Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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IMPROVEMENTS IN OR RELATING TO ORGANIC COMPO~NDS
The invention relates to compositions and methods of manufacturing
and applying quick setting concrete. The concrete is capable of
retaining fluidity for a long period of time and then rapidly setting.
The quick setting compositions of this invention
are particularly applicable in lining construction.
Lining construction is a process whereby concrete is applied to a
surface (e.g. of a tunnel or underground cavern). There are two major
types of lining construction processes, as follows:
1. Shotcreting.
This can be carried out using a dry mix concrete (the dry mix
system) or a wet mix concrete (the wet mix system).
a) The dry mix system.
The dry mix system is one in which dry mixed concrete is
pneumatically conveyed through a delivery hose and is applied by
projecting it out from the nozzle under pressure; water and a quick
setting agent being added, upstream of the nozzle just prior to
passage through the nozzle. With this system it is difficult to
control the quantity of water added and therefore to control the
water-cement ratio (hereinafter referred to as the WtC ratio). Further
a lot of dust is generated and this is a drawback. Alternatively the
quick setting agent can be added at the point of mixing instead of
vicinal to the nozzle.
b) The wet mix system
r
.
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The wet mix system is a system in which the concrete is mixed in
the presence of water and is pneumatically conveyed through a delivery
hose to a nozzle and is then projected out of the nozzle; a quick
setting agent being added upstream of the nozzle just prior to passage
through the nozzle. There are also examples of this system where the
concrete can be pumped, rather than pneumatically conveyed, to a point
midway between the point of mixing and the nozzle in the delivery hose
followed by pneumatic conveying between this midpoint and nozzle. The
system allows good control of U/C ratio and generates little dust.
2. Press-on method
This is also known as pressure bonding. The concrete is mixed, and
then pumped (not pneumatically conveyed) to a nozzle through a hose,
with the quick setting agent being added upstream of the nozzle just
prior to passage through the nozzle. The concrete is then poured into
a form at an excavated surface. The concrete is very fluid (about 18
cms in terms of slump) after pouring into the form until immediately
before hardening, that is to say for several minutes after adding of a
quick setting agent. This long setting time can be a disadvantage
because, in order to increase efficiency, one wants to be able to
remove the sheaths of the form as quickly as possible for the next job
and before one can do this, the concrete has to harden to least a
compressive strength of 1 kg/cm 2 in 3 to 5 minutes.
According to the invention, there is provided a cementitious
compo~ition for use e.g., in lining construction comprising;
a) cement and preferably aggregate (hereinafter referred to as
component a)
b) an admixture containing a polycarboxylate copolymer (the
admixture hereinafter being referred to as coni~npnt b); and
c) a quick setting agent or accelerator (herein after referred to
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as component c).
Further according to the invention, there is provided a process
for the production and application of a cementitious composition
comprising;
a) mixing components a) and b) together, preferably in the
presence of water;
b) transfering the mixture to a nozzle for expelling the mixture;
c) introducing component c) upstream of the nozzle prior to
passing the mixture through the nozzle; and
d) expelling the mixture through the nozzle, to apply the mixture
to a surface to be coated.
Preferably component a) ls concrete. This concrete may have a high
proportion of fine aggregate (e.g. sand) in the total quantity of
aggregate. Preferably in component a) the cement used i9 portland
cement and the aggregate that is preferably present is fine aggregate,
preferably sand having an average particle size of less than 5mm. The
aggregate when present may also include coarse aggregate, having a
particle size on average of about 15 mm. Preferably the amount of
aggregate is 50 to 400 Z by weight based on cement.
Preferably the copolymer of c~ ~re~t b) is
a) a water-soluble copolymer of an olefin and an , ~ unsaturated
dicarboxylic acid
b) a water-soluble copolymer of an ester of a polyethylene glycol
monoaryl ether with maleic acid, and optionally monomers capable of
copolymerization with said ester;
c) a water-soluble copolymer of isobutylene-styrene and maleic
-
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acid,
d) a water-soluble copolymer of isobutylene acrylic acid ester and
maleic acid;
e) a water-soluble copolymer of isobutylene styrene acrylic acid
ester and maleic acid; and
f) a water-soluble salt of a copolymer derived from a polyalkylene
glycol monoacrylic acid ester or polyalkylene glycol monomethacrylic
acid ester and acrylic acid or methacrylic acid, optionally together
with a qnC ~r capable of being copolymerised therewith.
Examples of a monomer capable of being copolymerised are esters of
Cl_20 aliphatic alcohols and methacryllc acid or acrylic acid;
methacrylic amides or acrylic amides; maleic acld or fumaric acid or
mono- or di- esters thereof with C1_20 aliphatic alcohols; C2_4
alkylene glycols or poly C2_4 polyalkylene glycols; C2_6 alkenyl
acetates (eg vinyl acetate and propenyl acetate); aromatic vinyl
compounds (eg styrene, p-methyl styrene, styrene sulphonate) or vinyl
halides (eg vinyl chloride).
Preferably the copolymer is derived from a poly C2_4 alkylene
glycol monomethacrylic acid ester or poly C2_~ alkylene glycol
monoacrylic acid ester and acrylic acid or methacrylic acid,
optionally neutralised with alkali.
More preferably the copolymer is derived from
a) a monomer of formula I
CH2=C(Rl)-CO-O-(R2-O)n-R3 (I); and
b) a IQnf -r of formula II
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C~2=C(R1)-COOX (II)
in which
each R1 independently is hydrogen or methyl;
R2 is C2_4 alkylene;
R3 is hydrogen or Cl_6 alkyl;
n is an integer of from 1 eo 100 inclusive; and
X is hydrogen, a monovalent or 1/2 equivalent of a divalent metal,
ammonium or an amine group.
Preferably the copolymer of component b) has a molecular ~eight of
23,000 to 27,000.
The dosages of component b) used are preferably at least O.OlZ,
~ore preferably from 0.01% to 0.5% based on the weight of cement, most
preferably in a range of 0.03 to 0.2Z. ~hat is kno~n as the
"super-fast accelerating effect" becomes larger as dosage is
increased, but when dosages in excess of the upper limit of 0.5X are
used, a ceiling in effectiveness is reached and thus further addition
becomes uneconomical.
- "Accelerator" (component c) is as defined p-106-7, 548 of Concrete
Admixtures ~andbook by V.S. Ramachandran 1984 Noyes Publications..
"Quick-setting agent" (component c) is defined in JIS A 0203,
"Concrete Terminology, n as ~a chemical admixture to be used to
accelerate the hydration reaction of cement and to markedly shorten
time of setting of cement. n Typical examples include:
a) inorganic salts (solid or liquid) comprising alkali aluminates
.
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and alkali carbonates, or mixtures thereof,
b) cement minerals, and
c) natural minerals (e.g. aluminates, water glass and calcium
sulfo-aluminate).
Inorganic salt quick-setting agents include quick-setting agents
comprising an aluminate and/or a carbonate. Natural mineral
quick-setting agents include calcinated alunite to which carbonates
and/or aluminates have been added. Cement mineral quick-setting agents
include cementitious materials comprising calcium aluminates such as
CaO.Al203, 12CaO.7Al203, CaO.2Al203, llCaO.7Al203.CaF2, and
3CaO.3Al203.CaF2, amorphous forms of these minerals, and may also
additionally include amounts of gypsum and/or inorganic salt base
quick-setting agents.
Calcinated Alunite is obtained by burning alunite at a very high
temperature below its melting point. Alunite (or Alum Stone) is a
hydrated basic aluminium and potassium sulphate mineral which has
served as a source of potash and of alumina. Alunite is KAl3
(S04)2(0H)6 having a hardness of 3.5 to 4 on the Mohs' scale.
The amount or dosage of component c) used can be expressed in
terms of percentages by weight of the weight of cement in the
cementitious composition. These are
a) approximately 2 to 8X (solid or liquid product) in case of
inorganic salt quick setting agents,
b) approximately 5 to 10% in case of cement mineral quick setting
agents, and
c) approximately 4 to 10% in case of natural mineral quick setting
agents.
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As quick-setting agents are expensive compared with cement, sand
and gravel (the principal materials used in concrete, which is the
preferred cementitious composition) and the dosage of quick-setting
agent required to obtain optimum super-fast accelerating effect is
larger than for chemical admixtures in general, it is an important
factor in determing the cost of a lining concrete. Accordingly, it is
desirable for the required super-fast accelerating effect to be
achieved with as small a dosage as possible.
Further, with a wet-mix shotcreting process, the super-fast
accelerating effect is smaller than compared with a dry-mix
shotcreting process. One of the causes of this i9 that cement
particles are in contact with water well before they come in contact
with quick-setting agent and so a thin film of initial hydration
product is formed on the surface of the cement particles, and these
obstruct contact between cement particles and quick-setting agent. In
case of a wet-mix process shotcreting system, the consistency of
concrete must be made fairly fluid so that it can be transferred
smoothly through the delivery hose to the nozzle and therefore, it is
unavoidable for U/C ratio to be high. However because the U/C ratio i9
higher in case of a wet-mix shotcreting process than for a dry mix
shotcreting process (a dry-mix shotcreting process has a U/C ratio of
about 0.45:1, whereas for a wet shotcreting process it is 0.55:1 or
higher) and since the super-fast accelerating effect diminishes the
higher the U/C ratio, the quicksetting effect is acutely negatively
influenced in a wet mix shotcreting process. The same is true for the
consistency of the concrete used in a press-on construction method or
pressure bonding method in order to allow good pourability when the
concrete i9 poured into forms.
The use of the component b) in concrete to be mixed before the
addition of a quick setting agent has succeeded in increasing the
super-fast accelerating effect of quick-setting agent in concrete
without impairing the fluidity of the concrete that is to be used as
lining concrete, where the concrete is mixed prior to the later
addition of the quick-setting agent, that is then applied to the
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excavated surface of a tunnel or underground cavern.
By using a method according to the invention in a wet-mix
shotcreting process, there is marked improvement of the super-fast
accelerating property of shotcrete while retaining fluidity of
concrete. It is thereforepossible for the dosage of quick-setting
agent to be reduced to obtain identical super-fast accelerating effect
compared to that required in a conventional wet mix shotcreting
process. Further, since the super-fast accelerating property is
improved, there is a reduction in rebound of material (rate of
material falling off when shotcreted on to a surface) in the
shotcreting method which is a very positive economic bonus. Further,
in producing concrete linings by a press-on or pressure bonding
method, it is possible to increase working efficiency by shortening
the time required for setting after addition of quick-setting agent
whilst maintaining fluidity of the concrete. This is of great
importance.
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The invention will now be illustrated by the follo~ing Examples.
Examples 1 and 2
The concrete of the Examples is made up in the proportions given
in Table to form a lining concrete.
(1) Concrete Ingredients:
(a) Cement:
A blend of Onoda, Mitsubishi and Sumitomo brand ordinary
portland cements in equal amounts.
(b) Coarse Aggregate:
Ohme graywacke crushed stone (specific gravity 2.64,
absorption 0.67X, F.M. = 6.35, maximum size 15 mm)
(c) Fine Aggregate:
A blend of Oi River System pit sand and Chiba pit sand in
equal amounts.
(d) Admixture:
a) Polycarboxylic Acid Admixture
Calcium salt of the copolymer of a poly C2_~ alkylene glycol
monomethacrylic acid ester and methacrylic acid (referred to as
"A~: manufactured by Nisso Haster Builders Co., Ltd.)
b) Lignosulfonate Admixture
Proprietary name: Pozzolith No. 8 (referred to as "B~:
manufactured by Nisso Master Builders Co., Ltd.)
c) Oxycarboxylate Admixture
Sodium gluconate (referred to as "C~)
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d) Sulfonated Naphthalene-Formaldehyde Condensate Admixture
Proprietary name: Mighty 150 (referred to as "D": manufactured
by Kao Soap Co., Ltd.)
e) Sulfonated Melamine Formaldehyde Condensate Admixture
Proprietary name: NL-4000 (referred to as "E~: manufactured by
Nisso Master Builders Co., Ltd.)
f) Inorganic Salt Powder Quick-Setting Agent
Proprietary name: QP-500 (referred to as llpn manufactured by
Nisso Master 8uilders Co., Ltd.)
g) Cement Mineral Quick-Setting Agent Proprietary name: QP-55
(referred to as "G": manufactured by Nisso Master Builders Co.,
Ltd.)
The dosages of all admixtures are the standard dosages
respectively recommended by the manufacturers and are expressed in
terms of percentage by weight of cement.
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In the above Table 1, Examples 1 and 2 illustrate the invention
and Examples I to X are comparative.
After mixing the cement, water, fine aggregate and coarse
aggregate together and admixture A to E if appropriate, the re~ultant
mortar, obtained by separating the mortar portion and coarse aggregate
using a 5-mm screen, is left standing for 30 minùtes. The
quick-setting agent is added and hand-mixed for 20 seconds. The
initial time of setting (time required for penetration resistance to
reach 35 kg/cm2 according to the method of "test for time of setting
of concrete" is measured for each mortar. The time of setting is
considered here as the time (minutes and seconds) from addition of
quick-setting agent.
Test results
The test results when quick-setting agent F is used, are as given
in Table 2, and the test results when quick-setting agent G is used,
are as given in Table 3.
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Table 2
Time of setting Measurement Results (Quick-setting Agent F)
Test No. Example No. Time of Setting
Initial (min-sec)
1 1 13 min 40 sec
2 I more than 20 min
3 II more than 20 min
4 III more than 20 min
IV more than 20 min
6 V 17 min 20 sec
Table 3
Time of Setting Measurement Results (Quick-Setting Agent G)
Test No. Example No. Time of Setting
Initial (min-sec)
7 2 less than 1 min
8 VI 3 min 30 sec
9 VII 4 min 20 sec
VIII more than 20 min
11 IX 4 min
12 X 3 min 10 sec
Where the quick setting agent used is P, the mortar made in the
absence of any admixture A to ~ or with any of the other comparative
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admixtures B to E, does not reach the initial set within 17 minutes,
but by using the polycarboxylate admixture (A), initial set is reached
in 13 minutes and 40 seconds.
Where the quick-setting agent used is G, and the
polycarboxylate admixture (A), the initial set is reached within 1
minute, whereas none of the other comparative tests show an initial
set under 3 minutes. This illustrates that time of setting is greatly
shortened using Admixture A rather than Admixtures B to E with the
same quick-setting agent
The extent to which the fluidity of concrete (prior to addition of
quick-setting) is maintained, is shown.
The materials used in the tests and the mix proportions of
concrete are the same as those given in Table 1 for Example 1 and
comparative Examples I, IV and V. Further, the admixtures used in -~
these tests are the polycarboxylate admixture (A), the
sulfonated-naphthalene formaldehyde condensate admixture (D) and the
sulfonated ol ~ ine formaldehyde condensate admixture (E).
After mixing the cement, water, aggregate and admixtures with a
tilting mixer, all of the concrete is discharged and slump is
measured. The concrete is returned to the mixer, and whilst continuing
to rotate the mixer at lo~ speed (2 rpm) for the required length of
time. The slumps are measured after 30 minutes and 60 minutes.
Te~t Reault~
The test results are given in Table 4.
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Table 4
Concrete Slump Loss Test Results
Test No. Example No. Admixture Slump (cm)
(Table 1) Type Dosage Imme- After After
diate 30 min 60 min
13 1 A 0.12 13.5 10.0 8.5
14 I - - 14.0 9.0 7.5
IV D 0.45 13.5 8.0 6.0
16 V E 0.50 14.0 6.5 5.0
It can be seen from Table 4 that the slump of the concrete
using the polycarboxylate admixture A is not reduced compared with
others even after a long period of time has elapsed. In the
comparative Example using the admixture E, it can be seen that the
time of setting is comparatively fast, but the time-dependent change
in slump is great (reaching less than 5 cm after 60 minutes).
3700/DM/HC
