Crack Formation and Strength of Fire Damaged Concrete Beam

2012 ◽  
Vol 166-169 ◽  
pp. 1121-1126
Author(s):  
Worapong Srisoros ◽  
K Kaewpetch ◽  
P Ariyasuk ◽  
A Chokcharoenmahasarn
Keyword(s):  
Main Crack ◽  
Concrete Beam ◽  
Crack Formation ◽  
Cement Clinker ◽  
Hydration Reaction ◽  
Spring Model ◽  
Material Models ◽  
Strength Capacity ◽  
Mesh Material ◽  
Heated Specimen

The Rigid-Body-Spring-Model was applied for analyzing fire-damaged concrete beam with voronoi random mesh. Material models of fire-damaged concrete was defined by the experiment. To evaluate the performance and effectiveness of the RBSM with voronoi random mesh, four models of fire damaged concrete beam at various temperatures covered 20°C and 100 to 800°C were analyzed. According to the results, heated specimen 800°C has the lowest strength capacity and internal stress comparing to the other specimens. Main crack of 800°C specimen appears earlier than other specimens. Strength capacity of heated specimen 400°C was higher than the results of unheated specimen because of hydration reaction of large cement clinker was accelerate during heating.

Regularities of main crack formation in heterogeneous materials

2020 ◽  
Author(s):  
Ekaterina Damaskinskaya ◽  
Vladimir Hilarov ◽  
Ivan Panteleev ◽  
Dmitry Korost
Keyword(s):  
Main Crack ◽  
Crack Formation ◽  
Heterogeneous Materials

scholarly journals Experimental Study on the Concrete with Compound Admixture of Iron Tailings and Slag Powder under Low Cement Clinker System

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Ruidong Wu ◽  
Juanhong Liu
Keyword(s):  
Diffusion Coefficient ◽  
Mineral Admixture ◽  
Chloride Diffusion ◽  
Cement Clinker ◽  
Hydration Reaction ◽  
Chloride Diffusion Coefficient ◽  
Carbonation Depth ◽  
Mixture Ratio ◽  
Slag Powder ◽  
Powder Content

In order to study the performance of concrete with compound admixture of iron tailings and slag powder under low cement clinker system, the mixture ratio of different iron tailings powder and slag powder was designed to prepare C30 and C50 concrete. The workability, strength, carbonation depth, chloride diffusion coefficient, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) of concrete were measured, respectively. The test results show that iron tailings powder is beneficial to improve the workability, and the strength of concrete decreases with the increase of iron tailings powder content, while the carbonation depth and chloride diffusion coefficient increase with the increase of iron tailings powder content. Under low cement clinker system, the iron tailings powder should not be used alone (below 70% of mineral admixture). When the ratio of iron tailings to slag powder is 1 : 1, the strength, carbonation depth, chloride ion permeation coefficient, and the microstructure of concrete are roughly the same to that of concrete with single slag powder. So, the iron tailings powder can replace S95 grade slag powder in the same quantity. Iron tailings powder does not take part in hydration reaction, but it can improve particle gradation, reach close accumulation, and increase the quantity of central grains.

The Activation of Steel Slag and its Application in Construction and Building Materials

2014 ◽  
Vol 884-885 ◽  
pp. 702-705 ◽  
Author(s):  
Lan Lan Li ◽  
Feng Qing Zhao ◽  
Shao Jie Liu
Keyword(s):  
Building Materials ◽  
Steel Slag ◽  
Concrete Block ◽  
Cement Clinker ◽  
Research Progress ◽  
Hydration Reaction ◽  
Crude Steel ◽  
Volume Stability ◽  
Industrial Solid Waste ◽  
Combined Use

Steel slag as the discharged residue during steelmaking process is a kind of industrial solid waste, accounting for about 15 to 20 percent of crude steel in production. Steel slag is mainly similar with cement clinker in mineral and chemical composition, and possesses potential hydration reaction activity. The properties of steel slag, the research progress of activation and volume stability were summarized in this paper. Several approaches of steel slag utilization in construction and building materials were introduced. The combined use of various activation methods and proper treatment will increase the volume of steel slag in autoclaved tailings bricks and aerated concrete block.

Evaluation of Crack Formation in Concrete and Basalt Specimens under Cyclic Uniaxial Load Using Acoustic Emission and Computed X-Ray Tomography

2016 ◽  
Vol 722 ◽  
pp. 247-253 ◽  
Author(s):  
Alexander N. Kravcov ◽  
Pavel Svoboda ◽  
Adam Konvalinka ◽  
Elena B. Cherepetskaya ◽  
Ivan E. Sas ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Main Crack ◽  
Crack Formation ◽  
Acoustic Emission Activity ◽  
X Ray ◽  
Stress Memory ◽  
Uniaxial Load ◽  
Computed Microtomography ◽  
Emission Activity ◽  
X Ray Computed

The paper discusses the use of acoustic emission, stress-memory effect, and X-ray computed microtomography (μST) to detect the onset of destruction of specimens of concrete and basalt which are widely used in construction. It is shown that the most informative parameter is acoustic emission activity based on which the onset of the formation of a main crack can be identified. The geometry of the crack is determined using computed X-ray tomography.

scholarly journals Mechanical Performance Evaluation of Concrete Beams Strengthened with Carbon Fiber Materials

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Jun Ding ◽  
Xia Huang ◽  
Gang Zhu ◽  
Song Chen ◽  
Guochao Wang
Keyword(s):  
Carbon Fiber ◽  
Crack Propagation ◽  
Crack Resistance ◽  
Main Crack ◽  
Concrete Beam ◽  
Mechanical Performance ◽  
Concrete Beams ◽  
Loading Capacity ◽  
Externally Bonded ◽  
Fiber Materials

As a kind of novel material of high strength and light weight, carbon fiber materials have been widely used in construction industry to repair the damaged bridges improving its mechanical performance. In this work, the reinforced plates made of carbon fiber materials (for short CFRP) are externally bonded to the bottom of concrete beams to enhance load capacity of beams. The strain energy release rates are calculated at the interest crack in concrete beams based on virtual crack closure technology using FEM and are chosen as the criterion to determine whether the mechanical properties of beams are strengthened by being externally bonded with CFRP. The effects of main crack propagation on plain concrete beam, on concrete beam strengthened with CFRP, and on inclined crack are also discussed. The comparison between the beams with and without CFRP shows that the CFRP significantly increases the loading capacity and crack resistance. It also shows that the main crack propagation can reduce loading capacity and crack resistance regardless of strengthening. The experiment observation also supports this. It proves the validity of the method, and it is concluded that in order to increase the loading capacity and crack resistance effectively, controlling over the crack propagation is necessary.

scholarly journals Microscopic Multiple Fatigue Crack Simulation and Macroscopic Damage Evolution of Concrete Beam

2019 ◽  
Vol 9 (21) ◽  
pp. 4664 ◽  
Author(s):  
Baijian Wu ◽  
Zhaoxia Li ◽  
Keke Tang ◽  
Kang Wang
Keyword(s):  
Fatigue Crack ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Concrete Beam ◽  
Crack Formation ◽  
Concrete Beams ◽  
Life Assessment ◽  
Engineering Practice ◽  
Stiffness Reduction ◽  
Fatigue Rupture

Microcracks in concrete can coalesce into larger cracks that further propagate under repetitive load cycles. Complex process of crack formation and growth are essentially involved in the failure mechanism of concrete. Understanding the crack formation and propagation is one of the core issues in fatigue damage evaluation of concrete materials and components. In this regard, a numerical model was formulated to simulate the thorough failure process, ranging from microcracks growth, crack coalescence, macrocrack formation and propagation, to the final rupture. This model is applied to simulate the fatigue rupture of three-point bending concrete beams at different stress levels. Numerical results are qualitatively consistent with the experimental observations published in literature. Furthermore, in the framework of damage mechanics, one damage variable is defined to reflect stiffness reduction caused by fatigue loading. S-N curve is subsequently computed and the macroscopic damage evolution of concrete beams are achieved. By employing the combined approaches of fracture mechanics and damage mechanics, made possible is the damage evolution of concrete beam as well as the microscopic multiple fatigue crack simulation. The proposed approach has the potential to be applied to the fatigue life assessment of materials and components at various scales in engineering practice.

scholarly journals Flexural Behavior of Post-Tensioned Concrete Beams with Multiple Internal Corroded Strands

2020 ◽  
Vol 10 (22) ◽  
pp. 7994
Author(s):  
Chi-Ho Jeon ◽  
Chang-Su Shim
Keyword(s):  
Prestressed Concrete ◽  
Concrete Beam ◽  
Concrete Beams ◽  
Safety Issue ◽  
Material Model ◽  
Flexural Behavior ◽  
Bending Test ◽  
Material Models ◽  
Strain Compatibility ◽  
Prestressed Concrete Beam

The corrosion of prestressing steel in prestressed concrete bridges is a critical safety issue. To evaluate the strength of a prestressed concrete beam with corroded strands, it is necessary to know the mechanical properties of the corroded strands in terms of their tensile strength and ductility. In this study, material models were suggested using tensile tests of corroded strands which had been taken from existing bridges. Five prestressed concrete beams with multiple internal corroded strands of different corrosion levels and locations were fabricated and tested using the three-point bending test. The beams with corroded strands near the support did not show meaningful flexural behavior changes, while the beams with corrosion in the mid-span showed significant strength reduction. In order to suggest the appropriate evaluation of the flexural strength of a prestressed concrete beam with corroded strands, material models of the corroded strands were divided into two model categories: a bi-linear material model and a brittle material model. Strength evaluations of the corroded prestressed concrete beams according to fps approximation and strain-compatibility using OpenSEES were conducted. Results suggested the use of the strain compatibility method only when the section loss was greater than 5%.

Hydration Kinetics and Microscopic Analysis of Calcium Oxide Expansion Clinker

2013 ◽  
Vol 477-478 ◽  
pp. 908-914
Author(s):  
Hua Li ◽  
Jia Ping Liu ◽  
Qian Tian ◽  
Shou Zhi Zhang
Keyword(s):  
Pure Water ◽  
Microscopic Analysis ◽  
Reaction Rate Constant ◽  
Cement Clinker ◽  
Hydration Reaction ◽  
Hydration Kinetics ◽  
High Calcium ◽  
High Calcium Fly Ash ◽  
The Difference ◽  
The Impact

Hydrating and calcining method combined with the kinetic equation were adopted to describe the hydration kinetics process of the laboratory-calcined CaO expansion clinker, XRD and SEM were used to test and analysis its mineral compo-sition and microstructure as well. The results show that, hydration reaction process in pure water of f-CaO contained in the CaO expansion clinker meets the Avrami isothermal crystallization kinetics model, and the hydration degree increases with temperature, with the relation between reaction rate constant and temperature conforming to Arrhenius law; the CaO expansion clinker powder contains a large number of particles in which f-CaO, CaSO4, Ca4Al6O12SO4 (partly still containing calcium silicates) phases existing at the same time, by the impact of the presence of impurity phases and the difference of calcining conditions, the hydration activity of f-CaO contained in CaO expansion clinker was different from that of pure CaO and that of f-CaO wrapped in cement clinker or high-calcium fly ash.

Crack formation in composites through a spring model

2011 ◽  
Vol 390 (4) ◽  
pp. 731-740 ◽  
Author(s):  
Supti Sadhukhan ◽  
Tapati Dutta ◽  
Sujata Tarafdar
Keyword(s):  
Crack Formation ◽  
Spring Model
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