CA2207915C - Low-heat high-performance concrete - Google Patents
Low-heat high-performance concrete Download PDFInfo
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- CA2207915C CA2207915C CA 2207915 CA2207915A CA2207915C CA 2207915 C CA2207915 C CA 2207915C CA 2207915 CA2207915 CA 2207915 CA 2207915 A CA2207915 A CA 2207915A CA 2207915 C CA2207915 C CA 2207915C
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- lhhpc
- silica
- portland cement
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
- C04B28/04—Portland cements
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
- C04B2103/0068—Ingredients with a function or property not provided for elsewhere in C04B2103/00
- C04B2103/0089—Agents for reducing heat of hydration
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00034—Physico-chemical characteristics of the mixtures
- C04B2111/00068—Mortar or concrete mixtures with an unusual water/cement ratio
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
Abstract
A Low-Heat High-Performance Concrete (LHHPC) composition having a very low cement content and high W/CM ratio offers high strengths, low heat of hydration, excellent volumetric stability, low chloride permeability and low pH. To reduce the cement content while maintaining high performance, silica fume and silica flour are used in large quantities. The LHHPC composition ca n be used for high mass concrete structures and other applications which requi re low heats of hydration yet offers compressive strength comparable to Standar d High Performance Cement (SHPC).
Description
CA 0220791~ 1997-06-16 W Q961~4564 PCT/CA9~100716 LOW-HEAT HIGH-PERFORMANCE CONCRETE
BACKGROUND OF THE INVENTION
This invention relates to a new low-heat, high-performance concrete.
Many engineering applications require high performance concrete having high strength and hardness and low permeability to air and water. Standard High Performance Concrete ("SHPC") exhibits such qualities having a 28 day unconfined compressive strengths (~c) of 70 MPa or more.
SHPC relies on high Portland cement content in the range of 450-550 kg/m3 (or about 20% by weight) to achieve high strength.
Por~land cement is an unhydrated mixture of oxides and sesqui-oxides of compounds of calcium, silicon and aluminum combined with trace elements and compounds. The four major compounds in Portland cement are C3S, C2S, C3A and C4AF where C is CaO, S is SiO2, A is Al2O3 and F is Fe2O3. The silicates C3S and C2S are generally ascribed as the compounds from which materials such as concretes, mortars and grouts, that are formed when the cemPnt is hydrated, derive their desirable mechanical and engineering properties. When hydrated, the 20 silicates form C-S-H (tobermorite) gels and CH (portlandite), where H is H20.
The hydration of cement produces an exothermic chemical reaction. The main generation of heat, which is initially retarded by gypsum in the mixture, begins at about 12 hours after mixing with CA 0220791~ 1997-06-16 water, reaches a maximum rate between about 24 and 48 hours after mixing, and then begins to decrease. Empirical relationships indicate that, when perfectly insulated against heat loss, for each 100 kg of cement per cubic meter of concrete, the heat of hydration will increase 5 the temperature of the concrete by between about 8 and 12~C.
As the heat produced in concrete is proportional to the cement content, SHPC which relies on high cement content undergoes considerable heating during curing. As a result, SHPC is generally unsuitable for mass concrete structures. During hydration of mass 10 concrete structures, the rate of heat generation far exceeds the rate of dissipation to the surroundings producing a non-linear temperature distribution across the structure. This induces tensile stresses which can cause surface cracking. In addition, the volume change associated with the temperature change as the heat is dissipated also induces 15 tensile stresses leading to continuous splitting cracks.
High rates and quantities of heat generation in mass structures also leads to lower final strength. The lower final strength of concrete cured at a high temperature has been attributed to accelerated hydration which results in non-uniformly distributed C-S-H hydration 20 products formed closely around the cement particles, and to internal stresses and microcracking.
Some of the effects of high rates and quantities of heat generation can be mitigated by special procedures such as the use of cooled water and aggregates, the inclusion of ice during the preparation 25 of the concrete, and liquid nitrogen cooling of the fresh concrete.
These procedures increase costs and can produce technically -CA 0220791~ 1997-06-16 un~1esirable results.
It is known to substitute silica fume for a portion of the Portland cement in order to reduce the heat of hydration and enhance the properties of SHPC. Silica fume, a waste product from the ferro-silicon 5 manufacturing process, consists of amorphous silicates with a mean equivalent spherical diameter of about 0.25 ~un. Silica fume reacts with the CH liberated during the hydration of Portland rPment to form C-S-H. The total heat released by this pozzolanic reaction is double that released during the hydration of Portland cement. However, the 10 pozzolanic reaction proceeds at a slower rate than the cement hydration reaction and as a result, the heat from the pozzolanic reaction does not build up in, and increase the temperature of, the concrete as much as the heat of hydration from the more rapid cPmPnt hydration reaction.
While reduced heat build-up and enhanced properties can be realized by the addition of silica fume, high addition levels of 30% by dry mass replacement of cement are reported by Malhotra et al. in Condensed Silica Fume in Concrete, 1987, CRC Press, Inc. to cause increased shrinkage. Accordingly, silica fume addition levels are 20 generally restricted to between 10 and 15%.
It is also known to add quantities of inert fillers to mixtures of Portland cement and silica fume to increase the strength of the mixture. In United States Patent Nos. 4,482,385, 4,505,753 and 4,780,141, cementitious compositions are disclosed which contain Portland 25 cement, silica fume and other ingredients including fine aggregate, preferably a crystalline silica having a particle size below 5 microns.
CA 0220791~ 1997-06-16 Although these compositions contain substantial quantities of silica fume and inert filler, they rely primarily on the conventional understanding that high strength and enhanced properties are achieved through low water to cement ("W/C") and low water to 5 cementitious materials ("W/CM") ratios. In particular, the W/C ratios in the plefelred compositions of the '385, '753 and '141 patents are 0.24, 0.24 and 0.25 respectively and the W/CM ratios are 0.27, 0.27 and 0.28 respectively. Furthermore, the cement to silica ratios of these compositions are about 1: 0.~2, 1: 0.63 and 1: 0.60. Such proportions of 10 cement can be expected to produce substantial heats of hydration approaching that of conventional Portland cement based concretes.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a cPrnentitious composition having low-heat generation, high volumetric stability 15 and high-performance, suitable for use in high mass structures. The low-heat high-performance concrete (LHHPC) of the present invention is characterized by a low cement content and a high water/cementitious materials ratio. To maintain sufficient cementitious materials in the composition for high strength, a large 20 quantity of pozzolanic silica is used. It has been found that the endogenous shrinkage associated with high addition levels of pozzolanic silica to high W/CM compositions can be substantially ~limin~ted by the addition of large quantities of inert mineral flour fillers.
Thus, in accordance with one aspect of the present invention, there is provided a cementitious composition comprising:
-a. Portland cPm~nt;
b. pozzolanic silica;
c. inert mineral flour;
d. aggregate;
e. superplasticizer f. water;
wherein the amount of Portland cement in the composition is in the range of 3% to 10%, the ratio of Portland cement to pozzolanic silica is between 1:0.8 and 1:1.2, the ratio of Portland cement to inert mineral flour is between 1:1.6 and 1:2.4 and the W/CM ratio of the composition is in the range of 0.40-0.55. The ~rer~lled pozzolanic silica is condensed silica fume. The ~refe~.ed inert mineral flour is silica flour having a particle size below about 50 microns.
The above and other objects, features and advantages of the 15 present invention will become apparent from the following description taken with the accompanying drawings.
BRIEF DESCRIPrION OF THE DRAWINGS
FIG. 1 is a graphical representation of the temperature of the LHHPC composition of the present invention as a function of time 20 after casting.
FIG. 2 is a graphical representation of the temperature of a SHPC
composition as a function of time after casting.
FIG. 3 is a graphical representation of the compressive strength of the LHHPC composition of the present invention as a function of CA 0220791~ 1997-06-16 W O 96124564 PC~rlCA95/00716 time after casting.
FIG. 4 is a graphical representation of the compressive strength of an SHPC composition as a funcfiQn of time after casting.
FIG. 5 is a graphical representation of the linear variation of the LHHPC composition of the present invention under water and air as a function of time after casting.
FIG. 6 is a graphical representation of the linear variation of an SHPC composition under water and air as a function of time after casting.
FIG. 7 is a graphical representation of the pH of the LHHPC
composition of the present invention and an SHPC composition as a function of time after casting.
FIG. 8 is a graphical representation of the compressive strength of the LHHPC composition of the present invention as a function of time after casting for a mass structure, cylinders cast in situ and laboratory specimens.
DESCRIPTION OF PREFERRED EMBODIMENTS
The invention is a composite material comprising a mixture of (a) Portland cement; (b) pozzolanic silica; (c) non-pozzolanic mineral flour filler; (d) aggregate; (e) superplasticizer and (f) water.
CA 0220791~ 1997-06-16 (a) Portland Cement While any of the commercially available grades of Portland cement can be used in the presen~ invention, Type V (U.S.)/Type 50 (~n~ ) cement is preferred. In order to achieve the low heat 5 characteristics of the present invention, the amount of Portland cement in the composition should be in the range of about 3 to 10% by weight of the composition, with a range of about 3.5 to 4.5% being ererl ~d.
(b) Pozzolanic Silica The pozzolanic silica used in the present invention is an amorphous, non-crystalline silicon dioxide, preferably condensed silica fume. Silica fume is a waste product from the ferro-silicon manufacturing process and has a mean particle diameter of about 0.25 ~ILm. The pozzolanic silica reacts with the CH liberated during the hydration reaction of Portland cement to form new C-S-H. The amount of pozzolanic silica should be such that the ratio of Portland c~Pnt to pozzolanic silica is in the range of about 1:0.8 to 1:1.2, with a ratio of 1:1 being ~refe~led.
(c) Non-pozzolanic Mineral Flour Filler The non-pozzolanic mineral flour filler used in the present invention includes flours such as quartz, ilmenite or iron oxide having an equivalent spherical partide size of up to about 50 ~m. The preferred mineral flour filler is silica flour the main constituent of which is quartz (>90% by dry mass). For optimum effect, the particle size of the mineral flour should be subst~nti~lly the same as the size of the c~m~nt particles and the hydration reaction products. The amount of non-pozzolanic mineral flour should be such that the ratio of CA 0220791~ 1997-06-16 Portland cement to non-pozzolanic mineral flour is in the range of about 1:1.6 to 1: 2.4, with a ratio of 1:2 being preferred.
(d) A~gregate The aggregate used in the present invention can be that 5 conventionally used in mass structure concrete compositions and advantageously includes a mixture of sand-like fine aggregate and coarse crushed stone like aggregate having a sizes predominantly in the range of between about 75~m to 4.5 mm and 4.5 mm to 12.5 mm respectively. The amount of aggregate present should be such that the 10 proportion of Portland cement in the composition falls in the ratios referred to above.
(e) Superplasticizer (Optional) To render the composition more fluid and to improve wetting and mixing, a superplasticizer is included in the composition. A
15 suitable superplasticizer is a condensed Na salt of sulphonated formaldehyde which is widely commercially available under a variety of trade names. The amount of superplasticizer should be such that the ratio of Portland c~m~nt to superplasticizer is in the range of from 8:1 to 12:1, with a ratio of about 10:1 being preferred.
(f) Water The amount of water in the composition of the present invention should be such that the W/CM ratio is in the range of about 0.40 - 0.55, with a range of about 0.46 - 0.49 being preferred.
The properties of the composition of the present invention were compared against those of a SHPC. The components listed in Table 1 under LHHPC were mixed to form an example of the present invention. The component listed under SHPC were mixed to form an example of Standard High-Performance Concrete for comparative purposes.
Table 1 Components LHHPC (k~) SHPC (k~) Portland ~~elnent97.0 497.0 Silica Fume 97.0 49 7 Silica ~lour 193.8 0.0 Fine Aggregate 894.7 703.2 Coarse Aggregate1039.6 1101.0 Superplasticizer (dry mass)' 10.3 7.1 Water 91.9 123.9 Properties Density 2424 kg/m3 2482 kg/m3 Air Content 2.8% 1.8%
Slump 170 mm 230.0 mm In each of the LHHPC and SHPC examples in Table 1, the 20 Portland c~n~ent used was Type V (US)/Type 50 (C~na~), the silica flour was comprised of over 90% by dry mass of inert quartz particles having a particle size 5imilar to the Portland cement grains (< 4~,um), the aggregates used were a crusher run coarse granite aggregate of 4.5 to 12.5 mm size, and natural sand-sized fine aggregate with a fineness 25 modulus of 2.66 and the superplasticizer was a condensed Na salt of sulphonated naphthalene formaldehyde. The LHHPC example was compared to the SHPC example by measuring the following CA 0220791~ 1997-06-16 W 096/24564 PCTlCA9StO0716 characteristic properties: temperature rise during curing, compressive strength, tensile strength, rlim~n~ nal stability in air and water, and pH.
Temperature Rise The temperatures were measured with time at the centre of cubical specimens poured into an insulated box with a specimen volume of 0.027 m3. The results for the LHHPC and SHPC examples are shown in Figures 1 and 2, respectively. The maximum temperature reached by the LHHPC was 37~C corresponding to a temperature rise of only 15~C. This is far lower than the 65~C
temperature reached by the SHPC corresponding to a 43~C rise.
Consistent with these findings, the LHHPC releases only about one-third of the heat released by the SHPC.
Compressive Stren~th (SC2 Unconfined compressive strengths were measured on cylin(lric~l specimens (100 mm diameter, 200 mm long) in accordance with ASTM Standard C 39-86. Twenty-four hours after casting, the samples were stripped from their moulds and immersed in saturated lime-water to cure for predefined periods. The results for the LHHPC
and SHPC examples are shown in Figures 4 and 5, respectively. The results show that the LHHPC gains strength initially more slowly than the SHPC but with time, the rate of strength development increases and the curves being to merge. High performance concrete are defined by a minimum 28 day ~c of 70 MPa. The 28 day compressive strength of the LHHPC example (c~c = 87 MPa) qll~lifies the LHHPC material of the present invention to be classified as high-performance concrete. The c~c of the LHHPC continues to increase with time after 28 days to over 100 CA 0220791~ 1997-06-16 W O 96124~64 PCT/CA95/00716 ~IPa.
Tensile Strength (~T) Cylindrical spe~im~n~ (lOOx200 mm) of SHPC and LHHPC were tested in accordance with ASTM Standard C496-86. Measurements of 5 sets of 3 samples each of SHPC at 1, 3, 7, 28 and 90 days after casting were recorded and the results are presented in Table 2. Measurements of 3 sets of 3 samples each of LHHPC at 7, 28 and 90 days after casting were recorded and the results are presented in Tables 3.
Table 2 - SHPC
iO Sample Age Load Stress Len~th Mass Density (days) (kN)(MPa) (~m~ ~ (g/cc) 143.34.4 204.0 4085.3 2.50 2 1 152.84.7 204.5 4116.7 2.51 3 1 150.34.6 204.0 4088.0 2.50 4 3 179.85.6 204.0 4113. 2.52 3 156.04.8 204.5 4102.1 2.50 6 3 179.25.5 204.5 4108.0 2.51 7 7 169.55.3 203.0 4085.5 2.51 8 7 188.75.8 204.5 4111.0 2.51 9 7 172.65.3 204.5 4122.7 2.52 28 193.56.0 204.0 4108.6 2.51 11 28 195.76.0 203.5 4119.8 2.53 12 28 188.45.8 205.0 4152.0 2.53 13 90 210.06.5 204.0 4104.2 2.51 14 90 202.36.2 204.5 4124.9 2.52 1 5 90 212.36.5 204.5 4126.4 2.52 CA 022079l~ l997-06-l6 Table 3 - LHHPC
~nple Aye Load Stress Len~h Mass Densi (days) ~ (MPa) (m~ ~p~ (g/ ~ 4 7 7 120.2 3.7 205.0 4025.2 2.45 8 7 120.3 3.7 204.0 4021.0 2.46 9 7 126.9 3.9 204.0 4026.9 2.46 28 185.8 5.7 206.0 4066.1 2.46 11 28 195.7 6.0 204.0 4007.3 2.45 12 28 201.5 6.2 204.0 4009.6 2.45 13 90 212.5 6.6 204.5 4041.8 2.47 14 90 239.3 7.4 204.5 4033.9 2.46 212.9 6.6 204.0 4032.1 2.47 The test results in Tables 2 and 3 show that the LHHPC at an early age (7 days) has tensile strength lower than the SHPC but after 28 days about equals SHPC and after 90 days exceeds SHPC.
Volumetric Stability (shrinkage and expansion) The linear shrinkage and expansion of beam specimens tlOOx100x300) of SHPC and LHHPC were measured with time in accordance with ASTM Standard C341-84. Spe-imen~ were cured for 1,7 and 28 days under water at 23~C after which they were dried in air ' on the laboratory bench for various periods and the linear drying shrinkage was measured. For comparison, the changes in length of specimens that were continuously cured under water were measured and the results for LHHPC and SHPC are shown in Figures 5 and 6, respectively. As is evident from Figures 5 and 6, drying shrinkage of the LHHPC decreases with increasing immersed curing time. Cured under water for less than 7 days, the LHHPC shrinks more than SHPC.
CA 0220791~ 1997-06-16 However, with longer curing periods, the linear drying shrinkage of the LHHPC is significantly less than that of the SHPC. Cured continuously under water, the LHHPC expands and the SHPC
contracts.
BACKGROUND OF THE INVENTION
This invention relates to a new low-heat, high-performance concrete.
Many engineering applications require high performance concrete having high strength and hardness and low permeability to air and water. Standard High Performance Concrete ("SHPC") exhibits such qualities having a 28 day unconfined compressive strengths (~c) of 70 MPa or more.
SHPC relies on high Portland cement content in the range of 450-550 kg/m3 (or about 20% by weight) to achieve high strength.
Por~land cement is an unhydrated mixture of oxides and sesqui-oxides of compounds of calcium, silicon and aluminum combined with trace elements and compounds. The four major compounds in Portland cement are C3S, C2S, C3A and C4AF where C is CaO, S is SiO2, A is Al2O3 and F is Fe2O3. The silicates C3S and C2S are generally ascribed as the compounds from which materials such as concretes, mortars and grouts, that are formed when the cemPnt is hydrated, derive their desirable mechanical and engineering properties. When hydrated, the 20 silicates form C-S-H (tobermorite) gels and CH (portlandite), where H is H20.
The hydration of cement produces an exothermic chemical reaction. The main generation of heat, which is initially retarded by gypsum in the mixture, begins at about 12 hours after mixing with CA 0220791~ 1997-06-16 water, reaches a maximum rate between about 24 and 48 hours after mixing, and then begins to decrease. Empirical relationships indicate that, when perfectly insulated against heat loss, for each 100 kg of cement per cubic meter of concrete, the heat of hydration will increase 5 the temperature of the concrete by between about 8 and 12~C.
As the heat produced in concrete is proportional to the cement content, SHPC which relies on high cement content undergoes considerable heating during curing. As a result, SHPC is generally unsuitable for mass concrete structures. During hydration of mass 10 concrete structures, the rate of heat generation far exceeds the rate of dissipation to the surroundings producing a non-linear temperature distribution across the structure. This induces tensile stresses which can cause surface cracking. In addition, the volume change associated with the temperature change as the heat is dissipated also induces 15 tensile stresses leading to continuous splitting cracks.
High rates and quantities of heat generation in mass structures also leads to lower final strength. The lower final strength of concrete cured at a high temperature has been attributed to accelerated hydration which results in non-uniformly distributed C-S-H hydration 20 products formed closely around the cement particles, and to internal stresses and microcracking.
Some of the effects of high rates and quantities of heat generation can be mitigated by special procedures such as the use of cooled water and aggregates, the inclusion of ice during the preparation 25 of the concrete, and liquid nitrogen cooling of the fresh concrete.
These procedures increase costs and can produce technically -CA 0220791~ 1997-06-16 un~1esirable results.
It is known to substitute silica fume for a portion of the Portland cement in order to reduce the heat of hydration and enhance the properties of SHPC. Silica fume, a waste product from the ferro-silicon 5 manufacturing process, consists of amorphous silicates with a mean equivalent spherical diameter of about 0.25 ~un. Silica fume reacts with the CH liberated during the hydration of Portland rPment to form C-S-H. The total heat released by this pozzolanic reaction is double that released during the hydration of Portland cement. However, the 10 pozzolanic reaction proceeds at a slower rate than the cement hydration reaction and as a result, the heat from the pozzolanic reaction does not build up in, and increase the temperature of, the concrete as much as the heat of hydration from the more rapid cPmPnt hydration reaction.
While reduced heat build-up and enhanced properties can be realized by the addition of silica fume, high addition levels of 30% by dry mass replacement of cement are reported by Malhotra et al. in Condensed Silica Fume in Concrete, 1987, CRC Press, Inc. to cause increased shrinkage. Accordingly, silica fume addition levels are 20 generally restricted to between 10 and 15%.
It is also known to add quantities of inert fillers to mixtures of Portland cement and silica fume to increase the strength of the mixture. In United States Patent Nos. 4,482,385, 4,505,753 and 4,780,141, cementitious compositions are disclosed which contain Portland 25 cement, silica fume and other ingredients including fine aggregate, preferably a crystalline silica having a particle size below 5 microns.
CA 0220791~ 1997-06-16 Although these compositions contain substantial quantities of silica fume and inert filler, they rely primarily on the conventional understanding that high strength and enhanced properties are achieved through low water to cement ("W/C") and low water to 5 cementitious materials ("W/CM") ratios. In particular, the W/C ratios in the plefelred compositions of the '385, '753 and '141 patents are 0.24, 0.24 and 0.25 respectively and the W/CM ratios are 0.27, 0.27 and 0.28 respectively. Furthermore, the cement to silica ratios of these compositions are about 1: 0.~2, 1: 0.63 and 1: 0.60. Such proportions of 10 cement can be expected to produce substantial heats of hydration approaching that of conventional Portland cement based concretes.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a cPrnentitious composition having low-heat generation, high volumetric stability 15 and high-performance, suitable for use in high mass structures. The low-heat high-performance concrete (LHHPC) of the present invention is characterized by a low cement content and a high water/cementitious materials ratio. To maintain sufficient cementitious materials in the composition for high strength, a large 20 quantity of pozzolanic silica is used. It has been found that the endogenous shrinkage associated with high addition levels of pozzolanic silica to high W/CM compositions can be substantially ~limin~ted by the addition of large quantities of inert mineral flour fillers.
Thus, in accordance with one aspect of the present invention, there is provided a cementitious composition comprising:
-a. Portland cPm~nt;
b. pozzolanic silica;
c. inert mineral flour;
d. aggregate;
e. superplasticizer f. water;
wherein the amount of Portland cement in the composition is in the range of 3% to 10%, the ratio of Portland cement to pozzolanic silica is between 1:0.8 and 1:1.2, the ratio of Portland cement to inert mineral flour is between 1:1.6 and 1:2.4 and the W/CM ratio of the composition is in the range of 0.40-0.55. The ~rer~lled pozzolanic silica is condensed silica fume. The ~refe~.ed inert mineral flour is silica flour having a particle size below about 50 microns.
The above and other objects, features and advantages of the 15 present invention will become apparent from the following description taken with the accompanying drawings.
BRIEF DESCRIPrION OF THE DRAWINGS
FIG. 1 is a graphical representation of the temperature of the LHHPC composition of the present invention as a function of time 20 after casting.
FIG. 2 is a graphical representation of the temperature of a SHPC
composition as a function of time after casting.
FIG. 3 is a graphical representation of the compressive strength of the LHHPC composition of the present invention as a function of CA 0220791~ 1997-06-16 W O 96124564 PC~rlCA95/00716 time after casting.
FIG. 4 is a graphical representation of the compressive strength of an SHPC composition as a funcfiQn of time after casting.
FIG. 5 is a graphical representation of the linear variation of the LHHPC composition of the present invention under water and air as a function of time after casting.
FIG. 6 is a graphical representation of the linear variation of an SHPC composition under water and air as a function of time after casting.
FIG. 7 is a graphical representation of the pH of the LHHPC
composition of the present invention and an SHPC composition as a function of time after casting.
FIG. 8 is a graphical representation of the compressive strength of the LHHPC composition of the present invention as a function of time after casting for a mass structure, cylinders cast in situ and laboratory specimens.
DESCRIPTION OF PREFERRED EMBODIMENTS
The invention is a composite material comprising a mixture of (a) Portland cement; (b) pozzolanic silica; (c) non-pozzolanic mineral flour filler; (d) aggregate; (e) superplasticizer and (f) water.
CA 0220791~ 1997-06-16 (a) Portland Cement While any of the commercially available grades of Portland cement can be used in the presen~ invention, Type V (U.S.)/Type 50 (~n~ ) cement is preferred. In order to achieve the low heat 5 characteristics of the present invention, the amount of Portland cement in the composition should be in the range of about 3 to 10% by weight of the composition, with a range of about 3.5 to 4.5% being ererl ~d.
(b) Pozzolanic Silica The pozzolanic silica used in the present invention is an amorphous, non-crystalline silicon dioxide, preferably condensed silica fume. Silica fume is a waste product from the ferro-silicon manufacturing process and has a mean particle diameter of about 0.25 ~ILm. The pozzolanic silica reacts with the CH liberated during the hydration reaction of Portland cement to form new C-S-H. The amount of pozzolanic silica should be such that the ratio of Portland c~Pnt to pozzolanic silica is in the range of about 1:0.8 to 1:1.2, with a ratio of 1:1 being ~refe~led.
(c) Non-pozzolanic Mineral Flour Filler The non-pozzolanic mineral flour filler used in the present invention includes flours such as quartz, ilmenite or iron oxide having an equivalent spherical partide size of up to about 50 ~m. The preferred mineral flour filler is silica flour the main constituent of which is quartz (>90% by dry mass). For optimum effect, the particle size of the mineral flour should be subst~nti~lly the same as the size of the c~m~nt particles and the hydration reaction products. The amount of non-pozzolanic mineral flour should be such that the ratio of CA 0220791~ 1997-06-16 Portland cement to non-pozzolanic mineral flour is in the range of about 1:1.6 to 1: 2.4, with a ratio of 1:2 being preferred.
(d) A~gregate The aggregate used in the present invention can be that 5 conventionally used in mass structure concrete compositions and advantageously includes a mixture of sand-like fine aggregate and coarse crushed stone like aggregate having a sizes predominantly in the range of between about 75~m to 4.5 mm and 4.5 mm to 12.5 mm respectively. The amount of aggregate present should be such that the 10 proportion of Portland cement in the composition falls in the ratios referred to above.
(e) Superplasticizer (Optional) To render the composition more fluid and to improve wetting and mixing, a superplasticizer is included in the composition. A
15 suitable superplasticizer is a condensed Na salt of sulphonated formaldehyde which is widely commercially available under a variety of trade names. The amount of superplasticizer should be such that the ratio of Portland c~m~nt to superplasticizer is in the range of from 8:1 to 12:1, with a ratio of about 10:1 being preferred.
(f) Water The amount of water in the composition of the present invention should be such that the W/CM ratio is in the range of about 0.40 - 0.55, with a range of about 0.46 - 0.49 being preferred.
The properties of the composition of the present invention were compared against those of a SHPC. The components listed in Table 1 under LHHPC were mixed to form an example of the present invention. The component listed under SHPC were mixed to form an example of Standard High-Performance Concrete for comparative purposes.
Table 1 Components LHHPC (k~) SHPC (k~) Portland ~~elnent97.0 497.0 Silica Fume 97.0 49 7 Silica ~lour 193.8 0.0 Fine Aggregate 894.7 703.2 Coarse Aggregate1039.6 1101.0 Superplasticizer (dry mass)' 10.3 7.1 Water 91.9 123.9 Properties Density 2424 kg/m3 2482 kg/m3 Air Content 2.8% 1.8%
Slump 170 mm 230.0 mm In each of the LHHPC and SHPC examples in Table 1, the 20 Portland c~n~ent used was Type V (US)/Type 50 (C~na~), the silica flour was comprised of over 90% by dry mass of inert quartz particles having a particle size 5imilar to the Portland cement grains (< 4~,um), the aggregates used were a crusher run coarse granite aggregate of 4.5 to 12.5 mm size, and natural sand-sized fine aggregate with a fineness 25 modulus of 2.66 and the superplasticizer was a condensed Na salt of sulphonated naphthalene formaldehyde. The LHHPC example was compared to the SHPC example by measuring the following CA 0220791~ 1997-06-16 W 096/24564 PCTlCA9StO0716 characteristic properties: temperature rise during curing, compressive strength, tensile strength, rlim~n~ nal stability in air and water, and pH.
Temperature Rise The temperatures were measured with time at the centre of cubical specimens poured into an insulated box with a specimen volume of 0.027 m3. The results for the LHHPC and SHPC examples are shown in Figures 1 and 2, respectively. The maximum temperature reached by the LHHPC was 37~C corresponding to a temperature rise of only 15~C. This is far lower than the 65~C
temperature reached by the SHPC corresponding to a 43~C rise.
Consistent with these findings, the LHHPC releases only about one-third of the heat released by the SHPC.
Compressive Stren~th (SC2 Unconfined compressive strengths were measured on cylin(lric~l specimens (100 mm diameter, 200 mm long) in accordance with ASTM Standard C 39-86. Twenty-four hours after casting, the samples were stripped from their moulds and immersed in saturated lime-water to cure for predefined periods. The results for the LHHPC
and SHPC examples are shown in Figures 4 and 5, respectively. The results show that the LHHPC gains strength initially more slowly than the SHPC but with time, the rate of strength development increases and the curves being to merge. High performance concrete are defined by a minimum 28 day ~c of 70 MPa. The 28 day compressive strength of the LHHPC example (c~c = 87 MPa) qll~lifies the LHHPC material of the present invention to be classified as high-performance concrete. The c~c of the LHHPC continues to increase with time after 28 days to over 100 CA 0220791~ 1997-06-16 W O 96124~64 PCT/CA95/00716 ~IPa.
Tensile Strength (~T) Cylindrical spe~im~n~ (lOOx200 mm) of SHPC and LHHPC were tested in accordance with ASTM Standard C496-86. Measurements of 5 sets of 3 samples each of SHPC at 1, 3, 7, 28 and 90 days after casting were recorded and the results are presented in Table 2. Measurements of 3 sets of 3 samples each of LHHPC at 7, 28 and 90 days after casting were recorded and the results are presented in Tables 3.
Table 2 - SHPC
iO Sample Age Load Stress Len~th Mass Density (days) (kN)(MPa) (~m~ ~ (g/cc) 143.34.4 204.0 4085.3 2.50 2 1 152.84.7 204.5 4116.7 2.51 3 1 150.34.6 204.0 4088.0 2.50 4 3 179.85.6 204.0 4113. 2.52 3 156.04.8 204.5 4102.1 2.50 6 3 179.25.5 204.5 4108.0 2.51 7 7 169.55.3 203.0 4085.5 2.51 8 7 188.75.8 204.5 4111.0 2.51 9 7 172.65.3 204.5 4122.7 2.52 28 193.56.0 204.0 4108.6 2.51 11 28 195.76.0 203.5 4119.8 2.53 12 28 188.45.8 205.0 4152.0 2.53 13 90 210.06.5 204.0 4104.2 2.51 14 90 202.36.2 204.5 4124.9 2.52 1 5 90 212.36.5 204.5 4126.4 2.52 CA 022079l~ l997-06-l6 Table 3 - LHHPC
~nple Aye Load Stress Len~h Mass Densi (days) ~ (MPa) (m~ ~p~ (g/ ~ 4 7 7 120.2 3.7 205.0 4025.2 2.45 8 7 120.3 3.7 204.0 4021.0 2.46 9 7 126.9 3.9 204.0 4026.9 2.46 28 185.8 5.7 206.0 4066.1 2.46 11 28 195.7 6.0 204.0 4007.3 2.45 12 28 201.5 6.2 204.0 4009.6 2.45 13 90 212.5 6.6 204.5 4041.8 2.47 14 90 239.3 7.4 204.5 4033.9 2.46 212.9 6.6 204.0 4032.1 2.47 The test results in Tables 2 and 3 show that the LHHPC at an early age (7 days) has tensile strength lower than the SHPC but after 28 days about equals SHPC and after 90 days exceeds SHPC.
Volumetric Stability (shrinkage and expansion) The linear shrinkage and expansion of beam specimens tlOOx100x300) of SHPC and LHHPC were measured with time in accordance with ASTM Standard C341-84. Spe-imen~ were cured for 1,7 and 28 days under water at 23~C after which they were dried in air ' on the laboratory bench for various periods and the linear drying shrinkage was measured. For comparison, the changes in length of specimens that were continuously cured under water were measured and the results for LHHPC and SHPC are shown in Figures 5 and 6, respectively. As is evident from Figures 5 and 6, drying shrinkage of the LHHPC decreases with increasing immersed curing time. Cured under water for less than 7 days, the LHHPC shrinks more than SHPC.
CA 0220791~ 1997-06-16 However, with longer curing periods, the linear drying shrinkage of the LHHPC is significantly less than that of the SHPC. Cured continuously under water, the LHHPC expands and the SHPC
contracts.
5 ~
The pH of mixtures of equal masses of simulated saline groundwater (500g) such as that found in the Canadian Shield and granulated mortars (500g) of LHHPC and SHPC that had been cured under water for 28 days after casting were measured over time using a 10 Beckman pH meter equipped with an Ag-AgCl electrode. The results for S~IPC and LHHPC are presented in Figure 7 and show that after 6 months, the pH of the LHHPC and the SHPC mixtures are virtually stable at 9.65 and 12.30 respectively.
Without wishing to be bound by any particular theory, it is likely 15 that the relatively low pH of the LHHPC is associated with greater degrees of completion of the pozzolanic reaction than in the SHPC.
Moreover, the high content of unreacted silica fume in the LHHPC
tends to buffer the system. The amorphous morphology of silica fume is unstable at high pH and reacts with OH- released from the concrete 20 and thus reduces the pH of solution. Low pH in the concrete tends to minimi7e alkali aggregate reactions which commonly contribute to deterioration of concrete. Conversely, the high pH of normal concrete and SHPC is commonly perceived to benefit reinforced and prestressed concrete structures insofar as the surfaces of steel imbedded in the 25 concrete becomes coated with a passivating layer that limits the rate of corrosion processes. Chloride diffusion tests carried out in accordance CA 0220791~ 1997-06-16 W 096t2456~ PCT/CA95/00716 with AASHO Standard procedures appear to indicate that the LHHPC
does not allow for tr~n~mi~sion of Cl- Chloride ions are generally considered to be the prime agent promoting the corrosion of steel in concrete structures. Accordingly, it is believed that steel in LHHPC will 5 corrode as, if not more, slowly as it corrodes in SHPC.
The compressive strength, tensile strength and volumetric stability tests all show that LHHPC is less mechanically stable than SHPC at early curing periods. However, with time the performance properties of the LHHPC tends to equal or, in the case of volumetric 10 stability, exceed those of SHPC. The delayed development of these me~h~nical qualities is consistent with the increased super plasticizer content of the LHHPC. Superplasticizers act as retarders, delaying the initiation and the rate of progress of the hydration reactions.
Increasing the superplasticizer content in concrete increases the 15 retarding effect. The LHHPC and SHPC formulations of Table 1 have superplasticizer contents of 10 kg/m3 and 7.0 kg/m3 respectively. With significantly lower cement and cementitious materials contents, the LHHPC has much higher ratios of superplasticizer to cement or cementitious materials (by dry mass) than the SHPC. It has been 20 shown that superplasticizers function by reacting with the cement during hydration to eventually become integrated with the hydration reaction products. It is believed that with the higher superplasticizer to cement ratios, the reactions between the superplasticizer and the cement are more extensive and prolonged in the LHHPC.
The suitability of the LHHPC compositions of the present invention for use in large-scale engineering application is demonstrated by the following test. Nine (9) cubic meters of the CA 0220791~ 1997-06-16 W O g612456~ PCT/CA95100716 LHHPC were mixed and used to build a dam 420 metres underground where the ambient temperature is 15~C. During curing, the temperature at the centre of the dam rose to 24~C. This 9~C rise was less than the value measured in the laboratory and recorded in Figure 5 1. Cores were recovered from the dam and unconfined compressive strength tests were carried out on the recovered cores and on in situ sperim~n~ for purposes of comparison. The in situ specimens were cylinders of LHHPC cast during the in situ work and cured at either 15~c or 25~C. The test results are shown in Figure 8. For comparison 10 purposes, Figure 8 also includes the tests result on laboratory sperim~n~ taken from Pigure 3.
As is evident from the results in Figure 8, the strengths of the cylinders cast in si~u and cured at 25~C are substantially the same as those obtained from laboratory prepared specimens. The strengths of 15 both ~e in situ cylinders and cores are less than ~ose of the laboratory specimens. Largely, a slower rate of hydration at the lower ambient underground temperature is considered to account for both the smaller temperature rise and the slower rate of gain of strength of the in situ placed material.
The performance of the LHHPC compositions of the present invention is surprising in light of the conventional view that enhanced properties of mortars and concrete are achieved by decreasing the water to cPrnent ratio of the composition. Precisely why the LHHPC of the present invention has such enhanced properties with very high W/C and W/CM ratios and very low cement quantities is not completely understood. The following is offered by way of possible explanation, but is not to be construed as limiting the CA 0220791~ 1997-06-16 invention in any way. For the SHPC and the LHHPC compositions of Table 1, the W/CM ratios are 0.23 and 0.47 respectively and the W/C
ratios are 0.26 and 0.94 respectively. The effects of the higher ratios in the LHHPC are clearly reflected in the results from the drying 5 ~hrink~ge tests. At early ages with the lower degrees of hydration and maturity of the LHHPC paste, there is more free mobile water than in the SHPC paste. This water evaporates from the surfaces and the ~y~Lelll responds by contracting. It is believed that at these early ages, the bonding hydrates are not sufficiently well developed to resist the 10 associated internally generated stresses in the concrete. The high content of inert filler and aggregates in the system leaves much less pore space in the LHHPC than in the SHPC for the hydration and pozzolanic reaction products to fill. It can be reasonably inferred from the strength and volume change results that, with increased curing 15 time, the low cement content used in the LHHPC is sufficient to fill the pores and the reaction products become well bonded to the filler and aggregates. Moreover, insofar as the volume of the LHHPC specimens that were fully immersed in water increase with time, as do strengths, it can be suggested that, despite the high W/CM in the LHHPC, the 20 hydration and pozzolanic reactions are incomplete well beyond 90 days after casting. These changes may be associated as much with changes in the morphology of the reaction products as with increases in their quantity. Furthermore, the reaction of silica fume with the cement produces a high formation of gels of C-S-H. Such gels enrobe the 25 mineral flour and include it in a cementitious matrix that will bond advantageously with the aggregate.
The present invention permits a large quantity of cement in concrete to be replaced by a mixture of silica fume and inert flour to CA 0220791~ 1997-06-16 decrease heat production to a minim u m and avoid éndogenous shrinkage while maintaining the advantageous properties of high-performance concrete. When compared to SHPC, the LHHPC of the present invention produces si~nificAntly less heat and when hydration 5 is sufficiently advanced, has similar mechanical strength characteristics, better volumetric stability in air and under water, low chloride permeability and a lower pH. Because of its extremely low heat of hydration, the LHHPC of the present invention can be used in mass concrete structures where SHPC is unsuitable due to its high heat 10 of hydration. In addition, the low pH of the LHHPC of the present invention will stabilize the alkali-aggregate reaction perrnitting the use of aggregate unsuitable for cement compositions having higher pH
levels. The low pH and the low chloride permeability contribute to high durability of the LHHPC of the present invention in seawater or similarly saline water, which have a pH of between about 7.5 and 8.4.
The LHHPC of the present invention is suitable for high mass structures for use in the geological isolation and disposal of radioactive wastes, although it can be used to form other concrete structures that will benefit from the low heat, low pH and other characteristics of the 20 LHHPC. Although suitable for high mass structures such as dams and foundations, the LHHPC of the present invention can be used for structural ~lem.on~ such as beams, columns and slabs in which many of the adverse effects, such as cracking and increased perme~hility, that are associated with elevated temperatures and high temperature 25 gradients during curing can bè ~limin~ted. The low pH of the LHHPC
of the present invention should also make the composition more suitable than conventional concretes for application with new reinforcing and pre- and post stressing Inaterials, such as those based on silica-glass fibre technology.
W O 96t24564 PCT/CA95/00716 Because silica flour can be used in large quantities in the compositions of the present invention, and its cost is at present less than that of c~mPnt, the LHHPC of the present invention also presents comm~rcial advantages over SHPC.
The pH of mixtures of equal masses of simulated saline groundwater (500g) such as that found in the Canadian Shield and granulated mortars (500g) of LHHPC and SHPC that had been cured under water for 28 days after casting were measured over time using a 10 Beckman pH meter equipped with an Ag-AgCl electrode. The results for S~IPC and LHHPC are presented in Figure 7 and show that after 6 months, the pH of the LHHPC and the SHPC mixtures are virtually stable at 9.65 and 12.30 respectively.
Without wishing to be bound by any particular theory, it is likely 15 that the relatively low pH of the LHHPC is associated with greater degrees of completion of the pozzolanic reaction than in the SHPC.
Moreover, the high content of unreacted silica fume in the LHHPC
tends to buffer the system. The amorphous morphology of silica fume is unstable at high pH and reacts with OH- released from the concrete 20 and thus reduces the pH of solution. Low pH in the concrete tends to minimi7e alkali aggregate reactions which commonly contribute to deterioration of concrete. Conversely, the high pH of normal concrete and SHPC is commonly perceived to benefit reinforced and prestressed concrete structures insofar as the surfaces of steel imbedded in the 25 concrete becomes coated with a passivating layer that limits the rate of corrosion processes. Chloride diffusion tests carried out in accordance CA 0220791~ 1997-06-16 W 096t2456~ PCT/CA95/00716 with AASHO Standard procedures appear to indicate that the LHHPC
does not allow for tr~n~mi~sion of Cl- Chloride ions are generally considered to be the prime agent promoting the corrosion of steel in concrete structures. Accordingly, it is believed that steel in LHHPC will 5 corrode as, if not more, slowly as it corrodes in SHPC.
The compressive strength, tensile strength and volumetric stability tests all show that LHHPC is less mechanically stable than SHPC at early curing periods. However, with time the performance properties of the LHHPC tends to equal or, in the case of volumetric 10 stability, exceed those of SHPC. The delayed development of these me~h~nical qualities is consistent with the increased super plasticizer content of the LHHPC. Superplasticizers act as retarders, delaying the initiation and the rate of progress of the hydration reactions.
Increasing the superplasticizer content in concrete increases the 15 retarding effect. The LHHPC and SHPC formulations of Table 1 have superplasticizer contents of 10 kg/m3 and 7.0 kg/m3 respectively. With significantly lower cement and cementitious materials contents, the LHHPC has much higher ratios of superplasticizer to cement or cementitious materials (by dry mass) than the SHPC. It has been 20 shown that superplasticizers function by reacting with the cement during hydration to eventually become integrated with the hydration reaction products. It is believed that with the higher superplasticizer to cement ratios, the reactions between the superplasticizer and the cement are more extensive and prolonged in the LHHPC.
The suitability of the LHHPC compositions of the present invention for use in large-scale engineering application is demonstrated by the following test. Nine (9) cubic meters of the CA 0220791~ 1997-06-16 W O g612456~ PCT/CA95100716 LHHPC were mixed and used to build a dam 420 metres underground where the ambient temperature is 15~C. During curing, the temperature at the centre of the dam rose to 24~C. This 9~C rise was less than the value measured in the laboratory and recorded in Figure 5 1. Cores were recovered from the dam and unconfined compressive strength tests were carried out on the recovered cores and on in situ sperim~n~ for purposes of comparison. The in situ specimens were cylinders of LHHPC cast during the in situ work and cured at either 15~c or 25~C. The test results are shown in Figure 8. For comparison 10 purposes, Figure 8 also includes the tests result on laboratory sperim~n~ taken from Pigure 3.
As is evident from the results in Figure 8, the strengths of the cylinders cast in si~u and cured at 25~C are substantially the same as those obtained from laboratory prepared specimens. The strengths of 15 both ~e in situ cylinders and cores are less than ~ose of the laboratory specimens. Largely, a slower rate of hydration at the lower ambient underground temperature is considered to account for both the smaller temperature rise and the slower rate of gain of strength of the in situ placed material.
The performance of the LHHPC compositions of the present invention is surprising in light of the conventional view that enhanced properties of mortars and concrete are achieved by decreasing the water to cPrnent ratio of the composition. Precisely why the LHHPC of the present invention has such enhanced properties with very high W/C and W/CM ratios and very low cement quantities is not completely understood. The following is offered by way of possible explanation, but is not to be construed as limiting the CA 0220791~ 1997-06-16 invention in any way. For the SHPC and the LHHPC compositions of Table 1, the W/CM ratios are 0.23 and 0.47 respectively and the W/C
ratios are 0.26 and 0.94 respectively. The effects of the higher ratios in the LHHPC are clearly reflected in the results from the drying 5 ~hrink~ge tests. At early ages with the lower degrees of hydration and maturity of the LHHPC paste, there is more free mobile water than in the SHPC paste. This water evaporates from the surfaces and the ~y~Lelll responds by contracting. It is believed that at these early ages, the bonding hydrates are not sufficiently well developed to resist the 10 associated internally generated stresses in the concrete. The high content of inert filler and aggregates in the system leaves much less pore space in the LHHPC than in the SHPC for the hydration and pozzolanic reaction products to fill. It can be reasonably inferred from the strength and volume change results that, with increased curing 15 time, the low cement content used in the LHHPC is sufficient to fill the pores and the reaction products become well bonded to the filler and aggregates. Moreover, insofar as the volume of the LHHPC specimens that were fully immersed in water increase with time, as do strengths, it can be suggested that, despite the high W/CM in the LHHPC, the 20 hydration and pozzolanic reactions are incomplete well beyond 90 days after casting. These changes may be associated as much with changes in the morphology of the reaction products as with increases in their quantity. Furthermore, the reaction of silica fume with the cement produces a high formation of gels of C-S-H. Such gels enrobe the 25 mineral flour and include it in a cementitious matrix that will bond advantageously with the aggregate.
The present invention permits a large quantity of cement in concrete to be replaced by a mixture of silica fume and inert flour to CA 0220791~ 1997-06-16 decrease heat production to a minim u m and avoid éndogenous shrinkage while maintaining the advantageous properties of high-performance concrete. When compared to SHPC, the LHHPC of the present invention produces si~nificAntly less heat and when hydration 5 is sufficiently advanced, has similar mechanical strength characteristics, better volumetric stability in air and under water, low chloride permeability and a lower pH. Because of its extremely low heat of hydration, the LHHPC of the present invention can be used in mass concrete structures where SHPC is unsuitable due to its high heat 10 of hydration. In addition, the low pH of the LHHPC of the present invention will stabilize the alkali-aggregate reaction perrnitting the use of aggregate unsuitable for cement compositions having higher pH
levels. The low pH and the low chloride permeability contribute to high durability of the LHHPC of the present invention in seawater or similarly saline water, which have a pH of between about 7.5 and 8.4.
The LHHPC of the present invention is suitable for high mass structures for use in the geological isolation and disposal of radioactive wastes, although it can be used to form other concrete structures that will benefit from the low heat, low pH and other characteristics of the 20 LHHPC. Although suitable for high mass structures such as dams and foundations, the LHHPC of the present invention can be used for structural ~lem.on~ such as beams, columns and slabs in which many of the adverse effects, such as cracking and increased perme~hility, that are associated with elevated temperatures and high temperature 25 gradients during curing can bè ~limin~ted. The low pH of the LHHPC
of the present invention should also make the composition more suitable than conventional concretes for application with new reinforcing and pre- and post stressing Inaterials, such as those based on silica-glass fibre technology.
W O 96t24564 PCT/CA95/00716 Because silica flour can be used in large quantities in the compositions of the present invention, and its cost is at present less than that of c~mPnt, the LHHPC of the present invention also presents comm~rcial advantages over SHPC.
Claims (11)
1. A cementitious composition comprising:
a. Portland cement;
b. pozzolanic silica;
c. inert mineral flour;
d. aggregate;
e. superplasticizer;
f. water;
wherein the amount of Portland cement in the composition is in the range of 3%
to 10% by weight, the ratio of Portland cement to pozzolanic silica is between 1:0.8 by weight and 1:1.2 by weight, the ratio of Portland cement to inert mineral flour is between 1:1.6 by weight and 1:2.4 by weight and the water/cementitious materials ratio of the composition is in the range of 0.40-0.55 by weight.
a. Portland cement;
b. pozzolanic silica;
c. inert mineral flour;
d. aggregate;
e. superplasticizer;
f. water;
wherein the amount of Portland cement in the composition is in the range of 3%
to 10% by weight, the ratio of Portland cement to pozzolanic silica is between 1:0.8 by weight and 1:1.2 by weight, the ratio of Portland cement to inert mineral flour is between 1:1.6 by weight and 1:2.4 by weight and the water/cementitious materials ratio of the composition is in the range of 0.40-0.55 by weight.
2. The composition of claim 1 wherein the ratio of Portland cement to pozzolanic silica to inert mineral flour is 1:1:2 by weight.
3. The composition of claim 1 wherein the water/cementitious materials ratio of the composition is in the range of 0.46-0.49 by weight.
4. The composition of claim 1 wherein the amount of Portland cement is in the range of 3.5% to 4.5% by weight.
5. The composition of claim 1 wherein the pozzolanic silica is condensed silica fume.
6. The composition of claim 1 wherein the inert mineral flour is selected from the group consisting of silica flour, ilmenite and iron oxide having an equivalent spherical particle size of up to 50µm.
7. The composition of claim 1 wherein the inert mineral flour is silica flour.
8. The composition of claim 1 wherein the aggregate is a mixture of coarse aggregate largely in the range of 4.5 to 12.5 mm size and a fine aggregate largely in the range of between 75 µm to 4.5 mm size.
9. A cementitious composition comprising:
a. Portland cement;
b. pozzolanic silica fume;
c. non-pozzolanic silica flour;
d. aggregate;
e. superplasticizer; and f. water;
wherein the amount of Portland cement is in the range of 3.5% to 4.5% by weight of the composition, the ratio of Portland cement to silica fume is between 1:0.8 by weight and 1:1.2 by weight and the ratio of Portland cement to inert mineral flour is between 1:1.6 by weight and 1:2.4 by weight and the water/cementitious materials ratio of the composition is in the range of 0.46 to 0.49 by weight.
a. Portland cement;
b. pozzolanic silica fume;
c. non-pozzolanic silica flour;
d. aggregate;
e. superplasticizer; and f. water;
wherein the amount of Portland cement is in the range of 3.5% to 4.5% by weight of the composition, the ratio of Portland cement to silica fume is between 1:0.8 by weight and 1:1.2 by weight and the ratio of Portland cement to inert mineral flour is between 1:1.6 by weight and 1:2.4 by weight and the water/cementitious materials ratio of the composition is in the range of 0.46 to 0.49 by weight.
10. The composition of claim 9 wherein the silica flour has a particle size less than 50 microns.
11. A cementitious composition according to claim 1, wherein said composition consists essentially of, in parts by weight:
a. Portland cement 97 b. pozzolanic silica fume 97 c. non-pozzolanic silica flour 194 d. aggregate 1934 e. superplasticizer 10 f water 92.
a. Portland cement 97 b. pozzolanic silica fume 97 c. non-pozzolanic silica flour 194 d. aggregate 1934 e. superplasticizer 10 f water 92.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/384,645 US5531823A (en) | 1995-02-06 | 1995-02-06 | Low-heat high-performance concrete |
| US08/384,645 | 1995-02-06 | ||
| PCT/CA1995/000716 WO1996024564A1 (en) | 1995-02-06 | 1995-12-21 | Low-heat high-performance concrete |
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|---|---|
| CA2207915A1 CA2207915A1 (en) | 1996-08-15 |
| CA2207915C true CA2207915C (en) | 2001-12-11 |
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ID=23518152
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|---|---|---|---|
| CA 2207915 Expired - Fee Related CA2207915C (en) | 1995-02-06 | 1995-12-21 | Low-heat high-performance concrete |
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| Country | Link |
|---|---|
| US (1) | US5531823A (en) |
| AU (1) | AU4294296A (en) |
| CA (1) | CA2207915C (en) |
| WO (1) | WO1996024564A1 (en) |
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|---|---|---|---|---|
| FR2770517B1 (en) * | 1997-11-03 | 1999-12-03 | Bouygues Sa | WELL CEMENTING DAIRY, ESPECIALLY AN OIL WELL |
| US7034660B2 (en) * | 1999-02-26 | 2006-04-25 | Sri International | Sensor devices for structural health monitoring |
| US7771529B1 (en) | 2004-08-31 | 2010-08-10 | Polycor Vetrazzo, Inc. | Cementitious composition incorporating high levels of glass aggregate for producing solid surfaces |
| US7799128B2 (en) * | 2008-10-10 | 2010-09-21 | Roman Cement, Llc | High early strength pozzolan cement blends |
| US8414700B2 (en) | 2010-07-16 | 2013-04-09 | Roman Cement, Llc | Narrow PSD hydraulic cement, cement-SCM blends, and methods for making same |
| US9272953B2 (en) | 2010-11-30 | 2016-03-01 | Roman Cement, Llc | High early strength cement-SCM blends |
| MX2014003888A (en) | 2011-10-20 | 2015-02-10 | Roman Cement Llc | Particle packed cement-scm blends. |
| FR3006312B1 (en) * | 2013-06-04 | 2016-05-06 | Italcementi Spa | CEMENT MATRIX FOR SLIDING, MORTAR OR LIGHT CONCRETE, STRUCTURAL |
| CN104018619A (en) * | 2014-03-18 | 2014-09-03 | 上海罗洋新材料科技有限公司 | Ultrahigh-performance cement-based H-shaped profile |
| CN103921348B (en) * | 2014-04-30 | 2016-03-23 | 国家电网公司 | A kind of preparation method of high strength electric power cement pole |
| CN105386563A (en) * | 2015-10-28 | 2016-03-09 | 上海罗洋新材料科技有限公司 | Ultra-high performance cement-based H-shaped section bar |
| CN105421659A (en) * | 2015-10-28 | 2016-03-23 | 上海罗洋新材料科技有限公司 | Ultra-high performance cement-based groove type profile |
| CN106116344A (en) * | 2016-06-23 | 2016-11-16 | 青岛海川建设集团有限公司 | Mass concrete and preparation method thereof |
| US10131575B2 (en) | 2017-01-10 | 2018-11-20 | Roman Cement, Llc | Use of quarry fines and/or limestone powder to reduce clinker content of cementitious compositions |
| US10737980B2 (en) | 2017-01-10 | 2020-08-11 | Roman Cement, Llc | Use of mineral fines to reduce clinker content of cementitious compositions |
| US10730805B2 (en) | 2017-01-10 | 2020-08-04 | Roman Cement, Llc | Use of quarry fines and/or limestone powder to reduce clinker content of cementitious compositions |
| US11168029B2 (en) | 2017-01-10 | 2021-11-09 | Roman Cement, Llc | Use of mineral fines to reduce clinker content of cementitious compositions |
| EP3539938A1 (en) * | 2018-03-17 | 2019-09-18 | Hindustan Zinc Limited | Method for manufacturing of paver blocks and bricks from industrial waste |
| EP3581549A1 (en) * | 2018-06-15 | 2019-12-18 | Holcim Technology Ltd. | Fresh concrete composition for encasing underground electrical cables |
| CN111233400A (en) * | 2020-02-25 | 2020-06-05 | 中建西部建设湖南有限公司 | Three-level gravel-mixed low-heat cement concrete for harbor engineering |
| WO2023130182A1 (en) * | 2022-01-07 | 2023-07-13 | Universite Laval | High-strength concrete and method of producing same |
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| US2250107A (en) * | 1939-09-02 | 1941-07-22 | Detroit Edison Co | Concrete |
| US2458039A (en) * | 1945-10-05 | 1949-01-04 | Bertrand H Wait | Aggregate for improving portland cement concretes |
| US3017677A (en) * | 1959-07-20 | 1962-01-23 | Jr Herbert Greenewald | Composition and method of forming ceramic cores |
| US3753748A (en) * | 1970-06-01 | 1973-08-21 | Dow Chemical Co | Hydraulic cement retarder composition |
| IE47350B1 (en) * | 1977-09-29 | 1984-02-22 | Pilkington Brothers Ltd | Fluidised beds |
| US4256500A (en) * | 1978-04-24 | 1981-03-17 | The Partners Limited | Pozzolan cement compositions |
| US4210457A (en) * | 1978-10-12 | 1980-07-01 | W. R. Grace & Co. | Portland cement-fly ash-aggregate concretes |
| US4274881A (en) * | 1980-01-14 | 1981-06-23 | Langton Christine A | High temperature cement |
| US4442219A (en) * | 1981-10-19 | 1984-04-10 | Kennecott Corporation | Two part castable ceramic cement |
| JPS59213655A (en) * | 1983-05-14 | 1984-12-03 | 日曹マスタ−ビルダ−ス株式会社 | Mortar material |
| US4505753A (en) * | 1983-06-30 | 1985-03-19 | Research One Limited Partnership | Cementitious composite material |
| US4482385A (en) * | 1983-06-30 | 1984-11-13 | Research One Limited Partnership | Cementitious composite material with stainless steel particulate filler |
| US4501830A (en) * | 1984-01-05 | 1985-02-26 | Research One Limited Partnership | Rapid set lightweight cement product |
| JPS61122146A (en) * | 1984-11-14 | 1986-06-10 | 三菱油化株式会社 | Hydraulic cement composition and manufacture of cement moldings |
| US4640715A (en) * | 1985-03-06 | 1987-02-03 | Lone Star Industries, Inc. | Mineral binder and compositions employing the same |
| IT1200142B (en) * | 1985-11-08 | 1989-01-05 | Modern Advanced Concrete | METHOD TO IMPROVE THE FLUIDIFICATION OF CEMENT MIXTURES |
| DK337186D0 (en) * | 1986-07-15 | 1986-07-15 | Densit As | PROCEDURE AND MATERIALS FOR THE MANUFACTURE OF A FORMATED ITEM |
| US4780141A (en) * | 1986-08-08 | 1988-10-25 | Cemcom Corporation | Cementitious composite material containing metal fiber |
| US4861378A (en) * | 1987-03-13 | 1989-08-29 | Denki Kagaku Kogyo Kabushiki Kaisha | Cement additive containing superplasticizer and bentonite |
| US4963515A (en) * | 1987-12-02 | 1990-10-16 | The Duriron Company, Inc. | Lightweight hydrogel-bound aggregate shapes and process for producing same |
| GB8805481D0 (en) * | 1988-03-08 | 1988-04-07 | Marley Uk Ltd | Cementitious products |
| GB8813894D0 (en) * | 1988-06-11 | 1988-07-13 | Redland Roof Tiles Ltd | Process for production of concrete building products |
| JP2663298B2 (en) * | 1988-06-28 | 1997-10-15 | 宇部興産株式会社 | Heated curing cement composition, its curing method and cured product |
| JPH04501406A (en) * | 1988-10-05 | 1992-03-12 | コマルコ・アルミニューム・リミテッド | low cement refractories |
| NO167649C (en) * | 1989-04-10 | 1993-07-06 | Norske Stats Oljeselskap | PROCEDURE FOR THE ADDITION OF SILICIDE OXIDE IN A HYDRAULIC CEMENT SUSPENSION |
| JPH04124054A (en) * | 1990-09-14 | 1992-04-24 | Jdc Corp | Superhigh-strength concrete |
| US5250113A (en) * | 1991-07-31 | 1993-10-05 | W. R. Grace & Co.-Conn. | Dry castable concrete compositions and methods of preparing and dry casting the same |
| JPH0542527A (en) * | 1991-08-08 | 1993-02-23 | Ohbayashi Corp | Manufacture of hydraulic compound |
| JP3200804B2 (en) * | 1992-05-07 | 2001-08-20 | 太平洋セメント株式会社 | Hydraulic composite material and method for producing high-strength concrete using the same |
-
1995
- 1995-02-06 US US08/384,645 patent/US5531823A/en not_active Expired - Fee Related
- 1995-12-21 AU AU42942/96A patent/AU4294296A/en not_active Abandoned
- 1995-12-21 CA CA 2207915 patent/CA2207915C/en not_active Expired - Fee Related
- 1995-12-21 WO PCT/CA1995/000716 patent/WO1996024564A1/en active Application Filing
Also Published As
| Publication number | Publication date |
|---|---|
| WO1996024564A1 (en) | 1996-08-15 |
| US5531823A (en) | 1996-07-02 |
| CA2207915A1 (en) | 1996-08-15 |
| AU4294296A (en) | 1996-08-27 |
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