Anti-cracking Performance Research Articles

STUDY ON ANTI-CRACKING PERFORMANCE EVALUATION METHOD OF STEEL FIBER REINFORCED CERAMSITE CONCRETE (SFRCC) BASED ON PARTLY-RESTRAINED SHRINKAGE RING

In the study of crack resistance of steel fiber reinforced concrete in steel fiber on concrete deformation ability and prevent the Angle of the micro cracks, and the lack of overall evaluation on the performance of steel fiber reinforced concrete crack. By tinder barrier-free restrain some experimental research on steel fiber ceramsite concrete shrinkage ring crack resistance, and use the test results within the definition of steel ring strain from expansion to contraction cut-off age for early and late ages, and the ages of the cut-off point for the early and the late steel fiber ceramsite concrete anti-cracking performance evaluation. The results show that the anti-cracking properties of the steel fiber ceramic concrete are improved with the increase of steel fiber content.

Mixed-mode fracture modeling of cold recycled mixture using discrete element method

Cold recycling (CR) consists of recycling asphalt pavement without the application of heat during the recycling process to produce rehabilitated pavements. Compared to other reconstruction methods, CR has advantages in energy conservation and economic saving. This paper aims to develop a three-dimensional (3D) numerical model of the Arcan test to simulate the mixed-mode cracking behavior of CR mixtures and to find the differences between CR and hot-mix asphalt (HMA) mixture. A rotatable test device was specially designed for the Arcan test to evaluate the mixed-mode cracking of specimens. A 3D numerical specimen of CR mixture was set up in the program PFC3D 4.0. A modified bilinear fracture model was established for asphalt mastic and the material parameters in the model were determined from laboratory tests. The results of virtual Arcan test verifies that three of five mixed-mode cracking simulations are reliable compared to the experimental results and 50% Mode I cracking shows the minimum error among three modes. During the cracking process of any mode, the stress concentration always occurs at the tip of cracking, and the stress value of cracking tip decreases as the cracking propagates. Compared with HMA mixtures, the emulsified CR mixture has a larger failure strain and a smaller failure stress, which can show a better anti-cracking performance in the practical engineering.

Identifying the rheological properties of polymer-modified bitumen based on its morphology

This paper is an attempt to identify the relationship between morphology and performance of polymer-modified bitumen (PmB) containing styrene–butadiene–styrene (SBS) copolymer and carbon nanotubes (CNTs). Morphology is defined as the partition of polymer-rich and bitumen-rich phases, which is obtained by fluorescence microscopy and atomic force microscopy. Rheological properties of PmB are captured by Master curve, Han curve, and Cole–Cole curve. Three different bitumen samples with same polymer amount were selected in this paper. The results showed that a dense network and the interlocked structure in SBS phase provided a better anti-rutting property of PmB. Han curve demonstrated that the elastic modulus improvement of PmB had a close relationship with the size of SBS phase. Cole–Cole curve illustrated that the smaller size and interlocked structure of SBS phase prevented the movement of SBS phase and presented a higher loss viscosity at low-driving speed condition. Furthermore, CNTs played a positive role on the anti-aging property, storage stability, and anti-cracking performance of SBS-modified bitumen.

Silane coupling agent on rheological performance of basalt fiber-reinforced asphalt mucilage

ABSTRACTDue to the lack of study on basalt fiber (BF)-reinforced asphalt mucilage based on silane coupling agent (SCA) modification, researchers used SCA to modify BF and then prepared fiber-reinforced asphalt mucilage (FRAM) specimens. FRAM's high- and low-temperature rheological performances were evaluated by BBR and DSR and the reinforcement mechanism of modified BF (MBF) was analyzed by ESEM and FTIR. Tests showed that the number of MBF's Si–O–Si bonds increased. MBF was rough, which was responsible for fiber's mechanical property and multi-direction-bridging reinforcement. When the powder–binder ratio was between 0.8 and 1.0 and the MBF content was between 0.3% and 0.6%, FRAM's anti-shearing and anti-cracking performances enhanced efficiently.

Properties of Printer Waste Toner Modified Bitumen

For the deficiency of the existing technology of petroleum bitumen, the printer (copier) waste toner (PWT) as the major additive, a proper amount of aluminate coupling agent and stearic acid synergist as the auxiliary additive were added to the base bitumen. A new kind of modified bitumen was developed and prepared. In order to evaluate the technical performance of the PWT modified bitumen and the bituminous mixtures, especially assess the high temperature performance, we compared the softening point and PG grade of Qilu 70# base bitumen and the PWT modified bitumen, and compared the Marshall test and rutting test results of the PWT modified bituminous mixtures and Qilu 70# bituminous mixtures. The results show that the PWT can improve the softening point of base bitumen about 3°C-8 ℃, accordingly, not only improve the high temperature stability of bituminous mixtures, reduce rutting, but also maintain the low temperature anti-cracking performance of bitumen and bituminous mixtures and show the good social, economic and environmental protection benefits. This technology overcomes the technical problem, the low temperature performance is sorry to be reduced when the high temperature performance is improved, which is posed by only adding the PWT to the base bitumen.

Stress and damage in concrete induced by pipe cooling at mesoscopic scale

Pipe cooling is one of the most important measures of mass concrete temperature control, but pipe cooling has its advantages and disadvantages. Inappropriate pipe-cooling water temperature may result in excessive stress and crack. Considering the fact that concrete is a type of three-phase composite material and the sizes of cooling pipe and aggregate are basically on the same scale, the mesoscopic heterogeneity of concrete may have a great effect on the stress field surrounding the pipe. This article computes the pipe cooling–induced stress and damage and analyzes the differences between the homogeneous model and heterogeneous model based on mesoscopic mechanics. In this study, both linear elastic analysis and nonlinear damage analysis are performed; elastic modulus and creep are used as a function of concrete age; and several factors such as temperature difference, multistep cooling mode, and earlier cooling are also studied. The research results show that due to the mesoscopic heterogeneity characteristics of concrete, there is a great deal of difference between homogeneous model and heterogeneous model; pipe cooling can lead to large residual stress around the aggregate and produce a large range of damage, and previous homogeneous model indeed underestimates the effect of cooling-induced stress; using multistep cooling and early cooling mode can reduce this damage; the cooling-induced damage has significant influence on the anti-crack performance of concrete. In the final, based on the research results, the temperature difference between the concrete and pipe water of the second-phase cooling was recommended to be controlled at approximately 5°C.

Effect of Chemical Admixture on Durability of Concrete

In this paper, the effect of the polynaphthaene sulphonate type water reducer (PSWR) and new type polycarboxylate water reducer (PAWR) on the internal pore structure, internal defects and forces of resistance to external environmental of concrete are fully compared and analyzed. The effect of PAWR on improving the durability of concrete was revealed. The test result showed that compared with PSWR, PAWR can improve the pore structure and pore size distribution of concrete grout, improve the density of concrete, reduce the adiabatic temperature rise of concrete, optimize the hydration heat curve of cement, reduce the shrinkage and deformation of concrete, improve concrete anti-cracking performance and volume stability, to reduce the internal defects of concrete; at the same time, but also to improve the ability of the concrete, including anti- carbonation, frost resistance, chloride ion erosion resistance and steel protection in different degree, as well as to enhance the resistance of concrete to the external environment, thereby greatly improving the durability of concrete.

Accelerated water tree aging of crosslinked polyethylene with different degrees of crosslinking

The effect of crosslinking degree on accelerated water tree aging in crosslinked polyethylene (XLPE) was investigated. The peroxide-crosslinking process was adopted to make XLPE specimens with different degrees of crosslinking by controlling the doping content of dicumyl peroxide (DCP) in low-density polyethylene (LDPE). The water blade electrode method was applied to accelerate water-tree aging of LDPE and XLPE specimens (hereafter referred to as the specimens), and their morphologies were observed using an optical microscope. The variation of crystalline morphology and anti-cracking performance of the amorphous region in the specimens were analyzed by differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and an electronic universal testing machine. Based on the experimental results, it was found that XLPE has great anti-water-treeing performance compared to LDPE. In addition, the higher the crosslinking degree, the better the anti-water-treeing performance. Although crystal growth is inhibited due to the crosslinking reaction, the density of tie molecular chains greatly increases in the amorphous region and exhibits significantly tighter lamellar stacking, which is the reason that water tree growth is restrained with increasing crosslinking degree.

Performance of porous asphalt mixture with various additives

The objective of this study is to evaluate the approaches to improve the durability and strength of the porous asphalt through laboratory testing. Porous asphalt specimens were prepared using three types of binders: high-viscosity binder (HVB), PG76-22 and PG70-22. Various additives: fibre, hydrated lime and DBS polymer, were utilised in the porous asphalt. Comprehensive laboratory tests, including strength test, binder draindown test, Cantabro abrasion test, moisture susceptibility test, rutting test, thermal stress restrained sample test, and permeability test, were conducted. It is found that HVB significantly improved the overall performance of the porous asphalt; DBS additive improved its high-temperature performance, but lowered the cracking resistance at low temperature as well as the durability; fibre enhanced its durability and anti-cracking performance at low temperature; hydrated lime improved its moisture stability while weakening its durability. It is concluded that HVB and polyester fibre should be used in all porous asphalt; DBS additive is good for porous asphalt in high-temperature areas, and hydrated lime can be added to porous asphalt in rainy areas.

Investigation of the properties of asphalt mixtures incorporating reclaimed SBS modified asphalt pavement

With the increasing environmental considerations and rising costs of construction materials, reclaimed asphalt pavement (RAP) has been frequently added into asphalt paving mixtures during pavement construction. Many studies have been conducted with regard to the study of reclaimed unmodified asphalt pavement, but the reclaimed SBS modified asphalt pavement is still unknown. In this study, the effects of RAP and rejuvenating agent on the performance were studied. The moisture susceptibility, rutting resistance, dynamic modulus, low temperature anti cracking performance and fatigue was tested. Furthermore, in order to better understand the effects of RAP and rejuvenating agent, the control asphalt mixture was measured using the same methods. The results indicated that the asphalt mixture incorporating reclaimed SBS modified asphalt pavement with better moisture susceptibility, rutting resistance, dynamic modulus, low temperature anti cracking performance and fatigue resistance was obtained by blending new SBS modified asphalt binder and rejuvenating agent. Thus, the rejuvenating agent will benefit the effort of preparing more sustainable asphalt pavement containing RAP.

Characterization of Low Temperature Crack Resistance of Crumb Rubber Modified Asphalt Mixtures Using Semi-Circular Bending Tests

AbstractThe objective of this study was to assess the low temperature anti-cracking performance of crumb rubber modified asphalt mixtures by performing the semi-circular bending tests. The flexural tensile strength, fracture energy density, and fracture resistance were used to evaluate the rubber modified asphalt mixture's performance based on fracture mechanics J-integral concept. The semi-circular bending (SCB) tests were conducted to study the effect of crumb rubber dosage, crumb rubber size, and testing temperature on the low temperature anti-cracking performance of rubber modified asphalt mixtures. Two gradations (a dense gradation mixture and a gap-gradation mixture) were selected, and five rubber application dosages (15, 18, 20, 22, and 25 %, all by the weight of base binder) were studied in the paper. The tests were performed at temperatures of 0, −10, and −20°C. The testing results indicated that the flexural tensile strength and fracture energy density increased initially, reached to a peak point and then decreased with the increase of rubber dosage. Flexural tensile strength and fracture energy density reached its maximum value at the 20 % rubber dosage among the five rubber application dosages. The flexural tensile strength, fracture energy density, and the J-integral fracture toughness of the gap-graded rubber asphalt mixture specimens were higher than those of the dense gradation. The smaller sized particle rubber modified mixture provided a better low temperature anti-cracking performance as compared to those with bigger particle sizes. Through the comprehensive consideration of laboratory test results and field results, it was recommended that the J-integral fracture toughness should be no less than 2.8 KJ/m2 for new asphalt rubber pavement in Shannxi province.

Expansive and mechanical properties of textile reinforced self-stressing concrete

To improve the crack resistance of concrete, textile-reinforced self-stressing concrete was prepared by combining self-stressing concrete and textile. The confinement effect of textile on the concrete matrix allows for the establishment of self-stresses in the matrix, which can highly enhance crack resistance. In this research, expansion deformations of self-stressing concrete under unconfined and confined conditions were measured. Furthermore, co-workability between self-stressing concrete matrix and textile was evaluated through pull-out and compressive experiments. Finally, section analysis method was used to analyze the anti-crack performance and flexural behavior of textile-reinforced self-stressing concrete. The textile and self-stressing concrete are found to work well together, and textile-reinforced self-stressing concrete can largely improve the crack resistance of concrete materials.

Relationship between fracture toughness and temperature in epoxy coatings

Relationship between fracture toughness and temperature in epoxy coatings

Shear Capacity Research on Transversely Reinforced Concrete Beams

Inner transverse prestressed bars were used to enhance the shear capacity of concrete beams in this paper, which can be used in transformer beams to reduce the sectional size. Two transversely prestressed one ordinary concrete beams were tested and calculated by finite element method, and the following conclusions can be drawn: (a)The shear capacity of transversely prestressed concrete beam increase rapidly with the increase of the prestressing force level, which means that prestressing force level has a great influence on the shear capacity of transversely prestressed concrete beam. (b) The transverse prestressing bars can efficiently enhance the anti-crack performance of the reinforced concrete beams.

Experimental Research on Anti-Cracking Ability of Polyacrylonitrile Fiber Mortar

This paper adopts panel constraint method to research the influence of different mixing amount of polyacrylonitrile fiber on plastic cracking of mortar. The research result shows that polyacrylonitrile fiber can prevent cracking and refine the cracks, and the effect will become more obvious with increase of its mixed amount. When the mixed fiber in mortar is more than 1.0kg/m3, the crack can be reduced to more than 90%. The best mixed amount of polyacrylonitrile fiber in mortar is 1~1.5kg/m3. This experimental result can provide theoretical basis for improving anti-cracking performance of mortar or concrete.

Impact of the implementation of continuous construction method on pavement cracking performance

A continuous construction method (CCM) was proposed to decrease the reflective cracking generated from the cement-treated macadam base by reducing the shrinkage of base materials and improving the bond strength at the interface between the base layer and surface layer. Traditional 3–7 days of curing period of cement-treated macadam base was eliminated by CCM and the asphalt mixture can be paved immediately after the construction of cement-treated macadam base. An anti-cracking agent was developed and added into the cement-treated base materials to prolong the hydration process and improve the shrinkage performance of base materials. The influences of anti-cracking agent on the properties of cement-treated materials were analysed using laboratory tests. The generation of micro-expansion ettringite from cement system was investigated from the microscopic perspective using the scanning electronic microscope test. Test roads were constructed and contrasted to demonstrate the feasibility of this approach and showed a superior anti-cracking performance.

Effect of Warm Mix Addictive EC120 on Asphalt Performance

In order to study the effect of warm mix addictive EC120 on asphalt performance, tests on asphalt density, penetration degree, softening point and ductility were carried out through adding various contents of EC120 to 70# paving asphalt (A grade) and SBS I-D polymer modified asphalt. The results indicate that when adding 3% content of EC120, the modification effect for these two kinds of asphalts is the best. The penetration degree of 70# paving asphalt decreases greatly than that for SBS polymer modified asphalt, but softening point increases small. The warm mix agent EC120 can improve the high-temperature stability and low-temperature anti cracking performance of asphalt. It has wide application prospect.

A Study on Anti-Cracking Performance of Lime and Fly-Ash Stabilized Coal Gangue Roadbase Materials

In order to determine the mix proportion with better anti-cracking performance of lime and fly-ash stabilized coal gangue roadbase materials, anti-cracking performance of lime and fly-ash stabilized coal gangue influenced by quality ratio of lime to fly-ash was studied based on the same aggregate gradation and the same aggregate ratio. And then crack of test road with different mix proportion was observed. Results show that both temperature shrinkage anti-cracking coefficient and drying shrinkage anti-cracking coefficient vary along parabola rule with the decrease of the quality ratio of lime to fly-ash. The mixture have the best anti-cracking performance when the quality ratio of lime to fly-ash is 5:15, which was test and verify in the transverse crack observations of test road. Lime and fly-ash stabilized coal gangue roadbase materials have a good anti-cracking performance and suitable for base in the pavement structure. The reasonable ratio of lime and fly-ash stabilized coal gangue roadbase materials in the engineering should be 5:15:80.

Natural Mineral Fiber Improved Asphalt Mixture Performance

Natural mineral fiber with good performances of mechanical properties and environmentally friendly, pollution-free especially have gradually aroused extensive concern. In order to improve the quality of asphalt pavement, explore the applicability of nature basalt fiber in enhanced asphalt mixture performance, this paper investigates two typical asphalt mixtures and contrastive studies pavement performance of asphalt mixture by high temperature stability, water stability, low temperature anti-cracking and fatigue performance between basalt fiber modified asphalt mixture and base asphalt mixture, and then study the basic principle of fiber reinforcing asphalt mixture. The research show that basalt fiber modified asphalt mixture has a better pavement performance than base asphalt mixture, its dynamic stability is 1.6 times than base asphalt mixture, low temperature anti-cracking performance increased by more 25% and fatigue life is more 2 times than base asphalt mixture. And the basalt fiber can be used in the road engineering as an additive material that enhances the comprehensive performance of asphalt pavement.

Grey Relational Analysis of Fiber Asphalt Mixture Based on Pavement Performance and Economic Benefits

In order to explore performance and economic benefits of the most commonly used fiber asphalt mixture, four types of fiber asphalt mixture were studied in this paper through a series of capability tests, such as water stability, high stability, low temperature crack resistance and fatigue stability test. Based on dynamic stability, low temperature bending strain, freeze-thaw splitting strength ratio, fatigue life and cost per square meter as the evaluation index, Grey Relational Analysis (GRA) was proposed in this study to determine the best performance and economic benefits of fiber asphalt mixture. The results show that Fiber B asphalt mixture only has better anti-cracking performance in low temperature and fatigue life,but fiber C asphalt mixture has better performance and economy than the other three fiber asphalt mixtures under the same conditions with grey relational analysis.