A sintered brick based on superabsorbent clay and a method for producing the same
By modifying highly absorbent clay with dodecylbenzene sulfonic acid and water glass and carbonizing it in a carbon-containing atmosphere, the problems of high plasticity index and high shrinkage rate of highly absorbent clay in sintered bricks were solved, realizing the efficient preparation of high-strength crack-free sintered bricks and reducing production energy consumption.
Patent Information
- Authority / Receiving Office
- CN Β· China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-17
- Publication Date
- 2026-06-16
AI Technical Summary
Existing technologies are difficult to effectively utilize highly absorbent clay to prepare sintered bricks, as they suffer from high plasticity index, severe shrinkage during drying leading to cracks, and high cost or unfavorable conditions for extrusion molding due to modification methods.
Highly absorbent clay was modified with dodecylbenzene sulfonic acid and water glass solution, and then carbonized in a carbon-containing atmosphere to form amorphous silica gel-coated clay particles, reducing the plasticity index and shrinkage rate. Sintered bricks were then prepared by vacuum extrusion molding and gradient sintering processes.
This approach enables the high-value-added resource utilization of highly absorbent clay, reduces the plasticity index and shrinkage rate, improves the compressive strength and appearance quality of sintered bricks, and reduces production energy consumption.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of building materials technology, specifically relating to a sintered brick based on highly absorbent clay and its preparation method. Background Technology
[0002] The main raw material for ordinary clay bricks is silty or sandy clay, whose main chemical components are SiO2, Al2O3, Fe2O3, and water of crystallization. In order to meet the requirements of clay brick extrusion molding, the plasticity index of the raw material should be controlled between 7 and 15, and its linear shrinkage rate during drying should be less than 6%.
[0003] A large amount of waste clay is generated during construction such as foundation excavation, road construction, and mining. Some of this waste clay contains minerals such as montmorillonite and illite, and has a high water absorption rate and a plasticity index that is much higher than that required for sintered bricks. In addition, the severe shrinkage after drying will produce a large number of shrinkage cracks, which seriously limits the use of waste clay for the preparation of sintered bricks.
[0004] Currently, there are two main methods for waterproofing modification of highly absorbent clay: 1) modification using organic materials, but this has problems such as high cost and irritating odor; 2) modification using traditional inorganic materials such as cement and lime, but this method is problematic because clay is prone to clumping, which is not conducive to extrusion molding, and the introduction of excessive calcium can also cause volume stability issues by forming free calcium oxide during calcination. Some studies have further pointed out the use of water glass to modify clay particles, but this method still has limited effect on improving highly absorbent clay. The main reason is that the sodium ions introduced into the water glass will undergo an ion exchange reaction with the clay particles, causing the clay particles to absorb more water and increase the interlayer spacing, resulting in significant volume expansion, which will still lead to severe shrinkage during the subsequent drying process. Summary of the Invention
[0005] The main objective of this invention is to address the problems and shortcomings of existing technologies by providing a sintered brick based on highly absorbent clay and its preparation process.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A sintered brick based on superabsorbent clay, the components and their weight fractions include: 85-90 parts of modified superabsorbent clay and 10-15 parts of water; the modified superabsorbent clay is obtained by sequentially modifying the superabsorbent clay with dodecylbenzene sulfonic acid and water glass solution, and then performing powder mixing and carbonization treatment in a carbon-containing atmosphere.
[0007] In the above scheme, the main mineral components and their mass percentages in the modified superabsorbent clay include: quartz 40-60%, feldspar 0-10%, kaolinite 0-15%, chlorite 0-15%, illite 10-20%, and montmorillonite 15-30%. Further, the plasticity index of the superabsorbent clay (initial clay) is 15-25, and the linear shrinkage rate is 10-20%.
[0008] Furthermore, the dodecylbenzenesulfonic acid modification is performed using a dodecylbenzenesulfonic acid solution with a concentration of 3-5 wt%.
[0009] In the above scheme, the mass ratio of the introduced superabsorbent clay to the dodecylbenzenesulfonic acid solution is 100:2~3.
[0010] In the above scheme, the water glass solution is obtained by diluting water glass with a modulus of 2.8 to 3.5, and its concentration is 5 to 10 wt%.
[0011] In the above scheme, the mass ratio of the superabsorbent clay to the water glass solution is 100:6~10.
[0012] Furthermore, the highly absorbent clay is dried, crushed, and screened before use to obtain fine highly absorbent clay material with a particle size of less than 3 mm.
[0013] In the above scheme, the mixing speed is 600~900 r / min and the time is 3~5 min.
[0014] In the above scheme, the environmental conditions for the carbonization and aging treatment in the carbon-containing atmosphere are: temperature 20~40β, relative humidity 80~95%; carbon-containing atmosphere temperature 20~50β, carbon dioxide concentration 20~100 vol%; and treatment time 1~2 days.
[0015] Furthermore, the preparation method of the modified superabsorbent clay includes the following steps: 1) Dry or bake the highly absorbent clay to control its moisture content at 2-5%; then crush and sieve it, and take the fine material from the sieve. 2) Add the dodecylbenzenesulfonic acid solution evenly to the obtained sieved fine material, stir evenly, and let stand to obtain the premix; 3) Add water glass solution evenly to the obtained premix, then perform high-speed powder mixing and crushing to obtain fine mixed material; 4) The obtained mixed fine material is aged (temperature 20~40β, relative humidity 80~95%), and carbon-containing gas is introduced at the same time (temperature 20~50β, carbon dioxide concentration 20~100 vol%). After aging (1~2 days), the modified superabsorbent clay is obtained, with a plasticity index of 10~15 and a linear shrinkage rate of 3~5%.
[0016] The present invention also provides a method for preparing the above-mentioned sintered brick based on highly absorbent clay, comprising the following steps: 1) Measure the modified water-absorbing clay and water according to the proportion, stir evenly (stir at a speed of 300~600r / min for 2~4min), and then roll and grind to obtain the premixed material; 2) The obtained premixed material is extruded (in a vacuum extruder) to obtain wet brick blanks; 3) Allow the obtained wet brick blanks to dry naturally (3-7 days) to obtain dry brick blanks; 4) Place the dry brick blanks in the kiln for gradient sintering, cool, and obtain the finished sintered bricks.
[0017] In the above scheme, the extrusion molding adopts a vacuum extrusion process, with a vacuum degree of -0.05 to -0.07 MPa and an extrusion molding pressure of 2 to 3 MPa.
[0018] In the above scheme, during the natural drying process, the ambient temperature is 30~40β and the relative humidity is 50~80%; the moisture content of the resulting dry brick blank is 0.5~2.5%.
[0019] In the above scheme, the gradient sintering process includes: first, heating to 100-120β at a rate of 0.5-0.8β / min, then heating to 420-450β at a rate of 0.8-1.2β / min, then heating to 650-750β at a rate of 0.5-0.8β / min, then heating to 900-950β at a rate of 0.8-1.2β / min, and holding at that temperature for 3-5 hours.
[0020] In the above scheme, the cooling step includes: cooling to room temperature at a rate of 1~1.5β / min.
[0021] The sintered bricks obtained according to the above scheme have a high compressive strength of over 20MPa, good appearance quality (no obvious cracks), no efflorescence, and a water absorption rate controlled at 8-12%.
[0022] The performance optimization mechanism of sintered bricks described in this invention includes: 1) Plasticity index modification: This invention targets highly absorbent clay. First, the clay is dried and crushed to obtain fine material. Then, a dodecylbenzenesulfonic acid solution is used for surface modification. The introduced dodecylbenzenesulfonic acid can uniformly adhere to the surface and pores of the clay particles. Furthermore, dodecylbenzenesulfonic acid has strong acidity and can significantly reduce surface tension, promoting the penetration of the water glass solution into the clay particles during subsequent water glass modification, and reacting to generate amorphous silica gel and sodium dodecylbenzenesulfonate. Because the surface of the clay particles and the micropores are coated with electrically neutral and non-hydrophilic silica gel, the double-layer structure and water film of the clay particles are effectively weakened, reducing the plasticity index of the clay. Simultaneously, the long carbon chain ends of sodium dodecylbenzenesulfonate are adsorbed on the clay surface, forming an organic hydrophobic film, further inhibiting the ion exchange reaction between sodium ions and clay particles, further reducing the plasticity index of the clay.
[0023] 2) Improved shrinkage: For highly absorbent clay, moisture penetrates the interlayer of clay particles, causing significant volume expansion, while moisture loss during drying leads to significant volume shrinkage. This invention employs a two-step modification method for highly absorbent clay. The first step utilizes the reaction between dodecylbenzenesulfonic acid and water glass. The resulting amorphous silica coats the surface of the clay particles, and sodium dodecylbenzenesulfonate effectively increases the oleophilic and hydrophobic properties of the clay particles, creating a composite structure: the outer layer is coated with silica, effectively inhibiting moisture penetration into the clay particle molecular layers, while the inner hydrophobic film further inhibits the diffusion of sodium ions and moisture inward, thus resolving the negative effects of sodium ions generated during water glass modification. The second step, the carbonization curing process, effectively increases the generation of silica (carbonized water glass). After these two steps of modification, the water consumption during molding is significantly reduced, and the shrinkage value also decreases. Furthermore, the high-hardness silica is less prone to deformation under shrinkage stress, further inhibiting shrinkage. The modified superabsorbent clay has a linear shrinkage rate reduced to 3-5%, effectively avoiding shrinkage cracks that occur during the drying process of wet brick blanks.
[0024] 3) The amorphous silica formed during the modification process of this invention has a lower melting point than clay minerals. Therefore, in the sintering process, the amorphous silica melts in advance to form a liquid phase. After the liquid phase is formed, capillary tension is generated, and internal gases are discharged, effectively increasing the density of the brick blank. This helps to further improve the strength of the obtained sintered brick and reduce the water absorption rate. In addition, the low-melting-point amorphous silica forms a low-melting-point eutectic with clay particles, which also helps to lower the sintering temperature (the traditional calcination temperature of clay is usually 950~1000β).
[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) After modification, the plasticity index of highly absorbent clay is reduced, and the moisture content during molding is reduced, which can shorten the drying time and improve production efficiency, realizing the high-value-added resource utilization of highly absorbent clay in sintered bricks.
[0026] 2) The sintered bricks obtained by this invention have high compressive strength, good appearance quality, and no efflorescence. The performance of the sintered bricks prepared by high water absorption clay is basically the same as that of sintered bricks prepared by conventional clay.
[0027] 3) Using modified superabsorbent clay can promote a reduction in sintering temperature and significantly reduce energy consumption during the production process. Detailed Implementation
[0028] The present invention will be further described in detail below with reference to embodiments, so as to facilitate a clearer understanding of the present invention, but these embodiments do not constitute a limitation on the present invention.
[0029] In the following examples and comparative examples, the superabsorbent clay used contains the following main mineral components and their mass percentages: quartz 47%, feldspar 6%, kaolinite 6%, chlorite 7%, illite 9%, and montmorillonite 21%; its plasticity index is 23, and its linear shrinkage rate is 16%. The water glass modulus used is 3.0, and it is diluted to a concentration of 6wt% before use.
[0030] The dodecylbenzene sulfonic acid used is a cleaning raw material from Chenqi Chemical and Daily Chemical, with an effective ingredient content of 92%.
[0031] The carbon-containing gas introduced into the aging chamber was at a temperature of 43Β°C and a carbon dioxide concentration of 25% (the remainder was mainly nitrogen and oxygen).
[0032] Example 1 A sintered brick based on highly absorbent clay, the preparation method of which includes the following steps: 1) Take 87 parts (by weight, the same below) of modified water-absorbing clay and 13 parts of water, stir at 450 r / min for 4 min, and then roll and grind to obtain premixed material; The preparation method of the modified superabsorbent clay includes the following steps: 1-1) Dry or bake the highly absorbent clay to control its moisture content at 3.5%; crush it and pass it through a 3mm sieve, then collect the fine material that passes through the sieve; 1-2) Dilute dodecylbenzenesulfonic acid with water to a concentration of 4wt% to obtain a dodecylbenzenesulfonic acid solution; Take 100 parts of the sieved fine material and stir it in a mixer at a speed of 90 r / min. Then, add 3 parts of the obtained dodecylbenzenesulfonic acid solution evenly within 3 min, continue stirring for 5 min, and let it stand for 2 h to obtain the premix. Continue stirring at 90 r / min, and uniformly add 8 parts of water glass solution to the obtained premix within 3 min, and continue stirring for 15 min to obtain the mixture; The resulting mixture is then crushed and mixed in a high-speed powder mixer to obtain fine mixed material. The powder mixer speed is 600 r / min and the time is 5 min. 1-3) The obtained mixed fine material was placed in an aging chamber for aging treatment at a temperature of 32β and a relative humidity of 85%. At the same time, carbon-containing gas (carbon-containing gas temperature 43β, carbon dioxide concentration 25 vol%) was introduced into the aging chamber. After aging for 2 days, modified superabsorbent clay was obtained with a plasticity index of 13 and a linear shrinkage rate of 4.1%.
[0033] 2) The obtained premixed material is extruded in a vacuum extruder to obtain wet brick blanks. The vacuum degree during molding is -0.05MPa and the extrusion molding pressure is 2.5MPa. 3) The obtained wet brick blanks were naturally dried for 5 days to obtain dry brick blanks; during the natural drying process, the ambient temperature was 32β and the relative humidity was 65%; the moisture content of the obtained dry brick blanks was 2.3%.
[0034] 4) Place the dry brick blanks in the kiln for gradient sintering; the specific sintering regime is as follows: first, raise the temperature to 120β at a rate of 0.6β / min, then raise the temperature to 450β at a rate of 1β / min, then raise the temperature to 700β at a rate of 0.6β / min, then raise the temperature to 900β at a rate of 1β / min, and hold the temperature for 4 hours; finally, cool the temperature to room temperature at a rate of 1.5β / min to obtain the finished sintered brick.
[0035] Example 2 A sintered brick based on superabsorbent clay is largely the same as in Example 1, except that the amount of water glass solution used in the preparation of the modified superabsorbent clay is adjusted to 10 parts; the plasticity index of the prepared modified superabsorbent clay is 11 and the linear shrinkage rate is 3.2%.
[0036] Example 3 A sintered brick based on superabsorbent clay is largely the same as in Example 1, except that the amount of dodecylbenzenesulfonic acid solution used in the preparation of the modified superabsorbent clay is adjusted to 2 parts. The plasticity index of the prepared modified superabsorbent clay is 14.3 and the linear shrinkage rate is 4.8%.
[0037] Comparative Example 1 A sintered brick based on superabsorbent clay is largely the same as in Example 1, except that the superabsorbent clay is used directly without modification.
[0038] Comparative Example 2 A sintered brick based on superabsorbent clay is largely the same as in Example 1, except that: no dodecylbenzene sulfonate is added during the modification of the superabsorbent clay; the prepared modified superabsorbent clay has a plasticity index of 17 and a linear shrinkage rate of 5.7%.
[0039] Comparative Example 3 A sintered brick based on superabsorbent clay is largely the same as in Example 1, except that in the preparation process of the modified superabsorbent clay, in steps 1-2), 100 parts of the sieved fine material are taken and stirred in a mixer at a speed of 90 r / min. Then, 3 parts of dodecylbenzenesulfonic acid solution and 15 parts of water glass solution are added evenly within 3 min, and the mixture is stirred for another 5 min and allowed to stand for 2 h to obtain a premix. The resulting mixture is then crushed and mixed in a high-speed powder mixer at a speed of 600 r / min for 5 min. The prepared modified superabsorbent clay has a plasticity index of 14.2 and a linear shrinkage rate of 5.3%.
[0040] Comparative Example 4 A sintered brick based on superabsorbent clay is largely the same as in Example 1, except that: no carbon-containing gas is introduced during the aging treatment of the modified superabsorbent clay; the prepared modified superabsorbent clay has a plasticity index of 14.5 and a linear shrinkage rate of 5.7%.
[0041] Comparative Example 5 A sintered brick based on superabsorbent clay is largely the same as in Example 1, except that in the preparation process of the modified superabsorbent clay, 3 parts of sodium dodecylbenzenesulfonate solution with a concentration of 4wt% are used to replace the dodecylbenzenesulfonic acid solution described in this invention; the prepared modified superabsorbent clay has a plasticity index of 20.1 and a linear shrinkage rate of 7.5%.
[0042] The sintered bricks obtained in Examples 1-3 and Comparative Examples 1-5 were subjected to performance tests according to standard GB / T5101-2017, and the results are shown in Table 1.
[0043] Table 1. Performance test results of sintered bricks
[0044] This invention is not limited to the embodiments described above. Those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.
Claims
1. A sintered brick based on highly absorbent clay, characterized in that, The components and their weight fractions include: 85-90 parts of modified superabsorbent clay and 10-15 parts of water; the modified superabsorbent clay is obtained by modifying the superabsorbent clay sequentially with dodecylbenzene sulfonic acid and water glass solution, followed by powder mixing and carbonization treatment in a carbon-containing atmosphere.
2. The sintered brick according to claim 1, characterized in that, The modified superabsorbent clay contains the following main mineral components and their mass percentages: quartz 40-60%, feldspar 0-10%, kaolinite 0-15%, chlorite 0-15%, illite 10-20%, and montmorillonite 15-30%.
3. The sintered brick according to claim 1, characterized in that, The plasticity index of the highly absorbent clay is 15-25, and the linear shrinkage rate is 10-20%.
4. The sintered brick according to claim 1, characterized in that, The modification step of dodecylbenzenesulfonic acid uses a dodecylbenzenesulfonic acid solution with a concentration of 3-5 wt%.
5. The sintered brick according to claim 1, characterized in that, The water glass solution is obtained by diluting water glass with a modulus of 2.8 to 3.5, and its concentration is 5 to 10 wt%.
6. The sintered brick according to claim 1, characterized in that, The environmental conditions for the carbonization and aging treatment in the carbon-containing atmosphere are: temperature 20~40β, relative humidity 80~95%; carbon-containing atmosphere temperature 20~50β, carbon dioxide concentration 20~100 vol%; treatment time 1~2 days.
7. The method for preparing sintered bricks based on highly absorbent clay according to any one of claims 1 to 6, characterized in that, Includes the following steps: 1) Measure the modified absorbent clay and water according to the proportion, mix them evenly, and then roll and grind them to obtain the premixed material; 2) The obtained premixed material is extruded to obtain wet brick blanks; 3) Allow the obtained wet brick blanks to dry naturally to obtain dry brick blanks; 4) Place the dry brick blanks in the kiln for gradient sintering, cool, and obtain the finished sintered bricks.
8. The preparation method according to claim 7, characterized in that, The moisture content of the resulting dry brick blanks is 0.5~2.5%.
9. The preparation method according to claim 7, characterized in that, The gradient sintering process includes: first, heating to 100-120β at a rate of 0.5-0.8β / min, then heating to 420-450β at a rate of 0.8-1.2β / min, then heating to 650-750β at a rate of 0.5-0.8β / min, and then heating to 900-950β at a rate of 0.8-1.2β / min, and holding at that temperature for 3-5 hours.
10. The preparation method according to claim 7, characterized in that, The cooling step includes cooling to room temperature at a rate of 1~1.5β / min.