Super-early-strength disturbance-resistant coarse aggregate UHPC and preparation method thereof

Abstract

The invention relates to the technical field of concrete materials, in particular to super-early-strength disturbance-resistant coarse aggregate UHPC and a preparation method thereof. The concrete is prepared from the following raw materials in parts by weight: 350 to 700 parts of Portland cement, 120 to 240 parts of sulphoaluminate cement, 30 to 100 parts of silica fume, 30 to 70 parts of mineral powder, 30 to 70 parts of fly ash, 600 to 1000 parts of fine aggregate, 600 to 1200 parts of coarse aggregate, 2 to 7 parts of coagulation regulating component, 2 to 7 parts of high-efficiency water reducing agent and 40 to 120 parts of steel fiber. The UHPC disclosed by the invention adopts a composite system of ordinary Portland cement and sulphoaluminate cement, the sulphoaluminate cement and ordinary Portland cement are hydrated synergistically, the characteristics of quick setting, quick hardening and excellent low-temperature performance of the sulphoaluminate cement are brought into full play, the early strength of the UHPC is improved, the initial setting time is greater than 60 minutes, the final setting time is less than 90 minutes, and the compressive strength within 3 hours is greater than or equal to 30 MPa.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete materials, and more specifically to an ultra-early strength anti-disturbance coarse aggregate UHPC and a preparation method thereof. Background Art

[0002] The long-term effects of environmental erosion and fatigue loads will cause aging and damage to concrete structures, such as steel corrosion, freeze-thaw spalling, external cracking, etc., posing a threat to public safety. Especially for the repair and reinforcement of existing bridge expansion joints, wet joints and bridge deck pavement projects, the vehicle-bridge coupling vibration without interrupting traffic conditions will cause the risk of cracking of ordinary concrete repair materials. UHPC (ultra-high performance concrete) is very suitable for use as a repair material for expansion joints, wet joints and bridge deck pavement because of its excellent working performance, ultra-high strength, toughness and durability, and good bonding and durability with concrete and steel interfaces.

[0003] In order to reduce the impact of repair and reinforcement construction on existing traffic, it is necessary to improve the early strength of UHPC, reduce the internal damage of UHPC materials caused by vehicle-bridge coupling vibration without interrupting traffic, balance the early strength and later performance, and reduce the cost of UHPC materials. Therefore, it is necessary to develop an ultra-early strength and anti-disturbance coarse aggregate UHPC and propose its preparation method. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, one aspect of the present invention aims to provide an ultra-early strength and disturbance-resistant coarse aggregate UHPC, wherein the raw materials of the coarse aggregate UHPC are 350 to 700 parts by weight of silicate cement, 120 to 240 parts by weight of sulphoaluminate cement, 30 to 100 parts by weight of silica fume, 30 to 70 parts by weight of mineral powder, 30 to 70 parts by weight of fly ash, 600 to 1000 parts by weight of fine aggregate, 600 to 1200 parts by weight of coarse aggregate, 2 to 7 parts by weight of regulating setting component, 2 to 7 parts by weight of high-efficiency water reducing agent and 40 to 120 parts by weight of steel fiber.

[0005] Preferably, the silicate cement model is 42.5 grade ordinary silicate cement or 52.5 grade ordinary silicate cement.

[0006] Preferably, the sulphoaluminate cement model is 42.5 grade low alkalinity sulphoaluminate cement.

[0007] The present invention adopts a composite system of ordinary Portland cement and sulphoaluminate cement. The ordinary Portland cement and the sulphoaluminate cement synergistically hydrate to promote the formation of ettringite, while accelerating the hydration reaction of calcium silicate in the ordinary Portland cement, thereby improving the early strength of UHPC; the ordinary Portland cement content is greater than the sulphoaluminate cement content, thereby ensuring the later strength and durability of the ultra-early strength anti-disturbance UHPC material.

[0008] Preferably, the fine aggregate is one or a combination of iron tailings sand and / or quartz sand, and has a particle size of 0.1 mm to 0.3 mm in continuous grading.

[0009] Preferably, the coarse aggregate is crushed stone with a particle size of 10 mm to 20 mm in continuous grading.

[0010] The present invention selects fine aggregate iron tailings sand or quartz sand and simultaneously mixes part of coarse aggregate to achieve the 3h compressive strength of the ultra-early strength anti-disturbance UHPC to be greater than or equal to 30MPa, which can greatly reduce the material cost.

[0011] Preferably, the setting regulating component includes a setting accelerator and a setting retarder in a ratio of 1-4:1-4; the setting accelerator is lithium carbonate or lithium sulfate, and the setting retarder is one or a combination of tartaric acid and / or sodium citrate.

[0012] The present invention adjusts the initial setting and final setting time of the ultra-early strength anti-disturbance coarse aggregate UHPC through the compounded setting adjustment component of the coagulant and the retarder, ensures sufficient construction time on site, and avoids the internal damage of the UHPC material caused by the vehicle-bridge coupling vibration under the condition of uninterrupted traffic. In the early stage of the mixing and pouring of the ultra-early strength anti-disturbance coarse aggregate UHPC, the retarder delays the hydration rate of the ordinary silicate cement and sulphoaluminate cement composite system by adsorbing on the surface of cement particles, forming sulphoaluminate and precipitate encapsulation; after a certain period of time, the effect of the retarder gradually weakens, the lithium salt in the coagulant reacts with the ions in the cement, promotes the bonding between cement particles, accelerates the formation of the hydration product calcium sulfonate, and the UHPC material quickly sets, reducing the influence of the vehicle-bridge coupling vibration on the coagulation and hardening of the UHPC material.

[0013] Preferably, the steel fiber is copper-plated steel fiber or milled steel fiber.

[0014] The present invention can select different types of steel fibers and fiber content according to the bending performance required by the design, and reasonably control the material cost while meeting the requirements of mechanical properties and durability.

[0015] Another object of the present invention is to provide a method for preparing ultra-early strength disturbance-resistant coarse aggregate UHPC, the specific steps of the preparation method are: S1. Stir the dry materials evenly to form a dry mix; S2. Add the wet material to water and stir thoroughly to form a wet mixture; S3. The dry mix and the wet mix are mixed to form a mixture; S4. After the mixture is uniform, coarse aggregate and steel fiber are slowly added until the coarse aggregate and steel fiber are fully wrapped by the slurry and evenly distributed to prepare the ultra-early strength and disturbance-resistant coarse aggregate UHPC.

[0016] Preferably, the dry materials in S1 are silicate cement, sulphoaluminate cement, silica fume, mineral powder, fly ash and fine aggregate.

[0017] Preferably, the wet materials in S2 are setting components and high-efficiency water reducing agent.

[0018] The beneficial effects of the present invention are as follows: The UHPC in the present invention adopts a composite system of ordinary Portland cement and sulphoaluminate cement, and the proportion of sulphoaluminate cement is lower than that of ordinary Portland cement. The sulphoaluminate cement and ordinary Portland cement are hydrated in a coordinated manner, giving full play to the characteristics of sulphoaluminate cement that are fast setting and hardening and excellent low-temperature performance, making up for the disadvantages of sulphoaluminate cement that is easy to carbonize and has a later strength reduction, thereby improving the early strength of UHPC.

[0019] Accelerators (lithium carbonate, lithium sulfate) and retarders (tartaric acid, sodium citrate) are used to adjust the initial and final setting time of the ultra-early strength anti-disturbance UHPC: the initial setting time is greater than 60 minutes and the final setting time is less than 90 minutes, which reduces the impact of changes in the construction environment temperature on the initial setting time of UHPC, ensures that there is enough construction time on site, and avoids stratification caused by mixing and pouring in batches. The difference between the initial and final setting time of the ultra-early strength anti-disturbance coarse aggregate UHPC is less than 30 minutes, which avoids internal damage to the UHPC material caused by the coupling vibration of the bridge under uninterrupted traffic conditions, affecting the final strength of the component. The use of coarse aggregate in the mix design can reduce the material cost of the ultra-early strength anti-disturbance coarse aggregate UHPC.

[0020] Additional aspects and advantages of the invention will become apparent from the following description, or may be learned by practice of the invention. DETAILED DESCRIPTION

[0021] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0022] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from the description. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0023] Embodiment 1 Material: P·O52.5 Portland cement 380kg / m 3 , 42.5 grade rapid hardening sulphoaluminate cement 130kg / m 3 , SF96 grade silica fume 50kg / m 3 , S95 grade mineral powder 40kg / m 3, Grade I fly ash 40kg / m 3 , 0.1-0.3mm continuous graded quartz sand 600kg / m 3 10-20mm continuous graded basalt crushed stone 1200kg / m 3 , Polycarboxylic acid high efficiency water reducing agent 3.1kg / m 3 , lithium carbonate (pure reagent) 1.5kg / m 3 , Tartaric acid (pure reagent) 1.4kg / m 3 , Copper-plated microfilament straight steel fiber (diameter 0.2mm, length 13mm) 60kg / m 3 and water 126kg / m 3 .

[0024] S1. P·O52.5 silicate cement 380kg / m 3 , 42.5 grade rapid hardening sulphoaluminate cement 130kg / m 3 , SF96 grade silica fume 50kg / m 3 , S95 grade mineral powder 40kg / m 3 , Grade I fly ash 40kg / m 3 and 0.1-0.3mm continuous graded quartz sand 600kg / m 3 Forced stirring to form a dry mix; S2. Add 3.1kg / m of polycarboxylic acid high efficiency water reducer 3 , lithium carbonate (pure reagent) 1.5kg / m 3 and tartaric acid (pure reagent) 1.4 kg / m 3 Add 126kg / m 3 Stir thoroughly in water to form a wet mix; S3. The dry mix and the wet mix are mixed to form a mixture; S4. After the mixture is uniform, slowly add 10-20mm continuous graded basalt crushed stone 1200kg / m 3 and copper-plated microfilament straight steel fiber (diameter 0.2mm, length 13mm) 60kg / m 3 , until the basalt crushed stone and copper-plated microfilament straight steel fibers are fully wrapped by the slurry and evenly distributed, the ultra-early strength and disturbance-resistant coarse aggregate UHPC is prepared.

[0025] Embodiment 2 Material: P·O52.5 Portland cement 460kg / m 3 , 42.5 grade rapid hardening sulphoaluminate cement 155kg / m 3 , SF96 grade silica fume 60kg / m 3 、S95 grade mineral powder 45kg / m 3 , Grade I fly ash 45kg / m 3, 0.1-0.3mm continuous graded quartz sand 720kg / m 3 , 10-20mm continuous graded basalt crushed stone 960kg / m 3 , Polycarboxylic acid high efficiency water reducing agent 4.1kg / m 3 , Industrial grade lithium sulfate 2.6kg / m 3 , Industrial grade tartaric acid 1.9kg / m 3 , Copper-plated microfilament straight steel fiber (diameter 0.2mm, length 13mm) 60kg / m 3 and water 144kg / m 3 .

[0026] S1. P·O52.5 silicate cement 460kg / m 3 , 42.5 grade rapid hardening sulphoaluminate cement 155kg / m 3 , SF96 grade silica fume 60kg / m 3 、S95 grade mineral powder 45kg / m 3 , Grade I fly ash 45kg / m 3 and 0.1-0.3mm continuous graded quartz sand 720kg / m 3 Forced stirring to form a dry mix; S2. Add 4.1kg / m of polycarboxylic acid high efficiency water reducer 3 , Industrial grade lithium sulfate 2.6kg / m 3 and industrial grade tartaric acid 1.9kg / m 3 Add 144kg / m 3 Stir thoroughly in water to form a wet mix; S3. The dry mix and the wet mix are mixed to form a mixture; S4. After the mixture is uniform, slowly add 10-20mm continuous graded basalt crushed stone 960kg / m 3 and copper-plated microfilament straight steel fiber (diameter 0.2mm, length 13mm) 60kg / m 3 , until the basalt crushed stone and copper-plated microfilament straight steel fibers are fully wrapped by the slurry and evenly distributed, the ultra-early strength and disturbance-resistant coarse aggregate UHPC is prepared.

[0027] Embodiment 3 Material: P·O52.5 silicate cement 536kg / m 3 , 42.5 grade rapid hardening sulphoaluminate cement 180kg / m 3 , SF96 grade silica fume 65kg / m 3 、S95 grade mineral powder 50kg / m 3 , Grade I fly ash 50kg / m 3 , 0.1-0.3mm continuous graded quartz sand 840kg / m 3, 10-20mm continuous graded basalt crushed stone 720kg / m 3 , Polycarboxylic acid high efficiency water reducing agent 5.2kg / m 3 , Industrial grade lithium sulfate 3.0kg / m 3 , Industrial grade citric acid 3.1kg / m 3 , Copper-plated microfilament straight steel fiber (diameter 0.2mm, length 13mm) 84kg / m 3 and water 170kg / m 3 .

[0028] S1. P·O52.5 silicate cement 536kg / m 3 , 42.5 grade rapid hardening sulphoaluminate cement 180kg / m 3 , SF96 grade silica fume 65kg / m 3 、S95 grade mineral powder 50kg / m 3 , Grade I fly ash 50kg / m 3 and 0.1-0.3mm continuous graded quartz sand 720kg / m 3 Forced stirring to form a dry mix; S2. Add 5.2kg / m of polycarboxylic acid high efficiency water reducer 3 , Industrial grade lithium sulfate 3.0kg / m 3 and industrial grade citric acid 3.1kg / m 3 Add 170kg / m 3 Stir thoroughly in water to form a wet mix; S3. The dry mix and the wet mix are mixed to form a mixture; S4. After the mixture is uniform, slowly add 10-20mm continuous graded basalt crushed stone 720kg / m 3 and copper-plated microfilament straight steel fiber (diameter 0.2mm, length 13mm) 84kg / m 3 , until the basalt crushed stone and copper-plated microfilament straight steel fibers are fully wrapped by the slurry and evenly distributed, the ultra-early strength and disturbance-resistant coarse aggregate UHPC is prepared.

[0029] Embodiment 4 Material: P·O52.5 Portland cement 380kg / m 3 , 42.5 grade rapid hardening sulphoaluminate cement 130kg / m 3 , SF96 grade silica fume 50kg / m 3 , S95 grade mineral powder 40kg / m 3 , Grade I fly ash 40kg / m 3 , 0.1-0.3mm continuous graded quartz sand 420kg / m 3 , 0.1-0.3mm continuous graded iron tailings sand 180kg / m 310-20mm continuous graded basalt crushed stone 1100kg / m 3 , Polycarboxylic acid high efficiency water reducing agent 3.1kg / m 3 , Industrial grade lithium sulfate 2.6kg / m 3 , Industrial grade tartaric acid 1.9kg / m 3 , Copper-plated milling steel fiber (length 30mm) 60kg / m 3 and water 144kg / m 3 .

[0030] S1. P·O52.5 silicate cement 380kg / m 3 , 42.5 grade rapid hardening sulphoaluminate cement 130kg / m 3 , SF96 grade silica fume 50kg / m 3 , S95 grade mineral powder 40kg / m 3 , Grade I fly ash 40kg / m 3 , 0.1-0.3mm continuous graded quartz sand 420kg / m 3 and 0.1-0.3mm continuous graded iron tailings sand 180kg / m 3 Forced stirring to form a dry mix; S2. Add 3.1kg / m of polycarboxylic acid high efficiency water reducer 3 , Industrial grade lithium sulfate 2.6kg / m 3 and industrial grade tartaric acid 1.9kg / m 3 Add 144kg / m 3 Stir thoroughly in water to form a wet mix; S3. The dry mix and the wet mix are mixed to form a mixture; S4. After the mixture is uniform, slowly add 10-20mm continuous graded basalt crushed stone 1100kg / m 3 and copper-plated milled steel fiber (length 30mm) 60kg / m 3 , until the basalt crushed stone and copper-plated milled steel fibers are fully wrapped by the slurry and evenly distributed, the ultra-early strength and disturbance-resistant coarse aggregate UHPC is prepared.

[0031] Performance Test: The ultra-early strength disturbance-resistant coarse aggregate UHPC prepared in the embodiment was tested for setting time and compressive strength at different ages. The setting time test method adopted the "Standard for Test Methods for Performance of Ordinary Concrete Mixtures" (GB / T50080-2016), and the compressive strength test method adopted the "Test Methods for Mechanical Properties of Ordinary Concrete" (GB / T 50081-2002). The specific performance test results are shown in Table 1.

[0032] Table 1. Properties of ultra-early strength anti-disturbance coarse aggregate UHPC prepared in various embodiments As can be seen from Table 1, the ultra-early strength anti-disturbance coarse aggregate UHPC prepared by the present invention has short initial setting and final setting times, and has sufficient initial setting time to avoid the influence of various factors on the construction site, and the difference between the initial setting and final setting time is short, which avoids the internal damage of the UHPC material caused by bridge coupling vibration. It not only has high early strength, but also has excellent late strength, and has a very good repair effect on components such as expansion joints, wet joints and bridge deck pavement in bridge engineering. Compared with Example 1, Example 2 and Example 3 use industrial-grade accelerators and retarders to replace analytical pure reagents, which have little effect on the setting time and compressive strength of UHPC and have good economic benefits; Example 4 uses milling steel fibers. For components such as expansion joints that have low requirements for concrete bending performance, a small amount of milling steel fibers can be added to control the initiation and expansion of concrete cracks.

[0033] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may also have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An ultra-early strength disturbance-resistant coarse aggregate UHPC, characterized by: The coarse aggregate UHPC raw materials include 350 to 700 parts by weight of silicate cement, 120 to 240 parts by weight of sulphoaluminate cement, 30 to 100 parts by weight of silica fume, 30 to 70 parts by weight of mineral powder, 30 to 70 parts by weight of fly ash, 600 to 1000 parts by weight of fine aggregate, 600 to 1200 parts by weight of coarse aggregate, 2 to 7 parts by weight of regulating setting component, 2 to 7 parts by weight of high-efficiency water reducing agent and 40 to 120 parts by weight of steel fiber.

2. The ultra-early strength anti-disturbance coarse aggregate UHPC according to claim 1, characterized in that: The silicate cement model is 42.5 grade ordinary silicate cement or 52.5 grade ordinary silicate cement.

3. The ultra-early strength anti-disturbance coarse aggregate UHPC according to claim 1, characterized in that: The sulphoaluminate cement model is 42.5 grade low alkalinity sulphoaluminate cement.

4. The ultra-early strength anti-disturbance coarse aggregate UHPC according to claim 1, characterized in that: The fine aggregate is one or a combination of iron tailings sand and / or quartz sand, and has a particle size of 0.1 mm to 0.3 mm in continuous grading.

5. The ultra-early strength anti-disturbance coarse aggregate UHPC according to claim 1, characterized in that: The coarse aggregate is crushed stone with a particle size of 10mm~20mm in continuous grading.

6. The ultra-early strength anti-disturbance coarse aggregate UHPC according to claim 1, characterized in that: The setting regulating component comprises a setting accelerator and a setting retarder in a ratio of 1-4:1-4; the setting accelerator is lithium carbonate or lithium sulfate, and the setting retarder is one or a combination of tartaric acid and / or sodium citrate.

7. The ultra-early strength anti-disturbance coarse aggregate UHPC according to claim 1, characterized in that: The steel fiber is copper-plated steel fiber or milled steel fiber.

8. The method for preparing ultra-early strength disturbance-resistant coarse aggregate UHPC according to claim 1, characterized in that: The specific steps of the preparation method are: S1. Stir the dry materials uniformly to form a dry mix; S2. Add the wet material to water and stir thoroughly to form a wet mixture; S3. The dry mix and the wet mix are mixed to form a mixture; S4. After the mixture is uniform, coarse aggregate and steel fiber are slowly added until the coarse aggregate and steel fiber are fully wrapped by the slurry and evenly distributed to prepare the ultra-early strength and disturbance-resistant coarse aggregate UHPC.

9. The method for preparing ultra-early strength disturbance-resistant coarse aggregate UHPC according to claim 8, characterized in that: The dry materials in S1 are silicate cement, sulphoaluminate cement, silica fume, mineral powder, fly ash and fine aggregate.

10. The method for preparing ultra-early strength disturbance-resistant coarse aggregate UHPC according to claim 8, characterized in that: The wet materials in S2 are setting components and high-efficiency water reducing agent.

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