AU2021101949A4 - A Kind of Green High Performance Concrete - Google Patents
A Kind of Green High Performance Concrete Download PDFInfo
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- AU2021101949A4 AU2021101949A4 AU2021101949A AU2021101949A AU2021101949A4 AU 2021101949 A4 AU2021101949 A4 AU 2021101949A4 AU 2021101949 A AU2021101949 A AU 2021101949A AU 2021101949 A AU2021101949 A AU 2021101949A AU 2021101949 A4 AU2021101949 A4 AU 2021101949A4
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- 239000004574 high-performance concrete Substances 0.000 title abstract description 6
- 239000011374 ultra-high-performance concrete Substances 0.000 claims abstract description 67
- 239000000843 powder Substances 0.000 claims abstract description 45
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 40
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 38
- 239000010959 steel Substances 0.000 claims abstract description 38
- 239000004568 cement Substances 0.000 claims abstract description 33
- 239000002893 slag Substances 0.000 claims abstract description 27
- 229910021487 silica fume Inorganic materials 0.000 claims abstract description 21
- 239000010453 quartz Substances 0.000 claims abstract description 20
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 18
- 239000002131 composite material Substances 0.000 claims abstract description 13
- 239000000835 fiber Substances 0.000 claims abstract description 12
- 239000000203 mixture Substances 0.000 claims abstract description 11
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 8
- 239000006004 Quartz sand Substances 0.000 claims abstract description 8
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 6
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 6
- 239000010703 silicon Substances 0.000 claims abstract description 6
- 239000010881 fly ash Substances 0.000 claims abstract description 5
- 239000002994 raw material Substances 0.000 claims abstract description 5
- 229910052742 iron Inorganic materials 0.000 claims abstract description 4
- 235000012239 silicon dioxide Nutrition 0.000 claims description 21
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 18
- 239000003638 chemical reducing agent Substances 0.000 claims description 12
- 239000011230 binding agent Substances 0.000 claims description 10
- 239000004576 sand Substances 0.000 claims description 6
- 239000000377 silicon dioxide Substances 0.000 claims description 4
- 239000002253 acid Substances 0.000 claims description 3
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical group [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 2
- 229910052681 coesite Inorganic materials 0.000 claims description 2
- 229910052906 cristobalite Inorganic materials 0.000 claims description 2
- 239000011777 magnesium Substances 0.000 claims description 2
- 229910052749 magnesium Inorganic materials 0.000 claims description 2
- 229910052682 stishovite Inorganic materials 0.000 claims description 2
- 229910052905 tridymite Inorganic materials 0.000 claims description 2
- 238000001035 drying Methods 0.000 abstract description 7
- 239000004566 building material Substances 0.000 abstract description 2
- 239000000463 material Substances 0.000 description 34
- 230000036571 hydration Effects 0.000 description 20
- 238000006703 hydration reaction Methods 0.000 description 20
- 239000002245 particle Substances 0.000 description 16
- 238000012360 testing method Methods 0.000 description 16
- 230000007423 decrease Effects 0.000 description 15
- 239000004567 concrete Substances 0.000 description 14
- 229910052500 inorganic mineral Inorganic materials 0.000 description 10
- 239000011707 mineral Substances 0.000 description 10
- 230000000694 effects Effects 0.000 description 9
- 238000000034 method Methods 0.000 description 7
- 239000000378 calcium silicate Substances 0.000 description 5
- 229910052918 calcium silicate Inorganic materials 0.000 description 5
- OYACROKNLOSFPA-UHFFFAOYSA-N calcium;dioxido(oxo)silane Chemical compound [Ca+2].[O-][Si]([O-])=O OYACROKNLOSFPA-UHFFFAOYSA-N 0.000 description 5
- 230000008859 change Effects 0.000 description 3
- 238000013461 design Methods 0.000 description 3
- 239000002086 nanomaterial Substances 0.000 description 3
- 238000012856 packing Methods 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 230000007704 transition Effects 0.000 description 3
- 239000000853 adhesive Substances 0.000 description 2
- 230000001070 adhesive effect Effects 0.000 description 2
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 2
- 239000000920 calcium hydroxide Substances 0.000 description 2
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000003517 fume Substances 0.000 description 2
- 238000000227 grinding Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000011858 nanopowder Substances 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 230000003334 potential effect Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 229910001653 ettringite Inorganic materials 0.000 description 1
- 239000011210 fiber-reinforced concrete Substances 0.000 description 1
- 238000013100 final test Methods 0.000 description 1
- 239000011372 high-strength concrete Substances 0.000 description 1
- 239000002440 industrial waste Substances 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000004452 microanalysis Methods 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- -1 on one hand Substances 0.000 description 1
- 230000036314 physical performance Effects 0.000 description 1
- 229920005646 polycarboxylate Polymers 0.000 description 1
- 230000000979 retarding effect Effects 0.000 description 1
- 102200129367 rs1805044 Human genes 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 239000008030 superplasticizer Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 230000003245 working effect Effects 0.000 description 1
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
- C04B2103/30—Water reducers, plasticisers, air-entrainers, flow improvers
- C04B2103/302—Water reducers
-
- 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
- C04B2103/56—Opacifiers
- C04B2103/58—Shrinkage reducing agents
-
- 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
- C04B22/00—Use of inorganic materials as active ingredients for mortars, concrete or artificial stone, e.g. accelerators, shrinkage compensating agents
- C04B22/06—Oxides, Hydroxides
- C04B22/066—Magnesia; Magnesium hydroxide
-
- 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
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
- C04B2201/52—High compression strength concretes, i.e. with a compression strength higher than about 55 N/mm2, e.g. reactive powder concrete [RPC]
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
Abstract
The invention discloses a kind of green high performance concrete (HPC), belonging to the
technical field of building materials. The ultra-high performance concrete (UHPC) in the
present invention comprises the following raw materials in percentage by weight: 33-35% of
cement, 12-15% of steel slag powder, 3-5% of composite expansive agent, 18-20% of micro
nano active admixture, 8-10% of silica fume, 18-20% of quartz sand, 1.6-1.8% of waterreducer
and 1.8-2% of steel fiber. Specifically, the micro-nano active admixture is a mixture of silicon
rich iron tailings, slag, fly ash and quartz powder in a mass ratio of 44:22:28:6. The UHPC of
the invention has good working performance, wherein, under standard curing conditions, the
flexural strength can reach 25.6MPa, compressive strength can reach 142MPa, and elastic
modulus can reach 52.4GPa, respectively. Besides, the adiabatic temperature rise is only 59.7
C and the drying shrinkage rate in 180d is only 280x106.
Description
A Kind of Green High Performance Concrete
The invention relates to the technical field of building materials, in particular to a green
high performance concrete.
Ultra-high performance concrete (UHPC), different from traditional high-strength
concrete (HSC) and steel fiber reinforced concrete (SFRC), refers to a new type of
cement-based engineering material whose properties, such as mechanical properties,
durability and so on, are far superior to ordinary concrete and high performance concrete.
Further, it is also called reactive powder concrete (RPC), because its preparation method
can increase the fineness of raw materials and improve the active components
(pozzolanic activity).
As a modern advanced material, on one hand, UHPC innovates the composite mode of
cement-based materials (concrete or mortar), fiber and steel (steel bar or high-strength
prestressed steel bar); on the other hand, it greatly raises the strength utilization efficiency
of fiber and steel bar in concrete. Therefore, great progress has taken place in the
comprehensive performance of cement-based structural materials. In terms of its
excellent mechanical properties and durability, UHPC has been paid much attention since
it came out, and the research on UHPC is becoming increasingly mature. Specifically,
researchers have done a lot of research work on raw material composition, mix design,
mechanical properties, durability, working performance and microstructure of UHPC.
In recent years, with the technical development of superplasticizer and superfine mineral
admixture, UHPC with 100-150 MPa can be prepared through conventional materials and
general technology. Moreover, UHPC is gradually replacing ordinary concrete in some
practical projects because of its ultra-high strength, ultra-high toughness, ultra-low wear
coefficient and high environmental protection property. For example, UHPC has been
used in structures with thin structural dimensions, such as steel bridge deck pavement and
prefabricated part.
However, for some mass concrete structures requiring ultra-high performance, the
application of UHPC in similar projects is limited because of the high hydration heat and
shrinkage caused by the large amount of cement in the preparation process. Therefore, it
is an urgent technical problem to provide UHPC with low heat of hydration and low
shrinkage.
The purpose of the present invention is to provide a green high-performance concrete to
solve the problems existing in the prior art, so that the UHPC can be equipped with low
hydration heat and low shrinkage.
To achieve the above-mentioned purpose, the present invention provides the following
scheme.
A kind of UHPC is proposed by the invention, which consists of the following raw
materials in percentage by weight.
33-35% of cement, 12-15% of steel slag powder, 3-5% of composite expansive agent, 18
% of micro-nano active admixture, 8-10% of silica fume, 18-20% of quartz sand, 1.6
1.8% of water reducer and 1.8-2% of steel fiber. Wherein, the micro-nano active admixture is a mixture of silicon-rich iron tailings, slag, fly ash and quartz powder with a mass ratio of 44:22:28:6; the specific surface area of the micro-nano active admixture is more than 1000 m2 /kg.
The composite expansive agent is magnesium composite expansive agent.
Further, the cement is Huaxin P- 42.5 grade cement.
Further, the quartz sand is in 20-200 meshes and contains 99.6% SiO2.
Further, the silicon content in the silica fume is more than 98%.
Further, the specific surface area of the steel slag powder is 600m 2 /kg.
Further, the steel fiber is copper-plated steel fiber with a diameter of 0.22 mm.
Further, the water reducer is polycarboxylic acid water reducer CP-J.
Furthermore, the water to binder ratio of the UHPC is 0.16, and the binder to sand ratio is
1:1.
The invention discloses the following technical effects.
(1) In the present invention, the ratio of water to binder is 0.16, of binder to sand is 1:1, of
cement to steel slag powder to expansive agent to micro-nano material to silica fume is
:15:5:20:10, and the amount of admixture- quartz powder is adjusted appropriately, so
that the prepared UHPC has good working performance, specifically, under standard
curing conditions, the flexural strength can reach 25.6MPa, compressive strength can
reach 142MPa, and elastic modulus can reach 52.4GPa, respectively. Besides, the
adiabatic temperature rise is only 59.7C and the drying shrinkage rate in 180d is only
280x10-6.
(2) The compressive strength of UHPC has a good correlation with the compactness of
cementitious material system, that is, the strength of UHPC increases with the decrease of porosity of cementitious material. In addition, the addition of mineral admixtures can not only adjust the particle size distribution of cementitious materials to realize dense filling, but also give full play to the pozzolanic effect to improve the strength of UHPC.
Moreover, the hydration heat of UHPC can be obviously reduced by adding a large
amount of mineral admixture and quartz powder.
(3) The addition of steel slag powder can not only effectively reduce the hydration heat of
UHPC, but also inhibit the shrinkage. Besides, the drying shrinkage of UHPC can be
greatly reduced by adding a small amount of ettringite composite expansive agent.
(4) The hydrated products in UHPC mainly consist of dense and heterogeneous hydrated
calcium silicate. Further, a small amount of ultrafine quartz powder particles can react in
alkaline environment to form a continuous and dense transition zone with hydrated
calcium silicate gel, which improves the interface structure between aggregate and
hydrated products.
In order to explain the embodiments of the present invention or the technical scheme in
the prior art more clearly, the figures needed in the embodiments will be briefly
introduced below. Obviously, the figures in the following description are only some
embodiments of the present invention, and for ordinary technicians in the field, others can
be obtained according to these figures without paying creative labour.
Figure 1 shows the change of porosity of admixture compact.
Figure 2 indicates the influence of quartz powder content on the porosity of aggregate
system.
Figure 3 is an adiabatic temperature rise diagram of UHPC with low hydration heat and
low shrinkage.
Figure 4 is a dry shrinkage diagram of UHPC with low hydration heat and low shrinkage.
Figure 5 is a typical SEM micrography of UHPC with low hydration heat and low
shrinkage. Wherein, (a) is a gel structure and (b) is a binder-bone interface structure.
Various exemplary embodiments of the present invention will now be described in detail,
which should not be regarded as a limitation of the present invention, but rather as a more
detailed description of certain aspects, characteristics and embodiments of the present
invention.
It should be understood that the terms described in the present invention are only for
describing specific embodiments and are not intended to limit the present invention. In
addition, as for the numerical range in the present invention, it should be understood that
every intermediate value between the upper limit and the lower limit of the range is also
specifically disclosed. Intermediate values within any stated value or stated range and
every smaller range between any other stated value or intermediate values within the
stated range are also included in the present invention. The upper and lower limits of
these smaller ranges can be independently included or excluded from the range.
Unless otherwise stated, all technical and scientific terms used herein have the same
meanings as commonly understood by those skilled in the art to which the present
invention relates. Although the present invention only describes preferred methods and
materials, any methods and materials similar or equivalent to those described herein may
be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe methods and/or materials related to the documents. In case of conflict with any incorporated documents, the contents of this specification shall prevail.
Without departing from the scope or spirit of the invention, it is obvious to those skilled
in the art that many modifications and changes can be made to the specific embodiments
of the specification of the invention. Other embodiments derived from the description of
the present invention will be apparent to the skilled person. The specification and
examples of this application are only exemplary.
As used herein, "including", "comprising", "having", "containing" and so on, are all open
terms, which means including but not limited to.
Unless otherwise specified, "parts" mentioned in the present invention are calculated by
mass parts.
The micro-nano active admixture (ICBM) of the invention takes slag (S), steel slag (I),
fly ash (C) and quartz powder (Q) as raw materials. Preferably, it is a mixture of silicon
rich iron tailings, slag, fly ash and quartz powder according to the mass ratio of
44:22:28:6, further, the specific surface area of the micro-nano active admixture is larger
than 1000 m2 .
The water reducer used in the invention is polycarboxylic acid water reducer CP-J.
The main physical performance indexes of cement, silica fume, steel slag powder and
micro-nano materials used in the invention are shown in Table 1.
Table 1 Raw Density Specific Water Mobility R28P 28d compressive material /g -cm area/m2-kg-c ratio/% ratio/% strength ratio/% Cement 4.20 380 100 100 49.3 100.0 Silica fume 2.30 / 115 90 52.1 105.7
Steel slag 2.81 600 105 100 40.7 82.6 powder Micro nano 2.64 1200 95 110 42.5 86.2 materials The particle size distribution of cement and mineral admixture is shown in Table 2.
Table 2 No. D50/[m D10/ m D25/[m D75/[m D90/tm P-0 42.5 14.50 2.54 5.58 20.24 36.74 cement Silica fume 0.50 0.14 0.25 0.86 1.02 Steel slag 14.10 2.12 5.08 20.02 35.25 powder Micro-nano 1.00 0.61 0.78 1.42 1.99 materials 1. Study on porosity of UHPC cementitious materials and aggregate systems with
different compositions
Adjusting the proportion of particles with different sizes in the cementitious material
system will cause the change of porosity. Based on the particle dense packing theory, the
composite cement dry powder compact is prepared by mechanical pressure method, and
the dense packing of particles with different sizes is studied by testing the porosity of the
compact. It can be seen from Table 2 that the cement and steel slag powder of D50 are
14.50tm and 14.10tm, respectively. Since their fineness is similar, the invention
considers that the proportion change has little effect on the bulk density of the
cementitious material system. Taking the ternary system of cement-micro-nano-silica
fume as basis, the influence of different particle sizes on the compactness of adhesive
material is studied. Fig.1 shows the porosity changes of cement, micro-nano and silica
fume compacts with different proportions, in which the proportions of micro-nano and
silica fume are respectively 3:1, 2:1, 1:1, 1:2 and 1:3, and the total proportion of
admixture is respectively 20%, 25%, 30%, 35% and 40%. It can be seen from the figure that the porosity of the adhesive system is reduced to varying degrees by the addition of different amounts of micro-nano and silica fume, further, the overall porosity decreases first and then increases with the increase of the content of micro-nano and silica fume.
When the ratio of cementitious materials compact cement, micro-nano materials and
silica fume is 70:20:10, the lowest porosity of the system is only 34.0%, followed by
34.2% with ratio of 80:5:15. At this time, it is considered that silica fume and micro-nano
can fully fill the larger cement particles, and play their dense filling role, thus improving
the bulk density of ternary cementitious system, which is basically consistent with the
maximum density theory. However, with the further increase of the content of micro
nano and silica fume, the accumulation of large cement particles will be affected due to
the effect of wall attachment, which will reduce the compactness and increase the
porosity of the whole system.
The proportion of particles with different sizes in aggregate system directly affects the
continuity of aggregate and the compactness of the system. In this invention, continuous
graded quartz sand of 20-120 meshes and quartz powder of 200 meshes are used to
prepare aggregate. Fig.2 shows the influence of different quartz powder content on the
porosity of aggregate system. It can be seen that with the increase of 200-mesh quartz
powder content, the porosity of aggregate system first decreases rapidly and then
increases. When the content of quartz powder reaches 15%, the porosity of the whole
aggregate system is the lowest and the bulk density is the highest.
2. Mix design of UHPC
On the basis of a large number of preliminary exploratory tests, the mix proportion of
UHPC is designed combined with the results of dense packing test. The cementitious material and aggregate are prepared by three combinations with the lowest porosity of cementitious material system and aggregate system respectively, shown in Table 3. It can be seen from the test results in Table 3 that the compressive strength of UHPC has a good correlation with the compactness of the cementitious material system. Specifically, with the decrease of the porosity of the cementitious material, the ternary cementitious material tends to be more closely packed, and the compressive strength of UHPC also increases, which indicates that the stacking mode of cementitious material particles has a great influence on the macro-mechanical properties of UHPC. In other words, the closer the particles with different sizes are stacked, the smaller the porosity is, and theoretically, the matrix can obtain higher mechanical strength. When the ratio of cement, micro-nano and silica fume is 70:20:10, the compressive strength of each specimen reaches the highest in the same group, which is consistent with the experimental results of Fig.1. In addition, it is found that with the increase of silica fume content and the decrease of ultrafine powder content, the working performance of UHPC decreases gradually. When the ratio of cement, micro-nano and silica fume is 80:5:15, the expansion degree of
UHPC decreases by 50mm, which is mainly because the self-made ultrafine powder
adopts physical viscosity reduction technology, which has obvious ball effect and certain
physical water reduction effect.
The test results in Table 3 show that the particle stacking morphology of aggregate has
great influence on the mechanical properties and working properties of UHPC. In the
same cementitious material system, the fluidity of UHPC mixture decreases with the
increase of quartz powder content, which is mainly due to the large specific surface area
of quartz powder and the increase of water demand. Therefore, water-binder ratio 0.16, binder-sand ratio 1:1, cementitious materials ratio 70:20:10, quartz powder content 20%, water reducer content 1.8% and steel fiber volume content 2% are selected as the optimized basic ratio.
Table 3 Cement: Steel 28d Water- Binder- micro- Quartz Water fiber Expansion compressive No. binder sand nano powder reducer volume degree strength ratio ratio materials: content content content /mm/MPa silica fume 1 0.16 1:1 70:20:10 15 1.8 2 635 148.2 2 0.16 1:1 70:15:15 15 1.8 2 610 140.5 3 0.16 1:1 80:5:15 15 1.8 2 585 143.8 4 0.16 1:1 70:20:10 20 1.8 2 610 152.3 0.16 1:1 70:15:15 20 1.8 2 595 143.4 6 0.16 1:1 80:5:15 20 1.8 2 575 145.6 7 0.16 1:1 70:20:10 25 1.8 2 590 146.5 8 0.16 1:1 70:15:15 25 1.8 2 565 133.8
9 0.16 1:1 80:5:15 25 1.8 2 560 139.0 3. Preparation of UHPC with low hydration heat and low shrinkage
It can be seen from the basic ratio that UHPC has a very large proportion of cement,
which will inevitably lead to high hydration heat and large shrinkage of UHPC. When
preparing high-strength concrete, people usually add a large amount of mineral admixture
to reduce hydration heat and shrinkage. Steel slag powder is a mineral admixture made by
grinding steel-making industrial waste residue, which contains a certain amount of
clinker minerals such as C2S and C3S, as well as a large amount of CaO and MgO, which
not only has high potential activity but also contributes to inhibiting shrinkage. Therefore,
ultra-fine steel slag powder is used as mineral admixture, and a certain amount of
expansion agent is used to prepare UHPC with low hydration heat and low shrinkage. On the basis of optimized ratio, steel slag powder and composite expansion agent are used to directly replace cement for testing. The test ratio and results are shown in Table 4
. Table 4
Content of Content of Expansion 28d Adiabatic 180d dry No. steel slag expansive degree compressive temperature shrinkage powder agent /mm strength /MPa rise/°C /10-6 1 0 0 610 152.3 65.6 480 2 10 0 610 144.5 62.8 446 3 15 0 605 142.6 60.6 428 4 20 0 600 132.6 57.3 408 0 5 590 146.3 63.5 336 6 15 5 585 141.8 59.5 285
7 15 8 560 134.5 57.2 268 It can be seen from Table 4 that with the increase of steel slag powder content, the
expansion degree of UHPC changes little and the compressive strength decreases
gradually, but when the content is less than 15%, the strength decreases little, and when it
exceeds 15%, the strength will decrease greatly. The addition of steel slag powder can
reduce the adiabatic temperature rise and dry shrinkage of UHPC, especially the adiabatic
temperature rise. This is because when preparing UHPC, the water-binder ratio is low,
and some cement particles can't be hydrated, but can only play a filling role. After ultra
fine grinding, the potential activity of steel slag powder is excited so that it can replace
some cement and give full play to its activity and filling role. Therefore, the cement
consumption is reduced causing reduced hydration heat. Moreover, the components such
as CaO and MgO contained in UHPC can also inhibit the drying shrinkage of UHPC to
some extent. The addition of composite expansion agent can obviously inhibit the drying
shrinkage of UHPC, and the drying shrinkage rate gradually decreases with the increase
of expansion agent content. However, when the recommended amount of expansion agent is 8%, the fluidity and compressive strength of UHPC decrease obviously. Considering the workability, compressive strength, adiabatic temperature rise and dry shrinkage of
UHPC, it is advisable to select 15% of steel slag powder and 5% of expansive agent.
Compared with the basic ratio, the adiabatic temperature rise decreases by 6.1°C, and the
dry shrinkage rate decreases by 195x106 in 180d days.
4. Performance test of low hydration heat and low shrinkage UHPC.
Test method:
(1) The working performance test shall be conducted in accordance with Standardfortest
method of mechanicalpropertieson ordinaryconcrete (GB/T 50081-2002).
(2) The mechanical property test shall be conducted in accordance with Standardfor test
methods of mechanicalpropertieson ordinary concrete (GB/T 50081-2002) and Reactive
powder concrete (GBT31387-2015), wherein, the concrete specimen shall be a cube
specimen with the size of 100mm.
(3) Shrinkage and durability tests shall be conducted in accordance with Standardfortest
methods of long-term performance and durability of ordinary concrete (GB/T 50082
2009).
According to the above test results, the final test ratio is determined and the performance
test is carried out. Ratio and test results are shown in Table 5. From the data in the table,
it can be seen that UHPC has good working performance, with 28d flexural strength and
compressive strength reaching 25.6MPa and 142.OMPa respectively, elastic modulus
exceeding 50GPa, adiabatic temperature rise below 60°C and dry shrinkage rate below
300x10-6. Test results of adiabatic temperature rise and dry shrinkage performance are
shown in fig.3 and fig.4. It can be seen from fig.3 that the adiabatic temperature rise peak of UHPC material with low hydration heat and low shrinkage appears at 89.7C within
31.5h after entering the mold, and the time of appearing temperature peak is obviously
longer than that of ordinary concrete. This is because the special retarding
polycarboxylate water reducer can effectively delay the early hydration heat release rate
of cement and play a positive role in reducing the adiabatic temperature rise of concrete.
It can be seen from fig.4 that the dry shrinkage rate of UHPC increases greatly within 60
days, and gradually stabilizes after reaching 120 days, and the dry shrinkage rate after
180 days is only 280x10-6, which is significantly lower than that of ordinary C50
concrete, which should be attributed to 50% composite mineral admixture and expansive
agent, which effectively inhibits the shrinkage of UHPC.
Table 5
Cement: steel Water- Binder- slag powder: Quartz Water Steel mx binder sand expansive agent: Mix bid r ad micro-nano powder reducer fiber proportion ratio ratio material: silica fume 0.16 1:1 50:15:5:20:10 20 1.8 2 28d Elastic Adiabatic 180d Fluidity flexural 28d compressive modulus temperature drying Performance /mm strength strength /MPa /GPa rise /C shrinkage test /MPa rate /106 590 25.6 142.0 52.4 59.7 280 5. Microanalysis of UHPC under standard curing
Fig.5 is a typical SEM micrography of UHPC with low hydration heat and low shrinkage
for 28 days under standard curing conditions. It can be seen from (a) and (b) that the hydration products of UHPC are mainly dense and heterogeneous hydrated calcium silicate, mixed with many mineral admixtures with partially hydrated or un-hydrated surface, and it is difficult to find needle-like or flaky calcium hydroxide crystals. The results show that the large amount of steel slag powder, ultrafine powder and silica fume can not only fill the dense cementitious material system well, but also give full play to the pozzolanic activity of the three materials, and consume a lot of calcium hydroxide produced by cement hydration, thus making UHPC system more dense. From (b), it can be clearly observed that there are two types of interface bonding between cementitious materials and quartz sand aggregates. One is that the interface between hydrated calcium silicate gel and large grain quartz sand is clear, and there is no obvious interface transition zone, but the bonding is quite tight; the other is that the interface between a small amount of ultrafine quartz powder particles and hydrated calcium silicate gel is unclear, and there is a continuous and dense transition zone, which indicates that the surface of some ultrafine quartz powder particles reacts and forms a compact whole with hydration products, further improving the interface structure as well as the compressive strength of UHPC.
The above embodiments only describe the preferred mode of the invention, but do not
limit the scope of the invention. On the premise of not departing from the design spirit of
the invention, various modifications and improvements made by ordinary technicians in
the field to the technical scheme of the invention shall fall within the protection scope
determined by the claims of the invention.
Claims (8)
1. The UHPC is characterized by comprising the following raw materials in percentage
by weight.
33-35% of cement, 12-15% of steel slag powder, 3-5% of composite expansive agent, 18
% of micro-nano active admixture, 8-10% of silica fume, 18-20% of quartz sand, 1.6
1.8% of water reducer and 1.8-2% of steel fiber. Wherein, the micro-nano active
admixture is a mixture of silicon-rich iron tailings, slag, fly ash and quartz powder with a
mass ratio of 44:22:28:6; the specific surface area of the micro-nano active admixture is
more than 1000 m2 /kg.
The composite expansive agent is magnesium composite expansive agent.
2. The UHPC according to claim 1, characterized in that the cement is Huaxin P-0 42.5
grade cement.
3. The UHPC according to claim 1, characterized in that the quartz sand is in 20-200
meshes and contains 99.6% SiO2.
4. The UHPC according to claim 1, characterized in that the silicon content in the silica
fume is more than 98%.
5. The UHPC according to claim 1, characterized in that the specific surface area of the
steel slag powder is 600 m 2 /kg.
6. The UHPC according to claim 1, characterized in that the steel fiber is copper-plated
steel fiber with a diameter of 0.22 mm.
7. The UHPC according to claim 1, characterized in that the water reducer is
polycarboxylic acid water reducer CP-J.
8. The UHPC according to claim 1, characterized in that the water to binder ratio of the
UHPC is 0.16, and the binder to sand ratio is 1:1.
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CN111995321A (en) * | 2020-08-21 | 2020-11-27 | 湖州上建混凝土有限公司 | High slump loss resistant concrete and preparation method thereof |
CN111995321B (en) * | 2020-08-21 | 2022-04-22 | 湖州上建混凝土有限公司 | High slump loss resistant concrete and preparation method thereof |
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