Cementing material of ecological concrete and ecological concrete thereof

Abstract

The invention relates to a cementing material of ecological concrete and the ecological concrete.The cementing material comprises, by weight, 30%-40% of gypsum, 20%-30% of mineral powder, 3%-5% of kieselguhr, 6%-8% of modified zeolite and the balance sulphoaluminate cement. The preparation method comprises the following steps: preparing a chitosan solution with the mass concentration of 20% for later use, and uniformly mixing zeolite powder with SPA for later use; spraying a chitosan solution on the mixture, and then drying to obtain the modified zeolite. According to the cementing material disclosed by the invention, the gypsum, the mineral powder, the diatomite, the modified zeolite and the aluminum sulfate cement are compounded into a plurality of materials, the alkalinity reduction action mechanisms of different materials are different, the respective defects are mutually compensated, a synergistic effect is generated, mutual promotion is realized, and the alkalinity of the concrete is more effectively reduced. Meanwhile, the microstructure and macroscopic performance of the concrete can be improved, and the durability and stability of the concrete are improved.

Description

Technical Field

[0001] The invention relates to a cementitious material for ecological concrete and ecological concrete thereof, belonging to the field of vegetation concrete. Background Art

[0002] Ecological concrete has always been called "environmentally friendly concrete" or "vegetation concrete". It mainly refers to concrete materials that can adapt to plant growth, beautify the environment, and play a positive role in regulating ecological balance and achieving harmony between humans and nature. Generally, it has at least three characteristics: (1) It has a certain strength to prevent scouring of the slope surface and protect the slope surface from rain erosion; (2) It must have a porosity that provides a living place for plants, generally ensuring that the continuous porosity reaches 18% to 35% so that the roots of vegetation can have sufficient space for growth and development; (3) The pH value of ecological concrete must be maintained at a level that does not affect plant growth. Generally speaking, it should be ≤10 to ensure that the growth environment of plant roots is not affected. Ecological concrete is mainly made of aggregate, cementitious materials, admixtures and water mixed in proportion. Cement is generally used as cementing material. During the cement hydration process, strong alkaline hydration products such as calcium hydroxide will be produced, resulting in a strong alkaline environment. The alkalinity of ecological concrete is usually about 13, which has an adverse effect on the environment in which plants grow, and is not conducive to the early germination of plants and the long-term growth of plants in the later period, resulting in the situation that plants do not germinate or have a low growth rate in the next year. The main strategies for reducing the alkalinity of existing ecological concrete are: ① Adjusting the type of cement, which is the core method to reduce the alkalinity inside ecological concrete; ② Using acidic soil to neutralize the alkaline substances inside ecological concrete; ③ By applying alkali sealing technology, the release of alkaline components in cement can be prevented, thereby reducing the alkalinity level inside ecological concrete. The existing alkali sealing technology mainly uses DPS agent spraying. DPS agent is a water-based penetrating crystalline waterproof material; its waterproof mechanism is to produce a chemical reaction with active ingredients such as free alkali in concrete to generate stable dendrite-like crystal colloids, which effectively block the fine cracks and capillary voids inside the concrete, so that the concrete structure has a lasting waterproof function and better density and compressive strength, and the penetration depth reaches 20-30mm. This will cause the porosity of the eco-concrete to become smaller and will not allow for plant growth. Summary of the invention

[0003] The invention provides a cementitious material for ecological concrete and ecological concrete thereof, which solves the problems that the existing ecological concrete uses a single cement as a cementitious material, resulting in high alkalinity of the prepared ecological slow-setting soil, which is not conducive to plant growth, and the existing alkali sealing technology leads to small porosity.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A cementitious material for ecological concrete, which comprises, by weight percentage, 30-40% gypsum, 20-30% mineral powder, 3-5% diatomaceous earth, 6-8% modified zeolite, and the remainder is sulphoaluminate cement.

[0006] The preparation method of the modified zeolite: The preparation method of the modified zeolite: dissolve chitosan in water to form a chitosan solution with a mass concentration of 20%, and set aside; mix zeolite powder and SPA evenly, and set aside; spray the chitosan solution on the mixture, and then dry it to obtain the modified zeolite.

[0007] Furthermore, preferably: the modified zeolite, by weight percentage, consists of 5% SPA, 20% chitosan and 75% zeolite powder.

[0008] Furthermore, preferably: the cementitious material, by weight percentage, comprises 36% gypsum, 23% mineral powder, 5% diatomaceous earth, 7% modified zeolite, and the remainder is sulphoaluminate cement.

[0009] Furthermore, preferably: the mineral powder is SP95 grade or SP105 grade mineral powder.

[0010] Furthermore, preferably: the sulphoaluminate cement is 42.5 aluminium sulphate cement.

[0011] The present invention also provides an ecological concrete, which comprises, by weight percentage, 15-20% of the cementitious material of the present invention, 6-10% of fly ash, 0.1-0.3% of a water reducing agent, 2-3% of water, and the remainder being aggregate.

[0012] Furthermore, preferably: the aggregate comprises 6-10 mm crushed stone, fine sand and diatomaceous earth; the volume ratio of the 3-6 mm crushed stone, fine sand and diatomaceous earth is 85:10:5.

[0013] The method for preparing ecological concrete comprises the following steps: mixing aggregates evenly, taking half of the aggregates and mixing them evenly with a cementitious material and a water reducing agent, adding the remaining aggregates and mixing them evenly, and finally adding water and mixing them evenly to obtain ecological concrete.

[0014] Beneficial effects of the present invention:

[0015] The modified zeolite of the present invention has a good alkali-reducing effect: SAP has a high water absorption property and can absorb and retain moisture in concrete. The retention of moisture helps to dilute the concentration of Ca(OH)2, thereby reducing the alkalinity of concrete. At the same time, SAP also plays an internal curing role in concrete. By slowly releasing moisture, it keeps the cement paste moist, helps further hydration of cement, and generates more hydrated calcium silicate (CSH) gel, which can consume part of calcium hydroxide, thereby reducing the alkaline substances in concrete. Chitosan is a natural high molecular polymer that combines with zeolite to enhance the ion exchange capacity of zeolite. Zeolite itself has the property of ion exchange and can react with Ca(OH)2 in Ca(OH)2. 2+ Ions are exchanged, thereby reducing the amount of Ca(OH)2 and lowering the alkalinity of concrete. After chitosan is modified with zeolite, it can slowly release the alkaline substances it adsorbs, which helps to maintain a lower and more stable alkaline environment, which is more conducive to the growth of vegetation in ecological concrete.

[0016] SAP and chitosan modified zeolite effectively reduce free calcium hydroxide in concrete through mechanisms such as ion exchange and physical adsorption, thereby reducing the alkalinity of concrete. At the same time, SAP and chitosan modified zeolite can increase the porosity of concrete, create more pore space, and make concrete more porous and breathable. Such a pore structure is conducive to the penetration of water and air, providing better growth conditions for plant roots. Through the above two improvements, a more suitable growth environment can be provided for plant roots. Plant roots can be better anchored and absorb water and nutrients. It is also conducive to microbial activity and further promotes the stable growth of vegetation.

[0017] Gypsum, mineral powder, diatomite, modified zeolite and aluminum sulfate cement are used as the cementing materials of ecological concrete. Different materials have different mechanisms of action in reducing alkali, which can compensate for their respective deficiencies, produce synergistic effects, promote each other, and more effectively reduce the alkalinity of concrete. At the same time, it can also improve the microstructure and macroscopic properties of concrete, and improve its durability and stability.

[0018] The ecological concrete of the present invention adopts low-alkalinity cementitious materials with slow-release effect, composite fly ash, 6-10mm crushed stone, fine sand and diatomaceous earth and other materials, which have many advantages and mutually reinforcing effects: coarse aggregate provides the skeleton structure of concrete; fine aggregate increases the cohesion of concrete, the volcanic ash activity of fly ash reacts with Ca(OH)2 in cement to generate cementitious substances such as hydrated calcium silicate, thereby enhancing the strength and durability of concrete; diatomaceous earth helps to maintain the stability and uniformity of the concrete structure, and can effectively improve the strength of concrete. DETAILED DESCRIPTION

[0019] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] The raw materials used in the embodiments of the present invention are as follows:

[0021] Gypsum powder: 100 mesh, initial setting time: 4-6min, final setting time 8-10min.

[0022] The mineral powder is S95 grade mineral powder or S105 grade mineral powder. The embodiment of the present invention uses S105 grade mineral powder, 400 mesh.

[0023] Diatomite indicators are as follows: SiO2 content ≥ 90 (%); Fe2O3 content ≤ 1-1.5 (%); loss on ignition ≤ 6 (%); moisture content ≤ 0.1 (%); loose density ≤ 1.9-2.3 (g / cm 3 );Sieve residue ≤5(%);PH value: neutral;Specific surface area 40-60(m 2 / g).

[0024] Zeolite powder: white powder with 7d and 28d activity indexes of 91.3% and 95.5% respectively and a median particle size of 12.8 μm, purchased from Gongyi Yuanheng Water Purification Material Factory.

[0025] SAP was purchased from Qingdao Shouke New Materials Co., Ltd., model SDK-S, mesh size: 200-300.

[0026] The sulphoaluminate cement used is 42.5 grade rapid hardening sulphoaluminate cement.

[0027] The water reducer used is cement-based PC-1021 water reducer produced by Langfang Hongmao Energy Saving Technology Co., Ltd.

[0028] Fly ash: Class II fly ash, Henan Borun Refractory Material Co., Ltd. Other raw materials can be used as building materials without special requirements.

[0029] Examples 1-5 investigate the effects of modified zeolite compositions of different compositions on ecological concrete

[0030] An ecological concrete comprises, by weight percentage, 20% of cementitious material, 0.2% of water reducing agent, 6% of fly ash, 3% of water, and the remainder is aggregate; the aggregate comprises 6-10 mm crushed stone, fine sand and diatomaceous earth; the volume ratio of 6-10 mm crushed stone, fine sand and diatomaceous earth is 85:10:5; the preparation method comprises the following steps: mixing the aggregate evenly, then taking half of the aggregate and mixing them evenly with the cementitious material and the water reducing agent, then adding the remaining aggregate and mixing evenly, and finally adding water and mixing evenly, so as to obtain the ecological concrete.

[0031] The cementitious material, in terms of weight percentage, includes 35% gypsum, 25% mineral powder, 5% diatomaceous earth, 6% modified zeolite, and the balance is sulphoaluminate cement. All raw materials are mixed evenly to obtain the cementitious material. The preparation method of the modified zeolite is as follows: dissolve chitosan in water to form a chitosan solution with a mass concentration of 20%, and set aside; mix zeolite powder and SPA evenly, and set aside; spray the chitosan solution on the mixture, and then dry it to obtain the modified zeolite. Example 2 does not contain chitosan, and zeolite powder can be directly mixed with SPA. The raw material composition of the modified zeolite is shown in Table 1.

[0032] Table 1 Raw material composition of different modified zeolites

[0033]

[0034] Example 6

[0035] The raw material composition is the same as that of Example 1, except that the zeolite reforming method is to directly mix the raw materials.

[0036] The concrete prepared in Examples 1-6 was tested for performance, and the specific method is as follows:

[0037] 1. Determination of compressive strength

[0038] Ecological concrete specimens of 150mm×150mm×150mm were prepared with a water-cement ratio of 0.3 and a target porosity of 25%. After the specimens were formed and demolded, they were placed in a standard curing room (the temperature of the standard concrete curing room was 20±1℃ and the relative humidity was above 95%RH) and cured to the specified age. According to the provisions of GB / T 50081-2019 "Standard Test Method for Mechanical Properties of Ordinary Concrete", the compressive strength of the specimens at 7d and 28d were measured respectively.

[0039] 2. Porosity determination

[0040] Take out the specimens that have been cured to the specified age, and use an electronic balance to measure their mass under standard curing conditions. Place the specimens in an oven and bake for 24 hours, then take them out and use an electronic balance to measure their drying mass. Soak the specimens in water, and use an immersion balance to measure their water-soaked mass after 24 hours. Calculate the effective porosity P1 and total porosity P2 of the eco-concrete, respectively, as shown in formula (1) and formula (2).

[0041]

[0042] Where: v—apparent volume of the specimen, cm 3 ;

[0043] m1—mass of the specimen under standard curing conditions, g;

[0044] m2—the drying mass of the specimen after being placed in the oven for 24 hours, g;

[0045] m3—The water mass of the specimen after being immersed in water for 24 hours, g.

[0046] 3. Determination of sand penetration rate

[0047] After cleaning and drying the sand, screen out the sand with an average particle size of 2.36 to 4.75 mm. Place the 150mm×150mm×150mm specimen into the specimen fixture and fix it on a sieve with an aperture greater than 4.75 mm. Take 100g of the screened sand and sprinkle it evenly on the surface of the specimen. Clamp the sieve, receiving tray and sieve cover with the specimen on a vibrating screen (number of rotations: 290±6 times / min, number of taps: 156±3 times / min) and vibrate for 5 minutes. After stopping the machine, weigh the mass of the sand in the receiving tray and calculate the percentage of the mass of the sand that passes through the specimen to the total mass.

[0048] 4. Alkalinity determination

[0049] A 150mm×150mm×150mm cement paste specimen was prepared and cured for 7 days after forming. The specimen was placed in a sealed container filled with 10L distilled water and immersed. After 24h, 48h and 72h, the pH value of the aqueous solution after immersion was tested to reflect the alkalinity between the pores.

[0050] 5.Planting performance

[0051] Natural brown soil is used as the basic material, and organic fertilizer, ferrous sulfate and SAP absorbent resin are added. After mixing evenly, they are crushed to make the particles finely crushed and used as the pore filling matrix. The weight ratio of brown soil, organic fertilizer, ferrous sulfate and SAP absorbent resin is 75:23:1:1. The organic fertilizer uses the biological organic fertilizer of Hebei Haowo Fertilizer Technology Co., Ltd.

[0052] The pore-filling matrix is ​​added with water to form a slurry with an expansion of 200-230 mm. The slurry is poured onto the surface of the test block and the pores are filled by the deadweight of the slurry. When a small amount of slurry flows out from under the test piece, stop. During the process, the side of the porous concrete can be gently tapped so that the matrix can fully fill the pores.

[0053] Then the ecological concrete specimens were laid on the soil, and 3 cm of culture medium material was laid on it. The culture medium material was: brown soil and organic fertilizer, with a weight ratio of 75:25. Then, tall fescue seeds were evenly sown in the soil layer at 20 g of tall fescue seeds per square meter, and finally 2 cm of culture medium material was sprinkled on it. The soil was watered and planted in a greenhouse with an ambient temperature of 25-30 ° C and sufficient light. During the planting process, equal amounts of water were kept in the morning and evening.

[0054] After 15 days, the number of tall fescue seedlings in an area of ​​100 mm × 100 mm in each specimen was determined. After 40 days, the tall fescue in an area of ​​100 mm × 100 mm in each specimen was cut along the substrate surface, collected, weighed, and the aboveground biomass was calculated.

[0055] Table 2 Results of the effects of different modified zeolite compositions on the performance of ecological concrete

[0056]

[0057]

[0058] As shown in Table 1, the modified zeolite of the present invention can effectively reduce the alkalinity while maintaining the good strength and porosity of the ecological concrete. The pH value of 24h is 7.2 and the pH value of 72h is 8.1. It can be seen that the alkalinity of the ecological concrete of the present invention does not increase much over time, which is beneficial to the growth and development of plants. Compared with Example 2 without adding chitosan, the number of tall fescue seedlings increased by 61.5% and the aboveground biomass increased by 123.2%; compared with Example 3 without adding SPA, the number of tall fescue seedlings increased by 82.6% and the aboveground biomass increased by 152.6%. As shown in Example 6, the present invention can effectively reduce the release rate of alkali in the ecological concrete by coating SPA and zeolite powder with chitosan, so that it is beneficial to the growth and development of plants.

[0059] Examples 7-11 Investigating the effects of different diatomite compositions on ecological concrete

[0060] An ecological concrete comprises, by weight percentage, 20% of cementitious material, 0.2% of water reducing agent, 6% of fly ash, 3% of water, and the remainder being aggregate; the aggregate comprises 6-10 mm crushed stone, fine sand and diatomaceous earth; and the volume ratio of 6-10 mm crushed stone, fine sand and diatomaceous earth is 85:10:5.

[0061] The preparation method comprises the following steps: mixing the aggregates evenly, then taking half of the aggregates and mixing them evenly with the cementitious material and the water reducing agent, then adding the remaining aggregates and mixing them evenly, and finally adding water and mixing them evenly to obtain the ecological concrete.

[0062] The cementitious material, by weight percentage, includes 35% gypsum, 25% mineral powder, 0%, 1%, 3%, 5%, 7% diatomite respectively, 6% modified zeolite, and the balance is sulphoaluminate cement. All raw materials are mixed evenly to obtain the cementitious material. The preparation method of the modified zeolite is as follows: dissolve chitosan in water to form a chitosan solution with a mass concentration of 20%, and set aside; mix zeolite powder and SPA evenly, and set aside; spray the chitosan solution on the mixture, and then dry it to obtain the modified zeolite. The modified zeolite, by weight percentage, consists of 5% SPA, 20% chitosan and 75% zeolite powder.

[0063] The properties of the concrete prepared in Examples 6-10 were measured. The specific method was as shown in Example 1. The results are shown in Table 3.

[0064] Table 3 The results of the test on the performance of ecological concrete with different diatomite compositions

[0065]

[0066] As shown in Table 3, diatomite has a porous structure and can absorb some alkaline substances and reduce their movement in concrete. This physical adsorption helps to reduce the alkalinity of concrete and effectively improve its strength. As the amount of addition increases, although too much diatomite will adsorb alkaline substances, the content of cementitious materials will decrease, resulting in the rapid dissolution of the alkali adsorbed in the diatomite, resulting in its subsequent high alkalinity, which is not conducive to the growth and development of plants.

[0067] Example 12

[0068] It is basically the same as Example 1, except that: an ecological concrete, in terms of weight percentage, includes 15% cementitious material, 10% fly ash, 0.2% water reducer, 2% water, and the remainder is aggregate; the aggregate includes 6-10mm crushed stone, fine sand and diatomaceous earth; the volume ratio of 6-10mm crushed stone, fine sand and diatomaceous earth is 85:10:5.

[0069] The gelling material comprises, by weight percentage, 36% gypsum, 23% mineral powder, 5% diatomaceous earth and 7% modified zeolite.

[0070] After testing: the pH value at 72 hours was 8.9, the compressive strength at 28 days was: 20.36MPa; the number of tall fescue seedlings: 46 roots; the aboveground biomass: 3867g.

[0071] Example 13

[0072] It is basically the same as Example 1, except that: an ecological concrete, in terms of weight percentage, includes 18% cementitious material, 8% fly ash, 0.1% water reducer, 3% water, and the remainder is aggregate; the aggregate includes 6-10mm crushed stone, fine sand and diatomaceous earth; the volume ratio of 6-10mm crushed stone, fine sand and diatomaceous earth is 85:10:5.

[0073] The gelling material comprises, by weight percentage, 30% gypsum, 30% mineral powder, 4% diatomaceous earth and 8% modified zeolite.

[0074] After testing: the pH value at 72 hours was 9.3, the compressive strength at 28 days was: 19.12MPa; the number of tall fescue seedlings: 43 roots; the aboveground biomass: 3526g.

[0075] Embodiment 14

[0076] It is basically the same as Example 1, except that: an ecological concrete, in terms of weight percentage, includes 17% cementitious material, 8% fly ash, 0.2% water reducer, 3% water, and the remainder is aggregate; the aggregate includes 6-10mm crushed stone, fine sand and diatomaceous earth; the volume ratio of 6-10mm crushed stone, fine sand and diatomaceous earth is 85:10:5.

[0077] The gelling material comprises, by weight percentage, 40% gypsum, 20% mineral powder, 3% diatomaceous earth and 8% modified zeolite.

[0078] After testing: the pH value at 72 hours was 9.1, the compressive strength at 28 days was: 20.13MPa; the number of tall fescue seedlings: 44 roots; the aboveground biomass: 3628g.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A cementitious material for ecological concrete, characterized in that: According to weight percentage, it includes 30-40% gypsum, 20-30% mineral powder, 3-5% diatomite, 6-8% modified zeolite, and the balance is sulphoaluminate cement. The preparation method of the modified zeolite: The preparation method of the modified zeolite: dissolve chitosan in water to form a chitosan solution with a mass concentration of 20%, and set aside; mix zeolite powder and SPA evenly, and set aside; spray the chitosan solution on the mixture, and then dry it to obtain the modified zeolite.

2. The gelling material according to claim 1, characterized in that: The modified zeolite is composed of 5% SPA, 20% chitosan and 75% zeolite powder according to weight percentage.

3. The gelling material according to claim 1, characterized in that: Calculated by weight percentage, the invention comprises 36% gypsum, 23% mineral powder, 5% diatomaceous earth, 7% modified zeolite, and the balance is sulphoaluminate cement.

4. The gelling material according to claim 1, characterized in that: The mineral powder is SP95 grade or SP105 grade mineral powder.

5. The gelling material according to claim 1, characterized in that: The aluminum sulfate cement is 42.5 aluminum sulfate cement.

6. An ecological concrete, characterized in that: Calculated by weight percentage, the cementitious material comprises 15-20% of any one of claims 1 to 5, 6-8% of fly ash, 0.1-0.3% of a water reducing agent, 2-3% of water, and the balance is aggregate.

7. The ecological concrete according to claim 6, characterized in that: The aggregate comprises 6-10 mm crushed stone, fine sand and diatomaceous earth; the volume ratio of the 6-10 mm crushed stone, fine sand and diatomaceous earth is 85:10:

5.

8. A method for preparing ecological concrete as claimed in claim 6, characterized in that: Mix the aggregates evenly, then take half of the aggregates and mix them evenly with the cementitious material and water reducer, then add the remaining aggregates and mix evenly, and finally add water and mix evenly to obtain ecological concrete.

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