Low-shrinkage type engineering spoil base light aggregate internal curing concrete

Abstract

The application provides a concrete, raw materials of the concrete include the following components in parts by weight: cement 320-420 parts; mineral admixture 80-105 parts; natural river sand 621-678 parts; engineering waste soil-based lightweight aggregate 273-410 parts; water 150-158 parts; additive 4.8-6.3 parts. The application can effectively utilize the engineering waste soil-based lightweight aggregate, realize high-value utilization of solid waste, and significantly reduce the drying shrinkage of the concrete.

Description

Technical Field

[0001] This invention relates to the field of building materials, specifically to a low-shrinkage lightweight aggregate internal curing concrete for engineering waste soil and its preparation method. Background Technology

[0002] With the continuous advancement of infrastructure construction in my country, the amount of excavated soil from construction projects is increasing daily. Its disposal not only occupies a large amount of land resources but also poses potential environmental pollution and safety hazards. The production of traditional lightweight aggregates (such as expanded clay and perlite) typically requires high-temperature sintering, resulting in high energy consumption, high costs, and the potential for secondary emissions. Therefore, developing non-sintering lightweight aggregates using excavated soil as the main raw material and realizing their application in concrete is of great significance for promoting the resource utilization of solid waste and energy conservation and emission reduction in the construction industry.

[0003] During the hardening process, ordinary concrete undergoes drying shrinkage due to internal moisture evaporation and hydration reactions, leading to cracking and severely impacting the structure's durability and service life. Internal curing technology is one of the effective means to inhibit concrete shrinkage and prevent early cracking. Its principle involves introducing pre-absorbed lightweight porous materials into the concrete, which slowly release water as the internal moisture of the cement paste decreases, promoting later hydration and compensating for shrinkage. Ideal internal curing materials need to possess high water absorption and retention properties. Research shows that aggregates prepared from excavated soil have the potential to serve as internal curing media due to their porous nature. However, if ordinary inorganic cementitious materials (such as cement) are used to solidify excavated soil to prepare aggregates, their volume stability is often poor, making them prone to shrinkage in dry environments. This can actually become a source of shrinkage within the concrete, hindering shrinkage control. In contrast, lightweight aggregates based on excavated soil prepared through carbonation curing processes exhibit significantly better volume stability and are more suitable as reliable internal curing materials. In addition, other existing internal curing materials (such as superabsorbent resin, pre-wetted traditional lightweight aggregate, etc.) often have problems such as high cost, weak interface bonding with cement matrix, or complex process, which limit their widespread application.

[0004] Therefore, how to transform engineering waste soil into lightweight aggregate with stable volume and high water absorption and retention properties through a low-carbon process, and use it to build an efficient internal curing system, thereby synergistically solving the two major problems of solid waste utilization and concrete shrinkage and cracking, has become a technical bottleneck that urgently needs to be overcome. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a low-shrinkage lightweight aggregate internal curing concrete based on engineering waste soil and its preparation method. The concrete uses non-sintering lightweight aggregate prepared from engineering waste soil as an internal curing medium, which significantly reduces the drying shrinkage of concrete while realizing the high-value utilization of solid waste.

[0006] The present invention provides a raw material for the concrete comprising the following components in parts by weight: 320-420 parts cement; 80-105 parts mineral admixtures; 621-678 parts natural river sand; 273-410 parts lightweight aggregate based on engineering waste soil; 150-158 parts water; and 4.8-6.3 parts admixtures.

[0007] Furthermore, the cement is ordinary Portland cement, grade PO 42.5.

[0008] Furthermore, the mineral admixture is one or more of fly ash or granulated blast furnace slag.

[0009] Furthermore, the additive is a polycarboxylate superplasticizer.

[0010] Furthermore, the lightweight aggregate based on the engineering waste soil is a non-sintering lightweight aggregate prepared by carbonization curing of engineering waste soil, and the bulk density of the lightweight aggregate based on the engineering waste soil is 600-1100 kg / m³. 3 The compressive strength of the cylinder is 5.3-12.9MPa; and the proportion of particles with a particle size in the range of 4.75mm-9.5mm is more than 85%.

[0011] Furthermore, the bulk density of the lightweight aggregate used in the engineering waste soil foundation is 600-1100 kg / m³. 3 The compressive strength of the cylinder is 5.3-12.9 MPa.

[0012] Furthermore, the proportion of particles with a particle size in the range of 4.75mm-9.5mm in the lightweight aggregate of the engineering waste soil base is more than 85%.

[0013] Furthermore, it includes the following steps:

[0014] (1) Pretreatment: The lightweight aggregate of the project waste soil is soaked in a saturated calcium hydroxide solution until it is fully saturated with water, then taken out and drained until it is saturated and dry.

[0015] (2) Mixing: Dry mix the pretreated waste soil lightweight aggregate with cement, mineral admixtures and natural river sand. After mixing evenly, add water and admixtures and continue mixing until the mixture is evenly mixed to obtain concrete mixture.

[0016] (3) Molding: The concrete mixture is poured and shaped to obtain the concrete.

[0017] Furthermore, in step (1), the soaking time is no less than 6 hours.

[0018] Furthermore, in step (3), a self-compacting construction process without vibration is used for casting and molding.

[0019] Compared with existing technologies, this invention can effectively utilize lightweight aggregates from engineering waste soil, realize high-value utilization of solid waste, and significantly reduce the drying shrinkage of concrete. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0021] The present invention provides a raw material for the concrete comprising the following components in parts by weight: 320-420 parts cement; 80-105 parts mineral admixtures; 621-678 parts natural river sand; 273-410 parts lightweight aggregate based on engineering waste soil; 150-158 parts water; and 4.8-6.3 parts admixtures.

[0022] Optionally, the cement is ordinary Portland cement of grade PO 42.5.

[0023] Optionally, the mineral admixture is a mineral admixture with alumina as the main active component.

[0024] Optionally, the mineral admixture is one or more of fly ash or granulated blast furnace slag.

[0025] Optionally, the additive is a polycarboxylate superplasticizer.

[0026] Optionally, the 28-day dry apparent density of the concrete is 1350-1650 kg / m³, which falls under the category of lightweight aggregate concrete.

[0027] Optionally, the 90-day drying shrinkage value of the concrete is no greater than 0.28 mm / m, exhibiting excellent low-shrinkage characteristics. Optionally, the lightweight aggregate based on the excavated soil is a non-sintering lightweight aggregate prepared from excavated soil through carbonization curing, and the bulk density of the lightweight aggregate based on the excavated soil is 600-1100 kg / m³. 3 The compressive strength of the cylinder is 5.3-12.9MPa; and the proportion of particles with a particle size in the range of 4.75mm-9.5mm is more than 85%.

[0028] Optionally, the engineering waste soil used in the embodiments of the present invention is the dewatered residual mud with a particle size ≤150 micrometers after the sand and gravel are extracted from the engineering slag, and its moisture content is ≤25%.

[0029] Specifically, the bulk density of the lightweight aggregate used in the engineering waste soil foundation is 600-1100 kg / m³. 3 The compressive strength of the cylinder is 5.3-12.9 MPa.

[0030] Specifically, the proportion of particles with a particle size in the range of 4.75mm-9.5mm in the lightweight aggregate of the project waste soil base is more than 85%.

[0031] Optional, the following steps may be included:

[0032] (1) Pretreatment: The lightweight aggregate of the project waste soil is soaked in a saturated calcium hydroxide solution until it is fully saturated with water, then taken out and drained until it is saturated and dry.

[0033] (2) Mixing: Dry mix the pretreated waste soil lightweight aggregate with cement, mineral admixtures and natural river sand. After mixing evenly, add water and admixtures and continue mixing until the mixture is evenly mixed to obtain concrete mixture.

[0034] (3) Molding: The concrete mixture is poured and shaped to obtain the concrete.

[0035] Specifically, in step (1), the soaking time is no less than 6 hours.

[0036] In particular, step (3) uses a self-compacting construction process that does not require vibration to cast the concrete.

[0037] To further illustrate the specific implementation of the present invention, specific embodiments are listed below.

[0038] The lightweight aggregate used in the carbonization curing engineering waste soil of Examples 1-3 of this invention has a moisture content of 18.5%; the cementitious material used is rapid-hardening sulfoaluminate cement with a strength grade of 42.5 MPa; the foaming agent used is dry aluminum powder with an active aluminum content ≥98.0%; the foam stabilizer used is analytical grade calcium stearate; the reinforcing agent used is calcium oxide powder with a CaO content ≥98.0%; the high-calcium industrial wastewater used is wastewater discharged from a cement plant with a calcium hydroxide concentration of 0.78 g / L; the carbon-rich industrial tail gas used is simulated cement kiln exhaust gas, composed of carbon dioxide, sulfur dioxide, and nitrogen dioxide, with a carbon dioxide concentration of 72%; and the curing box used is a carbonization reaction vessel with temperature control function.

[0039] The preparation method of the lightweight aggregate based on the waste soil from the carbonization curing project is as follows:

[0040] The excavated soil, cementitious materials, foaming agent, foam stabilizer, and reinforcing agent are mixed and stirred slowly until homogeneous to obtain a mixture.

[0041] After mixing high-calcium industrial wastewater with the mixture, the mixture is stirred rapidly and then granulated to obtain lightweight aggregate particles.

[0042] Lightweight aggregate particles are cured with carbon-rich industrial waste gas for 3-36 hours to obtain non-sintering lightweight aggregate for engineering waste soil.

[0043] Example 1

[0044] This embodiment aims to compare the effects of different lightweight aggregate preparation processes and pretreatment methods on concrete performance. The concrete foundation mix proportion was fixed (per 1 m³): 320 kg cement, 80 kg fly ash, 678 kg natural river sand, 150 kg water, and 4.8 kg polycarboxylate superplasticizer. The lightweight aggregate dosage was fixed at 335 kg / m³. 3 Four comparative experiments were conducted by changing the type of lightweight aggregate and the pretreatment method. The specific types of lightweight aggregate are as follows:

[0045] Group 1-A (Commercial Control): Commercially available non-sintered ceramsite (non-engineering waste soil base) was used, with a bulk density of 820 kg / m³. 3 Soak in clean water for 6 hours before use, then drain until saturated and dry.

[0046] Group 1-B (Process Control): Lightweight aggregate from cement-cured excavated soil used in engineering projects without carbonization curing, with a bulk density of 830 kg / m³. 3 Soak in clean water for 6 hours before use, then drain until saturated and surface dry. The lightweight aggregate for the engineering waste soil base consists of 75 parts engineering waste soil, 15 parts cementitious material, 10 parts reinforcing agent, 22.7 parts high-calcium industrial wastewater, 1 part foaming agent, and 0.4 parts foam stabilizer.

[0047] Group 1-C (Process Experiment Group): Lightweight aggregate from engineering waste soil that has undergone carbonization curing, with a bulk density of 805 kg / m³. 3 Soak in clean water for 6 hours before use, then drain until saturated and surface dry. The lightweight aggregate for the engineering waste soil base consists of 75 parts engineering waste soil, 15 parts cementitious material, 10 parts reinforcing agent, 22.7 parts high-calcium industrial wastewater, 1.1 parts foaming agent, and 0.4 parts foam stabilizer. The CO2 concentration of the carbon-rich industrial tail gas used is 72%, the temperature is 40℃, and the curing time is 12 hours.

[0048] Group 1-D (Core Invention Group): Uses the same batch of carbonized engineering waste soil-based lightweight aggregate as Group 1-C, with a bulk density of 805 kg / m³. 3 Before use, soak in a saturated calcium hydroxide solution for 6 hours, then drain until saturated and surface dry.

[0049] Concrete was prepared according to the method described in claim 8: (1) the lightweight aggregate was pretreated accordingly; (2) the pretreated aggregate was dry-mixed with cement, fly ash and river sand for 1 minute, and then water and water-reducing agent were added and stirred for 3 minutes until uniform; (3) the mixture was poured into a mold, self-compacted, and cured under standard curing conditions (temperature 20±2°C, relative humidity ≥95%) until the specified age for testing. The performance test results are shown in the table below.

[0050]

[0051] As can be seen from the table above, the 1-D group using the lightweight aggregate treatment method of the present invention has a significant improvement in compressive strength and a significant improvement in drying shrinkage value.

[0052] Example 2

[0053] This embodiment aims to investigate the effects of lightweight aggregates (all pretreated with saturated calcium hydroxide solution) of carbonized engineering waste soil with different bulk densities on concrete performance. The concrete foundation mix proportion was fixed as follows: 320 kg cement, 80 kg fly ash, 678 kg natural river sand, 150 kg water, and 4.8 kg polycarboxylate superplasticizer. Four types of aggregates with different densities (all treated using the 1-D group of lightweight aggregates) were used, and their mass usage was determined based on the principle of similar volume. The specific groupings are as follows:

[0054] Group 2-A: Aggregate bulk density 608 kg / m³ 3 The dosage is 273 kg. The lightweight aggregate for the engineering waste soil base consists of 75 parts engineering waste soil, 15 parts cementitious material, 10 parts reinforcing agent, 22.7 parts high-calcium industrial wastewater, 1.6 parts foaming agent, and 0.5 parts foam stabilizer. The CO2 concentration of the carbon-rich industrial tail gas used is 72%, the temperature is 40℃, and the curing time is 12 hours.

[0055] Group 2-B: Aggregate bulk density 755 kg / m³ 3 The dosage is 335 kg. The lightweight aggregate for the engineering waste soil base consists of 75 parts engineering waste soil, 15 parts cementitious material, 10 parts reinforcing agent, 22.7 parts high-calcium industrial wastewater, 1.2 parts foaming agent, and 0.4 parts foam stabilizer. The CO2 concentration of the carbon-rich industrial tail gas used is 72%, the temperature is 40℃, and the curing time is 12 hours.

[0056] Group 2-C: Aggregate bulk density 980 kg / m³ 3 The dosage is 418 kg. The lightweight aggregate for the engineering waste soil base consists of 75 parts engineering waste soil, 15 parts cementitious material, 10 parts reinforcing agent, 22.7 parts high-calcium industrial wastewater, 0.7 parts foaming agent, and 0.2 parts foam stabilizer. The CO2 concentration of the carbon-rich industrial tail gas used is 72%, the temperature is 40℃, and the curing time is 12 hours.

[0057] Group 2-D: Aggregate bulk density 1085 kg / m³ 3 The dosage is 507 kg. The lightweight aggregate for the engineering waste soil base consists of 75 parts engineering waste soil, 15 parts cementitious material, 10 parts reinforcing agent, 22.7 parts high-calcium industrial wastewater, 0.3 parts foaming agent, and 0.1 parts foam stabilizer. The CO2 concentration of the carbon-rich industrial tail gas used is 72%, the temperature is 40℃, and the curing time is 12 hours.

[0058] The preparation and testing methods are the same as in Example 1. The performance test results are shown in the table below.

[0059]

[0060] It can be seen that the higher the bulk density of the aggregate, the significantly higher its compressive strength, while the drying shrinkage value gradually increases, but overall it meets the requirements of building materials for drying shrinkage value.

[0061] Example 3

[0062] This embodiment aims to verify that the present invention can still achieve excellent low-shrinkage performance even with a high amount of cementitious materials. The fixed concrete foundation mix proportion is: 420 kg cement, 105 kg fly ash, 621 kg natural river sand, 158 kg water, and 6.3 kg polycarboxylate superplasticizer. The type of aggregate used, the pretreatment method, and the grouping are the same as in Example 2. The preparation and testing methods are the same as in Example 1. The performance test results are shown in the table below.

[0063]

[0064] It can be seen that with a higher amount of cementitious material, the compressive strength and drying shrinkage value of each group are significantly improved.

[0065] In this embodiment of the invention, lightweight aggregate based on excavated soil treated with carbonation is used as an internal curing material. This lightweight aggregate has the characteristics of being porous, highly absorbent, and volume stable. In the preparation process, the lightweight aggregate is first pretreated with a saturated calcium hydroxide solution and then applied to the preparation of lightweight aggregate concrete. During the concrete hardening stage, the pretreated lightweight aggregate plays the following synergistic role: (1) it continuously provides moisture for cement hydration through internal curing, promoting the later hydration reaction; (2) secondly, it provides sufficient calcium source in the transition zone of the lightweight aggregate-cementing material interface, achieving targeted strengthening of the interface structure; (3) the calcium ions immersed in the pores of the lightweight aggregate can react with the silica gel generated by carbonation to generate calcium silicate gel, thereby improving the strength of the lightweight aggregate itself; at the same time, the stable calcium carbonate crystal skeleton can effectively ensure the volume stability of the aggregate during service and reduce the drying shrinkage value.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading this application specification, they can still modify or make equivalent substitutions to the specific implementation of the present invention, but these modifications or changes do not depart from the protection scope of the pending claims of the present invention.

Claims

1. A low-shrinkage lightweight aggregate internally cured concrete for engineering waste soil foundations, characterized in that, The raw materials of the concrete include the following components in parts by weight: 320-420 parts cement; 80-105 parts mineral admixtures; 621-678 parts natural river sand; 273-410 parts lightweight aggregate from engineering waste soil; 150-158 parts water; and 4.8-6.3 parts admixtures.

2. The low-shrinkage lightweight aggregate internally cured concrete for engineering waste soil foundations according to claim 1, characterized in that, The cement is ordinary Portland cement, grade PO 42.

5.

3. The low-shrinkage lightweight aggregate internally cured concrete for engineering waste soil foundations according to claim 1, characterized in that, The mineral admixture is one or more of fly ash or granulated blast furnace slag.

4. The low-shrinkage lightweight aggregate internally cured concrete for engineering waste soil foundations according to claim 1, characterized in that, The additive is a polycarboxylate superplasticizer.

5. The low-shrinkage lightweight aggregate internally cured concrete for engineering waste soil foundations according to claim 1, characterized in that, The lightweight aggregate based on the engineering waste soil is a non-sintering lightweight aggregate prepared by carbonization curing of engineering waste soil, and the bulk density of the lightweight aggregate based on the engineering waste soil is 600-1100 kg / m³. 3 The compressive strength of the cylinder is 5.3-12.9MPa; and the proportion of particles with a particle size in the range of 4.75mm-9.5mm is more than 85%.

6. The low-shrinkage lightweight aggregate internally cured concrete for engineering waste soil foundations according to claim 5, characterized in that, The bulk density of the lightweight aggregate used in the project's spoil heap is 600-1100 kg / m³. 3 The compressive strength of the cylinder is 5.3-12.9 MPa.

7. The low-shrinkage lightweight aggregate internally cured concrete for engineering waste soil foundations according to claim 5 or 6, characterized in that, The proportion of particles with a particle size in the range of 4.75mm-9.5mm in the lightweight aggregate of the project's waste soil base is over 85%.

8. The low-shrinkage lightweight aggregate internally cured concrete for engineering waste soil foundations according to claim 1, characterized in that, Includes the following steps: (1) Pretreatment: The lightweight aggregate of the project waste soil is soaked in a saturated calcium hydroxide solution until it is fully saturated with water, then taken out and drained until it is saturated and dry. (2) Mixing: Dry mix the pretreated waste soil lightweight aggregate with cement, mineral admixtures and natural river sand. After mixing evenly, add water and admixtures and continue mixing until the mixture is evenly mixed to obtain concrete mixture. (3) Molding: The concrete mixture is poured and shaped to obtain the concrete.

9. The low-shrinkage lightweight aggregate internally cured concrete for engineering waste soil foundations according to claim 8, characterized in that, In step (1), the soaking time shall be no less than 6 hours.

10. The low-shrinkage lightweight aggregate internally cured concrete for engineering waste soil foundations according to claim 8, characterized in that, In step (3), a self-compacting construction process without vibration is used for casting and molding.

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