A phosphogypsum cementitious material modifier and its preparation method, phosphogypsum cementitious materials, and phosphogypsum lightweight aggregates.

Abstract

This invention provides a phosphogypsum cementitious material modifier and its preparation method, as well as phosphogypsum cementitious materials and phosphogypsum lightweight aggregates, belonging to the field of building materials technology. The phosphogypsum cementitious material modifier provided by this invention comprises, by mass parts, the following raw materials: 50-100 parts of dehydrated phase from supersulfurized phosphogypsum aggregate waste powder, 0-10 parts of fly ash, 5-20 parts of metakaolin, 0-10 parts of silica fume, 4-12 parts of quicklime, and 0-0.01 parts of gypsum retarder. The phosphogypsum cementitious material modifier provided by this invention can accelerate the setting and hardening speed of phosphogypsum lightweight aggregates with phosphogypsum cementitious materials as the main component, and improve the mechanical properties of phosphogypsum lightweight aggregates.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a phosphogypsum cementitious material modifier and its preparation method, phosphogypsum cementitious materials, and phosphogypsum lightweight aggregates. Background Technology

[0002] Phosphogypsum is an industrial byproduct of the phosphate chemical industry. Approximately five tons of phosphogypsum are produced for every ton of phosphoric acid produced. However, the utilization rate of phosphogypsum is low. Globally, only 15% of phosphogypsum is recycled as building materials, agricultural fertilizers, or for soil stabilization and remediation. This low utilization rate inevitably leads to a large accumulation of phosphogypsum, which not only occupies significant land resources but also causes serious environmental problems, polluting soil, water, and air, ultimately harming human health and ecosystems. To address this problem of large-scale phosphogypsum accumulation and improve its utilization rate, an increasing number of researchers are dedicated to studying the recycling and resource reuse of phosphogypsum.

[0003] In many application fields, using phosphogypsum to prepare cementitious materials is a feasible method, and the utilization rate of phosphogypsum is relatively high. However, when using phosphogypsum to prepare phosphogypsum cementitious materials, and then using phosphogypsum gel materials to prepare phosphogypsum lightweight aggregates, there are often disadvantages such as slow setting and poor mechanical properties. Summary of the Invention

[0004] The purpose of this invention is to provide a phosphogypsum cementitious material modifier and its preparation method, as well as phosphogypsum cementitious materials and phosphogypsum lightweight aggregates. The phosphogypsum cementitious material modifier provided by this invention can accelerate the setting and hardening speed of phosphogypsum lightweight aggregates with phosphogypsum cementitious materials as the main component, and improve the mechanical properties of phosphogypsum lightweight aggregates.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a phosphogypsum cementitious material modifier, comprising the following raw materials in parts by weight:

[0007] The mixture consists of 50-100 parts of dehydrated phase from supersulfurized phosphogypsum aggregate waste powder, 0-10 parts of fly ash, 5-20 parts of metakaolin, 0-10 parts of silica fume, 4-12 parts of quicklime, and 0-0.01 parts of gypsum retarder.

[0008] Preferably, the dehydration phase of the supersulfurized phosphogypsum aggregate waste powder includes a phosphogypsum dehydration phase, a CSH gel dehydration phase, and an aluminum phase dehydration phase; the mass ratio of the phosphogypsum dehydration phase, the CSH gel dehydration phase, and the aluminum phase dehydration phase is 60-80:15-20:15-20.

[0009] Preferably, the method for preparing the dehydrated phase of the supersulfurized phosphogypsum aggregate waste powder includes the following steps:

[0010] The waste of supersulfurized phosphogypsum aggregate is ground to obtain supersulfurized phosphogypsum aggregate powder;

[0011] The supersulfurized phosphogypsum aggregate waste powder is calcined to obtain the dehydrated phase of supersulfurized phosphogypsum aggregate waste powder.

[0012] Preferably, the particle size of the supersulfurized phosphogypsum aggregate waste powder is less than 0.15 mm; the calcination temperature is 100-200℃, the holding time is 2-4 h, and the rate of heating to the calcination temperature is 4-6℃ / min.

[0013] Preferably, the fly ash is Grade I fly ash, the total mass fraction of silicon oxide and aluminum oxide in the fly ash is greater than 50%, and the fineness of the fly ash is 600-800 mesh.

[0014] Preferably, the gypsum retarder includes at least one of protein-based gypsum retarder, alkaline phosphate retarder, and organic acid and its soluble salt retarder.

[0015] This invention provides a method for preparing the phosphogypsum cementitious material modifier described in the above technical solution, comprising the following steps:

[0016] The raw materials are mixed and ground to obtain a phosphogypsum cementitious material modifier.

[0017] This invention provides a phosphogypsum cementitious material, the raw materials of which include phosphogypsum-slag cementitious material and a phosphogypsum cementitious material modifier; the phosphogypsum cementitious material modifier is the phosphogypsum cementitious material modifier described in the above technical solution or the phosphogypsum cementitious material modifier prepared by the preparation method described in the above technical solution; the mass fraction of the phosphogypsum cementitious material modifier in the phosphogypsum cementitious material is 5-20%.

[0018] Preferably, the phosphogypsum-slag cementitious material comprises phosphogypsum, mineral powder, and silicate cement clinker, wherein the mass ratio of phosphogypsum, mineral powder, and silicate cement clinker is 50-80:10-20:4-6.

[0019] This invention provides a phosphogypsum lightweight aggregate, which is obtained by sequentially processing phosphogypsum slurry into pellets and then curing it. The raw materials for preparing the phosphogypsum slurry include phosphogypsum cementitious material and water, and the mass ratio of the phosphogypsum cementitious material to water is 1:0.25 to 1:0.28. The phosphogypsum cementitious material is the phosphogypsum cementitious material described in the above technical solution.

[0020] This invention provides a phosphogypsum cementitious material modifier. The invention uses the dehydrated phase of supersulfurized phosphogypsum aggregate waste powder as the main component, and adds metakaolin and quicklime to promote the hydration reaction between minerals, thereby promoting the rapid hydration of phosphogypsum lightweight aggregate to form a high-strength hardened body. Furthermore, this invention prepares the phosphogypsum cementitious material modifier by adding fly ash, silica fume, and gypsum retarder to the dehydrated phase of supersulfurized phosphogypsum aggregate waste powder; wherein, the addition of fly ash and silica fume introduces highly active silica and alumina, accelerating the formation of sulfoaluminate hydration products and improving the early strength of phosphogypsum slurry and phosphogypsum lightweight aggregate; the gypsum retarder helps to adjust the hydration rate of phosphogypsum. The phosphogypsum cementitious material modifier provided by this invention can accelerate the setting and hardening speed of phosphogypsum lightweight aggregate with phosphogypsum cementitious material as the main component, and improve its mechanical properties. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram showing the setting time of the phosphogypsum lightweight aggregates obtained in Examples 1-4 and Comparative Example 1. Detailed Implementation

[0023] This invention provides a phosphogypsum cementitious material modifier, comprising the following raw materials in parts by weight:

[0024] The mixture consists of 50-100 parts of dehydrated phase from supersulfurized phosphogypsum aggregate waste powder, 0-10 parts of fly ash, 5-20 parts of metakaolin, 0-10 parts of silica fume, 4-12 parts of quicklime, and 0-0.01 parts of gypsum retarder.

[0025] Unless otherwise specified, all raw materials used in this invention are commercially available products well known to those skilled in the art.

[0026] The raw materials for preparing the phosphogypsum cementitious material modifier of the present invention, by weight, include 50-100 parts, preferably 50-80 parts, of dehydrated phase of supersulfurized phosphogypsum aggregate waste powder. In the present invention, the role of the dehydrated phase of supersulfurized phosphogypsum aggregate waste powder is to promote the setting and hardening of the phosphogypsum cementitious material, fill the pores, and improve its early strength.

[0027] Based on the mass fraction of the dehydrated phase of the supersulfurized phosphogypsum aggregate waste powder, the raw materials for preparing the phosphogypsum cementitious material modifier of the present invention include 0-10 parts of fly ash, preferably 6-10 parts. In the present invention, the role of fly ash is to introduce a large amount of highly active silica and alumina, thereby accelerating the formation of sulfoaluminate hydration products and improving the early strength of phosphogypsum lightweight aggregate.

[0028] Based on the mass fraction of the dehydrated phase of the supersulfurized phosphogypsum aggregate waste powder, the raw materials for preparing the phosphogypsum cementitious material modifier of the present invention include 5-20 parts of metakaolin, preferably 8-20 parts. In the present invention, the role of metakaolin is to introduce a large amount of highly active silica and alumina, which participate extensively in the hydration reaction, accelerate the formation of sulfoaluminate hydration products, and improve the early strength and mechanical properties of the phosphogypsum lightweight aggregate.

[0029] Based on the mass fraction of the dehydrated phase of the supersulfurized phosphogypsum aggregate waste powder, the raw materials for preparing the phosphogypsum cementitious material modifier of the present invention include 0-10 parts of silica fume, preferably 4-10 parts. In the present invention, the role of silica fume is to introduce a large amount of highly active silica and alumina, thereby accelerating the formation of sulfoaluminate hydration products and improving the early strength of phosphogypsum lightweight aggregate.

[0030] Based on the mass fraction of the dehydrated phase of the superphosphogypsum aggregate waste powder, the raw materials for preparing the phosphogypsum cementitious material modifier of the present invention include 4 to 12 parts of quicklime, preferably 4 to 10 parts. In the present invention, quicklime can promote the hydration reaction between minerals, thereby improving the early strength of superphosphogypsum lightweight aggregate.

[0031] Based on the mass fraction of the dehydrated phase of the supersulfurized phosphogypsum aggregate waste powder, the raw materials for preparing the phosphogypsum cementitious material modifier of the present invention include 0-0.01 parts of gypsum retarder, preferably 0.001-0.005 parts. In the present invention, the gypsum retarder has a good retarding effect, and can significantly prolong the setting time of gypsum at a low dosage, making it easy to adjust the hydration rate of gypsum.

[0032] In this invention, the dehydrated phase of the supersulfurized phosphogypsum aggregate waste powder preferably includes a phosphogypsum dehydrated phase, a CSH gel dehydrated phase, and an aluminum phase dehydrated phase; the mass ratio of the phosphogypsum dehydrated phase, CSH gel dehydrated phase, and aluminum phase dehydrated phase is preferably 60-80:15-20:15-20, more preferably 60-70:16-18:15-16. In this invention, the supersulfurized phosphogypsum aggregate waste powder reacts rapidly with water during dehydration, solidifying and hardening; wherein, the phosphogypsum dehydrated phase can quickly saturate the sulfate and calcium ion concentrations in the system, and crystallize to obtain dihydrate gypsum filling the pores, while the CSH gel dehydrated phase and aluminum phase dehydrated phase can quickly revert to the CSH gel and aluminum phase solidified matrix, and act as seed crystals.

[0033] The method for preparing the dehydrated phase of supersulfur phosphogypsum aggregate waste powder according to the present invention includes the following steps:

[0034] The waste of supersulfurized phosphogypsum aggregate is ground to obtain supersulfurized phosphogypsum aggregate powder;

[0035] The supersulfurized phosphogypsum aggregate waste powder is calcined to obtain the dehydrated phase of supersulfurized phosphogypsum aggregate waste powder.

[0036] In this invention, the particle size of the supersulfurized phosphogypsum aggregate waste powder is preferably less than 0.15 mm, more preferably 0.1–0.15 mm. This invention does not specifically limit the grinding method; any grinding method well-known to those skilled in the art can be used. In this invention, the grinding process preferably includes: sequentially drying and physically pulverizing the supersulfurized phosphogypsum aggregate waste. The drying temperature is preferably 45–60°C, more preferably 45–50°C; the drying time is preferably 12–24 h, more preferably 20–24 h. This invention does not specifically limit the physical pulverization method; any physical pulverization method well-known to those skilled in the art can be used. The calcination temperature is preferably 100–200°C, more preferably 170–200°C; the holding time is 2–4 h, specifically 2 h, 3 h, or 4 h; and the rate of heating to the calcination temperature is 4–6°C / min, specifically 4°C / min, 5°C / min, or 6°C / min. In this invention, the calcination process preferably includes cooling. The present invention does not impose any special limitations on the cooling method and conditions; any cooling method known to those skilled in the art can be used.

[0037] In this invention, the fly ash is preferably Grade I fly ash, and the total mass fraction of silicon oxide and aluminum oxide in the fly ash is preferably greater than 50%, more preferably 79-83%; the fineness of the fly ash is preferably 600-800 mesh, more preferably 800 mesh.

[0038] In this invention, the gypsum retarder preferably includes at least one of protein-based gypsum retarder, alkaline phosphate retarder, and organic acid and its soluble salt retarder, more preferably a protein-based gypsum retarder. In this invention, the alkaline phosphate retarder is preferably a sodium polyphosphate retarder; the organic acid and its soluble salt retarder is preferably a sodium citrate retarder.

[0039] This invention also provides a method for preparing the phosphogypsum cementitious material modifier described in the above technical solution, comprising the following steps:

[0040] The raw materials are mixed and ground to obtain a phosphogypsum cementitious material modifier.

[0041] In this invention, the grinding speed is preferably 300-400 r / min, more preferably 350 r / min; the grinding time is preferably 1-2 min, specifically 1 min, 1.5 min or 2 min; the particle size of the resulting phosphogypsum cementitious material modifier is preferably 6-16 μm, more preferably 6-14 μm.

[0042] The present invention also provides a phosphogypsum cementitious material, the raw materials of which include phosphogypsum-slag cementitious material and phosphogypsum cementitious material modifier; the phosphogypsum cementitious material modifier is the phosphogypsum cementitious material modifier described in the above technical solution or the phosphogypsum cementitious material modifier prepared by the preparation method described in the above technical solution.

[0043] In this invention, the mass fraction of the phosphogypsum cementitious material modifier in the phosphogypsum cementitious material is preferably 5-20%, more preferably 10-15%. The phosphogypsum-slag cementitious material of this invention preferably comprises phosphogypsum, mineral powder, and silicate cement clinker; the mass ratio of the phosphogypsum, mineral powder, and silicate cement clinker is preferably 50-80:10-20:4-6, more preferably 75-80:15-20:5-6. This invention does not impose any particular limitation on the mixing method of phosphogypsum, mineral powder, and silicate cement clinker; any mixing method well known to those skilled in the art can be used.

[0044] The present invention also provides a phosphogypsum lightweight aggregate, which is obtained by sequentially subjecting phosphogypsum slurry to pelletizing and curing treatment; the raw materials for preparing the phosphogypsum slurry include phosphogypsum cementitious material and water, and the mass ratio of the phosphogypsum cementitious material to water is preferably 1:0.25 to 1:0.28, more preferably 1:0.27; the phosphogypsum cementitious material is the phosphogypsum cementitious material described in the above technical solution.

[0045] This invention involves spheroidizing the phosphogypsum slurry to obtain spherical aggregate. In this invention, the spheroidizing process is preferably a roller extrusion process. In an embodiment of this invention, the roller extrusion process includes the following steps: conveying the phosphogypsum slurry to smooth rollers for extrusion to obtain cake-shaped phosphogypsum aggregate; feeding the cake-shaped phosphogypsum aggregate into longitudinal grooved rollers for strip-shaped shaping to obtain strip-shaped phosphogypsum aggregate; feeding the strip-shaped phosphogypsum aggregate into transverse grooved rollers for block-shaped shaping to obtain cube-shaped phosphogypsum aggregate; and feeding the cube-shaped phosphogypsum aggregate into a spherical cavity for rolling to obtain spherical phosphogypsum aggregate. The roller spacing of the smooth rollers is 11.5–11.7 mm, the roller spacing and groove diameter of the longitudinal grooved rollers are both 11.2–11.4 mm, the roller spacing and groove diameter of the transverse grooved rollers are both 11–11.2 mm, and the diameter of the spherical phosphogypsum aggregate is 11 mm.

[0046] After obtaining spherical phosphogypsum aggregate, the present invention preferably performs a curing treatment on the spherical phosphogypsum aggregate to obtain lightweight phosphogypsum aggregate. In the present invention, the curing treatment preferably includes the following steps: mixing the spherical phosphogypsum aggregate with water for curing treatment to obtain lightweight phosphogypsum aggregate. In the present invention, the mass ratio of the phosphogypsum aggregate to water is preferably 1:1 to 3, more preferably 1:2; the curing temperature is preferably 27 to 29°C, and the curing time is preferably 28 to 60 days, more preferably 28 days. In the present invention, drying treatment is preferably performed after curing; the drying temperature is preferably 50 to 55°C, more preferably 50°C; the present invention does not have a special limitation on the drying time, and a drying time well known to those skilled in the art can be used.

[0047] This invention utilizes a phosphogypsum cementitious material modifier to prepare phosphogypsum cementitious materials and phosphogypsum lightweight aggregates, which can accelerate the setting and hardening process of phosphogypsum lightweight aggregates, significantly improve their early strength, and also have a certain enhancing effect on later strength; at the same time, by incorporating this modifier, the water absorption rate of phosphogypsum lightweight aggregates can be reduced and the softening coefficient can be increased.

[0048] The process of this invention is simple, low-cost, and easy to promote. This invention uses a phosphogypsum granulation process, which consumes phosphogypsum by-products and recycles production waste. The phosphogypsum cementitious material modifier prepared in this way can modify phosphogypsum slurry and phosphogypsum lightweight aggregate, improve the hydration degree of phosphogypsum slurry and phosphogypsum lightweight aggregate, optimize the hydration products of the two, and improve their mechanical properties.

[0049] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0050] In embodiments of the present invention, the specifications of the specific reagents are as follows:

[0051] The reagent is specifically:

[0052] Waste phosphogypsum aggregate (produced from the phosphogypsum aggregate production line of Hubei Changyao New Materials Co., Ltd.);

[0053] Metakaolin (particle size d(0.5) is 10.925μm, produced by Inner Mongolia Chaopai Kaolin Co., Ltd.);

[0054] Silica fume (particle size d(0.5) is 15.737μm, produced by Henan Borun Casting Materials Co., Ltd.);

[0055] Fly ash (particle size d(0.5) is 14.586μm, fineness is 800 mesh, total mass fraction of silicon oxide and aluminum oxide in fly ash is 79-83%, produced by Henan Borun Casting Materials Co., Ltd.);

[0056] Quicklime (800 mesh, produced by Hangzhou Taihe New Materials Co., Ltd.);

[0057] Protein-based gypsum retarder (specifically named KH-GR801 gypsum retarder, commercial model KH-GR801, produced by Wuhan Huaxuan High-Tech Co., Ltd.);

[0058] Phosphogypsum (particle size d(0.5) is 18.263μm, produced from Zhongfu Chemical Dongxiquan phosphogypsum slag yard);

[0059] Mineral powder (particle size d(0.5) is 9.659μm, produced by Lingshou County Dali Mineral Products Co., Ltd.);

[0060] Silicate cement clinker (particle size d(0.5) is 9.006μm, produced by Huaxin Cement Co., Ltd., P·O42.5).

[0061] Example 1

[0062] (1) Preparation of phosphogypsum cementitious material modifier

[0063] The waste supersulfurized phosphogypsum aggregate was dried at 50℃ for 24 hours, then physically crushed and ground to obtain supersulfurized phosphogypsum aggregate powder with a particle size of 0.1-0.15 mm. The supersulfurized phosphogypsum aggregate powder was then transferred to a dry reactor, and the reactor temperature was raised to 175℃ at a rate of 5℃ / min for calcination, held at that temperature for 3 hours, and then cooled to obtain the dehydrated phase of the supersulfurized phosphogypsum aggregate powder. The mass ratio of the dehydrated phosphogypsum phase, CSH gel phase, and aluminum phase in the obtained dehydrated phase was 67:18:15.

[0064] By weight, 50 parts of dehydrated phase of supersulfurized phosphogypsum aggregate waste powder, 20 parts of metakaolin, 10 parts of silica fume, 10 parts of fly ash, 10 parts of quicklime, and 0.01 parts of protein gypsum retarder are mixed and ground at 350 r / min for 2 min to obtain phosphogypsum cementitious material modifier.

[0065] (2) Preparation of phosphogypsum cementitious materials

[0066] Phosphogypsum, mineral powder, and silicate cement clinker are mixed in a mass ratio of 80:15:5 to obtain phosphogypsum-slag cementitious material; then, the phosphogypsum-slag cementitious material and the phosphogypsum cementitious material modifier obtained in step (1) are mixed in a mass ratio of 90:10 to obtain phosphogypsum cementitious material, that is, the mass fraction of the phosphogypsum cementitious material modifier in the phosphogypsum cementitious material is 10%.

[0067] (3) Preparation of phosphogypsum lightweight aggregate

[0068] Water and the phosphogypsum cementitious material obtained in step (2) are mixed at a mass ratio of 0.27:1 to obtain phosphogypsum slurry. The phosphogypsum slurry is then subjected to roller extrusion to obtain spherical phosphogypsum aggregate. The spherical phosphogypsum aggregate is then mixed with water at a mass ratio of 1:2 and cured at 28±1℃ for 28 days. After being removed, it is dried at 50℃ to obtain phosphogypsum lightweight aggregate.

[0069] Example 2

[0070] (1) Preparation of phosphogypsum cementitious material modifier

[0071] The waste supersulfurized phosphogypsum aggregate was dried at 50℃ for 24 hours, then physically crushed and ground to obtain supersulfurized phosphogypsum aggregate powder with a particle size of 0.1-0.15 mm. The supersulfurized phosphogypsum aggregate powder was then transferred to a dry reactor, and the reactor temperature was raised to 175℃ at a rate of 5℃ / min for calcination, held at that temperature for 3 hours, and then cooled to obtain the dehydrated phase of the supersulfurized phosphogypsum aggregate powder. The mass ratio of the dehydrated phosphogypsum phase, CSH gel phase, and aluminum phase in the obtained dehydrated phase was 67:18:15.

[0072] By mass fraction, 67 parts of dehydrated phase of supersulfurized phosphogypsum aggregate waste powder, 13.2 parts of metakaolin, 10 parts of silica fume, 6.6 parts of fly ash, 6.6 parts of quicklime, and 0.01 parts of protein-based gypsum retarder are mixed and ground at 350 r / min for 2 min to obtain phosphogypsum cementitious material modifier.

[0073] (2) Preparation of phosphogypsum gel material

[0074] Phosphogypsum, mineral powder, and silicate cement clinker are mixed in a mass ratio of 80:15:5 to obtain phosphogypsum-slag cementitious material; then, the phosphogypsum-slag cementitious material and the phosphogypsum cementitious material modifier obtained in step (1) are mixed in a mass ratio of 85:15 to obtain phosphogypsum cementitious material, that is, the mass fraction of the phosphogypsum cementitious material modifier in the phosphogypsum cementitious material is 15%.

[0075] (3) Preparation of phosphogypsum lightweight aggregate

[0076] Water and the phosphogypsum cementitious material obtained in step (2) are mixed at a mass ratio of 0.27:1 to obtain phosphogypsum slurry. The phosphogypsum slurry is then subjected to roller extrusion to obtain spherical phosphogypsum aggregate. The spherical phosphogypsum aggregate is then mixed with water at a mass ratio of 1:2 and cured at 28±1℃ for 28 days. After being removed, it is dried at 50℃ to obtain phosphogypsum lightweight aggregate.

[0077] Example 3

[0078] (1) Preparation of phosphogypsum cementitious material modifier

[0079] The waste supersulfurized phosphogypsum aggregate was dried at 50℃ for 24 hours, then physically crushed and ground to obtain supersulfurized phosphogypsum aggregate powder with a particle size of 0.1-0.15 mm. The supersulfurized phosphogypsum aggregate powder was then transferred to a dry reactor, and the reactor temperature was raised to 175℃ at a rate of 5℃ / min for calcination, held at that temperature for 48 hours, and then cooled to obtain the dehydrated phase of the supersulfurized phosphogypsum aggregate powder. The mass ratio of the dehydrated phosphogypsum phase, CSH gel phase, and aluminum phase in the obtained dehydrated phase was 67:18:15.

[0080] By mass fraction, 80 parts of dehydrated phase of supersulfurized phosphogypsum aggregate waste powder, 8 parts of metakaolin, 4 parts of silica fume, 4 parts of fly ash, 4 parts of quicklime, and 0.01 parts of protein gypsum retarder are mixed and ground at 350 r / min for 2 min to obtain phosphogypsum cementitious material modifier.

[0081] (2) Preparation of phosphogypsum cementitious materials

[0082] Phosphogypsum, mineral powder, and silicate cement clinker are mixed in a mass ratio of 80:15:5 to obtain phosphogypsum-slag cementitious material; then, the phosphogypsum-slag cementitious material and the phosphogypsum cementitious material modifier obtained in step (1) are mixed in a mass ratio of 80:20 to obtain phosphogypsum cementitious material, that is, the mass fraction of the phosphogypsum cementitious material modifier in the phosphogypsum cementitious material is 20%.

[0083] (3) Preparation of phosphogypsum lightweight aggregate

[0084] Water and the phosphogypsum cementitious material obtained in step (2) are mixed at a mass ratio of 0.27:1 to obtain phosphogypsum slurry. The phosphogypsum slurry is then subjected to roller extrusion to obtain spherical phosphogypsum aggregate. The spherical phosphogypsum aggregate is then mixed with water at a mass ratio of 1:2 and cured at 28±1℃ for 28 days. After being removed, it is dried at 50℃ to obtain phosphogypsum lightweight aggregate.

[0085] Example 4

[0086] (1) Preparation of phosphogypsum cementitious material modifier

[0087] The waste supersulfurized phosphogypsum aggregate was dried at 50℃ for 24 hours, then physically crushed and ground to obtain supersulfurized phosphogypsum aggregate powder with a particle size of 0.1-0.15 mm. The supersulfurized phosphogypsum aggregate powder was then transferred to a dry reactor, and the reactor temperature was raised to 175℃ at a rate of 5℃ / min for calcination, held at that temperature for 48 hours, and then cooled to obtain the dehydrated phase of the supersulfurized phosphogypsum aggregate powder. The mass ratio of the dehydrated phosphogypsum phase, CSH gel phase, and aluminum phase in the obtained dehydrated phase was 67:18:15.

[0088] By mass fraction, 58.5 parts of dehydrated phase of supersulfurized phosphogypsum aggregate waste powder, 17.6 parts of metakaolin, 5.9 parts of silica fume, 5.9 parts of fly ash, 11.8 parts of quicklime, and 0.01 parts of protein-based gypsum retarder are mixed and ground at 350 r / min for 2 min to obtain phosphogypsum cementitious material modifier.

[0089] (2) Preparation of phosphogypsum cementitious materials

[0090] Phosphogypsum, mineral powder, and silicate cement clinker are mixed in a mass ratio of 80:15:5 to obtain phosphogypsum-slag cementitious material; then, the phosphogypsum-slag cementitious material and the phosphogypsum cementitious material modifier obtained in step (1) are mixed in a mass ratio of 85:15 to obtain phosphogypsum cementitious material, that is, the mass fraction of the phosphogypsum cementitious material modifier in the phosphogypsum cementitious material is 15%.

[0091] (3) Preparation of phosphogypsum lightweight aggregate

[0092] Water and the phosphogypsum cementitious material obtained in step (2) are mixed at a mass ratio of 0.27:1 to obtain phosphogypsum slurry. The phosphogypsum slurry is then subjected to roller extrusion to obtain spherical phosphogypsum aggregate. The spherical phosphogypsum aggregate is then mixed with water at a mass ratio of 1:2 and cured at 28±1℃ for 28 days. After being removed, it is dried at 50℃ to obtain phosphogypsum lightweight aggregate.

[0093] Comparative Example 1

[0094] (1) Preparation of phosphogypsum-slag cementitious materials

[0095] Phosphogypsum, mineral powder, and silicate cement clinker are mixed in a mass ratio of 80:15:5 to obtain phosphogypsum-slag cementitious material.

[0096] (2) Preparation of phosphogypsum lightweight aggregate

[0097] The phosphogypsum-slag cementitious material obtained in step (1) is mixed with 0.27 parts of water to obtain phosphogypsum slurry; then the phosphogypsum slurry is subjected to roller extrusion to obtain spherical phosphogypsum aggregate; then the spherical phosphogypsum aggregate is immersed in water and cured at 28±1℃ for 28 days, and then dried at 50~55℃ to obtain phosphogypsum lightweight aggregate.

[0098] The composition of the phosphogypsum cementitious material modifier in Examples 1-4 and Comparative Example 1 is shown in Table 1.

[0099] Table 1. Proportioning of Modifier for Phosphogypsum Cementitious Materials

[0100]

[0101] The setting times of the phosphogypsum lightweight aggregates obtained in Examples 1-4 and Comparative Example 1 are as follows: Figure 1 As shown. By Figure 1 It is known that the addition of the phosphogypsum cementitious material modifier provided by the present invention can significantly shorten the initial and final setting time of the phosphogypsum cementitious material, with Example 3 showing the most significant effect.

[0102] The mechanical properties of the phosphogypsum lightweight aggregates obtained in Examples 1-4 and Comparative Example 1 are shown in Table 2 (the mechanical properties were tested according to the following literature: Physical properties, strength, and impurities stability of phosphogypsum-based cold-bonded aggregate).

[0103] Table 2 Mechanical properties of phosphogypsum lightweight aggregate

[0104]

[0105]

[0106] As shown in Table 2, the addition of the phosphogypsum cementitious material modifier provided by this invention can significantly improve the early single-particle strength of phosphogypsum lightweight aggregate, and also has a certain effect on increasing the later strength. A comparison of the mechanical properties of the phosphogypsum lightweight aggregates obtained in Examples 1-4 and Comparative Example 1 shows that the phosphogypsum lightweight aggregate obtained in Example 2 has the highest early single-particle strength and the lowest water absorption rate. Therefore, when the mass ratio of phosphogypsum-slag cementitious material to phosphogypsum cementitious material modifier is 85:15, the resulting phosphogypsum lightweight aggregate has the best mechanical properties. The proportion of the phosphogypsum cementitious material modifier is: 67 parts of dehydrated phase of supersulfurized phosphogypsum aggregate waste powder, 13.2 parts of metakaolin, 10 parts of silica fume, 6.6 parts of fly ash, 6.6 parts of quicklime, and 0.01 parts of protein-based gypsum retarder.

[0107] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A phosphogypsum cementitious material modifier, comprising, by weight parts, the following raw materials: The mixture comprises 50-100 parts of dehydrated phase of supersulfurized phosphogypsum aggregate waste powder, 0-10 parts of fly ash, 5-20 parts of metakaolin, 0-10 parts of silica fume, 4-12 parts of quicklime, and 0-0.01 parts of gypsum retarder; the dehydrated phase of supersulfurized phosphogypsum aggregate waste powder includes a phosphogypsum dehydrated phase, a CSH gel dehydrated phase, and an aluminum phase dehydrated phase; the mass ratio of the phosphogypsum dehydrated phase, CSH gel dehydrated phase, and aluminum phase dehydrated phase is 60-80:15-20:15-20.

2. The phosphogypsum cementitious material modifier according to claim 1, characterized in that, The method for preparing the dehydrated phase of the supersulfurized phosphogypsum aggregate waste powder includes the following steps: The waste phosphogypsum aggregate was ground to obtain waste phosphogypsum aggregate powder. The supersulfurized phosphogypsum aggregate waste powder is calcined to obtain the dehydrated phase of supersulfurized phosphogypsum aggregate waste powder.

3. The phosphogypsum cementitious material modifier according to claim 2, characterized in that, The particle size of the supersulfurized phosphogypsum aggregate waste powder is less than 0.15 mm; the calcination temperature is 100-200℃, the holding time is 2-4 h, and the rate of heating to the calcination temperature is 4-6℃ / min.

4. The phosphogypsum cementitious material modifier according to claim 1, characterized in that, The fly ash is grade I fly ash, the total mass fraction of silicon oxide and aluminum oxide in the fly ash is greater than 50%, and the fineness of the fly ash is 600-800 mesh.

5. The phosphogypsum cementitious material modifier according to claim 1, characterized in that, The gypsum retarder includes at least one of protein-based gypsum retarder, alkaline phosphate retarder, and organic acid and its soluble salt retarder.

6. A method for preparing the phosphogypsum cementitious material modifier according to any one of claims 1 to 5, comprising the following steps: The raw materials are mixed and ground to obtain a phosphogypsum cementitious material modifier.

7. A phosphogypsum cementitious material, the raw materials for preparation comprising phosphogypsum-slag cementitious material and a phosphogypsum cementitious material modifier; wherein the phosphogypsum cementitious material modifier is the phosphogypsum cementitious material modifier according to any one of claims 1 to 5 or the phosphogypsum cementitious material modifier prepared by the preparation method according to claim 6; wherein the mass fraction of the phosphogypsum cementitious material modifier in the phosphogypsum cementitious material is 5% to 20%.

8. The phosphogypsum cementitious material according to claim 7, characterized in that, The phosphogypsum-slag cementitious material includes phosphogypsum, mineral powder, and silicate cement clinker, and the mass ratio of the phosphogypsum, mineral powder, and silicate cement clinker is 50-80:10-20:4-6.

9. A phosphogypsum lightweight aggregate, obtained by sequentially subjecting phosphogypsum slurry to pelletizing and curing treatment; the raw materials for preparing the phosphogypsum slurry include phosphogypsum cementitious material and water, wherein the mass ratio of the phosphogypsum cementitious material to water is 1:0.25 to 1:0.28; wherein the phosphogypsum cementitious material is the phosphogypsum cementitious material as described in claim 7 or 8.

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