scholarly journals An Investigation of Softening Laws and Fracture Toughness of Slag-Based Geopolymer Concrete and Mortar

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5200
Author(s):  
Yao Ding ◽  
Yu-Lei Bai ◽  
Jian-Guo Dai ◽  
Cai-Jun Shi
Keyword(s):  
Fracture Toughness ◽  
Inverse Analysis ◽  
Mouth Opening ◽  
Crack Mouth Opening Displacement ◽  
Unstable Fracture ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Tension Softening ◽  
Initial Fracture ◽  
Crack Tip Opening

This paper aimed to determine the softening laws and fracture toughness of slag-based geopolymer (SG) concrete and mortar (SGC and SGM) as compared to those of Portland cement (PC) concrete and mortar (PCC and PCM). Using three-point bending (TPB) tests, the load vs. mid-span displacement, crack mouth opening displacement, and crack tip opening displacement curves (P-d, P-CMOD, and P-CTOD curves) were all recorded. Bilinear softening laws of the PC and SG series were determined by inverse analysis. Furthermore, the cohesive toughness was predicted using an analytical fracture model. The cohesive toughness obtained by experimental study was consistent with that predicted by analytical method, proving the correctness of the tension softening law obtained from inverse analysis. In addition, both initial and unstable fracture toughness values of SG mortar were lower than those of PC mortar given the same compressive strength. Moreover, the initial fracture toughness of SG concrete was generally lower than that of PC concrete, whereas the unstable fracture toughness exhibited an opposite trend.

Effect of Calcium Dissolution on the Fracture Properties of Concrete Exposed to Nitric Acid Environment

2011 ◽  
Vol 374-377 ◽  
pp. 1974-1978
Author(s):  
Hai Long Wang ◽  
Chun Ling Guo ◽  
Xiao Yan Sun
Keyword(s):  
Fracture Toughness ◽  
Nitric Acid ◽  
Mouth Opening ◽  
Crack Mouth Opening Displacement ◽  
Unstable Fracture ◽  
Crack Mouth ◽  
Acid Attack ◽  
Opening Displacement ◽  
Fracture Properties ◽  
Initial Fracture

The effect of calcium leaching by nitric acid on fracture properties of concrete was experimentally studied. The double-K fracture parameters were investigated using three-point bending beams, and the deterioration regularity of fracture properties of concrete chronically attacked by nitric acid was gotten on basis of these results. The load-crack mouth opening displacement curves under different nitric attack periods were obtained by pasting some strain gauges onto the pre-crack tip. On basis of the double-K criterion, the unstable fracture toughness as well as the initial fracture toughness was calculated according to the critical crack mouth opening displacement, the unstable fracture load and initial cracking load which can be obtained from the test. The experimental results indicated that the ratio of the initial fracture toughness to the unstable fracture toughness varied between 0.47 and 0.61 approximately. Both of the unstable fracture toughness and the initial fracture toughness decrease with attack period especially during the early 60 days, then drop to a stable trend gradually. In addition, the initial fracture toughness is less sensitive to acid attack compared with the unstable fracture toughness.

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 for Crack Opening Displacement of Steel Fiber Reinforced Concrete under Three-Point Bending

2010 ◽  
Vol 36 ◽  
pp. 157-161 ◽  
Author(s):  
Tin Gyi Zhang ◽  
Yuan Bao Leng ◽  
Dan Ying Gao
Keyword(s):  
Crack Opening Displacement ◽  
Crack Opening ◽  
Mouth Opening ◽  
Crack Tip ◽  
Crack Mouth Opening Displacement ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Critical Crack ◽  
Critical Crack Opening ◽  
Crack Tip Opening

Based on the principle of electrical measurement method, the clip gauge was made to measure the crack opening displacement (COD).Through the three-point bending test on the specimens of steel fiber reinforced high strength concrete (SFHSC), the effect of the fiber volume fraction (ρf) upon the critical crack opening displacement (the critical crack tip opening displacement and the critical crack mouth opening displacement) was studied. The result shows that the effect of ρf on mouth-tip ratio (the ratio of critical crack mouth opening displacement to critical crack tip opening displacement) can reflect its effect upon the critical crack opening displacement. According to the geometrical relationship between the initial crack length and the critical crack opening displacement，calculation method for the initial crack length was proposed. Based on the test result, the formula was established for calculating the critical crack tip opening displacement.

Critical Crack Tip Opening Displacement for X70 and X80 Steels - A Parametric Study

2017 ◽  
Vol 898 ◽  
pp. 719-724 ◽  
Author(s):  
Xiao Ben Liu ◽  
Qing Quan Duan ◽  
Bao Dong Wang ◽  
Hong Zhang
Keyword(s):  
Mouth Opening ◽  
High Strength ◽  
Crack Mouth Opening Displacement ◽  
Specimen Thickness ◽  
Pipe Steels ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Critical Crack ◽  
Line Pipe ◽  
Crack Tip Opening

High strength line-pipe steels are widely used in long distance gas pipelines. Fracture toughness is one major parameter in the performance evaluation of these line-pipe steels. For high strength line-pipe steels, critical crack tip opening displacement (CTOD) is one typical quantity for fracture toughness. In this paper, a series of experimental studies were conducted to investigate the influences of steel property and specimen thickness on critical CTOD by three points bending tests for X70 and X80 line-pipe steel. Results showed that the critical CTOD is mainly depended on the plastic crack mouth opening displacement of the specimen. For the same size specimens, the critical CTOD of X80 steel was much less than X70 steel. The specimen thickness had a significant influence on the plastic crack mouth opening displacement. With the decrease of the specimen thickness, the critical CTOD increased.

Experimental Study on Fracture Properties of Cementitious Materials

2007 ◽  
Vol 348-349 ◽  
pp. 157-160
Author(s):  
Yu Zhu ◽  
Shi Lang Xu
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Cement Paste ◽  
Mouth Opening ◽  
Material Design ◽  
Cementitious Materials ◽  
Crack Mouth Opening Displacement ◽  
Unstable Fracture ◽  
Opening Displacement ◽  
Fracture Properties

For micro-fiber reinforced strain-hardening cementitious materials, in addition to the basic characteristics and mechanical properties of fiber and interfacial properties between fiber and matrix, mechanical properties of matrix such as strength and crack resistance are essential parameters for material design, too. Therefore, the fracture properties of cement paste and mortar which are two most basal cementitious materials were studied, using three-point bending beams of which strength and depth are varied. Complete load versus crack mouth opening displacement (P-CMOD) curve directly obtained, and double-K fracture parameters ini Ic K and un Ic K were subsequently determined. The initial cracking load Pini was determined using resistant strain gauges. The results show that an apparent stable crack propagation before unstable failure was observed both in cement paste and in mortar. For cement paste, due to the influence of shrinkage crack, the divergence of the unstable fracture toughness un Ic K is more evident than initial fracture toughness ini Ic K .

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.

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.

Analysis on Critical CTOD of Long-Term Used Penstock

2017 ◽  
Vol 741 ◽  
pp. 57-62
Author(s):  
Fumito Kawamura ◽  
Masazumi Miura ◽  
Ryuichiro Ebara ◽  
Keiji Yanase
Keyword(s):  
Fracture Toughness ◽  
Structural Integrity ◽  
Steel Structures ◽  
Chemical Compositions ◽  
Structural Components ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Critical Crack ◽  
Crack Tip Opening

Many studies have been conducted to characterize the fracture toughness of structural steels and their welded joints. However, most studies focus on newly developed steels, and the number of studies on the fracture toughness of long-term used steels in structural components is rather limited. Furthermore, a lack of data on the fracture toughness causes difficulties in evaluating the structural integrity of existing steel structures. In this study, CTOD tests were performed to characterize the fracture toughness of penstock that has been in service for 50 years. By measuring the critical crack tip opening displacement in conjunction with analysis for chemical compositions, the characteristics of fracture toughness were investigated.

Modeling and CMOD Mapping of Surface-Cracked Wide Plates

2008 ◽  
Author(s):  
Da-Ming Duan ◽  
Yong-Yi Wang ◽  
Yaoshan Chen ◽  
Joe Zhou
Keyword(s):  
Test Data ◽  
Driving Force ◽  
Mouth Opening ◽  
Quality Data ◽  
Crack Mouth Opening Displacement ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Crack Driving Force ◽  
Strain Capacity ◽  
Test Conditions

Curved wide plate (CWP) tests are frequently used to measure the tensile stress and strain capacity of pipeline girth welds. The parameters affecting the CWP measurement include specimen geometry and cooling setups. High-quality data is obtained when valid test conditions are confirmed. Crack mouth opening displacement (CMOD) is often measured in CWP tests. CMOD is a direct indicator of the amount of deformation at the cracked plane. It is an indirect indicator of the crack driving force (CDF) imparted on the crack. For a given test geometry and material, certain relationships can be derived between the measured CMOD and the more conventional representation of crack driving force, such as CTOD (crack tip opening displacement) and J-integral. Such relationships are a key element in fracture toughness testing standards. This kind of relationship is also particularly useful in strain-based design where CWP specimens are used for strain capacity and flaw growth prediction. In this paper finite element (FE) analysis is first used in modeling CWP testing conditions for X100 specimens with girth weld flaws to validate the test conditions. A novel approach called CMOD mapping is then developed to characterize the flaw behavior which, by making a direct use of CMOD test data from the CWP tests, is used to estimate the crack growth in the CWP. Finally analysis of strain limits using crack driving force (CDF) for the CWP specimens is also given by comparing experimental test data and FE estimation.

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