CN114634338A - High-ductility cement-based composite material for wind-blown sand in desert and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of civil engineering building materials, and discloses a desert aeolian sand high ductility cement-based composite material and a preparation method thereof. The composite material is composed of the following raw materials in parts by weight: 1.0 part of cement, 0.1 part of desert aeolian sand ‑3 parts, fly ash 0.1‑4 parts, silica fume 0‑0.9 parts, rubber powder 0.0005‑0.004 parts, water reducing agent accounting for 0.2‑1% by weight of cement raw materials, fiber volume ratio 0‑3%, water The glue ratio is 0.32‑0.38. The invention completely replaces traditional river sand with desert aeolian sand, and replaces part of cement with fly ash and silica fume, "turns waste into treasure", does not contain coarse aggregate, does not need a large amount of additives, and does not need to modify materials , without any treatment such as washing the aeolian sand, adding fibers, and using a simple and easy-to-implement preparation process, a high-ductility cement-based composite material with good mechanical properties can be prepared, which can effectively improve the traditional concrete. The defects of poor toughness and easy cracking can also alleviate the contradiction between supply and demand of building materials, reduce project costs and protect the environment.

Description

A kind of desert aeolian sand high ductility cement-based composite material and preparation method thereof

technical field

The invention belongs to the technical field of civil engineering building materials, and particularly relates to a desert aeolian sand high-ductility cement-based composite material and a preparation method thereof.

Background technique

Concrete, as the most widely used material in building structures, has the advantages of low price and simple preparation process. However, ordinary concrete has the disadvantages of low tensile strength, small tensile deformation, brittle texture and difficult to control cracks after cracking. At the same time, with the increasing demand for building performance in engineering, ordinary concrete is increasingly unable to meet the requirements of modern engineering structures. How to improve the performance of concrete is one of the problems to be solved urgently.

The above shortcomings of concrete are essential and cannot be solved by improving the material itself. Therefore, relevant experts put forward the concept of cement-based composite materials - using the idea of "composite" to improve the performance of concrete materials, using fibers as reinforcement When the material is used, there is the concept of fiber-reinforced cement-based composite materials. Although adding fibers with three major functions of crack resistance, reinforcement and toughening into concrete can greatly improve the tensile strength and deformation capacity of concrete, the crack width is not easy to control under the action of load, and it is easy to control under the action of direct tensile load. Strain softening occurs. These shortcomings greatly limit the popularization and application of fiber reinforced concrete in engineering.

In order to overcome the shortcomings of difficult to control the crack width and strain softening of the material, people began to study cement-based composites with the help of micromechanics and fracture mechanics. Mineral admixtures, aggregates, fibers and additives are used as raw materials, and the ultimate elongation is not less than 0.5% under the action of axial tension. When subjected to bending and tensile loads, it has obvious strain hardening behavior and multiple seams. The cracking feature can overcome the shortcomings of traditional concrete materials such as easy cracking and high brittleness, and has a good application prospect.

However, traditional ECC materials are mainly prepared from high-priced quartz sand and imported PVA/PE fibers, which are expensive and difficult to popularize and use in the field of construction engineering. The use of ordinary river sand instead of quartz sand to prepare ECC materials can reduce the cost to a certain extent. However, in recent years, with the large-scale construction of infrastructure in my country, a large amount of sand resources have been consumed. The relevant management regulations of stone collection have made the contradiction between supply and demand of construction sand increasingly prominent, which cannot meet today's construction needs. Especially in the northwest region of my country, the shortage of natural sand itself leads to more serious contradictions, so a new building material is urgently needed to replace natural river sand. However, there are abundant desert aeolian sand resources in Northwest my country, and the particle size of desert aeolian sand is small, which meets the requirements of ECC raw materials. Materials can not only save resources and reduce project costs, but also provide new choices for building materials.

On the other hand, increasing the proportion of fly ash in the cementitious material and reducing the amount of cement is also a method to reduce the preparation cost of ECC materials. Xinjiang Province, which is located in the northwest region of my country, is still mainly based on thermal power generation. Coupled with coal-fired heating in winter, it has abundant fly ash resources. At present, fly ash has been used in the construction industry to a certain extent, but the overall utilization rate is not high. The accumulation of a large amount of excess fly ash not only occupies valuable land resources, but also easily becomes a secondary pollution source of air and land. If a large amount of fly ash is used, it can not only save cement clinker, but also improve the defects of concrete materials. Secondly, the rational use of fly ash can also protect the environment. Therefore, the promotion and use of large-volume fly ash concrete not only has positive significance for the sustainable development of the construction industry, but also points out a feasible way for the harmonious coexistence of man and nature and the sustainable development of society.

For those skilled in the art, how to perfectly combine the industrial waste of fly ash and the natural resource of desert aeolian sand to realize the rational development and utilization of local natural resources and industrial solid waste, and obtain good performance , Building materials that meet the needs of the modern building structure field is one of the important problems to be solved urgently. CN110204273A discloses a desert sand cement-based composite material and a preparation process thereof, wherein the desert sand cement-based composite material is made of main material, auxiliary material I (water reducing agent), auxiliary material II (fiber) and water, and the water-to-binder ratio is It is 0.36-0.38, and the composition of the main ingredients is as follows: 1.0 parts by weight of cement, 1.0-3.5 parts by weight of desert sand, 2.0-4.0 parts by weight of fly ash, 0.1-0.5 parts by weight of desulfurized gypsum, and 0.15-0.6 parts by weight of microsilica; The amount of water reducing agent accounts for 0.5-1% of the weight of cement; the volume ratio of fibers is 0-2%, but this solution can only obtain ordinary fiber-reinforced concrete materials, but cannot obtain high-ductility cement-based composite materials.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the problems of the shortage of existing building materials and the high cost of traditional ECC, and to provide a desert aeolian sand high ductility cement-based composite material and a preparation method thereof.

In order to achieve the above purpose, one aspect of the present invention relates to a desert aeolian sand high ductility cement-based composite material, which is composed of the following raw materials in parts by weight: 1.0 parts of cement, 0.1-3 parts of desert aeolian sand, and 0.1-3 parts of fly ash. 4 parts, 0-0.9 part of silicon powder, 0.0005-0.004 part of rubber powder, water reducing agent accounting for 0.2-1% by weight of cement raw materials, fiber volume ratio of 0-3%, and water-to-binder ratio of 0.32-0.38.

Preferably, the cement is any one or a mixture of two or more of ordinary Portland cement of grades 42.5, 52.5, 62.5 or other types of cement.

Preferably, the fly ash is Class I fly ash, II fly ash or raw ash from coal-fired thermal power plants.

Preferably, the fibers are any one or a mixture of two or more of ultra-high molecular weight polyethylene fibers, high-strength and high-modulus polyvinyl alcohol fibers, or polypropylene fibers.

Preferably, the water reducing agent is a polycarboxylic acid series high-efficiency water reducing agent.

Preferably, the rubber powder is redispersible latex powder and/or hydroxypropyl methylcellulose.

Another aspect of the present invention relates to the preparation method of the desert aeolian sand high ductility cement-based composite material, comprising the following steps:

1) Ingredients: 1.0 part of cement, 0.32-0.38 part of water-to-binder ratio, 0.1-3 part of desert aeolian sand, 0.1-4 part of fly ash, 0-0.9 part of silica fume, 0.0005-0.004 part of rubber powder, fiber The volume rate of the cement is 0-3%, the fiber length is 6mm-18mm, and the amount of water reducing agent accounts for 0.2-1% of the cement weight;

2) Feeding and mixing sequence: first put cement, fly ash, silica fume, desert aeolian sand and rubber powder into the mixing bucket, dry at a slow speed for 2-3 minutes, and then add the water that was evenly mixed in the mixing container in advance Add the mixture of water reducing agent and water reducing agent into the mixing bucket, wet-mix at a slow speed for 2-3min, and finally add the fibers dispersed in advance, add while stirring, until all is added, stir at a slow speed for 2-3min, and then quickly stir for 2- 3min;

3) Forming: pour the prepared mixture into a pre-prepared mold, and vibrate to form;

4) Conservation: Cover the prepared specimen with a layer of cling film, remove the cling film after 24 hours, and dismantle the specimen with the mold, and then dismantle the specimen under standard conditions at a temperature of 20± 2 ℃, the relative humidity above 95% curing to the test age.

Preferably, in the step 2), the fibers must be uniformly dispersed in the matrix to give full play to the reinforcing, toughening, and crack-resistance properties of the fibers. It is added slowly several times to make the fibers evenly dispersed in the material to improve the ductility and toughness of the desert aeolian sand high ductility cement-based composite material.

Preferably, in the step 2), the slow speed is 200-250 r/min, and the fast speed is 900-950 r/min.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The composition of the raw materials of the present invention is simple, the raw materials do not need to be processed too much, and the raw materials do not need to be modified, and the preparation process is simple and easy to implement; the present invention all selects desert aeolian sand as fine aggregates, and uses pulverized coal Ash and silica fume replace part of the cement, so that the natural resource of desert aeolian sand and the two industrial solid wastes such as fly ash and silica fume can be fully utilized, and the project cost is significantly reduced;

(2) The amount of fly ash in the present invention can be very large, which not only saves the cement in the cementitious material, but also realizes the resource utilization of industrial waste, and plays a positive role in protecting the environment; Replacing ordinary sand and rationally using natural resources, it alleviates the current problem of the contradiction between supply and demand of construction sand;

(3) The present invention selects ultra-high molecular weight polyethylene fibers (PE fibers), high-strength and high-modulus polyvinyl alcohol fibers (PVA fibers) or polypropylene fibers (PP fibers), which are better in both economic and performance perspectives, to prepare excellent performance. desert aeolian sand highly ductile cementitious composites.

(4) A certain proportion of rubber powder is used in the components of the present invention, in addition to the most basic thickening effect, it is also beneficial to the improvement of the tensile strain of the cement-based material. Since the redispersible latex powder itself has strong bonding properties, it can improve the elasticity of the matrix, that is, reduce the elastic modulus of the matrix. At the same time, the addition of redispersible latex powder reduces the cracking strength of the matrix. According to the strength criterion of ECC (cement-based composite material), the smaller the cracking strength of the matrix, the more favorable the steady-state multi-crack cracking of ECC. On the other hand, due to the substantial increase in the elasticity of the matrix, its failure mode is different from the brittle failure of traditional concrete, and the critical dimension of the matrix crack instability and failure correspondingly increases, which also means that the fracture toughness and crack tip toughness of the matrix increase. According to the ECC energy criterion, this is not conducive to the steady-state multi-slit cracking of the ECC. Under the joint influence of the above two aspects, the multi-fracture cracking characteristics and strain hardening behavior of ECC are difficult to exert, but due to the strong toughness of its matrix, it still maintains a high ultimate tensile force in the case of less crack propagation and cracking. extensional strain. Therefore, the addition of redispersible latex powder and the adjustment of its content are very important for ECC to achieve better strain hardening performance.

(5) The preparation time of the present invention is short, and the high ductility cement-based composite material with little difference in compressive and flexural strength and good uniaxial tensile performance can be obtained in a short stirring time.

Detailed ways

The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

Example 1

A matrix of desert aeolian sand high ductility cement-based composite material is composed of raw materials in the following proportions by weight: 1.0 part of 42.5 cement, 1.5 part of fly ash, 1.55 part of desert aeolian sand, 0.004 part of water reducing agent and 0.004 part of rubber powder each. parts, the water-binder ratio is 0.34.

Example 2

A desert aeolian sand high ductility cement-based composite material is composed of the following raw materials by weight: 1.0 part of 52.5 cement, 0.429 part of fly ash, 0.429 part of desert aeolian sand, PE fiber volume ratio of 2%, fiber length It is 12mm, the water reducing agent is 0.004 part, the rubber powder is 0.001 part, and the water-to-binder ratio is 0.38.

Example 3

A desert aeolian sand high ductility cement-based composite material is composed of raw materials in the following proportions by weight: 1.0 part of 42.5 cement, 2.4 parts of fly ash, 0.15 part of silica fume, 0.1 part of desert aeolian sand, PE fiber volume ratio 1.5%, the fiber length is 12mm, the water reducing agent is 0.004 part, the rubber powder is 0.002 part, and the water-to-binder ratio is 0.38.

Example 4

A desert aeolian sand high ductility cement-based composite material is composed of raw materials in the following proportions by weight: 1.0 part of 42.5 cement, 0.5 part of fly ash, 0.15 part of silica fume, 1.5 part of desert aeolian sand, and a volume ratio of PE fiber. 1.5%, the fiber length is 12mm, the water reducing agent is 0.004 part, the rubber powder is 0.0005 part, and the water-to-binder ratio is 0.36.

Example 5

A desert aeolian sand high ductility cement-based composite material is composed of raw materials in the following proportions by weight: 1.0 part of 42.5 cement, 1.0 part of fly ash, 0.75 part of desert aeolian sand, PE fiber volume ratio of 1.5%, fiber length It is 12mm, the water reducing agent and rubber powder are 0.004 parts each, and the water-to-binder ratio is 0.32.

Example 6

A desert aeolian sand high ductility cement-based composite material is composed of the following raw materials in parts by weight: 1.0 part of 42.5 cement, 1.5 part of fly ash, 0.9 part of silica fume, 0.75 part of desert aeolian sand, PE fiber volume ratio 1.5%, the fiber length is 12mm, the water-reducing agent and the rubber powder are each 0.004 parts, and the water-to-binder ratio is 0.34.

Example 7

A desert aeolian sand high ductility cement-based composite material is composed of raw materials in the following proportions by weight: 1.0 part of 42.5 cement, 3.5 parts of fly ash, 0.75 part of desert aeolian sand, PE fiber volume ratio of 1.5%, fiber length It is 12mm, the water reducing agent and rubber powder are 0.004 parts each, and the water-to-binder ratio is 0.34.

Example 8

A desert aeolian sand high ductility cement-based composite material is composed of raw materials in the following proportions by weight: 1.0 parts of 42.5 cement, 1.5 parts of fly ash, 2.35 parts of desert aeolian sand, a PE fiber volume ratio of 1.5%, and a fiber length of 1.5%. It is 12mm, the water reducing agent and rubber powder are 0.004 parts each, and the water-to-binder ratio is 0.34.

Example 9

A desert aeolian sand high ductility cement-based composite material is composed of raw materials in the following proportions by weight: 1.0 part of 42.5 cement, 1.5 part of fly ash, 1.55 part of desert aeolian sand, a PE fiber volume ratio of 1.25%, and a fiber length of 1.25%. It is 6mm, the water reducing agent and rubber powder are 0.004 parts each, and the water-to-binder ratio is 0.34.

Example 10

A desert aeolian sand high ductility cement-based composite material is composed of the following raw materials by weight: 1.0 part of 42.5 cement, 1.5 part of fly ash, 1.55 part of desert aeolian sand, PE fiber volume ratio of 1.5%, fiber length It is 18mm, the water reducing agent and rubber powder are 0.004 parts each, and the water-to-binder ratio is 0.34.

Example 11

A desert aeolian sand high ductility cement-based composite material is composed of the following raw materials by weight: 1.0 part of 42.5 cement, 1.5 part of fly ash, 1.55 part of desert aeolian sand, PE fiber volume ratio of 1.25%, PVA fiber The volume ratio is 0.25%, the fiber length is 12mm, the water reducing agent and the rubber powder are each 0.004 parts, and the water-to-binder ratio is 0.34.

Example 12

A desert aeolian sand high ductility cement-based composite material is composed of the following raw materials by weight: 1.0 part of 42.5 cement, 3 parts of fly ash, 0.75 part of desert aeolian sand, PVA fiber volume ratio of 1.5%, fiber length It is 12mm, the water reducing agent and rubber powder are 0.004 parts each, and the water-to-binder ratio is 0.34.

In the above examples 1-12, the cement is 42.5 or 52.5 ordinary Portland cement; the fly ash is Class I fly ash; the average particle size of desert aeolian sand is less than or equal to 110 μm; the fiber is ultra-high molecular weight polyethylene or high-strength high-modulus polyethylene Alcohol fiber; superplasticizer and rubber powder are polycarboxylate superplasticizer and redispersible latex powder respectively.

The preparation method of the desert aeolian sand high ductility cement-based composite material described in Examples 1-12 is relatively simple, easy to operate and easy to implement, and includes the following steps:

(1) batching is carried out according to the specific formula of each embodiment;

(2) Feeding and mixing sequence: first put cement, fly ash, silica fume, desert aeolian sand and rubber powder into the mixing bucket, dry at a slow speed (250r/min) for 2 minutes, and then put them in the mixing container in advance The well-stirred mixture of water and water reducer is added to the mixing bucket, wet-mixed at a slow speed (250 r/min) for 2 minutes, and finally the fibers dispersed in advance are added, and added while stirring until all is added, and the slow speed (250 r/min) ) stir for 2min, and then quickly (950r/min) stir for 2min;

(3) Forming: pour the prepared mixture into a pre-prepared mold, and vibrate to form;

(4) Conservation: Cover the prepared specimen with a layer of cling film, remove the cling film after 24 hours, and dismantle the specimen with the mold, and then dismantle the specimen under standard conditions at a temperature of 20 °C. ± 2 ℃, relative humidity above 95% curing to 7d, 28d.

The desert aeolian sand high ductility cement-based composite material prepared by the method of Example 1-12 is tested for fluidity according to the relevant regulations in the "Determination of the fluidity of cement mortar" (GB/T2419-2016); Cube test blocks with a size of 70.7mm × 70.7mm × 70.7mm, three for each age, according to the relevant provisions of the "Standards for Basic Performance Test of Building Mortar" (JGJ/T70-2009) The test blocks are tested for compressive performance. ; Make prismatic test blocks with a size of 40mm × 40mm × 160mm, three for each age, and test the flexural properties of the test blocks according to the relevant regulations in "Cement Mortar Strength Test Method" (GB17671-1999); Dumbbell-shaped test blocks with a size of 250mm × 60mm × 15mm, three for each age, were tested according to the relevant regulations in "Test Methods for Mechanical Properties of High-ductility Fiber-reinforced Cement-based Composites" (JC/T2461-2018). Tensile property testing. The test results are shown in Table 1-2 below:

Table 1 Work performance and mechanical properties (compression resistance, flexural resistance) test results of different embodiments

Table 2 Uniaxial tensile test results of different embodiments

It can be seen from the test results in Tables 1-2 that the desert aeolian sand high ductility cement-based composite material provided by the present invention has good working and mechanical properties, and the flexural toughness of the material 28d was evaluated with reference to ASTMC1018, and the calculation results are shown in the table. As shown in 3, most of the obtained results are I _T > _T , indicating that the desert aeolian sand high ductility cement-based composite material provided by the present invention has good toughness, all of which are tough materials. The better the toughness.

Table 3 Bending toughness calculation results of different embodiments

It can be seen that the cement-based composite material obtained by combining components of different dosages in the present invention has good uniaxial tensile properties, and the compressive strength, flexural strength and bending toughness also meet the most basic requirements of high-ductility cement-based composite materials. Require.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above-mentioned specific embodiments, and those skilled in the art can make various variations or modifications within the scope of the claims, which do not affect the essential content of the present invention.

Claims (9)

1. a desert aeolian sand high ductility cement-based composite material, is characterized in that, is made up of the raw material of following weight part ratio: cement 1.0 part, desert aeolian sand 0.1-3 part, fly ash 0.1-4 part, silicon 0-0.9 part of powder, 0.0005-0.004 part of rubber powder, 0.2-1% by weight of cement raw material, water reducing agent, fiber volume ratio of 0-3%, and water-to-binder ratio of 0.32-0.38. 2. desert aeolian sand high ductility cement-based composite material according to claim 1, is characterized in that, described cement is any one or the mixture of two or more in the ordinary Portland cement of grades 42.5, 52.5, 62.5 . 3. desert aeolian sand high ductility cement-based composite material according to claim 1, is characterized in that, described fly ash is Class I fly ash, II fly ash or coal-fired thermal power plant raw ash. 4. desert aeolian sand high ductility cement-based composite material according to claim 1, is characterized in that, described fiber is any one or both in ultra-high molecular weight polyethylene fiber or high-strength high-modulus polyvinyl alcohol fiber or polypropylene fiber. more than one mixture. 5 . The high-ductility cement-based composite material of desert aeolian sand according to claim 1 , wherein the water-reducing agent is a polycarboxylic acid series high-efficiency water-reducing agent. 6 . 6 . The high ductility cement-based composite material of desert aeolian sand according to claim 1 , wherein the rubber powder is redispersible latex powder and/or hydroxypropyl methylcellulose. 7 . 7. A preparation method of desert aeolian sand high ductility cement-based composite material according to any one of claims 1 to 6, characterized in that, comprising the following steps: 1) Ingredients: 1.0 part of cement, 0.32-0.38 part of water-to-binder ratio, 0.1-3 part of desert aeolian sand, 0.1-4 part of fly ash, 0-0.9 part of silica fume, 0.0005-0.004 part of rubber powder, fiber The volume rate of the cement is 0-3%, the fiber length is 6mm-18mm, and the amount of water reducing agent accounts for 0.2-1% of the cement weight; 2) Feeding and mixing sequence: first put cement, fly ash, silica fume, desert aeolian sand and rubber powder into the mixing bucket, dry at a slow speed for 2-3 minutes, and then add the water that was evenly mixed in the mixing container in advance Add the mixture of water reducing agent and water reducing agent into the mixing bucket, wet-mix at a slow speed for 2-3min, and finally add the fibers dispersed in advance, add while stirring, until all is added, stir at a slow speed for 2-3min, and then quickly stir for 2- 3min; 3) Forming: pour the prepared mixture into a pre-prepared mold, and vibrate to form; 4) Conservation: Cover the prepared specimen with a layer of cling film, remove the cling film after 24 hours, and dismantle the specimen with the mold, and then dismantle the specimen under standard conditions at a temperature of 20± 2 ℃, the relative humidity above 95% curing to the test age. 8. the preparation method of desert aeolian sand high ductility cement-based composite material according to claim 7, is characterized in that, in described step 2), before stirring, the fiber is dispersed to no obvious bunching phenomenon, in the stirring process A small amount of medium and small amounts are added slowly and several times to make the fibers evenly dispersed in the material, so as to improve the ductility and toughness of the desert aeolian sand high ductility cement-based composite material. 9 . The preparation method of desert aeolian sand high ductility cement-based composite material according to claim 7 , wherein, in the step 2), the slow speed is 200-250 r/min, and the fast speed is 900-950 r/min. 10 .