scholarly journals Examining the Distribution of Strength across the Thickness of Reinforced Concrete Elements Subject to Sulphate Corrosion Using the Ultrasonic Method

Materials ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 2519 ◽  
Author(s):  
Bohdan Stawiski ◽  
Tomasz Kania
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Chemical Reactions ◽  
Cross Sections ◽  
Ultrasonic Method ◽  
Concrete Strength ◽  
Corrosive Environment ◽  
Standard Samples ◽  
Actual Distribution ◽  
Initial Strength

Sulphate corrosion of concrete is a complex chemical and physical process that leads to the destruction of construction elements. Degradation of concrete results from the transportation of sulphate compounds through the pores of exposed elements and their chemical reactions with cementitious material. Sulphate corrosion can develop in all kind of structures exposed to the corrosive environment. The mechanism of the chemical reactions of sulphate ions with concrete compounds is well known and described. Furthermore, the dependence of the compressive strength of standard cubic samples on the duration of their exposure in the sulphate corrosion environment has been described. However, strength tests on standard samples presented in the scientific literature do not provide an answer to the question regarding the measurement methodology and actual distribution of compressive strength in cross-section of reinforced concrete structures exposed to sulphate ions. Since it is difficult to find any description of this type of test in the literature, the authors undertook to conduct them. The ultrasonic method using exponential heads with spot surface of contact with the material was chosen for the measurements of concrete strength in close cross-sections parallel to the corroded surface. The test was performed on samples taken from compartments of a reinforced concrete tank after five years of operation in a corrosive environment. Test measurements showed heterogeneity of strength across the entire thickness of the tested elements. It was determined that the strength of the elements in internal cross-sections of the structure was up to 80% higher than the initial strength. A drop in the mechanical properties of concrete was observed only in the close zone near the exposed surface.

scholarly journals Tests of Concrete Strength across the Thickness of Industrial Floor Using the Ultrasonic Method with Exponential Spot Heads

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2118 ◽  
Author(s):  
Bohdan Stawiski ◽  
Tomasz Kania
Keyword(s):  
Compressive Strength ◽  
Cross Section ◽  
Cross Sections ◽  
Ultrasonic Method ◽  
Concrete Strength ◽  
Testing Machine ◽  
Cross Section Area ◽  
Section Area ◽  
Strength Result

The accepted methods for testing concrete are not favorable for determining its heterogeneity. The interpretation of the compressive strength result as a product of destructive force and cross-section area is burdened with significant understatements. It is assumed erroneously that this is the lowest value of strength at the height of the tested sample. The top layer of concrete floors often crumble, and the strength tested using sclerometric methods does not confirm the concrete class determined using control samples. That is why it is important to test the distribution of compressive strength in a cross-section of concrete industrial floors with special attention to surface top layers. In this study, we present strength tests of borehole material taken from industrial floors using the ultrasonic method with exponential spot heads with a contact surface area of 0.8 mm2 and a frequency of 40 kHz. The presented research project anticipated the determination of strength for samples in various cross-sections at the height of elements and destructive strength in the strength testing machine. It was confirmed that for standard and big borehole samples, it is not possible to test the strength of concrete in the top layer of the floor by destructive methods. This can be done using the ultrasonic method. After the analysis, certain types of distributions of strength across concrete floor thickness were chosen from the completed research program. The gradient and anti-gradient of strength were proposed as the new parameters for the evaluation of floor concrete quality.

Analysis of the Impact of Concrete Compressive Strength Reduction in Joint Core Area on Super High-Rise Structures

2013 ◽  
Vol 438-439 ◽  
pp. 690-695
Author(s):  
Xiao Yu ◽  
Na Wu ◽  
Zhao Yang ◽  
Kai Xu
Keyword(s):  
Compressive Strength ◽  
Cross Sections ◽  
Concrete Strength ◽  
Nonlinear Finite Element ◽  
Core Area ◽  
Concrete Compressive Strength ◽  
Element Analysis ◽  
High Rise ◽  
The Impact ◽  
Joint Core Area

t is focused on a super high-rise building structure, of which the concrete compressive strength is reduced in joint core. The whole structure is calculated with program SATWE. Based on this calculation, integral stress analysis by MIDAS when concrete strength is reduced in joint core area and nonlinear finite element analysis by ANSYS on the joints of the worst cross-sections in the whole structure are developed. Thus the adverse effect of reduced concrete strength in joint core area on super high-rise structures is found out.

scholarly journals Application of the maturity method to reinforced concrete roof slabs

2021 ◽  
Vol 26 (4) ◽  
Author(s):  
Roberto Luiz Curra ◽  
Fernanda Pacheco ◽  
Hinoel Zamis Ehrenbring ◽  
Roberto Christ ◽  
Jeferson Ost Patzlaff ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Low Temperature ◽  
Concrete Structure ◽  
Concrete Strength ◽  
Southern Brazil ◽  
Reinforced Concrete Structure ◽  
Industrial Construction ◽  
Maturity Method ◽  
Hardened State

ABSTRACT The maturity method is a procedure that associates the evolution of the temperature of concrete cast to the structure and the evolution of its hardened state properties like compressive strength, usually at early ages. Its use is justified when safety and agility are required for activities like prestressing, shoring removal, demolding and low temperature concrete curing analysis. Temperate regions are known for having lower temperatures during the winter, which can delay concrete strength gains. The aim of this study was to apply the maturity method to a reinforced concrete structure located in Southern Brazil in industrial construction. It was noted that the concrete, despite being expected to reach 30 MPa at 28 days, managed to reach 70% of the strength at 8.5 days for slab 1. Slab 2, whose function was to support garners 4, 5 and 6, presented the data at 4.4 days, it being possible to measure such property using the maturity method.

scholarly journals NGHIÊN CỨU THIẾT KẾ TĂNG CƯỜNG KHẢ NĂNG CHỊU UỐN SÀN BÊ TÔNG CỐT THÉP BẰNG VẬT LIỆU TẤM SỢI FRP DÁN NGOÀI

2021 ◽  
Vol 5 (1) ◽  
pp. 2330-2341
Author(s):  
Nguyễn Thị Thanh ◽  
Phạm Việt Hùng ◽  
Ngô Quý Tuấn ◽  
Lê Minh Đức ◽  
Nguyễn Trường Giang
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Concrete Strength ◽  
Fiber Reinforced Polymer ◽  
Concrete Slabs ◽  
Fiber Reinforced ◽  
Flexural Strengthening ◽  
Reinforced Concrete Slabs ◽  
Reinforced Polymer ◽  
Calculation Results

Phương pháp tăng cường khả năng chịu uốn của kết cấu sàn bê tông cốt thép sử dụng vật liệu tấm sợi FRP (Fiber Reinforced Polymer) dán ngoài đã trở nên phổ biến, vì những ưu điểm của chúng mang lại như cường độ chịu kéo cao, trọng lượng nhẹ, cách điện, cách nhiệt tốt, bền theo thời gian. Bài báo trình bày quy trình thiết kế tăng cường khả năng chịu uốn của sàn bê tông cốt thép gia cường bằng tấm sợi FRP dán ngoài để đảm bảo yêu cầu khai thác và khảo sát hiệu quả tăng cường tương ứng với các cấp cường độ chịu nén của bê tông theo hướng dẫn ACI 440.2R-17. Kết quả tính toán theo trình tự đề nghị giúp chọn và kiểm tra được diện tích tấm FRP tăng cường cần thiết. Ngoài ra, kết quả tính toán chỉ ra rằng mức độ tăng cường khả năng chịu uốn của sàn tỷ lệ thuận với cường độ chịu nén của bê tông, tương ứng với cường độ bê tông tăng từ 11,5 MPa đến 19,5 MPa, sức kháng uốn tính toán tăng từ 91%  đến 144%. Đồng thời, kết quả cũng cho thấy rằng sự phá hoại của sàn bê tông cốt thép xảy ra do mất dính bám giữa lớp FRP gia cường khỏi bề mặt cấu kiện là chủ yếu. ABSTRACT The method of the flexural strengthening of reinforced concrete slabs using the externally bonded FRP (fiber reinforced polymer) laminates has become popular because of their advantages as high tensile strength, large modulus of elasticity, lightweight, high abrasion resistance, electrical insulation, good heat resistance and durable over the time. The paper presented the design procedure for the flexural strengthening of reinforced concrete slabs with FRP laminates to ensure the mining requirements and investigation of the reinforcement efficiency corresponding to the compressive strength levels of concrete based on ACI 440.2R-17. Calculation results in the suggested sequence helped select and check the required reinforcement FRP areas. In addition, the calculation results showed that the degree of increased flexural strengthening of the slabs was proportional to the compressive strength of the concrete, corresponding to the concrete strength increased from 11,5 MPa to 19,5 MPa, flexural strengthening increases from 91% to 144%. Moreover, the damage to the reinforced concrete slabs was caused by the debonding between the FRP and the surface of the structures.

Sodium Sulfate Corrosion of Polypropylene Concrete Strength Curve of Impact Study

2015 ◽  
Vol 1094 ◽  
pp. 265-268
Author(s):  
Chang Zheng Sun ◽  
Fan Fan Zhu ◽  
Ying Dong Lin
Keyword(s):  
Compressive Strength ◽  
Sodium Sulfate ◽  
Ultrasonic Method ◽  
Concrete Strength ◽  
Sulfate Solution ◽  
Strength Test ◽  
Test Block ◽  
The Press ◽  
Compressive Strength Test ◽  
Real Value

Using ultrasonic method for various corrosion instars of clear water, sodium sulfate solution corrosion respectively after block of NDT, polypropylene mortar test results calculated according to the theory of strength. Through the press again the compressive strength test, it is concluded that polypropylene mortar test block intensity of real value[4]. Through the press again the compressive strength test, it is concluded that polypropylene mortar test block intensity of real value.

scholarly journals THE EFFECT OF HIGH TEMPERATURE ON REINFORCED CONCRETE STRUCTURES

2010 ◽  
Vol 2 (1) ◽  
pp. 12-21 ◽  
Author(s):  
Robertas Zavalis ◽  
Arnoldas Šneideris
Keyword(s):  
Reinforced Concrete ◽  
High Temperature ◽  
Cross Sections ◽  
Concrete Strength ◽  
Temperature Fields ◽  
Concrete Element ◽  
Zone Method ◽  
Standard Fire ◽  
Fire Curve ◽  
Zone Dimension

The article represents the behaviour of reinforced concrete and its components (concrete and reinforcement) under high temperature. The comparing analysis of the experimentally and theoretically obtained results has been performed. The carried out experiment has disclosed that the mechanical properties of concrete alters differently in cases of temperature rise and theoretical reference. The most visible difference has been noticed at a temperature of 100 °C (Fig 4, Fig 5). The main fire resistance calculation basics are discussed. The temperature fields of the reinforced concrete element cross-section are calculated according to the standard fire curve using the program COSMOS/M of the finite element method. Concrete thermal properties, thermal conductivity and specific heat capacity dependence on temperature are taken into account in the model (Fig 10, Fig 11). By means of this model, the corresponding algorithm (Table 2) was made and can be used for obtaining temperature distribution for the reinforced concrete element of different cross-sections. According to the received temperature fields and applying the zone method, the influence of differences in theoretical and experimental results on element load bearing capacity is determined. The residual strength of the element considering the theoretical reduction curve of concrete strength is 5% larger than the results obtained in cases of 30 and 60 minutes heating. 90 and 120 minutes heating indicates that element strength is only 2% larger than the results calculated experimentally. The reduced zone dimension determined due to a decrease in the reduction coefficient at a temperature of 100 °C has affected residual element strength.

scholarly journals Experimental Study on the Mechanical Properties of Amorphous Alloy Fiber-Reinforced Concrete

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Chaohua Jiang ◽  
Yizhi Wang ◽  
Wenwen Guo ◽  
Chen Jin ◽  
Min Wei
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Reinforced Concrete ◽  
Amorphous Alloy ◽  
Flexural Strength ◽  
Concrete Strength ◽  
Splitting Tensile Strength ◽  
Fiber Reinforced Concrete ◽  
Fiber Reinforced

With great mechanical properties and corrosion resistance, amorphous alloy fiber (AAF) is a highly anticipated material in the fiber-reinforced concrete (FRC) field. In this study, the mechanical properties of AAFRC such as compressive strength, tensile strength, and flexural strength were examined. The comparison and analysis between AAFRC and steel fiber-reinforced concrete (SFRC) were also carried out. The results show that adding fibers significantly improves the concrete strength and toughness index. Compared with plain concrete, the compressive strength, splitting tensile strength, and flexural strength of AAFRC increase by 8.21–16.72%, 10.4–32.8%, and 18.12–45.21%, respectively. Meanwhile, the addition of AAF with a greater tensile strength and larger unit volume quantity improves the splitting tensile strength and flexural strength of concrete more noticeably than that of SF. Adding AAF improves the ductility of concrete more significantly in comparison to the SF. AAFRC shows great interfacial bonding performance as well. A prediction equation for the strength of AAFRC was proposed, which verified good accuracy calibrated based on the test results.

Monte Carlo Simulation of the Torsional Strength due to Concrete Compression of Reinforced Concrete Element

2015 ◽  
Vol 797 ◽  
pp. 27-34 ◽  
Author(s):  
Roman Jaskulski ◽  
Piotr Wiliński
Keyword(s):  
Compressive Strength ◽  
Monte Carlo ◽  
Reinforced Concrete ◽  
Cross Sections ◽  
Safety Margin ◽  
Strength Distribution ◽  
Distribution Functions ◽  
Concrete Compressive Strength ◽  
Concrete Element ◽  
Torsional Resistance

The aim of the work was to assess the safety margin of reinforced concrete element of rectangular cross-sections subjected to torsion. In the performed analyses two models of torsional resistance based on concrete compressive strength was taken into account. Assessment was performed with use of Monte Carlo method. Utilized models of shear resistance were taken from formerly used Polish standards: PN-84/B-03264, PN-B-03264:2002 and the actual Polish standard EN-1992-1-1:2004. From the same standards necessary assumptions related with the models were taken. The safety margin and influence of the differences in assumptions on the obtained results were analyzed. The selected models was also evaluated in terms of their “sensitivity” to changes of basic parameters of distribution functions of selected random variables. Results showed that average torsional resistance differs of about 50% times depending of assumed model. The reliability level, measured with the partial reliability exponent ΔR, differs of 10% if different models are concerned but the differences are much higher (up to 5 times, when the standard deviation of concrete compressive strength distribution changes).

scholarly journals Assessment of ultimate drift capacity of RC shear walls by key design parameters

2017 ◽  
Vol 50 (4) ◽  
pp. 482-493 ◽  
Author(s):  
Chanipa Netrattana ◽  
Rafik Taleb ◽  
Hidekazu Watanabe ◽  
Susumu Kono ◽  
David Mukai ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Cross Sections ◽  
Axial Load ◽  
Concrete Strength ◽  
Shear Walls ◽  
Load Ratio ◽  
Design Parameters ◽  
Seismic Behaviour ◽  
Drift Capacity ◽  
Axial Load Ratio

The latest version of the Standard for Structural Calculation of Reinforced Concrete Structures, published by the Architectural Institute of Japan in 2010 [1], allows the design of shear walls with rectangular cross sections in addition to shear walls with boundary columns at the end regions (referred to here as “barbell shape”). In recent earthquakes, several reinforced concrete (RC) shear walls were damaged by flexural failures through concrete compression crushing accompanied with buckling of longitudinal reinforcement in the boundary areas. Damage levels have clearly been shown to be related to drift in structures; this is why drift limits are in place for structural design criteria. A crucial step in designing a structure to accommodate these drift limits is to model the ultimate drift capacity. Thus, in order to reduce damage from this failure mode, the ultimate drift capacity of RC shear walls needs to be estimated accurately. In this paper, a parametric study of the seismic behaviour of RC shear walls was conducted using a fibre-based model to investigate the influence of basic design parameters including concrete strength, volumetric ratio of transverse reinforcement in the confined area, axial load ratio and boundary column dimensions. This study focused on ultimate drift capacity for both shear walls with rectangular sections and shear walls with boundary columns. The fibre-based model was calibrated with experimental results of twenty eight tests on shear walls with confinement in the boundary regions. It was found that ultimate drift capacity is most sensitive to axial load ratio; increase of axial load deteriorated ultimate drift capacity dramatically. Two other secondary factors were: increased concrete strength slightly reduced ultimate drift capacity while increased shear reinforcement ratio and boundary column width improved ultimate drift capacity.

Effect of combined drink cans and steel fibers on the impact resistance and mechanical properties of concrete

2020 ◽  
Vol 14 (2) ◽  
pp. 6734-6742
Author(s):  
A. Syamsir ◽  
S. M. Mubin ◽  
N. M. Nor ◽  
V. Anggraini ◽  
S. Nagappan ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Reinforced Concrete ◽  
Impact Resistance ◽  
Fiber Reinforced Concrete ◽  
Steel Fibers ◽  
Fiber Reinforced ◽  
Indirect Tensile ◽  
The Impact

This study investigated the combine effect of 0.2 % drink cans and steel fibers with volume fractions of 0%, 0.5%, 1%, 1.5%, 2%, 2.5% and 3% to the mechanical properties and impact resistance of concrete. Hooked-end steel fiber with 30 mm and 0.75 mm length and diameter, respectively was selected for this study.  The drinks cans fiber were twisted manually in order to increase friction between fiber and concrete. The results of the experiment showed that the combination of steel fibers and drink cans fibers improved the strength performance of concrete, especially the compressive strength, flexural strength and indirect tensile strength. The results of the experiment showed that the combination of steel fibers and drink cans fibers improved the compressive strength, flexural strength and indirect tensile strength by 2.3, 7, and 2 times as compare to batch 1, respectively. Moreover, the impact resistance of fiber reinforced concrete has increase by 7 times as compared to non-fiber concretes. Moreover, the impact resistance of fiber reinforced concrete consistently gave better results as compared to non-fiber concretes. The fiber reinforced concrete turned more ductile as the dosage of fibers was increased and ductility started to decrease slightly after optimum fiber dosage was reached. It was found that concrete with combination of 2% steel and 0.2% drink cans fibers showed the highest compressive, split tensile, flexural as well as impact strength.    

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