scholarly journals Stimulated autogenous-healing capacity of fiber-reinforced mortar incorporating healing agents for recovery against fracture and mechanical properties

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Abdul Salam Buller ◽  
Fahad-ul-Rehman Abro ◽  
Tariq Ali ◽  
Sadam Hussain Jakhrani ◽  
Abdul Hafeez Buller ◽  
...  
Keyword(s):  
Peak Load ◽  
Mouth Opening ◽  
Bending Test ◽  
Crack Mouth Opening Displacement ◽  
Partial Recovery ◽  
Self Healing ◽  
Fiber Reinforced ◽  
Opening Displacement ◽  
Digital Microscope ◽  
Set Up

Abstract This study aimed to investigate the effect of autogenous healing capacity with the addition of expansive and crystalline agents on mechanical and fracture behaviors of fiber-reinforced (FR) mortar specimens with crack mouth opening displacement (CMOD) controlled test set-up. The experimental results of a self-healing approach of FR mortar were analyzed in terms of first cracking peak load (FCPL) increase, index of fracture toughness recovery (IFTR), and index of fracture energy recovery (IFER). Initially, the specimens were pre-cracked at different crack widths ranging from 30 μm to 200 μm after 28-days of curing. After pre-cracking, the specimens were kept in water for 56- and 120-day healing. A controlled three-point bending test (PBT) was applied on prism specimen having a central notch of 40 mm depth for pre-cracking as well as the post-conditioning stage for determining the FCPL. However, the crack surfaces were monitored by a high-range digital microscope and scanning electron microscope (SEM) to examine the nature of healed products near the damaged area. Test results revealed that a significant recovery of small cracks (≤50 μm) could be achieved for self-healing specimens by using healing agents (HA), while for large cracks (≥100 μm) partial recovery could be achieved after the 120-day healing period.

scholarly journals Fracture Properties and Softening Curves of Steel Fiber-Reinforced Slag-Based Geopolymer Mortar and Concrete

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1445 ◽  
Author(s):  
Yao Ding ◽  
Yu-Lei Bai
Keyword(s):  
Fracture Toughness ◽  
Fracture Energy ◽  
Inverse Analysis ◽  
Steel Fiber ◽  
Mouth Opening ◽  
Crack Mouth Opening Displacement ◽  
Fiber Reinforced ◽  
Fiber Volume ◽  
Opening Displacement ◽  
Fracture Properties

Adding short steel fibers into slag-based geopolymer mortar and concrete is an effective method to enhance their mechanical properties. The fracture properties of steel fiber-reinforced slag-based geopolymer concrete/mortar (SGC/SGM) and unreinforced control samples were compared through three-point bending (TPB) tests. The influences of steel fiber volume contents (1.0%, 1.5% and 2.0%) on the fracture properties of SGC and SGM were studied. Load-midspan deflection (P-δ) curves and load-crack mouth opening displacement (P-CMOD) curves of the tested beams were recorded. The compressive and splitting tensile strengths were also tested. The fracture energy, flexural strength parameters, and fracture toughness of steel fiber-reinforced SGC and SGM were calculated and analyzed. The softening curves of steel fiber-reinforced SGC and SGM were determined using inverse analysis. The experimental results show that the splitting tensile strength, fracture energy, and fracture toughness are significantly enhanced with fiber incorporation. A strong correlation between the equivalent and residual flexural strengths is also observed. In addition, the trilinear strain-softening curves obtained by inverse analysis predict well of the load-displacement curves recorded from TPB tests.

TEST STUDY ON THE BEST PASTING LAYER OF FRP REINFORCED CONCRETE

2019 ◽  
Vol 27 (02) ◽  
pp. 1950105
Author(s):  
XIANGQIAN FAN ◽  
JUEDING LIU
Keyword(s):  
Fracture Toughness ◽  
Acoustic Emission ◽  
Reinforced Concrete ◽  
Crack Depth ◽  
Mouth Opening ◽  
Bending Test ◽  
Crack Mouth Opening Displacement ◽  
Displacement Curve ◽  
Crack Mouth ◽  
Opening Displacement

To optimize the strengthening method using the fiber reinforced polymer (FRP) for the reinforcement of the concrete structure with cracks, the three-point bending test was conducted on the concrete beams wrapped with different layers of FRP materials. The strain gauges were pasted on the surface of the specimens to measure the initial cracking load. The crack mouth opening displacement (CMOD) was utilized to test the load–crack mouth opening displacement curve. According to the improved calculation formula of the fracture toughness, the critical effect crack length [Formula: see text], initiation fracture toughness [Formula: see text] and instability fracture toughness [Formula: see text] of specimens were calculated. The test results showed that, under the same initial crack depth, the peak load of FRP reinforced concrete decreases with the increase of FRP pasting layer. When there was one layer wrapped over the specimen, the instability toughness of the specimen reached the maximum value and the crack resistance was the best. Based on acoustic emission testing method, the acoustic emission parameters of the above-mentioned concrete during fracture process were identified and collected. The optimal layer of the FRP reinforced concrete with cracks was analyzed from the acoustic emission method.

scholarly journals Vibrated Concrete vs. Self-Compacting Concrete: Comparison of Fracture Mechanics Properties

2014 ◽  
Vol 601 ◽  
pp. 199-202
Author(s):  
Sara Korte ◽  
Veerle Boel ◽  
Wouter de Corte ◽  
Geert de Schutter
Keyword(s):  
Fracture Mechanics ◽  
Mouth Opening ◽  
Bending Test ◽  
Crack Mouth Opening Displacement ◽  
Self Compacting Concrete ◽  
Opening Displacement ◽  
Three Point Bending ◽  
Fracture Parameters ◽  
Wedge Splitting Test ◽  
Splitting Test

This study focuses on the fracture mechanics aspect of self-compacting concrete, compared to vibrated concrete. The most commonly used experiments to investigate the toughness and cracking behaviour of concrete are the three-point bending test (3PBT) on small, notched beams, and the wedge-splitting test (WST) on cubic samples with guiding groove and starter notch. From the resulting P-CMOD curves (applied load versus crack mouth opening displacement), different fracture parameters, such as fracture energy and fracture toughness, can be extracted. Moreover, using inverse analysis, the σ-w relationship (tensile stress versus crack width) can be derived. This paper lists the results of a series of tests on samples, made of VC, SCC of equal strength, and SCC with identical w/c factor. Subsequently, a comparison of the mechanical characteristics is made, revealing important differences regarding several fracture parameters.

scholarly journals Advanced Evaluation of the Freeze–Thaw Damage of Concrete Based on the Fracture Tests

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6378
Author(s):  
Barbara Kucharczyková ◽  
Hana Šimonová ◽  
Dalibor Kocáb ◽  
Libor Topolář
Keyword(s):  
Peak Load ◽  
Mouth Opening ◽  
Crack Mouth Opening Displacement ◽  
Experimental Program ◽  
Crack Model ◽  
Test Evaluation ◽  
Fracture Test ◽  
Opening Displacement ◽  
Freeze Thaw ◽  
Fracture Tests

This paper presents the results of an experimental program aimed at the assessment of the freeze–thaw (F–T) resistance of concrete based on the evaluation of fracture tests accompanied by acoustic emission measurements. Two concretes of similar mechanical characteristics were manufactured for the experiment. The main difference between the C1 and C2 concrete was in the total number of air voids and in the A300 parameter, where both parameters were higher for C1 by about 35% and 52%, respectively. The evaluation of the fracture characteristics was performed on the basis of experimentally recorded load–deflection and load–crack mouth opening displacement diagrams using two different approaches: linear fracture mechanics completed with the effective crack model and the double-K model. The results show that both approaches gave similar results, especially if the nonlinear behavior before the peak load was considered. According to the results, it can be stated that continuous AE measurement is beneficial for the assessment of the extent of concrete deterioration, and it suitably supplements the fracture test evaluation. A comparison of the results of fracture tests with the resonance method and splitting tensile strength test shows that all testing methods led to the same conclusion, i.e., the C1 concrete was more F–T-resistant than C2. However, the fracture test evaluation provided more detailed information about the internal structure deterioration due to the F–T exposure.

scholarly journals Fracture parameters of fly ash geopolymer mortars with carbon black and graphite filler

2021 ◽  
Vol 1205 (1) ◽  
pp. 012019
Author(s):  
H Simonova ◽  
C Mizerova ◽  
P Rovnanik ◽  
M Lipowczan ◽  
P Schmid
Keyword(s):  
Fly Ash ◽  
Carbon Black ◽  
Mouth Opening ◽  
Bending Test ◽  
Crack Mouth Opening Displacement ◽  
Crack Model ◽  
Vertical Force ◽  
Opening Displacement ◽  
Mechanical Fracture ◽  
Fracture Parameters

Abstract In this study, the effect of carbon black and graphite filler on the crack initiation and fracture parameters of fly ash geopolymer mortar is investigated. The carbon black was added in the amount of 0.5 and 1.0% and graphite powder in the amount of 5 and 10% relative to the fly ash mass. The reference mixture without any filler was also prepared. The fracture characteristics were determined based on the results of the three-point bending test of prismatic specimens provided with an initial central edge notch. The fracture experiments were conducted at the age of 48 days. The vertical force (F), the displacement measured in the middle of the span length (d), and the crack mouth opening displacement (CMOD) were continuously recorded during the test. The records of fracture tests were subsequently evaluated using the effective crack model, work-of-fracture method, and double-K fracture model. The addition of both fine fillers led to a decrease in monitored mechanical fracture parameters in comparison with reference mortar.

Finite Element Analysis of Flaw Growth History

2010 ◽  
Author(s):  
Nader Yoosef-Ghodsi ◽  
Da-Ming Duan ◽  
Qishi Chen ◽  
Randy Petersen ◽  
Chengye Fan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Peak Load ◽  
Mouth Opening ◽  
Crack Mouth Opening Displacement ◽  
Opening Displacement ◽  
Element Analysis ◽  
Family Of Curves ◽  
Growth History ◽  
Unloading Compliance

Finite element models of curved wide plate (CWP) samples were used to generate a family of load-deformation curves, where each curve corresponds to a flaw with a constant depth. This family of curves was then compared to the test results to find the flaw depth corresponding to each load step using two techniques. One technique is based on mapping the crack mouth opening displacement (CMOD) response obtained from finite element analysis (FEA) and tests, while the other one is based on FEA and experimental unloading compliance data. Both the CMOD mapping and unloading compliance techniques were applied to six CWP specimens and the results from the two techniques were compared. The CWP specimens included flaws either at the centreline of the girth weld or at the heat affected zone (HAZ). Nominal flaw sizes were 3 or 5 mm deep by 25, 50 or 75 mm long. For all specimens, testing continued until either maximum load was reached or specimen rupture occurred. Failure strain, defined as the remote strain at peak load, ranged from 1.1% to 4.1%. The flaw growth history curves from the CMOD mapping and unloading compliance techniques for a given specimen were generally found to be in close agreement. The prediction of flaw growth at failure for the specimens with flaw in the weld was closer to the experimental flaw growth at failure than for the specimens with flaw in the HAZ. The average FEA to test ratio of the flaw growth at failure for these two groups of specimens was 0.95 and 0.6, respectively. Additional analyses were carried out to study the effect of HAZ softening and the shape of the input stress strain curves beyond the onset of necking.

Meso-scale study of notched and un-notched plain concrete beam under three-point bending

2021 ◽  
Author(s):  
Biswajit Pal ◽  
Ananth Ramaswamy
Keyword(s):  
Concrete Beam ◽  
Finite Thickness ◽  
Peak Load ◽  
Mouth Opening ◽  
Plain Concrete ◽  
Crack Mouth Opening Displacement ◽  
Opening Displacement ◽  
Two Phase ◽  
Three Phase ◽  
Meso Scale

<p>In this study, meso-scale (mm-cm scale) modelling approach is adopted to simulate the behaviour of plain concrete beam under 3-point bending. At meso-level, concrete is assumed as either a two- phase or a three-phase composite material (mortar, aggregate and/or interfacial transition zone- ITZ). In this tudy, first the aggregates are generated and placed in the concrete domain with prescribed randomness. The remaining space in the concrete domain is then filled with mortar. However, in three phase model, ITZ of finite thickness surrounding the aggregates is assumed to exist. In this study, three geometrically similar beam specimens with and without notch have been considered. The simulated load-crack mouth opening displacement (CMOD) is then validated with the corresponding experimental data. A convergence study of peak load with different specimens in terms of randomness in aggregates generation and placement has been studied.</p>

The Effects of Tensile Softening Curve Parameters on Fracture in Concrete Based on Initial Fracture Toughness Criterion

2014 ◽  
Vol 904 ◽  
pp. 232-235
Author(s):  
Long Bang Qing ◽  
Huan Huan Liu
Keyword(s):  
Fracture Toughness ◽  
Crack Propagation ◽  
Peak Load ◽  
Mouth Opening ◽  
Crack Mouth Opening Displacement ◽  
Opening Displacement ◽  
Critical Crack ◽  
Softening Curve ◽  
Initial Fracture ◽  
Tensile Softening

The effects of tensile softening curve parameters on the crack propagation P-CMOD and P-CTOD curves were analyzed using a calculation method which adopted the initial fracture toughness as the crack propagation criterion. The results showed that: the whole process of the P-CMOD and P-CTOD curves were affected by the tensile softening curve parameters, especially for the descending segment of the curves, but the peak load and critical crack mouth opening displacement were less affected.

Comparison study of crack propagation in rubberized and conventional prestressed concrete sleepers using digital image correlation

2021 ◽  
pp. 095440972110205
Author(s):  
Guoqing Jing ◽  
Du yunchang ◽  
Ruilin You ◽  
Mohammad Siahkouhi
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Prestressed Concrete ◽  
Mouth Opening ◽  
Image Correlation ◽  
Crack Mouth Opening Displacement ◽  
Experimental Program ◽  
Pure Bending ◽  
Opening Displacement ◽  
Rubber Concrete

Rubber concrete (RC) has been confirmed to be suitable for concrete sleeper production. This paper studies the cracking behaviour of conventional and rubber-reinforced concrete sleepers based on the results of an experimental program. The cracking behaviour in the pure bending zone was analysed up to a load of 140 kN. The crack mouth opening displacement (CMOD) was accordingly measured using a digital image correlation (DIC) method. The DIC results show that the rubber prestressed concrete sleeper (RPCS) has a resistance against crack initiation that is 20% greater than that of the conventional prestressed concrete sleeper (CPCS) under the same loading condition; however, due to the higher crack growth rate of the RPCS, the first crack detected by the operator forms at 60 kN, which corresponds to a strength approximately 9% lower compared with the 65 kN load at which the first crack is detected in the CPCS. Before the first crack (60 kN), the RPCS has a deflection 35% lower than that of the CPCS, but after cracking, at loads of 80 kN, 100 kN and 140 kN, the RPCS has a deflection 15%, 4% and 24% higher than that of the CPCS, respectively.

Studies on effect of steel fiber and coarse aggregate on fracture properties of self compacting concrete using wedge splitting test

2019 ◽  
Vol 11 (6) ◽  
pp. 751-767
Author(s):  
Raja Rajeshwari B. ◽  
Sivakumar M.V.N.
Keyword(s):  
Fracture Energy ◽  
Coarse Aggregate ◽  
Peak Load ◽  
Mouth Opening ◽  
Test Method ◽  
Crack Mouth Opening Displacement ◽  
Fine Aggregate ◽  
Content Type ◽  
Fracture Properties ◽  
Splitting Test

Purpose Fracture properties depend on the type of material, method of testing and type of specimen. The purpose of this paper is to evaluate fracture properties by adopting a stable test method, i.e., wedge split test. Design/methodology/approach Coarse aggregate of three different sizes (20 mm, 16 mm and 12.5 mm), three ratios of coarse aggregate, fine aggregate (CA:FA) (50:50, 45:55, 40:60), presence of steel fibers, and specimens without and with guide notch were chosen as parameters of the study. Findings Load-crack mouth opening displacement curves indicate that for both fibrous and non-fibrous mixes, higher volume of aggregate and higher size of coarse aggregate have high fracture energy. Originality/value For all volumes of coarse aggregate, it was noticed that specimens with 12.5 mm aggregate size achieved highest peak load and abrupt drop post-peak. The decrease in coarseness of internal structure of concrete (λ) resulted in the increase of fracture energy.

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