• 专利附录
  • 专利说明
  • 权利要求
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    • 专利摘要:
    The present disclosure relates to the technical field of building materials, particularly relating to a preparation method of magnesium phosphate cement (MPC) modified recycled coarse aggregates (RCA), obtained modified RCA and application of the MPC modified RCA. The method includes the following steps: l) crushing and classifying waste concrete to obtain RCA having a particle size of 5-25 mm; 2) soaking the obtained RCA into water to reach the water absorption-saturation state, and then filtering to obtain the soaked RCA, and 3) mixing the soaked RCA with dry MPC powder, stirring the mixture until RCA particles are uniformly coated with the dry MPC powder, and filtering to obtain MPC modified RCA. In the present disclosure, a pulling effect can be formed at the two sides of the interfaces between the RCA and new mortar; the mechanical anchoring forces are formed at the interfaces; the interfacial strength is significantly increased; and the aim of increasing the overall strength of the recycled concrete is achieved. Meanwhile, the modification process of recycled aggregates is further simplified and the production efficiency is elevated as well.
    公开号:NL2028676A
    申请号:NL2028676
    申请日:2021-07-09
    公开日:2022-02-28
    发明作者:Fan Jianping；Wu Qiaoyun；Chen Xuyong；Xiao Xuehao
    申请人:Wuhan Inst Technology；
    IPC主号:
    专利说明:

    Preparation method of magnesium phosphate cement (MPC) modified recycled coarse aggregates (RCA), obtained modified RCA and application of MPC modified RCA
    TECHNICAL FIELD The present disclosure relates to the technical field of building materials, particularly relating to a preparation method of magnesium phosphate cement (MPC) modified recycled coarse aggregates (RCA), obtained modified RCA and application of the MPC modified RCA.
    BACKGROUND With the rapid development of building industry, construction wastes produced by the building industry are unprecedentedly increased. In addition to the quite amazing treatment cost of massive construction wastes, many environmental problems and social harms are caused. Management of the construction wastes started from the end of the 1980s in China, but the existing management systems, polices, laws and regulations are not perfect enough. Due to imperfect matched management policies, most of the waste construction concrete is not treated and transported to the suburb or villages, and disposed of by means of open stockpiles or landfills. Meanwhile, severe environmental pollution is caused by problems such as discarding and scattering, and dust and lime sand flying during clearing, transportation and stacking. Facing the increasingly serious environmental problems, tight land supply, and depleted mineral resources, the contradictions among humans, environment, and resources are undoubtedly aggravated by those concrete wastes, thereby affecting coordinated development of the urban ecological environment. The recycling of the waste concrete is generally regarded as one of the most effective measures/technology for solving the waste concrete problem. The waste concrete is crushed and classified to become RCA. The RCA has defects such as high water absorption rate and micro-cracks. Therefore, the RCA needs to be undergone a pretreatment for the application in recycled concrete.
    SUMMARY A purpose of the present disclosure is to further optimize a RCA modification method, and provide a RCA modification preparation method that can repair mortar attached onto the RCA and enhance interfacial bond strength of a modified material and old mortar, thereby further increasing the performance of the RCA. On one hand, threat of the waste concrete on the ecological environment is eased, and the waste concrete serving as a green building material is popularized and applied; on the other hand, the RCA is fully utilized, thereby further protecting the environment and realizing green production.
    Technical solutions provided by the present disclosure are as follows: A preparation method of magnesium phosphate cement (MPC) modified recycled coarse aggregates (RCA) includes the following steps: 1) crushing and classifying waste concrete to obtain RCA having a particle size of 5-25 mm; 2) soaking the RCA obtained in the step 1) into water to reach the water absorption-saturation state, and then filtering to obtain the soaked RCA; and 3) mixing the soaked RCA obtained in the step 2) with dry MPC powder, stirring the mixture until RCA particles are uniformly coated with the dry MPC powder, and filtering to obtain MPC modified RCA.
    Magnesium phosphate cement is called MPC for short and includes major components such as re-burned magnesium oxide and ammonium dihydrogen phosphate. Borax is additionally doped to serve as a retarder.
    For recycling of the RCA, if the RCA is not treated but directly mixed with fresh mortar, due to an interface problem existing in the two materials, the performance of the obtained composite mortar cannot meet operating requirements. In an existing method, a common method is to use ordinary Portland cement for modification. Modification with the ordinary Portland cement mainly achieves an effect of repairing cracks and holes in the RCA. Through the treatment, although compatibility of the RCA and the fresh mortar may be increased, and the performance of the fresh mortar doped with the RCA is increased to a certain extent, since there is no more bonding between the RCA and the fresh mortar, design strength of original waste concrete is still rarely achieved in the mechanical property of the recycled concrete.
    Based on the above technical solutions, after the RCA is fully soaked in water, the MPC can rapidly penetrate into the old mortar of the RCA to be subjected to a hydration reaction, thereby repairing the RCA. Further, MPC components that are not completely reacted can continue to react towards the new mortar in a water environment of fresh concrete; and finally, a pulling effect is formed at the two sides of the interfaces of the RCA and the new mortar, thereby further forming mechanical anchorage and significantly increasing the interfacial strength. Specifically, the soaking time of the RCA in the water in the step 2) is not less than 24 h.
    Specifically, a weight of the soaked RCA obtained in the step 2) is gained by 4-13% compared with that of the RCA obtained in the step 1). Specifically, in the step 3), a weight percentage of a dosage of the dry MPC powder and a weight gain of the soaked RCA obtained in the step 2) is 50-70%. Specifically, in the step 3), a weight ratio of magnesium to phosphorus in the MPC is (1.8-2.2):1. Specifically, in the step 3), a weight percentage ratio of the soaked RCA obtained in the step 2)
    to the dry MPC powder is (92-98):(2.5-6). The present disclosure further provides magnesium phosphate cement (MPC) modified recycled coarse aggregates (RCA) obtained by the preparation method of the magnesium phosphate cement (MPC) modified recycled coarse aggregates (RCA). The present disclosure further provides an application of the magnesium phosphate cement (MPC) modified recycled coarse aggregates (RCA), wherein the MPC modified RCA serves as concrete aggregate.
    According to the magnesium phosphate cement (MPC) modified recycled coarse aggregates (RCA) provided by the present disclosure, an apparent density is increased by 0.4-0.8%; a stacking density is increased by 1.5-1.8%; a water absorption rate is increased by 60-75%; a crush index is increased by 20-25%; and concrete slump or concrete workability is increased by 20-24%. The MPC modified RCA is fully suitable to serve as the concrete aggregate. Compared with the prior art, the present disclosure has beneficial effects as follows: In the present disclosure, the RCA is modified with the MPC. 1) After contacting with water absorbed by the RCA, the MPC rapidly reacts and gradually extends to the RCA so as to fill micro-cracks in the mortar attached onto the RCA; and 2) with the adoption of the dry MPC powder and the soaked RCA, an interface thickness between the MPC and the attached mortar is significantly decreased compared with that in the prior art. Thus, the strength of the RCA is significantly increased. Compared with the traditional cement grout modification method, the method in the present disclosure is simple in procedure, convenient to operate and high in controllability.
    BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a flow chart of a preparation method of magnesium phosphate cement (MPC)
    modified recycled coarse aggregates (RCA) provided by the present disclosure.
    DETAILED DESCRIPTION Principles and features of the present disclosure will be described below. Illustrated 5 embodiments are merely used for explaining the present disclosure, rather than limiting a scope of the present disclosure. The present disclosure provides a preparation method of magnesium phosphate cement (MPC) modified recycled coarse aggregate (RCA), including the following steps: 1) waste concrete was crushed by a jaw crusher and classified to obtain RCA having a particle size of 5-25 mm; 2) the RCA obtained in the step 1) was soaked into water for 24 h, and filtered; and 4 Kg of the soaked RCA was taken for determining a water absorption rate; and 3) the soaked RCA in the step 2) was poured into a container filled with MPC having a magnesium-phosphorus ratio of 2:1; the mixture was stirred to ensure that the aggregate was uniformly coated with the MPC powder; and the mixture was filtered, thereby obtaining the MPC modified RCA. In the step 1), after being preliminarily crushed into small blocks and removing obvious impurities, the waste concrete may be crushed in the jaw crusher and then classified so as to obtain the RCA.
    In the step 2), when the RCA was soaked, a water surface shall be 5 mm higher than the RCA at least. In the step 3), the adopted modified material is MPC (a magnesium phosphate cement based material); the MPC includes major components such as re-burned magnesium oxide and ammonium dihydrogen phosphate; borax is additionally doped to serve as a retarder; wherein, a ratio of magnesium to phosphorus is 2:1; the MPC is powdered; and a total dosage of the MPC is 3/5 of a water absorption amount of the RCA.
    The present disclosure will be further described below by virtue of specific embodiments. It should be indicated that, embodiments below shall not explained as a limitation to the present disclosure. Embodiment 1 1) Waste concrete was crushed by a jaw crusher and classified to obtain RCA having a particle size of 5-25 mm; 2) the RCA obtained in the step 1) was soaked into water for 24 h, and filtered; and 4 Kg of the soaked RCA was taken for determining a water absorption rate (the water absorption rate of the RCA determined in the present embodiment was 7.3%); and 3) the soaked RCA in the step 2) was poured into a container filled with MPC having a magnesium-phosphorus ratio of 2:1 (the container included the following components in percentage by weight: 95.8% of RCA and 4.2% of MPC); the mixture was stirred to ensure that the aggregate was uniformly coated with the MPC powder; and the mixture was filtered, thereby obtaining the MPC modified RCA. Embodiment 2 1) Waste concrete was crushed by a jaw crusher and classified to obtain RCA having a particle size of 5-25 mm; 2) the RCA obtained in the step 1) was soaked into water for 24 h, and filtered, and 4 Kg of the soaked RCA was taken for determining a water absorption rate (the water absorption rate of the RCA determined in the present embodiment was 12.6%); and
    3) the soaked RCA in the step 2) was poured into a container filled with MPC having a magnesium-phosphorus ratio of 2:1 (the container included the following components in percentage by weight: 93.0% of RCA and 7.0% of MPC); the mixture was stirred to ensure that the aggregate was uniformly coated with the MPC powder; and the mixture was filtered, thereby obtaining the MPC modified RCA.
    Embodiment 3 1) Waste concrete was crushed by a jaw crusher and classified to obtain RCA having a particle size of 5-25 mm; 2) the RCA obtained in the step 1) was soaked into water for 24 h, and filtered; and 4 Kg of the soaked RCA was taken for determining a water absorption rate (the water absorption rate of the RCA determined in the present embodiment was 4.9%); and
    3) the soaked RCA in the step 2) was poured into a container filled with MPC having a magnesium-phosphorus ratio of 2:1 (the container included the following components in percentage by weight: 97.1% of RCA and 2.9% of MPC); the mixture was stirred to ensure that the aggregate was uniformly coated with the MPC powder; and the mixture was filtered, thereby obtaining the MPC modified RCA.
    The above descriptions are merely preferred embodiments of the present disclosure, rather than limiting the present disclosure.
    Any modifications, equivalent replacements and improvements made within the spirit and principles of the present disclosure shall be included in the protection scope of the present disclosure.
    权利要求:
    Claims (8)
    [1]
    A production method of magnesium phosphate-cement (MPC) modified recycled raw aggregates (RCA), comprising the following steps: I) crushing and classifying waste concrete to obtain the RCA having a particle size of 5-25 mm; 2) soaking the RCA obtained in step 1) in water to reach the water absorption saturation stage, and then filtering to obtain the soaked RCA; and 3) mixing the soaked RCA obtained in step 2) with dry MPC powder, stirring the mixture until the RCA particles are evenly covered with the dry MPC powder and filtering to obtain MPC modified RCA.
    [2]
    The preparation method of the magnesium phosphate-cement (MPC) modified recycled crude aggregates (RCA) according to claim 1, wherein the soaking time of the RCA in the water in step 2) is not less than 24 hours.
    [3]
    The preparation method of the magnesium phosphate-cement (MPC) modified recycled crude aggregates (RCA) according to claim 2, wherein the weight of the soaked RCA obtained in step 2) increases by 4-13% as compared with that of the RCA obtained in step 1).
    [4]
    The production method of the magnesium phosphate-cement (MPC) modified recycled raw aggregates (RCA) according to claim 3, wherein in step 3) a weight percentage of a dose of the dry MPC powder and a weight gain of the soaked RCA obtained in step 2 ) is 50-70%.
    [5]
    The preparation method of the magnesium phosphate cement (MPC) modified recycled raw aggregates (RCA) according to claim 4, wherein in step 3) is a percentage ratio of the weight of the soaked RCA obtained in step 2) to the dry MPC powder
    (92-98):(2.5-6).
    [6]
    The production method of the magnesium phosphate-cement (MPC) modified recycled crude aggregates (RCA) according to any one of claims 1-5, wherein in step 3) a weight ratio of magnesium to phosphorus in the MPC is (1.8-2.2):1 .
    [7]
    Magnesium phosphate cement (MPC) modified recycled crude aggregates (RCA) obtained by the preparation method of the magnesium phosphate cement (MPC) modified recycled crude aggregates (RCA) according to any one of claims 1-6.
    [8]
    A use of the magnesium phosphate cement (MPC) modified recycled raw aggregates (RCA) according to claim 7, wherein the MPC modified RCA serves as a concrete aggregate.
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    同族专利:
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    引用文献:
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    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    CN202010664100.XA|CN111908817A|2020-07-10|2020-07-10|Preparation method of magnesium phosphate cement material modified recycled coarse aggregate, modified recycled coarse aggregate obtained by preparation method and application of modified recycled coarse aggregate|
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