if the admixture has more than one constit-
uent, each of which individually has a different effect on thesetting
~: :
: . . - . :~:. .
:- . . : .: . :

1078~15
of portland cement compositions. It is not po~sible in gener~l
2 to decide if a particular mixture of an accelerator and a
retarder will accelerate or retard a portland cement composition.
4 The difficulties in predicting the effects of
5 compounds and mixtures of c~mpounds on the setting times of
6 portland cement compositions stem from the fact that changing
7 setting times is a catalytic effect. In many fields of
8 chemistry it is recogni~ed that the mechanisms of catalysis
9 are relatively poorly understood. The field of cement chemistry
lO is no exception. Since even the basic reactions involved in the
- 11 hardening of portland cement are not fully understood at this
12 time, the effect of a given admixture in catalylzing the reactions
1 13 i.e. in accelerating or retarding setting times, i9 for the most
14¦ part impossible to predict successfully. In general, resork must
15¦ be had to empirical measurements.
16¦ It has been known since the late 1930's that certain
17¦ organic hydroxy carbonyl compounds could influence the setting
18¦ times of portland cement. The prior art teaches that certain
191 hydroxy carbonyl compounds, including some of the -hydroxy
21 car~onyl compounds included in the accelerators of the present
invention, ~a~d the setting of portland cement rather than
22 accelerate it. This prior art, the most p-ertinent of which is
discussed below, does not disclose or suggest the accelerators
226 f the present invention and in fact strongly suggests th~t such
compounds would not function as accelerators.
26 One reference teaches broadly that the ~-hydroxy
27 carbonyl group,
28 11 --- C _ C--, ia Very aative in retarding the
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11 10784~L5
1 hydration o~ portland cement, the degree o~ hydration being a
2 measure of its de~ree of hardening. In this re~erence, "Proceed-
3 ings of the International Symposium on the Ch~mistry oE Cement,"
4 Washington, D.C~ 1960, pages ~24-925, J. H. Taplin classifies
hydroxyacetic acid as a strong ret~rder on the basis o~ data
obtained from cement paste specimens having water-cement ratios
7 of 0.30 and containing one percent admixture by weight. Lactic
8 acid, classified as having a negligible retarding effect, is calle d
9 exceptional in that it contains the ~-hydroxy arbonyl group but
does not retard. Taplin nonetheless concludes that "it appears
11 to be a general rule, that for an organic substance to ~Q~a~
12 cement, it must have at least two oxygen atoms each bound to a
13 single but different carbon atom in such a way that the oxygen
14 atoms can approach each other." The Taplin refexence contains
16 no teaching or suggestion that hydroxyacetic or lactic acid might
16 be useful individually as accelerators for portland cement com-
17 positions, or in combination with one or more other ingredients
18 to form an accelerating admixture.
19 A second reference which similarly teaches away from
the present invention is U. S. Patent No. 3,144,347, issued
21 August 11, 1964 to E. I. du Pont de Nemours & Company. The '34
22 patent teaches the use of hydroxyacetic acid, lactic acid, and
23 their sodium, calcium, potassium and amine salts as retardin~
24 admixtures in concentrations ranging ~rom about 0.001 to 3.5
weight percent relative to the Cemellt. The patent recites further
2~ tColumn 1, lines 33-35) that "most orten less than about 0.8
27 weight percent will be used, and particularly advantageous results
28 are obtained within the narrow range of 0.01 to 0.1 weight
29 percent". All of the specific examples contaîned in columns
3 and 4 of the pat:ent relate to the use of less th~n 0.8 weight
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I ~ 8415
::~ i
1¦ percent of the fore~oing retard~nt admixtures in concretes. The
second paragraph of the patent de~ine~ the scop~ of the ~sserted
3 invention as relating to "a small class o~ monohydroxy organic
4 compounds ~ . . which not only serve as excellent water reducing
retardants but at the same time causes a signi~ican~ increase
in the compressive strength of the concrete." The sole and plain
7 teachin~ of the '347 patent is thus that ~he recited compounds
8 are useful as retarding agents and, concomitantly,as ultimate
91 strength increasing agents.
10¦ The only suggestion whatsoever in the prior art that a
11¦ specific -hydroxy carbonyl compound may have some utility as an
12¦ accelerator is found in Japanese Patent Application Publication
13¦ 13680 of 1972, dated 24 April 1972 and assigned to Hani Chemical
14¦ Company, Ltd., by Kenji Harazawa. Precisely what the Harazawa
1~¦ patent does or does not teach one of ordinary skill in this art
is at best unclear. It states that calcium monoglycolate and
1 1 calcium diglycolate effect a limited reduction in the initial
81 setting time of portland cement, and further that "it is particu-
1~ larly preferred to use portland cement and mixed gyps~m plaster."
221 It is unclear what "gypsum plaster" is, or why one would want to
mix it with cement. Although t~e terminology is ambiguous,
22 calcium diglycolate is generally used to r~fer to t~e calcium salt
23 of diglycolic acid, which is not an ~-hydroxy carbonyl compound.
24 Even giving Haraza the benefit of all doubts,his preferred
range is between 0.05 and 0.15 percen-t admixture with respect to
26 the cementt and the shortest final setting time disclosed for
27 either compound is one hour and forty-five minutes, The shoxtest
28 final setting time for calcium monoglycolate is one hour and
S0 fi~ty minutes, as measured by JIS R-5201, a Vicat Needle test.
For rea~ons stated above, it is not possible to extrapolate with
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:~378~
respect to the effect of higher concentrations of admixture, and
Harazawa contains no suggestion whatsoever that the salts recited
by him, or any other compounds, might make useful accelerators
for applications requiring fast setting times such as shotcreting,
plugging compounds, and quick-setting mortars. Furthermore, there
is no suggestion that the salts recited might usefully be combined
with one or more additional compounds to form an accelerator with
the properties disclosed below. The patent contains no suggestion
of the invention disclosed and claimed herein.
As notedabove in connection with shotcreting, sodium
carbonate has been used as a component in accelerators. A book by
Lea and Desch entitled The Chemistry o~ Cement and Concrete,
(Ed~ard Arnold Publishers, 1956) points out on page 252 that
alkali carbonates produce a very strong acceleration of the set,
the addition of 1-2 percent reducing the time of initial set to
a few minutes.
SUMMARY OF THE INVENTION
The present invention relates to an admixture for
accelerating the setting time of portland cement compositions.
The admixture comprises a water-soluble carbonate compound and
; an ~-hydroxy carbonyl compound selected from the group consist-
ing of hydroxyacetic acid, lactic acia, 2-methyllactic acid, dl-
mandelic acid and their water-soluble salts. For example, an
admixture of the present invention might include sodium carbonate
and sodium hydroxyacetate.
Canadian Patent application Serial No. 232,260, filed
July 25, 1975 by the present inventor discloses that certain a-hy-
droxy carbonyl compounds, long thought to retard the setting of
portland cement compositions, could in fact function as accel-
erators. Certain of the accelerators disclosed in the '260application are able to speed the
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84~S
setting of portland cement sufficiently to be useful as accele-
rators in shotcreting applications. In such cases, as noted
above, the final setting time must be less than fifteen minutes
as measured by the Proctor Needle test. Many of the ~-hydroxy
carbonyl accelerators of -the '260 application are capable of re-
ducing portland cement setting time to less than five minutes.
For many applications other than shotcreting, such
extremely short setting times are a disadvantage because they do
not permit enough time for mixing and spreading the cement.
For example, it can take thirty minutes or so to mix, apply,
- 10 and smooth a concrete patch to repair a pothole in a road.
Accelerated concrete with a much shorter setting time would
therefore be unsuitable for that application.
While it is generally possible to obtain setting times
longer than the extremely short setting times required for
shotcreting by carefully selecting the concentration of an
~-hydroxy carbonyl accelerator, such a procedure is not always
practical since the setting time may be unduly dependent upon
accelerator concentration. For example, for setting times of
a mortar above a few minutes the setting time may be so highly
dependent upon sodium hydroxyacetate concentration as to pre-
clude obtaining adequately uniform setting times in production
quantities. Such setting times are additionally very dependent
upon water-cement ratio and similar parameters, further aggra-
vating production control problems.
In the present invention, it has been found that the
combination of an ~-hydroxy carbonyl accelerator with a water-
soluble carbonate salt affords setting times generally signifi-
cantly longer than those obtained with ~-hydroxy carbonyl
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784:~LS
accelerator alone yet substantially shorter than unaccelerated
portland cement and with a more rapid early strength development
than that of the unaccelerated cement.
Combining an ~-hydroxy carbonyl accelerator with a
soluble carbonate also tends somewhat to reduce the dependency
of setting time on admixture concentration, particularly for
setting times only a few minutes longer than the setting times
resulting from the ~-hydroxy carbonyl accelerator alone. For
still longer setting times, however, the setting times have been
found to be erratic and once again concentration dependent,
leading to difficulties in producing mortars of predictable
setting times. The concentration dependence especially makes
it difficult to mix large production batches of mortar suffici-
ently uniformly for different samples taken from a batch to have
the same setting time.
Surprisingly, it has been found possible to achieve
both longer setting times and a greatly reduced concentration
dependence by including a water-soluble organic compound having
a plurality of hydroxy groups with the soluble carbonate and
~-hydroxy carbonyl accelerator. Such compounds, for example
sodium gluconate, are known retarders for portland cement com-
positions. Very low concentrations of such compounds have been
found to have a surprisingly large synergistic effect in length-
ening the setting time and reducing the unpredictability and
concentration dependence of setting times of portland cement
mortars accelerated with a soluble carbonate and an ~-hydroxy
carbonyl compound. Beneficial effects similar to those discussed
above for water-soluble organic compounds having a plurality of
hydroxy groups can also be obtained by using the monohydroxy
compound citric acid or its sodium, potassium, or calcium salts.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The setting time which results from a particular ad-
mixture in accordance with the present invention will vary for
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~7~
specific applications depending upon the composition and concen~
tration of the mixture, the water-cement ratio, the nature and
quantity of aggregates used, the composition of the cement, the
order in which the ingredients are mixed, and the temperature
and other conditions under which the constituents are mixed and
set. A preferred accelerator in accordance with the present
invention includes a mixture of sodium hydroxyacetate, sodium
carbonate, and sodium gluconate. When this mixture is mixed
with a portland cement mortar, the ratio of the weight of sodium
hydroxyacetate to that of the cement is preferably in the range
of from 6 x 10 4 to about 5 x 10 2; the ratio of the weight of
sodium carbonate to that of the cement is preferably in the
range of from about 6 x 10 4 to about 2 x 10 2; and the ratio
of the weight of sodium gluconate to that of the cement is pre-
ferably in the range of about 8 x 10 5 to about 3 x 10 2
Preferred a-hydroxy carbonyl compounds for the present
invention are hydroxyacetic acid, lactic acid, 2-methyllactic
acid, dl-mandelic acid and their sodium, potassium, calcium,
lithium, zinc, and triethanolamine salts. Preferred water-
soluble carbonates are sodium and potassium carbonates.
Preferred water-soluble organic compounds having a
; plurality of hydroxy groups are gluconic acid, lignosulfonic
acid, heptogluconic acid, and their sodium, potassium, and
calcium salts. Polysaccarides are also suitable organic com- ;
pounds having a plurality of hydroxy groups.
In general, the admixture constituents are preferably
selected such that the admixture is approximately neutral in
pH, allowing it to be handled without the special precautions
required in connection with the highly caustic prior-art admix-
tures.
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:" 1'
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: I . . .
1 I ~ The accelerating a~mixtur~s of the present invention
2 ¦ cause neither reaction with ferrous metals nor electrolytic
3 ¦ action between different metals, and are ~hus suitable for use
4 ¦ in connection with reinforced and prestressed concretes as well
5 ¦ as in other applications involving.a cement, mortar, or concxete-
61 metal interface. ..
¦ One of the most surprisi:ng aspects of the present
8¦ invention is that the com~ination of water-soluble carbonate,
¦ which is an accelera~or, with an ~-hydro~y carbonyl compound,
10¦ which is also an accelerator, leads to longer setting times
111 than are obtained with the a-hydroxy carbonyl compound alone.
12¦ One possible explanation for this phenomenon may lie in the
13¦ observation that portland cement is generally composed of three
14¦ principal eomponents, C3A ~tricalcium aluminate), C3S ~tricalcium
15¦ silieate), and C2S (dicalium silicate), which harden at different
16¦ rates and are affected differently by different a~mixturesO The
17¦ hardening of C3A determines the setting time of a cement mix
181 since this component hardens most rapidly~ The early strength
19¦ development, on the other hand, is principally due to the
201 hardening of C3S. Since a-hydroxy carbonyl accelerator~ both
21¦ shorten setting time and speed early strength development, they
22¦ appa.ently accelerate both C3A and C3S. Sodium carbonate and
231 other soluble carbona es, on the other hand, appear to accelerate
~41 the setting of C3S while retarding the setting of C3A. The :
251 acceleration of C3S by soluble carbonates nevertheless is
26 sufficient to eause an overall shortening o~ the setting time
27 relative to unaccelerated cement. The apparent result of mixing
28 an ct-hydroxy carbonyl accelerator with a soluble carbonate`is
29 therefore to moderate the affect of ~he ~-hydroxy carbonyl
accelerator on CIA, but not on C3S. The setting ~ime is thus
.:
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!1 1~7~ L5
,. I
¦ leng~lened, bu~ the early strength development remains sub-
2 ¦ stantially una~fected relative to ~le use of the ~-hydro.Yy
I carbonyl accelerator alone.
5 ¦ Sodium gluconate and other compounds having a plurality
I o~ hydroxy groups appear to moderate ~le affect of the two
6 ¦ accelerators on both C3A and C3S, delaying both setting time
7 ¦ and early strength development somewhat. This is consistent
¦ with the observation that water-soluble organic compounds having
¦ a plurality of hydroxy groups appear to retard the settiny of
101 portland cement by coating the particles of cement wi~h a film
111 thereby reducing contact between the cement particles and water.
Even taking into account the moderation of the early strength
13¦ development caused by the inclusion of sodium gluconate,
141 preferred composite admi~tures o~ the present invention result
15¦ in mortars e~hibiting early streng~hs substantially greater than
16¦ the early strengths of mortars employing prior-art accelerators.
17¦ The foregoing explanation is offered for the sake of completeness
18¦ and is not to be construed as limiting the invention in any way.
19¦ EXAM~LES
201 The following specific examples of portland cement
221 compositions and their effects on setting time will facilitate a
I ~etter understanding of ~he invention.
231 Example I
241 The following dry mortars were prepared:
25¦ A B C
261 :~parts by weight)
Atlas Type I cement 78.0 77.8 77.5
271 Federal Fine Sand 20.0 19.9 19.8
28¦ Sodium Glycolate 2.0 1.9 1.9
291 Sodium Carbonate 0.0 0.4 0.8
501 The final setting time of these mortars a~ measured by ~he Vicat
I . , , .
I . . .

` ~11 . .
: I iLC~78~5
1 ¦ Needle test (using a water-cement ratio of 0.30) and the
2 ¦ compressive strengths after one or five hours were as ~ollows:
I Set~in~ Time Compressive Str~th
4 ¦ Mortar A 1' 15" 1710 psi ~5 hours)
5 ¦ Mortar B 3' 30" 990 psi (1 hour)
6¦ Mortar C 17' 30" 1080 psi (1 hour)
7 ¦ It is apparent tha~ the addition of sodium carbonate leng~hens
8¦ the settins time of the mortar.
l Example II
10¦ The following mortars were prepared:
11¦ D E
l (parts by weight)
i 121 Atlas Type I cement ~7.7 75.5
131 Federal ~ine Sand 1904 18.9
14¦ Sodium Lactate 2.9 2.8
15¦ Sodium Carbonate 0.0 2.8
16¦ The following final se~ting times were measured using ~he Vicat
17¦ Needle test: ~
18¦ Setting Time ~later-Cement Ratio
I . . _ .. _ . . . _ _ ,
¦ Mortar D 1' 0.28
20¦ Mortar E 17' 0.29
21¦ Thus adding sodium carbonate to a mortar accelerated with sodium
231 lac~ate is seen to increase the setting time signi~icantly.
¦ Example III
`241The following dry mortar was prepared:
; ¦Atlas Type I cement 600 g
26Federal Fine sand 400 y
27Sodium Hydroxyacetate 5 g
28 ~rom this mortar the following six samples were prepared for
29 which ~he corresponding initial setting times ~ere measured
30 by the Gillmore Needle test:
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784~S
Sodium Carbon~te Sodium Gluconate Setting
1 Sample (we.ight perc~nt) ~ ~rcent) Time
_ - . ., .,
F 0.2 0 0 3~ 5l-
. G 0.5 0.0 4'10"
.; 4 H 0.8 0.0 5'40"
I 0.2 0.02 17'15"
J o.s ~.~2 16'50"
7 K 0.8 - 0.02 3'30"
.~ The weight percentages are relative to ~he to~al weight of the
9 mortar sample. The water-cement ratio was 0.35.
~ 10 Note that as the concentration of sodium carbonate
- 11 ¦ increases from 0.2 to 0.5 weight percent, the setting time
12 remains essentially constant for samples I and J, which include
13 0.02 weight percent sodium gluconate. Over ~his concentration
14 range, therefore, the setting time of the mortar is quite
. 15 insensitive to the concentration of sodium carbonate.
- 16 Over the same concentration range the addition of
17 sodium gluconate also has the effect of lengthening the initial
18 setting time from about three or four minutes to about
. 19 seventeen minutes. As the concentration of sodium carbonate is
: 20 `increased to 0.8 weight percent, the initial setting time drops
21 to less than four minutes for the samples con~aining sodium .
22 gluconate. .At this concentration, the usual accelerating e~fect
23 of sodium carbonate apparantly predominates over its retarding
24 effect in combination with sodium hydroxyacetate.
Example IV
, . , . .
26 The ollowing fast-setting, premixed mortar was
. 27 prepared: ..
28 . parts l:v weight
.: 29 Hercules Type I cement . .79.2~0
Mason's Sand ~STM ~4)19.B18
' ', . ,
-17- '
:
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- ~ .
1 ~07i3~
1 ¦ Sodium Hydro~yacetate 0.664 .
¦ Sodium Carbonate 0.1~8
3 ¦ Sodium Gluconate 0.005
~ ¦ Stone dust 0-045
;~ ¦The initial setting time of ~his mortar was between five and
6 ~ ten minutes as measured by the Gillmore Needle test with a
; 7 ¦water-cement ratio of 0.3. This mortar is suitable as a quick-
1 1 set~ing r~ar compound.
lG
~21~
232 ; ` .
24 .
.
26 . - .
27 . .
28 .
29 . ' ` .
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.