Engineering gelling composite material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of building materials, and particularly relates to an engineering gelling composite material and a preparation method and application thereof. The machine-made sand is used as the core aggregate, and the compactness of the engineering gel composite material is improved due to the good grading controllability and micro powder filling effect of the machine-made sand. Through the synergistic effect of the machine-made sand and the mixed fibers, the cost of the engineering gelling composite material is reduced, meanwhile, the excellent mechanical property and durability of the engineering gelling composite material are kept, the balance of the mechanical property and the durability is achieved, and the sustainability is high. Specifically, by controlling the mixing ratio of the raw materials, the engineering gelling composite material is excellent in mechanical property, and has excellent fluidity, high ductility, bending toughness, breaking strength and compressive strength; the mixed fibers form a multi-stage crack resistance mechanism, and the crack resistance of the engineering gelling composite material is enhanced by combining the grain composition advantage of the machine-made sand.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials, and in particular relates to an engineering gelling composite material and a preparation method and application thereof. Background Art

[0002] Engineered cementitious composites (ECCs) hold great potential in applications such as structural repair due to their excellent strain hardening properties, multi-crack behavior, and durability. Traditional ECCs achieve this excellent performance by utilizing high-quality quartz sand with a particle size less than 150 μm and polyvinyl alcohol (PVA) fibers treated with an oil. However, the high cost of these raw materials severely restricts their large-scale application in infrastructure construction.

[0003] Researchers have attempted to reduce the cost of engineered cementitious composites by replacing raw materials, such as using industrial byproducts (fly ash, slag) to replace part of the cement, or using recycled aggregate to replace natural sand. In terms of aggregate substitution, studies have used recycled fine aggregate to prepare engineered cementitious composites with compressive strengths exceeding 120 MPa. The resulting recycled fine aggregate-based engineered cementitious composites have superior tensile strain capacity, multi-crack cracking, and crack width control capabilities. However, the interface transition zone (ITZ) of recycled aggregates is weak due to the mortar attached to the surface, resulting in poor performance stability and a tendency to reduce strength and durability. Summary of the Invention

[0004] The purpose of the present invention is to provide an engineering gelled composite material and a preparation method and application thereof. The engineering gelled composite material provided by the present invention has both economic efficiency and performance stability.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides an engineering cementitious composite material, comprising the following raw materials: mixed fibers, machine-made sand, fly ash, an admixture, cement and water; the mixed fibers comprise polypropylene fibers and basalt fibers; the volume ratio of the polypropylene fibers to the basalt fibers is 0.5-1.5:0.5-1.5; the sand-to-binder ratio of the engineering cementitious composite material is 0.40-0.70, and the water-to-binder ratio is 0.20-0.40; the fineness modulus of the machine-made sand is 0.9-2.3.

[0007] Preferably, the volume content of the mixed fiber in the engineered gelled composite material is 1.95-2.05%.

[0008] Preferably, the polypropylene fiber has a length of 6 to 18 mm, a diameter of 20 to 50 μm, and a density of 0.90 to 0.91 g / cm3 The basalt fiber has a length of 6 to 18 mm, a diameter of 13 to 17 μm, and a density of 2.6 to 2.8 g / cm 3 .

[0009] Preferably, the stone powder content of the machine-made sand is ≤10%.

[0010] Preferably, the mass ratio of fly ash to cement is 10 to 50:70.

[0011] Preferably, the admixture includes a water reducing agent.

[0012] The present invention provides a method for preparing the engineering gelled composite material described in the above scheme, comprising the following steps:

[0013] The mixed fiber, machine-made sand, fly ash, admixture, cement and water are mixed, poured and cured in sequence to obtain the engineering cementitious composite material.

[0014] Preferably, the mixed fiber, machine-made sand, fly ash, admixture, cement and water are mixed as follows: cement, fly ash and a first portion of water are mixed to obtain a premixed slurry; the premixed slurry is mixed with polypropylene fiber, basalt fiber and a water reducer to obtain a fiber composite slurry; and the fiber composite slurry is mixed with machine-made sand and the remaining portion of water.

[0015] Preferably, after pouring, the mold is demoulded after standing still; the standing time is 20 to 28 hours.

[0016] The present invention also provides applications of the engineering gelled composite material described in the above solution or the engineering gelled composite material obtained by the preparation method described in the above solution in the field of construction or engineering.

[0017] The present invention provides an engineering cementitious composite material. The present invention uses machine-made sand as the core aggregate. Its good gradation controllability and micropowder filling effect improve the density of the engineering cementitious composite material and can reduce porosity by 15%. Through the synergistic effect of machine-made sand and blended fibers (polypropylene fiber (PPF) and basalt fiber (BF)), the present invention reduces the cost of the engineering cementitious composite material by 20%, while maintaining its excellent mechanical properties and good durability, achieving a balance between mechanical properties and durability and strong sustainability. Specifically:

[0018] (1) Significantly improved economic efficiency: Compared with basalt sand and sea sand, the present invention uses machine-made sand as fine aggregate, which has a wide source, controllable particle shape, and low cost; compared with single fiber, the mixture of polypropylene fiber and basalt fiber can significantly reduce the fiber cost.

[0019] (2) Optimization of mechanical properties: The present invention controls the raw material mix ratio (the amount of manufactured sand and fineness modulus, water-binder ratio, sand-binder ratio and fiber mixing ratio) to make the engineering cementitious composite material have excellent mechanical properties, excellent fluidity, flexural strength and compressive strength, as well as good ductility and bending toughness, meeting most engineering performance requirements; the mixed fiber forms a multi-level crack resistance mechanism, combined with the particle grading advantage of manufactured sand, further inhibits crack expansion, and can enhance the crack resistance of the engineering cementitious composite material.

[0020] (3) Improved durability: The angular morphology and surface roughness of machine-made sand enhance its mechanical engagement with the cement paste, contributing to improved durability of engineered cementitious composites. The stability of machine-made sand and the weather resistance of the mixed fibers further mitigate the material’s durability flaws.

[0021] The present invention also provides a method for preparing the engineered gelled composite material described in the above scheme. The preparation method provided by the present invention has simple steps, reduces costs, and avoids the use of recycled micropowder or complex additives. The performance of the engineered gelled composite material is more controllable, achieving a balance between environmental protection and performance.

[0022] The present invention also provides applications of the engineering cementitious composite material described in the above-mentioned solution, or the engineering cementitious composite material obtained by the preparation method described in the above-mentioned solution, in the construction or engineering fields. The engineering cementitious composite material provided by the present invention is suitable for use in the construction or engineering fields and has applicability in multiple scenarios. It is particularly suitable for bridge and tunnel repair, building seismic reinforcement, and highly corrosive environments such as marine engineering, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 A test chart of the fluidity of the mixed material of the engineering gelled composite material provided by the present invention;

[0025] Figure 2 This is a test chart of the flexural strength of the engineering cementitious composite material provided by the present invention;

[0026] Figure 3 This is a test chart of the compressive strength of the engineering cementitious composite material provided by the present invention. DETAILED DESCRIPTION

[0027] The present invention provides an engineering cementitious composite material, comprising the following raw materials: mixed fibers, machine-made sand, fly ash, an admixture, cement and water; the mixed fibers comprise polypropylene fibers and basalt fibers; the volume ratio of the polypropylene fibers to the basalt fibers is 0.5-1.5:0.5-1.5; the sand-to-binder ratio of the engineering cementitious composite material is 0.40-0.70, and the water-to-binder ratio is 0.20-0.40; the fineness modulus of the machine-made sand is 0.9-2.3.

[0028] The raw materials of the engineered gelled composite material provided by the present invention include mixed fibers; the volume content of the mixed fibers in the engineered gelled composite material can be 1.95-2.05%, specifically 1.95%, 1.97%, 2%, 2.03% or 2.05%.

[0029] In the present invention, the length of the polypropylene fiber can be 6 to 18 mm, specifically 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, 16 mm or 18 mm, the diameter can be 20 to 50 μm, specifically 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or 50 μm, and the density can be 0.90 to 0.91 g / cm 3 , specifically 0.905 g / cm 3 .

[0030] In the present invention, the tensile strength of the polypropylene fiber can be ≥350 MPa, specifically 390 MPa or 469 MPa, the elastic modulus can be ≥3.5 GPa, specifically 3.7 GPa or 4.3 GPa, and the ultimate elongation can be 20-30%, specifically 24% or 28.4%.

[0031] In the present invention, the length of the basalt fiber can be 6 to 18 mm, specifically 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, 16 mm or 18 mm, the diameter can be 13 to 17 μm, specifically 13 μm, 14 μm, 15 μm, 16 μm or 17 μm, and the density can be 2.6 to 2.8 g / cm 3 , specifically 2.7 g / cm 3 .

[0032] In the present invention, the tensile strength of the basalt fiber can be ≥1250MPa, specifically 1350MPa or 1550MPa, the elastic modulus can be ≥30GPa, specifically 32GPa or 35.8GPa, and the ultimate elongation can be 2-5%, specifically 3%, 3.6% or 4%.

[0033] In the present invention, the volume ratio of the polypropylene fiber to the basalt fiber is 0.5-1.5:0.5-1.5, specifically 0.5:0.7, 0.5:1.0, 0.5:1.2, 0.5:1.5, 0.8:0.5, 0.8:0.7, 0.8:1.0, 0.8:1.2, 0.8:1.5, 1:0.5, 1:0.7, 1:1, 1:1.2, 1:1.5, 1.3:0.5, 1.3:0.7, 1.3:1.0, 1.3:1.2, 1.3:1.5, 1.5:0.5, 1.5:0.7, 1.5:1.0 or 1.5:1.2, preferably 1:1. Polypropylene fiber has good flexibility and can effectively bridge microcracks and delay the destruction process; the high elastic modulus of basalt fiber can effectively share the load and improve the overall bearing capacity of the material; utilizing the flexibility of polypropylene fiber and the high elastic modulus of basalt fiber, the synergistic effect of the two can significantly improve the toughness and bearing capacity of engineering cementitious composites.

[0034] The raw materials of the engineering cementitious composite material provided by the present invention include machine-made sand; the machine-made sand can be local machine-made sand, specifically the machine-made sand from Changsha in the embodiment.

[0035] In the present invention, the fineness modulus of the manufactured sand can be between 0.9 and 2.3, specifically 0.9, 1.2, 1.5, 1.8, 2.1, or 2.3, with a preferred value of 1.4. The stone powder content of the manufactured sand can be ≤10%, specifically 10%, 8%, 5%, 3%, or 1%. The angular morphology and surface roughness of the manufactured sand enhance its mechanical engagement with the cement paste, while the stone powder fills the intergranular spaces and improves the material's density. Specifically, manufactured sand with a fineness modulus of 1.4, as a fine aggregate, can balance gradation, reduce the proportion of large pores, and significantly improve the material's density.

[0036] In a specific embodiment of the present invention, the machine-made sand may include one or more of fine machine-made sand, medium machine-made sand and coarse machine-made sand; the fineness modulus of the fine machine-made sand may be 0.9, and the maximum particle size may be 0.3 mm; the fineness modulus of the medium machine-made sand may be 1.4, and the maximum particle size may be 0.6 mm; the fineness modulus of the coarse machine-made sand may be 2.3, and the maximum particle size may be 1.18 mm.

[0037] In the present invention, the sand-to-binder ratio (S / B, which refers to the ratio of the mass of manufactured or natural sand to the total mass of cement and fly ash) of the engineered cementitious composite material is 0.40 to 0.70, specifically 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, or 0.70, and is preferably 0.50. This sand-to-binder ratio helps form a uniform and dense pore structure, improving the mechanical properties and durability of the material.

[0038] The raw materials of the engineering cementitious composite material provided by the present invention include fly ash; the mass ratio of the fly ash to cement can be 10 to 50:70, specifically 10:70, 15:70, 20:70, 25:70, 30:70, 35:70, 40:70, 45:70 or 50:70.

[0039] In the present invention, the fly ash can be Class I fly ash; the fineness of the fly ash can be 45 μm square hole sieve residue ≤12%, specifically 6.5% or 9.5%, the loss on ignition can be ≤5.0%, specifically 2.06% or 4%, the water requirement ratio can be ≤100%, specifically 93% or 95%, and the 28-day activity index can be ≥70%, specifically 72% or 79%.

[0040] The raw materials of the engineering cementitious composite material provided by the present invention include an admixture; the mass ratio of the admixture to water can be 1:8-40, specifically 1:8, 1:12, 1:16, 1:20, 1:24, 1:28, 1:31.25, 1:36 or 1:40.

[0041] In the present invention, the admixture may be a water reducer; the water reducer may be a polycarboxylate water reducer; the polycarboxylate water reducer may be a polycarboxylate ether water reducer; the water reduction rate of the water reducer may be ≥25%, specifically 25%.

[0042] The raw materials of the engineering cementitious composite material provided by the present invention include cement; the cement may be Portland cement; the Portland cement may include one or more of P.II 42.5 grade Portland cement and PO 42.5 grade Portland cement.

[0043] In the present invention, the specific surface area of ​​the cement can be 300 to 350 m 2 / kg, specifically 325m 2 / kg, the initial setting time can be ≥45min, specifically 60min, 100min or 146min, the final setting time can be ≤390min, specifically 208min, 258min, 300min or 350min, the 28-day flexural strength can be ≥6.5MPa, specifically 7.5MPa or 8.5MPa, and the 28-day compressive strength can be ≥42.5MPa, specifically 50MPa or 61.6MPa.

[0044] The raw materials of the engineered cementitious composite material provided by the present invention include water; the water-to-binder ratio (W / B, which refers to the ratio of the mass of water to the total mass of cement and fly ash) of the engineered cementitious composite material can be 0.20 to 0.40, specifically 0.20, 0.23, 0.26, 0.28, 0.30, 0.33, 0.35, 0.38, or 0.40, preferably 0.30. The use of this water-to-binder ratio in the present invention helps to form a uniform and dense pore structure, improving the mechanical properties and durability of the material.

[0045] The present invention provides a method for preparing the engineering gelled composite material described in the above scheme, comprising the following steps:

[0046] The mixed fiber, machine-made sand, fly ash, admixture, cement and water are mixed, poured and cured in sequence to obtain the engineering cementitious composite material.

[0047] The present invention mixes blended fiber, manufactured sand, fly ash, admixture, cement, and water (referred to as a first mixing process) to obtain a mixed material. In the present invention, the first mixing process may include: mixing cement, fly ash, and a first portion of water (referred to as mixing A) to obtain a premixed slurry; mixing the premixed slurry with polypropylene fiber, basalt fiber, and a water reducer (referred to as mixing B) to obtain a fiber composite slurry; and mixing the fiber composite slurry with manufactured sand and the remaining portion of water (referred to as mixing C).

[0048] In the present invention, the mass ratio of the first part of water to the remaining part of water can be 50-80:20-50, specifically 50:50, 55:45, 60:40, 65:35, 70:30, 75:25 or 80:20.

[0049] In the present invention, the mixing A can be stirring mixing; the rotation speed of the stirring mixing can be planetary stirring mixing; the revolution speed of the planetary stirring mixing can be 135-145rpm, specifically 140rpm, the rotation speed can be 275-295rpm, specifically 285rpm, and the mixing time can be 1-2min, specifically 1.5min.

[0050] In the present invention, the mixing B may include slow stirring and fast stirring in sequence; the slow stirring may be slow planetary stirring mixing; the revolution speed of the slow planetary stirring mixing may be 135 to 145 rpm, specifically 140 rpm, the rotation speed may be 275 to 295 rpm, specifically 285 rpm, and the mixing time may be 1 to 2 min, specifically 1.5 min.

[0051] In the present invention, the rapid stirring can be rapid planetary stirring and mixing; the revolution speed of the rapid planetary stirring and mixing can be 275-295rpm, specifically 285rpm, the rotation speed can be 550-590rpm, specifically 560rpm, 5 / 70rpm or 580rpm, and the mixing time can be 2-5min, specifically 3min or 4min.

[0052] In the present invention, the mixing C may include slow stirring mixing and fast stirring mixing in sequence; the slow stirring mixing may be slow planetary stirring mixing; the revolution speed of the slow planetary stirring mixing may be 135 to 145 rpm, specifically 140 rpm, the rotation speed may be 275 to 295 rpm, specifically 285 rpm, and the mixing time may be 1 to 2 min, specifically 1.5 min.

[0053] In the present invention, the rapid stirring and mixing can be rapid planetary stirring and mixing; the revolution speed of the rapid planetary stirring and mixing can be 275-295rpm, specifically 285rpm, the rotation speed can be 550-590rpm, specifically 560rpm, 5 / 70rpm or 580rpm, and the mixing time can be 3-5min, specifically 4min.

[0054] After the mixture is obtained by mixing, the present invention sequentially casts and cures the mixture to obtain the engineering gelled composite material. In the present invention, the casting mold size can be 40 mm×40 mm×160 mm.

[0055] In the present invention, the pouring may further include standing still and then demoulding; the standing still time may be 20 to 28 hours, specifically 22 hours, 24 hours or 26 hours.

[0056] In the present invention, the curing may be standard curing; the conditions for the standard curing may be: temperature of 20°C ± 2°C, humidity ≥ 95%, and duration of 28 to 30 days; the curing may be performed in a curing room. The present invention facilitates further stabilization and improvement of material properties through standard curing.

[0057] The present invention also provides applications of the engineering gelled composite material described in the above solution or the engineering gelled composite material obtained by the preparation method described in the above solution in the field of construction or engineering.

[0058] The engineering cementitious composite material provided by the present invention is suitable for use in the construction field or engineering field, has applicability in multiple scenarios, and is particularly suitable for the field of bridge and tunnel repair, the field of building seismic reinforcement, or high-corrosion environments such as marine engineering, and has broad application prospects.

[0059] In order to further illustrate the present invention, the scheme of the present invention is described in detail below with reference to the accompanying drawings and embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0060] Example 1

[0061] (1) Raw materials and mix ratio

[0062] Cementitious material: P.II 42.5 grade ordinary Portland cement, with a specific surface area of ​​325m 2 / kg, the initial setting time is 146min, the final setting time is 208min, its 28-day flexural strength is 8.5MPa, and the 28-day compressive strength is 61.6MPa; Grade I fly ash, fineness is 45μm, 45μm square hole sieve residue is 6.5%, loss on ignition is 2.06%, water requirement ratio is 93%, and 28-day activity index is 79%.

[0063] Fine aggregate: local machine-made sand (denoted as MS), with a fineness modulus of 2.3 and a corresponding maximum particle size of 1.18 mm.

[0064] Blended fiber: Polypropylene fiber, length 12 mm, diameter 32.7 μm, density 0.91 g / cm 3 , tensile strength is 469MPa, elastic modulus is 4.3GPa, ultimate elongation is 28.4%; basalt fiber, length is 12mm, diameter is 17μm, density is 2.62g / cm 3 , tensile strength is 1550MPa, elastic modulus is 35.8GPa, and ultimate elongation is 3.6%.

[0065] Admixture: high-efficiency water reducer, Jiangsu Chaoli Building Materials Technology Co., Ltd. CPA-R slow-setting polycarboxylic acid high-performance water reducer, with a water reduction rate of 25%.

[0066] Mixing ratio: 0.7 parts by mass of cement, 0.3 parts by mass of fly ash, 0.3 parts by mass of water (water-binder ratio of 0.3), 0.5 parts by mass of sand (sand-binder ratio of 0.5), 1.0% by volume of polypropylene fiber, and 1.0% by volume of basalt fiber. The raw material cost is significantly lower than that of traditional engineering cementitious composite materials.

[0067] (2) Preparation of engineering cementitious composite material specimens

[0068] Mixing: Using a planetary cement mortar mixer, first add cement, fly ash and part of the water (60% of the total water), stir and mix slowly (orbital speed of 140±5rpm; rotation speed of 285±10rpm) for 1 minute; then add polypropylene fiber, basalt fiber and water reducer, stir slowly (orbital speed of 140±5rpm; rotation speed of 285±10rpm) for 1 minute, and then stir quickly for 2 minutes; then add machine-made sand and the remaining water, stir slowly (orbital speed of 140±5rpm; rotation speed of 285±10rpm) for 1 minute, and then stir quickly (orbital speed of 285±10rpm; rotation speed of 570±20rpm) for 3 minutes until uniform, to obtain a mixed material.

[0069] Casting: Cast the mixture into a specimen mold of 40 mm × 40 mm × 160 mm.

[0070] Curing: demould after 24 hours, transfer the specimen to a curing room and cure for 28 days under standard curing conditions (relative humidity greater than 95%, temperature 20℃±2℃).

[0071] Example 2

[0072] The preparation method of this embodiment is the same as that of Example 1, except that the specification of the machine-made sand is adjusted to a fineness modulus of 1.4, corresponding to a maximum particle size of 0.6 mm.

[0073] Example 3

[0074] The preparation method of this embodiment is the same as that of Example 1, except that the specification of the machine-made sand is adjusted to a fineness modulus of 0.9, corresponding to a maximum particle size of 0.3 mm.

[0075] Example 4

[0076] The preparation method of this embodiment is the same as that of Example 1, except that the water-to-binder ratio is 0.2.

[0077] Example 5

[0078] The preparation method of this embodiment is the same as that of Example 1, except that the water-to-binder ratio is 0.4.

[0079] Example 6

[0080] The preparation method of this embodiment is the same as that of Example 1, except that the sand-to-adhesive ratio is 0.4.

[0081] Example 7

[0082] The preparation method of this embodiment is the same as that of Example 1, except that the sand-to-adhesive ratio is 0.6.

[0083] Example 8

[0084] The preparation method of this embodiment is the same as that of Example 1, except that the sand-to-adhesive ratio is 0.7.

[0085] Example 9

[0086] The preparation method of this embodiment is the same as that of Example 1, except that the volume ratio of polypropylene fiber to basalt fiber is 1.5:0.5.

[0087] Example 10

[0088] The preparation method of this embodiment is the same as that of Example 1, except that the volume ratio of polypropylene fiber to basalt fiber is 0.5:1.5.

[0089] Comparative Example 1

[0090] The preparation method of this comparative example is the same as that of Example 1, except that the machine-made sand is replaced by natural sand (denoted as NS), the fineness modulus of the natural sand is 1.4, and the corresponding maximum particle size is 0.6 mm.

[0091] Comparative Example 2

[0092] The preparation method of this comparative example is the same as that of Example 1, except that the volume ratio of polypropylene fiber to basalt fiber is 2:0.

[0093] Test Example 1

[0094] The fluidity test of the mixtures prepared in Examples 1 to 10 and Comparative Examples 1 to 2 was carried out, and a table jump test was carried out according to GB / T 2419-2005 Determination of fluidity of cement mortar. The results are as follows: Figure 1 shown.

[0095] according to Figure 1 It can be seen that by comparing the fluidity of the mixture of engineering cementitious composite materials with different types of fine aggregates, it can be seen that the fluidity of the mixture prepared by using machine-made sand is significantly higher than that of natural sand with the same fineness modulus; as the fineness modulus of machine-made sand decreases, the fluidity of the mixture increases slightly, but the overall difference is not large; as the water-binder ratio increases, the fluidity of the mixture gradually increases, and when the water-binder ratio increases from 0.2 to 0.3, the fluidity of the mixture increases from 163.3mm to 194.8mm, and the fluidity of the mixture is more significantly improved; the fluidity of the mixture is highest when the sand-binder ratio is 0.4, and then as the sand-binder ratio increases, the fluidity of the mixture gradually decreases, but the overall change range is relatively small; as the proportion of polypropylene fiber decreases and the proportion of basalt fiber increases, the fluidity of the mixture gradually decreases. In summary, the present invention uses machine-made sand to prepare engineering cementitious composite materials with excellent fluidity.

[0096] Test Example 2

[0097] The flexural strength of the engineering cementitious composite material specimens prepared in Examples 1 to 10 and Comparative Examples 1 to 2 was tested using a three-point bending loading method. The specimen size was 40 mm × 40 mm × 160 mm, the loading rate was 50 ± 2 N / s, and the test time points were 3 days, 7 days, and 28 days. The results are as follows: Figure 2 shown.

[0098] according to Figure 2 It can be seen that when the fineness modulus of manufactured sand is 1.4, the corresponding flexural strength at different ages is slightly higher than that at other fineness moduli, but this difference is not significant. The flexural strength of the engineered cementitious composite specimens prepared using manufactured sand at different ages is significantly higher than that of natural sand. The lower the water-binder ratio, the higher the flexural strength of the engineered cementitious composite at different ages. Excessively high or low sand-binder ratios affect the particle size distribution and structure within the material, thereby affecting the flexural strength of the engineered cementitious composite. As the proportion of basalt fiber increases, the flexural strength of the engineered cementitious composite at each age also shows a gradual increasing trend. Overall, the manufactured sand engineered cementitious composite prepared using the embodiments of the present invention has excellent flexural strength.

[0099] Test Example 3

[0100] On the half prisms retained after the flexural test, compressive strength tests were conducted on the engineering cementitious composite material specimens prepared in Examples 1 to 10 and Comparative Examples 1 to 2. The loading rate was 2.4±0.2 kN / s, and the test time points were 3 days, 7 days, and 28 days. The results are as follows: Figure 3 shown.

[0101] according to Figure 3 It can be seen that as the fineness modulus of manufactured sand decreases, the compressive strength of the engineered cementitious composite material increases slightly at each age, but the increase is not significant. The compressive strength of the engineered cementitious composite material specimens prepared using manufactured sand is significantly higher than that of natural sand at different ages. At the 28-day age, the compressive strength of the engineered cementitious composite material with a water-binder ratio of 0.2 is 86.2 MPa, which is much higher than the 59.58 MPa with a water-binder ratio of 0.4. When the sand-binder ratio is 0.6, the compressive strength of the engineered cementitious composite material specimens at 3 and 7 days is relatively high. When the sand-binder ratio is 0.7, the compressive strength of the engineered cementitious composite material specimens at 28 days is relatively high, but the overall difference is small. With the increase of the basalt fiber ratio, the compressive strength of the engineered cementitious composite material at each age also shows a gradual increasing trend. When the mixed fiber ratio changes from 1.5% and 0.5% to 1% and 1%, its compressive strength increases significantly. In summary, the engineered sand engineered cementitious composite material prepared by the embodiment of the present invention has excellent compressive strength.

[0102] It can be seen from the above examples that the engineering cementitious composite material provided by the present invention has excellent mechanical properties, excellent fluidity, flexural strength and compressive strength, low cost, simple and efficient preparation steps.

[0103] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. An engineering gelled composite material, characterized in that: The raw materials include: mixed fiber, machine-made sand, fly ash, admixtures, cement and water; The mixed fibers include polypropylene fibers and basalt fibers; The volume ratio of the polypropylene fiber to the basalt fiber is 0.5-1.5:0.5-1.5; The engineering cementitious composite material has a sand-binder ratio of 0.40 to 0.70 and a water-binder ratio of 0.20 to 0.40; The fineness modulus of the machine-made sand is 0.9 to 2.

3.

2. The engineering gelled composite material according to claim 1, characterized in that: The volume content of the mixed fiber in the engineering gelled composite material is 1.95-2.05%.

3. The engineering gelled composite material according to claim 1 or 2, characterized in that: The polypropylene fiber has a length of 6 to 18 mm, a diameter of 20 to 50 μm, and a density of 0.90 to 0.91 g / cm 3 ; The basalt fiber has a length of 6 to 18 mm, a diameter of 13 to 17 μm, and a density of 2.6 to 2.8 g / cm 3 .

4. The engineering gelled composite material according to claim 1, characterized in that: The stone powder content of the machine-made sand is ≤10%.

5. The engineering gelled composite material according to claim 1 or 4, characterized in that: The mass ratio of the fly ash to cement is 10 to 50:

70.

6. The engineering gelled composite material according to claim 1, characterized in that: The admixture includes a water reducing agent.

7. The method for preparing the engineering gelled composite material according to any one of claims 1 to 5, characterized in that: The following steps are involved: The mixed fiber, machine-made sand, fly ash, admixture, cement and water are mixed, poured and cured in sequence to obtain the engineering cementitious composite material.

8. The preparation method according to claim 7, characterized in that The mixed fiber, machine-made sand, fly ash, admixture, cement and water are mixed as follows: mixing cement, fly ash and the first portion of water to obtain a premixed slurry; Mixing the premixed slurry with polypropylene fiber, basalt fiber and a water reducer to obtain a fiber composite slurry; The fiber composite slurry is mixed with machine-made sand and the remaining portion of water.

9. The preparation method according to claim 7 or 8, characterized in that After the pouring, the mold is demoulded after standing still; The standing time is 20 to 28 hours.

10. Use of the engineering cementitious composite material according to any one of claims 1 to 6 or the engineering cementitious composite material obtained by the preparation method according to any one of claims 7 to 9 in the field of construction or engineering.

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