Multi-source solid waste-based alkali-activated mortar and preparation method thereof

Abstract

This invention discloses a multi-source solid waste-based alkali-activated mortar and its preparation method, belonging to the field of building materials technology. The multi-source solid waste-based alkali-activated mortar comprises: binder, tailings, and deionized water, wherein the mass ratio of binder to tailings is 1:3, and the mass ratio of binder to deionized water is 1:2. The binder comprises the following raw materials by mass percentage: 20% carbide slag, 0-15% phosphogypsum, 0-15% industrial waste salt, and 65-75% blast furnace slag, wherein the addition of phosphogypsum and industrial waste salt is not simultaneously zero. The preparation method of the multi-source solid waste-based alkali-activated mortar is as follows: the raw materials are dry-mixed for 1 minute, then deionized water is added and mixing continues for 3 minutes to obtain a freshly mixed slurry. The slurry is poured into a mold and placed in a standard curing chamber. After curing for 24 hours, the mold is removed, and the specimen continues to be cured in the curing chamber for 7-28 days. The mortar material of this application has high strength and excellent structural density. This invention significantly reduces efflorescence by optimizing the activator composition.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a multi-source solid waste-based alkali-activated mortar and its preparation method. Background Technology

[0002] Alkali-activated cementitious materials are considered a potential alternative to traditional silicate cement due to their ability to utilize a large proportion of industrial solid waste, low carbon emissions, and excellent mechanical properties. However, the high alkalinity environment of these materials (usually using strong alkaline activators such as NaOH and Na₂SiO₃) easily triggers Na₂O₃ formation. + Ca 2+ isocations and CO3 2- The migration and crystallization of anions cause white crystalline precipitates (efflorescence) to form on the surface of structures. This phenomenon not only damages the appearance but also compromises the material's density, leading to pore expansion and strength deterioration, seriously jeopardizing the safety and durability of the project.

[0003] The alkali blooming behavior is mainly due to the fact that CO2 is easily converted into CO3 under strongly alkaline conditions. 2- The concentration of free active ions in high-concentration pore solutions is closely related to the loose gel framework formed by traditional strong base activation, which provides favorable conditions for ion surface crystallization. Existing suppression strategies mainly include: replacing sodium-based activators with potassium-based, calcium-based, or silica-alumina salts (taking advantage of the low crystal solubility of elements such as potassium and calcium), and reducing the concentration and amount of activator to reduce the content of free ions.

[0004] Based on the concept of low carbon and weak alkali activation, the synergistic utilization of multi-source solid waste can reduce the amount of high-concentration chemical alkali used while regulating the ion composition and hydration process of the system. This is expected to weaken the alkali blooming behavior and improve the material performance, providing a new technical path for the development of environmentally friendly alkali-activated materials. However, how to select and proportion the types of solid waste is a key technical challenge. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a multi-source solid waste-based alkali-activated mortar and its preparation method. By using industrial solid wastes such as carbide slag, phosphogypsum, and waste salt as raw materials and adjusting the composition of the alkali activator, the efflorescence phenomenon is significantly reduced. In particular, by using phosphogypsum as an alkali activator, a dense AFt and C–S–H gel structure is generated, which effectively inhibits the precipitation of surface salts.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a multi-source solid waste-based alkali-activated mortar, comprising the following components: binder, tailings and deionized water.

[0007] Furthermore, the mass ratio of the adhesive, tailings, and deionized water is 1:3:2.

[0008] Furthermore, the tailings are iron tailings.

[0009] Furthermore, the binder is composed of 20% carbide slag, 0-15% phosphogypsum, 0-15% industrial waste salt and 65-75% blast furnace slag, wherein the amount of phosphogypsum and industrial waste salt added is not both 0.

[0010] Furthermore, the binder is composed of 20% carbide slag, 5-15% phosphogypsum, and 65-75% blast furnace slag.

[0011] This invention also provides a method for preparing alkali-activated mortar based on multi-source solid waste, comprising the following steps: mixing the binder and tailings evenly, adding deionized water, stirring evenly to obtain fresh slurry, pouring the slurry into a mold and placing it in a standard curing room for curing for 24 hours before demolding, and continuing to cure for 7~28 days to obtain alkali-activated mortar specimens based on multi-source solid waste.

[0012] Furthermore, the composition of the carbide slag includes, by mass percentage: 95.19% CaO, 2.64% SiO2, 0.92% Al2O3, 0.59% Fe2O3, 0.39% MgO, 0.04% SrO, 0.04% P2O5, 0.03% Na2O, and 0.03% MnO.

[0013] Furthermore, the composition of the phosphogypsum includes, by mass percentage, 34.55% CaO, 2.09% SiO2, 0.47% Fe2O3, 2.09% MgO, 0.02% P2O5 and 38.67% SO3.

[0014] Furthermore, the temperature of the standard curing room is 20 ± 1℃ and the relative humidity is 95 ± 1%.

[0015] Furthermore, the mixing time of the adhesive and tailings is 1 minute, and the time for adding deionized water and stirring evenly is 3 minutes.

[0016] Compared with the prior art, the present invention has at least the following advantages and technical effects: This invention uses calcium-rich phosphogypsum as the main component of the alkali activator, which results in the formation of a densely interwoven network of ettringite and hydrated calcium aluminosilicate, with a refined pore structure, significantly inhibiting salt migration to the surface and markedly weakening the degree of alkali bloom.

[0017] The present invention provides a method for preparing alkali-activated mortar that enables high-proportion co-utilization of industrial solid waste, eliminates the need for high-temperature calcination, and is compatible with existing production lines, providing a feasible path for low-carbon, low-efficiency, and high-performance cementitious materials. Attached Figure Description

[0018] 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.

[0019] Figure 1 The efflorescence evolution process of multi-source solid waste-based mortars in Examples 1, 3, 4, and 6; Figure 2 The results of surface efflorescence binarization of multi-source solid waste-based mortars in Examples 1, 3, 4, and 6 at different ages are shown. Figure 3 The results of quantitative analysis of efflorescence in mortar specimens are shown. a represents the CG-P group; b represents the CG-G group. Figure 4 The results show the leaching of Na and Ca in the mortar specimens during the efflorescence process. a represents Na; b represents Ca. Figure 5 The XRD patterns of the surface region of the efflorescence specimen are shown in Figure 1; a represents the CG-P group; b represents the CG-G group. Figure 6 The results of TG and DTG curves for efflorescence specimens are shown, where a represents mass loss and b represents the DTG curve. Figure 7 The images show the FTIR spectra of the efflorescence test specimens. a represents the CG-P group; b represents the CG-G group. Figure 8 SEM images and EDS spectra of efflorescence specimens are shown. a~c represent the CG-P group; b~f represent the CG-G group. Figure 9 For the pore structure analysis of the alkali bloom specimen, a is the N2 adsorption isotherm; b is the pore size distribution. Figure 10 This is a schematic diagram of the alkali weakening mechanism of the multi-source solid waste-based cementitious material of the present invention. Detailed Implementation

[0020] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0021] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0022] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0023] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0024] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0025] This invention provides a multi-source solid waste-based alkali-activated mortar, comprising the following components: binder, tailings, and deionized water.

[0026] In some embodiments of the present invention, the mass ratio of the adhesive to tailings is 1:3, and the mass ratio of the adhesive to deionized water is 1:2.

[0027] In some embodiments of the present invention, the tailings are iron tailings.

[0028] In some embodiments of the present invention, the adhesive is composed of 20% carbide slag, 0-15% phosphogypsum, 0-15% industrial waste salt and 65-75% blast furnace slag, wherein the amounts of phosphogypsum and industrial waste salt added are not both 0.

[0029] In some embodiments of the present invention, the binder is composed of 20% carbide slag, 5-15% phosphogypsum and 65-75% blast furnace slag.

[0030] This invention also provides a method for preparing alkali-activated mortar based on multi-source solid waste, comprising the following steps: mixing the binder and tailings evenly, adding deionized water, stirring evenly to obtain a fresh slurry, pouring the slurry into a mold and placing it in a standard curing room for 24 hours before demolding, and continuing to cure for 7~28 days to obtain a multi-source solid waste-based alkali-activated mortar specimen.

[0031] In some embodiments of the present invention, the composition of the carbide slag includes, by mass percentage: 95.19% CaO, 2.64% SiO2, 0.92% Al2O3, 0.59% Fe2O3, 0.39% MgO, 0.04% SrO, 0.04% P2O5, 0.03% Na2O and 0.03% MnO.

[0032] In some embodiments of the present invention, the phosphogypsum comprises, by mass percentage, 34.55% CaO, 2.09% SiO2, 0.47% Fe2O3, 2.09% MgO, 0.02% P2O5 and 38.67% SO3.

[0033] In some embodiments of the present invention, the temperature of the standard curing room is 20 ± 1°C and the relative humidity is 95 ± 1%.

[0034] In some embodiments of the present invention, the mixing time of the adhesive and tailings is 1 minute, and the time for adding deionized water and stirring evenly is 3 minutes.

[0035] The technical solution of the present invention will be described in detail below through specific embodiments.

[0036] Unless otherwise specified, the raw materials used in the embodiments of this invention are all obtained through conventional purchasing channels. The technical specifications of the industrial solid waste are shown in Table 1.

[0037] Table 1 Chemical Analysis of Raw Materials Example 1 A multi-source solid waste-based alkali-activated mortar has the following raw material components: binder, iron tailings and deionized water, wherein the mass ratio of binder to tailings is 1:3, the mass ratio of binder to deionized water is 1:2, and the binder is composed of 20% carbide slag, 5% phosphogypsum and 75% blast furnace slag.

[0038] The specific steps for preparing the mortar are as follows: Dry mix the raw materials for 1 minute, then add deionized water and continue mixing for 3 minutes to obtain a freshly mixed mortar. Pour the mortar into a 40mm × 40mm × 40mm mold and place it in a standard curing chamber (temperature 20 ± 1℃, relative humidity 95 ± 1%). After curing for 24 hours, demold the specimen, and then continue curing in the curing chamber until the specified age. This yields mortar specimen CG-P5.

[0039] Example 2 A multi-source solid waste-based alkali-activated mortar is prepared in the same way as in Example 1, except that the binder is composed of 20% carbide slag, 10% phosphogypsum and 70% blast furnace slag, resulting in mortar specimen CG-P10.

[0040] Example 3 A multi-source solid waste-based alkali-activated mortar is prepared in the same way as in Example 1, except that the binder is composed of 20% carbide slag, 15% phosphogypsum and 65% blast furnace slag, resulting in mortar specimen CG-P15.

[0041] Example 4 A multi-source solid waste-based alkali-activated mortar is prepared using the same method as in Example 1, except that the binder consists of 20% carbide slag, 5% industrial waste salt, and 75% blast furnace slag, resulting in mortar specimen CG-G5.

[0042] Example 5 A multi-source solid waste-based alkali-activated mortar is prepared in the same way as in Example 1, except that the binder is composed of 20% carbide slag, 10% industrial waste salt and 70% blast furnace slag, to obtain mortar specimen CG-G10.

[0043] Example 6 A multi-source solid waste-based alkali-activated mortar is prepared in the same way as in Example 1, except that the binder is composed of 20% carbide slag, 15% industrial waste salt and 65% blast furnace slag, to obtain mortar specimen CG-G15.

[0044] The efflorescence evolution process of mortar specimens in Examples 1, 3, 4, and 6 during indoor curing from 0 to 28 days is as follows: Figure 1 As shown, by Figure 1 It can be seen that the surfaces of all four groups of samples were relatively dense and smooth at 0 days, without obvious efflorescence. As the curing time progressed, a white frost layer gradually appeared on the surface of the specimens, from light to dark, indicating that soluble salts in the system crystallized and precipitated onto the surface. Specifically, at 7 days, a more obvious crystalline layer could be observed on the surface of some samples, which was particularly prominent in the systems with high amounts of phosphogypsum or waste salt.

[0045] Comparison of different dosage groups revealed that the efflorescence rate of the low solid waste content system was slower, and the surface crystallization was relatively uniform. In contrast, the high dosage sample showed obvious whitening and even slight cracking on the surface in the early stages, indicating that the increase in soluble components exacerbated the crystallization. After 28 days, the surface crystallization of all groups of samples tended to stabilize, and the efflorescence range did not expand significantly. However, the high dosage group still had a thicker and more uneven crystalline layer.

[0046] The surface efflorescence binarization analysis and threshold results of multi-source solid waste-based mortar specimens at different ages in Examples 1, 3, 4, and 6 are as follows: Figure 2 As shown, the binarization results of the initial specimens reveal a certain number of white areas in each group of specimens in the early stages, reflecting the distribution characteristics of surface porosity and efflorescence. It is noteworthy that localized white patches can still be observed on the surface of the initial specimens, primarily due to porosity. The number of white areas significantly increases in the binarized image of the 28-day specimens, indicating that surface crystal precipitation requires time to occur, consistent with the efflorescence evolution pattern. The degree of efflorescence increases with age, but the AS- specimen at the same dosage exhibits worse efflorescence than the PG- specimen, attributed to the difference in salt composition between the two solid wastes.

[0047] Quantitative analysis results of efflorescence in mortar specimens are as follows: Figure 3 As shown, with increasing age, the proportion of efflorescence area in both groups of specimens increased, reaching a high level at 28 days. From the results of the CG-P group ( Figure 3 As shown in a), the efflorescence area increases with increasing PG content. At 0 days, the efflorescence area of ​​all groups is extremely low, but it increases significantly after 7 days, especially in the CG-P15 group, which reaches 80.72%, indicating that high PG content accelerates the crystallization and precipitation of calcite. After 14 days, the growth rate of all groups slows down, with the CG-P15 group reaching nearly 93% efflorescence area at 28 days, significantly higher than the CG-P5 and CG-P10 groups. This suggests that the high content of soluble sulfates in PG easily forms a frost layer on the specimen surface under moisture-driven conditions.

[0048] For the AS system ( Figure 3 In sample b), the efflorescence area was generally higher than that of the PG system, and increased rapidly from 3 to 7 days, exhibiting stronger crystallization ability. The efflorescence area of ​​sample CG-G15 reached 88.56% at 7 days, while that of CG-G5 was only 74.96%, indicating that high levels of waste salt significantly promoted calcite crystallization, similar to the trend observed in the PG system. After 14 days, the efflorescence area of ​​the CG-G group samples tended to saturate, and stabilized basically by 28 days. Among them, the CG-G15 group had the highest efflorescence area, reaching 98.5%, with its surface almost completely covered by crystals. Comparing the results of the two groups of samples, it can be seen that efflorescence occurred faster and to a greater extent in the AS system, while the efflorescence development in the PG system was relatively slower but lasted longer.

[0049] Figure 4 The figure shows the leaching results of Na and Ca in mortar specimens during the efflorescence process. As can be seen from the figure, Na... + With Ca 2+ The leaching concentrations all increased with increasing aging period.

[0050] Depend on Figure 4 From a, we can see that Na in the PG system + The overall concentration was low, remaining below 100 mg / L at both 7 and 28 days, indicating that the Na+ concentration in the CG-P group was low. + Given the limited source, it is inferred that the precipitation of its crystals is mainly due to Ca. 2+ Control. The Na+ concentration in the AS system increased significantly and was positively correlated with the doping amount. Na+ concentration in the CG-G15 sample after 7 days... + The concentration was close to 1000 mg / L, and further increased to approximately 1500 mg / L at 28 days, significantly higher than CG-G5 and CG-G10. This indicates that the incorporation of AS increased the sodium salt content in the system, providing cations for alkali blooming behavior. Simultaneously, maintaining interlayer charge balance in the high-doped AS system requires the consumption of more Na. + This leads to the free Na in the pore solution + The concentration is low.

[0051] Ca 2+ The pattern of concentration change is as follows Figure 4 As shown in b. Ca in the PG system 2+ The concentrations were generally higher than those in the AS system, and showed an increasing trend with increasing doping concentration. At 7 days, the Ca concentration in the CG-P15 sample... 2+ The concentration was 2480 mg / L, indicating that the elemental leaching concentration mainly depends on the initial content of the element in the feed system. In contrast, the Ca in the AS system... 2+ The concentrations were all below 1700 mg / L, mainly attributed to their high sodium and low calcium composition. This result further indicates that sodium plays a dominant role in efflorescence behavior within multi-source solid waste systems, consistent with efflorescence test results.

[0052] Figure 5 The XRD diffraction patterns of the surface region of the efflorescence specimens are presented. The main crystalline phases of both groups of samples included ettringite (AFt), gypsum, calcium hydroxide (CH), and calcite, while C–S–H gel was also detected. The multi-source solid waste-based mortar generates various carbonate components during the efflorescence process, indicating the presence of CO3. 2-The precipitation of ferrous sulfate plays a crucial role in alkali blooming behavior. Increased PG doping enhanced the intensity of the AFt diffraction peak, attributed to gypsum promoting AFt formation. The high PG doping specimen showed an increased C–S–H peak intensity at 29.3°, further confirming that active ions in the PG system primarily participate in hydration reactions, making them less likely to induce salt nucleation and aggregation. This result is corroborated by the approximate intensities of the calcite peak in CG-P5 and CG-P15 samples. The relatively weakened AFt and C–S–H peak intensities in the AS system indicate that the hydration reaction is interfered with by salt precipitation, limiting the densification of the gel structure. Therefore, it can be inferred that ions in this system are more inclined to participate in crystallization reactions, reducing hydration products within the matrix and hindering the construction of a stable framework structure.

[0053] Figure 6 The results of TG-DTG analysis of the efflorescence specimens are shown. The DTG curves reveal that the first weight loss peak appears in the 50–200℃ range, corresponding to the dehydration process of C–S–H gel and AFt; another peak, originating from the decomposition of monosulfoaluminate (AFm), is located at 200–300℃. The CG-P15 sample exhibits the highest peak values ​​in both stages, indicating that PG promotes the formation of gel products and that the secondary hydration of AFt in this system is more complete. A decomposition peak of CH is observed at 400–500℃, while the peak at 600–800℃ corresponds to the decomposition of calcite. Notably, the CH peak is weakened in specimens rich in PG and AS, mainly due to the consumption of Ca during hydration and efflorescence. 2+ and OH - AFt or calcite was formed. Furthermore, the calcite decomposition peak intensity in the CG-G group was significantly higher than in other specimens, indicating that its matrix contained a large amount of CaCO3 crystals, reflecting that the AS system is more prone to alkali blooming, which is consistent with the XRD results.

[0054] For the TG curves, the overall trends of the four samples were consistent. However, the high-doped PG and AS specimens showed higher total mass losses, which corresponded to the changes in peak intensity of the products in the DTG curves. Interestingly, the cementing products such as AFt and C–S–H showed a complementary relationship with the formation of calcite, further revealing an ion competition mechanism between the cementing reaction and the efflorescence behavior. This mechanism indicates that the efflorescence process weakens the cementing properties of the matrix, a finding verified by mechanical property tests.

[0055] Figure 7 The FTIR spectra of the efflorescence specimen are presented. The figure shows the 1625 cm⁻¹. -1 The absorption peak at 1420 cm⁻¹ indicates the symmetrical bending vibration of H–O–H, mainly caused by the formation of C–S–H gel and bound water in AFt; -1 and 875cm -1 The peaks at these locations correspond to CO3.2- The asymmetric stretching vibrations and out-of-plane bending vibrations of C–O in the CG-G15 specimen are related to calcite formation. The peak intensities at these two locations are slightly enhanced, indicating that Na+ in the AS may promote the precipitation of sodium salt crystals, consistent with the leaching test results. (1112 cm⁻¹) -1 The peak at this point represents the Si–O–T (T=Si or Al) stretching vibration, reflecting the formation of C–S–H gel. The strength of the CG-G group specimens at this peak is slightly lower than that of the CG-P group, indicating that the hydrates in the AS system have been subjected to alkali erosion. 778 cm⁻¹ -1 The peak originates from the symmetric stretching vibration of Al–O or Si–O, while the 458 cm⁻¹ peak... -1 The peaks, attributed to in-plane bending vibrations of Si–O–Si, all confirm the existence of a silica-alumina cementitious framework structure. The higher intensity of the CG-P group at the Si-Al characteristic peak indicates that high PG doping is beneficial to the formation of the silica-alumina phase and sulfates; 694 cm⁻¹ -1 The peak at that location corresponds to SO4. 2- The stretching vibrations are related to the gypsum and AFt in the system. The Ca in the PG system... 2+ With SO4 2- It promotes the formation of the sulfate phase and improves the matrix bonding performance, while the Na in the AS system + More active, it weakens gelation chemical bonds and limits the formation of hydration products.

[0056] Figure 8 SEM images and EDS analysis results of the alkali efflorescence specimens are presented. The morphology images show that the main products of both types of specimens consist of C–S–H gel, AFt, and calcite, but there are differences in crystal morphology and phase distribution. Specifically, the PG system ( Figure 8 On surfaces a and b), a dense structure formed by interwoven needle-like AFt and flocculent C–S–H gel was observed; corresponding EDS at point P1 ( Figure 8 c) shows that the main active elements are Ca, Si, Al, and S, supporting the conclusion that AFt and C–S–H gels coexist in a complex form, but Figure 8 This phenomenon was not observed in samples d and e. Notably, a three-dimensional network structure of C–S–H / hydrated sodium silicate gel (N–S–H) appeared in the CG-G group specimens, with the Na peak at point P2 showing an increase in intensity while the Ca peak weakened. Simultaneously, at point P2 ( Figure 8 The Si and Al peak intensities in f) are also lower than those in point P1, indicating that the crystal strength and bonding force of the gel products in the AS system are relatively weak, which is consistent with the characterization results of the reaction products.

[0057] Figure 9The changes in pore structure of multi-source solid waste-based mortar after efflorescence are shown. The N2 adsorption isotherms of all samples exhibit a significant hysteresis loop when the relative pressure P / P0 is close to 1, indicating that the matrix interior is dominated by pores in the range of 2–70 nm. Figure 9 As shown in Figure a, when P / P0 is below 0.8, the isotherm rises slowly, indicating that the initial adsorption stage is mainly limited by the preferential occupation of sample pores; as P / P0 further increases, the adsorption amount increases significantly, which is attributed to the gradual filling process of nitrogen gas by capillary condensation and larger pores.

[0058] The pore size distribution results of the alkali bloom specimen are as follows: Figure 9 As shown in Figure b, only the pore size distribution of the CG-P15 specimen is concentrated in the micropore size (0~10nm) and small pore size (10~50nm) range, indicating that the large amount of AFt and C-S-H gel generated in the PG system effectively fills the pores and inhibits the formation of interconnected throats. The pore size of the CG-G group is mainly distributed in the 10~100nm range, proving that the number of pores and connectivity in the AS system are relatively high, allowing salts to precipitate on the surface during the alkali bloom process. This characteristic corresponds to the structure of the reaction products in the microscopic analysis. Further comparison revealed that increasing the AS doping amount reduced the large pore size (50~100nm) while increasing the distribution of small pores. This is due to Na + Increased concentration promotes the formation of N–S–H gels, reduces the porosity of the gel skeleton, and ultimately inhibits Ca2+ formation. 2+ and Na + Migration and crystallization.

[0059] The multi-source solid waste-based alkali-activated cementitious material prepared with two types of solid waste activators (PG and AS) showed only a thin frost layer on the surface of the specimens after 28 days. Compared with the "frost" phenomenon in traditional alkali-activated materials, the degree of alkali efflorescence in this system was significantly reduced. Combining macroscopic, microscopic, and chemical analysis results, the efflorescence process can be deduced. The schematic diagram of the efflorescence weakening mechanism of the multi-source solid waste-based cementitious material is shown below. Figure 10 As shown. The activators used in the CG-P and CG-G groups are both solids. Upon contact with water, they do not immediately form gelling products, but rather dissolve in water first, and then undergo a hydration reaction under the alkaline environment provided by the CCR. The reaction equation is as follows: PG has a retarding effect; it can adsorb onto the surface of active ions in the early stages of the reaction, prolonging the reaction time and allowing for a more uniform distribution and sufficient contact of various ions in the solution. Therefore, the solid activator does not produce rapid solidification like traditional chemical agents (such as NaOH solution), avoiding the heterogeneity of the pore structure and thus reducing the pore channels for frost crystallization.

[0060] At the gelling system level, due to the different alkali activator components and varying proportions of active ions in the two types of materials, their reaction mechanisms should be discussed separately. For the PG system, CCR and PG provide a large amount of Ca. 2+ and SO4 2- These ions react with the SiO4 released by the dissolution of GGBS. 4- and AlO4 5- Polymerization occurs, producing AFt and C–S–H gel. The reaction equation is as follows: Microscopic analysis shows that this type of gel skeleton has a dense structure and small pore size distribution, which is beneficial for suppressing Ca2+. 2+ The leaching of sodium weakens the alkali bloom effect. In contrast, the AS and CCR systems in the AS system contain more Na. + and Ca 2+ When reacting with active silica-alumina phase, in addition to forming C–S–H gel, N–S–H gel is also generated. The reaction equation for N–S–H gel is as follows: It should be noted that the N–S–H gel has a loose three-dimensional network structure, unlike the dense AFt / C–S–H backbone, and is more likely to promote Na+ absorption. + Ca 2+ The migration and crystallization of [substances]. This also explains why the alkali-inhibiting effect of the AS system is weaker than that of the PG system.

[0061] Besides the influence of the structure of the gelling products on the efflorescence behavior, the crystallization reaction in the efflorescence process also plays an important role. During the efflorescence process, moisture continuously evaporates from the bottom of the specimen and enters the matrix, forming a porous solution that promotes Ca efflorescence. 2+ The migration of CO2 in the air; under alkaline conditions, the pore solution accelerates the dissolution of CO2 in the air, generating CO3. 2- With Ca 2+ The reaction produces calcite precipitate, and the reaction equation is as follows: On the other hand, AS provides a large amount of Na + With CO3 2- The reaction forms sodium carbonate, which combines with water under the influence of an alkaline solution, precipitating as hydrated sodium carbonate crystals (Na₂CO₃·nH₂O). The reaction equation is as follows: Therefore, the surface precipitates in the AS system are mainly composed of both calcium and sodium salts, while those in the PG system are primarily calcite-based precipitates. Characterization results also show that the types and quantities of crystal precipitation differ between the two systems, a difference that reasonably explains the more pronounced efflorescence phenomenon in the AS system compared to the PG system.

[0062] In summary, based on Figure 1-9 The data leads to the conclusion that the efflorescence behavior of cementitious materials using solid waste as an activator is mainly controlled by the type and quantity of ions. In the PG system, Ca... 2+ High concentration, Na + At low concentrations, crystallization is predominantly calcite, forming a dense AFt and C–S–H gel structure, which inhibits surface salt precipitation; in the AS system, Na… + The increased concentration and reaction to form Na2CO3·nH2O crystals, with rapid crystallization and high degree of alkali blooming, are key factors causing strong alkali blooming.

[0063] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A multi-source solid waste-based alkali-activated mortar, characterized in that, It includes the following components: binder, tailings and deionized water, wherein the binder components include carbide slag, blast furnace slag, phosphogypsum or industrial waste salt.

2. The multi-source solid waste-based alkali-activated mortar according to claim 1, characterized in that, The mass ratio of the adhesive, tailings, and deionized water is 1:3:

2.

3. The multi-source solid waste-based alkali-activated mortar according to claim 1, characterized in that, The tailings are iron tailings.

4. The multi-source solid waste-based alkali-activated mortar according to claim 1, characterized in that, The binder is composed of 20% carbide slag, 0-15% phosphogypsum, 0-15% industrial waste salt and 65-75% blast furnace slag, wherein the amount of phosphogypsum and industrial waste salt added is not both 0.

5. The multi-source solid waste-based alkali-activated mortar according to claim 4, characterized in that, The binder consists of 20% carbide slag, 5-15% phosphogypsum, and 65-75% blast furnace slag.

6. The multi-source solid waste-based alkali-activated mortar according to claim 4, characterized in that, The composition of the carbide slag, by mass percentage, includes: 95.19% CaO, 2.64% SiO2, 0.92% Al2O3, 0.59% Fe2O3, 0.39% MgO, 0.04% SrO, 0.04% P2O5, 0.03% Na2O and 0.03% MnO.

7. The multi-source solid waste-based alkali-activated mortar according to claim 4, characterized in that, The phosphogypsum comprises, by mass percentage: 34.55% CaO, 2.09% SiO2, 0.47% Fe2O3, 2.09% MgO, 0.02% P2O5 and 38.67% SO3.

8. A method for preparing multi-source solid waste-based alkali-activated mortar as described in claim 1, characterized in that, The process includes the following steps: mixing the adhesive and tailings evenly, adding deionized water, stirring evenly to obtain a fresh slurry, pouring the slurry into a mold and placing it in a standard curing room for 24 hours before demolding, and continuing to cure for 7~28 days to obtain a multi-source solid waste-based alkali-activated mortar specimen.

9. The method for preparing multi-source solid waste-based alkali-activated mortar according to claim 8, characterized in that, The temperature of the standard curing room is 20±1℃ and the relative humidity is 95±1%.

10. The method for preparing multi-source solid waste-based alkali-activated mortar according to claim 8, characterized in that, The mixing time for the adhesive and tailings is 1 minute, and the time for stirring evenly after adding deionized water is 3 minutes.

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