CN110218073A - Dredging silt dehydrating and curing calcium and magnesium based composites and the preparation method and application thereof - Google Patents

Abstract

The present invention provides a kind of dredging silt dehydrating and curing calcium and magnesium based composites and the preparation method and application thereof, it can effectively solve the problem that the problems such as dredging silt high-moisture percentage, low bearing capacity, low resistance to compression shearing strength, have mud through processing and have good physical and mechanical property.Dredging silt dehydrating and curing calcium and magnesium based composites provided by the present invention, in terms of dry powder, including following components: resin SAP:0.25~1wt.%, cement: 6~12wt.%, reheating MgO:6~15wt.%, magnesium phosphate: 8~22wt.%, metakaolin: 6~18wt.%, active MgO:6~15wt.%, magnesium chloride: 10~25wt.%, quick lime: 2~4wt.%, sodium metasilicate: 3~8wt.%, sodium hydroxide: 3~6wt.%, slag powders: 15~40wt.%, flyash: 10~30wt.%.

Description

Calcium-magnesium-based composite material for dehydration and solidification of dredged silt and its preparation method and application

technical field

The invention belongs to the field of building materials, and in particular relates to a calcium-magnesium-based composite material for dehydration and solidification of dredged silt, a preparation method and application thereof.

technical background

During the dredging and dredging process of inland lakes, port roadways and river sediments in my country, a large amount of dredged silt with high water content (even as high as 200-300%) and a certain risk of polluting the surrounding environment will inevitably be produced. These silts usually have high clay content, high moisture content, low shear strength, poor bearing capacity, and emit a foul smell. They do not need to be stacked for a long time, not only occupying a large amount of cultivated land, polluting the land environment, but also difficult to be directly used as engineering fillers. Therefore, the problem of co-processing of dredged silt dehydration and solidification is a thorny problem that needs to be solved urgently under the background that my country attaches great importance to environmental protection.

At present, engineering waste mud is generally treated by landfill or offshore disposal. Due to the disadvantages of environmental pollution and high risk of transportation leakage, it may be gradually abandoned for use. If it is not properly disposed of, it will inevitably occupy a shortage of land resources and pollute the ecological environment. The solidification and stabilization treatment method is adopted, that is, adding solidification materials to the sludge to effectively improve the engineering properties of the sludge such as strength, deformation and permeability, and transform the waste dredged sludge into geotechnical materials that meet engineering standards, are renewable, low-pollution or even pollution-free filler. The modified silt after solidification treatment can be used as filling material for road subgrade filling, landfill filling and other fields, which is in line with the concept of sustainable development and solid waste resource recycling in my country.

There are many types of solidification materials used in sludge solidification disposal, mainly including: lime, cement, steel slag, fly ash and other traditional materials. When dealing with dredging such silt, the effect of water reduction and reinforcement is usually not ideal, and even the amount of curing agent is too large, resulting in high processing costs. The above materials are single in proportion and cannot take advantage of the advantages of mixing multiple materials and magnesium-based composite materials. Therefore, it is of high engineering significance and practical value to develop economical and efficient dehydration-solidified calcium-magnesium-based composite materials suitable for dredging sludge with high water content to replace or partially replace high-emission and high-energy-consuming materials such as cement and lime.

Contents of the invention

The present invention is carried out in order to solve the above problems, and the purpose is to provide a calcium-magnesium-based composite material for dehydration and solidification of dredged silt and its preparation method and application. It has the advantages of excellent dehydration performance, good curing effect, ecological environmental protection, and reasonable cost. Effectively solve the problems of high water content, low bearing capacity, low compressive and shear strength of dredged silt, so that the treated silt has good physical and mechanical properties.

In order to achieve the above object, the present invention adopts the following scheme:

<composite material>

The invention provides a calcium-magnesium-based composite material for dehydration and solidification of dredged silt, which is characterized in that, in terms of dry powder, it comprises the following components: resin SAP: 0.25-1wt.%, cement: 6-12wt.%, dead-burned MgO: 6 ～15wt.%, magnesium phosphate: 8～22wt.%, metakaolin: 6～18wt.%, active MgO: 6～15wt.%, magnesium chloride: 10～25wt.%, quicklime: 2～4wt.%, silicic acid Sodium: 3-8wt.%, sodium hydroxide: 3-6wt.%, slag powder: 15-40wt.%, fly ash: 10-30wt.%, the sum of the percentages of each component is 100.

Preferably, the calcium-magnesium-based composite material provided by the present invention for dehydration and solidification of dredged sludge can also have the following characteristics: the active magnesium oxide is highly active MgO, and the MgO content is ≥ 92wt.%.

Preferably, the calcium-magnesium-based composite material for dehydration and solidification of dredged sludge provided by the present invention may also have the following characteristics: the dead-burned magnesium oxide is MgO with low activity, the burning temperature is >1200°C, and the MgO content is ≥94wt.%.

Preferably, the calcium-magnesium-based composite material provided by the present invention for dehydration and solidification of dredged sludge may also have the following characteristics: the magnesium chloride is analytically pure, and the content of MgCl ₂ ·6H ₂ O is ≥98wt.%.

Preferably, the calcium-magnesium-based composite material provided by the present invention for dehydration and solidification of dredged sludge can also have the following characteristics: the magnesium phosphate is analytically pure, and the MgPO ₄ content is ≥ 95wt.%.

In addition, the calcium-magnesium-based composite material provided by the invention for dehydration and solidification of dredged sludge may also include: CaO content in quicklime ≥ 95wt.%.

Preferably, the calcium-magnesium-based composite material provided by the present invention for dehydration and solidification of dredged sludge may also have the following characteristics: sodium silicate is a dry powder sample, and the Na ₂ SiO ₃ content is ≥ 99 wt.%.

Preferably, the dredged silt dehydration-solidified calcium-magnesium-based composite material provided by the present invention can also have the following characteristics: in the fly ash, the sum of the mass percentages of _Al2O3 and _SiO2 is _≥70wt .%, and the CaO content does not need to be limited .

Preferably, the calcium-magnesium-based composite material for dehydration and solidification of dredged sludge provided by the present invention may also have the following characteristics: the fly ash is secondary fly ash.

Preferably, the calcium-magnesium matrix composite material provided by the present invention for dehydration and solidification of dredged sludge may also have the following characteristics: the slag powder is granulated blast furnace slag powder, and the content of Al ₂ O ₃ +SiO ₂ +CaO in the slag is ≥85wt.%.

Preferably, the calcium-magnesium-based composite material provided by the present invention for dehydration and solidification of dredged sludge may also have the following characteristics: the cement is ordinary Portland cement.

Preferably, the calcium-magnesium-based composite material for dehydration and solidification of dredged sludge provided by the present invention may also have the following characteristics: sodium hydroxide is high-purity NaOH dry powder, and its NaOH content is ≥ 99%.

<Preparation method>

Furthermore, the present invention also provides a method for preparing a calcium-magnesium-based composite material for dehydration and solidification of dredged sludge, which is characterized in that it includes: weighing the dry powder of each component according to the proportion, resin SAP: 0.25-1wt.%, cement: 6 ～12wt.%, dead-burned MgO: 6～15wt.%, magnesium phosphate: 8～22wt.%, metakaolin: 6～18wt.%, active MgO: 6～15wt.%, magnesium chloride: 10～25wt.%, Quick lime: 2～4wt.%, sodium silicate: 3～8wt.%, sodium hydroxide: 3～6wt.%, slag powder: 15～40wt.%, and fly ash: 10～30wt.%. Then carry out Mix and evenly mix to obtain the dehydrated and solidified calcium-magnesium matrix composite material of the dredged sludge.

<application>

Further, the present invention also provides the application of the dewatered and solidified calcium-magnesium-based composite material of dredging silt in the reinforcement of soft soil foundation and construction mud.

Function and Effect of Invention

The technical principle of the calcium-magnesium-based composite material for dehydration and solidification of dredged silt disclosed by the present invention is that the resin SAP can utilize the characteristics of a water-swellable high molecular polymer that contains strong hydrophilic groups such as carboxyl and hydroxyl groups and has a certain degree of crosslinking, Quickly absorb water to reduce the initial moisture content of the sludge significantly, and achieve the effect of water reduction and enhancement in a short period of time; ordinary Portland cement undergoes hydration reaction quickly when it encounters water, forming calcium silicate hydrate CSH and calcium aluminate hydrate CAH and Ca(OH) ₂ , and create a high-alkaline and high-pH solution environment, which can promote the rapid increase of the early strength of the sludge; quicklime quickly generates Ca(OH) ₂ and releases a certain amount of heat when it meets water, which can accelerate water evaporation and promote water conversion The double function of the chemical reaction is rapid dehydration and thickening in the early stage of the chemical reaction; the highly active MgO reacts with water to generate Mg(OH) ₂ , which can provide an alkaline environment and cause volume expansion to cause a compaction effect, while the active MgO and magnesium chloride A chemical reaction occurs to generate 5·1·8 phase (5Mg(OH) ₂ ·MgCl ₂ ·8H ₂ O, namely 5 phases) and 3·1·8 phase (3MgO·1MgCl ₂ ·8H ₂ O, namely 3 phases ) crystals, which play a role in pore filling and particle bonding, and promote the early strength improvement of sludge; Ca(OH) ₂ and Mg(OH) ₂ , as hydration products, can be combined with NaOH, sodium silicate and other activators to synergistically excite slag fly ash Potential active components of mineral materials, such as mineral materials, induce pozzolanic reactions to form cementation products such as calcium silicate hydrate CSH, magnesium silicate hydrate MSH and sodium aluminosilicate NASH, which can effectively ensure the long-term maintenance of the late strength of solidified silt and long-term stability; fly ash itself has a particle filling effect (80% of the particle size is silt, clay) and can also fill the pores between particles/agglomerates, playing a role in micro-filling and compacting; NaOH and sodium silicate can excite partial The aluminosilicate component in kaolin, through a series of chemical actions such as geopolymerization, forms sodium aluminosilicate hydrate NASH colloid and continues to harden and coagulate, which can effectively improve the long-term strength and long-term stability of solidified sludge. The mixture of dead-burned MgO and magnesium phosphate quickly undergoes acid-base neutralization reaction to form a kind of chemically bonded material of magnesium phosphate salt, which has the advantages of high early strength, fast coagulation speed, and short coagulation time; the synergistic cooperation of the above effects can effectively Greatly increase the compressive strength and durability of solidified silt.

Compared with the prior art, the present invention has the advantages of combining multiple reaction principles such as alkaline excitation, geopolymer polymerization, and calcium-magnesium-based gelling materials, fully utilizing bulk industrial waste materials such as slag and fly ash, Introduce green and low-carbon materials such as high-activity MgO, dead-burned MgO, magnesium chloride and magnesium phosphate, and achieve the macroscopic effect of water reduction and enhancement by adjusting the pH level, effectively promoting the hydration process and stimulating the active components of aluminosilicate minerals. , Improve the environmental friendliness of the cured material. The invention has the advantages of high early strength, good durability, stable late strength and sufficient compaction effect of the chemical reaction process, etc., and can be used in the fields of dredging silt, construction mud and soft ground treatment, etc., and the dredged silt after solidification treatment can be used as roadbed Filling and backfilling soil, etc.

Detailed ways

The specific implementations of the dredged sludge dehydration-solidified calcium-magnesium-based composite material involved in the present invention, its preparation method and application are described in detail below.

<Example 1>

In this embodiment one, the method for preparing the calcium-magnesium-based composite material for dehydration and solidification of dredged silt is as follows:

Weigh each component according to the proportion: resin SAP 0.5wt.%, cement 6wt.%, dead burnt MgO 8wt.%, magnesium phosphate 13wt.%, metakaolin 8wt.%, active MgO 8wt.%, magnesium chloride 10wt.%. , 3wt.% of quicklime, 3wt.% of sodium silicate, 5.5wt.% of sodium hydroxide, 20wt.% of slag powder, 15wt.% of fly ash; composite material.

Performance Testing:

Add 250kg of dehydration-solidified calcium-magnesium-based composite material to each cubic meter of sludge, and set the initial moisture content of the sludge to 120%. After uniform mixing of the sludge and dehydrated-solidified calcium-magnesium-based composite material, prepare a sample with a diameter of 50mm and a height of 100mm , demolded after 3 days of standard curing, and continued curing to 7 days and 28 days, and three parallel samples were used for unconfined compressive strength at each age. The average strength of the solidified sludge can reach 1.117MPa and 1.913MPa in the 7-day and 28-day curing ages, and the average moisture content can reach 50.3% and 36.9% in the 7-day and 28-day curing ages.

<Example 2>

In this embodiment two, the method for preparing the calcium-magnesium-based composite material for dehydration and solidification of dredged silt is as follows:

Weigh each component according to the proportion: resin SAP 0.5wt.%, cement 6wt.%, dead-burned MgO 8wt.%, magnesium phosphate 13wt.%, metakaolin 8wt.%, active MgO 6wt.%, magnesium chloride 10wt.%. , quicklime 3wt.%, sodium silicate 6wt.%, sodium hydroxide 4.5wt.%, slag powder 20wt.%, fly ash 15wt.%; composite material.

Performance Testing:

Add 250kg of dehydration-solidified calcium-magnesium-based composite material to each cubic meter of sludge, and set the initial moisture content of the sludge to 120%. After the sludge and dehydrated-solidified calcium-magnesium-based composite material are evenly stirred, a sample with a diameter of 50 mm and a height of 100 mm is prepared. The mold was removed after 3 days of standard curing, and the curing was continued to 7 days and 28 days. Three parallel samples were used for unconfined compressive strength at each age. The average strength of the solidified sludge can reach 1.043MPa and 1.722MPa in the 7-day and 28-day curing ages, and the average moisture content can reach 52.3% and 37.6% in the 7-day and 28-day curing ages.

<Example Three>

In this embodiment three, the method for preparing the calcium-magnesium-based composite material for dehydration and solidification of dredged silt is as follows:

Weigh each component according to the proportion: resin SAP 0.5wt.%, cement 6wt.%, dead-burned MgO 10.5wt.%, magnesium phosphate 15wt.%, metakaolin 8wt.%, active MgO 8wt.%, magnesium chloride 12wt. %, quicklime 2wt.%, sodium silicate 3wt.%, sodium hydroxide 3wt.%, slag powder 20wt.%, fly ash 12wt.%; then mix and mix evenly to get dredged silt dehydration solidified calcium magnesium base composite material.

Performance Testing:

Add 250kg of dehydration-solidified calcium-magnesium-based composite material to each cubic meter of sludge, and set the initial moisture content of the sludge to 120%. After the sludge and dehydrated-solidified calcium-magnesium-based composite material are evenly stirred, a sample with a diameter of 50 mm and a height of 100 mm is prepared. The mold was removed after 3 days of standard curing, and the curing was continued to 7 days and 28 days. Three parallel samples were used for unconfined compressive strength at each age. The average strength of solidified sludge can reach 1.342MPa and 2.133MPa in the 7-day and 28-day curing ages, and the average moisture content can reach 54.7% and 39.2% in the 7-day and 28-day curing ages.

<Example 4>

In this embodiment four, the method for preparing the calcium-magnesium-based composite material for dehydration and solidification of dredged silt is as follows:

Weigh each component according to the proportion: resin SAP 0.5wt.%, cement 6wt.%, dead burnt MgO 8wt.%, magnesium phosphate 10wt.%, metakaolin 6.5wt.%, active MgO 6wt.%, magnesium chloride 10wt. %, quicklime 2wt.%, sodium silicate 3wt.%, sodium hydroxide 3wt.%, slag powder 30wt.%, fly ash 15wt.%; then mixed and evenly mixed to obtain dredged silt dehydration solidified calcium magnesium base composite material.

Performance Testing:

Add 250kg of dehydration-solidified calcium-magnesium-based composite material to each cubic meter of sludge, and set the initial moisture content of the sludge to 120%. After the sludge and dehydrated-solidified calcium-magnesium-based composite material are evenly stirred, a sample with a diameter of 50 mm and a height of 100 mm is prepared. The mold was removed after 3 days of standard curing, and the curing was continued to 7 days and 28 days. Three parallel samples were used for unconfined compressive strength at each age. The average strength of the solidified sludge can reach 1.488MPa and 2.341MPa in the 7-day and 28-day curing ages, and the average moisture content in the 7-day and 28-day curing ages can reach 45.5% and 28.4%.

<Embodiment 5>

In this embodiment five, the method for preparing the calcium-magnesium-based composite material for dehydration and solidification of dredged silt is as follows:

Weigh each component according to the proportion: resin SAP 1wt.%, cement 6wt.%, dead burnt MgO 8wt.%, magnesium phosphate 12wt.%, metakaolin 12wt.%, active MgO 8wt.%, magnesium chloride 10wt.%, quicklime 3wt.%, sodium silicate 3wt.%, sodium hydroxide 3wt.%, slag powder 24wt.%, fly ash 10wt.%, and then mixed and evenly mixed to obtain dredged silt dehydration solidified calcium magnesium matrix composite material.

Performance Testing:

Add 250kg of dehydration-solidified calcium-magnesium-based composite material to each cubic meter of sludge, and set the initial moisture content of the sludge to 120%. After the sludge and dehydrated-solidified calcium-magnesium-based composite material are evenly stirred, a sample with a diameter of 50 mm and a height of 100 mm is prepared. The mold was removed after 3 days of standard curing, and the curing was continued to 7 days and 28 days. Three parallel samples were used for unconfined compressive strength at each age. The average strength of the solidified sludge can reach 1.247MPa and 1.996MPa in the 7-day and 28-day curing ages, and the average moisture content can reach 53.7% and 32.4% in the 7-day and 28-day curing ages.

In the above examples, the superabsorbent resin SAP used is white and granular in appearance, and its main components are low-crosslinking sodium polyacrylate (accounting for 88wt.%) and crosslinking agent (accounting for 0.75wt.%) , fineness is 200-400 mesh; slag powder is granulated blast furnace slag powder, Al ₂ O ₃ +SiO ₂ +CaO content ≥ 90wt.%; magnesium phosphate is analytically pure, MgPO ₄ content ≥ 95wt.%; fly ash It is secondary fly ash; magnesium chloride is analytically pure, MgCl ₂ 6H ₂ O content ≥ 98wt.%; cement is ordinary Portland cement; magnesium oxide is highly active magnesium oxide, and MgO content ≥ 90wt.%; hydrogen Sodium oxide is dry powder, NaOH content ≥ 99wt.%; quicklime is dry powder, CaO content ≥ 95wt.%; Al ₂ O ₃ + SiO ₂ content ≥ 70wt.% and CaO content < 10wt.% in fly ash.

In summary, the present invention comprehensively utilizes the reaction principles of alkaline excitation, geopolymer polymerization, and calcium-magnesium-based cementitious materials, and fully utilizes industrial by-products such as slag powder and fly ash by adjusting the amount of components added and the distribution ratio of components. The material contains only a small amount of cement and lime, which effectively overcomes the shortcomings of traditional solidified materials. The invention has the advantages of good early strength performance, fast coagulation and hardening speed, good long-term stability and good durability, and can obviously solve the problems of high moisture content, high compressibility and low shear strength of sludge, and convert waste dredging sludge into Recycling geotechnical fillers can achieve good curing effect and economic effect.

In addition, the above embodiments are only illustrations for the technical solution of the present invention. The calcium-magnesium-based composite material for dehydration and solidification of dredged sludge involved in the present invention is not limited to the content described in the above embodiments, but is subject to the scope defined in the claims. Any modifications, supplements or equivalent replacements made by those skilled in the art of the present invention on the basis of the embodiments are within the protection scope of the claims of the present invention.

Claims (10)

1. A dredged silt dewatering solidified calcium-magnesium-based composite material, characterized in that, in dry powder terms, comprising the following components: Resin SAP: 0.25～1wt.%, Cement: 6～12wt.%, Dead burnt MgO: 6～15wt.%, Magnesium phosphate: 8～22wt.%, Metakaolin: 6～18wt.%, Active MgO: 6～ 15wt.%, magnesium chloride: 10~25wt.%, quicklime: 2~4wt.%, sodium silicate: 3~8wt.%, sodium hydroxide: 3~6wt.%, slag powder: 15~40wt.%, powder Coal ash: 10-30wt.%. 2. dredging silt dehydration solidified calcium-magnesium matrix composite material according to claim 1, is characterized in that: Wherein, the active magnesium oxide is highly active MgO, and the content of MgO is more than or equal to 92wt.%. 3. the dredged silt dehydration solidified calcium magnesium matrix composite material according to claim 1, is characterized in that: Wherein, the dead-burned magnesium oxide is MgO with low activity, the burning temperature is >1200°C, and the MgO content is ≥94wt.%. 4. the dredged silt dehydration solidified calcium magnesium matrix composite material according to claim 1, is characterized in that: Wherein, the magnesium chloride is analytically pure, and the content of MgCl ₂ ·6H ₂ O is ≥98wt.%. 5. the dredged silt dehydration solidified calcium magnesium matrix composite material according to claim 1, is characterized in that: Wherein, the magnesium phosphate is analytically pure, and the MgPO ₄ content is more than or equal to 95wt.%. 6. the dredged silt dehydration solidified calcium magnesium matrix composite material according to claim 1, is characterized in that: Wherein, the CaO content in the quicklime is ≥95wt.%. 7. The dredged silt dehydration solidified calcium-magnesium matrix composite material according to claim 1, characterized in that: Wherein, the sodium silicate is a dry powder sample, and the Na ₂ SiO ₃ content is ≥99wt.%. 8. The dredged silt dehydration solidified calcium-magnesium matrix composite material according to claim 1, characterized in that: Wherein, in the fly ash, the sum of the mass percentages of Al ₂ O ₃ and SiO ₂ is ≥70wt.%, and the content of CaO is not limited. 9. A method for preparing dredged silt dehydration solidified calcium-magnesium-based composite material, characterized in that, comprising: Weigh each component according to the ratio, resin SAP: 0.25~1wt.%, cement: 6~12wt.%, dead-burned MgO: 6~15wt.%, magnesium phosphate: 8~22wt.%, metakaolin: 6~ 18wt.%, active MgO: 6~15wt.%, magnesium chloride: 10~25wt.%, quicklime: 2~4wt.%, sodium silicate: 3~8wt.%, sodium hydroxide: 3~6wt.%, slag powder: 15-40wt.%, and fly ash: 10-30wt.%, and then mixed and uniformly mixed to obtain the dehydrated and solidified calcium-magnesium matrix composite material of dredged silt. 10. Application of the dredged silt dehydration-solidified calcium-magnesium-based composite material according to any one of claims 1 to 8 in soft soil foundation and construction mud reinforcement.