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FIBER CONCRETE TECHNOLOGY MIXTURES BASED ON LOCAL MATERIALS
Associate professor
Ergashov J.D.
PhD., Senior lecturer
Usmanova D.A.
jasurbek_1711@mail.ru
https://doi.org/10.5281/zenodo.13922849
Abstract:
For successful application of basalt fiber concrete in monolithic construction
,
there must be an available efficient technology for frequently used compositions of such
concrete. This article presents the results of research and recommendations on efficient
technology of basalt fiber concrete.
The conducted studies allowed to establish that the introduction of basalt fiber into the
composition of heavy concrete according to the proposed technology helps to increase the
compressive strength limit by 15% compared to the same indicator of concrete without
microreinforcement. At the same time, it is possible to save cement consumption by up to 10%
or more.
Keywords:
basalt fiber concrete, basalt, fiber, testing, strength, technology, composition.
Introduction
From the results of numerous experimental and theoretical studies [1,2,3] it is known that
the process of concrete destruction under load begins with cracks at the contacts between the
cement stone and large aggregates. These cracks mainly develop along the compression forces,
but may have some deviation due to transverse expansion deformations. The destruction of the
compressed sample occurs due to the rupture of concrete in the transverse direction, first,
microcracks of separation appear, which subsequently, with increasing load, merge and form
visible cracks, leading to the destruction of the concrete sample. For high-quality splitting of
basalt fiber bundles into individual units and their uniform distribution by volume during
mixing of concrete components, a more accessible technology is needed, which can be based on
changing the order of preparation of such concrete mixtures.
An important point in the preparation of concrete mix is the correct assignment of the
ratio of components of the concrete mix, since the quality and strength of the concrete largely
depend on this.
It is recommended to mix the components of fiber concrete (binding fillers and dispersed
reinforcement) usually in forced-action concrete mixers in two stages - at the first stage, the
components of concrete in dry form are mixed for at least 3 minutes, at the second stage, after
adding water, they are also mixed for at least 3 minutes. According to the authors [ 4], this mode
allows the bundles of basalt fibers to split into individual units. The use of basalt fibers
according to this technology for preparing concrete mix at its optimal content, according to the
author, allows to increase the tensile strength of concrete in bending up to 70% or more
compared to similar indicators of concrete without dispersed reinforcement.
Materials and test methods
Ahangarancement "was used to conduct experimental studies, which meets the
requirements of GOST 10178-85 "Portland cement and slag Portland cement. Technical
conditions".
the manufacturer's data, the normal density of cement paste is 27%, the specific surface
is 3500 cm2/g. The activity of cement by strength on the day of testing is 38.5 MPa .
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from the Kuylyuk quarry, which meets the requirements of GOST 10260 [5], was used as
a large aggregate for the preparation of the concrete mixture.
from the Kuylyuk quarry, which meets the requirements of GOST 8736 [6], was used as
fine aggregate.
Basalt fiber is a section of complex basalt fiber of a given length in the form of loose
monofilaments. Basalt is produced OOO MEGA INVEST INDUSTRIAL ». Basalt fiber has the
following technical characteristics: color – bronze; density – 2.8 g/cm3
;
diameter of individual
fiber – 13-20 μm; fiber length: 5, 10, 15 and 20 mm; operating temperature from -260 to
+700°С; melting point – 1450°С; tensile strength – 45-55 Gs / tex ; resistant to acids and alkalis.
Basalt fiber concrete technology
The properties of basalt fiber provide high performance of concrete with its use, which is
associated with the modification of the concrete matrix and giving it special properties for
resistance to various aggressive influences.
When preparing a fiber concrete mixture, the fiber is introduced at the stage of production
of the concrete mixture, which acts as a reinforcing component, compatibility with all chemical
additives and rapid distribution of fibers throughout the volume of the mixture without
clumping occurs [4,8]. How this technology modifies bundles of basalt fibers into individual
fibers is not entirely clear. The fact is that when adding basalt fiber (Fig. 1)
in the almost prepared concrete mixture there are
no conditions for its splitting into separate units, since
the fibers in their original form will begin to stick to the
cement-sand mortar and form lumps. In this regard,
mechanical or other external influences are necessary to
split the bundles of basalt fibers. In this case, the bundles
of basalt fibers should split by at least 70-80%, without
damaging the properties of the fiber. It can be expected
that the surface and shape of the fibers will not be greatly
deformed by mechanical influences, which will
contribute to their uniform dispersion and adhesion to
the cement mortar. After analyzing the existing
technologies for preparing basalt fiber concrete mixture, we can draw some conclusions: it is
recommended to mix basalt fiber only when preparing concrete mixture in forced-action
mixers, there is no way to control the splitting and dispersion of fiber bundles, which in their
original state will be together with all the components of concrete, as its separate component.
As follows from the above analysis, first of all, in all likelihood, it is necessary to slightly change
the composition of basalt fiber concrete itself by adjusting the proportion of large aggregate in
the aggregate mixture, reducing its consumption, and accordingly increasing the proportion of
sand. The composition is calculated as for ordinary heavy concrete with some adjustment by
introducing a decreasing coefficient of 0.85 for the consumption of large aggregate, its volume
is replenished by increasing the consumption by introducing an increasing coefficient of 1.2 on
the calculated values of these indicators. The structure of concrete, unlike the traditional one,
allows the most complete use of the volume of intergranular voids of crushed stone for uniform
distribution of basalt fibers throughout its volume. At the same time, the efficiency of basalt
fiber concrete compositions will be determined by the appointment of the optimal grain
Fig. 1. Basalt fibers used in the
experiments
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composition of fillers, providing minimal voids due to the dense arrangement of fibers in the
composition of the cement-sand mortar of concrete.
Research results
When selecting the concrete composition, we relied on two main assumptions, based on
the structural features of heavy concrete based on Portland cement. The first is to ensure
maximum strength of the cement-sand concrete mortar with the minimum possible
consumption of large aggregate, based on the fact that after the introduction of basalt fiber, the
strength of the mortar will increase sharply and good adhesion (bondage) with large aggregate
and the required reinforcement effect will be achieved without compromising the technology
of basalt fiber concrete.
The second condition is to ensure the required mobility of the basalt fiber concrete
mixture at various frequently used binder consumption rates (350-550 kg/m3
)
and water-
cement ratio with the optimal aggregate consumption, which is determined by both the
technology and the expected concrete strength. In addition, the recommended technology for
preparing the basalt fiber concrete mixture should be based on the use of existing mixing
equipment for mixing the five-component concrete composition. A gravity mixer was used for
this purpose.
Mixing of concrete mixture in such mixers is carried out due to the action of gravity on it.
During rotation, the blades pick up, lift and throw down streams of mixture.
The basalt fiber concrete mixture was prepared in a laboratory mixer of a similar type. In
this case, unlike other technologies of such concrete, two variants of the sequence of loading
the concrete components were considered.
After testing the existing and proposed technology for preparing basalt fiber concrete
mixture, we came to the conclusion that the best method was the preliminary separate
displacement of 50% of the amount of crushed stone with fiber, introduced in 3-4 portions, as
well as another method - initially 50% of crushed stone plus 50% of sand is loaded and basalt
fiber is introduced.
The first method is to load the required amount of basalt fiber into the mixer drum after
loading 50% of the amount of crushed stone and mix it with it for 3-5 minutes. Then pour the
rest of the crushed stone and sand into the mixer. With the unit turned on, pour in water and
add cement. Continue mixing the batch until the desired consistency is achieved (about 5-7
minutes).
The second method is to load the required amount of basalt fiber into the mixer drum
after loading crushed stone and sand in an amount of 50% each and mix them together for at
least 5 minutes. Then add the remaining parts of crushed stone and sand into the mixer. With
the unit turned on, pour in water and add cement. Continue mixing until the desired consistency
is achieved (about 5-7 minutes). In this case, a two-stage modification of basalt fibers occurs.
Condition and types of basalt fiber concrete mixtures prepared using the technology described
above are shown in Fig. 2.
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Fig. 2. View of basalt fiber concrete mixture after unloading from the mixer. a -
according to the first method; b - the same, according to the second method.
From these mixtures, concrete cubes with 10 cm rib dimensions were made, which after
stripping were tested for compression in a MIG-1000 hydraulic press [7].
The composition of the concrete was determined as follows:
cement – 425 kg/m³; crushed granite fr.5-20 mm – 950 kg/m
3
; quartz sand – 815 kg/m
3
; water – 210 l/m
3
; basalt fiber 1% of the cement weight. No negative phenomena were
observed during the production of cube samples. The test results are presented in the table.
Method of
preparation -
leniya
Return of
concrete on the
day of testing,
days .
Strength of
concrete
without
additives, MPa
Strength of basalt
fiber concrete, MPa
Strength
increase, %
According to
option 1
7
14
28
22.6
26.1
30.2
25.8
30.2
34.8
14
15.8
15.2
According to
option II
7
14
28
22.6
26.1
30.2
26.4
31.0
34.2
16.8
18.7
13.2
As follows from the data in the table, in all comparable test conditions, there is an increase
in the strength of basalt fiber concrete (on average by 15%) compared to the strength of
concrete of similar compositions without basalt fibers. The increase in strength is directly
related to the introduction of basalt fibers into the concrete composition, leading to an
improvement in its structure formation during the process of cement hydration and concrete
hardening.
Technological recommendations have been developed that allow for further
improvement of other concrete compositions and development of basalt fiber concrete
production based on local materials. In order to confirm the results of laboratory studies, work
is currently underway to test them in production conditions.
Conclusions
- one of the ways to solve problems of improving the strength and durability characteristics of
concrete is to introduce basalt fibers into their composition. At present, such concretes on
cement binders have limited areas of application in load-bearing structures, despite the
technical advantages;
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- compositions and technology for producing basalt fiber concrete mixtures have been
developed, which make it possible to improve the performance of such concretes due to a more
uniform distribution of fibers throughout the volume of concrete;
- selection of basalt fiber concrete compositions with frequently used cement consumption
rates should be based on selection of concrete compositions calculated by the calculation and
experimental method based on absolute volumes with a reduction in the consumption of coarse
aggregate and adjustment of sand consumption. At the same time, its consumption rate should
not exceed the consumption rate of coarse aggregate;
- an effective technology of basalt fiber concrete should be based on the splitting of basalt fibers
at the initial stage of preparation of the mixture by mixing with half of the coarse aggregate
(first method) or with half of the coarse aggregate and half of the sand combined (second
method). With this technology it will be possible to achieve maximum splitting of basalt fibers
and their uniform distribution;
- the compressive strength of basalt fiber concrete samples manufactured using the
recommended technology, with a basalt fiber content of 1%, results in an increase in the same
characteristic by 15% compared to a composition without additives;
- the technical and technological advantages inherent in basalt fiber concrete give grounds to
conclude that this study should be continued with the aim of using basalt fiber for reinforcing
load-bearing concrete and reinforced concrete structures.
References:
1.
Berg O.Ya., Shcherbakov E.N., Pisanko G.N. High-strength concrete. Publishing house of
literature on construction. Moscow, 1971.
2.
Trofimov V.I., Fomenko S.A. Dispersed reinforcement of concrete with high-adhesion
fiber. // Collection. Science of the 21st century: experience of the past – a look into the future.
Materials of the III scientific and practical conference. - 2007, pp. 69-76.
3.
Baranov A.S. Effects of compaction pressing and dispersed reinforcement on the tensile
strength of concrete. // Science and education in transport. - 2014. pp. 287-290.
4.
Kondrashov G.M., Goldstein B.M. Basalt fiber concrete – the technology of the future. News
of Volgograd State University. Series 10, Innovative activity. Issue 7, 2012, pp. 91-92.
5.
GOST 10260-80. Crushed gravel for construction works. Technical conditions. Publishing
house of standards, Moscow, 2018, 31 p.
6.
GOST 8736-2014. Sand for construction works. Technical conditions. Standartinform,
Moscow, 8 p.
7.
GOST 10180-2012. Concrete. Methods for determining strength using control samples
Standardinform, Maskva, 2018, 31 pp.
8.
Akramov H.A., Yusupov R.R., Ergashov J.D. Features of technology and properties of
concrete using non-metallic fiber. Journal “Problems of Architecture and Construction ”. No. 1,
2023, pp. 42-45.
