Cracking Tests Research Articles

Comparative fracture resistance assessment of rubber-modified asphalt mortar based on meso-and macro-mechanical analysis

ABSTRACT This study investigates the effects of ground tire rubber (GTR) on the cracking resistance of asphalt mortar from different analysis scales. Furthermore, the effectiveness of different fracture test methods was compared for GTR-modified asphalt mortar, including the indirect tensile cracking test (IDEAL-CT), disk-shaped compact tension test (DCT) and Illinois flexibility index test (I-FIT). To achieve this, a mesoscopic fracture test based on the SEM-Servo Plus device was proposed firstly to obtain the micro-parameters of constitutive models in discrete-element modelling (DEM). A unified fracture modelling procedure that can avoid any interference factors was carried out for comparative fracture analysis. Results from the tests and simulations show that rubber filler plays a positive role in enhancing the fracture properties of the asphalt mortar. The fracture energy measured by IDEAL-CT is almost 5–6 times of the DC(T) test and 1.5–2 times of the I-FIT test. It is not an inherent attribute of material and can only be regarded as a relative index for fracture resistance evaluation. The FI and CTindex obtained from the I-FIT and IDEAL-CT test show a weak correlation of fracture resistance, especially when comparatively evaluating the GTR-modified asphalt mortar with minor difference in filler content.

Virtual source total focusing method for crack detection in complex curved structure

Accurate non-destructive testing and evaluation of cracks is important for the quality assurance and life-cycle management of key components in aerospace and energy industries. This paper presents a novel imaging method for cracks detection in complex curved structure , combining virtual source technique, multi-mode total focusing method and phase coherence imaging method. The virtual source on the sample surface is employed as the emitter and receiver for the ultrasonic array imaging. In this way, the calculation complexity of imaging algorithm due to beam path search can be reduced, and the detection sensitivity in the region of interest can be improved. In addition, the phase coherence factor is used to suppress the background noise and imaging artifacts, which significantly improves the quality of ultrasonic array imaging. A complex curved sample with variable thickness and non-developable surface was used to examine the effectiveness of the virtual source total focusing method. The signal-to-noise ratio of the crack defect is increased by more than 25 dB using the novel method compared with that of the conventional total focusing method, and the quantitative evaluation error of defect is less than 2.67%.

Geometry correction factor polynomials for corner crack test pieces accounting for constrained boundary conditions

Geometry correction factor polynomials for corner crack test pieces accounting for constrained boundary conditions

Penetapan Kadar Antosianin Dan Formulasi Sediaan Blush On Compact Powder Ekstrak Beras Merah (Oryza Rufipogon Griff.)

Blush or rouge is one of the decorative cosmetic preparations in beauty products that is widely used by presenting various colors as coloring the cheeks with an artistic touch so as to enhance aesthetics in the nuances of make-up on the face, giving a thinner and fresher accent to the face. One of the natural ingredients that can be used as a dye is Red Rice (Oryza rufipogon Griff.) Red Rice (Oryza rufipogon Griff.) is rice that contains anthocyanin compounds which function to give red color to red rice. This study aims to determine whether brown rice can be used as a coloring agent for blush on compact powder form and to determine the physical evaluation of blush preparations. The formulation of the blush preparation was made using dyes from red rice extract with a concentration of 0%, 5%, 10% and 15%. This research method was carried out experimentally, including: sample preparation, simplicia characterization, extract preparation, phytochemical screening, determination of anthocyanin levels, preparation of preparations. extraction was carried out by maceration and remaceration, using 96% ethanol solvent, then concentrated with a rotary vacuum evaporator. Tests carried out on the physical evaluation of blush on preparations included organoleptic tests, homogeneity tests, pH tests, irritation tests, adhesion / spread tests, crack tests, hedonic (preferability) tests and stability tests. The results of organoleptic testing, homogeneity, pH test, irritation test showed that all formulas were good. In the fracture test results of the 4 formulas it was observed that they were not cracked, cracked, and broken. The results of the hedonic (preference) test for blush with brown rice extract show that on average the ease of use of blush is preferred. The stability test results at room temperature (20-25oC) did not change, the stability test results at refrigerator temperature (5oC), oven temperature (40oC), and temperature to electric light (30oC) underwent changes.

The fitness and corrosion mechanisms of high‐strength steel in corrosive oil–water environment at high temperature

AbstractThis work investigated the mechanical decay mechanism and high‐temperature corrosion mechanism of high‐strength steel via high‐temperature mechanical experiments, and corrosion and stress corrosion cracking tests were performed in simulated working conditions where water, oil, H2S, and CO2 coexist. The results show that the tensile strength and yield strength of high‐strength steel decrease with increasing temperature; the tensile strength and yield strength at 350°C reduce 11.91% and 19.08%, respectively, compared with 25°C. Moreover, the corrosion rate of high‐strength steel gradually increased from 0.0914 mm/a at 150°C to 1.2288 mm/a at 350°C. In addition, the influence of high temperature on the corrosion mechanism was inferred through thermodynamic calculations, and the reason for the presence of Fe3O4 in the corrosion products at 350°C was analyzed. At 350°C, stress corrosion cracking was observed in high‐strength steels when the applied stress reached 90% of the yield strength. Based on the aforementioned studies, the relevant mechanisms related to the decay of mechanical properties, corrosion, and stress corrosion cracking are also proposed.

Application of Biological Glue-Clay Composite Substrate in Slope Ecological Restoration.

Given the issues of soil cracking, poor water retention during drought, and erosion damage caused by rainfall, we conducted an in-depth study on the water retention properties, cracking resistance, and scouring resistance of biogel-amended clay using evaporation cracking and scouring tests. The hydrophysical properties and cohesive aggregation mechanism of biogel-amended clay were explored, and the results showed that the incorporation of biogel improved the water retention, cracking resistance, and scour resistance of the clay samples. With an increase in the biogel content, the biogel mucous membrane inside the samples improved the cohesion between soil particles, reduced the generation and development of cracks, and improved the cracking resistance. There was no significant cracking of the samples after the biogel content reached 0.3%, which changed the migration of water in the sample, prevented water evaporation, and improved the water retention of the clay samples. Biofilm can change the migration of water in the sample, prevent some evaporation, and reduce the evaporation rate. To a certain extent, it can enhance the water retention capacity of the sample. Enhanced biofilm content significantly reduced scouring in the process of rainfall and runoff erosion of the sample, and biofilm content of 0.2% significantly reduced the surface of the specimen damaged by erosion. The hydrophysical properties of the composite-adhesive-amended clay samples were significantly improved compared with those of the single-bioadhesive-amended clay samples.

Cracking and erosion behaviors of sand–clay mixtures stabilized with microbial biopolymer and palm fiber

Drying-induced cracks and precipitation-induced erosion negatively impact the performance of soils in the context of extreme weather events. This study introduces two effective and sustainable materials, microbial biopolymer (MB) and palm fibers (PF), for cracking and erosion control in the sand–clay mixtures. A series of desiccation cracking tests, erosion tests, and SEM tests were conducted to evaluate the effectiveness of the treatment. The results showed that MB could significantly improve the resistance of the soil to cracking and scouring, and the improvement increased with increasing MB content. The optimum MB content was 0.15 % to achieve the maximum cracking and erosion resistance. For samples with varying sand contents, 0.15 % MB addition reduced the crack ratio, total crack length, and accumulative erosion ratio by 19.55 %–96.91 %, 4.22 %–99.58 %, and 57.88 %–89.53 %, respectively. In addition, PF positively affected the anti-crack and anti-erosion properties of the soil, and the application of 0.60 % PF had the best performance for both improvements. The cracks in the soils were mostly fine and shallow with the addition of 0.60 % PF, and therefore, the accumulative erosion ratio decreased by 44.18 %–62.76 % for samples with varying sand contents. Compared to the untreated soil, the degree of cracking and erosion was less due to the formation of a structure with more macropores and a sand skeleton in the treated samples with higher sand content. MB addition provides strong inter-particle bonding connections and a hydrophilic crust structure to improve the soils' resistance to cracking and erosion, while the fiber reinforcement effect benefits from interfacial friction and spatial restriction effects. This study provides mechanistic interpretations of desiccation cracking and erosion behavior in sand–clay mixtures under different treatments. It may guide the design of low-carbon technologies for geotechnical engineering applications.

Development of in-situ Delayed Hydride Cracking tests using neutron imaging to study the H redistribution in Zr-2.5%Nb

Delayed Hydride Cracking (DHC) is a failure mechanism that occurs in Zr alloys under certain conditions of hydrogen concentration, temperature and stress gradient. In service, hydrogen produced by corrosion reaction can be incorporated in Zr alloys and if the solid solubility is exceeded, hydrogen precipitates as zirconium hydride. The presence of a stress concentrator, such as a crack, generates the hydrogen diffusion and precipitation to the high stress zone beginning the DHC process. In this work, in-situ DHC tests in air at 250°C were performed at ANTARES, the neutron imaging facility of the FRM-II reactor. Samples of Zr2.5%Nb produced from extruded tubes and pressure tubes were studied using a stress rig specially modified to perform DHC tests in the neutron beam. H redistribution during mechanical testing was followed in-situ by registering the changes in neutron transmission. The results were compared with the images obtained by light optical microscopy after the tests. The results highlight the capabilities of neutron imaging to analyze time-dependent H distribution during DHC crack growth.

Effect of air voids on the fracture resistance of HMA in the indirect tensile cracking (IDEAL-CT) test

ABSTRACT Air voids (density) is a key volumetric property of asphalt mixes and play an unignorable role in anti-cracking. While lower voids were expected to result in more durable asphalt mixtures, contradictory trends were found in lab testing. In this study, several plant-produced mixtures were compacted to three levels of air voids (7%, 9%, and 11%) and tested to evaluate the sensitivity to the crack resistance. The results indicate that the higher the air voids, the better the cracking resistance as measured by the CTindex. To understand the cause, a stepwise regression analysis was conducted to model the IDEAL-CT parameters with volumetric and gradation parameters. The air void, percent passing the 0.6 mm (P0.6) and binder content (Pb) are found to have significant effects on CTindex and post-peak slope. The analysis of the CT change rate shows that the Pb, dust to binder ratio (D/B), and P0.6 can be used to predict the effect of the voids with a correlation factor (R2) of 0.96. For further understanding, the asphalt film thickness was calculated and found that compared with using film thickness as the single fitting parameter, combining the film thickness with D/B in modelling can dramatically increase the R2 of correlation from 0.67 to 0.92.

Development of a prior model to predict the cracking performance of asphalt mixture in general for asphalt material selection and mix design

ABSTRACT The main objective of this proposed study is to explore the correlations between the performance parameters measured from the state-of-practice mixture laboratory cracking tests and develop a prior model to predict the mixture cracking performance using the identified significant mix design variables for asphalt material selection and mix design stages. Total 20 plant-produced asphalt mixtures with varying design information were evaluated and the disparate mixture cracking performance tests were performed on these mixtures to characterise their performance. The analysis results indicate that the Flexibility Index (FI) parameter shows the overall good correlations with other cracking indices and thus is selected as the index to modelling mixture cracking performance in general. The stepwise regression model was employed to identify the significant mix design variables which were then used for the development of the prediction models to predict the mixture cracking performance in the form of FI parameter. The developed models can be used as a prior tool for material selection and mix design procedure, eliminating the time and effort for sample preparations and running the tests.

Laboratory performance and construction challenges for plant produced asphalt mixes containing RAP and RAS

In this study, four plant-produced asphalt mixes were considered to evaluate the performance and construction challenges of mixes containing RAP/RAS. Also, asphalt mixes were collected at two different plant-production times for each mix type to monitor the performance variability between lots. A softer base binder (PG 58–22) was used for mixes with RAS compared to the base binder (PG 64–16) used for the control mix (no RAP or RAS) and the mix with only RAP. Use of small dosages of rejuvenators and the softer binder in the RAS mixes were found to show similar performance compared to the control mix with no RAP or RAS. The results obtained from the extracted binders of these mixes indicate that mixes with RAP and RAP/RAS are expected to show higher rutting resistance and slightly lower low-temperature cracking resistance, also shown in the mix rutting and fracture cracking tests. A similar fatigue life was observed for all mixes at low strain levels in the Four-Point Beam test. However, the mix with both RAP and RAS was found to show better fatigue life at high strain levels. Similar performance test results were observed between different lots of the same mix type for most cases. Finally, there were no problems with field mixing, compaction, or finishing of the mixes containing RAP and RAP/RAS.

Crack Resistance and Strength Properties of Red Clay Modified with Lignocellulose and Guar Gum

Desiccation cracking is a common problem of red clay under wet and dry conditions. The presence of cracks could reduce soil strength properties, which is the major reason for shallow failure of red clay slopes. This study aims to propose some additives to improve the crack resistance as well as the strength of red clay. To this end, three natural fibers and three natural gels were primarily selected to modify red clay. Desiccation crack tests were conducted to identify the best fiber and gel in terms of crack resistance. Then, direct shear tests and uniaxial tensile tests were performed on the soil specimens modified by the best fiber and gel to determine the optimal dosages regarding strength improvements. The results demonstrated that natural gels reduced the crack resistance of red clay, while natural fibers could enhance the crack resistance. Lignocellulose was the best additive in improving the crack resistance of red clay, and the modified effect was positively correlated with the fiber dosage. Adding 1.5% lignocellulose into red clay could reduce the crack rate from 2.19% to 0.30%, with a reduction of 0.86 times. The tensile strength, shear strength and its parameters of lignocellulose-modified red clay showed a trend of increasing first and then decreasing with increasing lignocellulose dosage. At the optimal lignocellulose dosage of 0.75%, the shear strength and tensile strength were increased by 44.63% and 18.21%, respectively. The strength of red clay modified by both lignocellulose and guar gum was positively correlated with the dosage of guar gum, and the desirable dosage of guar gum was 1.0%. In engineering practice, the wet red clay mixed with 0.75% lignocellulose and grass seeds can be employed as planting soil and is sprayed uniformly onto the slope surface after excavation using a spraying planting machine. To further improve the strength of the planting soil, 1.0% guar gum solution can be sprayed on the soil surface. The findings could provide useful guidance for the protection of red clay slopes.

Assessment of the impact of binder grade on the laboratory performance of fiber reinforced asphalt mixtures

This study aims to evaluate the impact of different fiber types and binder modifications on the volumetric properties and performance (rutting and cracking) of fiber-reinforced asphalt mixtures (FRAM). Four types of fibers (carbon, fiberglass, basalt, and polyolefin/aramid (PFA) mix) and two binder performance grades (PG 58–28 unmodified and PG 76–22 polymer modified) were used to produce a total of ten asphalt mixtures (two control and eight FRAM). All fibers were introduced at the manufacturer-recommended dosages (i.e., carbon, fiberglass, basalt: at 0.16%, and PFA: at 0.05%) by mix weight. The mix design and volumetrics properties were examined to assess the impact of FRAM on volumetric properties of modified and unmodified binders. Mix characteristics, durability, rutting, and cracking performances were also evaluated by performing several tests, including dynamic modulus test |E*|, Cantabro loss, Asphalt pavement Analyzer (APA), Flow Number (FN), and Indirect Tensile Asphalt Cracking Test (IDEAL-CT). Mix design results showed that FRAM at 0.16% dosage increased the air voids of the unmodified binder (PG58-28). PFA fibers did not have an impact on air voids or volumetric properties of the asphalt mix regardless of modification. Performance results showed that FRAM were highly durable than control mix, but durability is significant for polymer modified binder (PG76-22). Furthermore, only PFA reinforced mixtures showed better rutting resistance for both modified and unmodified binders. The addition of fibers did not show any impact on cracking performance of modified and unmodified binder prepared asphalt mix. Finally, PFA reinforced mix also indicated higher fracture toughness (Gf) and carbon fibers improved the ductility of asphalt mix.

Investigation of fiber length distribution on crack resistance mechanism of basalt fiber asphalt mixture based on digital image processing technology

Basalt fiber has been widely used to enhance the crack resistance performance of asphalt mixtures. The length of the fiber is an essential parameter to affect the reinforcement effect. However, the research on fiber length distribution (FLD) on the anti-cracking mechanism of asphalt mixtures is still limited.This study aims to present an efficient methodology considering the FLD effect for investigating the crack resistance mechanism of basalt fiber asphalt mixture (BFAM). The X-ray computed tomography (CT) and discrete element (DE) simulation techniques are used to obtain morphological parameters of the BFAM correlated with the FLD (i.e. aggregate skeleton gap size parameters). Then, three indoor cracking tests of the BFAM at low and medium temperatures (i.e. trabecular bending test, IDEAL-CT test and SCB test) are conducted to investigate the relationship between crack resistance performance and morphological parameters. Influences of FLD on the fracture property indexes of the BFAM are discussed.Results indicate that the optimal FLD for the best anti-cracking performance of the BFAM with a specific dense-graded gradation can be found by using digital image processing technology. The morphological parameter of the longest axis of the aggregate skeleton gap is identified as the optimal FLD, which can significantly improve the fracture energy and fracture property indices of the BFAM compared with other FLDs. Under the same fiber content, the fracture energy enhancement of BFAM with different FLDs varies from 7.63% to 106.87%. As for the fracture property indices, the enhancement of the εB in trabecular bending test, CTindex in IDEAL-CT test, and FI in SCB test varies from 17.42% to 39.30%, 13.00% to 162.99%, and 7.46% to 77.61%, respectively. The results demonstrate that fiber length distribution indeed impacts the cracking resistance of the BFAM. The X-ray CT and DE simulation techniques are proved to be both highly efficient approaches for seeking the optimal FLD in the BFAM.

Impact of Flax Seed Protein and Beeswax Emulsion Blend on Leather Finishing– A Novel Eco-Benign Formulation

Protein based finishing on leather surface is generally done using casein-based formulation which forms a transparent and breathable film. Other naturally available options such as protein extracted from flax seeds exhibit versatile application in various fields. Thus in this work, the flax seed protein which is found to be 84%, along with bees wax emulsion is explored for the first time as an Eco benign binder and as an alternative for casein based finish. The binders play very important role in leather finishing as it helps in binding the various constituents of finishing such as pigments, wax, and additives to the leather matrix. The prepared Eco benign binder formed a continuous film on the surface of the leather and improved the of physical properties and crack resistance of the leather. The FTIR and particle size analysis were carried out for the characterization of the Eco benign binder. The experimental leathers were tested for tensile strength, elongation at break, lastometer test, colour fastness and cold crack tests. The results of the said tests were satisfied and on par with control leathers.

Experimental evaluation of alkali-activated and portland cement-based mortars prepared using waste glass powder in replacement of fly ash

The decreasing trend in coal fly ash production has led to a rapidly growing interest in finding alternative materials to replace fly ash in concrete. In this study, the use of glass powder to replace fly ash in concrete was investigated. The performance of portland cement and alkali-activated slag-based mortars containing fly ash (class F) or glass powder (aluminosilicate-based) was evaluated via a series of experiments, including fresh, physical, mechanical, and restrained cracking tests. Notably, a customized restrained shrinkage test was used to investigate the cracking potential. Results showed that the ultra-fine glass powder performed differently in the two binding systems. In the portland cement system, the use of glass powder yielded higher concrete mechanical performance compared to the concrete containing fly ash, while the opposite conclusion was obtained for the alkali-activated system. Comparing the alkali-activated system with the portland cement system, the alkali-activated materials with either fly ash or glass powder had higher free shrinkage and developed cracks much earlier under the restrained drying shrinkage. However, the alkali-activated materials maintained a high level of strain in the steel ring, which was primarily attributed to the development of multiple cracks and their different bonding at the mortar and steel interface.

Numerical analysis of hydro-thermal fracturing in saturated rocks by considering material anisotropy and micro-structural heterogeneity

This study is devoted to numerical modeling of cracking process induced by temperature change in saturated porous rocks in the context of geological disposal of radioactive waste. Effects of material anisotropy and heterogeneity are taken into account. The macroscopic elastic properties are determined from two steps of homogenization by considering pores and mineral inclusions at two different scales. An extended phase-field model is proposed to describe the initiation and propagation of localized cracks. Two damage variables are introduced to conveniently represent both tensile and shear cracks. New damage evolution criteria are defined by incorporating the pore pressure effect. Three application examples are presented. By assuming a random distribution of pores and inclusions, the efficiency of the proposed model for capturing the progressive cracking process is first verified in a triaxial compression test. The thermal cracking process in an anisotropic and heterogeneous sample is then investigated. The respective influences of elastic anisotropy and spatial variability of pores and inclusions are outlined. Finally, the proposed model is applied to a series of real laboratory thermal cracking tests. Both hydromechanical responses and cracking evolution patterns are investigated. Numerical results are compared with experimental measurements. The main mechanisms involved in the thermal cracking process are highlighted.

Comparison between Shear Strength in Total Etch and Self Etch Adhesive material in Bonding of Stainless-steel Brackets

Bracket bonding in tooth enamel with total-etch material is a general practice procedure. The researchers combine etchant and bonding procedures in one application or called self-etch. This procedure is a solution for timesaving in bonding procedures and minimizing enamel damage without degrading the ability to sustain bond strength during the application of an orthodontic appliance. The aim of this research is to know the comparison between shear strength, ARI value, and enamel crack length between total-etch and self-etch adhesive material. Eighteenth teeth are divided into three groups which are K-1 as a control group without etchant application, K2 as the self-etch material group, and K-3 as the total etch material group. All teeth practiced shear strength test by Universal Testing Machine Autograph. After bracket removal, an Adhesive Remnant Index (ARI) test was performed and followed by cleaning the adhesive remnant with tungsten carbide burs and continued by enamel crack test by Scanning Electron Microscope (SEM). According to the OneWay Anova result, there is a difference between shear strength, ARI value, and significant enamel crack length (p<0.05) between the control group, self-etch group, and total-etch group. Total etch material has higher shear strength, higher ARI value, and higher enamel crack length number than self-etch material.

Accounting for the Effect of Air Voids on Asphalt Mix Monotonic Cracking Testing Results

Abstract Various monotonic cracking resistance assessment tests and indicators of asphalt mixes have their own merits; however, they provide illogical interpretations of mix resistance to cracking under different air void (AV) contents. This study aims to investigate and address the limitations of the monotonic tests and indicators in evaluating the cracking resistance of asphalt mixes with different AV contents. The results show that the shape of the load-displacement curve, curve basic elements, and monotonic indicators are significantly sensitive to variation in AV content. However, the currently proposed correction ratios could not address this dependency of cracking assessment on AV content. This study therefore proposes and evaluates a new approach and correction ratios for monotonic tests and performance indicators. The results demonstrate that the newly proposed correction ratios could normalize the effect of AV content on the examined performance assessment indicators.

Analysis of the Cause of Gas Pipeline Burst in a Gas Production Plant

In order to reduce the failure of pipes, the macroscopic morphology, macroscopic crack, chemical composition, hardness, microstructure and so on were tested through the macroscopic analysis, physical and chemical property inspection, hydrogen-induced cracking test and sulfide stress cracking test. The SEM was used to analyze the microscopic cracks, fractures and element distribution at the failure site. The results show that the cracking zone of the failed pipe section has the characteristics of bulging deformation and thinning of wall thickness. The macroscopic fracture of the fracture is a typical 45° shear shape. The fracture was observed under the high magnification of scanning electron microscope and showed dimple morphology. The failure mode of the failed pipe segment is plastic fracture. The reason for the failure of this pipe is the special geographical location of this section of the pipeline, and the sudden increase of pipeline pressure after the well opening operation causes the water hammer phenomenon, which causes the local bulging of the pipe body, which further leads to burst failure.