CN103275730B - Barium-containing sulphoaluminate soft soil curing agent and preparation method thereof - Google Patents

Abstract

The present invention relates to the field of soft soil curing agents, and specifically provides a barium-containing sulfoaluminate soft soil curing agent and a preparation method thereof, the components of which include: (1) barium-containing sulfoaluminate clinker 50wt%~80wt%; (2) Calcined gypsum 25wt%~40wt%; (3) Lime 10wt%~12wt%; (4) Water retaining agent 0.5wt%~2wt%; (5) Retarder 0.5wt%~5wt%. The preparation process includes calcining natural gypsum and mixing and grinding ingredients. The soft soil curing agent has the characteristics of fast setting, high strength, and no shrinkage of the volume of the solidified soil. It can form full strength within 1 to 3 days after curing, and is especially suitable for rapid maintenance and reinforcement of road foundations. Under the same addition amount, the unconfined compressive strength of the reinforced soil using the soft soil curing agent is significantly higher than that of the reinforced soil using P.C32.5 ordinary Portland cement, and the reinforcement effect is remarkable.

Description

Barium-containing sulfoaluminate soft soil curing agent and preparation method thereof

technical field

The invention relates to the field of soft soil curing agents, in particular to a barium-containing sulfoaluminate soft soil curing agent and a preparation method thereof.

Background technique

Soft soil refers to a type of soil with low bearing capacity, large void ratio, high water content and high compressibility. Reinforcement of soft soil foundation has become one of the hot topics in engineering construction and maintenance. There are many methods of soft soil reinforcement, such as compaction reinforcement, heat treatment reinforcement, and chemical reinforcement. Among them, curing agent reinforcement of soft soil has become the most widely used method of soft soil reinforcement because of its low cost and relatively simple construction. .

Soft soil curing agent refers to materials that can directly cement soil particles at room temperature, or can react with clay minerals to form cementitious substances, thereby improving the physical properties of soil. Soft soil curing agents can be divided into calcium-based curing agents (cement, lime, fly ash, slag, etc.) and non-calcium-based curing agents (ionic curing agents, enzyme curing agents, polymer curing agents, etc.) according to their main components. . At present, the soft soil curing agents that are widely used in China mainly include cement, lime, and fly ash.

Lime, fly ash (fly ash and lime) are low-cost curing agents and are widely used to consolidate expansive soils, but they have been found to have many disadvantages in application. For example, the curing effect is slow, and generally it takes 7 to 28 days to form a certain strength after construction; the strength of the solidified soil is uncontrollable; the water stability is poor, and the general lime soil or lime soil loses its strength after being soaked in water.

The strength of cement-reinforced soil increases rapidly, and the cost is relatively high. It is widely used in the solidification of soft soil with various particle sizes. However, when dealing with cohesive soil, it is easy to mix unevenly with the soil, and the ideal effect cannot be obtained. The cement paste is strongly alkaline, and the pH value is generally greater than 12, which is not conducive to environmental protection, and the volume of ordinary Portland cement shrinks after hydration, and it is easy to form cracks in the solidified soil.

The molecular formula of barium-containing sulfoaluminate mineral is (3-x)CaO·xBaO·3Al ₂ O ₃ ·CaSO ₄ , where x=0.25~3, which is made of aluminum raw materials (such as bauxite), calcareous raw materials ( Such as limestone), gypsum, and barite are made at a temperature of 1200~1300°C. Its hydration speed is very fast, and it has the characteristics of early strength and high strength. Generally, the full strength can be formed within 3 days, and its 3-day strength is equivalent to the 28-day strength of Portland cement of the same label. During hydration, a large amount of free water can be consumed to form ettringite and aluminum hydroxide gel, and the hydrate has better water stability and antifreeze performance. The pH value of the hydration slurry is less than 12, which is beneficial to protect the environment, and the preparation temperature of the barium-containing sulfoaluminate mineral is 100-200°C lower than that of ordinary Portland cement, which is also conducive to reducing energy consumption.

Rapid hardening sulphoaluminate cement, high-strength sulphoaluminate cement, expansive sulphoaluminate cement, self-stressing sulphoaluminate cement, and low-alkalinity sulphoaluminate cement have been developed domestically. There are five types of salt cement, and the technology is mature. It only needs to slightly change the ratio of raw materials to produce barium-containing sulfoaluminate clinker.

At present, the published patents on barium-containing sulfoaluminate include: barium-containing sulfoaluminate cement (publication number: CN1035486A); a cement-based anti-seepage and plugging material (publication number: CN1526785A). After searching, no patent application or literature report about making a soft soil curing agent from barium-containing sulfoaluminate was found.

Contents of the invention

Aiming at the deficiency of the existing soft soil curing agent, the invention provides a formula and a preparation method of a novel barium-containing sulphoaluminate soft soil curing agent.

The invention provides a kind of soft soil solidifying agent, and its component and each component weight percentage are:

(1) Barium-containing sulfoaluminate clinker 50~80%

(2) Calcined gypsum 25~40%

(3) Lime 10~12%

(4) Water retaining agent 0.5~2%

(5) Retarder 0.5~5%

The mineral composition weight percent of the barium-containing sulfoaluminate clinker used in this soft soil solidifying agent is:

(1) Barium-containing sulfoaluminate [(3-x)CaO·xBaO·3Al ₂ O ₃ ·CaSO ₄ , where x=0.25~3] 55~75wt%

(2) Dicalcium silicate (2CaO·SiO ₂ ) 8~37%

(3) Iron phase (2CaO·Fe ₂ O ₃ -6CaO·2Al ₂ O ₃ ·Fe ₂ O ₃ ) 3~10%

The calcined gypsum used in this soft soil curing agent is made by calcining natural gypsum at 300°C for 30 minutes.

The water-retaining agent used in this soft soil curing agent is any one of polyacrylamide, sodium polyacrylate, potassium polyacrylate, ammonium polyacrylate or starch grafted acrylate; the retarder is starch, sucrose, glucose, lignin Calcium acid salt, sodium carboxymethylcellulose, carboxyethylcellulose, sodium hexametaphosphate or sodium citrate.

The soft soil curing agent of the present invention is made by grinding barium-containing sulfoaluminate clinker as the main raw material, adding calcined gypsum, lime, water-retaining agent and retarder, and controlling the specific surface area of the curing agent powder particles to be 300-400m ² /kg.

Barium-containing sulfoaluminate is made of aluminum raw materials (such as bauxite), calcareous raw materials (such as limestone), gypsum, and barite raw materials, which are calcined at a temperature of 1200~1300 °C after proper mixing. Material. In the liquid phase filled with gypsum, the barium-containing sulfoaluminate will undergo hydration reaction to form ettringite and aluminum hydroxide gel. The reaction equation is as follows:

(3-x)CaO·xBaO·3Al ₂ O ₃ ·CaSO ₄ + 2CaSO ₄ + 38H ₂ O → (3-x)CaO·xBaO·Al ₂ O ₃ ·3CaSO ₄ ·32H ₂ O + 2(Al ₂ O ₃ ·3H ₂ O)(gel), where x=0.25~3

Under alkaline conditions, aluminum hydroxide gel can react with gypsum and calcium hydroxide to further generate ettringite. The reaction equation is as follows:

Al ₂ O ₃ 3H ₂ O+3CaSO ₄ +3Ca(OH) ₂ +26H ₂ O→3CaO Al ₂ O ₃ 3CaSO ₄ 32H ₂ O

The soft soil curing agent of the present invention utilizes the hydration reaction of barium-containing sulfoaluminate minerals, and its curing mechanism is as follows: the soft soil curing agent is added to saturated soft soil, and the barium-containing sulfoaluminate is immediately mixed with the soil The free water reacts, and in the liquid phase filled with gypsum and calcium hydroxide, a large amount of ettringite is generated. The overall reaction formula is as follows:

(3-x)CaO·xBaO·3Al ₂ O ₃ ·CaSO ₄ + 8CaSO ₄ + 6Ca(OH) ₂ + 90H ₂ O → 3[(3-y)CaO·yBaO·Al ₂ O ₃ ·3CaSO ₄ ·32H ₂ O], where x=0.25~3, y=0.08~1

Through the above hydration reaction, the liquid free water in the soft soil is converted into solid crystal water, reducing the content of free water and some weakly bound water in the soft soil, and the generated acicular ettringite minerals can cement soil particles and form new The skeleton structure supports the entire soil mass. It is calculated that about 3.0 kg of water can be solidified per 1 kg of barium-containing sulfoaluminate mineral, and about 6.4 kg of ettringite can be produced at the same time. At the same time, the lime in the curing agent hydrates to form calcium hydroxide, which makes the soft soil alkaline, which can promote the hardening reaction of the active silicon and aluminum components in the soft soil, and directly generate hydrated calcium silicate or calcium aluminate minerals. cemented particles. Ca ²⁺ can also ion-exchange with Na ⁺ and K ⁺ ions in the soil, reduce the amount of cations adsorbed by soil colloidal particles, and then reduce the thickness of the diffusion layer, and promote the aggregation of soil particles to form larger soil clusters.

The soft soil solidifying agent of the present invention has fast curing speed and high strength of solidified soil, and generally can form full strength within 1 to 3 days, and is especially suitable for fast maintenance and reinforcement of road foundations. The hydration product of the curing agent is mainly ettringite, which slightly expands in volume after hydration, which can avoid the disadvantage of ordinary Portland cement shrinking in volume after hydration and causing cracks in the solidified soil.

4. Specific implementation

The present invention is described in detail through examples below, and the characteristics of the soft soil curing agent of the present invention are illustrated by taking cement as a comparison. It is necessary to point out that this embodiment is only used to further illustrate the present invention, and cannot be interpreted as limiting the protection scope of the present invention. Those skilled in the art can make some non-essential improvements and adjustments according to the content of the above-mentioned invention .

1 Embodiment 1～3 and comparative example 1

54.6wt% barium-containing sulfoaluminate clinker was ground together with 34.4wt% calcined gypsum, 10% lime, 0.5wt% polyacrylamide water retaining agent, and 0.5wt% sodium citrate retarder to make a curing agent. The soft soil to be reinforced is taken from the yellow fine-grained heavy clay in Chengdu. The soil is dried at 110°C for 24 hours and crushed with a rubber hammer until it passes through a 3mm round-hole sieve. Add 18.18wt%, 22.22wt%, 28.57wt% curing agent and 28.57wt% P.C32.5 ordinary Portland cement to the dried soil respectively, stir evenly, add distilled water according to the moisture content of 60%, and stir for 2 minutes Finally, pour the slurry into a 40×40×160mm cement mortar trial mold and vibrate to form it. The solidified soil was sealed together with the mold, and cured at 20°C for 1 day and 3 days, and the unconfined compressive strength of the solidified soil was measured after demoulding. The materials and strengths of this embodiment and comparative examples are shown in Table 1.

Table 1 Unconfined compressive strength of yellow clay reinforced with curing agent and cement

serial number Curing agent (cement) content 1 day unconfined compressive strength/KPa 3-day unconfined compressive strength/KPa Example 1 18.18wt% 446.83 458.46 Example 2 22.22wt% 1170.64 1124.65 Example 3 28.57wt% 2263.77 2278.59 Comparative example 1 28.57wt% 716.91 1697.42

2 Embodiment 4～6 and comparative example 2

54.6wt% barium-containing sulfoaluminate clinker was ground together with 34.4wt% calcined gypsum, 10% lime, 0.5wt% polyacrylamide water retaining agent, and 0.5wt% sodium citrate retarder to make a curing agent. The soft soil to be reinforced is taken from reticulated red silty clay in Chengdu. The soil has been dried at 110°C for 24 hours and crushed with a rubber hammer until it passes through a 3mm round hole sieve. Add 18.18wt%, 22.22wt%, 28.57wt% curing agent and 28.57wt% P.C32.5 ordinary Portland cement to the dried soil respectively, stir evenly, add distilled water according to the moisture content of 60%, and stir for 2 minutes Finally, pour the slurry into a 40×40×160mm cement mortar trial mold and vibrate to form it. The solidified soil was sealed together with the mold, and cured at 20°C for 1 day and 3 days, and the unconfined compressive strength of the solidified soil was measured after demoulding. The materials and strengths of this embodiment and comparative examples are shown in Table 2.

Table 2 Unconfined compressive strength of red silty clay reinforced with curing agent and cement

serial number Curing agent (cement) content 1 day unconfined compressive strength/KPa 3-day unconfined compressive strength/KPa Example 4 18.18wt% 241.41 233.93 Example 5 22.22wt% 586.13 665.42 Example 6 28.57wt% 1933.36 2034.76 Comparative example 2 28.57wt% 382.43 791.91

3 Examples 7-9 and Comparative Example 3

54.6wt% barium-containing sulfoaluminate clinker was ground together with 34.4wt% calcined gypsum, 10% lime, 0.5wt% polyacrylamide water retaining agent, and 0.5wt% sodium citrate retarder to make a curing agent. The soft soil to be reinforced is taken from the fine-grained saturated organic soil in Chengdu. The soil was dried at 110°C for 24 hours and crushed with a rubber hammer until all of it passed through a 3mm round hole sieve. Add 18.18wt%, 22.22wt%, 28.57wt% curing agent and 28.57wt% P.C32.5 ordinary Portland cement to the dried soil respectively, stir evenly, add distilled water according to the moisture content of 60%, and stir for 2 minutes Finally, pour the slurry into a 40×40×160mm cement mortar trial mold and vibrate to form it. The solidified soil was sealed together with the mold, and cured at 20°C for 1 day and 3 days, and the unconfined compressive strength of the solidified soil was measured after demoulding. The materials and strengths of this embodiment and comparative examples are shown in Table 3.

Table 3 Unconfined compressive strength of fine-grained organic soil reinforced with curing agent and cement

serial number Curing agent (cement) content 1 day unconfined compressive strength/KPa 3-day unconfined compressive strength/KPa Example 7 18.18wt% 666.43 647.09 Example 8 22.22wt% 1122.79 1073.58 Example 9 28.57wt% 2574.21 2715.09 Comparative example 3 28.57wt% 519.84 858.90

Claims (1)

1. the preparation method of barium-containing sulfoaluminate soft soil solidifying agent is characterized in that technological process comprises the following steps: (1) Preparation of calcined gypsum: Grind the natural gypsum with a grinder to form particles with a diameter of 75-96 μm, add water and make pellets with a diameter of 2-20 mm on a ball forming machine, and calcinate at a temperature of 250-350 ° C for 30 minutes; (2) Add calcined gypsum, lime, water retaining agent and retarder to barium-containing sulfoaluminate clinker calcined by conventional methods, and grind it with a grinder at room temperature until the specific surface area of the mixture particles is 300-400m ² /kg, That is, the barium-containing sulfoaluminate soft soil curing agent is obtained; The components of the prepared barium-containing sulfoaluminate soft soil curing agent include barium-containing sulfoaluminate clinker, calcined gypsum, lime, water retaining agent and retarder, and the weight percentage of each component is: The sum of the percentages of the above components is 100%.