Red mud-building solid waste low-strength composite foundation reinforcing pile suitable for acid soil and construction method

Abstract

The invention discloses a red mud-building solid waste low-strength composite foundation reinforcing pile suitable for acid soil and a construction method, red mud and recycled micro powder are used as cementing materials, recycled aggregate is used as filling aggregate, an alkali activator is added to excite potential cementing activity of the red mud and the recycled micro powder, and the pH value change is monitored, so that the red mud-building solid waste low-strength composite foundation reinforcing pile is obtained. A proper amount of cement is matched to form composite foundation reinforcing piles; the method comprises the steps of mixing ratio testing, pile forming construction, pile body material filling, natural curing and detection, wherein when the pile body material is filled, the pH value is monitored in real time through a pH value sensor, and the use amount of an alkali activator is regulated and controlled to keep alkalinity; building solid waste and industrial solid waste red mud are combined, the low-strength composite foundation reinforcement pile is prepared through an alkali excitation means, corrosion of acid soil to a pile body is resisted through the alkalinity of the red mud and an alkali activator, the performance meets the national standard requirement, the potential gelling activity of the red mud is excited while the building solid waste is recycled, and the construction period is shortened. And natural resource consumption in the building industry is reduced, and pollutant emission is reduced.

Description

Technical Field

[0001] The invention belongs to the field of foundation treatment, and in particular relates to a red mud-construction solid waste low-strength composite foundation reinforcement pile suitable for acidic soil and a construction method. Background Art

[0002] Acidic soil is widely distributed in my country. The causes of its formation include natural factors such as mineral oxidation and reduction, life metabolism of microorganisms and plant roots, as well as acid rain and soil acid deposition caused by industrial pollution. The pH value of local strong acidic soil layers is less than 4. Since concrete materials are usually weakly alkaline or alkaline, they are sensitive to their acidic environment. When concrete piles are in acidic soil or acidic groundwater environment, they are very easy to react with the acid in the environment and suffer corrosion, reducing their strength.

[0003] Red mud is the waste residue produced during the production of alumina. It is red because it contains a large amount of iron oxide, so it is called red mud. Due to the difference in ore grade, production method and technical level, most production plants produce 1 to 2 tons of red mud for every ton of alumina produced. Red mud is a solid residue of iron, calcium, aluminum and other compounds and silicon dioxide, with the characteristics of strong alkalinity and high salinity. At present, most alumina plants at home and abroad transport red mud to the yard and store it by wet damming. This method easily causes a large amount of waste alkali liquid to penetrate into the nearby soil, causing soil alkalization. The main chemical composition of red mud is similar to that of silicate cement. At the same time, red mud itself also has certain gelling activity and volcanic ash activity, and has the potential to prepare cementitious materials and geopolymers.

[0004] Construction solid waste refers to the abandoned soil, abandoned materials and other solid wastes generated in the process of building, renovating, expanding and demolishing various buildings, structures, pipelines, etc., as well as in the process of residents decorating and renovating houses. In 2021, my country's construction solid waste emissions reached 3 billion tons, of which abandoned concrete accounted for about 40%. Traditional disposal methods occupy a large amount of land resources and cannot make full use of them. Recycled aggregate refers to the aggregate obtained after a series of processes such as crushing, screening, and cleaning of waste concrete. These aggregates can be used again in the production of building products such as concrete, road foundations, and wall materials to achieve resource recycling. Recycled micropowder is the sand powder remaining after the secondary screening of waste concrete and the hardened cement slurry. It has potential gelling activity and can be used as an auxiliary gelling material. Recycled concrete can reduce the accumulation of construction waste, reduce the demand for new resources, and reduce the impact on the environment. With the advancement of technology and the improvement of environmental awareness, the application of recycled aggregates in concrete is becoming more and more extensive. The comprehensive resource utilization of red mud and construction solid waste in the field of foundation treatment is an effective way to dispose of waste resources. Summary of the invention

[0005] In order to overcome the above problems, the present invention provides a red mud-construction solid waste low-strength composite foundation reinforcement pile method suitable for acidic soil, the main purpose of which is to achieve resource utilization of red mud combined with recycled micropowder and recycled aggregate.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A red mud-construction solid waste low-strength composite foundation reinforcement pile suitable for acidic soil, wherein the raw material components thereof include, by mass, 150-300 parts of red mud, 150-300 parts of recycled micropowder, 500-600 parts of recycled aggregate, 100-200 parts of cement, 50-100 parts of alkali activator and 100-300 parts of water; the pile body material uses red mud and recycled micropowder as auxiliary cementitious materials, and recycled aggregate as filling aggregate, and the potential cementitious activity of red mud is stimulated by the alkali activator, and the red mud-construction solid waste low-strength composite foundation reinforcement pile suitable for acidic soil is formed in combination with cement.

[0008] Furthermore, the red mud is industrial solid waste from the Bayer process for producing alumina, which is dried and ground to a particle size of 8-10 μm.

[0009] Furthermore, the regenerated micro powder is obtained by grinding the sand powder remaining after secondary screening of waste concrete with hardened cement slurry, and the particle size thereof is less than 75 μm.

[0010] Furthermore, the recycled aggregate is the aggregate obtained by crushing and screening waste concrete, including coarse aggregate and fine aggregate, which are not further distinguished, and the particle size distribution is 0.15-50mm.

[0011] Furthermore, the cement is ordinary Portland cement.

[0012] Furthermore, the alkaline activator is sodium hydroxide.

[0013] The present invention also provides a construction method for the red mud-construction solid waste low-strength composite foundation reinforcement piles suitable for acidic soil, comprising the following steps:

[0014] (1) Alkali-activated mix ratio test of indoor pile body mixture

[0015] The pile material uses red mud and recycled micro powder as auxiliary cementitious materials, recycled aggregate as filling aggregate, and uses alkali activator to stimulate the potential cementing activity of red mud, and is combined with cement to form foundation reinforcement piles; according to different construction processes, the corresponding fluid pile material is prepared according to the indoor test mix ratio;

[0016] (2) Pile construction

[0017] Select the pile construction technology according to the designed size of the pile body and the ground conditions, including long spiral drilling and pouring piles, long spiral drilling pipe pumping mixed material piles or vibration sinking pipe pouring piles;

[0018] (3) Pour the pile material and monitor the pH value

[0019] During the construction of foundation reinforcement piles, a soil pH sensor is installed at the feeding port to monitor the pH changes in acidic soil during construction in real time, and adjust the amount of alkali activator accordingly to make the pH value not lower than 11;

[0020] During the sinking or drilling process, use a hopper to feed materials into the pile pipe in the air. After reaching the designed elevation, feed materials as soon as possible. Monitor the pH value of the pile during the feeding process. If the pH value is lower than 11 due to the influence of acidic soil, add alkali activator in time until the pH value is stable and the mixture is flush with the upper feeding port. Then vibrate the pile body from the bottom to the top to ensure that the mixture is dense.

[0021] (4) Natural maintenance and testing

[0022] After confirming that it meets the design requirements for pile formation, the pile is capped with granular material or clay. After natural curing to the specified age, the pile body is cored and tested for performance indicators.

[0023] The present invention has the following beneficial effects:

[0024] 1. Based on the potential gelling activity of red mud and recycled micropowder, the gelling activity is stimulated by using alkaline activator and grinding method, and red mud and recycled micropowder are used as auxiliary gelling materials to achieve resource utilization of waste, reduce cement consumption and reduce carbon emissions.

[0025] 2. Use recycled aggregate as filling aggregate to prepare foundation reinforcement piles, reuse coarse and fine aggregates, reduce the land occupied by the stacking of construction solid waste, reduce environmental pollution, and achieve environmental protection and sustainability of the production process.

[0026] 3. Make full use of the residual alkalinity of red mud and alkali activator to resist the erosion of composite foundation reinforcement piles by acidic soil, ensure the performance of reinforcement piles, and reduce the treatment cost of foundation reinforcement piles to resist acidic soil. DETAILED DESCRIPTION

[0027] The specific embodiments of the present invention are described in detail below.

[0028] The present invention proposes a red mud-construction solid waste low-strength composite foundation reinforcement pile suitable for acidic soil, the raw materials used include original red mud from an aluminum plant in Pingguo, Guangxi, the red mud is dried and ground to a particle size of 8-10 μm; the sand powder remaining after secondary screening of waste concrete after demolition of a building is ground together with hardened cement slurry to obtain a recycled micro powder, the particle size of which is less than 75 μm; the aggregate obtained after crushing and screening of waste concrete after demolition of a building, including coarse aggregate and fine aggregate, no further distinction, and the particle size distribution is 0.15-50 mm.; the alkali activator is a NaOH aqueous solution; and ordinary Portland cement is also included.

[0029] The pile material of the present invention uses red mud and recycled micro powder as auxiliary cementitious materials, recycled aggregate as filling aggregate, stimulates the potential cementitious activity of the red mud through an alkali activator, and forms a foundation reinforcement pile with an appropriate amount of cement.

[0030] In the present invention, a soil pH sensor is arranged on the feeding port during the construction of foundation reinforcement piles, which is used to monitor the pH change in acidic soil during construction in real time, and adjust the dosage of the alkali activator accordingly to make the pH value not lower than 11.

[0031] Example 1

[0032] Red mud, recycled micro powder and recycled aggregate are crushed, ground and sieved to the specified particle size respectively, and then 150 parts of red mud, 150 parts of recycled micro powder, 500 parts of recycled aggregate, 100 parts of cement, 50 parts of alkali activator and 100 parts of water are added into the mixer and stirred for 10 minutes. The slump of the mixture is controlled according to different pile-making processes. The slump of the long spiral drilling pipe pump-pressed mixture pile construction is 160mm~200mm, and the slump of the vibration sinking pipe pouring pile is preferably 30mm~50mm.

[0033] The geological conditions of the site are as follows: the first layer is plain fill with an average thickness of 5.8m, and the second layer is a clay layer with an average thickness of 6.7m, both of which have good strength. There is stagnant water in the upper layer of the site, with a distribution depth of 1.3 to 8.2m. The average pH value of groundwater is 4.5, which is moderately acidic and has a certain corrosiveness to concrete. Combined with the geological conditions, this embodiment adopts long spiral drilling pipes to pump the mixture into piles, control the slump at 160 to 200mm, and the final slump is 185mm, which meets the requirements of pumped mixture.

[0034] Long spiral drilling and pouring piles are used, with a pile diameter of 500mm and a pile length of 8m. During the drilling process, the drilling speed is appropriately adjusted according to the geological conditions, and the verticality of the drill rod is controlled to ensure the accuracy of the pile position. Drilling is stopped when the hole reaches the designed elevation of 8m.

[0035] Pump the pre-mixed mixture and receive the pH sensor data. During the construction process, the pH value varies between 9 and 13. Adjust the amount of alkali activator according to the pH value to keep the pH value not lower than 11. After the pH value reading stabilizes, slowly pump and lift the drill at a speed of 0.5m / min until the designed pile top elevation is reached, completing the production of composite foundation reinforcement piles.

[0036] After confirming that it meets the pile design requirements, the top is sealed with clay and naturally cured to 28 days old. Subsequently, the material of the top 50cm of the pile body is removed, and the pile body is cored three times, and the cores taken out are tested for compressive strength. The compressive strengths of the three groups of cores are 11.86MPa, 12.45MPa, and 12.33MPa, respectively, with an average compressive strength of 12.21MPa, which meets the strength requirements of foundation treatment.

[0037] Example 2

[0038] Red mud, recycled micro powder and recycled aggregate were crushed, ground and sieved to the specified particle size, and then 300 parts of red mud, 200 parts of recycled micro powder, 600 parts of recycled aggregate, 200 parts of cement, 100 parts of alkali activator and 300 parts of water were added into the mixer and stirred for 10 minutes. The slump of the mixture was controlled according to different pile-making processes. The slump of the long spiral drilling pipe pumped mixture pile construction was 160mm~200mm, and the slump of the vibration sinking pipe pouring pile was preferably 30mm~50mm.

[0039] The geological conditions of the site are as follows: the first layer is plain fill with an average thickness of 5.8m, and the second layer is a clay layer with an average thickness of 6.7m, both of which have good strength. There is stagnant water in the upper layer of the site, with a distribution depth of 1.3 to 8.2m. The average pH value of groundwater is 4.5, which is moderately acidic and has a certain corrosiveness to concrete. Combined with the geological conditions, this embodiment adopts long spiral drilling pipes to pump the mixture into piles, control the slump at 160 to 200mm, and the final slump is 178mm, which meets the requirements of pumped mixture.

[0040] Long spiral drilling and pouring piles are used, with a pile diameter of 400mm and a pile length of 6m. During the drilling process, the drilling speed is appropriately adjusted according to the geological conditions, and the verticality of the drill rod is controlled to ensure the accuracy of the pile position. Drilling is stopped when the hole reaches the design elevation of 6m.

[0041] Pump the pre-mixed mixture and receive the pH sensor data. During the construction process, the pH value varies between 10 and 13. Adjust the amount of alkali activator according to the pH value to keep the pH value not lower than 11. After the pH value reading stabilizes, slowly pump and lift the drill at a speed of 0.5m / min until the designed pile top elevation is reached, completing the production of composite foundation reinforcement piles.

[0042] After confirming that it meets the design requirements for pile formation, the pile is capped with clay and naturally cured until the age of 28 days. Subsequently, the material of the top 50 cm of the pile body is removed, and the pile body is cored three times, and the cores taken out are tested for compressive strength. The compressive strengths of the three groups of cores are 14.76 MPa, 15.42 MPa, and 14.89 MPa, respectively, with an average compressive strength of 15.02 MPa, which meets the strength requirements of foundation treatment.

[0043] Example 3

[0044] Red mud, recycled micro powder and recycled aggregate were crushed, ground and sieved to the specified particle size, and then 200 parts of red mud, 300 parts of recycled micro powder, 550 parts of recycled aggregate, 150 parts of cement, 70 parts of alkali activator and 200 parts of water were added into the mixer and stirred for 10 minutes. The slump of the mixture was controlled according to different pile-making processes. The slump of the long spiral drilling pipe pump-pressed mixture pile construction was 160mm-200mm, and the slump of the vibration sinking pipe pouring pile was preferably 30mm-50mm.

[0045] The geological conditions of the site are as follows: the first layer is plain fill with an average thickness of 5.8m, and the second layer is a clay layer with an average thickness of 6.7m, both of which have good strength. There is stagnant water in the upper layer of the site, with a distribution depth of 1.3 to 8.2m. The average pH value of groundwater is 4.5, which is moderately acidic and has a certain corrosiveness to concrete. Combined with the geological conditions, this embodiment adopts long spiral drilling pipes to pump the mixture into piles, control the slump at 160 to 200mm, and the final slump is 176mm, which meets the requirements of pumped mixture.

[0046] Long spiral drilling and pouring piles are used, with a pile diameter of 300mm and a pile length of 5m. During the drilling process, the drilling speed is appropriately adjusted according to the geological conditions, and the verticality of the drill rod is controlled to ensure the accuracy of the pile position. Drilling is stopped when the hole reaches the designed elevation of 5m.

[0047] Pump the pre-mixed mixture and receive the pH sensor data. During the construction process, the pH value varies between 9.5 and 13. Adjust the amount of alkali activator according to the pH value to keep the pH value not lower than 11. After the pH value reading stabilizes, slowly pump and lift the drill at a speed of 0.5m / min until the designed pile top elevation is reached, completing the production of composite foundation reinforcement piles.

[0048] After confirming that it meets the pile design requirements, the top is sealed with clay and naturally cured to 28 days old. Subsequently, the material of the top 50cm of the pile body is removed, and the pile body is cored three times, and the cores taken out are tested for compressive strength. The compressive strengths of the three groups of cores are 13.81MPa, 14.22MPa, and 14.12MPa, respectively, with an average compressive strength of 14.05MPa, which meets the strength requirements of foundation treatment.

[0049] The above-mentioned embodiments illustrate that a red mud-construction solid waste low-strength composite foundation reinforcement pile suitable for acidic soil and a construction method are effective.

[0050] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A red mud-construction solid waste low-strength composite foundation reinforcement pile suitable for acidic soil, characterized by: The raw material components include, by mass, 150-300 parts of red mud, 150-300 parts of recycled micropowder, 500-600 parts of recycled aggregate, 100-200 parts of cement, 50-100 parts of alkali activator and 100-300 parts of water; the pile material uses red mud and recycled micropowder as auxiliary cementitious materials, recycled aggregate as filling aggregate, and the potential cementing activity of red mud is stimulated by the alkali activator, and cement is combined to form red mud-construction solid waste low-strength composite foundation reinforcement piles suitable for acidic soil.

2. The red mud-construction solid waste low-strength composite foundation reinforcement pile suitable for acidic soil according to claim 1, characterized in that: The red mud is industrial solid waste from the Bayer process of producing alumina, which is dried and ground to a particle size of 8-10 μm.

3. The red mud-construction solid waste low-strength composite foundation reinforcement pile suitable for acidic soil according to claim 1, characterized in that: The regenerated micro powder is obtained by grinding the sand powder remaining after secondary screening of waste concrete with hardened cement slurry, and the particle size thereof is less than 75 μm.

4. The red mud-construction solid waste low-strength composite foundation reinforcement pile suitable for acidic soil according to claim 1, characterized in that: The recycled aggregate is the aggregate obtained by crushing and screening waste concrete, including coarse aggregate and fine aggregate, which are not further distinguished, and the particle size distribution is 0.15-50mm.

5. The red mud-construction solid waste low-strength composite foundation reinforcement pile suitable for acidic soil according to claim 1, characterized in that: The cement is ordinary Portland cement.

6. The red mud-construction solid waste low-strength composite foundation reinforcement pile suitable for acidic soil according to claim 1, characterized in that: The alkaline activator is sodium hydroxide.

7. The construction method of red mud-construction solid waste low-strength composite foundation reinforcement piles suitable for acidic soil according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Alkali-activated mix ratio test of indoor pile body mixture The pile material uses red mud and recycled micro powder as auxiliary cementitious materials, recycled aggregate as filling aggregate, and uses alkali activator to stimulate the potential cementitious activity of red mud, and is combined with cement to form foundation reinforcement piles; According to different construction techniques, corresponding fluid pile materials are prepared according to the indoor test mix ratio; (2) Pile construction Select the pile construction technology according to the designed size of the pile body and the ground conditions, including long spiral drilling and pouring piles, long spiral drilling pipe pumping mixed material piles or vibration sinking pipe pouring piles; (3) Pour the pile material and monitor the pH value During the construction of foundation reinforcement piles, a soil pH sensor is installed at the feeding port to monitor the pH changes in acidic soil during construction in real time, and adjust the amount of alkali activator accordingly to make the pH value not lower than 11; During the sinking or drilling process, use a hopper to feed materials into the pile pipe in the air. After reaching the designed elevation, feed materials as soon as possible. Monitor the pH value of the pile during the feeding process. If the pH value is lower than 11 due to the influence of acidic soil, add alkali activator in time until the pH value is stable and the mixture is flush with the upper feeding port. Then vibrate the pile body from the bottom to the top to ensure that the mixture is dense. (4) Natural maintenance and testing After confirming that it meets the design requirements for pile formation, the pile is capped with granular material or clay. After natural curing to the specified age, the pile body is cored and tested for performance indicators.