Mechanism of Polyurethane Binder Curing Reaction and Evaluation of Polyurethane Mixture Properties

Abstract

This study focuses on analyzing the curing reaction mechanism of polyurethane (PU) binders and comprehensively evaluating the PU mixture’s properties. The former was investigated by conducting a Fourier transform infrared spectroscopy (FTIR) test on PU binders with different curing times. The volume change characteristics, construction operation time, and strength formation law were clarified through the splitting tensile test of PU mixtures under different environmental conditions. The optimal PU mixture stacking time and curing time under different environmental conditions were determined. The properties of the PU mixture and asphalt mixture were evaluated and compared through a rutting test, low-temperature bending test, freeze–thaw splitting test, and four-point bending fatigue test. The results show that the physical and chemical curing of the PU binder occurred within the first 24 h of curing, and the reaction speed gradually accelerated to form a polyurea structure 24 h later. It is recommended to stack the PU mixture for 4 h before compaction and to cure it for 2 days before opening under the conditions of 50% humidity and 15–40 °C surrounding temperature. The PU mixture shows better temperature stability and fatigue resistance than the asphalt mixture, and the splitting tensile strength of the PU mixture before and after the freeze–thaw splitting test is also higher. It is clear that the PU mixture is a green road building material with good performance.

Mechanical Properties of Polyurethane Mixture and Load Response Behaviour of Polyurethane Composite Pavement

“…The reason for this is that asphalt is a temperature-sensitive binder. Increases in the temperature lead to a transition of asphalt from an elastic state to a viscous state, which affects its mechanical properties [ 16 ]. The strength of the PU mixture is formed by the curing reaction of the PU binder, which is irreversible.…”

“…Secondly, according to the ultimate bearing capacity and stress level, the control stresses of the five mixtures are calculated. Previous studies have shown that the fatigue life of PU mixtures is long [ 16 , 17 ], so the stress levels of asphalt mixtures are 0.3, 0.4, and 0.5, and the stress levels of PU mixtures are 0.5, 0.6, and 0.7.…”

“…Therefore, the 4 cm SMA-13 mixture is used as the upper layer of the pavement, and this study focuses on the structural design of the middle and lower layers. Previous studies have shown that PU mixtures have significant elastic properties, and their dynamic modulus is obviously larger [ 16 , 17 ]. Therefore, the thickness of the PU mixture layers is appropriately reduced in the design of the pavement structure.…”

“…Compared to traditional mixtures, PU mixtures have better durability, temperature stability, waterproof properties, and crack resistance, which can reduce maintenance frequency [ 11 , 12 , 13 , 14 , 15 ]. However, as a new type of road construction material, the conventional pavement structure design method is not applicable [ 16 , 17 , 18 , 19 , 20 ]. Therefore, it is necessary to study the mechanical properties of PU mixtures and their composite pavement load response behaviour, providing a basis for the structural design of PU mixture pavement.…”

Fatigue Properties and Damage Characteristics of Polyurethane Mixtures under a Stress Control Mode

“…At present, PU mixture is mainly studied in three aspects: functional pavement, pavement structural layer, and bridge deck pavement. The composition design, curing reaction mechanism, performance evaluation, and construction technology of PUM are being studied by an increasing number of researchers worldwide [16][17][18].…”