Transverse Crack Spacing Research Articles

Tensile damage evolution and mechanical behaviour of SiCf/SiC mini-composites through 4D in-situ micro-CT and data-driven modelling

Damage evolution of SiCf/SiC ceramic matrix mini-composites (CMMCs) was characterised by using a 4D in-situ micro-computed tomography (CT) tensile test and digital volume correlation (DVC) technique. Additionally, a CT damage data-driven shear lag model was developed to predict its tensile stress-strain response. A 4D in-situ X-ray CT tensile test of a unidirectional SiCf/SiC mini-composite was first carried out. Then two ad-hoc deep-learning image segmentation models were developed to automatically identify its microstructure and damages induced by tension, respectively. Damage evolution was quantitively characterised by visualising the initiation and propagation of matrix cracks in three-dimensions (3D). A two-step approach was employed to evaluate its 3D internal strain distributions at various loading levels, which further revealed strain concentrations and helped establishing the tensile stress-strain response of the CMMCs. It was observed that transverse cracking is the predominant damage mode, and the average crack opening displacement increases with loading. A high-fidelity X-ray CT data-driven shear lag model was developed, incorporating inputs of transverse matrix crack spacing calculated by the 4D in-situ CT test data. The predicted stress-strain response showed a good correlation with the experimental results.

An Evaluation of Asphalt Mixture Crack Resistance and Identification of Influential Factors

The crack resistance of asphalt pavement mixtures directly impact pavement service condition and pavement distress. And characterizing the crack resistance of a pavement mixture can reflect the crack resistance potential of asphalt pavement. This study analyzes several representative highway sections based on time, material, and service conditions to identify the mixture type of three layers. Semi-circular bending tests are conducted at 15 °C, and load–displacement curves are recorded. Factor independence analysis is performed, and combinations showcasing the cracking performance of the surface layer, middle layer, and bottom layer are selected. Analysis of variance (ANOVA) evaluating the indices versus selected factors for the three layers identifies significant influencing factors, and the crack resistance is analyzed based on these significant factors. The crack resistance of the middle layer with the highest truck loads is significantly lower than the two other lanes and the shoulder. Transverse crack spacing (TCS) can be used to directly evaluate the crack resistance of the mixture. The Factor dots upper rate (FUDR) and absolute Factor dots upper rate (absFUDR) indices are introduced to quantify the percentage deviation of a factor specimen from the average crack resistance index–fracture energy ratio, indicating whether the crack curve becomes sharper or flatter. The factor dots upper rate index is then applied to characterize the factors, and the results are reasonable. It is found only on the surface and middle layers that the service age has significant impacts on crack resistance, the Transverse crack spacing has significant impacts on crack resistance index, and the Factor dots upper rate can identify the brittleness of mixtures with different factors.

Non-uniform spacing of transverse cracks in symmetric composite laminates

Non-uniform spacing of transverse cracks in symmetric composite laminates

Investigation of transverse crack spacing in an asphalt pavement with a semi-rigid base

Transverse cracking is a serious problem for semi-rigid base asphalt pavement. The shrinkage of the base course and the surface course, as well as reflective cracks, are key factors for transverse cracking in asphalt pavement. Crack spacing can directly reflect the degree of transverse cracking in pavements. Therefore, this study aims to calculate the transverse crack spacing and discuss its affecting factors. To this end, a calculation model of transverse crack spacing for the semi-rigid base asphalt pavement was first established. Then, the transverse crack spacings of different composite structures were calculated, and the influences of the shrinkage coefficient, the structural layer thickness, and the pavement tensile strength on transverse crack spacing were expounded. Finally, the transverse crack spacing of the pavement after the appearance of the reflective was calculated. The results show that the lower lime and fly ash content and skeleton gap gradation can be adopted during the design of the base course. Meanwhile, the lower lime and fly ash content in the macadam base, the skeleton gap gradation and asphalt concrete with a larger particle size in the surface layer can be used during the design of surface layer. In addition, the transverse crack spacing of the semi-rigid base asphalt pavement could be increased by reducing the shrinkage coefficient, increasing the thicknesses of the surface course and the base course, and improving the tensile strength of the pavement. After the appearance of reflective cracks, the transverse crack spacing of the surface layer ranged between 32.8 m and 66.5 m. 15fp-AC25, 15fp-AC20, 15df-AC25, and 17fp-AC25 were found to be the best semi-rigid base asphalt pavement structures to reduce transverse cracking. Finally, transverse cracking in pavement composite structures under different bonding conditions needs to be analyzed in the follow-up work.

Peridynamic modeling of early-age cracking behaviour in continuously reinforced concrete pavement

ABSTRACT Continuously reinforced concrete pavement (CRCP) is frequently used for heavy traffic. In CRCP, early-age cracking can be caused by environmental loading freely and randomly, but only certain crack patterns can affect its long-term performance and induce distress such as punchouts. In this work, we introduce a peridynamic model that includes the time dependency of the environmental loading and material properties to investigate the early-age behaviour of CRCP and predict its cracking. The simulation results match those from field observations in terms of crack patterns, average transverse crack spacing, and crack width. We conduct parametric analyses and find the effects changing environmental conditions and design parameters have on crack patterns. An investigation of active crack control demonstrates that the model can be used to determine optimal pre-notch spacing, for specific environmental conditions, that leads to desirable crack patterns.

Prediction of Equivalent Chloride Ion Diffusion Coefficient in Cracked Concrete of the in-Service RC Element

Considering the influence of the visible load-induced transverse cracks on chloride ion diffusion in cracked concrete of the in-service reinforced concrete (RC) elements under marine environment, a typical concrete volume with one transverse crack was taken to establish the governing equation. Assuming the crack widths at the outer lateral and bottom surfaces were equal, a model to predict the equivalent chloride diffusion coefficient in cracked concrete was put forward to consider the influence of the average transverse crack width, crack spacing and crack extending lengths in beam height and width directions on chloride diffusion. Results show that the proposed model can better reflect the variation trend of the equivalent chloride diffusion coefficient with different crack widths in in-service RC elements under marine environment.

Basalt fibre continuous reinforcement composite pavement reinforcement design based on finite element model

Abstract The thrust of basalt fibre (BFRP) tendons will result in narrower transverse crack spacing, decreased load transfer capacity of transverse cracks and voids at the bottom of the slab, which will lead to thrust failure. The thesis uses the finite element analysis method to analyse the material characteristics of BFRP tendons. At the same time, the article determines the critical load position corresponding to the tensile stress of concrete and BFRP tendons, and analyses the influence of voids, crack spacing and other factors on the load stress of concrete and BFRP tendons. The study results found that continuously reinforced concrete and asphalt overlay composite design can reduce cracks.

Basalt fibre continuous reinforcement composite pavement reinforcement design based on finite element model

Abstract The thrust of basalt fibre (BFRP) tendons will result in narrower transverse crack spacing, decreased load transfer capacity of transverse cracks and voids at the bottom of the slab, which will lead to thrust failure. The thesis uses the finite element analysis method to analyse the material characteristics of BFRP tendons. At the same time, the article determines the critical load position corresponding to the tensile stress of concrete and BFRP tendons, and analyses the influence of voids, crack spacing and other factors on the load stress of concrete and BFRP tendons. The study results found that continuously reinforced concrete and asphalt overlay composite design can reduce cracks.

Assessment of California’s Continuously Reinforced Concrete Pavement Practice and Performance

Around 2009, the California Department of Transportation (Caltrans) adopted continuously reinforced concrete pavement (CRCP) as the preferred pavement type for high-volume truck corridors across the state. Over the last decade, Caltrans has constructed more than a dozen CRCP projects in different climates and exposure to different truck volumes. Caltrans was interested in assessing early CRCP performance and identifying potential areas where design, materials, plans, and specifications, and/or construction practices warranted improvement. This project included a review of national CRCP practice, documentation of Caltrans’ statewide practice, and condition assessment of select CRCP projects statewide. For the most part, Caltrans’ CRCP practice is similar to national guidance and other state highway agency practice. A condition assessment of 14 CRCP projects revealed a wide range of performance with various degrees of distresses (i.e., transverse, cluster, and Y-cracking, and punchouts). However, pavements with average transverse crack spacing below Caltrans’ desired lower limit of 3 ft appeared to have acceptable performance. Excessive map cracking, a high percentage of cluster cracking, and initial development of punchouts was evident in sections that appeared to be performing poorly. General recommendations are provided to advance Caltrans’ CRCP practice.

Automated Transverse Crack Mapping System with Optical Sensors and Big Data Analytics.

Transverse cracks on bridge decks provide the path for chloride penetration and are the major reason for deck deterioration. For such reasons, collecting information related to the crack widths and spacing of transverse cracks are important. In this study, we focused on developing a data pipeline for automated crack detection using non-contact optical sensors. We developed a data acquisition system that is able to acquire data in a fast and simple way without obstructing traffic. Understanding that GPS is not always available and odometer sensor data can only provide relative positions along the direction of traffic, we focused on providing an alternative localization strategy only using optical sensors. In addition, to improve existing crack detection methods which mostly rely on the low-intensity and localized line-segment characteristics of cracks, we considered the direction and shape of the cracks to make our machine learning approach smarter. The proposed system may serve as a useful inspection tool for big data analytics because the system is easy to deploy and provides multiple properties of cracks. Progression of crack deterioration, if any, both in spatial and temporal scale, can be checked and compared if the system is deployed multiple times.

Corrosion-Induced Mass Loss Measurement under Strain Conditions through Gr/AgNW-Based, Fe-C Coated LPFG Sensors.

In this study, graphene/silver nanowire (Gr/AgNW)-based, Fe-C coated long period fiber gratings (LPFG) sensors were tested up to 72 hours in 3.5 w.t% NaCl solution for corrosion-induced mass loss measurement under four strain levels: 0, 500, 1000 and 1500 µε. The crack and interfacial bonding behaviors of laminate Fe-C and Gr/AgNW layer structures were characterized using Scanning Electron Microscopy (SEM) and electrical resistance measurement. Both optical transmission spectra and electrical impedance spectroscopy (EIS) data were simultaneously measured from each sensor. Under increasing strains, transverse cracks appeared first and were followed by longitudinal cracks on the laminate layer structures. The spacing of transverse cracks and the length of longitudinal cracks were determined by the bond strength at the weak Fe-C and Gr/AgNW interface. During corrosion tests, the shift in resonant wavelength of the Fe-C coated LPFG sensors resulted from the effects of the Fe-C layer thinning and the NaCl solution penetration through cracks on the evanescent field surrounding the LPFG sensors. Compared with the zero-strained sensor, the strain-induced cracks on the laminate layer structures initially increased and then decreased the shift in resonant wavelength in two main stages of the Fe-C corrosion process. In each corrosion stage, the Fe-C mass loss was linearly related to the shift in resonant wavelength under zero strain and with the applied strain taken into account in general cases. The general correlation equation was validated at 700 and 1200 µε to a maximum error of 2.5% in comparison with 46.5% from the zero-strain correlation equation.

Punchout evaluations and classification of continuously reinforced concrete pavement to improve pavement design

In continuously reinforced concrete pavement (CRCP) research, it has been assumed that transverse crack spacing plays an important role in determining CRCP behaviour and performance. For the longitudinal reinforcement design, the 1993 American Association of State Highway and Transportation Officials (AASHTO) Design Guide recommends a minimum crack spacing of 3.5 ft. The minimum spacing of 3.5 ft is recommended to minimise the occurrence of punchouts. This concept of narrow crack spacing being more prone to punchout has been accepted. Hence, all the available CRCP design algorithms are based on this concept. However, since treated base/non-erodible base is now provided in CRCP, this theory has some discrepancies with the real CRCP performance especially in Texas. In this study, an extensive field evaluation was conducted for the number of punchouts recorded in TxDOT pavement management information system (PMIS). Out of 1472 punchouts, 232 punchouts that developed in major metropolitan Districts in TxDOT were surveyed and evaluated to determine whether punchouts have a relationship with closely spaced transverse cracks and the resulting load transfer efficiency (LTE). Field survey and testing results show that the majority of distresses in CRCP have been caused by quality issues of either materials or construction in the vicinity of transverse construction joint and repair joint.

Optimization of parameters affecting horizontal cracking in continuously reinforced concrete pavement (CRCP)

Field evaluation of distresses in continuously reinforced concrete pavement (CRCP) indicated punch-out distress associated with horizontal cracking at the depth of the longitudinal steel is the most severe performance problem in CRCP. The developed 3-D model was used to perform a parametric analysis to determine the effects of critical loading location, concrete properties, and longitudinal steel design on horizontal cracking potential. The maximum vertical tensile stresses in the concrete were slightly affected by the coefficient of thermal expansion of the concrete. The critical tensile stresses in the concrete were observed to decrease as the base modulus, slab–base friction, slab thickness, and transverse crack spacing increase. The vertical tensile stresses significantly decreased when the longitudinal steel spacing decreased. The use of varying longitudinal steel spacing and reducing the depth of steel may be one of the ways to reduce the horizontal cracking potential without changing the steel ratio of the slab.

Structural behavior of corroded reinforced concrete beams under sustained loading

This paper presents the results of an experimental study designed to investigate the combined effects of corrosion and sustained loads on the structural performance of reinforced concrete beams. A total of eight RC beams, including both uncorroded beams and corroded ones accelerated by the impressed current method, were tested. All the beams were subjected to a four-point sustained bending load which was equivalent to 17%, 33% or 50% of the designed ultimate load, respectively. Corrosion degree, crack patterns, crack width and mid-span deflection of the beams were monitored during the test. The results showed that reinforcement corrosion had no obvious effect on the transverse crack spacing and a slight effect on the development of transverse crack width for the beams under simultaneous loading and corrosion. A higher load level and a lower current density allow for more sufficient oxidation of corrosion products with a larger volume expansion rate, leading to premature initiation and rapid propagation of corrosion cracking, and more obvious deflection development of RC beams. For a beam under simultaneous loading and reinforcement corrosion, the effect of reinforcement corrosion on its deflection cannot be ignored, because it may exceed creep effect at a relatively low corrosion degree.

Evaluation of tension stiffening and momentcurvature of high performance reinforced concrete beams under sustained load.

In this paper, the effects of creep and shrinkage on the deflection and cracking of
 reinforced high performance concrete beams subjected to sustained load type in bending
 are investigated. Mid-span deflections, cracking and surface strain profiles were
 monitored over a 90 day period so that to verify the structural response of HPRC (high
 performance reinforced concrete) beams. Using the results obtained from the
 experiments, the effect on tension stiffening was examined. Four concrete strengths 52,
 95, 96 and 100 MPa were included as a major experimental parameter. The results
 showed that as higher strength concrete was employed, not only cracks along the
 reinforcement more extensive, but also the transverse crack spacing became smaller.
 Thereby, the effective tensile stiffness of the high-performance concrete specimens at
 the stabilized cracking stage was much smaller than those of normal-strength concrete
 specimens. This observation is contrary to the current design provisions, and the
 reduction in the tension stiffening effect by employment of high-performance concrete
 is much greater than that would be expected. Measured surface strains in both the
 tension and compression zones of beams of HPC subjected to sustained load were
 considerably higher than the normal strength concrete beam. This was thought to be
 primarily due to the effects of creep in the compression zone and a higher degree of
 cracking within the tension zone. The progressive long-term increase in deflection is
 shown to be a result of strain development primarily in the compression zone. The
 sustained load is shown to affect the section stiffness most significantly within the early
 stages of loading. Using experimental results, the validity of Eurocode 2 (EC2) is
 examined.

Evaluation of structural responses of continuously reinforced concrete pavement (CRCP) using falling weight deflectometer

The objective of this study is to suggest reasonable structural evaluation method of continuously reinforced concrete pavement (CRCP) using falling weight deflectometer (FWD). The effects of transverse crack spacing and temperature conditions were investigated in CRCP sections with various slab thicknesses and pavement ages. A total of 20 CRCP sections were selected throughout Texas and structural responses were evaluated from 2006 to 2013 for 8 testing years. Test results show that transverse crack spacing has little effect on deflection and load transfer efficiency (LTE). The LTE values were maintained at above 90%, regardless of crack spacing, temperature condition or pavement age. Temperature variations had small effects on deflections at cracks and the mid-slab, but almost no effects on LTE. Maximum deflections and back-calculated k-values appear to be better indicators of structural condition of CRCP than LTE. Load transfer efficiency is not the best indicator of structural condition of transverse cracks in CRCP. Deficiencies in slab support are the primary cause of full-depth distresses in Texas, and back-calculated k-values, which combine both a maximum deflection and the shape of deflection bowl from FWD testing, may be a better indicator of the structural condition of CRCP.

Evolution of damage during the fatigue of 3D woven glass-fibre reinforced composites subjected to tension–tension loading observed by time-lapse X-ray tomography

The development of fatigue damage in a glass fibre modified layer-to-layer three dimensional (3D) woven composite has been followed by time-lapse X-ray computed tomography (CT). The damage was found to be distributed regularly throughout the composite according to the repeating unit, even at large fractions of the total life. This suggests that the through-thickness constraint provides a high level of stress redistribution and damage tolerance. The different types of damage have been segmented, allowing a quantitative analysis of damage evolution as a function of the number of fatigue cycles. Transverse cracks were found to initiate within the weft after just 0.1% of life, followed soon after (by 1% of life) by longitudinal debonding cracks. The number and extent of these multiplied steadily over the fatigue life, whereas the spacing of transverse cracks along with weft/binder debonding saturated at 60% of life and damage in the resin pockets occurred only just before final failure.

Implications of zero-stress temperature for the long-term behavior and performance of continuously reinforced concrete pavement

The excellent performance of continuously reinforced concrete pavement (CRCP) has been well known. Over the years, various efforts are underway to further improve the long-term performance of CRCP in terms of material, design, construction, and quality control. According to the national mechanistic-empirical pavement design guide (MEPDG) developed as part of NCHRP 1-37A, one of the material factors with a substantial effect on the long-term performance of CRCP is zero-stress temperature (ZST) of early-age concrete. However, there is no documented evidence that the long-term performance of CRCP depends on ZST. In this paper, implications of ZST for the long-term behavior and performance of CRCP are investigated. To accomplish this objective, a series of field evaluations was made in seven experimental CRCP sections with known material properties, design details, and early-age temperature histories, all of which are as old as 7–22years after construction. Performance indicators such as transverse crack spacing, crack width, and typical CRCP distresses, namely punchout and spalling, were evaluated and then compared with the ZST to find a possible correlation between ZST and resulting CRCP performance. Results revealed that there is no strong correlation between them, which suggests needed improvements to the current MEPDG considering more realistic CRCP behavior.

Mechanism of Transverse Crack Development in Continuously Reinforced Concrete Pavement at Early Ages

The transverse crack in continuously reinforced concrete pavement (CRCP), more specifically transverse crack spacing and crack widths, has been cited as one of the most important pavement structural responses determining CRCP performance. Efforts have been made to predict crack spacing and crack widths for given environmental conditions and traffic loading, pavement structure, and material properties, with the primary objective of developing rational CRCP designs. However, that most transverse cracks develop at or near transverse steel implies substantial interactions between transverse steel and other factors causing transverse cracks. These interactions have not been fully incorporated in the theoretical models developed so far to predict transverse crack spacing and crack widths in CRCP. This study investigated the interactions between transverse steel and other factors and identified the mechanisms of transverse crack development at or near the transverse steel. Drying shrinkage and temperature drop in concrete cause concrete volume contractions in all directions (not just transverse and longitudinal, but vertical directions as well). Interactions between concrete volume contraction vertically and transverse steel cause larger concrete tensile stresses at or near transverse steel than at other areas and cause a higher probability of transverse cracks near transverse steel. Traditionally, subgrade drag theory has been used in the design of transverse steel even though current practice is to place just enough transverse steel to support longitudinal steel during concrete placement. If transverse cracks have such substantial effects on CRCP performance as currently thought, interactions between transverse steel and other factors should be considered in the design of optimum transverse steel.

Investigation and Analysis on Transverse Crack Spacing Distribution in Continuously Reinforced Concrete Pavement in China

The longterm field investigations in the US showed that punchouts were the most important distress in continuously reinforced concrete pavement (CRCP) and often developed in the cluster cracking with the crack spacing of 0.3m-0.6m. But, it was not sure whether punchouts were the most important distress in CRCP in China, so this paper carried out field investigations on several CRC pavements in China. Results showed that punchouts were the most serious distress and often occurred in cluster crack regions. Furthermore, this paper analyzed the transverse crack spacing distribution. Results showed that the transverse cracks spacing distribution followed Weibull’s distribution.