High-strength anti-freezing concrete and preparation method thereof

Abstract

The invention belongs to the technical field of concrete, and particularly relates to high-strength anti-freezing concrete and a preparation method thereof. The high-strength anti-freezing concrete is prepared from the following components in parts by weight: 40 to 70 parts of cement, 70 to 100 parts of recycled coarse aggregate, 5 to 10 parts of charcoal, 20 to 30 parts of fly ash, 10 to 20 parts of steel slag powder, 25 to 40 parts of blast furnace slag powder, 0.1 to 0.5 part of a water reducing agent and 20 to 30 parts of water. Biochar, steel slag powder, blast furnace slag powder and fly ash are added into a ball mill, a grinding aid (10-20 wt% of ethylenediamine phosphate, 5-10 wt% of anhydrous sodium sulfate, 0.1-0.5 wt% of sulfuric acid and the balance of water) is added, an admixture is obtained after ball milling, and concrete is further prepared. The concrete prepared by the invention has excellent mechanical properties and frost resistance, and is suitable for being used in a cold environment.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete, and particularly relates to high-strength frost-resistant concrete and a preparation method thereof. Background Art

[0002] Steel slag and blast furnace slag are the smelting slags with the largest emission in the steel industry. The resource utilization of solid waste materials generated by the steel industry is a hot topic of current research. Although my country has established relevant national standards for blast furnace slag powder and steel slag powder used in cement and concrete. However, due to its porosity and the presence of calcium and magnesium oxides, etc., steel slag may lead to poor volume stability, poor early activity, poor grindability, etc., and its actual utilization rate in concrete is not ideal. Blast furnace slag is usually obtained by rapid cooling in the water quenching slag method to obtain granulated blast furnace slag, and blast furnace slag powder is prepared by grinding to improve the activity of slag. Blast furnace slag can improve the structural mechanical strength and durability of cement, but it has defects such as slow hydration rate and low early mechanical strength, which limits the application of blast furnace slag.

[0003] Most of the current research focuses on further grinding and crushing steel slag and slag to solve the technical problems of steel slag being difficult to grind, poor stability and poor hydration activity. For example, Chinese patent CN103771797A discloses a method for preparing foamed concrete blocks by mixing steel slag and slag. The steel slag used is made by vibrating mill and has a specific surface area of ​​5000m 2 / kg or more ultra-fine steel slag, the slag is made by vibration grinding and has a specific surface area of ​​6000m 2 / kg or more of ultra-fine slag. Chinese patent CN115583813A uses ultra-fine tire vertical mill to grind steel slag ultra-fine powder, and then prepares a composite admixture for concrete of slag powder-fly ash-steel slag system with slag powder and fly ash. However, these methods require high research on grinding equipment and increase production costs. Summary of the invention

[0004] Based on the technical problem of low utilization rate of steel slag and blast furnace slag in the existing concrete preparation process, the present invention aims to provide a high-strength frost-resistant concrete and a preparation method thereof.

[0005] The present invention firstly provides a high-strength frost-resistant concrete, which comprises, by weight, 40-70 parts of cement, 70-100 parts of recycled coarse aggregate, 5-10 parts of biochar, 20-30 parts of fly ash, 10-20 parts of steel slag powder, 25-40 parts of blast furnace slag powder, 0.1-0.5 parts of water reducing agent and 20-30 parts of water.

[0006] Furthermore, the high-strength frost-resistant concrete comprises, by weight: 55 parts of cement, 74 parts of recycled coarse aggregate, 5-10 parts of biochar, 20-30 parts of fly ash, 15 parts of steel slag powder, 30 parts of blast furnace slag powder, 0.2 parts of water reducer, and 20 parts of water.

[0007] The cement described in the present invention is 42.5 grade ordinary Portland cement.

[0008] The recycled coarse aggregate described in the present invention has a particle size of 5-20 mm, a water absorption rate of less than 3%, an apparent density of more than 2450 kg / m3, and a void ratio of less than 47%.

[0009] The fly ash described in the present invention has a 45μm square hole sieve residue of ≤12%, a calcium oxide content of ≤10%, and a water content of ≤1%.

[0010] The steel slag powder described in the present invention is Grade I steel slag powder with a specific surface area of ​​≥350m 2 / kg, water content ≤1%. Calcium oxide content ≤4%, 7-day activity index ≥65%.

[0011] The blast furnace slag powder of the present invention is granulated blast furnace slag powder with a specific surface area of ​​≥500m 2 / kg, 7-day activity index ≥95%, water content ≤1%.

[0012] The water reducer of the present invention is any one of aromatic, naphthalene and polycarboxylic acid, and has a bulk density of 500-600 kg / m 3 , fineness ≥98%, moisture content ≤5%.

[0013] The biochar described in the present invention is obtained by anaerobic pyrolysis of biomass.

[0014] Optionally, the biomass is wood, corn straw, wheat straw, rice straw, sorghum straw, etc. Optionally, the biochar is prepared by the following method: drying the wheat straw and crushing it, anaerobic pyrolysis at 500-700°C for 30-60min, cooling it and taking it out, crushing it, and sieving it.

[0015] Preferably, the particle size of the biochar is 100-300 mesh.

[0016] The present invention also provides a method for preparing the above-mentioned high-strength frost-resistant concrete, comprising the following steps: (1) Add biochar, steel slag powder, blast furnace slag powder and fly ash into a ball mill according to weight, add a grinding aid, and mill at a speed of 100-200 rpm for 30-60 min. Then, dry naturally to obtain an admixture.

[0017] (2) Add cement, admixtures and recycled coarse aggregate into a mixer and dry mix them at a speed of 60-100 r / min for 90-150 s to prepare dry premixed mortar; (3) Add water-reducing agent and water to the premixed mortar and stir at a speed of 60-100 r / min for 90-150 s to prepare the mixture; (4) Pour the mixture into the mold, vibrate to compact it, and cure it naturally. After demoulding, cure it in a standard curing room.

[0018] Furthermore, the amount of the grinding aid in step (1) is 5% of the total mass of the powder.

[0019] Furthermore, the grinding aid in step (1) comprises, by weight percentage, 10-20 wt% of ethylenediamine phosphate, 5-10 wt% of anhydrous sodium sulfate, 0.1-0.5 wt% of sulfuric acid and the balance of water.

[0020] Furthermore, the grinding aid in step (1) comprises, by weight percentage, 10-15 wt% ethylenediamine phosphate, 5-10 wt% anhydrous sodium sulfate, 0.1-0.5 wt% sulfuric acid and the balance water.

[0021] Furthermore, the grinding aid in step (1) comprises, by weight percentage, 10 wt% ethylenediamine phosphate, 10 wt% anhydrous sodium sulfate, 0.5 wt% sulfuric acid and the balance water.

[0022] Furthermore, the standard curing room conditions in step (4) are a temperature of 20±2°C and a relative humidity of 95%±3%, and the curing period is 28 days.

[0023] The concrete prepared by the present invention has excellent mechanical properties and antifreeze properties, and is suitable for use in cold environments, such as outdoor pavements.

[0024] Compared with the prior art, the present invention has at least one of the following beneficial effects: The present invention effectively reduces the problem of ultra-high temperature rise caused by blast furnace slag by mixing and modifying biochar, fly ash, blast furnace slag and steel slag, and simultaneously utilizes fly ash and biochar to reduce the swelling behavior of steel slag, enhance activity and increase hydration rate.

[0025] The invention improves the activity of the admixture by optimizing the grinding aid, and simultaneously improves the compression resistance and freeze-thaw resistance of the concrete. DETAILED DESCRIPTION

[0026] The present invention is described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0027] The raw materials used in the following specific examples of the present invention are as follows: The cement is P.O42.5 Portland cement.

[0028] Recycled coarse aggregate, particle size 5-20mm, water absorption rate <3%, apparent density >2450 kg / m3, void ratio <47%.

[0029] Fly ash, 45 μm square hole sieve residue ≤12%, calcium oxide content ≤10%, moisture content ≤1%.

[0030] Steel slag powder, specific surface area ≥350m 2 / kg, water content ≤1%. Calcium oxide content ≤4%, 7-day activity index ≥65%.

[0031] Granulated blast furnace slag powder, specific surface area ≥500m 2 / kg, 7-day activity index ≥95%, water content ≤1%.

[0032] The water reducing agent is a polycarboxylic acid high performance water reducing agent with a water reducing efficiency of 20-30%.

[0033] The biochar is obtained by anaerobic pyrolysis of biomass. Optionally, the biochar is prepared by the following method: drying and crushing the wheat straw, anaerobic pyrolysis at 600° C. for 30 min, cooling and taking out, and passing through a 200-mesh sieve for later use. Example 1

[0034] A high-strength thermal insulation concrete comprises, by weight, 55 parts of cement, 75 parts of recycled coarse aggregate, 10 parts of biochar, 20 parts of fly ash, 15 parts of steel slag powder, 30 parts of blast furnace slag powder, 0.2 parts of water reducing agent and 20 parts of water.

[0035] A method for preparing high-strength thermal insulation concrete comprises the following steps: (1) Add biochar, steel slag powder, blast furnace slag powder and fly ash into a ball mill according to weight, and add a grinding aid, the mass of which is 5% of the total mass of the powder. The grinding aid contains 10wt% ethylenediamine phosphate, 10wt% anhydrous sodium sulfate, 0.5wt% concentrated sulfuric acid and the balance water. The ball mill is rotated at 200rpm for 30min and naturally dried to obtain an admixture.

[0036] (2) Add cement, admixtures and recycled coarse aggregate into a mixer, and dry mix them at a speed of 60-100 r / min for 90-150 s to prepare dry powder premixed mortar; (3) Add the water reducing agent and water to the premixed mortar and stir at a speed of 60-100 r / min for 90-150 s to prepare the mixture; (4) Pour the mixture into a mold (100×100×100mm, 100×100×400mm), vibrate to compact, and naturally cure for 1 day. After demoulding, cure in a standard curing room (temperature 20±2℃, relative humidity 95%±3%) for 28 days. Example 2

[0037] The difference between this embodiment and embodiment 1 is that the amount of biochar used is 5 parts. Example 3

[0038] The difference between this embodiment and embodiment 1 is that the amount of fly ash used is 30 parts. Example 4

[0039] The difference between this embodiment and embodiment 1 is that the grinding aid is 20wt% ethylenediamine phosphate, 5wt% anhydrous sodium sulfate, 0.5wt% concentrated sulfuric acid and the balance water. Example 5

[0040] The difference between this embodiment and embodiment 1 is that no biochar is added. Example 6

[0041] The difference between this embodiment and embodiment 1 is that fly ash is not added. Example 7

[0042] The difference between this embodiment and embodiment 1 is that the grinding aids are 85 wt % of triethanolamine and 15 wt % of glycerol.

[0043] According to GB / T50081-2019 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete", the compressive strength, flexural strength and thermal conductivity were measured respectively. The results are shown in Table 1. According to GB / T50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete", a slow freezing test was carried out with 25 freeze-thaw cycles to determine the mass loss rate.

[0044] Table 1 Concrete mechanical properties and frost resistance data Sample Compressive strength (MPa) Flexural strength (MPa) Mass loss rate (%) Example 1 50.5 7.58 1.2 Example 2 45.6 6.75 1.6 Example 3 48.1 7.02 1.5 Example 4 46.2 6.90 1.3 Example 5 39.2 4.35 2.6 Example 6 35.5 4.20 2.2 Example 7 40.2 5.83 2.1 The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A high-strength frost-resistant concrete, characterized in that: The composition comprises, by weight: 40-70 parts of cement, 70-100 parts of recycled coarse aggregate, 5-10 parts of biochar, 20-30 parts of fly ash, 10-20 parts of steel slag powder, 25-40 parts of blast furnace slag powder, 0.1-0.5 parts of water reducing agent and 20-30 parts of water.

2. The high-strength frost-resistant concrete according to claim 1, characterized in that: The composition includes, by weight: 55 parts of cement, 74 parts of recycled coarse aggregate, 5-10 parts of biochar, 20-30 parts of fly ash, 15 parts of steel slag powder, 30 parts of blast furnace slag powder, 0.2 parts of water reducing agent and 20 parts of water.

3. The high-strength frost-resistant concrete according to claim 1 or 2, characterized in that: The biochar is obtained by anaerobic pyrolysis of biomass at 500-700° C. for 30-60 minutes.

4. The high-strength frost-resistant concrete according to claim 3, characterized in that: The biochar is sieved through a 100-300 mesh sieve.

5. The method for preparing high-strength frost-resistant concrete according to any one of claims 1 to 4, characterized in that: The steps include: (1) Adding biochar, steel slag powder, blast furnace slag powder and fly ash into a ball mill according to weight, and adding a grinding aid, the ball mill speed is 100-200 rpm, the ball mill is milled for 30-60 minutes, and the mixture is naturally dried to obtain an admixture; (2) Add cement, admixtures and recycled coarse aggregate into a mixer and dry mix them at a speed of 60-100 r / min for 90-150 s to prepare dry powder premixed mortar; (3) Add water-reducing agent and water to the premixed mortar and stir at a speed of 60-100 r / min for 90-150 s to prepare the mixture; (4) Pour the mixture into the mold, vibrate to compact it, and cure it naturally. After demoulding, cure it in a standard curing room.

6. The method for preparing high-strength frost-resistant concrete according to claim 5, characterized in that: The amount of the grinding aid in step (1) is 5% of the total mass of the ball mill.

7. The method for preparing high-strength frost-resistant concrete according to claim 5, characterized in that: The grinding aid in step (1) comprises, by weight percentage, 10-20 wt % of ethylenediamine phosphate, 5-10 wt % of anhydrous sodium sulfate, 0.1-0.5 wt % of sulfuric acid and the balance of water.

8. The method for preparing high-strength frost-resistant concrete according to claim 5, characterized in that: The standard curing room conditions in step (4) are a temperature of 20±2°C and a relative humidity of 95%±3% for 28 days.