Experimental and numerical study on improving mechanical properties of new polyurethane-emery thin polymer overlay (TPO) structure using three-point bending test

https://doi.org/10.1016/j.conbuildmat.2022.129992Get rights and content

Highlights

  • Thin polymer overlay (TPO) is an advanced road surface treatment layer used for the repair reinforcement of roads.

  • A polyurethane-emery TPO composite material with better mechanical performance was proposed.

  • The mechanical behaviors of the polyurethane-emery TPO reinforced with steel fiber and cement materials are investigated.

  • New polyurethane-emery TPO system can be used in the development of the bridge surface treatment reinforcement formwork.

Abstract

The thin polymer overlay (TPO) is a new type of road surface treatment layer for high traffic pressure and high road performance requirements. Therefore, it is not only widely used on highways but also has more and more applications in the field of bridge deck pavement. In this work, a new type of TPO—the polyurethane-emery TPO composite material was proposed, and a reasonable material mixing ratio is determined. In addition, the flexural and compressive behaviors of the polyurethane-emery TPO reinforced with the steel fiber and cement materials are investigated, and a comparison is made for the development of a numerical model to simulate the behavior of the reinforced-new-TPO using the Finite Element (FE). The experimental tests include three-point bending and compressive tests to evaluate the ultimate capacity of the new-TPO material in flexural and compression and its modulus of elasticity. Moreover, the flexural and compression performance of polyurethane-emery TPO containing different reinforcement configurations was evaluated in three-point bending and compression tests, and the reinforcing effects of different steel fibers and cement contents were investigated. The use of steel fiber and cement-reinforced thin polymer overlay in reinforced bridge surface treatment construction was found to be able to significantly offer several advantages, such as excellent corrosion resistance, and flexural and compression strength. Through experimentation, it can be seen that the new type of polyurethane-emery TPO proposed in this paper can completely replace the existing TPO, however, the effect of the dosage of steel fiber and cement needs to be considered during the design. Meanwhile, a three-dimensional nonlinear finite element model was established by using ABAQUS, which incorporated the second development model of steel fiber based on python and CDP models and can be used to predict the flexural and compression behaviors. The numerical model was experimentally validated by using the three-point bending and compression test results and was used for parametric studies. The parameters investigated in this study were steel fiber content, fiber length, and polyurethane-cement ratio of the polyurethane-emery TPO reinforcement. The proposed new polyurethane-emery TPO system was revealed to be promising for the development of the bridge surface treatment reinforcement formwork and can be used in superstructure construction for the extension of the bridge service life. The numerical and the experimental results were generally in good agreement.

Introduction

The most notable characteristic of thin polymer overlay (TPO) is its dense microstructure with thin thickness and lightweight, which results in superior anti-sliding, anti-rutting, anti-wearing, and long-term durability [1], [2], [3], [4]. The current ultra-thin wear overlay material is usually an asphalt mixture, such as SMA, AC, OGFC, Superpave and Novachip, etc [5], [6], [7], [8], [9], [10]. However, when asphalt materials are used as thin overlays, they often have shortcomings such as insufficient interfacial cohesion and low strength, and it will often cause damage such as slippage and delamination, which will affect the service life of the bridge deck [11], [12]. Based on long-term practical applications in many countries, polymer pavement materials are used as overlays, and thin polymer overlay (TPO) technology is gradually formed [13]. The TPO system is currently used by>2400 Bridges, Compared with the traditional asphalt concrete pavement, the application of TPO into bridge deck pavement has obvious advantages. First of all, it has a thin thickness and a light weight making it possible to effectively reduce the static load of the bridge body. Second, it has good bonding performance with the lower bearing layer and can provide excellent anti-skid performance and high strength.

As mentioned in the literature review, epoxy resin binder and basalt aggregate have been used as traditional TPO materials [14]. However, ordinary epoxy resin has high brittleness, poor toughness and poor bonding performance and cannot be directly used as interface bonding material. In addition, the old pavement is an open environment and has cracks and other diseases. Another problem is that diseases such as aggregate delamination, voids and even delamination often occur after using epoxy resin-basalt TPO pavement, which greatly hinders the development of this technology in bridge deck pavement. Therefore, the bonding material between the aggregate and the old pavement must have good permeability, adhesion and weather resistance, and the bonding material and aggregate used in TPO pavement must be modified to meet the maintenance and bearing capacity requirements.

In this study, a new TPO material firstly was prepared using an economically common polyurethane binder and emery aggregate and introduced to the mechanical performance test. Until recently, there has been few reports on polyurethane-emery TPO pavement materials, and furthermore, systematic investigation of the adhesion mechanism and mechanical performance was not performed before. Polyurethane composite materials have many advantages and good engineering application prospects. Numerous experimental studies and engineering examples have proven that polyurethane composite materials can improve the load-bearing capacity of the structure. This material has strong bonding properties, without any peeling failure of structures strengthened by traditional materials. Moreover, polyurethane-cement (PUC) composite materials have high strength, as demonstrated by their capability to limit cracks [15], [16]. Polyurethane is widely used at present. Polyurethane is a kind of synthetic material with excellent properties such as wear resistance, temperature resistance, and good comprehensive mechanical strength. Many scholars have carried out a series of studies on its excellent performance in civil engineering materials. Especially, two-component polyurethane binder material has strong bonding properties, without any peeling failure of structures strengthened by traditional materials. In other words, Cement represents the most widely used structural material because of its excellent permeability, frost resistance, dry shrinkage resistance, and compressive strength characteristic. Moreover, polyurethane-cement (PUC) composite materials have high strength, as demonstrated by their capability to limit cracks. With the addition of polyurethane in cement, the tensile strength is seen to improve substantially. PUC has a large tensile deformation capacity and good bonding with the bridge deck. PUC is a new kind of material with excellent mechanical properties of high tensile strength, large ultimate deformation, high modulus of elasticity, and excellent bonding performance. Thus, PUC has great advantages in bridge deck pavement materials, and research is needed to fully understand the behavior of polyurethane-emery TPO structures reinforced with cement materials.

The hydroxyl groups on the surface of SiC particles and the NCO in the polyurethane macromolecules, the main component of emery, participate in in-situ polymerization to form a certain amount of chemical bonds and hydrogen bonds, which is conducive to the crystallization of macromolecules to achieve enhancement [17], [18]. When the emery content is too high, it may destroy the orderly arrangement of the hard segments in some macromolecules and affect the crystallization, thereby reducing the mechanical properties of the polyurethane-emery composites.

On the other hand, the effectiveness of steel fiber and cement-reinforced polymer as reinforcement in TPO structures has not been demonstrated. The basic purpose of TPO design is to reduce the dead load of the entire structure including the bridge, improve the mechanical performance, and provide a safe driving environment as the TPO surface has relatively high anti-skid and wear-resistant performance. However, traditional TPO has a disadvantage in that traffic is delayed due to high brittleness, poor toughness, and poor binder performance of the base material, and low anti-skid, wear-resistant, and aging performance. Therefore, there is a need for a method to improve the wear-resistant, anti-skid, and aging-resistance performance of this material in the future. As such a method, reinforcing materials such as steel fiber and cement, which have a good reinforcing effect and good toughness and ductility, are added to the primary material to improve not only the mechanical performance of TPO but also other road performance. Thus, research is needed to fully understand the behavior of TPO structures reinforced with steel fiber and cement materials. Compared with conventional steel reinforcement, steel fiber polymer has higher flexural and compressive strength and greater corrosion resistance [19], [20]. Steel fiber and cement have been extensively implemented as one-dimensional reinforcement in concrete structures, such as bridge girders and decks.

The mechanical properties of both plain polyurethane-emery TPO and steel fiber and cement reinforced the polyurethane-emery TPO mixtures, proportioned using commercially available materials, were investigated in this study. In addition, polyurethane and cement were used to increase reactivity.

This research includes the development of reliable analysis tools capable of predicting displacement modes and load capacities of steel fiber and cement-reinforced polyurethane-emery TPO structures in which there are significant flexural characteristics based on ABAQUS software. The geometrical shape, modulus of elasticity, and force transfer characteristics of polyurethane-emery TPO with reinforced steel fiber and cement materials are different from those of conventional TPO structures. Parametric studies were carried out by using the numerical model to investigate the effect of reinforced configuration on an ultimate load of reinforced polyurethane-emery TPO structures. A three-dimensional FEM simulation in ABAQUS has been used to model the failure process of the experimentally tested compression specimens and the flexural prisms.

The results show that the error between the experimental value and the numerical value is small proving that the research results of this paper can promote the development of new thin polymer overlay.

Section snippets

Reinforcement materials – steel fiber and cement

Two types of steel fibers are used in this study, that is, straight steel fibers having circular cross-sections with a diameter of 0.3 mm and lengths of 6 and 13 mm. Steel fibers with 0.3 mm in diameter and 6 mm in length had a unit weight of 6.5 g/cm3 and Steel fibers with 0.3 mm in diameter and 13 mm in length had a unit of 6.53 g/cm3. Young’s modulus and Poisson's ratio were 200GPa and 0.2, respectively. Steel fibers with 0.3 mm in diameter and 6 mm in length were used with a dosage of 0.5 %

Flexural and compressive strength

In the test for determining the optimal mixing ratio of two-component polyurethane and the emery—TypeⅠtest, the flexural and compressive strength results of the test are listed in Table 2. Fig. 3, Fig. 4 show the effect of the two-component polyurethane mix ratio and polyurethane-to-emery mix ratio on the properties of the polyurethane-emery TPO material specimens, respectively.

When the polyurethane-to-emery mixing ratio is 1:5, the flexural and compressive strengths are the highest among the

Numerical simulations

This section presents the numerical study of new-TPO behavior and failure. FEM simulation is used to model the failure process of the experimentally tested flexural prisms. The commercial software ABAQUS is commonly utilized in research, and the second development model of steel fiber and CDP model based on python in this software can predict the behavior of the steel fiber and new-TPO with reasonable accuracy. Then, the mechanical behavior obtained through the experiment is transferred to the

Conclusions

In this study, the basic behaviors of the polyurethane- emery TPO (new-TPO) considered with different reinforcement configurations were determined by flexural and compression tests. Through flexural and compression tests, this study mainly investigated change laws of flexural and compressive performance of polyurethane-emery TPO at different reinforcement configurations and analyzed failure load, displacement, maximum principle stress, damage, and displacement distribution before and after

Funding

This work was supported by the Jilin Transportation Innovation Development Support (Science and Technology) Project [Grant No 2020–1-9].

CRediT authorship contribution statement

Chol Rim: Investigation, Conceptualization, Data curation, Methodology, Software, Visualization, Writing – original draft. Quansheng Sun: Resources, Project administration, Funding acquisition. Changsop Kim: Formal analysis, Validation, Writing – review & editing.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors gratefully appreciate Jilin Transportation Innovation Development Support (Science and Technology) Project (2020-1-9) and the support from the Province Key Laboratory of Road in Northeast Forestry University.

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