GB2613913A

GB2613913A - Antifreezing and high-ductility cement-based material, and preparation method, use and use method thereof

Info

Publication number: GB2613913A
Application number: GB2208456.0A
Authority: GB
Inventors: Yin Liqiang; Liu Shuguang; Yan Changwang; Li Danqing; Zhang Ju; Wang Xiaoxiao; Jing Lei
Original assignee: Inner Mongolia University of Technology
Current assignee: Inner Mongolia University of Technology
Priority date: 2021-12-17
Filing date: 2022-06-09
Publication date: 2023-06-21
Also published as: GB202208456D0; CN114180911A; CN114180911B

Abstract

An antifreezing and high-ductility cement-based material, a preparation method, and use in a negative bending moment area of a reinforced concrete (RC) continuous beam bridge and a method for the use is defined. The cement-based material comprises cement, high calcium fly ash, quartz sand, and water in a mass ratio of (280-350):(680-760):(640-720):(200-280), a water reducer, thickener and defoamer in a mass ratio of (1-1.5):(0.1-0.2):(0.8-1.6), wherein the cement and the water reducer have a mass ratio of 100:(3-5.2), with 2-2.5% of the total material volume comprising a polyvinyl alcohol (PVA) fibre. The cement may be a Portland cement, the water reducer may be a polycarboxylate water reducer, and the thickener may be hydroxypropyl methylcellulose. The preparation method comprises mixing the cement, high-calcium fly ash, quartz sand, and thickener, and adding to a mixed solution of water reducer, defoamer, and water to obtain a paste, and mixing the paste with the PVA fibre. The RC continuous beam bridge comprises a prefabricated RC beam 1, a prestressed tendon 2 and a prestressed steel cable 3, a transverse wet joint of the negative bending moment area 4, a permanent support 5, a bridge pier 6, a temporary support 7, and a scabbling part 8.

Description

ANTIFREEZING AND HIGH-DUCTILITY CEMENT-BASED MATERIAL, AND PREPARATION METHOD, USE AND USE METHOD THEREOF

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of cement-based materials, in particular to an antifreezin2 and high-ductility cement-based material, and a preparation method, use and a use method thereof.

BACKGROUND ART

[0002] Reinforced concrete (RC) continuous beam bridges are generally constructed based on a method of "first simply supported then continuously supported". This construction method has higher rigidity, smaller deformation, fewer expansion joints, and shorter construction period compared with a continuous structure formed by cast-in-place concrete. The construction method "first simply supported then continuously supported" specifically includes: centralized prefabrication of beams and slabs is performed in a prefabrication field; when hoisting, temporary supports are installed in place according to simply supported beams, permanent supports are preset on bridge piers, and steel bars of longitudinal wet joints are connected and transverse wet joints are concreted; prestressed tendons of a bridge deck are tensioned, a system is converted into a continuous beam, and hinge joints am concreted; and the temporary supports and appurtenant works of the bridge deck in construction are removed. During the whole process, the concreting of transverse wet joints is a key and difficult point of the construction.

[0003] Under the normal load, an upper part of the negative bending moment area of the RC continuous beam bridge is in tension, while the concrete has a low tensile strength (about lilt) of a compressive strength) and poor ductility. In the cold northern regions, the concrete in the negative bending moment area is prone to cracking. Moreover, in snowy days, snow melting agents (with chloride salts as a main component) need to be sprinkled to ensure the safe operation of traffic, such that the negative bending moment area of heam is in a chloride salt environment. Due to the promoted diffusion of chloride ions by a load coupling effect, the corrosion of steel bars is accelerated to reduce a bearing capacity. A survey has found that in the RC continuous beam bridges that have been built and operated, cracks have occurred in negative bending moment area sections of many bridges, causing adverse effects on a service performance and a service life of the bridges. In the construction method of continuous beam bridge of "simply supporting and then continuously supporting", when the system is converted, a maximum bending moment of the beam is at a cast-in-place section where two beams are connected, that is, at the transverse wet joint. The transverse wet joints are located at the negative bending moment of the continuous beam bridge, and the concrete in northern severe cold areas is easy to fall off and crack under the action of freeze-thaw cycles. These factors frequently cause the bridge to work with cracks after being opened to traffic, resulting in problems such as premature corrosion of steel bars.

[0004] Therefore, it is of great value and significance to study an antifrcezing and high-ductility cement-based material for a structure in a negative bending moment area of a fatigue-resistant RC continuous beam bridge. The material can overcome the poor fatigue resistance, frost resistance and crack resistance in the negative bending moment area, and prolong a service life of the continuous beam bridge.

SUMMARY

[0005] To overcome the deficiencies of the prior art, an objective of the present disclosure is to provide an antifreezing and high-ductility cement-based material, and a preparation method, use and a use method thereof.

[0006] To achieve the above objective, the present disclosure provides the following technical solutions.

[0007] The present disclosure provides an antifreezing and high-ductility cement-based material, including a cement, high-calcium fly ash, quartz sand, a water reducer, a thickener, a dcfoamer, a polyvinyl alcohol fiber, and water; where [0008] the cement, the high-calcium fly ash, the quartz sand, and the water have a mass ratio of (280-350):(680-760):(640-720):(200-280); [0009] the water reducer, the thickener, and the defoamer have a mass ratio of (1 -1.5):(0.1-0.2):(0.8-1.6); [0010] the cement and the water reducer have a mass ratio of 100:(3-5.2); and [0011] the polyvinyl alcohol fiber is 2% to 2.5% of a total volume of the cement-based material. [0012] Preferably, the cement may be a Portland cement; the high-calcium fly ash may have a particle size of less than or equal to 70 pm; and the quartz sand may have a particle size of 0.075 mm to 0.125 mm [0013] Preferably, the water reducer may be a polycarboxylate water reducer; and the thickener may he hydroxypropyl methylcellulose.

[0014] Preferably, the polyvinyl alcohol fiber may have a density of 1 g/cm3 to 1.5 g/cm3, a diameter of 0.03 mm to 005 mm a length of 10 mm to 14 mm a fineness of 13 dtex to 17 dtex, an elongation of 4% to 8%, a tensile strength of 1,500 MPa to 1,700 MPa and an elastic modulus of 35 GPa to 45 GPa.

[0015] The present disclosure further provides a preparation method of the antifreezing and high-ductility cement-based material, including the following steps: [0016] 1) mixing the cement, the high-calcium fly ash, the quartz sand, and the thickener to obtain a powder; [0017] 2) mixing the water reducer, the defoamer, and water to obtain a mixed solution; [0018] 3) mixing the mixed solution and the powder to obtain a paste; and [0019] 4) mixing the paste and the polyvinyl alcohol fiber to obtain the antifreezing and high-ductility cement-based material.

[0020] Preferably, the mixing may be conducted for 1 min to 4 min in step 2), for 4 min to 10 mm in step 3), and for 2 min to 6 mm in step 4).

[0021] The present disclosure further provides use of the cement-based material in a negative bending moment area of an RC continuous beam bridge, where the RC continuous beam bridge includes a prefabricated RC beam (1), a prestressed tendon (2), a prestressed steel cable (3), a transverse wet joint of the negative bending moment area (4), a permanent support (5), a bridge pier (6), a temporary support (7), and a scabbling part (8).

[0022] The present disclosure further provides a method for concreting a negative bending moment area of an RC continuous beam bridge using the antifreezing and high-ductility cement-based material, including the following steps: [0023] I) concreting transverse wet joints at tops of l# and 34 continuous piers and a longitudinal wet joint in the negative bending moment area with the antifreezing and high-ductility cement-based material, followed by tensioning the prestressed steel cable in the negative bending moment area and conducting duct grouting sequentially; and [0024] 2) concreting transverse wet joints at tops of 2# and 4# continuous piers and the longitudinal wet joint in the negative bending moment area with the antifreezing and high-ductility cement-based material, followed by tensioning the prestressed steel cable in the negative bending moment area and conducting duct grouting sequentially.

[0025] Preferably, in step 1), the method may further include the following steps before the concreting: i, erecting the prefabricated RC beam, and welding connectors; and ii, laying a diaphragm plate formwork, welding steel bars of a diaphragm plate and protrusion steel bars of the prefabricated RC beam in sequence, and concreting in the diaphragm plate formwork; where [0026] the connector includes a longitudinal wet joint, a diaphragm plate, and a transverse wet joint steel bar; and the transverse wet joint steel bar is welded by lap welding or rod welding. [0027] Preferably, in step 1) and step 2), the concreting may be conducted at 5°C to 35°C; and after step 2) is completed, the longitudinal wet joint of the prefabricated RC beams in non-negative bending moment areas may be concreted from a mid-span to a fulcrum.

[0028] The present disclosure has the following beneficial effects: [0029] 1) In the present disclosure, the polyvinyl alcohol fiber improves a frost resistance of the cement-based material, such that the cement-based material still has a desirable crack resistance in the cold northern regions. This treatment can prolong a service life of the RC continuous beam bridge, and has desirable economic and social benefits.

[0030] 2) In the antifreezing and high-ductility cement-based material, fly ash is used as a main material, which can replace the cement by up to 60%, reducing the serious environmental pollution caused by stacking of the fly ash. Therefore, the cement-based material is an environmental-protection material.

[0031] 3) The antifreezing and high-ductility cement-based material is characterized by expansion with fine and multiple cracks under the action of tensile stress, and has a crack width under the ultimate load controlled within 90 pm. Therefore, the material can effectively reduce penetration of harmful ions such as chloride ions, prolong an initial rust time of steel bars, and reduce a corrosion rate of the steel bars; the material can also improve a crack resistance and a corrosion resistance of the negative bending moment area, enhance a fatigue resistance of the negative bending moment area, and improve a service life of the continuous beam bridge.

[0032] 4) In the present disclosure, a structural form of the negative bending moment area of the RC continuous beam bridge has an extremely strong anti-fatigue performance, thereby significantly reducing maintenance, repair and inspection costs of the bridge in a later stage.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1 shows a schematic diagram of a "one binding beam with three span beams" structure of an RC continuous beam bridge of the present disclosure; where 1 shows a prefabricated RC beam, 2 shows a prestressed tendon, 3 shows a prestressed steel cable, 4 shows a transverse wet joint of the negative bending moment area, 6 shows a bridge pier, and 14, 2#, 34, and 4# show different pier tops; [0034] FIG. 2 shows a sectional view of the RC continuous beam bridge of the present disclosure; where 1 shows the prefabricated RC beam, 2 shows the prestressed tendon, 3 shows the prestressed steel cable, 4 shows the transverse wet joint of the negative bending moment area, 5 shows a permanent support, 6 shows the bridge pier, 7 shows a temporary support, and 8 shows a scabbling part; and [0035] FIG. 3 shows a schematic diagram of a structure of a negative bending moment area of the RC continuous beam bridge of the present disclosure; where 1 shows the prefabricated RC beam, 4 shows the transverse wet joint of the negative bending moment area, and 6 shows the bridge pier.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] The present disclosure provides an antifreezing and high-ductility cement-based material, including a cement, high-calcium fly ash, quartz sand, a water reducer, a thickener, a defoamer, a polyvinyl alcohol fiber, and water; where [0037] the cement, the high-calcium fly ash, the quartz sand, and the water have a mass ratio of (280-350):(680-760):(640-720):(200-280); [0038] the water reducer, the thickener, and the defoamer have a mass ratio of (l-1.5):(0.1-0.2):(0.8-l.6); [0039] the cement and the water reducer have a mass ratio of 100:(3-5.2); and [0040] the polyvinyl alcohol fiber is 2% to 2.5% of a total volume of the cement-based material. [0041] In the present disclosure, the cement is preferably a Portland cement with a strength grade of preferably 42.5R.

[0042] In the present disclosure, the cement, the high-calcium fly ash, the quartz sand, and water have a mass ratio of preferably (290-340):(690-750):(650-700):(210-270), more preferably (300-330):(700-740):(660-690):(220-260), and further more preferably (310-320):(710-730):(670-680):(230-250).

[0043] In the present disclosure, the water reducer, the thickener, and the defoamer have a mass ratio of preferably (1.1-1.4):(0.12-0.18):(0.9-1.5). more preferably (1.2-1.3):(0.14-0.16):(1-1.4), and further more preferably 1.25:0.15:(1.2-1.3).

[0044] In the present disclosure, the cement and the water reducer have a mass ratio of preferably 100:(3.2-5), more preferably 100:(3.5-4.5), and further more preferably 100:(3.8-4.2). [0045] In the present disclosure, the polyvinyl alcohol fiber is preferably 2.1% to 2.4%, more preferably 2.2% to 2.3%, and further more preferably 2.25% of a total volume of the cement-based material.

[0046] In the present disclosure, the high-calcium fly ash is a waste produced by coal combustion, has a particle size of preferably less than or equal to 70 pm, more preferably less than or equal to 60 mn, and further more preferably less than or equal to 50 [tm, and has a free CaO content of preferably greater than or equal to 18%.

[0047] In the present disclosure, the quartz sand has a particle size of preferably 0.075 mm to 0.125 mm, more preferably 0.085 mm to 0.115 mm, and further more preferably 0.1 mm to 0.11 mm.

[0048] In the present disclosure, the water reducer is preferably a polycarboxylate water reducer, more preferably a modified polycarboxylate Sika-III water reducer; the thickener is preferably hydroxypropyl methylcellulosc, more preferably MK-100000S hydroxypropyl methylcellulose. [0049] In the present disclosure, quality indexes of the water reducer, the thickener, and the defoamer each meet standard requirements of "Concrete Admixtures" (GB 8076-2008).

[0050] In the present disclosure, the polyvinyl alcohol fiber is preferably KHTM Kuralen; the material is specially treated on a surface, has a high strength, desirable elastic modulus, wear resistance, and excellent acid and alkali resistance, and has desirable affinity and bonding with cement, fly ash and other cementitious materials.

[0051] In the present disclosure, the polyvinyl alcohol fiber has a density of preferably 1 g/cm3 to 1.5 g/cm3, more preferably 1.1 g/cm3 to 1.4 g/cm3, and further more preferably 1.2 g/cm3 to 1.3 g/cm3, a diameter of preferably 0.03 mm to 0.05 mm, more preferably 0.035 mm to 0.045 mm and further more preferably 0.04 mm, a length of 10 mm to 14 mm more preferably 11 mm to 13 mm, and further more preferably 12 mm, a fineness of preferably 13 dtex to 17 dtex, more preferably 14 dtex to 16 dtex, and further more preferably 15 dtex, an elongation of preferably 4% to 8%, more preferably 5% to 7%, and further more preferably 6%, a tensile strength of preferably 1,500 MPa to 1,700 MPa, more preferably 1,550 MPa to 1,650 MPa, and further more preferably 1,600 MPa, and an elastic modulus of preferably 35 GPa to 45 GPa, more preferably 37 GPa to 42 GPa, and further more preferably 39 GPa to 40 GPa.

[0052] In the present disclosure, the polyvinyl alcohol fiber doped into the antifreezing and high-ductility cement-based material is a synthetic fiber made of high-quality polyvinyl alcohol with high degree of polymerization as a raw material and processed by advanced technologies such as dry spinning and wet spinning. The doped polyvinyl alcohol fiber greatly improves a frost resistance of the cement-based material, thereby solving a greatly reduced service life of concrete equipment in northern severe cold areas due to low-temperature freezing and thawing. [0053] In the present disclosure, the antifreezing and high-ductility cement-based material has uniaxi al tensile strain of more than 3% (300 times that of ordinary concretes), is characterized by expansion with fine and multiple cracks under the action of tensile stress, and has a crack width under the ultimate load controlled within 90 pm. The cracks can effectively resist the penetration of chloride ions and are called "harmless cracks".

[0054] The present disclosure further provides a preparation method of the antifreezing and high-ductility cement-based material, including the following steps: [0055] 1) mixing the cement, the high-calcium fly ash, the quartz sand, and the thickener to obtain a powder; [0056] 2) mixing the water reducer, the defoamer, and water to obtain a mixed solution; [0057] 3) mixing the mixed solution and the powder to obtain a paste; and [0058] 4) mixing the paste and the polyvinyl alcohol fiber to obtain the antifreezing and high-ductility cement-based material.

[0059] In the present disclosure, in step 2). the mixing is conducted for preferably 1 min to 4 min, more preferably 2 mm to 3 mm; and a uniform powder is obtained by the mixing.

[0060] In the present disclosure, in step 3), the mixing is conducted for preferably 4 min to 10 min, more preferably 3 min to 6 min by low-speed stirring, and then 1 min to 3 min by highspeed stirring, and further more preferably 4 min to 5 min by low-speed stirring, and then 2 min by high-speed stirring; in the low-speed stirring, a stirring blade has a rotation speed of preferably 135 r/min to 145 r/min, more preferably 138 r/min to 142 r/min, and further more preferably 140 r/min, and a revolution speed of preferably 57 r/min to 67 r/min, more preferably 59 r/min to 65 r/min, and further more preferably 61 r/min to 63 r/min; and in the high-speed stirring, the stirring blade has a rotation speed of preferably 275 r/min to 295 r/min, more preferably 280 r/min to 290 r/min, and further more preferably 283 r/min to 286 r/min, and a revolution speed of preferably 115 r/min to 135 r/min, more preferably 120 r/min to 130 r/min, and further more preferably 123 r/min to 125 r/min.

[0061] In the present disclosure, in step 3), the paste has desirable fluidity.

[0062] In the present disclosure, in step 4), the mixing is conducted for preferably 2 min to 6 min, more preferably 1 min to 3 min by low-speed stirring, and then 0.5 min to 2 min by highspeed stifling, and further more preferably 2 min by low-speed stifling, and then 1 min to 1.5 min by high-speed stirring; in the low-speed stirring, a stirring blade has a rotation speed of preferably 135 r/min to 145 r/min, more preferably 138 r/min to 142 r/min, and further more preferably 140 dmin, and a revolution speed of preferably 57 r/min to 67 r/min, more preferably 59 r/min to 65 r/min, and further more preferably 61 r/min to 63 r/min; and in the high-speed stirring, the stirring blade has a rotation speed of preferably 275 r/min to 295 r/min, more preferably 280 r/min to 290 r/min, and further more preferably 283 r/min to 286 r/min, and a revolution speed of preferably 115 r/min to 135 r/min, more preferably 120 r/min to 130 r/min, and further more preferably 123 r/min to 125 r/min.

[0063] The present disclosure further provides use of the cement-based material in a negative bending moment area of an RC continuous beam bridge, where the RC continuous beam bridge includes a prefabricated RC beam (1), a prestressed tendon (2), a prestressed steel cable (3), a transverse wet joint of the negative bending moment area (4), a permanent support (5), a bridge pier (6), a temporary support (7), and a scabbling part (8).

[0064] In the present disclosure, FIG. 1 shows a schematic diagram of a "one binding beam with three span beams" structure of an RC continuous beam bridge; where 1 shows a prefabricated RC beam, 2 shows a prestressed tendon, 3 shows a prestressed steel cable, 4 shows a transverse wet joint of the negative bending moment area, 6 shows a bridge pier, and 1#, 2#, 3#, and 4# show different pier tops.

[0065] In the present disclosure. FIG. 2 shows a sectional view of the RC continuous beam bridge; where 1 shows the prefabricated RC beam, 2 shows the prestressed tendon, 3 shows the prestressed steel cable, 4 shows the transverse wet joint of the negative bending moment area, 5 shows a permanent support, 6 shows the bridge pier, 7 shows a temporary support, and 8 shows a scab bling part.

[0066] In the present disclosure, FIG. 3 shows a schematic diagram of a structure of a negative bending moment area of the RC continuous beam bridge; where 1 shows the prefabricated RC beam, 4 shows the transverse wet joint of the negative bending moment area and 6 shows the bridge pier.

[0067] The present disclosure further provides a method for concreting a negative bending moment area of an RC continuous beam bridge using the antifreezing and high-ductility cement-based material, including the following steps: [0068] 1) concreting transverse wet joints at tops of 14 and 34 continuous piers and a longitudinal wet joint in the negative bending moment area with the antifreezing and high-ductility cement-based material, followed by tensioning the prestressed steel cable in the negative bending moment area and conducting duct grouting sequentially; and [0069] 2) concreting transverse wet joints at tops of 24 and 44 continuous piers and the longitudinal wet joint in the negative bending moment area with the antifreezing and high-ductility cement-based material, followed by tensioning the prestressed steel cable in the negative bending moment area and conducting duct grouting sequentially.

[0070] In the present disclosure, in step 1), the method further includes preferably the following steps before the concreting: i, erecting the prefabricated RC beam, and welding connectors; and ii, laying a diaphragm plate formwork, welding steel bars of a diaphragm plate and protrusion steel bars of the prefabricated RC beam in sequence, and concreting in the diaphragm plate formwork; where [0071] the connector includes preferably a longitudinal wet joint, a diaphragm plate, and a transverse wet joint steel bar; and the transverse wet joint steel bar is welded preferably by lap welding or rod welding.

[0072] In the present disclosure, before the prefabricated RC beam is erected, prestressing construction is preferably completed in a positive bending moment area; ordinary concrete is concreted in the diaphragm plate formwork, and layered vibration is required during concreting to improve a density of the ordinary concrete; then, preferably steel cable corrugated pipes of the transverse wet joint are installed and the steel cables are threaded, and steel strand threading and corrugated pipe threading of the transverse wet joint are preferably performed at the same time; a connection between the steel cable corrugated pipes of the transverse wet joint and reserved corrugated pipes of the prefabricated beam is preferably wrapped with waterproof tape to ensure tight connection to prevent slurry leakage during grouting.

[0073] In the present disclosure, the duct grouting is preferably conducted with cement slurry, and the cement slurry is preferably C50 cement slurry; and the cement slurry is preferably grouted fully.

[0074] In the present disclosure, the welding of steel bars on the transverse wet joint is an important step in the construction of transverse wet joint.

[0075] In the present disclosure, before thc transverse wet joint is on site concreted, the prefabricated RC beam is preferably thoroughly scabbled and washed with a high-pressure water gun to ensure a desirable connection between the cement-based material and the prefabricated RC beam; the transverse wet joint is concreted after a whole binding beam is completed.

[0076] In the present disclosure, in step 1), the concreting is conducted at preferably 5°C to 35°C, more preferably 10°C to 30°C, and further more preferably 15°C to 20°C.

[0077] In the present disclosure, after the concreting reaches a design strength, preferably the tensioning the prestressed steel cable in the negative bending moment area and conducting duct grouting are conducted sequentially; the tensioning the prestressed steel cable in the negative bending moment area is preferably conducted by tensioning simultaneously from both ends in a symmetrical manner, and during the tensioning, prestress and elongation are preferably controlled simultaneously; the duct grouting is conducted by preferably a grouting method.

[0078] In the present disclosure, in step 2), the concreting is conducted at preferably 5°C to 35°C, more preferably 10°C to 30°C, and further more preferably 15°C to 20°C; and in step 2), methods for concreting the cement-based material, the tensioning the prestressed steel cable in the negative bending moment area and conducting duct grouting are exactly the same as those in step 1).

[0079] In the present disclosure, in step 1) and step 2), the continuous joints are concreted at an air temperature difference of preferably 3°C to 8°C, more preferably 4°C to 6°C, more preferably 5°C. Preferably, all transverse wet joints of a binding beam should be concreted at one time; it is forbidden to walk and carry sundries on the bridge deck within 3 d to avoid cracking in the negative bending moment area due to excessive disturbance.

[0080] In the present disclosure, after step 2) is completed, preferably the longitudinal wet joint of the prefabricated RC beams in non-negative bending moment areas is concreted preferably from a mid-span to a fulcrum; during the concreting, the concrete of transverse wet joint is preferably plastered preferably 2 times.

[0081] In the present disclosure, the anti freeting and high-ductility cement-based material is preferably premixed evenly before being transported to the construction site for cast-in-place. [0082] In the present disclosure, in step 1) and step 2), when tensioning the prestressed steel cables in the negative bending moment area, a tensile strength is strictly controlled according to the requirements of design and specification; before tensioning the prestressed steel cables, cleaning and threading prestressed steel strands are performed preferably in sequence; the cleaning is preferably cleaning prestressed ducts and blowing the ducts with high-pressure air. [0083] The technical solution provided by the present disclosure will be described in detail below with reference to examples, but they should not be construed as limiting the protection scope of the present disclosure.

[0084] Example 1

[0085] 2,900 g of a Portland cement (with a strength grade of 42.5R), 6,900 g of high-calcium fly ash (with a particle size of < 65 um), 6,500 g of quartz sand (with a particle size of 0.08 mm), and MK-100000S hydroxypropyl methylcellulose were stirred and mixed for 2 min to obtain a uniform powder. A modified polycarboxylate Sika-III water reducer and a JXPT-1206 defoamer were stirred and mixed uniformly in water to obtain a mixed solution. The modified polycarboxylate water reducer, the defoamer, and the hydroxypropyl methylcellulose had a mass ratio of 1.1:0.1:0.9; and the modified polycarboxylate water reducer and the cement had a mass ratio of 3.5:100. The powder was stirred at low speed for 3 min (a stirring blade had a rotation speed of 137 r/min, and a revolution speed of 59 r/min) and then stirred at high speed for 1.5 min (the stirring blade had a rotation speed of 278 r/min, and a revolution speed of 118 r/min) in the mixed solution to obtain a paste. A polyvinyl alcohol fiber was added to the paste, and was stirred at low speed for 1.5 min (a stirring blade had a rotation speed of 137 r/min, and a revolution speed of 59 r/min) and then stirred at high speed for 1 min (the stirring blade had a rotation speed of 278 r/min, and a revolution speed of 118 r/min) to obtain an antifreezing and high-ductility cement-based material. The polyvinyl alcohol fiber accounted for 2% of a total volume of the cement-based material. The polyvinyl alcohol fiber had a density of 1.1 g/cms, a diameter of 0.035 mm, a length of 11 mm, a fineness of 14 dtex, an elongation of 5%, a tensile strength of 1,550 MPa, and an elastic modulus of 37 GPa.

[0086] Example 2

[0087] 3,400 g of a Portland cement (with a strength grade of 42.5R), 7,500 g of high-calcium fly ash (with a particle size of < 55 tun), 7,100 g of quartz sand (with a particle size of 0.12 mm) and MK-100000S hydroxypropyl methylcellulose were stirred and mixed for 3 min to obtain a uniform powder. A modified polycarboxylate Sika-III water reducer and a JXPT-1206 defoamer were stirred and mixed uniformly in water to obtain a mixed solution. The modified polycarboxylate water reducer, the defoamer, and the hydroxypropyl methylcellulose had a mass ratio of 1.5:0.2:1.5; and the modified polycarboxylate water reducer and the cement had a mass ratio of 5:100. The powder was stirred at low speed for 5 min (a stirring blade had a rotation speed of 144 r/min, and a revolution speed of 66 r/min), and then stirred at high speed for 3 min (the stirring blade had a rotation speed of 293 r/min, and a revolution speed of 132 r/min) in the mixed solution to obtain a paste. A polyvinyl alcohol fiber was added to the paste, and was stirred at low speed for 3min (a stirring blade had a rotation speed of 143 r/min, and a revolution speed of 65 r/min), and then stirred at high speed for 1 5min (the stirring blade had a rotation speed of 292 r/min, and a revolution speed of 132 r/min) to obtain an antifreezing and high-ductility cement-based material. The polyvinyl alcohol fiber accounted for 2.5% of a total volume of the cement-based material. The polyvinyl alcohol fiber had a density of 1.4 g/cm3, a diameter of 0.045 mm, a length of 13 mm, a fineness of 16 dtex, an elongation of 7%, a tensile strength of 1,650 MPa, and an elastic modulus of 42 GPa.

[0088] Example 3

[0089] 3,100 g of a Portland cement (with a strength grade of 42.5R), 7,200 g of high-calcium fly ash (with a particle size of < 50 pm), 6,800 g of quartz sand (with a particle size of 0.1 mm) and MK-100000S hydroxypropyl methylcellulose were stirred and mixed for 2 min to obtain a uniform powder. A modified polycarboxylate Sika-III water reducer and a JXPT-1206 defoamcr were stirred and mixed uniformly in water to obtain a mixed solution. The modified polycarboxylate water reducer, the defoamer, and the hydroxypropyl methylcellulose had a mass ratio of 1.25:0.15:1.2; and the modified polycarboxylate water reducer and the cement had a mass ratio of 4.3:100. The powder was stirred at low speed for 4 min (a stirring blade had a rotation speed of 140 r/min, and a revolution speed of 62 r/min) and then stirred at high speed for 2 min (the stirring blade had a rotation speed of 285 r/min, and a revolution speed of 125 r/min) in the mixed solution to obtain a paste. A polyvinyl alcohol fiber was added to the paste, and was stirred at low speed for 2 min (a stirring blade had a rotation speed of 140 r/min, and a revolution speed of 62 r/min), and then stirred at high speed for 1 mm (the stirring blade had a rotation speed of 285 r/min, and a revolution speed of 125 r/min) to obtain an antifreezing and high-ductility cement-based material. The polyvinyl alcohol fiber accounted for 2.2% of a total volume of the cement-based material. The polyvinyl alcohol fiber had a density of 1.3 g/cm3, a diameter of 0.04 mm, a length of 12 mm, a fineness of 15 dtex, an elongation of 6%, a tensile strength of 1,600 MPa, and an elastic modulus of 40 GPa.

[0090] Example 4

[0091] A prefabricated RC beam that had completed prestressing construction in a positive bending moment area was erected, and longitudinal wet joints, diaphragm plates, and steel bars of transverse wet joints are welded, where the steel bars of transverse wet joints were lap-welded. Diaphragm plate formworks were laid, steel bars of the diaphragm plates were welded to protrusion steel bars of the prefabricated RC beam, and cast-in-place concreting was conducted on the formworks, followed by conducting layered vibration. Steel cable corrugated pipes of the transverse wet joint were installed and the steel cables were threaded; a connection between the steel cable corrugated pipes of the transverse wet joint and reserved corrugated pipes of the prefabricated beam was wrapped well with waterproof tape to ensure tight connection to prevent slurry leakage during grouting.

[0092] The prefabricated RC beam was thoroughly scabbled and washed with a high-pressure water gun; the transverse wet joint was concreted after a whole binding beam was completed. The transverse wet joints were concreted at tops of 14 and 34 continuous piers and a longitudinal wet joint in the negative bending moment area with the antifreezing and high-ductility cement-based material of Example 1 at 8°C. all the transverse wet joints in a binding beam were concreted at one time; after reaching a design strength, a single prestressed steel cable in the negative bending moment area was simultaneously tensioned from both ends in a symmetrical manner; and a C50 cement is subjected to duct grouting by a grouting method. The transverse wet joints were concreted at tops of 24 and 44 continuous piers and a longitudinal wet joint in the negative bending moment area with the antifreezing and high-ductility cement-based material of Example 1 at 8°C, and the rest steps were exactly the same as those of 14 and 34. The longitudinal wet joint of the prefabricated RC beams in non-negative bending moment areas was concreted from a mid-span to a fulcrum; during the concreting, the concrete of transverse wet joint was plastered 2 times.

[0093] Example 5

[0094] In Example 4, the antifreezing and high-ductility cement-based material was changed to the cement-based material of Example 2, a concreting temperature was changed from 8°C to 30°C: and other conditions were the same as those in Example 4.

[0095] Example 6

[0096] In Example 4, the antifreezing and high-ductility cement-based material was changed to the cement-based material of Example 3, a concreting temperature was changed from 8°C to 22°C; and other conditions were the same as those in Example 4.

[0097] In Examples 1 to 3, each antifreezing and high-ductility cement-based material is characterized by expansion with fine and multiple cracks under the action of tensile stress, and has a crack width under the ultimate load controlled within 90 pm. Therefore, the material can effectively reduce penetration of harmful ions such as chloride ions, prolong an initial rust time of steel bars, and reduce a corrosion rate of the steel bars; the material can also improve a crack resistance and a corrosion resistance of the negative bending moment area, enhance a fatigue resistance of the negative bending moment area, and improve a service life of the continuous beam bridge.

[0098] In the present disclosure, a structural form of the negative bending moment area of the RC continuous beam bridge has an extremely strong anti-fatigue performance, thereby significantly reducing maintenance, repair and inspection costs of the bridge in a later stage. [0099] The above descriptions are merely preferred implementations of the present disclosure. It should be noted that a person of ordinary skill in the art may further make several improvements and modifications without departing from the principle of the present disclosure as defined by the scope of the appended claims.

Claims

WHAT IS CLAIMED IS: I. An antifreezing and high-ductility cement-based material, comprising a cement, high-calcium fly ash, quartz sand, a water reducer, a thickener, a defoamer, a polyvinyl alcohol fiber, and water; wherein the cement, the high-calcium fly ash, the quartz sand, and the water have a mass ratio of (280-350):(680-760):(640-720):(200-280); the water reducer, the thickener, and the defoamer have a mass ratio of (1-1.5):(0.1-0.2):(0.8-1.6); the cement and the water reducer have a mass ratio of 100:(3-5.2); and the polyvinyl alcohol fiber is 2% to 2.5% of a total volume of the cement-based material.
2. The cement-based material according to claim 1, wherein the cement is a Portland cement; the high-calcium fly ash has a particle size of less than or equal to 70 pm; and the quartz sand has a particle size of 0.075 mm to 0.125 mm.
3. The cement-based material according to claim 1 or 2, wherein the water reducer is a polycarboxylatc water reducer; and the thickener is hydroxypropyl methylcellulose.
4. The cement-based material according to claim 3, wherein the polyvinyl alcohol fiber has a density of 1 gicm3 to 1.5 g/cm3, a diameter of 0.03 mm to 0.05 mm, a length of 10 mm to 14 mm, a fineness of 13 dtex to 17 dtex, an elongation of 4% to 8%, a tensile strength of 1,500 MPa to 1,700 MPa, and an elastic modulus of 35 GPa to 45 GPa.
5. A preparation method of the antifreezing and high-ductility cement-based material according to any one of claims 1 to 4, comprising the following steps: 1) mixing the cement, the high-calcium fly ash, the quartz sand, and the thickener to obtain a powder; 2) mixing the water reducer, the defoamer, and water to obtain a mixed solution; 3) mixing the mixed solution and the powder to obtain a paste; and 4) mixing the paste and the polyvinyl alcohol fiber to obtain the antifreezing and high-ductility cement-based material.
6. The preparation method according to claim 5, wherein the mixing is conducted for 1 min to 4 min in step 2), for 4 min to 10 min in step 3), and for 2 min to 6 min in step 4).
7. Use of the cement-based material according to any one of claims 1 to 4 in a negative bending moment area of a reinforced concrete (RC) continuous beam bridge, wherein the RC continuous beam bridge comprises a prefabricated RC beam (1), a prestressed tcndon (2), a prestressed steel cable (3), a transverse wet joint of the negative bending moment area (4), a permanent support (5), a bridge pier (6), a temporary support (7), and a scabbling part (8).
8. A method for concreting a negative bending moment area of an RC continuous beam bridge using the antifreezing and high-ductility cement-based material according to any one of claims I to 4, comprising the following steps: I) concreting transverse wet joints at tops of l# and 31t continuous piers and a longitudinal wet joint in the negative bending moment area with the antifreezing and high-ductility cement-based material, followed by tensioning the prestressed steel cable in the negative bending moment area and conducting duct grouting sequentially; and 2) concreting transverse wet joints at tops of 2# and 4# continuous piers and the longitudinal wet joint in the negative bending moment area with the antifreezing and high-ductility cement-based material, followed by tensioning the prestressed steel cable in the negative bending moment area and conducting duct grouting sequentially.
9. The method according to claim 8, wherein in step 1), the method further comprises the following steps before the concreting: i, erecting the prefabricated RC beam, and welding connectors; and ii, laying a diaphragm plate formwork, welding steel bars of a diaphragm plate and protrusion steel bars of the prefabricated RC beam in sequence, and concreting in the diaphragm plate formwork; wherein the connector comprises a longitudinal wet joint, a diaphragm plate, and a transverse wet joint steel bar; and the transverse wet joint steel bar is welded by lap welding or rod welding.
10. The method according to claim 8 or 9, wherein in step 1) and step 2), the concreting is conducted at 5°C to 35°C; and after step 2) is completed, the longitudinal wet joint of the prefabricated RC beams in non-negative bending moment areas is concreted from a mid-span to a fulcrum.