CC BY
12
УДК 691.3, 691.5
EXPERIMENTAL STUDY OF THE PHYSICAL AND MECHANICAL PROPERTIES OF HIGH-STRENGTH FINE-GRAINED MODIFIED "POWDERY" CONCRETE
1 G.E. Okolnikova, 2 G.E. Grishin, 3 A.K. Kurbanmagomedov, 4 N.I. Shchedrin 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
It has now been developed and are being actively introduced the high-strength modified concretes with mineral additives with compressive strength of 80 MPa and above which are produced on an industrial scale. In this paper, the research was carried out for the high-strength fine-grained modified "powdery" concrete, which is a relatively new construction material.
Keywords:
compressive strength, tensile strength at bending, strength at axial tension, cracking moment. История статьи: Дата поступления в редакцию: 11.04.19
Дата принятия к печати: 15.04.19
The aim of the study is to determine the main physical and mechanical properties and characteristics of crack resistance of high-strength fine-grained concrete under various loading conditions.
In our study the physical and mechanical characteristics of high-strength fine-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.
As a basis for the development of the theory of strength of high-strength concrete can be used our results, which will allow to create a regulatory framework for the design and construction of structures made of high-strength concrete.
INTRODUCTION
The construction of high-rise projects, which seemed impossible decades ago, requires the use of new high-quality materials. This allows to use the best architectural and structural solutions to make the project more and more complex.
Concretes with compressive strength of more than 100 MPa have been developed and are now being actively implemented on an industrial scale [1, 2]. In recent decades, studies have been carried out on the basic physical and mechanical properties of coarse aggregates of high-strength concrete [3-4].
The behavior of high-strength concrete under tension has not been studied sufficiently, in contrast to its behavior under compression.
The researchers have not yet determined all the basic physical and mechanical characteristics of fine aggregate high-strength concrete. Also, they have little studied the much greater fragility of high-strength and ultrahigh-strength concretes, which is also very significant.
General physical and mechanical properties of high-strength concrete with modifiers (admixtures) have not been studied sufficiently, although some researchers have studied the effect of various impurities on high-strength concrete [5-6].
Determination of compressive strength, bending tensile strength, axial tensile strength, cracking moment and modulus of elasticity of modified high-strength fine-grained concrete "powder" (HSFPC) with organic-mineral admixture MB10-50C is the aim of the study. This study is a continuation of [7].
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MATERIALS AND METHODS OF RESEARCH
In this research, we studied high-strength concrete with fine aggregate, which is necessary for the construction of high-rise buildings with a compressive strength of more than 120 MPa.
To create HSFPC samples we used next composition: Portland cement of type I = 545 kg/m as the binder;
concrete modifier MB10-01 (an admixture on an organic-mineral basis containing micro-silica, fly ash, harden-
3 3
ing regulator, superplasticizer) = 115 kg/m ; river sand with a fineness modulus of 2.7 = 575 kg/m as the fine
33
aggregate; coarse aggregate is crushed granite = 995 kg/m ;water = 205 l/m .
We carried out laboratory experiment in accordance with the CIS Interstate Standard "GOST" [8-10]. Eight series of HSFPC samples with dimensions of 100x100x100 mm — and four series and 100x100x400 mm — eight series were produced. For the experiment, each series have three samples, twelve cubes and prisms, 36 samples in total. For the best curing samples were placed in air-humid condition( in water-bath with temperature of 19-22 °C).
Samples were cured for 7, 14, 28, 60 days. Then they were tested for compression and tension on a hydraulic press with a capacity of up to 5000 kN and 200 kN, respectively.
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 with 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 [9]:
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
Rct =$■
(■ b2
where 5 is the scale factor for tensile test, 5 = 0.92 for prisms with the dimensions of 100x100x400 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 [11]:
R, = R
ctf 1.75
Cracking moment was identified by the following formula [11]:
Mcrc = RCt ■ ^J
where b and h are the width and the height of the cross section of the sample accordingly. RESULTS AND DISCUSSION
Compressive strength, tensile strength in bending, strength in axial stress, moment cracking of concrete grade and modulus of elasticity are necessary physic-mechanical properties in the design of reinforced concrete structures.
We have experimentally determined, prepared by the modifier MB10-01, HSFPC's compressive strength, tensile strength in bending, strength in axial tension, the moment of cracking of a certain class and the module axial compression.
To determine the physical and mechanical properties of HCFPC, the following types of test specimens were investigated:
1. 12 cubic samples HSFPC size 100x100x100 divided into four 4 series of 3 samples to determine the compressive strength. The experimental data on compressive strength are given in table 1.
2. 12 prisms with dimensions of 100x100x400 mm divided into four 4 series of 3 samples were tested for determination of tensile strength in bending, axial strength and cracking moment. The experimental data on bending tensile strength, axial tensile strength and cracking moment are given in table 2.
Table 1.
Result of the laboratory tests of HSFPC samples of 100x100x100 mm, prepared with modifier MB10-01, on the compressive strength (cubic strength) and the concrete grade
Curing Period, Days Sample Number Failure Load on Compression, HSFPC Sample Strength Average HSFPC Samples Strength in series Rc, MPa Actual HSFPC samples Grade
F1 kN 1345 Rc, MPa 127,8
7 F2 F3 F4 1345 1313 1393 127,8 124,7 132,3 126,76 C101
14 F5 F6 F7 1440 1439 1446 136,8 136,7 137,4 135,28 C108
28 F8 F9 F10 1479 1477 1568 140,5 140,3 149,0 139,40 C112
60 F11 F12 1509 1518 143,4 144,2 145,51 C116
Table 2.
Results of the laboratory tests of HSFPC samples of 100x100x450 mm, prepared with modifier MB10-01, on the tensile strength at bending, the strength at axial tension and the cracking moment
Curing Period, Sample Number Failure Load on Tensile, Tensile Strength at Bending
Days kN R , MPa ct
P1 24,1 6,65
7 P2 24,4 6,73
P3 23,9 6,60
P4 28,3 7,81
14 P5 27 7,45
P6 24,8 6,84
Average Tensile Strength at Bending Rt , MPa
7,37
Average Strength at Axial Tension MPa
3,81
4,21
Average Cracking Moment M ,
crc
H,m 1087,48
1203,13
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Продолжение таблицы
P7 35,7 9,85
28 P8 35,4 9,77 9,87 5,64 1611,69
P9 36,2 9,99
P10 41,5 11,45
60 P11 42,7 11,79 11,15 6,37 1820,47
P12 37 10,21
Fig. 1. Shows the diagram of changes in compressive strength (cubic strength) of HSFPC depending on the curing period
Considering the diagram in Fig. 1 it can be seen that in the first 7 days of the samples life there is an active set of strength, and after 7 days the strength growth continues, but with a significantly lower speed up to 60 days.
By analyzing the experimental test data of our HSFPC samples (table 1 and Fig. 1) it was established that the compressive strength in 7 days curing reaches 125-127 MPa, and at 28 days 138-140 MPa. Therefore, for the first 7 days concrete gains 90% compressive strength from strength on the 28th day, thereby allowing at an early age to load concrete columns and walls.
After 60 days, the average compressive strength of curing reached 145.5 MPa. In comparison with the samples hardened 28 days, the strength increased by only 4%.
Fig. 2. Shows the dependency of the cracking moment on the curing period of HSFPC samples
of 100x100x450 mm
Early development of strength for high strength concrete is an important feature .The kinetics of tensile strength of samples HSFPC 100x100x450 mm in tests, axial tension and bending is shown in Fig. 3-4.
Fig. 3. Dependency of the tensile strength at bending on the curing period of HSFPC samples of 100x100x450 mm
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Fig. 4. Dependency of the strength at axial tension on the curing period of HSFPC
samples of 100x100x450 mm
In the diagram (Fig. 2-4) it can be seen that from 14 to 28 days of curing the tensile strength of HSFPC increases, but after 28 days the rate slows down. We also noted in Fig.1 and 2, that the tensile strength reaches 10.8 MPa, which is about 7.7% of the compressive strength. For reinforced concrete bending elements, such as slabs, it is necessary to know this property.
The use of MB 10-01 modifier allowed due to the high compressive strength of our HSFPS samples to achieve high resistance to chips, impact resistance, and wear resistance of the material surface.
CONCLUSION
We experimentally verified our proposed hypothesis of the process of destruction of high-strength concrete in compression.
As a basis for the development of the theory of strength of high-strength concrete can be used our results, which will allow to create a regulatory framework for the design and construction of structures made of high-strength concrete.
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REFERENCES:
1. Shanaka Kristombu Badugea Priyan Mendisa Tuan Ngoa Joanne Portellab Kate Nguyen. Understanding failure and stress-strain behavior of very-high strength concrete (>100 MPa) confined by lateral reinforcement. Construction Materials, 2018, 189: 62-77.
2. Shanaka Kristombu Baduge Priyan Mendis Tuan Ngo. Stress-strain relationship for very-high strength concrete (>100 MPa) confined by lateral reinforcement. Engineering Structures, 2018, 177: 795-808.
3. J. Pachecoa J. de Britoa C. Chastreb L. Evangelistac Experimental investigation on the variability of the main mechanical properties of concrete produced with coarse recycled concrete aggregates. Construction and Building Materials, 2019, 201: 1217-1224.
4. Karpenko N.I., Andrianov A.A. and Romkin D.S. A new approach to the description of the measures of creep and the results of its verification. Academia: Architecture& Construction, 2008, 4: 76-77.
5. Dzigita Nagrockiene, Aurelijus Daugela. Investigation into the properties of concrete modified with biomass combustion fly ash. Construction and Building Materials, 2018, 174: 369-375.
6. Nabeel A. Farhan M. Neaz Sheikh Muhammad 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 Materials, 2019, 196: 26-42
7. Okolnikova G.E., Kharun M., Tiekolo D. Effect of modifier MB10-50C on the physical and mechanical properties of high-strength fine-aggregate "powdery" concrete/ Journal of Fundamental and Applied Sciences, 9(7S), 2017, pp. 402 — 413. http://jfas.info/index.php/jfas/article/view/3337
8. GOST 24452-80. Concretes: Methods of Prismatic, Compressive Strength, Modulus of Elasticity and Poisson's Ratio Determination, Interstate Standard, Standartinform, Moscow, Russia, 2005.
9. GOST 53231-2008. Concretes: Rules for Control and Assessment of Strength, Interstate Standard, Standartinform, Moscow, Russia, 2009.
10. GOST 10180-2012. Concretes: Methods for Strength Determination using Reference Specimens, Interstate Standard, Standartinform, Moscow, Russia, 2013.
11. 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 G.E., Grishin G.E., Kurbanmagomedov A. K., Shchedrin N.I. Experimental study of the physical and mechanical properties of high-strength fine-grained modified «powdery» concrete. — Системные технологии. — 2019. — № 31. — С. 41—46.
ЭКСПЕРЕМЕНТАЛЬНОЕ ИЗУЧЕНИЕ ФИЗИЧЕСКИХ И МЕХАНИЧЕСКИХ СВОЙСТВ МОДИФИЦИРОВАННОГО ВЫСОКОПРОЧНОГО БЕТОНА С МЕЛКИМ ЗАПОЛНИТЕЛЕМ
Юкольникова Г.Э., 2Гришин Г.Е., 3Курбанмагомедов А.К., 4Щедрин Н.И.
1А4Департамент строительства, Российский университет дружбы народов (РУДН), Москва, Россия 3Кафедра математики, Московский политехнический университет, Москва, Россия
