CC BY
19
УДК 691.3, 691.5
EXPERIMENTAL STUDY OF THE MODIFIED HIGH-STRENGTH COARSE-GRAINED CONCRETE
1 G.E. Okolnikova, 2 G.E. Grishin, 3 A.K. Kurbanmagomedov, 4D.A. Bronnikov 1,2,4 Department of Civil Engineering, Peoples' Friendship University of Russia (RUDN University), Moscow, Russia
3Department of Mathematics, Moscow Polytechnic University, Moscow, Russia
Abstract
In this work the modified high-strength coarse-grained concrete with compressive strength of 80 MPa and above was selected as the core material which is increasingly used in contemporary construction, especially in high-rise buildings.
High-strength concrete is a relatively new construction material, and its physical and mechanical properties are not studied enough. The aim of the study is to determine the physical and mechanical properties under various loading conditions.
In our study the physical and mechanical characteristics of high-strength coarse-grained concrete at the ages of 7, 14, 28, 60 days have been determined, such as cubic strength, tensile strength at bending, strength at axial tensile, cracking moment, concrete grade at axial compression.
The obtained results are the basis for development of the theory of strength of high-strength concrete for creating a regulatory framework for the structural design and construction with high-strength concrete.
Keywords:
compressive strength, tensile strength at bending, strength at axial tension, cracking moment История статьи: Дата поступления в редакцию: 20.04.19
Дата принятия к печати: 22.04.19
Introduction
The actual task of present time is the creation and development of building materials with increased durability and reliability [1]. The solution of this problem is possible by creating high strength concretes, which at the same time are distinguished by higher bending strength.
The using of high strength concrete in construction is promising with economic and technological points of view. Their use, instead of the traditional heavy concrete allows to reduce the consumption of concrete itself by about 15%, and creating high-strength concrete increased crack resistance will allow reduce the reinforcement of the structure by about 10%. High strength concrete is characterized by increased durability and their maintenance life in comparison with usual concrete increases in two and more times [2]. High-strength concretes can be used in high-rise buildings as bearing constructions, for bridge construction, as well as on railway transport objects as supports for the line electricity transmissions [3-5].
But high-strength concrete is a relatively new construction material, and its physical and mechanical properties are not studied enough therefore the development of new high-strength concrete's composition providing increased crack resistance is relevant and timely.
This task is dedicated to present our study. This study is a continuation of [6-7].
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MATERIALS AND METHODS OF RESEARCH
In the case of this study, as the main research material selected modified high-strength concrete with coarse aggregate, with a compressive strength of more than 80 MPa, which is increasingly used in modern construction, especially in high-rise buildings. The study of HSCAC had the following composition: Binder is portland cement of type I = 450 kg/m ; concrete modifier MB10-50C (on an organic- mineral basis an admixture consisted
3
of micro-silica, fly ash, hardening regulator, superplasticizer) = 100 kg/m ; fine aggregate is sand with a fine-
33
ness modulus of 2.7 = 750 kg/m ; coarse aggregate is crushed granite with fraction of 5-15 mm = 960 kg/m ; 3
water = 160 l/m .
All HSCAC samples were made from one concrete batches.
The Laboratory experiment was conducted in accordance with the CIS Interstate Standard "GOST" [8-9]. 8 series of test samples were produced in total:
1) 6 series — 100x100x100 mm
2) 4 series — 100x100x450 mm
Each series have 3 samples. 12 samples in each type, 24 samples summary. For the research we applied:
Compression machine for measuring cubic strength of concrete with compression force up to 5000KN. Bending machine for measuring tensile strength at bending, strength at axial tension and cracking moment with bending force up to 200KN
Ultra sonic wave device for measuring elastic modulus. Samples were tested at the curing periods of 7, 14, 28, 60 days Compressive strength was identified by the following formula [10]:
F
Rc =a- — c A
where a is the scale factor on compression test, a = 0.95 for cubes of the dimensions of 100x100x100 mm; Fc is the failure load on compression; A is the surface area of the sample. The concrete grade was identified by the formula [24]:
Cf = 0.8 Rtc
where Rt is the actual concrete strength according to the test data, Rt = Rc-a. Tensile strength at bending was identified by the following formula [10]:
F ■ l
Ro =§■ F l
ct ,2
a ■ b
where 5 is the scale factor for tensile test, 5 = 0.92 for prisms of the dimensions of 100x100x450 mm; Ft is the failure load on tensile; l is the distance between supports during sample testing; a and b are the width and the height of the cross section of the sample accordingly.
Strength at axial tension was identified by the formula [10]:
R, = R
ctf 1.75
Cracking moment was identified by the following formula [10]:
RESULTS AND DISCUSSION
Compressive strength, tensile strength at bending, strength at axial tension, cracking moment and concrete grade are the most important physical and mechanical properties of. In the construction applicability of HSCAC depends on these characteristics.
In the case of this study we determinate prepared with modifier MB10-50C HSCAC's compressive strength, tensile strength at bending, strength at axial tension, cracking moment and concrete grade at axial compression.
The following types of test specimens were investigated to determine the physical and mechanical properties of HSCAC:
1. The series of the HSCAC samples of 100x100x100 mm of cube shape were tested to determine the compressive strength (cubic strength) and the concrete grade. This series was numbered as F1, F2, F3, ..., F12. The results of experimental study of compressive strength and HSCAC grade are shown in the tables 1.
2. Four series of the HSCAC samples of 100x100x450 mm of prism shape were tested to determine the tensile strength at bending, the strength at axial tension, and the cracking moment. This series was numbered as P1, P2, P3, ..., P12. The results of study are shown in the table 2.
Fig. 1 shows the diagram of changes in compressive strength (cubic strength) of HSCAC depending on the curing period.
Fig. 1 reflects the strength growth in HSCAC samples is uniform, smooth and have no jumps or changes.
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Table 1.
Result of the laboratory tests of HSCAC samples of 100x100x100 mm, prepared with modifier MB10-50C, on the compressive strength (cubic strength) and the concrete grade
Curing Period, Days Sample Number F1 Failure Load on Compression, kN 679 HSFPC Sample Strength Rc, MPa 64.5 Average HSFPC Samples Strength in series Rc, MPa Actual HSFPC samples Grade
7 F2 F3 F4 641 598 795 60.9 56.8 75.5 60.75 С49
14 F5 F6 F7 767 755 841 72.8 71.8 79.9 73.36 С59
28 F8 F9 F10 821 735 870 78.0 69.9 82.6 75.90 С61
60 F11 F12 F10 846 810 934 80.4 77.0 88.7 80.00 С64
120 F11 F12 F10 866 869 953 82.3 82.5 90.5 84.50 С68
180 F11 F12 946 897 89.9 85.2 88.55 С71
Compressive strength of HSCAC samples 7 days of curing which is about 70% of the compressive strength of 28 days curing period.
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0 10 20 30 40 50 60 70 80 90 100 110120 130140 150 160 170 180 190
Curing Period, days
Fig. 1. Compressive strength (cubic strength) of HSCAC depending on the curing period of HSCAC samples of 100x100x100 mm
Table 2.
Results of the laboratory tests of HSCAC samples of 100x100x450 mm, prepared with modifier MB10-50C, on the tensile strength at bending, the strength at axial tension and the cracking moment
Average
Curing Failure Load Tensile Strength Average Tensile Average Strength Cracking
Period, Sample Tvlnmhpr on Tensile, at Bending Rct, Strength at Bend- at Axial Tension Moment
IN U111UC1 MPa c ing Rct , MPa Rcf MPa M , crc7
Days kN H,m
P1 19.7 5.43
7 P2 17.6 4.85 5.38 3.07 877.69
P3 21.2 5.85
P4 22.5 6.21
14 P5 20.0 5.53 5.72 3.27 933.88
P6 19.6 5.41
P7 23.0 6.34
28 P8 21.0 5.80 5.81 3.32 948.95
P9 19.2 5.30
P10 23.1 6.39
60 P11 25.4 7.02 6.46 3.69 1053.94
P12 21.6 5.95
Fig. 2 shows the dependency of the cracking moment on the curing period of HSCAC samples of 100x100x450 mm. Diagram's analyzing (Fig. 2) shows that after 14 days of curing cracking moment features are decreased.
Fig. 2. Dependency of the cracking moment on the curing period of HSCAC samples of 100x100x450 mm
Early development of strength is an important feature of high-strength concrete. Diagrams in Fig. 3 U
and Fig. 4 shows the tensile strength Kinetics of HSCAC samples in bending and axial tension tests of ^
100x100x450 mm Û
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Fig. 3. Dependency of the tensile strength at bending on the curing period of HSCAC samples of
100x100x450 mm
Fig. 4. Dependency of the strength at axial tension on the curing period of HSCAC
samples of 100x100x450 mm
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Thank to tests of HSCAC samples (Table 2, Fig. 3 and Fig. 4) we detected that tensile strength in 28 days of curing can reach about 7.7% of compressive strength what is 5,3-6,34 MPa. For structures such as slabs this feature is very necessary to while loading.
Tests also show that samples have resistance to chipping, impact resistance, and a high abrasion resistance of the material surface due to the high compressive strength.
CONCLUSION
The obtained results are the basis for development of the theory of strength of high-strength concrete using the methods of destruction mechanics, and also for creating a regulatory framework for the structural design and construction with high-strength concrete.
REFERENCES:
1. P. CAitcin. The durability characteristics of high performance concrete: a review. Cement and Concrete Composites 25, 2003, 25: 409-420
2. Nabeel A. Farhan M. NeazSheikhMuhammad N.S.Hadi. Investigation of engineering properties of normal and high strength fly ash based geopolymer and alkali-activated slag concrete compared to ordinary Portland cement concrete. Construction and Building Materials, 2019, 196: 26-42.
3. Kovacevic, Ilda & Dzidic. HIGH-STRENGTH CONCRETE (HSC)-MATERIAL FOR HIGH-RISE BUILDINGS. Sanin.
4. Niyazi OzgurBezgin. High performance concrete requirements for prefabricated high speed railway sleepers. Construction and Building Materials, 2017, 138: 340-351.
5. M. Iordachescu A. ValienteM.De Abreu. Fatigue life assessment of a tack welded high-strength wire mesh for reinforcement of precast concrete bridge girders. Construction and Building Materials, 2019, 197: 421-427.
6. Okolnikova G.E., Kharun M., Tiekolo D. Effect of modifier MB10-01 on the physical and mechanical properties of high-strength coarse-aggregate concrete/Journal of Fundamental and Applied Sciences, 9(7S), 2017, pp. 391 — 401. http://jfas.info/ index.php/jfas/article/view/3336
7. Okolnikova G.E., Kharun M. Effect of Modifier Mb10-01 on the Parameters of Fracture Mechanics of High-Strength Coarse-Aggregate Concrete/ Journal of Fundamental and Applied Sciences, 10(3S), 2018, pp. 592 — 605. http://jfas.info/ index.php/jfas/article/view/3951
8. GOST 53231-2008. Concretes: Rules for Control and Assessment of Strength, Interstate Standard, Standartinform, Moscow, Russia, 2009.
9. GOST 10180-2012. Concretes: Methods for Strength Determination using Reference Specimens, Interstate Standard, Standartinform, Moscow, Russia, 2013.
10. Regulation Code 63.13330.2012. Concrete and Reinforced Concrete Structures. Ministry of Construction of Russia, Moscow, Russia, 2015.
Просьба ссылаться на эту статью следующим образом:
Okolnikova Galina E., Grishin G.E., Kurbanmagomedov A. K., Bronnikov D.A. Experimental study of the modified high-strength coarse-grained concrete. — Системные технологии. — 2019. — № 31. — С. 25—30.
ЭКСПЕРИМЕНТАЛЬНОЕ ИЗУЧЕНИЕ МОДИФИЦИРОВАННОГО ВЫСОКОПРОЧНОГО БЕТОНА С КРУПНЫМ ЗАПОЛНИТЕЛЕМ
'Окольникова Г.Э., 2Гришин Г.Е., 3Курбанмагомедов А.К., 4Бронников Д.А.
1А4 Департамент строительства, Российский университет дружбы народов (РУДН), Москва, Россия 3Кафедра математики, Московский политехнический университет, Москва, Россия
Ключевые слова:
прочность на сжатие, прочность на растяжение при изгибе, прочность при осевом растяжении, момент трещинообразования. Date of receipt in edition: 20.04.19 Date of acceptance for printing: 22.04.19
Аннотация
В данной работе в качестве основного материала был выбран модифицированный высокопрочный крупнозернистый бетон с прочностью на сжатие 80 МПа и выше, который все чаще используется в современном строительстве, особенно в высотных зданиях. Высокопрочный бетон является относительно новым строительным материалом, и его физико — механические свойства изучены недостаточно.
Целью исследования является определение физико-механических свойств при различных условиях нагружения.
В нашем исследовании определены физико-механические характеристики высокопрочного крупнозернистого бетона в возрасте 7, 14, 28, 60 дней, такие как кубиковая прочность, прочность на растяжение при изгибе, прочность при осевом растяжении, момент трещинообразования, класс бетона при осевом сжатии.
Полученные результаты являются основой для разработки теории прочности высокопрочного бетона для создания нормативной базы для проектирования и строительства конструкций из высокопрочного бетона.
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УДК 691.3, 691.5
СЦЕПЛЕНИЕ БЕТОНА С БАЗАЛЬТОПЛАСТИКОВОЙ АРМАТУРОЙ И ИССЛЕДОВАНИЕ СВОЙСТВ БАЗАЛЬТОПЛАСТИКОВОЙ АРМАТУРЫ
!Г.Э. Окольникова, 2Р.Х. Нурхонов, 3Йен Кунно, 4А.К. Курбанмагомедов
1,2,3 Департамент строительства, Российский университет дружбы народов (РУДН),
Москва, Россия
4Кафедра математики, Московский политехнический университет, Москва, Россия
Аннотация
В нашей статье мы рассматриваем преимущество и недостатки композитной арматуры, область применения композитных арматур, причисляем сравнительные характеристики композитной и металлической арматуры, процесс производства базальтопласти-ковой и стеклопластиковой арматуры, даем определение композитной и базальтопластиковой арматуре, а также рассмотрим анализ стойкости высокопрочной стальной и стеклопластиковой арматуры в агрессивных средах.
Ключевые слова:
композитная арматура, стекло-пластиковая арматура, ба-зальтопластиковая арматура, прочность, преимущество и недостатки композитной арматуры, область применения композитной арматуры. История статьи:
Дата поступления в редакцию: 11.05.19
Дата принятия к печати: 15.05.19
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