Method for preparing concrete early strength nucleating agent through partial depolymerization and modification regeneration of waste PET

Abstract

The invention discloses a method for preparing a concrete early strength nucleating agent through partial depolymerization and modification regeneration of waste PET, and particularly relates to the technical field of concrete admixture preparation. A part of degradation products obtained after waste PET polyester is treated in dihydric alcohol and polyfunctional silane are subjected to chemical reaction to achieve construction of the high-specific-surface-area active spherical structure. The method for preparing the early strength nucleating agent has the advantages of simple steps, greenness, mildness, low cost, obvious early strength enhancing effect, no influence on or even improvement of the later strength, and effective reduction of the carbon emission in the waste consumption process, and the waste utilization rate is close to 100%. The surface of the prepared early-strength nucleating agent is rich in a large amount of active hydroxyl groups, the early-strength nucleating agent is easily complexed with calcium ions in concrete to form a calcium silicate hydrate gelling product, more nucleating sites are provided, the hydration rate and the early strength are effectively improved, and the early-strength nucleating agent has application prospects in the fields of road rescue, plateau construction and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete admixture preparation, and particularly relates to a method for preparing a concrete early strength nucleating agent by partially depolymerizing and modifying waste PET. Background Art

[0002] As the most important building material, concrete is widely used in roads, bridges, national defense construction and other fields. However, under the plateau climate conditions, concrete products have bottleneck problems such as long laying period and serious cracking, which seriously affect the long-term safe and stable operation of important projects. In addition, under the background of dual carbon, its high emissions and high pollution also restrict the development of related industries and the realization of carbon neutrality goals.

[0003] Concrete early strength agent is a concrete admixture with the characteristics of rapid gelation, strong adaptability and high safety. It can not only improve the strength development speed and early strength of concrete, but also effectively improve the pore structure and density. It is widely used in practical scenes such as road rescue and plateau construction, and plays a vital role in the performance of concrete. However, the early strength agents mainly used in engineering are inorganic salts such as sulfates and chlorides or organic substances such as calcium formate and triethanolamine. These early strength agents are high in cost and have large dosage in actual application. They also face bottleneck problems such as decreased corrosion resistance, poor early strength effect, and even affect the later strength. In addition, some traditional early strength agents have high carbon emissions during production and use, and are prone to produce toxic and harmful substances, causing serious pollution to the environment.

[0004] Therefore, developing new early strength agents using waste materials as a source to achieve rapid early hydration of concrete can not only effectively solve the problem of slow early strength development in low temperature environments and accelerate the progress of concrete construction, but also has important significance for the green development of the concrete industry. Summary of the invention

[0005] In view of the above problems, the present invention provides a method for preparing a concrete early strength nucleating agent by partially depolymerizing and modifying waste PET, aiming to solve at least part of the above technical problems. The characteristics are:

[0006] The construction of high specific surface area active spherical structure is achieved by chemical reaction of some degradation products of waste PET polyester treated in diol with multifunctional silane. The surface of the prepared early strength nucleating agent is rich in active hydroxyl groups, which is easy to complex with calcium ions in concrete to form hydrated calcium silicate gelling products, provide more nucleation sites, promote the acceleration of concrete hydration reaction, improve the early strength of concrete, and have little effect on the later strength, solving the problem of slow early strength development in low temperature environment.

[0007] The present invention firstly discloses a method for preparing a concrete early strength nucleating agent by partially depolymerizing and modifying waste PET, which comprises the following steps:

[0008] (1) After washing and drying the PET waste, the PET waste is crushed and put into a flask, and after adding diol and catalyst, the mixture is stirred at 190-200° C. at a certain stirring rate for 2-4 hours until the waste is completely dissolved to obtain a slurry;

[0009] (2) washing, filtering, drying, and mixing the slurry with the multifunctional silane, adding the mixture to a 250 ml three-necked flask equipped with a stirrer, a thermometer, and a condenser reflux device, heating and stirring for 1-2 hours under a nitrogen atmosphere to obtain a mixture;

[0010] (3) further purifying the cooled mixture by treating it with a dialysis bag to remove small molecules and obtain a purified liquid;

[0011] (4) The purified liquid is heated to 60-80° C. in a vacuum oven until it is completely dried, thereby obtaining an active spherical concrete early strength nucleating agent with a high specific surface area.

[0012] Furthermore, the diol in step (1) is selected from any one of ethylene glycol, propylene glycol or diethylene glycol; and the catalyst is selected from one or two of tetrabutyl titanate, zinc acetate and manganese acetate.

[0013] Furthermore, in step (1), the mass ratio of the diol to the PET waste is 1-3:1; and the amount of the catalyst added is 0.5-1.5% of the total mass of the PET waste and the diol solvent.

[0014] Furthermore, the multifunctional silane in step (2) is selected from any one of n-butyltriethoxysilane, n-octyltriethoxysilane or isobutyltriethoxysilane.

[0015] Furthermore, in step (2), the mass ratio of the multifunctional silane to the PET waste is 0.3-0.6:1; and the heating and stirring temperature is 120-130°C.

[0016] Furthermore, the molecular cutoff of the dialysis bag in step (3) is 3000, and the dialysis time is 48 hours.

[0017] The present invention also discloses a concrete early-strength nucleating agent prepared by any of the above methods. The surface of the early-strength nucleating agent is rich in a large number of active hydroxyl groups, which are easy to complex with calcium ions in concrete to form hydrated calcium silicate cementitious products, provide more nucleation sites, and promote the early hydration process of concrete. It can meet the requirements of different use environments, especially in concrete construction scenes in plateau and cold regions, and has great application potential.

[0018] Compared with the prior art, the preparation of concrete early strength nucleating agent by partial depolymerization and modified regeneration of waste PET in the present invention has the following characteristics:

[0019] (1) An early nucleating agent for concrete is prepared based on waste-derived PET polyester materials. The surface of the product is rich in active hydroxyl groups, which are easy to complex with calcium ions in concrete to form hydrated calcium silicate cementitious products. This avoids the problems of existing early strength agents, such as low early strength increase, decreased later strength and corrosion resistance, as well as high costs and excessive carbon emissions caused by complex synthesis.

[0020] (2) By controlling the type of diol, reaction time, and reaction temperature during degradation, the molecular weight and surface active group density of the partially degraded waste can be adjusted, which can be applied to different concrete usage scenarios.

[0021] (3) The method described in the present invention achieves a utilization rate of nearly 100% for waste plastics, generates no pollutants, has a significant early strength effect, increases early strength by 200%, and does not affect or even improves later strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the material preparation method process described in the embodiment of the present invention.

[0023] Figure 2 This is a scanning electron microscope image of the synthetic early strength nucleating agent described in Example 1 of the present invention.

[0024] Figure 3 It is the compressive strength of concrete 1 day, 3 days and 28 days after adding the early strength nucleating agent as described in Example 1 of the present invention. DETAILED DESCRIPTION

[0025] The present invention is specifically described below through examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art in this field can make some non-essential improvements and adjustments to the present invention based on the above content.

[0026] Embodiment 1:

[0027] Take 50g of PET waste, wash and dry it, crush it and put it into a flask, add 100g of ethylene glycol and 0.225g of zinc acetate, stir it at 190℃ at a stirring speed of 500r / min for 2h until the waste is completely dissolved to obtain slurry, wash, filter and dry the above slurry, take 10g and 3g of n-butyl triethoxysilane and add them to a 250ml three-necked flask equipped with a stirrer, a thermometer and a condenser reflux device, heat and stir for 2h under a nitrogen atmosphere, and further purify the cooled mixture by treating it with a dialysis bag with a molecular weight cutoff of 3000 for 48 hours to remove small molecular substances, and heat the purified liquid to 80℃ in a vacuum oven until it is completely dried to obtain a high specific surface area active spherical early strength nucleating agent. The obtained early strength agent is mixed with concrete aggregate at a ratio of 1:200, and the early strength of the concrete increases by 200%, and the later strength also increases by about 11%.

[0028] according to Figure 2 The results show that the synthesized early-strength nucleating agent flakes are stacked to form a spherical structure. Due to the characteristics of high specific surface area, the surface of the early-strength nucleating agent contains a large number of active hydroxyl sites, which are easy to complex with calcium ions in concrete to form hydrated calcium silicate, laying the foundation for accelerating the hydration process of concrete and improving the early strength.

[0029] according to Figure 3 The results show that the compressive strength of concrete with 0.5wt% early strength nucleating agent increased by about 200% within 24 hours, with obvious early strength effect. Moreover, the compressive strength was also improved after the hydration was basically complete in 28 days.

[0030] Embodiment 2:

[0031] Take 50g of PET waste, wash and dry it, crush it and put it into a flask, add 80g of diethylene glycol and 0.2g of zinc acetate, stir at 200℃ and 500r / min stirring speed for 3h until the waste is completely dissolved to obtain slurry, wash, filter and dry the above slurry, take 10g and 5g of n-butyltriethoxysilane and add them to a 250ml three-necked flask equipped with a stirrer, a thermometer and a condenser reflux device, heat and stir for 2h under nitrogen atmosphere, and further purify the cooled mixture by treating it with a dialysis bag with a molecular weight cutoff of 3000 for 48 hours to remove small molecular substances, and heat the purified liquid to 80℃ in a vacuum oven until it is completely dried to obtain a high specific surface area active spherical early strength nucleating agent. The obtained early strength agent is mixed with concrete aggregate at a ratio of 1:100, and the early strength of concrete increases by 150% without affecting the later strength.

[0032] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a concrete early strength nucleating agent by partially depolymerizing and modifying waste PET, comprising: (1) After washing and drying the PET waste, the PET waste is crushed and put into a flask, and after adding diol and catalyst, the mixture is stirred at 190-200° C. at a certain stirring rate for 2-4 hours until the waste is completely dissolved to obtain a slurry; (2) After washing, filtering and drying the slurry, the mixed multifunctional silane was added into a 250 ml three-necked flask equipped with a stirrer, a thermometer and a condenser reflux device, and the temperature was raised and stirred for 1-2 hours under a nitrogen atmosphere to obtain a mixture; (3) processing the cooled mixture through a dialysis bag to obtain a purified liquid; (4) The purified liquid is heated to 60-80° C. in a vacuum oven until it is completely dried to obtain a concrete early strength nucleating agent.

2. The method of claim 1, wherein: The diol in step (1) is selected from any one of ethylene glycol, propylene glycol or diethylene glycol; The catalyst is selected from one or two of tetrabutyl titanate, zinc acetate and manganese acetate.

3. The method of claim 1, wherein: The mass ratio of the diol to the PET waste in step (1) is 1-3:1; The catalyst addition amount is 0.5-1.5% of the total mass of the PET waste and the diol solvent.

4. The method of claim 1, wherein: The multifunctional silane in step (2) is selected from any one of n-butyltriethoxysilane, n-octyltriethoxysilane or isobutyltriethoxysilane.

5. The method of claim 1, wherein: In step (2), the mass ratio of the multifunctional silane to the PET waste is 0.3-0.6:1; The heating and stirring temperature is 120-130°C.

6. The method of claim 1, wherein: The molecular cutoff of the dialysis bag in step (3) is 3000, and the dialysis time is 48 hours.

7. A concrete early strength nucleating agent obtained by the method as claimed in any one of claims 1 to 6.

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