Low shrinkage mass concrete for bridge pier

Abstract

The application discloses a low-shrinkage mass concrete for bridge pier, which comprises the following raw materials by weight: low-shrinkage low-heat Portland cement: 250-350 kg / m 3 ; fly ash: 50-100 kg / m 3 ; early hardening expansive agent: 6-23 kg / m 3 ; gravel: 920-1120 kg / m 3 ; machine-made sand: 700-850 kg / m 3 ; powdered polycarboxylic acid water reducing agent: 1.0-1.5 kg / m 3 ; and water: 130-160 kg / m 3 . The low-shrinkage mass concrete for bridge pier can reduce the hydration heat and self-shrinkage of the concrete, prevent cracking and prolong the durability of the concrete.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and specifically to a low-shrinkage, large-volume concrete for bridge piers and abutments. Background Technology

[0002] Bridge piers and abutments are widely used in railways and highways in my country, and most are constructed primarily of reinforced concrete and large-volume concrete. During the pouring of large-volume concrete, the internal temperature of the concrete rises significantly. During the temperature drop, the concrete structure is subjected to both internal and external constraints. Furthermore, concrete has a low modulus of elasticity. When the early tensile strength of the structure is lower than the tensile stress generated by the shrinkage of the concrete under these constraints, cracks will occur. Additionally, the large-volume concrete used in bridge piers and abutments is typically designed with a high strength grade, and the autogenous shrinkage of concrete is directly proportional to the amount of cement used. Therefore, the autogenous shrinkage of concrete is one of the main driving forces behind the formation of cracks in the large-volume concrete of bridge piers and abutments.

[0003] To address the technical problems of high heat of hydration, easy shrinkage, and cracking in mass concrete, patent publication number CN2022210797459.3, entitled "A Low-Shrinkage, Freeze-Temperature Resistant Mass Concrete," utilizes early-strength, low-heat-of-hydration silicate cement, combined with fly ash, admixtures, and aggregates with low thermal expansion coefficients to prepare concrete. This reduces the heat of hydration, shrinkage, and cracking in mass concrete, improves freeze-thaw resistance, and extends the service life of mass concrete. However, in its embodiments, the 3-day heat of hydration of the early-strength, low-heat-of-hydration silicate cement used is mostly greater than 220 kJ / kg, and the clinker saturation ratio is high; no reports have been made on the auto-shrinkage of the concrete. Patent publication number CN201811323941.3, entitled "A Low-Shrinkage, Low-Creep, Crack-Resistant, High-Performance Mass Concrete," utilizes ordinary silicate cement, grade I fly ash, granite crushed stone, and granite manufactured sand to prepare mass concrete. The significant feature of this invention is that the concrete mix requires no special mixing process, is easy to mix, and the order of adding materials can be changed. The concrete mixture has moderate viscosity and good cohesion, resulting in good crack resistance, low shrinkage and creep, and good volume stability. It is suitable for use in the construction of large-volume concrete with high-strength stress and complex conditions, reducing the probability of crack formation. However, this patent uses ordinary silicate cement, and the durability of the large-volume concrete has not been reported.

[0004] Therefore, the present invention provides a low-shrinkage, large-volume concrete for bridge piers and abutments, which reduces the heat of hydration and autogenous shrinkage of concrete, prevents cracking, and extends the durability of concrete. Summary of the Invention

[0005] The purpose of this invention is to provide a low-shrinkage, large-volume concrete for bridge piers and abutments, wherein the cementitious materials used include low-shrinkage, low-heat silicate cement, early-hardening expansion agent, and fly ash, which are used to reduce the heat of hydration and autogenous shrinkage of the large-volume concrete, prevent cracking, and extend the durability of the concrete.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] The present invention provides a low-shrinkage, large-volume concrete for bridge piers and abutments, comprising the following raw materials by weight:

[0008] Low-shrinkage, low-heat silicate cement: 250–350 kg / m³ 3 ;

[0009] Fly ash: 50-100 kg / m³ 3 ;

[0010] Early hardening expansion agent: 6-23 kg / m 3 ;

[0011] Crushed stone: 920~1120kg / m 3 ;

[0012] Manufactured sand: 700~850kg / m³ 3 ;

[0013] Powdered polycarboxylate superplasticizer: 1.0~1.5kg / m² 3 ;

[0014] Water: 130~160kg / m 3 .

[0015] In some embodiments of the present invention, the low-shrinkage, low-heat silicate cement is composed of 95 wt% low-shrinkage, low-heat silicate cement clinker and 5 wt% gypsum.

[0016] In some embodiments of the present invention, the low-shrinkage, low-heat silicate cement clinker has a lime saturation coefficient of 0.78 to 0.80, a silica content of 2.60 to 2.90, an aluminum content of 0.8 to 1.0, and a clinker weight per liter greater than 1.4 kg / L.

[0017] In some embodiments of the present invention, the low-shrinkage, low-heat silicate cement clinker contains 43-48 wt% C2S, 30-35 wt% C3S, 2-5 wt% C3A, 3-5 wt% MgO, 1.0-1.5 wt% SO3, and the remainder is C4AF.

[0018] In some embodiments of the present invention, the low-shrinkage and low-heat silicate cement clinker is prepared by using limestone, high-magnesium limestone, quartz sand chips, non-ferrous metal ash slag, and mineralizer as raw meal, and the raw meal is then calcined at 1350-1400℃.

[0019] During the production process, the batching values ​​of limestone, high-magnesium limestone, quartz sand fragments, non-ferrous metal slag, and mineralizing agent vary depending on the composition of each material, so there is no specific batching ratio.

[0020] In some embodiments of the present invention, the mineralizer is composed of 30 wt% steel slag, 30 wt% petroleum coke ash, 30 wt% low-heat silicate cement clinker and 10 wt% tailings; preferably, the SO3 content in the petroleum coke ash is greater than 30 wt%.

[0021] In some embodiments of the present invention, the specific surface area of ​​the low-shrinkage, low-heat silicate cement is 320–340 m². 2 / kg, cement 3d heat of hydration ≤215kJ / kg, 3d compressive strength ≥15MPa, 28d compressive strength ≥48MPa.

[0022] In some embodiments of the present invention, the particle size distribution of the low-shrinkage, low-heat silicate cement is as follows: ≤3μm particles account for 6-9%, 3-32μm particles account for 73-78%, 32-65μm particles account for 12-20%, ≥65μm particles account for 0-1%, and the uniformity coefficient is 0.94-0.96.

[0023] In some embodiments of the present invention, the early hardening expansion agent is made by calcining limestone, sandstone, aluminum ore waste rock, and petroleum coke ash at a high temperature of 1230-1290°C for 45 minutes, and then grinding it by ball milling.

[0024] During the production process, the batching values ​​of limestone, sandstone, aluminum ore waste rock, and petroleum coke ash vary depending on the composition of each material, so there is no specific batching ratio.

[0025] In some embodiments of the present invention, the early hardening expansion agent comprises 5-12 wt% anhydrous calcium sulfoaluminate, 20-46 wt% C2S, 32-51 wt% CaO and 1-3 wt% high-temperature gypsum.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. This invention reduces cement auto-shrinkage and heat of hydration by controlling the content of C3S and C3A in low-shrinkage, low-heat silicate cement clinker.

[0028] 2. The iron element in the steel slag, the sulfur element in the petroleum coke ash, and the metallic elements in the tailings of the mineralizer in this invention can cause lattice distortion, grain refinement, and an increase in grain boundary defects in C2S, resulting in some C2S existing in α and α' crystal forms, thus activating belite hydration activity. Furthermore, during the raw material calcination process, the low-heat silicate cement clinker in the mineralizer can act as nucleation sites for C2S, lowering the calcination temperature and promoting the firing of C2S and stabilizing high-temperature C2S.

[0029] 3. In the grinding process of the low-shrinkage and low-heat silicate cement of the present invention, the specific surface area, particle size distribution and uniformity coefficient of cement are comprehensively considered, which reduces the water demand of cement and the 28-day shrinkage value, thereby reducing concrete shrinkage.

[0030] 4. This invention reduces the autogenous shrinkage of concrete by incorporating a suitable early-hardening expansive agent. The CaO particles in the early-hardening expansive agent are approximately 10–20 μm in size. Upon hydration, they generate Ca(OH)₂, undergoing primary expansion. Ca(OH)₂ then reacts with anhydrous calcium sulfoaluminate and high-temperature gypsum to form ettringite, resulting in secondary expansion. The coordinated composition of the minerals in the early-hardening expansive agent compensates for the autogenous shrinkage caused by cement hydration.

[0031] 5. In the low-shrinkage, low-heat silicate cement of this invention, during the clinker calcination process, some MgO is dissolved in the clinker minerals and glass, while the remaining MgO exists as periclase. In the later stage of cement hydration, periclase reacts with water to generate Mg(OH)2, which plays a role in the later stage of hydration expansion and compensates for the drying shrinkage of concrete. Attached Figure Description

[0032] Figure 1 This is a mineral and petrographic diagram of the low-shrinkage, low-heat silicate cement clinker of the present invention.

[0033] Figure 2 This is a SEM image of the early hardening expansion agent of this invention. Detailed Implementation

[0034] Figure 1 This is a mineral and petrographic diagram of the low-shrinkage, low-heat silicate cement clinker of this invention. From... Figure 1 It can be seen that the grain size of C2S is between 20μm and 30μm, and it is round with clear and smooth boundaries and bicrystalline striations on the surface.

[0035] Figure 2 This is a SEM (scanning electron microscope) image of the early-stage hardening expansion agent of this invention. From... Figure 2It is evident that the CaO particle size is 10 μm, while the anhydrous calcium sulfoaluminate particle size is only 1 μm. In this system, CaO is a pre-hydrated mineral, belonging to an in-situ reaction. The generated Ca(OH)2 undergoes primary expansion, and then, together with anhydrous calcium sulfoaluminate and high-temperature gypsum, it forms ettringite, undergoing secondary expansion. The ettringite is formed through a dissolution and crystallization reaction.

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0037] In this embodiment of the invention, the mineralizer is composed of 30 wt% steel slag, 30 wt% petroleum coke ash, 30 wt% low-heat silicate cement clinker and 10 wt% tailings, wherein the tailings are gold tailings.

[0038] In this embodiment of the invention, the specific surface area of ​​the low-shrinkage, low-heat silicate cement is 320–340 m². 2 / kg.

[0039] In this embodiment of the invention, the particle size distribution of the low-shrinkage, low-heat silicate cement is as follows: ≤3μm particles account for 6-9%, 3-32μm particles account for 73-78%, 32-65μm particles account for 12-20%, ≥65μm particles account for 0-1%, and the uniformity coefficient is 0.94-0.96.

[0040] Example 1

[0041] As a preferred embodiment of the present invention, this embodiment discloses a low-shrinkage, high-volume concrete for bridge piers, comprising the following raw materials by weight:

[0042] Low-shrinkage, low-heat silicate cement: 350 kg / m³ 3 ;

[0043] Fly ash: 50kg / m³ 3 ;

[0044] Early hardening expansion agent: 23kg / m 3 ;

[0045] Crushed stone: 1120kg / m 3 ;

[0046] Manufactured sand: 700 kg / m³ 3 ;

[0047] Powdered polycarboxylate superplasticizer: 1.5 kg / m³ 3 ;

[0048] Water: 160kg / m 3 .

[0049] The low-shrinkage, low-heat silicate cement in this embodiment is composed of 95 wt% low-shrinkage, low-heat silicate cement clinker and 5 wt% gypsum.

[0050] In this embodiment, the lime saturation coefficient of the low-shrinkage, low-heat silicate cement clinker is 0.788, the silica ratio is 2.71, the aluminum ratio is 0.98, and the clinker weight per liter is 1.42 kg / L.

[0051] In this embodiment, the low-shrinkage, low-heat silicate cement clinker contains 45.96 wt% C2S, 32.16 wt% C3S, 4.06 wt% C3A, 4.0 wt% MgO, 1.1 wt% SO3, and 12.72 wt% C4AF.

[0052] In this embodiment, the low-shrinkage, low-heat silicate cement clinker is prepared by using limestone, quartz sand fragments, non-ferrous metal ash slag, and mineralizer as raw meal, which is then calcined in a rotary kiln at 1350℃~1400℃.

[0053] In this embodiment, the early hardening expansion agent is made by calcining limestone, sandstone, aluminum ore waste rock, and petroleum coke ash at 1260℃ for 45 minutes, and then grinding it into powder by ball milling.

[0054] The early hardening expansion agent in this embodiment contains 9 wt% anhydrous calcium sulfoaluminate, 46 wt% C2S, 40 wt% CaO and 2 wt% high-temperature gypsum.

[0055] Example 2

[0056] As a preferred embodiment of the present invention, this embodiment discloses a low-shrinkage, high-volume concrete for bridge piers, comprising the following raw materials by weight:

[0057] Low-shrinkage, low-heat silicate cement: 250 kg / m³ 3 ;

[0058] Fly ash: 100kg / m³ 3 ;

[0059] Early hardening expansion agent: 15kg / m 3 ;

[0060] Crushed stone: 920kg / m 3 ;

[0061] Manufactured sand: 850kg / m³ 3 ;

[0062] Powdered polycarboxylate superplasticizer: 1.0 kg / m³ 3 ;

[0063] Water: 130kg / m 3 .

[0064] The low-shrinkage, low-heat silicate cement in this embodiment is composed of 95 wt% low-shrinkage, low-heat silicate cement clinker and 5 wt% gypsum.

[0065] In this embodiment, the lime saturation coefficient of the low-shrinkage, low-heat silicate cement clinker is 0.794, the silica ratio is 2.60, the aluminum ratio is 1.01, and the clinker weight per liter is 1.43 kg / L.

[0066] In this embodiment, the low-shrinkage, low-heat silicate cement clinker contains 43.74 wt% C2S, 33.03 wt% C3S, 4.48 wt% C3A, 3.1 wt% MgO, 1.0 wt% SO3, and 14.65 wt% C4AF.

[0067] In this embodiment, the low-shrinkage, low-heat silicate cement clinker is prepared by using limestone, quartz sand fragments, non-ferrous metal ash slag, and mineralizer as raw meal, which is then calcined in a rotary kiln at 1350℃~1400℃.

[0068] In this embodiment, the early hardening expansion agent is made by calcining limestone, sandstone, aluminum ore waste rock, and petroleum coke ash at 1260℃ for 45 minutes, and then grinding it into powder by ball milling.

[0069] The early hardening expansion agent in this embodiment contains 5 wt% anhydrous calcium sulfoaluminate, 48 wt% C2S, 40 wt% CaO and 2.7 wt% high-temperature gypsum.

[0070] Example 3

[0071] As a preferred embodiment of the present invention, this embodiment discloses a low-shrinkage, high-volume concrete for bridge piers, comprising the following raw materials by weight:

[0072] Low-shrinkage, low-heat silicate cement: 300 kg / m³ 3 ;

[0073] Fly ash: 75kg / m³ 3 ;

[0074] Early hardening expansion agent: 6 kg / m 3 ;

[0075] Crushed stone: 1080kg / m 3 ;

[0076] Manufactured sand: 770kg / m³ 3 ;

[0077] Powdered polycarboxylate superplasticizer: 1.2 kg / m³ 3 ;

[0078] Water: 150kg / m 3 .

[0079] The low-shrinkage, low-heat silicate cement in this embodiment is composed of 95 wt% low-shrinkage, low-heat silicate cement clinker and 5 wt% gypsum.

[0080] In this embodiment, the lime saturation coefficient of the low-shrinkage, low-heat silicate cement clinker is 0.799, the silica content is 2.79, the aluminum content is 0.90, and the clinker weight per liter is 1.42 kg / L.

[0081] In this embodiment, the low-shrinkage, low-heat silicate cement clinker contains 43.46 wt% C2S, 34.97 wt% C3S, 3.13 wt% C3A, 3.4 wt% MgO, 1.3 wt% SO3, and 13.74 wt% C4AF.

[0082] In this embodiment, the low-shrinkage, low-heat silicate cement clinker is prepared by using limestone, quartz sand fragments, non-ferrous metal ash slag, and mineralizer as raw meal, which is then calcined in a rotary kiln at 1350℃~1400℃.

[0083] In this embodiment, the early hardening expansion agent is made by calcining limestone, sandstone, aluminum ore waste rock, and petroleum coke ash at 1260℃ for 45 minutes, and then grinding it into powder by ball milling.

[0084] In this embodiment, the early hardening expansion agent contains 12 wt% anhydrous calcium sulfoaluminate, 30 wt% C2S, 50 wt% CaO and 1.5 wt% high-temperature gypsum.

[0085] Comparative Example 1

[0086] In this comparative example of low-shrinkage, large-volume concrete, ordinary low-heat silicate cement was used instead of low-shrinkage, low-heat silicate cement; all other aspects were the same as in Example 1.

[0087] Comparative Example 2

[0088] In this comparative example of low-shrinkage, large-volume concrete, UEA expansive agent was used instead of early-hardening expansive agent; otherwise, it was the same as in Example 1.

[0089] Test case

[0090] The basic physical and mechanical properties, heat of hydration, and 28-day performance of the low-shrinkage and low-heat silicate cement used in Examples 1-3 were tested, and the test results are shown in Table 1.

[0091] Table 1 Physical and mechanical properties of low-shrinkage and low-heat silicate cement

[0092]

[0093] As shown in Table 1, the low-shrinkage and low-heat silicate cement used in this invention has a 3-day heat of hydration of less than 215 kJ / kg, a 28-day heat of hydration of less than 310 kJ / kg, a 3-day compressive strength of greater than 15 MPa, a 28-day compressive strength of greater than 48 MPa, and a 28-day shrinkage value of 0.03% to 0.06%.

[0094] The workability and mechanical properties of the concrete from Examples 1-3 and Comparative Examples 1-2 were tested, and the test results are shown in Table 2.

[0095] Table 2 Workability and Mechanical Properties of Concrete

[0096]

[0097] As can be seen from Table 2, the concrete strength of Example 1 is higher than that of Comparative Example 1 because the C2S hydration activity in the low-shrinkage, low-heat silicate cement is high. Compared with Comparative Example 2, the early-strength hardening expansive agent of Example 1 can significantly improve the early-age strength of concrete.

[0098] Early crack resistance, restricted expansion rate and chloride ion resistance of concrete from Examples 1-3 and Comparative Examples 1-2 were tested, and the test results are shown in Table 3.

[0099] Table 3. Early crack resistance, restricted expansion rate, and chloride ion resistance of concrete.

[0100]

[0101] As shown in Table 3, the low-shrinkage mass concrete of the present invention exhibits better shrinkage compensation performance, crack resistance, and chloride ion penetration resistance, all of which are improved compared to the comparative example. Compared to Comparative Example 1, the maximum crack width in Example 1 decreased from 0.27 mm to 0.18 mm, and the unit crack area decreased from 500 mm². 2 / m 2 dropped to 430mm 2 / m 2 From the perspective of the restricted expansion rate, the expansion rate of Example 1 at all ages was higher than that of Comparative Example 1; the electrical flux decreased from 1050C to 879C after 6 hours, a decrease of 16.3%. The results indicate that the low-shrinkage, low-heat silicate cement of this invention has good crack resistance and can significantly improve the crack resistance of concrete. Compared with Comparative Example 2, the crack width in Example 1 was narrower, the crack area was reduced, the concrete showed slight expansion after 56 days, and the electrical flux decreased by 30.7%, indicating that the early-hardening expansive agent and the expansion performance of MgO in the cement were coordinated to compensate for shrinkage.

[0102] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. That is to say, any changes or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but whose technical problems are still consistent with the present invention, should be included within the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. A low-shrinkage, large-volume concrete for bridge piers and abutments, characterized in that, Raw materials including the following weights: Low-shrinkage, low-heat silicate cement: 250~350 kg / m³ 3 ; Fly ash: 50~100 kg / m³ 3 ; Early hardening expansion agent: 6~23 kg / m 3 ; Crushed stone: 920~1120 kg / m 3 ; Manufactured sand: 700~850 kg / m³ 3 ; Powdered polycarboxylate superplasticizer: 1.0~1.5 kg / m³ 3 ; Water: 130~160 kg / m³ 3 ; The low-shrinkage, low-heat silicate cement is composed of 95 wt% low-shrinkage, low-heat silicate cement clinker and 5 wt% gypsum. The low-shrinkage, low-heat silicate cement clinker contains 43-48 wt% C2S, 30-35 wt% C3S, 2-5 wt% C3A, 3-5 wt% MgO, 1.0-1.5 wt% SO3, and the remainder is C4AF. The early hardening expansion agent contains 5-12 wt% anhydrous calcium sulfoaluminate, 20-46 wt% C2S, 32-51 wt% CaO and 1-3 wt% high-temperature gypsum.

2. The low-shrinkage, large-volume concrete for bridge piers and abutments according to claim 1, characterized in that, The low-shrinkage, low-heat silicate cement clinker has a lime saturation coefficient of 0.78 to 0.80, a silica content of 2.60 to 2.90, an aluminum content of 0.8 to 1.0, and a clinker weight per liter greater than 1.4 kg / L.

3. The low-shrinkage, large-volume concrete for bridge piers and abutments according to claim 1, characterized in that, The low-shrinkage, low-heat silicate cement clinker is prepared by using limestone, high-magnesium limestone, quartz sand fragments, non-ferrous metal ash slag, and mineralizer as raw meal, which is then calcined at 1350~1400℃.

4. The low-shrinkage, large-volume concrete for bridge piers and abutments according to claim 3, characterized in that, The mineralizer is composed of 30 wt% steel slag, 30 wt% petroleum coke ash, 30 wt% low-heat silicate cement clinker and 10 wt% tailings; the SO3 content in the petroleum coke ash is greater than 30 wt%.

5. The low-shrinkage, large-volume concrete for bridge piers and abutments according to claim 1, characterized in that, The specific surface area of ​​the low-shrinkage, low-heat silicate cement is 320~340 m². 2 / kg, cement 3d heat of hydration ≤215kJ / kg, 3d compressive strength ≥15MPa, 28d compressive strength ≥48MPa.

6. The low-shrinkage, large-volume concrete for bridge piers and abutments according to claim 1, characterized in that, The particle size distribution of the low-shrinkage, low-heat silicate cement is as follows: ≤3μm particles account for 6~9%, 3~32μm particles account for 73~78%, 32~65μm particles account for 12~20%, ≥65μm particles account for 0~1%, and the uniformity coefficient is 0.94~0.

96.

7. The low-shrinkage, large-volume concrete for bridge piers and abutments according to claim 1, characterized in that, The early hardening expansion agent is made by calcining limestone, sandstone, aluminum ore waste rock, and petroleum coke ash at a high temperature of 1230~1290℃ for 45 minutes, and then grinding it into powder by ball milling.

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