scholarly journals Study on Mechanics-Based Cracking Resistance of Semiflexible Pavement Materials

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Duanyi Wang ◽  
Xiayi Liang ◽  
Danning Li ◽  
Hehao Liang ◽  
Huayang Yu
Keyword(s):  
Numerical Simulation ◽  
Internal Stress ◽  
Cement Mortar ◽  
Material Design ◽  
Air Voids ◽  
Pavement Materials ◽  
Indirect Tensile ◽  
Optimal Material ◽  
Air Void ◽  
Contraction And Expansion

Semiflexible mixture is a composite paving material combining the advantages of both asphalt and cement concrete materials. It consists of matrix asphalt skeleton and cement mortar. Due to the different volume characters between asphalt structure and cement mortar, stress concentration always happens in this semiflexible mixture, leading to internal cracking. The objective of this study is to alleviate the internal cracking concern of the semiflexible mixture by adjusting the material components. To this end, optimal material design and numerical simulation have been conducted. Matrix asphalt structures with four different air voids were incorporated with different dosages of cement mortar. The contraction strain and expansion strain of cement mortar as well as the indirect tensile strength of matrix asphalt structure were measured. The results were input into ABAQUS for numerical simulation. The results indicated that (1) the internal stress in this semiflexible mixture is mainly determined by the contraction of cement mortar, rather than expansion; (2) larger air void of matrix asphalt structure and less volumetric variation of cement mortar reduce the internal stress; (3) once the air void of matrix asphalt structure is decided, both maximum contraction and expansion deformations of cement mortar should meet specific requirement to ensure less internal cracking. This is a practical-ready paper that provides reference for the anticracking design of semiflexible pavement.

scholarly journals Comparing the Field and Laboratory Curing Behaviour of Cold Recycled Asphalt Mixtures for Binder Courses

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4697
Author(s):  
Gilda Ferrotti ◽  
Andrea Grilli ◽  
Chiara Mignini ◽  
Andrea Graziani
Keyword(s):  
Mechanical Performance ◽  
Complex Modulus ◽  
Material Design ◽  
Asphalt Mixtures ◽  
Laboratory Simulation ◽  
Curing Time ◽  
Recycled Asphalt ◽  
Air Voids ◽  
Indirect Tensile

The cold recycling of reclaimed asphalt (RA) for the rehabilitation of end-of-life pavements is becoming very common. Cold recycled asphalt mixtures (CRAMs) are characterised by a curing time, required to reach the material design mechanical performance. Since the laboratory simulation of the long-term field curing is not yet a standardised procedure, a CRAM was laid as binder course in a full-scale trial section that was monitored for more than two years. The comparison between field curing and oven-curing in laboratory at 40 °C was performed by carrying out indirect tensile stiffness modulus (ITSM), indirect tensile strength (ITS) and complex modulus tests, as well as measurements of the air voids content. The evolution of the ITSM as a function of the curing time (field/oven-curing) was obtained for both gyratory specimens and cores taken from the trial section at different time periods. Results showed that the material stiffness development can be accelerated with a small effect on its long-term value if oven-curing is applied a few days/weeks after compaction. A linear relationship was found between the ITS measured on the cores and their air voids content. Finally, the complex modulus tests confirmed that CRAMs provide an intermediate behaviour between asphalt concrete mixtures and cement-bound mixtures.

scholarly journals Moisture Susceptibility of Warm Mix Asphalt (WMA) with an Organic Wax Additive Based on X-Ray Computed Tomography (CT) Technology

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Jie Ji ◽  
Hui Yao ◽  
Zhikai Yuan ◽  
Zhi Suo ◽  
Ying Xu ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Moisture Content ◽  
Void Content ◽  
Moisture Susceptibility ◽  
Air Voids ◽  
X Ray ◽  
X Ray Computed ◽  
Indirect Tensile ◽  
Air Void ◽  
Air Void Content

The warm mix asphalt was fabricated with different moisture contents (0%, 1%, 2%, and 3%) of limestone aggregates using the Superpave gyratory compactor. The moisture susceptibility of asphalt mixtures with an organic wax additive RH was studied. The samples were compacted and tested using the modified Lottman test AASHTO T283, and the X-ray computed tomography technology was used to capture the internal structure images before and after the freeze-thaw cycles. The test results show that the air voids were distributed in the size range of 0–5 mm3 and 5–10 mm3. The number of air voids decreased with the increase of air void size and increased after freeze-thaw cycles. The air void content can be influenced by the residual moisture in aggregates. The higher the moisture content of aggregates is, the larger the air void content is. So, the air void content is likely to be sensitive to moisture damage. The increase ratio of the air void and moisture content of aggregates had good correlation with the indirect tensile strength and tensile strength ratio of the samples. The indirect tensile strength and tensile strength ratio of the samples decreased linearly, and the samples were sensitive to the moisture damage with the increases of increase ratio of the air void/moisture content in aggregates.

scholarly journals A GPR-Based Pavement Density Profiler: Operating Principles and Applications

2021 ◽  
Vol 13 (13) ◽  
pp. 2613
Author(s):  
Nectaria Diamanti ◽  
A. Peter Annan ◽  
Steven R. Jackson ◽  
Dylan Klazinga
Keyword(s):  
Asphalt Pavement ◽  
Wave Impedance ◽  
Asphalt Mixtures ◽  
Void Content ◽  
Air Voids ◽  
New Instrument ◽  
Pavement Engineering ◽  
And Performance ◽  
Air Void ◽  
Air Void Content

Density is one of the most important parameters in the construction of asphalt mixtures and pavement engineering. When a mixture is properly designed and compacted, it will contain enough air voids to prevent plastic deformation but will have low enough air void content to prevent water ingress and moisture damage. By mapping asphalt pavement density, areas with air void content outside of the acceptable range can be identified to predict its future life and performance. We describe a new instrument, the pavement density profiler (PDP) that has evolved from many years of making measurements of asphalt pavement properties. This instrument measures the electromagnetic (EM) wave impedance to infer the asphalt pavement density (or air void content) locally and over profiles.

Numerical simulation of contraction and expansion flows of fiber suspensions

1994 ◽  
Vol 38 (3) ◽  
pp. 753-753
Author(s):  
Kazunori Yasuda ◽  
Kiyoji Nakamura ◽  
Noriyasu Mori
Keyword(s):  
Numerical Simulation ◽  
Fiber Suspensions ◽  
Contraction And Expansion

Influence of Air Content and Vibration Time on Frost Resistance of Air Entrained Concrete

2013 ◽  
Vol 857 ◽  
pp. 110-115 ◽  
Author(s):  
Xiu Hua Zheng ◽  
Yong Ge ◽  
Jie Yuan
Keyword(s):  
Frost Resistance ◽  
Hardened Concrete ◽  
Air Voids ◽  
Air Content ◽  
High Durability ◽  
Void Structure ◽  
Vibration Time ◽  
Air Void ◽  
Air Void Structure ◽  
Air Entrained Concrete

Air-entraining agent turely is one of the necessary compositions of the high durability concrete. The influence of air content and vibration time on the frost resistance of concrete was researched, and air void characteristics of hardened concrete was analysed. The results showed that the air contents could reduce the compressive strengthof hardened concrete excessively, but it made the spacing factor reduce obviously and significantly improve the frost resistance of concrete.The air voids with different structure in concrete were realized by vibration time. It was found that the air void structure and the frost resistance properties were influenced by the vibration time largely. The optimized vibration time is 30s, the appropriate vibration time is 20s~30s, no more than 35s.

Detection of Sizes and Locations Air Voids in Reinforced Concrete Slab using Ground Penetrating Radar and Impact-Echo Methods

2015 ◽  
Vol 74 (3) ◽  
Author(s):  
Nurhayati Abdul Razak ◽  
Syahrul Fithry Senin ◽  
Roszilah Hamid
Keyword(s):  
Reinforced Concrete ◽  
Ground Penetrating Radar ◽  
Concrete Slab ◽  
Depth Estimation ◽  
Reinforced Concrete Slab ◽  
Air Voids ◽  
Impact Echo ◽  
Void Defects ◽  
Ground Penetrating ◽  
Air Void

 The presence of inevitable air void defects in reinforced concrete components due to poor quality control during construction can further aggravate the moisture and chloride penetration in concrete to accelerate the corrosion process of the reinforcing steel. Non-destructive test  (NDT) methods, Ground Penetrating Radar (GPR) and Impact-Echo (IE), are utilised tp detect the void defects. This study is to compare the accuracy and limitations of both methods in detecting the sizes and depths of the air voids. The sample is a 600 × 400 ×200 mm3 reinforced grade 40 concrete slab with embedded air voids in the sample. The air-voids are introduced in the concrete slab by positioning air-void plastic balls with diameters of 67, 45, 27, 20 and 3 mm each at the depths of 70, 80, 100, 80 and 80 mm, respectively, from the top surface of the slab. Results show that GPR can detect the air voids with sizes larger than 20 mm in diameter with error ranging from -8.9 to 30% from their actual diameters. The IE method is only able to detect the air voids depths and not the voids’ sizes. It is also observed that the void depth estimation acquired by GPR is more accurate only for large size void (67 mm), but for sizes less than that, IE is more accurate in determining their locations. Both methos should be considered for NDT application in detecting voids depending on which parameter accuracy is inticipated.  

scholarly journals Numerical Simulation Virtual Test of Torsion Shear for Asphalt Mixture

2019 ◽  
Vol 2019 ◽  
pp. 1-21
Author(s):  
Jun Xie ◽  
Yougang Yang
Keyword(s):  
Numerical Simulation ◽  
Shear Failure ◽  
Failure Process ◽  
Asphalt Mixture ◽  
Test Method ◽  
Reconstruction Method ◽  
Virtual Test ◽  
Torsional Shear ◽  
Shear Process ◽  
Air Void

In order to analyze the torsional shear process of asphalt mixtures in a microscopic view, the numerical simulation of a torsional shear test of an asphalt mixture was carried out by discrete element method. Based on the defects of existing algorithms, the method of random reconstruction of the existing 3D model of the asphalt mixture was improved, and a new reconstruction method was proposed. A 3D numerical model of the asphalt mixture contained irregular-shaped coarse aggregate, mineral gradation, and asphalt mortar; furthermore, the particle algorithm established the air void distribution. Then, the numerical simulation of the asphalt mixture’s torsional shear was completed; in addition, the stress, displacement, and contact of the specimens at each stage were analyzed. The results showed that the stress and displacement in different stages changed greatly with the loading, i.e., the crack generated from a weak point on the surface and then spread to the ends with an oblique angle of about 45°. At the same time, the shear failure process of the asphalt mixture was studied. The virtual test method could accomplish the implementation of the numerical simulation of torsional shear; it also provided a good research method for analysis of the asphalt mixture’s shear failure process.

scholarly journals Preparation of Asphalt Concretes by Gyratory Compactor: A Case of Study with Rheological and Mechanical Aspects

2020 ◽  
Vol 10 (23) ◽  
pp. 8567
Author(s):  
Paolino Caputo ◽  
Pietro Calandra ◽  
Rosolino Vaiana ◽  
Vincenzo Gallelli ◽  
Giovanni De Filpo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Activation Energy ◽  
Energy Savings ◽  
Tensile Deformation ◽  
Environmental Issues ◽  
Exponential Factor ◽  
Air Voids ◽  
Chemical Mechanisms ◽  
Physico Chemical ◽  
Indirect Tensile

For asphalt concrete preparation in laboratory mix-design operations, bitumens are usually mixed with micrometer-sized particles (filler), sand and centimeter-sized crushed stones in a gyratory press at a temperature of about 140–155 °C depending on the bitumen viscosity, until adequate homogenization and compaction take place (air voids optimum). This requires energy consumption. To minimize it, the process needs to be optimized and is usually made empirically. The aim of this manuscript is to gain a comprehension of the physico-chemical mechanisms involved in the process by exploring: (i) the rheological properties (viscosity, activation energy) of a neat and RTFOT-aged bitumen, in presence and in absence of a filler, (ii) the volumetric and resistance behavior under the compaction in a standard Gyratory Compactor (GC) of their blends with aggregates and (iii) the mechanical properties (Indirect Tensile Strength, compression and tensile deformation) of the final products. Correlations between activation energy and pre-exponential factor of the viscosity on a side, and between viscosity, workability and final mechanical properties on the other side allowed to provide a rational interpretation of the physico-chemical processes involved in the framework of the physics of complex fluids. The scientific clues will be of help in optimizing the workability in asphalt concretes productions with obvious repercussions in terms of energy savings, useful for economic and environmental issues.

scholarly journals Experimental Study on the Performance Decay of Permeable Asphalt Mixture in Seasonally Frozen Regions under Freeze-Thaw Cycles

2020 ◽  
Vol 12 (7) ◽  
pp. 2966 ◽  
Author(s):  
Chao Chai ◽  
Yong-Chun Cheng ◽  
Yuwei Zhang ◽  
Yu Chen ◽  
Bing Zhu
Keyword(s):  
Acoustic Emission ◽  
Asphalt Mixture ◽  
Temperature Stability ◽  
High Temperature Stability ◽  
Air Voids ◽  
Particle Loss ◽  
Seasonal Freezing ◽  
Freeze Thaw ◽  
Splitting Test ◽  
Air Void

This paper focuses on the freeze-thaw cycles (F-T cycles) resistance of porous asphalt mixture (PAM) with different air voids in order to explore the gradation of the PAM suitable for seasonal freezing regions. Three sets of PAMs with 18%, 21%, and 25% air voids were designed. After 0–20 F-T cycles, the effects of F-T cycles on the performance degradation of three groups of PAMs were studied by performing a low-temperature splitting test with acoustic emission technology, a normal temperature splitting test, a compression test, a Cantabro particle loss test, and a dynamic creep test. The results show that the damage process of PAM caused by multiple F-T cycles could be more clearly defined by acoustic emission parameters. In addition, the larger the air void, the smaller its indirect tensile strength and compression strength, and the worse its particle loss resistance and high-temperature stability, which made the adverse effect of F-T cycles more significant. Therefore, the air void of PAM used in seasonal freezing regions is suggested to be less than 21%.

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