RU2667402C1 - Method for preparation of basalt-fiber-concrete mixture - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: invention relates to a technology for the production of dispersed-reinforced concrete mixtures for the manufacture of building products and structures. According to the invention, a dry concrete mixture is first prepared from coarse and fine aggregates and 90 % of cement, which is closed with water in an amount of 40–50 % of the design volume. Basalt fibers taken in the amount of 0.4–0.6 % of the total weight of cement and the remaining mixing water of the remaining 10 % dry cement, a suspension is prepared by mixing all components in a high-speed rotary mixer. Prepared slurry is introduced into the partially closed concrete mixture and mixed in a high-speed rotary mixer until uniform. For the preparation of the suspension, either all of the remaining mixing water is used in an amount of 60–50 %, or 55–40 % of the remaining mixing water. In the latter case, 5–10 % of the remaining water is dissolved by the PowerFlow 1190 hyperplasticizer, taken in the amount of 0.4–0.8 % of the total mass of the cement. Prepared aqueous solution of the hyperplasticizer PowerFlow 1190 is introduced into the fiber-reinforced concrete mixture at the last stage of its mixing.

EFFECT: ensuring a high degree of homogeneity of the basalt-fiber-concrete mixture, increasing the strength characteristics of concrete and stability of strength indicators.

1 cl, 2 dwg

Description

The present invention relates to the production of building materials, in particular, to a technology for the production of dispersively reinforced concrete mixtures for the manufacture of building products and structures.

From the existing level of technology there is known a method of preparing a dispersion-reinforced solution (patent RU 2191690, publ. 10/27/2008), which includes three stages: mixing the binder with a fine aggregate; mineral fiber is added to the binder mixture with fine aggregate, the diameter and length of which is 0.25-3 microns and 0.25-2000 microns, respectively, then mixing is carried out in a forced-action concrete mixer; at the last stage of forced alteration, the dry components are gradually wetted with mixing water. The disadvantage of this method is the uneven distribution of fibers in the volume of the concrete mixture, which increases the variability of the strength of cement materials.

Concrete mixtures are known (patents RU 2480428, publ. 04/27/2013, RU 2355656, publ. 05/20/2009, RU 2569140, publ. 11/20/2015, RU 2609784 C1, publ. 03.02.2017), which as a dispersed reinforcement (fiber) contain basalt fibers of various modifications. The methods for preparing such concrete mixtures do not differ in technological features from standard methods. All components are mixed in a concrete mixer. The differences are in the composition of the concrete mix and the presence of various modifiers. The disadvantage of these methods is the uneven distribution of fibers in the volume of the concrete mixture, which increases the variability of the strength of fiber concrete and reduces the class of concrete in terms of compressive and tensile strength.

The introduction of micro-reinforcing components, both organic and mineral, into the concrete mixture is complicated by the fact that, without taking into account the nature of the surface of the fibers, it is quite problematic to evenly distribute them over the volume of the mixture. With an increase in the specific surface of the fiber, the tendency to adhesion of individual fibers to each other increases, which leads to the formation of lumps of interwoven fibers (hedgehogs), their uneven distribution over the volume of the material and a significant violation of the uniformity of the structure of the concrete mixture. It is not possible to carry out a qualitative distribution of basalt fibers in concrete mix using standard mechanical methods of mixing the components.

Known methods for the preparation of basalt fiber concrete mixture from the source (Improving the manufacturing technology of basalt fiber concrete with increased homogeneity / A.I. Kudyakov, BC Plevkov, K.L. Kudyakov, A.V. Nevsky, A.S. Ushakova // Building materials. - 2015. - No. 10. - S. 44-47). In this source, it is proposed to solve the problem of introducing fibers into a concrete mixture by applying several technological methods: introducing fibers into a dry mixture, introducing fibers into a partially mixed concrete mixture, introducing fibers in an aqueous solution of a surfactant. The closest of these methods is a method for preparing a basalt-fiber-concrete mixture with the introduction of basalt fibers into a partially mixed concrete mixture. First, cement, coarse and fine aggregates are mixed in dry form. Then the resulting dry concrete mixture is partially water shut in the amount of 40% of the design volume of mixing water. Basalt fibers in the amount of 0.4-0.6% of the total mass of cement and the remainder of the design volume of mixing water are introduced into the partially mixed concrete mix. After that, the fiber-reinforced concrete mixture is mixed in a high-speed rotary mixer until smooth.

The disadvantage of this method is the presence of "hedgehogs", and in the case of a satisfactory distribution of the fibers in the volume of the concrete mixture, the adhesion of the fibers to the cement stone deteriorates, which leads to a decrease in the variability and / or strength of the fiber concrete.

The technical problem solved by the invention is to improve the process to ensure uniform distribution of fibers in the volume during the preparation of fiber-reinforced concrete mixture and to reduce the variability.

The technical result consists in obtaining a basalt-fiber-concrete mixture with a high degree of stability of strength indicators. This ensures an increase in the strength characteristics of concrete, namely, the class of concrete in terms of compressive and tensile strength.

The specified technical result is achieved as follows. According to the claimed method, as well as according to the prototype method, cement, coarse and fine aggregates are first mixed in dry form. The resulting dry concrete mixture is partially water shut in an amount of at least 40% of the design volume of the mixing water. Basalt fibers in the amount of 0.4-0.6% of the total mass of cement and the remainder of the design volume of mixing water are introduced into the partially mixed concrete mix. The resulting fiber-reinforced concrete mixture is mixed in a high-speed rotary mixer until smooth.

In contrast to the prototype for the preparation of dry concrete mix take 90% of the design quantity of cement, and dry concrete mix shut water in an amount of 40-50% of the design volume of mixing water. The difference is also that basalt fibers are injected into the partially-mixed concrete mixture in the form of a suspension. The suspension is prepared from basalt fibers, the remaining 10% of dry cement and the remaining mixing water, which are mixed in a high-speed rotary mixer.

To prepare the suspension, you can use the entire amount of water remaining after partial mixing of the concrete mixture in an amount of 60-50% or only 55-40% of the remaining mixing water, and 5-10% can be used to prepare an aqueous solution of PowerFlow 1190 hyperplasticizer taken in an amount of 0.4 -0.8% of the total mass of cement. In the latter case, the resulting aqueous solution of PowerFlow 1190 hyperplasticizer is introduced into the fiber-reinforced concrete mixture at the last stage of its mixing. The second option is characterized by a more stable technical result, as well as an increase in the mobility of the concrete mixture. However, in both cases, the strength characteristics of concrete are improved, namely, the concrete class in terms of compressive and tensile strength, with a high degree of stability of strength indicators.

The technology for preparing fiber-reinforced concrete mix with mechanochemical activation of basalt fibers can be implemented in two versions:

1. Mixing coarse, fine aggregates and 90% of the design quantity of cement by weight in a high-speed rotary concrete mixer for 1 min until the mixture is homogeneous in a dry state. Next, mixing water in the amount of 40-50% of its design quantity is added to the dry concrete mixture and the mixture is mixed in the concrete mixer in the same mode for 2 minutes. A pre-prepared suspension of 10% of the design quantity of cement by weight, 60-50% of the design volume of mixing water (remaining) and basalt fibers in the amount of 0.4-0.6% is introduced into the mixture. Next, mix the mixture in a concrete mixer for 5 minutes.

2. After partial mixing of the dry concrete mixture, a suspension is prepared into the mixture, prepared from 55-40% of the remaining water, 10% of dry cement, and 0.4-0.6% of the total cement mass of basalt fibers. To ensure design mobility at the last stage of mixing, 5-10% of the design volume of mixing water with Power Flow 1190 hyperplasticizer dissolved in it in the amount of 0.4-0.8% of the total cement mass is added to the fiber-reinforced concrete mixture.

The method is shown in a specific example.

The basalt-fiber-reinforced concrete mixture is made from the following raw materials: Portland cement without additives Cem I 42.5N (GOST 30515-2012); sand with a fineness modulus of 2.8 mm (GOST 8736-93); crushed stone from gravel fraction 5-10 mm (GOST 31424-2010); tap water (GOST 23732-2011); basalt fiber (TU 5769-004-80104765-2008); PowerFlow 1190 hyperplasticizer (TU 5745-096-51552155-2011).

The design of the compositions of the fiber-reinforced concrete mix with the P2 mobility grade (according to GOST 7473-2010) was carried out according to the method taking into account the intergranular voidness of aggregates of the aggregates developed at the Department of SM&T of Tomsk State Autonomous Administration (Kudyakov, A.I. , S. A. Lukyanchikov // Abstracts of the All-Union conference “Basic research and new technologies in building materials science.” Part 4. The theory of artificial conglomerates and its practical significance / BTSM. - Belgorod, 1989. - P. 82). The composition of the fiber-reinforced concrete mix with basalt fibers was calculated for 1 m of concrete mix:

- Portland cement Cem I 42.5N - 335 kg / m ³ ;

- sand with a fineness modulus of 2.8 mm - 500 kg / m ³ ;

- crushed stone from gravel fraction 5-10 mm - 1340 kg / m ³ ;

- tap water - 215 kg / m ³ (100% of the volume of mixing water)

- basalt fibers in an amount of: 1.34 kg / m ³ (0.4%), 1.67 kg / m ³ (0.5%), 2.01 kg / m ³ (0.6%).

Fiber-concrete samples were made from the obtained composition, which were tested for compressive and tensile strength. For comparison, samples were prepared without the addition of basalt fibers.

In FIG. Figure 1 shows diagrams of the compressive strength R of concrete without the addition of basalt fibers (option (a)) and basalt fiber concrete (option (b)) with different contents of basalt fibers μ _bf (0.4; 0.5; 0.6). In FIG. 2 is a diagram of tensile strength of concrete R for the above concrete.

As can be seen from the diagrams, the strength of samples from a basalt-fiber-concrete mixture in comparison with base concrete of a similar composition without the addition of basalt fibers is higher by compression by 49-59%, and by tension by 27-40%. Moreover, the coefficient of variability of the strength characteristics of fiber-reinforced concrete samples did not exceed 4.1%, which indicates their satisfactory stability. An increase in the relative ultimate strain of fiber-reinforced concrete under compression to 0.0031 and tensile to 0.00014 was also recorded.

For the second option, the composition of the fiber-reinforced concrete mix with basalt fibers, similar to the previous one, was calculated, calculated on 1 m ^{3 of the} concrete mix, but with the addition of Power Flow 1190 hyperplasticizer:

- Portland cement Cem I 42.5N - 335 kg / m ³ ;

- sand with a fineness modulus of 2.8 mm - 500 kg / m ³ ;

- crushed stone from gravel fraction 5-10 mm - 1340 kg / m ³ ;

- tap water - 215 kg / m ³ (100% of the volume of mixing water)

- basalt fibers in an amount of: 1.34 kg / m ³ (0.4%), 1.67 kg / m ³ (0.5%), 2.01 kg / m ³ (0.6%).

- Power Flow 1190 hyperplasticizer in the amount of: 1.34 kg / m ³ (0.4%), 1.67 kg / m ³ (0.5%), 2.01 kg / m ³ (0.6%), 2.68 kg / m ³ (0.8%).

The strength indicators of samples prepared from a basalt-fiber-concrete mixture with the addition of hyperplasticizer, as shown by experiments, are within the same limits as in the previous version. But it was noted that the stability of the strength characteristics of these samples is higher than in the first embodiment: the coefficient of variation of the strength characteristics of fiber-reinforced concrete samples is about 2.8%.

It was also established that the fiber-reinforced concrete mixture prepared by the present method, in contrast to analogues and prototype, does not contain “hedgehogs”.

Claims (1)

A method of preparing a basalt-fiber-reinforced concrete mixture, according to which cement is first mixed in a dry form, coarse and fine aggregates, the resulting dry concrete mixture is partially mixed with water in an amount of at least 40% of the design volume of mixing water, then basalt fibers are introduced into the partially mixed concrete mixture in the amount of 0.4-0.6% of the total mass of cement and the remainder of the design volume of mixing water, after which the resulting mixture is mixed in a high-speed rotary mixer until homogeneous, characterized in that for the preparation of dry concrete mix take 90% of the design quantity of cement, dry concrete mix with water in the amount of 40-50% of the design volume of mixing water, and basalt fibers are introduced into the partially mixed concrete mix in the form of a suspension, for the preparation of which basalt the fibers are pre-mixed in a high-speed rotary mixer with the remaining 10% of dry cement and the remaining mixing water in an amount of 60-50% or in an amount of 55-40%, while 5-10% of the remaining mixing water is used for For the preparation of an aqueous solution of PowerFlow 1190 hyperplasticizer, taken in an amount of 0.4-0.8% of the total cement mass, the resulting aqueous solution of PowerFlow 1190 hyperplasticizer is introduced into the fiber-reinforced concrete mixture at the last stage of its mixing.

Images