1. The composite building material with sea sand as aggregate is characterized by comprising the following raw materials in parts by weight: 70-90 parts of sea sand, 20-30 parts of fly ash, 70-100 parts of light-burned magnesium oxide, 60-100 parts of magnesium sulfate solution, 1-2 parts of defoaming agent, 3-5 parts of water reducing agent, 3-8 parts of composite modifier and 20-35 parts of water.

2. The composite building material with sea sand as aggregate of claim 1, wherein the composite modifier consists of 50-70wt% of phosphogypsum, 20-30wt% of water glass, 3-5wt% of sodium gluconate and 5-15wt% of silane coupling agent.

3. The composite building material using sea sand as aggregate according to any one of claims 1 to 2, wherein the content of active magnesium oxide in the lightly calcined magnesium oxide is 50 to 70 wt%; the magnesium sulfate solution has a density of 1.2-1.24g/cm³Aqueous magnesium sulfate solution.

4. The composite building material with sea sand as aggregate according to any one of claims 1 to 2, wherein the defoaming agent is emulsified glycerin; the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent; the silane coupling agent is KH550 or KH 570.

5. The method for preparing a composite construction material with sea sand as aggregate according to any one of claims 1 to 4, comprising the steps of:

(1) weighing the raw materials according to the weight ratio for later use;

(2) preparing a composite modifier, adding the composite modifier into a magnesium sulfate solution, adding a defoaming agent, and uniformly stirring to obtain a mixed solution a;

(3) adding light-burned magnesium oxide into the mixed solution a, and uniformly stirring to obtain a mixed solution b;

(4) mixing and fully stirring the sea sand, the fly ash, the mixed solution b, the water reducing agent and water to obtain composite building material slurry;

(5) pouring the composite building material slurry into a mold, molding, curing for 24 hours, demolding, and then naturally curing to obtain the composite building material.

Background

Sea sand refers to sand eroded by seawater without desalination treatment, and is mostly from the boundary between seawater and rivers.

In the total production of sea sand, 90% or more of the total production is used as a sand making machine building and civil engineering material, and 45% or more of the total production is used as a concrete fine aggregate. In addition, about 20% of sea sand is used for paving the roadbed, about 20% of filler used for filling the sea and making land, and the rest 15% is used for asphalt concrete.

CN108409283A is an early study of the applicant, which takes sea sand as aggregate and magnesium oxychloride cement as main cementing material to obtain the composite building material. The magnesium oxychloride cement is a gelled material with air hardening property, which is formed by mixing light-burned magnesium oxide and magnesium chloride solution, and has the characteristics of high early strength, light weight, good fire resistance and the like, but has the defects of poor water resistance, high setting speed and the like. Although CN108409283A added with the modifier improves the defect of poor water resistance to a certain extent, the defects of high coagulation speed, insufficient strength and the like still exist.

Magnesium oxysulfate cement is an inorganic cementitious material prepared by mixing magnesium sulfate solution with light-burned magnesium oxide (MgO) powder. Compared with magnesium oxychloride cement, the magnesium oxychloride cement has the advantages of light weight, fire resistance, impact resistance and the like, and overcomes the defects of poor water resistance, moisture absorption, halogen regain and the like. But its strength is lower and at the same time it coagulates faster.

Disclosure of Invention

In order to solve the technical problem, the invention discloses a composite building material with sea sand as aggregate, which comprises the following raw materials in parts by weight: 70-90 parts of sea sand, 20-30 parts of fly ash, 70-100 parts of light-burned magnesium oxide, 60-100 parts of magnesium sulfate solution, 1-2 parts of defoaming agent, 3-5 parts of water reducing agent, 3-8 parts of composite modifier and 20-35 parts of water.

Wherein the composite modifier consists of 50-70wt% of phosphogypsum, 20-30wt% of water glass, 3-5wt% of sodium gluconate and 5-15wt% of silane coupling agent.

Preferably, the content of active magnesium oxide in the light-burned magnesium oxide is 50 to 70 wt%; the magnesium sulfate solution has a density of 1.2-1.24g/cm³Aqueous magnesium sulfate solution.

Preferably, the defoaming agent is emulsified glycerol; the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent.

Preferably, the silane coupling agent is KH550 or KH 570.

Meanwhile, the invention discloses a preparation method of the composite building material, which comprises the following steps:

(1) weighing the raw materials according to the weight ratio for later use;

(2) preparing a composite modifier, adding the composite modifier into a magnesium sulfate solution, adding a defoaming agent, and uniformly stirring to obtain a mixed solution a;

(3) adding light-burned magnesium oxide into the mixed solution a, and uniformly stirring to obtain a mixed solution b;

(4) mixing and fully stirring the sea sand, the fly ash, the mixed solution b, the water reducing agent and water to obtain composite building material slurry;

(5) pouring the composite building material slurry into a mold, molding, curing for 24 hours, demolding, and then naturally curing to obtain the composite building material.

Phosphogypsum is a solid waste discharged during the production of phosphate fertilizer and phosphoric acid, and the main component of the phosphogypsum is dihydrate gypsum. Besides the main component calcium sulfate, the phosphogypsum also contains a small amount of phosphoric acid, silicon, magnesium, iron, aluminum, organic impurities and the like. The calcium sulfate can be used as the water-resistant modifier of the magnesia cement, and the phosphoric acid or the salt thereof is not only the traditional water-resistant modifier of the magnesia cement, but also a common cement retarder. The water glass is a common inorganic cementing material, has the advantages of high bonding strength, high compressive strength and the like, and has the function of blocking capillary pores after being hardened, so that the water resistance is improved. The sodium gluconate is a commonly used retarder and can delay the setting time of concrete and improve the strength of concrete products. The addition of the silane coupling agent can improve water resistance and adhesive strength. Through detection, the 7d compressive strength of the composite building material is 15-20MPa, and the 28d compressive strength is 60-70 MPa. The initial setting time is 230-270min, and the final setting time is 330-380 min. The invention takes sea sand as aggregate and magnesium oxysulfate cement as main cementing material. Meanwhile, the kind of the composite modifier is reasonably selected and the dosage of the composite modifier is reasonably adjusted, and finally the composite building material with high strength, adjustable setting time and good water resistance is obtained.

Detailed Description

The present invention is further illustrated by the following examples, but is not limited to the details of the description.

Example 1

A composite building material with sea sand as aggregate comprises the following raw materials in parts by weight: 75 parts of sea sand, 20 parts of fly ash, 70 parts of light-burned magnesium oxide, 65 parts of magnesium sulfate solution, 1 part of defoaming agent, 3 parts of water reducing agent, 3 parts of composite modifier and 20 parts of water. WhereinThe composite modifier consists of 55wt% of phosphogypsum, 30wt% of water glass, 3wt% of sodium gluconate and 12wt% of silane coupling agent. Wherein the content of active magnesium oxide in the light-burned magnesium oxide is 50 wt%; the magnesium sulfate solution had a density of 1.2g/cm³Aqueous magnesium sulfate solution. The defoaming agent is emulsified glycerol; the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent. The silane coupling agent is KH 550.

The preparation method of the composite building material comprises the following steps:

(1) weighing the raw materials according to the weight ratio for later use;

(2) preparing a composite modifier, adding the composite modifier into a magnesium sulfate solution, adding a defoaming agent, and uniformly stirring to obtain a mixed solution a;

(3) adding light-burned magnesium oxide into the mixed solution a, and uniformly stirring to obtain a mixed solution b;

(4) mixing and fully stirring the sea sand, the fly ash, the mixed solution b, the water reducing agent and water to obtain composite building material slurry;

(5) pouring the composite building material slurry into a mold, molding, curing for 24 hours, demolding, and then naturally curing to obtain the composite building material.

The detection proves that the 7d compressive strength is 15.4MPa, and the 28d compressive strength is 63.7 MPa. The initial setting time is 235min, and the final setting time is 340 min.

Example 2

A composite building material with sea sand as aggregate comprises the following raw materials in parts by weight: 80 parts of sea sand, 25 parts of fly ash, 90 parts of light-burned magnesium oxide, 85 parts of magnesium sulfate solution, 1.5 parts of defoaming agent, 3.5 parts of water reducing agent, 6 parts of composite modifier and 25 parts of water. Wherein the composite modifier consists of 60wt% of phosphogypsum, 25wt% of water glass, 4wt% of sodium gluconate and 11wt% of silane coupling agent. Wherein the content of active magnesium oxide in the light-burned magnesium oxide is 55 wt%; the magnesium sulfate solution had a density of 1.22g/cm³Aqueous magnesium sulfate solution. The defoaming agent is emulsified glycerol; the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent. The silane coupling agent is KH 550.

The preparation method of the composite building material comprises the following steps:

(1) weighing the raw materials according to the weight ratio for later use;

(2) preparing a composite modifier, adding the composite modifier into a magnesium sulfate solution, adding a defoaming agent, and uniformly stirring to obtain a mixed solution a;

(3) adding light-burned magnesium oxide into the mixed solution a, and uniformly stirring to obtain a mixed solution b;

(4) mixing and fully stirring the sea sand, the fly ash, the mixed solution b, the water reducing agent and water to obtain composite building material slurry;

(5) pouring the composite building material slurry into a mold, molding, curing for 24 hours, demolding, and then naturally curing to obtain the composite building material.

The detection proves that the 7d compressive strength is 17.7MPa, and the 28d compressive strength is 68.5 MPa. The initial setting time is 262min, and the final setting time is 368 min.

Example 3

A composite building material with sea sand as aggregate comprises the following raw materials in parts by weight: 90 parts of sea sand, 30 parts of fly ash, 100 parts of light-burned magnesium oxide, 95 parts of magnesium sulfate solution, 2 parts of defoaming agent, 5 parts of water reducing agent, 8 parts of composite modifier and 30 parts of water. Wherein the composite modifier consists of 70wt% of phosphogypsum, 20wt% of water glass, 5wt% of sodium gluconate and 5wt% of silane coupling agent. Wherein the content of active magnesium oxide in the light-burned magnesium oxide is 65 wt%; the magnesium sulfate solution had a density of 1.24g/cm³Aqueous magnesium sulfate solution. The defoaming agent is emulsified glycerol; the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent. The silane coupling agent is KH 570.

The preparation method of the composite building material comprises the following steps:

(1) weighing the raw materials according to the weight ratio for later use;

(2) preparing a composite modifier, adding the composite modifier into a magnesium sulfate solution, adding a defoaming agent, and uniformly stirring to obtain a mixed solution a;

(3) adding light-burned magnesium oxide into the mixed solution a, and uniformly stirring to obtain a mixed solution b;

(4) mixing and fully stirring the sea sand, the fly ash, the mixed solution b, the water reducing agent and water to obtain composite building material slurry;

(5) pouring the composite building material slurry into a mold, molding, curing for 24 hours, demolding, and then naturally curing to obtain the composite building material.

The detection proves that the 7d compressive strength is 16.1MPa, and the 28d compressive strength is 64.9 MPa. The initial setting time was 248min and the final setting time was 359 min.

Comparative example 1

CN108409283A composite building material prepared in example 5. The detection proves that the 7d compressive strength is 11.5MPa, and the 28d compressive strength is 53.6 MPa. The initial setting time is 54min, and the final setting time is 122 min.

Comparative example 2

The procedure of example 1 was repeated except that the composite modifier was not added. The detection proves that the 7d compressive strength is 5.1MPa, and the 28d compressive strength is 30.4 MPa. The initial setting time is 12min, and the final setting time is 53 min.

Comparative example 3

The composite modifier consists of 100wt% phosphogypsum, and the rest is the same as the example 1. The detection proves that the 7d compressive strength is 8.2MPa, and the 28d compressive strength is 39.1 MPa. The initial setting time is 37min, and the final setting time is 78 min.

Comparative example 4

The composite modifier consists of 70wt% of phosphogypsum and 30wt% of water glass, and the rest is the same as the embodiment 1. The detection proves that the 7d compressive strength is 10.9MPa, and the 28d compressive strength is 51.5 MPa. The initial setting time is 29min, and the final setting time is 67 min.

Comparative example 5

The composite modifier consists of 70wt% of phosphogypsum, 25wt% of water glass and 5wt% of sodium gluconate, and the rest is the same as that in the embodiment 1. The detection proves that the 7d compressive strength is 12.4MPa, and the 28d compressive strength is 59.5 MPa. The initial setting time is 215min, and the final setting time is 310 min.

As can be seen from the above examples and comparative examples, the composite building material using sea sand as aggregate prepared by the invention has the compressive strength of 15-20MPa in 7d and 60-70MPa in 28 d. The initial setting time is 230-270min, and the final setting time is 330-380 min. The type and the dosage of the composite modifier have important influence on the properties of the composite building material, such as strength, setting time and the like. By reasonably selecting the type and the dosage of the composite building material, the composite building material with high strength, adjustable setting time and good water resistance is obtained.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. Not all embodiments are exhaustive. All obvious changes and modifications which are obvious to the technical scheme of the invention are covered by the protection scope of the invention.