Experimental and numerical study on improving mechanical properties of new polyurethane-emery thin polymer overlay (TPO) structure using three-point bending test
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.
References (29)
- et al.
Design and skid resistance evaluation of skeleton-dense epoxy asphalt mixture for steel bridge deck pavement
Constr. Build. Mater.
(2016) - et al.
Modelling of five-point bending beam test for asphalt surfacing system on orthotropic steel deck bridges
Int. J. Pavement Eng.
(2019) - et al.
Investigation of mechanical properties of thin epoxy polymer overlay materials upon orthotropic steel bridge decks
Constr. Build. Mater.
(2012) - et al.
Experimental study to investigate mechanical properties of new material polyurethane-cement composite (PUC)
Constr. Build. Mater.
(2014) - et al.
A novel approach to preparing carbon nanotube reinforced thermoplastic polymer composites
Carbon
(2005) - et al.
Effect of polymer admixtures to cement on the bond strength and electrical contact resistivity between steel fiber and cement
Cement. Concrete. Res.
(1996) - et al.
Experimental study on the interfacial bonding behaviors between sprayed UHTCC and concrete substrate
Constr. Build. Mater.
(2019) - et al.
Self-compacting concrete beams reinforced with steel fiber under flexural loads: A ductility index evaluation
Mater. Today. Proc.
(2021) - et al.
Flexural performance of highly reinforced composite beams with ultra-high performance fiber reinforced concrete layer
Eng. Struct.
(2020) - et al.
Ultra-high performance concrete overlays for concrete bridge decks, IOP Confer
Ser. Mater. Sci. Eng.
(2019)