1. Introduction
Although Chinese highway bridge construction has made great achievements, the damage problem of the expansion joint anchorage zone still becomes a key factor restricting the rapid development of highway bridge infrastructure construction. In the actual operation of the expansion joint, damage occurs due to the external effects of vehicles’ impact, sunlight, rainwater, vehicle impact, etc., resulting in an unsmooth connection between the road surface and the bridge deck, reducing driving comfort, and affecting traffic operations. And, due to the dramatic increase in traffic in recent years, this has accelerated degradation in the performance of bridge expansion joints [
1]. The role of expansion joints in the normal and safe operation of bridges cannot be overstated [
2]; however, due to the short life of expansion joints, frequent maintenance and repair are required. In addition, bridges are usually located in busy sections of traffic routes, and closing traffic for maintenance can incur huge costs. Therefore, a kind of expansion joint repair material with good crack resistance and impact resistance, simple construction, fast hardening, and early strength is needed.
The composite materials used in the anchorage zone of the expansion joint include polymer cement composite (PCC) and fiber-reinforced concrete [
3]. The advantages of organic and inorganic materials are combined, and the mix ratio can be adjusted as needed to obtain a higher-performance anchorage zone. In recent decades, scholars both abroad and domestic have conducted a lot of research on the materials of the anchorage area of expansion joints and made progress in various areas, from improving the use characteristics of materials in the anchorage zone of expansion joints to studying their service life and maintenance costs [
4,
5], from macroscopic mechanical properties to microstructural changes [
6,
7,
8], and from experimental research (interface compression–shear test [
7,
8,
9,
10], mechanical fatigue test [
11,
12], crack resistance test [
6]) to numerical simulation (stress distribution in the anchorage zone, fine simulation of wheel pressure load [
5,
13,
14]). In the study of anchorage zone materials, Li [
15] explored the utilization of polypropylene fiber and styrene–butadiene latex in combination with self-compacting concrete for expansion joints, examining their performance. Considering that the functional properties of PCC concrete depend on its microstructure and changes, Ohama [
16,
17] proposed the B-O-V model [
18] and divided the PCC microstructure into four stages [
19]. For interface compression–shear performance, Zhang Juan [
20] studied the shear fatigue resistance of the bonding layer of the cement concrete bridge deck using a 45° dynamic oblique shear test. Luo Yuming et al. [
21] conducted direct shear tests on Z-shaped bonded specimens to study the shear performance of the bonding interface between the reinforced concrete and the old concrete carbonation layer. Finally, in terms of numerical simulation, Li Wei [
22] established a finite element model of expansion joints to study the failure mechanism of expansion joints and the stress of anchorage zones of expansion joints.
The above research shows that domestic and foreign scholars have conducted a lot of research on expansion joints in terms of the causes of damage, anchorage zone materials, and stress characteristics. In terms of materials, antifatigue materials polyurethane elastic concrete, epoxy asphalt, and other materials are used in expansion joints, but these materials have the characteristics of chemical instability, ease of change, and high cost. Therefore, there is an urgent need to develop a good-performance and economical restoration material. In contrast, a fast-hardening PCC developed in this paper shows the characteristics of stable high- and low-temperature performance/long service life/short construction time, which meets the current needs. It uses sulfate aluminate cement and ordinary Portland cement as binders. With polymer powder as an admixture, the mix ratio of PCC fast-hardening material is determined by trial mixing. The semicircular bending test (SCB) test is carried out to study the effect of different fiber incorporation on the crack resistance of fast-hardening PCC material. Then, the interface shear performance of the fast-hardening PCC material and ordinary concrete is studied using a compression–shear test. Meanwhile, a finite element model is established to simulate the interface behavior between fast-hardening PCC material and ordinary concrete and compared with actual test results to verify its rationality. Ultimately, the finite element model of the expansion joint zone is established, and the mechanical response of the expansion joint anchorage zone after the application of the PCC is analyzed. Compared with other materials, the superiority of fast-hardening PCC material is verified.
5. Conclusions
● By comparing the compressive strength of basalt fiber BF, polyacrylonitrile fiber PAN, and propylene fiber PP at different ages, the fiber reinforcement effect of PCC fast-hardening material was studied. It was found that 1% volume content BF can greatly improve the compressive strength of the material.
● Considering the crack resistance of the material, the effects of different fiber types and content on the crack resistance of the material were compared using the SCB test. The crack of the fiber-free matrix specimen extended rapidly; the crack propagation of specimens mixed with BF or PAN fibers was slow, and the fibers were pulled out or broken.
● Considering the influence of fiber incorporation on the fracture energy Gf, fracture toughness KIC, and stiffness S of fast-hardening PCC materials in the SCB experiment, BF fiber contributes more significantly to the fracture energy Gf, fracture toughness KIC, and stiffness of materials than PAN fiber and PP fiber.
● Through the interface compression–shear test, it was concluded that the maximum compression–shear stress between fast-hardening PCC material and ordinary concrete can reach 5.61 MPa when the ratio of interface normal pressure to shear force is 1:1.
● The finite element model of expansion joint anchorage zone using fast-hardening PCC material was established. The stress characteristics of the expansion joint anchorage zone were explored, and the superior mechanical properties of the fast-hardening PCC material as expansion joint anchorage zone material were verified.
In summary, by determining the mix ratio of PCC material and the compressive strength under different fiber contents, the effect of different fibers on the crack resistance of the material and the interfacial bonding performance between the material and ordinary concrete was studied. It can be seen from the test and numerical analysis results, with a rational mixing ratio and fiber content, that PCC has favorable compressive and anti-cracking properties, and meanwhile, due to the short time of its strength formation, the application of PCC in the repair of bridge expansion joint anchorage areas can improve the service life of the expansion joints; reduce the construction period, so as to reduce the cost of maintenance; and minimize the impact of bridge repair on traffic. In addition, due to the excellent anti-cracking property of PCC material and its strong bonding property with ordinary concrete, PCC can also be applied to structural waterproofing or bridge deck defect repair in the future, which has high practical value and broad application prospects. The focus of future work may be to study the interaction between PCC materials and other materials, such as stretching (interfacial bonding properties between PCC materials and other cementitious materials) or drawing (bonding and anchoring properties between PCC materials and reinforcements). At the same time, it is also important to use more test data to reveal the deeper performance of PCC materials.