阅读说明：本技术 一种高活性低温稻壳灰及掺有该稻壳灰的高性能混凝土 (High-activity low-temperature rice hull ash and high-performance concrete doped with same ) 是由 戎志丹 陈浩 于 2020-11-11 设计创作，主要内容包括：本发明公开一种高活性低温稻壳灰及掺有该稻壳灰的高性能混凝土。该活性低温稻壳灰由如下方法制得：将稻壳在1％的盐酸中沸水浴1h,水洗后再晒干,除去其中杂质；将预处理完的稻壳在炉内600～700℃下烧制30～60min,随后冷却；将烧制后的稻壳灰在500～800转/分钟的球磨机中球磨10～30min,得到SiO-2含量超过90wt％的高活性低温稻壳灰。掺有该高活性低温稻壳灰的高性能混凝土,由如下重量百分含量的原料组成：硅酸盐水泥15％～20％,高活性低温稻壳灰5％～10％,粉煤灰10％～15％,河砂20％～30％,玄武岩石子25％～35％,水6％～12％,减水剂0.4％～1％。本发明的稻壳灰具有高纯度和高活性,可有效替代硅灰作为矿物掺合料,制备的高性能混凝土力学性能优异,提高稻壳利用率的同时大大降低了水泥用量,降低了混凝土成本。(The invention discloses high-activity low-temperature rice hull ash and high-performance concrete doped with the same. The active low-temperature rice hull ash is prepared by the following method: putting the rice hull in 1% hydrochloric acid, boiling in water bath for 1h, washing with water, and drying in the sun to remove impurities; firing the pretreated rice hulls in a furnace at 600-700 ℃ for 30-60 min, and then cooling; ball-milling the fired rice hull ash in a ball mill at 500-800 r/min for 10-30 min to obtain SiO 2 High activity low temperature rice hull ash with a content of more than 90 wt%. The high-performance concrete doped with the high-activity low-temperature rice hull ash comprises the following raw materials in percentage by weight: 15 to 20 percent of Portland cement, 5 to 10 percent of high-activity low-temperature rice hull ash and pulverized coal10 to 15 percent of ash, 20 to 30 percent of river sand, 25 to 35 percent of basalt stone, 6 to 12 percent of water and 0.4 to 1 percent of water reducing agent. The rice hull ash disclosed by the invention has high purity and high activity, can effectively replace silica fume to be used as a mineral admixture, and the prepared high-performance concrete has excellent mechanical property, the utilization rate of rice hulls is improved, the cement consumption is greatly reduced, and the concrete cost is reduced.)

1. The high-activity low-temperature rice hull ash is characterized by being prepared by the following method:

(1) pretreatment: putting the rice hulls in 0.5-1.5% hydrochloric acid for 45-90 min in a boiling water bath, washing with water, and then drying in the sun to remove impurities;

(2) firing: firing the pretreated rice hulls in a furnace at 600-700 ℃ for 30-60 min, and then cooling;

(3) grinding: ball-milling the fired rice hull ash in a ball mill with 500-800 r/min for 10-30 min to obtain the high-activity low-temperature rice hull ash, wherein the high-activity low-temperature rice hull ash contains more than 90 wt% of SiO₂。

2. The high-performance concrete doped with the high-activity low-temperature rice hull ash of claim 1, which is characterized by comprising the following raw materials in percentage by weight:

3. the high performance concrete of claim 2, wherein the cement is portland cement or portland cement of strength grade 52.5.

4. The high performance concrete of claim 2, wherein the fly ash isThe grade I fly ash has a water requirement ratio of less than or equal to 95 percent, a loss on ignition of less than or equal to 5 percent and a specific surface area of more than or equal to 400m²/kg。

5. The high-performance concrete of claim 2, wherein the river sand is common river sand with continuous gradation and a maximum particle size of 5 mm.

6. The high performance concrete of claim 2, wherein the basalt pebbles are of continuous grading with a maximum grain size of 20 mm.

7. The high-performance concrete of claim 2, wherein the water reducing agent is a polycarboxylic acid water reducing agent with a solid content of more than 30%.

Technical Field

The invention relates to high-performance low-temperature rice hull ash and high-performance concrete doped with the same, and belongs to the technical field of building materials.

Background

With the rapid development of global economy and the continuous promotion of large-scale infrastructure engineering, more and more requirements are put on the strength, toughness, safety and durability of concrete building materials. The high-performance concrete material is more and more widely applied to projects such as high-rise, large-span, ocean, protection, severe environment and the like due to excellent mechanical property, durability, safety and reliability. The requirement for high-performance concrete in building engineering is increasing day by day, and in the aspect of concrete performance regulation and control, the requirements for reducing porosity, optimizing pore structure and improving compactness are continuously met, wherein a high-activity mineral admixture is doped into a cement-based material, and the improvement of the microstructure of cement paste and the optimization of pore structure from a microscopic angle so as to improve the mechanical property of the high-performance concrete is an effective technical approach and is also a current research hotspot.

The concrete science and engineering world at present has fully realized that mineral admixtures such as fly ash, silica fume, ground slag and the like are indispensable components for preparing high-performance concrete, are important measures for saving energy, saving resources and protecting ecological environment, and are well recognized for replacing cement clinker in important and important engineering construction. At present, high-quality fly ash and ground slag micro powder still cannot meet the engineering requirements despite the increase of the yield in years, and the situation of short supply and demand appears, even the II-grade ash is used for filling the dosage. Researchers find that other mineral admixtures such as rice hull ash, metakaolin, red mud, tailing powder, rice straw ash, power plant ash and other waste residues produced in industrial or agricultural production in large quantity are rich in different varieties of micro-scale active substances, and the substances can also exert the particle property and high activity when being doped into the ultra-high performance cement-based material, so that the mechanical property and durability of the cement-based material are improved.

In the mineral admixture, the rice hull ash is an ecological material which can partially replace silica fume. The rice hull ash is agricultural waste and is a product of rice hulls after combustion, and the waste is accumulated in the atmosphere, so that the rice hull ash not only occupies farmlands, but also causes serious environmental pollution, and becomes a serious threat to social sustainable development. All over the world each yearThe produced rice is about 7 hundred million and more tons, the mass of the rice hulls accounts for about 20 percent, and the rice hull ash produced by completely burning the rice hulls under certain conditions can contain 90 to 96 percent of amorphous SiO₂Therefore, the rice husk ash is also a pozzolan admixture with high activity similar to silica fume. SiO of rice husk itself₂The content is low, modification treatment is generally needed to increase the silicon content, however, the existing modification treatment method is generally complicated, and SiO is treated₂The content is usually about 70%, a certain amount of impurities such as organic matters, metal elements and the like still exist, and the purity and the activity are relatively low.

Therefore, how to obtain the high-purity and high-activity rice hull ash so as to fully play the reinforcing effect in the cement-based material is an urgent problem to be solved.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the problems that the existing rice hull ash has low purity and activity and cannot effectively enhance the performance of a cement-based material, the invention provides high-activity low-temperature rice hull ash and high-performance concrete doped with the rice hull ash.

The technical scheme is as follows: the invention relates to high-activity low-temperature rice hull ash which is prepared by the following method:

(1) pretreatment: putting the rice hulls in 0.5-1.5% hydrochloric acid for 45-90 min in a boiling water bath, washing with water, and then drying in the sun to remove impurities;

(2) firing: firing the pretreated rice hulls in a furnace at 600-700 ℃ for 30-60 min, and then cooling;

(3) grinding: ball-milling the fired rice hull ash in a ball mill with 500-800 r/min for 10-30 min to obtain the high-activity low-temperature rice hull ash, wherein the high-activity low-temperature rice hull ash contains more than 90 wt% of SiO₂。

The high-performance concrete doped with the high-activity low-temperature rice hull ash comprises the following raw materials in percentage by weight:

and weighing the portland cement, the high-activity low-temperature rice hull ash, the fly ash, the river sand, the basalt stone, the water and the water reducing agent according to the weight ratio, putting the materials into a concrete mixer, and mechanically and uniformly mixing to obtain the high-performance concrete.

Wherein the portland cement can be portland cement with a strength grade of 52.5 or ordinary portland cement.

The fly ash is preferably I-class fly ash, the water requirement ratio of the fly ash is less than or equal to 95 percent, the ignition loss is less than or equal to 5 percent, and the specific surface area is more than or equal to 400m²/kg。

Preferably, the river sand is common river sand with continuous gradation and the maximum grain size of 5 mm. The basalt pebbles are in continuous gradation, and the maximum grain size is 20 mm.

The water reducing agent is preferably a polycarboxylic acid water reducing agent with the solid content of more than 30 percent.

Has the advantages that: compared with the prior art, the invention has the advantages that: (1) the rice hull ash is prepared by burning and grinding rice hulls at low temperature (600-700 ℃), and SiO₂The content is more than 90 wt%, and the high-purity high-pozzolanic-activity volcanic ash has high purity; moreover, the treatment process is simple, easy to operate, low in cost, green and environment-friendly, and easy for industrial production; (2) because the rice hull ash has high activity, the rice hull ash can effectively replace silica fume to be used as a mineral admixture to be doped into a cement-based material, the prepared high-performance concrete has the advantages of fast strength development, high strength, good workability, good volume stability and high durability, and the strength of the prepared high-performance concrete is even higher than that of the existing silica fume-doped concrete; (3) the rice hull ash disclosed by the invention is doped into the cement-based material, so that the cement consumption can be saved, the cost is reduced, the utilization rate of the rice hulls is improved, the comprehensive utilization of the rice hulls is realized, and the rice hull ash is ecological and environment-friendly; in addition, the rice hull which is agricultural waste has sufficient sources and can meet the large-scale market demand.

Drawings

FIG. 1 is a 28d TG-DSC curve of the high-activity low-temperature rice hull ash prepared in example 1;

FIG. 2 is a 28d TG-DSC curve of silica fume.

Detailed Description

The technical solution of the present invention is further explained below.

Example 1

Preparing high-activity low-temperature rice hull ash:

(1) pretreatment: putting rice hull in 1% hydrochloric acid, boiling in water bath for 60min, washing with water, and sun drying to remove impurities;

(2) firing: firing the pretreated rice hulls in a furnace at 650 ℃ for 60min, and then cooling;

(3) grinding: and ball-milling the fired rice hull ash in a ball mill at 700 r/min for 30min to obtain the high-activity low-temperature rice hull ash.

The chemical composition of the high activity low temperature rice hull ash prepared by X-ray fluorescence spectroscopy (XRF) analysis, as shown in Table 1 below, shows that the high activity low temperature rice hull ash prepared contains more than 95 wt% SiO₂。

Table 1 chemical composition of high activity low temperature rice hull ash prepared in example 1

The high-activity low-temperature rice hull ash prepared by adopting a DSC/TG thermal analysis method is analyzed, and the activity index of the high-activity low-temperature rice hull ash is calculated according to an activity calculation method, as shown in the following table 2, and by combining with figures 1-2, the rice hull ash prepared by the invention has obviously higher activity compared with silica fume.

TABLE 2 Rice Hull Ash and silica Ash Activity index

The high-activity low-temperature rice hull ash prepared by the method is used as a raw material to prepare the high-performance concrete with the following component contents:

and weighing the portland cement, the high-activity low-temperature rice hull ash, the fly ash, the river sand, the basalt stone, the water and the water reducing agent according to the weight ratio, putting the materials into a concrete mixer, and mechanically and uniformly mixing to obtain the high-performance concrete. The compressive strength of the concrete is (28d)106.3MPa according to GB/T50081-2019 'test method Standard of physical and mechanical Properties of concrete'.

Example 2

Preparing high-activity low-temperature rice hull ash:

(1) pretreatment: putting rice hull in 0.5% hydrochloric acid, boiling in water bath for 45min, washing with water, and sun drying to remove impurities;

(2) firing: firing the pretreated rice hulls in a furnace at 600 ℃ for 30min, and then cooling;

(3) grinding: and ball-milling the fired rice hull ash in a ball mill at 500 r/min for 10min to obtain the high-activity low-temperature rice hull ash.

The high activity low temperature rice hull ash obtained in this example contains more than 90 wt% SiO as analyzed by X-ray fluorescence spectroscopy (XRF)₂. The activity index of the rice hull ash is analyzed and calculated by a DSC/TG thermal analysis method, and the rice hull ash has higher activity compared with silica ash.

The prepared high-activity low-temperature rice hull ash is used as a raw material to prepare high-performance concrete with the following component contents:

and weighing the portland cement, the high-activity low-temperature rice hull ash, the fly ash, the river sand, the basalt stone, the water and the water reducing agent according to the weight ratio, putting the materials into a concrete mixer, and mechanically and uniformly mixing to obtain the high-performance concrete. The compressive strength of the concrete is (28d)92.3MPa according to GB/T50081-2019 test method Standard for physical and mechanical Properties of concrete.

Example 3

Preparing high-activity low-temperature rice hull ash:

(1) pretreatment: putting rice hull in 1% hydrochloric acid, boiling in water bath for 90min, washing with water, and sun drying to remove impurities;

(2) firing: firing the pretreated rice hulls in a furnace at 700 ℃ for 60min, and then cooling;

(3) grinding: and ball-milling the fired rice hull ash in a 600 r/min ball mill for 20min to obtain the high-activity low-temperature rice hull ash.

The high activity low temperature rice hull ash obtained in this example contains more than 90 wt% SiO as analyzed by X-ray fluorescence spectroscopy (XRF)₂. The activity index of the rice hull ash is analyzed and calculated by a DSC/TG thermal analysis method, and the rice hull ash has higher activity compared with silica ash.

The prepared high-activity low-temperature rice hull ash is used as a raw material to prepare high-performance concrete with the following component contents:

and weighing the portland cement, the high-activity low-temperature rice hull ash, the fly ash, the river sand, the basalt stone, the water and the water reducing agent according to the weight ratio, putting the materials into a concrete mixer, and mechanically and uniformly mixing to obtain the high-performance concrete. The compressive strength (28d) is measured to be 95.6MPa according to GB/T50081-2019 concrete physical and mechanical property test method Standard.

Example 4

Preparing high-activity low-temperature rice hull ash:

(1) pretreatment: putting rice hull in 1.5% hydrochloric acid, boiling in water bath for 90min, washing with water, and sun drying to remove impurities;

(2) firing: firing the pretreated rice hulls in a furnace at 800 ℃ for 45min, and then cooling;

(3) grinding: and ball-milling the fired rice hull ash in a ball mill at 800 r/min for 30min to obtain the high-activity low-temperature rice hull ash.

Fluorescence by X-rayThe high activity low temperature rice hull ash obtained in this example contains more than 90 wt% SiO by optical spectrum (XRF) analysis₂. The activity index of the rice hull ash is analyzed and calculated by a DSC/TG thermal analysis method, and the rice hull ash has higher activity compared with silica ash.

The prepared high-activity low-temperature rice hull ash is used as a raw material to prepare high-performance concrete with the following component contents:

and weighing the portland cement, the high-activity low-temperature rice hull ash, the fly ash, the river sand, the basalt stone, the water and the water reducing agent according to the weight ratio, putting the materials into a concrete mixer, and mechanically and uniformly mixing to obtain the high-performance concrete. The compressive strength (28d) is 84.7MPa according to GB/T50081-2019 concrete physical and mechanical property test method Standard.

Example 5

Preparing high-activity low-temperature rice hull ash:

(1) pretreatment: putting rice hull in 1% hydrochloric acid, boiling in water bath for 60min, washing with water, and sun drying to remove impurities;

(2) firing: firing the pretreated rice hulls in a furnace at 650 ℃ for 60min, and then cooling;

(3) grinding: and ball-milling the fired rice hull ash in a ball mill at 800 r/min for 20min to obtain the high-activity low-temperature rice hull ash.

The high activity low temperature rice hull ash obtained in this example contains more than 90 wt% SiO as analyzed by X-ray fluorescence spectroscopy (XRF)₂. The activity index of the rice hull ash is analyzed and calculated by a DSC/TG thermal analysis method, and the rice hull ash has higher activity compared with silica ash.

The prepared high-activity low-temperature rice hull ash is used as a raw material to prepare high-performance concrete with the following component contents:

and weighing the portland cement, the high-activity low-temperature rice hull ash, the fly ash, the river sand, the basalt stone, the water and the water reducing agent according to the weight ratio, putting the materials into a concrete mixer, and mechanically and uniformly mixing to obtain the high-performance concrete. The compressive strength (28d) is 121.8MPa according to GB/T50081-2019 concrete physical and mechanical property test method Standard.