CN107721287B - A kind of diatomite modified concrete and preparation method thereof - Google Patents

Abstract

The invention discloses a diatomite modified concrete and a preparation method thereof. The diatomite modified concrete consists of the following components in parts by weight: 15-20 parts by weight of cement, 1-5 parts by weight of diatomite, 6-6 parts by weight of water 8 parts by weight, 25-30 parts by weight of river sand, 40-45 parts by weight of gravel, and 0.2-0.5 parts by weight of water reducing agent. In the invention, by doping a certain proportion of diatoms in the concrete, the diatomite is pretreated in advance in the process of preparing the concrete, and the prepared concrete solves the problem of large early shrinkage of high-strength concrete, and can effectively reduce the brittleness of high-strength concrete , without reducing the strength of high-strength concrete.

Description

A kind of diatomite modified concrete and preparation method thereof

technical field

The invention relates to the technical field of concrete preparation, in particular to a diatomite modified concrete and a preparation method thereof.

Background technique

Many experts and scholars at home and abroad are committed to improving the early crack resistance of high-strength concrete from the perspective of concrete materials. At present, there are two commonly used technical approaches to improve the early shrinkage of high-strength concrete: one is to add superplasticizers to concrete; the other is to add mineral admixtures. However, only adding water reducer can not improve the composition and quality of cement hydration products, but adding mineral admixtures can improve the early shrinkage of concrete and the composition and quality of cement hydration products. Studies have shown that adding mineral admixtures or adding pre-absorbent internal curing materials can effectively prevent early cracking of concrete. The currently used mineral admixtures mainly include slag powder, fly ash and silica fume. The internal maintenance material is a material with a porous structure, which has the functions of water holding and water release. When the water evaporation and hydration reaction cause the free water inside the concrete to drop to a certain level, these internal curing materials can release water and maintain the relative humidity in the system. At present, the most widely used internal curing material is ceramsite.

By comparing the effects of several admixtures on the early crack resistance of concrete, it is concluded that different admixtures have different effects on early crack resistance, and the mineral admixture accounts for 30% of the cementitious material. Fly ash has the ability to appropriately reduce the brittleness of concrete and inhibit early cracking, while mineral powder and fly ash have the opposite effect. It is pointed out that the chemical composition of such admixtures, the impact of pozzolanic activity on hydration reactions, and the particle size, The effect of specific surface area on pore structure is the main reason affecting the early crack resistance of concrete. Saturated ceramsite is used as an internal curing material to partially replace coarse aggregate in concrete. When the content of ceramsite is 20%, the early shrinkage is reduced by about 50%, but the incorporation of ceramsite reduces the mechanical properties of concrete greatly.

Contents of the invention

The purpose of the present invention is to provide a diatomite-modified concrete, which can solve the problem of large early shrinkage of high-strength concrete, effectively reduce the brittleness of high-strength concrete without reducing the strength of high-strength concrete.

In addition, the present invention also provides a method for preparing the above concrete.

The present invention realizes through following technical scheme:

A diatomite-modified concrete, consisting of the following components in parts by weight:

15-20 parts by weight of cement, 1-5 parts by weight of diatomite, 6-8 parts by weight of water, 25-30 parts by weight of river sand, 40-45 parts by weight of gravel, and 0.2-0.5 parts by weight of water reducing agent.

The existing technologies aimed at improving the early shrinkage and cracking of high-strength concrete mostly use the addition of composite mineral admixtures and the addition of porous aggregates to replace ordinary aggregates. However, these two methods have the following disadvantages:

Whether it is mixed with composite mineral admixture or pre-absorbed water saturated porous, its dosage is generally about 20% to 30%, which is a large amount and consumes materials. And there is a risk of reducing the strength of concrete.

Moreover, mineral admixtures are generally industrial waste residues. Although they provide a way to reuse, the future output of industrial by-products with high pollution will be greatly limited, and they are not a green raw material. At the same time, the particle size and composition of mineral admixtures have a great influence on the performance of concrete, so there are certain requirements for the quality of mineral admixtures. Porous ceramsite and shale are commonly used porous aggregates. When mixed into concrete, they can exert their water-holding and water-releasing functions, maintain the relative humidity in the concrete, and reduce concrete shrinkage. Greatly reduced, lost the fundamental role of high-strength concrete

The invention adopts diatomite to replace the traditional admixture. The diatomite is a biological sedimentary rock deposited from the remains of single-cell biological diatoms, has good pozzolanic performance, and is a natural and environmentally friendly concrete admixture.

The applicant has found through a large number of tests: doping diatomite (about 1% to 5% of diatomite) according to the ratio of the present invention can reduce the early cracking area by about 30% to 65%. When the doping amount is 10 parts by weight, the strength of the pre-absorbed diatomite high-strength concrete is reduced by 70%.

Therefore, the concrete formulation of the present invention can improve the problem of large early shrinkage of high-strength concrete by doping a certain proportion of diatomite, and at the same time, it will not affect other properties of concrete. Diatomite is a natural and environmentally friendly recycled Resources, will not cause pollution, use a small amount.

Further, it consists of the following parts by weight:

15-20 parts by weight of cement, 2-4 parts by weight of diatomite, 6-8 parts by weight of water, 25-30 parts by weight of river sand, 40-45 parts by weight of gravel, and 0.2-0.5 parts by weight of water reducing agent.

Further, it consists of the following parts by weight:

20 parts by weight of cement, 3 parts by weight of diatomaceous earth, 8 parts by weight of water, 25 parts by weight of river sand, 40 parts by weight of gravel, and 0.4 parts by weight of a water reducing agent.

Further, the water reducer is a naphthalene-based high-efficiency water reducer.

A diatomite pretreatment method comprises mixing diatomite and tap water at a weight ratio of 1:1.5-1:1.7, performing water absorption treatment, stirring evenly, and making the mixed material in a saturated surface-dry state.

Diatomite and tap water are subjected to water absorption treatment at a weight ratio of 1:1.5-1:1.7, and then applied to the preparation of concrete, which can significantly improve the early shrinkage of high-strength concrete and effectively reduce the brittleness of high-strength concrete.

The invention relates to an application of diatomite. The diatomite treated with water absorption is applied to the preparation of ordinary concrete.

A preparation method of diatomite modified concrete, comprising the following steps:

1) Diatomite pretreatment: mix diatomite and tap water at a weight ratio of 1:1.5-1:1.7, perform water absorption treatment, and stir evenly, so that the mixed material is in a saturated surface-dry state;

2) Pour cement, river sand and gravel into the mixer in proportion to dry mixing;

3) Dissolving the water reducing agent in water to form a water reducing agent aqueous solution;

4) Pour the water reducing agent aqueous solution into the mixer for wet mixing;

5) Pour the saturated surface-dried diatomaceous earth into the mixer, continue stirring, and obtain concrete after uniformity.

Concrete and ordinary high-strength concrete (concrete not containing diatomite) prepared by the method of the present invention are simultaneously maintained under the concrete early cracking test curing environment stipulated in the national standard "Ordinary Concrete Long-term Performance and Durability Test Method" for 24 hours. hours, compared with ordinary high-strength concrete, the concrete prepared by the present invention has a maximum crack width reduction of 50%-100%, a crack area reduction of about 30%-100%, and a maximum delay of cracking time of 1.5 hours, indicating that pre-absorbed diatomite can effectively improve Early cracking of high-strength concrete. At the same time, compared with ordinary high-strength concrete, the 28-day compressive strength is up to 10%, and the 28-day tension and compression is 23.5% higher than ordinary high-strength concrete, indicating that pre-absorbed diatomite concrete can effectively reduce its brittleness without affecting the mechanical indicators of high-strength concrete .

At the same time, compared with the non-pre-absorbed diatomite high-strength concrete, the pre-absorbed diatomite is mixed into the concrete at the same dosage, and its work performance is significantly improved, the fluidity is increased by 5-10cm, and the 28-day compressive strength is also improved. 5-8%. The main reasons are as follows: first, the diatomite mixed with pre-absorbed water has a large degree of dispersion and is easy to mix evenly; second, due to the "internal maintenance" effect of pre-absorbed diatom earth, it can be replenished in time in the late stage of strength development. water, to promote the continuous hydration reaction.

Moreover, the following conclusions were also obtained: the doping amount of diatomite should not be greater than 5%. When the doping amount of diatomite is too large, although the problem of early cracking can be solved, the strength of concrete will be greatly reduced.

The preparation method of the present invention rationally designs the ratio of each component, and pre-absorbs diatomite at the same time, which can obviously improve the early shrinkage problem of high-strength concrete, and can effectively reduce the brittleness of high-strength concrete without reducing the its strength

Further, the following steps are also included: pouring concrete into the mould, vibrating forming, natural curing, and stripping.

In the test of pre-absorbed diatomite ordinary concrete (C30, water-cement ratio 0.5). The 28-day strength of pre-absorbed diatomite mixed with 1%-5% is reduced by 4%-13% compared with the benchmark ordinary concrete; it can be seen that the "internal curing" effect of pre-absorbed diatomite is effective in high-strength concrete with relatively small water-cement ratio The effect is more obvious.

Further, the average particle size of river sand is 0.5-0.7mm.

Further, the average particle size of the gravel is 15-25mm.

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

1. The concrete formula of the present invention can improve the early shrinkage problem of high-strength concrete by doping a certain proportion of diatomite, and at the same time, it will not affect other properties of concrete, and diatomite is a kind of natural environmental protection The renewable resource will not cause pollution, and the usage is small.

2. The preparation method of the present invention rationally designs the proportioning ratio between each component, and carries out pre-absorption treatment to diatomite at the same time, can obviously improve the early shrinkage problem of high-strength concrete, and can effectively reduce the brittleness of high-strength concrete, and at the same time without reducing its strength.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail in conjunction with the following examples. The schematic embodiments of the present invention and their descriptions are only used to explain the present invention, and are not intended as a guideline for the present invention. limit.

Example 1:

A preparation method of diatomite modified concrete, comprising the following steps:

1), diatomite pretreatment: mix 1 weight part of diatomite and 1.5 weight parts of tap water, carry out water absorption treatment, stir evenly, make the material after mixing be in saturated surface dry state;

2), 15 parts by weight of cement, 25 parts by weight of river sand and 40 parts by weight of crushed stone are poured into the mixer for dry mixing, the average particle size of the river sand is 0.5 mm, and the average particle size of the crushed stone is 15 mm;

3) Dissolving 0.2 parts by weight of naphthalene-based high-efficiency water-reducer in water to form an aqueous water-reducer solution;

4) Pour the aqueous solution of naphthalene-based high-efficiency water reducer into the mixer for wet mixing;

5) Pour the saturated surface-dried diatomaceous earth into the mixer, continue stirring, and obtain concrete evenly;

6) Pour the concrete into the mold, vibrate for forming, natural curing, and stripping.

The prepared concrete consists of the following components in parts by weight:

15 parts by weight of cement, 1 part by weight of diatomaceous earth, 6 parts by weight of water, 25 parts by weight of river sand, 40 parts by weight of gravel, and 0.2 parts by weight of water reducing agent.

Example 2:

A preparation method of diatomite modified concrete, comprising the following steps:

1), diatomite pretreatment: mix 2 parts by weight of diatomite and 3.4 parts by weight of tap water, perform water absorption treatment, and stir evenly, so that the mixed material is in a saturated surface-dry state;

2) Pour 20 parts by weight of cement, 30 parts by weight of river sand and 45 parts by weight of crushed stone into a mixer for dry mixing. The average particle size of the river sand is 0.7 mm, and the average particle size of the crushed stone is 25 mm;

3) Dissolving 0.5 parts by weight of naphthalene-based high-efficiency water-reducer in water to form an aqueous water-reducer solution;

4) Pour the aqueous solution of naphthalene-based high-efficiency water reducer into the mixer for wet mixing;

5) Pour the saturated surface-dried diatomaceous earth into the mixer, continue stirring, and obtain concrete evenly;

6) Pour the concrete into the mold, vibrate for forming, natural curing, and stripping.

The prepared concrete consists of the following components in parts by weight:

20 parts by weight of cement, 5 parts by weight of diatomaceous earth, 7 parts by weight of water, 30 parts by weight of river sand, 45 parts by weight of gravel, and 0.5 parts by weight of a water reducing agent.

Example 3:

A preparation method of diatomite modified concrete, comprising the following steps:

1), diatomite pretreatment: mix 4 parts by weight of diatomite and 6.4 parts by weight of tap water, perform water absorption treatment, and stir evenly, so that the mixed material is in a saturated surface-dry state;

2), 18 parts by weight of cement, 28 parts by weight of river sand and 42 parts by weight of crushed stone are poured into the mixer in proportion to dry mixing. The average particle diameter of the river sand is 0.6mm, and the average particle diameter of the crushed stone is 20mm;

3) Dissolving 0.3 parts by weight of naphthalene-based high-efficiency water reducer in water to form an aqueous water reducer solution;

4) Pour the aqueous solution of naphthalene-based high-efficiency water reducer into the mixer for wet mixing;

5) Pour the saturated surface-dried diatomaceous earth into the mixer, continue stirring, and obtain concrete evenly;

6) Pour the concrete into the mold, vibrate for forming, natural curing, and stripping.

The prepared concrete consists of the following components in parts by weight:

18 parts by weight of cement, 4 parts by weight of diatomaceous earth, 8 parts by weight of water, 28 parts by weight of river sand, 42 parts by weight of gravel, and 0.3 parts by weight of a water reducing agent.

Example 4:

A preparation method of diatomite modified concrete, comprising the following steps:

1), diatomite pretreatment: mix 5 parts by weight of diatomite with 7.5 parts by weight of tap water, perform water absorption treatment, and stir evenly, so that the mixed material is in a saturated surface-dry state;

2), 18 parts by weight of cement, 28 parts by weight of river sand and 42 parts by weight of crushed stone are poured into the mixer in proportion to dry mixing. The average particle diameter of the river sand is 0.6mm, and the average particle diameter of the crushed stone is 22mm;

3) Dissolving 0.4 parts by weight of naphthalene-based high-efficiency water-reducer in water to form an aqueous water-reducer solution;

4) Pour 0.4 parts by weight of naphthalene-based high-efficiency water reducer aqueous solution into a mixer for wet mixing;

5) Pour the saturated surface-dried diatomaceous earth into the mixer, continue stirring, and obtain concrete evenly;

6) Pour the concrete into the mold, vibrate for forming, natural curing, and stripping.

The prepared concrete consists of the following components in parts by weight:

18 parts by weight of cement, 5 parts by weight of diatomaceous earth, 8 parts by weight of water, 28 parts by weight of river sand, 42 parts by weight of gravel, and 0.4 parts by weight of water reducing agent.

Example 5:

A preparation method of diatomite modified concrete, comprising the following steps:

1), diatomite pretreatment: mix 3 parts by weight of diatomite and 4.8 parts by weight of tap water, perform water absorption treatment, and stir evenly, so that the mixed material is in a saturated surface-dry state;

2), 20 parts by weight of cement, 25 parts by weight of river sand and 40 parts by weight of crushed stone are poured into the mixer for dry mixing, the average particle size of the river sand is 0.6mm, and the average particle size of the crushed stone is 20mm;

3) Dissolving 0.4 parts by weight of naphthalene-based high-efficiency water-reducer in water to form an aqueous water-reducer solution;

4) Pour the aqueous solution of naphthalene-based high-efficiency water reducer into the mixer for wet mixing;

5) Pour the saturated surface-dried diatomaceous earth into the mixer, continue stirring, and obtain concrete evenly;

6) Pour the concrete into the mold, vibrate for forming, natural curing, and stripping.

The prepared concrete consists of the following components in parts by weight:

20 parts by weight of cement, 3 parts by weight of diatomaceous earth, 8 parts by weight of water, 25 parts by weight of river sand, 40 parts by weight of gravel, and 0.4 parts by weight of a water reducing agent.

Comparative example 1:

This comparative example is based on Example 5, the difference is that diatomaceous earth is not used.

Comparative example 2:

This comparative example is based on Example 5, the difference is that the content of diatomaceous earth is 6 parts by weight.

Comparative example 3:

This comparative example is based on Example 5, the difference is that the content of diatomaceous earth is 8 parts by weight.

Comparative example 4:

This comparative example is based on Example 5, the difference is that the content of diatomaceous earth is 10 parts by weight.

Comparative example 5:

This comparative example is based on Example 5, and the difference is that step 1) is not included, that is, diatomaceous earth is not pretreated.

Comparative example 6:

This comparative example is based on Example 5, and the difference is that in step 1) diatomite is 3 parts by weight and tap water is 7.5 parts by weight, that is, the ratio of diatomaceous earth and tap water is 1:2.5.

Comparative example 7:

This comparative example is based on Example 5, the difference is that: in step 1), the diatomite is 3 parts by weight, and the tap water is 3 parts by weight, that is, the ratio of diatomaceous earth and tap water is 1:1.0.

The concrete prepared by embodiment 1-embodiment 5, comparative example 1-comparative example 7 is used for following test respectively:

Pour the concrete into the early cracking test mold of 800mm×600mm×100mm and the mechanical performance test mold of 150mm×150mm×150mm, and put it in a constant temperature and humidity curing room with a temperature of 20±5°C and a relative humidity of 50%. maintenance. For early-stage cracking test specimens, after standing for 30 minutes, carry out wind blowing treatment, so that the wind speed at 100mm directly above the center of the specimen surface is 5.5m/s, and then maintain for 24 hours, record the time of initial crack appearance, crack length and maximum Width, to calculate the cracking area; for mechanical performance test specimens, after 28 days of curing, test the compressive strength and tensile strength of the specimens and calculate the tension-compression ratio. The test results are shown in Table 1:

Table 1

It can be seen from the data in Table 1 that:

1), by the data comparison of embodiment 1-embodiment 5 and comparative example 1, it can be seen that the compressive strength and the splitting tensile strength do not change substantially in the concrete without diatomite doped with diatomite doped, However, the maximum crack width and total crack area of the concrete without diatomaceous earth both doubled, and the initial cracking time was shortened by half an hour.

2), by the comparison of the data of Example 1-Example 5 and Comparative Example 2-Comparative Example 4, it can be seen that as the diatomite doping amount increases, the maximum crack width and the total crack area decrease, when diatomite When the doping amount is 10%, the large crack width and the total cracking area are 0, but, with the increase of diatomite doping amount, the compressive strength and splitting tensile strength are gradually decreasing, when the diatomite doping amount When it is 10%, the compressive strength and splitting tensile strength are reduced by about 70%.

3), by the comparison of the data of Example 1-Example 5 and Comparative Example 5-Comparative Example 7, it can be seen that when the doped diatomite does not undergo water absorption pretreatment, or during pretreatment, the ratio of diatomite to tap water The compressive strength and splitting tensile strength are all reduced, and the maximum crack width and total cracking area are basically unchanged.

In summary, when the doping amount of diatomite is set within the scope of the present invention, and when preparing concrete, the diatomite is pre-treated to absorb water in advance, which can effectively reduce the problem of early cracking of concrete, and at the same time will not affect the concrete. compressive strength and splitting tensile strength.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the scope of the present invention. Protection scope, within the spirit and principles of the present invention, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present invention.

Claims (9)

1. a diatomite modified concrete is characterized in that, is made up of following components by weight: 15-20 parts by weight of cement, 1-5 parts by weight of diatomaceous earth, 6-8 parts by weight of water, 25-30 parts by weight of river sand, 40-45 parts by weight of gravel, and 0.2-0.5 parts by weight of water reducing agent. Diatomite is pretreated diatomite, and the pretreatment is: mix diatomite with tap water in a weight ratio of 1:1.5-1:1.7, perform water absorption treatment, stir evenly, and make the mixed material saturated dry state. 2. a kind of diatomite modified concrete according to claim 1, is characterized in that, is made up of following components by weight: 15-20 parts by weight of cement, 2-4 parts by weight of diatomaceous earth, 6-8 parts by weight of water, 25-30 parts by weight of river sand, 40-45 parts by weight of gravel, and 0.2-0.5 parts by weight of water reducing agent. Diatomite is pretreated diatomite, and the pretreatment is: mix diatomite with tap water in a weight ratio of 1:1.5-1:1.7, perform water absorption treatment, stir evenly, and make the mixed material saturated dry state. 3. a kind of diatomite modified concrete according to claim 1, is characterized in that, is made up of following components by weight: 20 parts by weight of cement, 3 parts by weight of diatomaceous earth, 8 parts by weight of water, 25 parts by weight of river sand, 40 parts by weight of gravel, and 0.4 parts by weight of a water reducing agent. 4. A diatomite-modified concrete according to claim 1, wherein the water reducer is a naphthalene-based high-efficiency water reducer. 5. a pretreatment method of diatomite, it is characterized in that, diatomite and tap water are mixed by weight 1:1.5-1:1.7, carry out water absorption treatment, stir, make the material after mixing be in saturated surface dry state. 6. A method for preparing concrete as claimed in any one of claims 1-3, characterized in that, comprising the following steps: 1) Diatomite pretreatment: mix diatomite and tap water at a weight ratio of 1:1.5-1:1.7, perform water absorption treatment, and stir evenly, so that the mixed material is in a saturated surface-dry state; 2) Pour cement, river sand and gravel into the mixer in proportion to dry mixing; 3) Dissolving the water reducing agent in water to form a water reducing agent aqueous solution; 4) Pour the water reducing agent aqueous solution into the mixer for wet mixing; 5) Pour the saturated surface-dried diatomaceous earth into the mixer, continue stirring, and obtain concrete after uniformity. 7 . The method for preparing concrete according to claim 6 , further comprising the steps of: pouring concrete into a mould, vibration molding, natural maintenance, and stripping. 8. The preparation method of concrete according to claim 6, characterized in that, the average particle diameter of the river sand is 0.5-0.7mm. 9. The preparation method of concrete according to claim 6, characterized in that, the average particle diameter of the gravel is 15-25mm.