Lightweight aggregate, method for its production and use thereof

Abstract

The application provides a light aggregate and a preparation method and application thereof, relates to the technical field of aggregates, and the light aggregate comprises steel slag, waste ceramic and active admixture. The application converts the steel slag and the waste ceramic into the light aggregate, and combines the light aggregate with phosphate cement, thereby providing an MPC-UHPC material with high strength, durability and lightness, the material has excellent corrosion resistance, lightness and high early strength, and has significant advantages in environmental protection and economic benefits.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aggregate, in particular to a light aggregate and a preparation method and application thereof. BACKGROUND

[0002] Traditional ultra-high performance concrete (UHPC) mostly uses high-density and high-strength aggregate, which has excellent mechanical properties, but its density is high, the construction weight is large, and it causes additional burden to the engineering structure. At the same time, a large amount of construction and industrial solid waste (such as steel slag and waste ceramic) is not effectively utilized, resulting in resource waste and environmental pollution. The existing technology still lacks a MPC-UHPC material that can combine the characteristics of lightness, environmental protection and high strength.

[0003] Phosphate cement (MPC) is a cement-based material with high early strength, rapid curing and chemical corrosion resistance. The MPC cement is used to prepare MPC-UHPC and its prefabricated components in cooperation with solid waste-based light and high-strength aggregate. On the one hand, the industrial solid waste can be used as a high-value resource, and on the other hand, it has the characteristics of ultra-early strength, without the need for special curing measures such as high-temperature steam curing, which is highly efficient and energy-saving. SUMMARY

[0004] In view of the above prior art, the present application provides a light aggregate made of steel slag and waste ceramic, and a light MPC-UHPC prepared by combining phosphate cement, which can meet the multiple requirements of resource utilization, environmental protection, lightness and high performance.

[0005] The present application provides a light aggregate, which comprises steel slag, waste ceramic and active admixture.

[0006] Preferably, the steel slag accounts for 60-70% by mass fraction, the waste ceramic accounts for 20-30% by mass fraction, and the active admixture accounts for 5-10% by mass fraction.

[0007] The present application also provides a preparation method of the light aggregate, which comprises the following steps:

[0008] Step 1: The steel slag and the waste ceramic are respectively crushed to a particle size of less than 2 mm, sieved to remove fine particles, and the oxides in the steel slag and the dust on the surface of the waste ceramic are removed. After washing with water, dry at 80℃ for 1-2h to reduce the water content and prevent adverse reactions in the subsequent process; the selection of the steel slag and the waste ceramic should be uniform and free of harmful impurities. The steel slag contains calcium, silicon, iron and other mineral components, and the waste ceramic has good pore structure and high durability;

[0009] Step 2: Stir the steel slag, waste ceramic powder and active admixture in a blender in a certain proportion, add an appropriate amount of water to make the moisture content of the mixture reach 10%-12%, and ensure uniform granulation to avoid overdrying or overwetting; the active admixture can be silica fume and nano silicon oxide, silica fume can improve the interface performance of the aggregate, and nano silicon oxide can enhance the overall strength and compactness;

[0010] Step 3: Granulate the mixture using a rotary disc granulator or a roller granulator, the particle size of the granulated aggregate is 0.5-4mm, which is suitable for lightweight UHPC, the granulation time is 10-15min to ensure uniform particles, and after granulation, the aggregate is dried at 80℃ for 2-3h to remove excess water to avoid excessive expansion of the pore structure during sintering;

[0011] Step 4: Put the dried aggregate into a high-temperature kiln, gradually heat it to 1000-1200℃ at a heating rate of 10-15℃ / min, and keep it at 1000-1200℃ for 20-30min, a temperature higher than 1000℃ can promote the full reaction of the components of steel slag and waste ceramic to form a dense surface structure, and after sintering, it is cooled to room temperature, usually by air cooling or water spray cooling method to stabilize the pore structure and microstructure; the high-temperature sintering treatment makes the aggregate form a porous structure inside, which can not only reduce the density of the aggregate but also ensure high strength;

[0012] Step 5: After sintering, immerse the aggregate in a 1%-2% silane coupling agent solution for 5-10min, which helps to improve the adhesion between the aggregate and the cement matrix and reduce the water absorption; after silane coupling agent treatment, further spray nano silicon oxide or nano aluminum oxide solution (0.5%-1% concentration) to form a thin layer coating to enhance the durability of the aggregate, and the coated aggregate is dried at 80℃ for 1-2h to ensure complete curing of the coupling agent and nano coating and improve the surface properties of the aggregate.

[0013] The lightweight aggregate prepared from steel slag and waste ceramic has a density of 500-900kg / m³ and a compressive strength of 15-30MPa.

[0014] The application also provides the use of the lightweight aggregate or the lightweight aggregate prepared by the preparation method in the preparation of phosphate cement ultra-high performance concrete.

[0015] Preferably, the preparation method of the phosphate cement ultra-high performance concrete comprises the following steps:

[0016] Step 1: Add phosphate cement dry powder and lightweight aggregate to a forced mixer in a certain proportion, and stir at a speed of 90-120rpm for 1-2min to make the phosphate cement dry powder and lightweight aggregate mix uniformly;

[0017] Step 2: Continue stirring at a speed of 90-120 rpm for 2-3 min, and gradually add water during stirring to evenly distribute the cement and aggregate, and evenly coat the aggregate with the cement paste;

[0018] Step 3: Adjust the stirring speed to 250-300 rpm and continue stirring for 1-2 min to form a uniform paste;

[0019] Step 4: Pour the uniformly stirred paste into the mold and gently vibrate the mold to remove air bubbles and ensure the material is compacted;

[0020] Step 5: After pouring, cover the mold with a film and let it stand at room temperature (20-25°C) for 1-2 h, wait for the phosphate cement to initially set, then remove the mold and transfer it to a curing room for 28 d of curing.

[0021] Preferably, the mass percentage of the lightweight aggregate is 30%-50%, and the mass ratio of the phosphate cement dry powder to water is 1:0.2-0.25.

[0022] Preferably, the preparation method of the phosphate cement dry powder comprises the following steps: mixing magnesium oxide powder, phosphate, boric acid (B2O3) or borax (Na2B4O7) under dry conditions, low-speed stirring using a variable-speed mixer at a speed of 90-120 rpm for 5-10 min to avoid particle agglomeration and ensure uniform mixing. Adding boric acid (B2O3) or borax (Na2B4O7) can adjust the reaction rate and heat release characteristics during the hydration process.

[0023] Preferably, the magnesium oxide powder is selected from high-purity (purity ≥95%) and moderately calcined magnesium oxide powder. The reactivity of magnesium oxide depends on its calcination temperature, and the lightweight magnesium oxide powder with a calcination temperature of 700-900°C is selected in the present application, which has high chemical reactivity.

[0024] The phosphate is selected from potassium dihydrogen phosphate (KH2PO4) or ammonium dihydrogen phosphate (NH4H2PO4), which can rapidly react with magnesium oxide to form magnesium phosphate hydrate.

[0025] Preferably, the mass ratio of magnesium oxide to phosphate is 1.5-2:1, which can ensure sufficient reaction and prevent the rapid generation of magnesium phosphate.

[0026] Preferably, the addition amount of boric acid or borax is 0.5%-2% of the weight of the phosphate to adjust the setting time.

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] 1. The application converts steel slag and waste ceramics into lightweight aggregate and combines with phosphate cement to provide a MPC-UHPC material with high strength, durability and lightweight characteristics, which has excellent corrosion resistance, lightweight and high early strength, and can be applied to bridge structures, ocean engineering, underground structures, high-rise buildings and other engineering application fields that require lightweight high strength, high durability and corrosion resistance.

[0029] 2. Green environmental protection and resource utilization: The application uses steel slag and waste ceramics to make lightweight aggregate, realizing efficient utilization of solid waste resources and having dual benefits of environmental protection and economy.

[0030] 3. Lightweight and high strength: The application uses lightweight aggregate and MPC matrix material to significantly reduce the weight of MPC-UHPC material while ensuring high strength, expanding its application scenarios.

[0031] 4. Rapid solidification and convenient construction: The rapid setting of MPC makes lightweight MPC-UHPC material suitable for rapid construction, shortening the construction period and improving construction efficiency. DETAILED DESCRIPTION

[0032] In order to make the technical means, creative characteristics and purposes achieved by the application easy to understand, the application will be further described below in combination with specific embodiments.

[0033] Embodiment 1: A preparation method of phosphate cement ultra-high performance concrete, comprising the following steps:

[0034] Step 1: Add phosphate cement dry powder and lightweight aggregate in proportion into a forced stirrer, stir at a speed of 100 rpm for 1.5 min, so that the phosphate cement dry powder and the lightweight aggregate are uniformly mixed;

[0035] Step 2: Continue to stir at a speed of 100 rpm for 2.5 min, and gradually add water during the stirring process, so that the cement and the aggregate are uniformly distributed, and the aggregate and the cement paste are uniformly wrapped;

[0036] Step 3: Adjust the stirring speed to 270 rpm and continue to stir for 1.5 min to form a uniform slurry;

[0037] Step 4: Pour the uniformly stirred slurry into a mold, gently vibrate the mold to remove air bubbles and ensure the density of the material;

[0038] Step 5: After pouring, cover the film at room temperature for 1.5 h, wait for the initial setting of phosphate cement, then remove the mold and transfer it to a curing room for 28 d curing.

[0039] The mass percentage of the lightweight aggregate is 40%, and the mass ratio of the phosphate cement dry powder and water is 1:0.23.

[0040] Further, the preparation method of the light-weight aggregate comprises the following steps:

[0041] Step 1: crush the steel slag and waste ceramic to a particle size of less than 2 mm respectively, sieve, remove the oxides in the steel slag and the dust on the surface of the waste ceramic, wash with water, and then dry at 80℃ for 1.5h;

[0042] Step 2: mix the steel slag, waste ceramic powder and active admixture in a certain proportion in a blender, and add an appropriate amount of water to make the moisture content of the mixture reach 11%;

[0043] Step 3: use a rotary disc granulator or a roller granulator to granulate the mixture, the aggregate particle size after granulation is 3mm, the granulation time is 12min, and after granulation, the aggregate is dried at 80℃ for 2.5h to remove excess water;

[0044] Step 4: put the dried aggregate into a high-temperature kiln, gradually heat to 1100℃ at a heating rate of 12℃ / min, keep sintering at 1100℃ for 25min, and then cool to room temperature by air cooling;

[0045] Step 5: immerse the sintered aggregate in a 1.5% silane coupling agent solution for 8min, further spray a nano-silicon oxide or nano-aluminum oxide solution (0.7% concentration) after silane coupling agent treatment, form a thin layer coating, and the coated aggregate is dried at 80℃ for 1.5h.

[0046] Among them, the steel slag is 65%, the waste ceramic is 25%, and the active admixture is 10% by mass percentage.

[0047] Further, the preparation method of the phosphate cement dry powder comprises the following steps: mixing magnesium oxide powder, phosphate, and boric acid under dry conditions, using a variable speed blender to stir at low speed, and stirring at a speed of 100rpm for 7min.

[0048] Among them, the mass ratio of the magnesium oxide powder to the phosphate is 1.8:1. The addition amount of the boric acid is 1% of the weight of the phosphate.

[0049] After performance testing, the compressive strength of the phosphate cement ultra-high performance concrete prepared in this embodiment is 120 MPa (28-day curing age), and the dry density is 1900kg / m³.

[0050] Embodiment 2: A preparation method of a phosphate cement ultra-high performance concrete, comprising the following steps:

[0051] Step 1: Add phosphate cement dry powder and lightweight aggregate into a forced mixer in proportion, stir for 2 min at a speed of 90 rpm, so that the phosphate cement dry powder and lightweight aggregate are mixed evenly;

[0052] Step 2: Continue stirring at a speed of 90 rpm for 3 min, and gradually add water during stirring, so that the cement and aggregate are evenly distributed, and the aggregate and cement paste are evenly wrapped;

[0053] Step 3: Adjust the stirring speed to 250 rpm, continue stirring for 2 min, and form a uniform paste;

[0054] Step 4: Pour the uniformly stirred paste into a mold, gently vibrate the mold to expel air bubbles, and ensure the compactness of the material;

[0055] Step 5: After casting, cover the film at room temperature for 1 h, wait for the phosphate cement to initial set, then remove the mold and transfer to a curing room for 28 d curing.

[0056] Among them, the mass percentage of the lightweight aggregate is 50%, and the mass ratio of the phosphate cement dry powder and water is 1:0.2.

[0057] Further, the preparation method of the lightweight aggregate comprises the following steps:

[0058] Step 1: Crush the steel slag and waste ceramic to a particle size of less than 2 mm respectively, sieve, remove the oxides in the steel slag and the dust on the surface of the waste ceramic, wash with water, and then dry at 80℃ for 2 h;

[0059] Step 2: Stir and mix the steel slag, waste ceramic powder and active admixture in a certain proportion in a mixer, and add an appropriate amount of water to make the moisture content of the mixture reach 10%;

[0060] Step 3: Granulate the mixture by using a rotary disc granulator or a roller granulator, the particle size of the aggregate after granulation is 4 mm, the granulation time is 10 min, and after granulation, the aggregate is dried at 80℃ for 3 h to remove excess water;

[0061] Step 4: Send the dried aggregate into a high-temperature kiln, gradually heat to 1200℃ at a heating rate of 10℃ / min, keep sintering at 1200℃ for 20 min, and then cool to room temperature by water spraying;

[0062] Step 5: Soak the sintered aggregate in a 2% silane coupling agent solution for 5 min, further spray a nano-silicon oxide or nano-aluminum oxide solution (1% concentration) after silane coupling agent treatment, form a thin layer coating, and dry the coated aggregate at 80℃ for 1 h.

[0063] The steel slag is 70%, the waste ceramic is 25%, and the active admixture is 5% by mass percentage.

[0064] Further, the preparation method of the phosphate cement dry powder comprises the following steps: mixing the magnesium oxide powder, the phosphate, and the borax under dry conditions, and stirring at a low speed using a variable-speed mixer at a speed of 120 rpm for 5 min.

[0065] The mass ratio of the magnesium oxide powder to the phosphate is 2:1. The borax is added in an amount of 0.5% of the weight of the phosphate.

[0066] Through performance testing, the compressive strength of the phosphate cement ultra-high performance concrete prepared in this embodiment is 100 MPa (28-day curing age), and the dry density is 1800 kg / m³.

[0067] Embodiment 3: A preparation method of a phosphate cement ultra-high performance concrete, comprising the following steps:

[0068] Step 1: The phosphate cement dry powder and the lightweight aggregate are added into a forced mixer in a proportion, and stirred at a speed of 120 rpm for 1 min, so that the phosphate cement dry powder and the lightweight aggregate are uniformly mixed;

[0069] Step 2: The stirring is continued at a speed of 120 rpm for 2 min, and water is gradually added during the stirring, so that the cement and the aggregate are uniformly distributed, and the aggregate and the cement paste are uniformly wrapped;

[0070] Step 3: The stirring speed is adjusted to 300 rpm, and the stirring is continued for 1 min to form a uniform paste;

[0071] Step 4: The uniformly stirred paste is poured into a mold, and the mold is gently vibrated to remove air bubbles to ensure the compactness of the material;

[0072] Step 5: After casting, a film is placed at room temperature for 2 h to wait for the initial setting of the phosphate cement, and then the mold is removed and transferred to a curing room for curing for 28 d.

[0073] The mass percentage of the lightweight aggregate is 30%, and the mass ratio of the phosphate cement dry powder to water is 1:0.25.

[0074] Further, the preparation method of the lightweight aggregate comprises the following steps:

[0075] Step 1: The steel slag and the waste ceramic are respectively crushed to a particle size of less than 2 mm, sieved, and the oxides in the steel slag and the dust on the surface of the waste ceramic are removed, and then washed with water and dried at 80°C for 1 h.

[0076] Step 2: Steel slag, waste ceramic powder and active admixture are mixed in a blender, and an appropriate amount of water is added to make the moisture content of the mixture reach 12%;

[0077] Step 3: The mixture is granulated using a rotary disc granulator or a roll granulator, the aggregate particle size after granulation is 0.5mm, the granulation time is 15min, and after granulation, the aggregate is dried at 80℃ for 2h to remove excess water;

[0078] Step 4: The dried aggregate is sent into a high-temperature kiln, and the temperature is gradually increased to 1000℃ at a rate of 15℃ / min, and kept at 1000℃ for sintering for 30min, and then cooled to room temperature by air cooling;

[0079] Step 5: The sintered aggregate is immersed in a 1% silane coupling agent solution for 10min, and after silane coupling agent treatment, further spraying of nano-silicon oxide or nano-aluminum oxide solution (0.5% concentration) is carried out to form a thin layer coating, and the coated aggregate is dried at 80℃ for 2h.

[0080] Among them, the steel slag is 60%, the waste ceramic is 30%, and the active admixture is 10% by mass percentage.

[0081] Further, the preparation method of the phosphate cement dry powder comprises the following steps: mixing magnesium oxide powder, phosphate, boric acid under dry conditions, and using a variable speed mixer to stir at a low speed, and stirring at a speed of 90rpm for 10min.

[0082] Among them, the mass ratio of the magnesium oxide powder to the phosphate is 1.5:1. The addition amount of the boric acid is 2% of the weight of the phosphate.

[0083] Through performance test, the compressive strength of the phosphate cement ultra-high performance concrete prepared in the embodiment is 110 MPa (28-day curing age), and the dry density is 1850kg / m³.

[0084] The above is only an embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent scheme made by using the content of the present application specification, directly or indirectly applied in other related technical fields, is also within the patent protection scope of the present application.

Claims

1. A lightweight aggregate, characterized in that, The lightweight aggregate comprises steel slag, waste ceramics, and active admixtures; by mass percentage, the steel slag comprises 60%-70%, the waste ceramics 20%-30%, and the active admixtures 5%-10%; the preparation method of the lightweight aggregate includes the following steps: Step 1: Crush the steel slag and waste ceramics separately to a particle size of less than 2mm, sieve them to remove oxides from the steel slag and dust from the surface of the waste ceramics, wash them with water and dry them at 80℃ for 1-2 hours. Step 2: Mix steel slag, waste ceramic powder and active admixture in a certain proportion, add an appropriate amount of water to make the moisture content of the mixture reach 10%-12%; Step 3: Granulate the mixture. The aggregate particle size after granulation is 0.5-4 mm. The granulation time is 10-15 min. After granulation, dry the aggregate at 80℃ for 2-3 h to remove excess moisture. Step 4: The dried aggregate is fed into a high-temperature kiln and gradually heated to 1000-1200℃ at a heating rate of 10-15℃ / min. It is then sintered at 1000-1200℃ for 20-30 minutes. After sintering, it is cooled to room temperature. Step 5: Immerse the sintered aggregate in a 1%-2% silane coupling agent solution for 5-10 minutes. After silane coupling agent treatment, further spray with nano-silica or nano-alumina solution to form a thin coating. Dry the coated aggregate at 80°C for 1-2 hours.

2. The application of the lightweight aggregate as described in claim 1 in the preparation of phosphate cement ultra-high performance concrete.

3. The application as described in claim 2, characterized in that, The method for preparing the phosphate cement ultra-high performance concrete includes the following steps: Step 1: Mix the phosphate cement powder and the lightweight aggregate at a speed of 90-120 rpm for 1-2 minutes in proportion to ensure that the phosphate cement powder and the lightweight aggregate are mixed evenly. Step 2: Continue stirring at a speed of 90-120 rpm for 2-3 minutes, and gradually add water during the stirring process to ensure that the cement and aggregate are evenly distributed and that the aggregate and cement paste are evenly coated. Step 3: Adjust the stirring speed to 250-300 rpm and continue stirring for 1-2 minutes to form a uniform slurry; Step 4: Pour the well-stirred slurry into the mold and gently shake the mold to remove air bubbles; Step 5: After pouring, cover with a film and let stand at room temperature for 1-2 hours to allow the phosphate cement to set initially. Then remove the formwork and transfer to the curing room for 28 days of curing.

4. The application as described in claim 3, characterized in that, The lightweight aggregate comprises 30%-50% by mass, and the mass ratio of the phosphate cement dry powder to water is 1:0.2-0.

25.

5. The application as described in claim 3, characterized in that, The preparation method of the phosphate cement dry powder includes the following steps: mixing magnesium oxide powder, phosphate, boric acid or borax under dry conditions, and stirring at a speed of 90-120 rpm for 5-10 min.

6. The application as described in claim 5, characterized in that, The mass ratio of magnesium oxide powder to phosphate is 1.5-2:

1.

7. The application as described in claim 5, characterized in that, The amount of boric acid or borax added is 0.5%-2% of the weight of phosphate.