Determination of compaction timing of porous polyurethane mixture by multiscale testing and analysis

Abstract

In this study, different methods including laboratory test, micro test and statistical analysis were employed to investigate the strength evolution mechanism of porous polyurethane mixture (PPM) and determine its reasonable compaction timing. Firstly, a series of laboratory tests including void analysis, indirect tensile test, rutting test, bending test, and immersion Cantabro test were conducted on PPM compacted at different curing times to study the relationship between curing time and the performance of PPM. Then, orthogonal tests were carried out to quantify the impact of temperature, relative humidity, and catalyst dosage on the curing reaction of PPM, and a prediction model for curing time was proposed to determine its compaction timing. Finally, combined with the micro test results of thermal gravimetric analysis (TGA), four invalid test conditions and results in the orthogonal test were eliminated to optimize the prediction model. The test results show that voids in total mix (VTM) and indirect tensile strength (ITS) were suitable as control indicators to determine the earliest and latest compaction timing for PPM, specifically VTM ≤ 24.06 % and ITS ≥ 1.13 MPa. The prediction model of the earliest and latest compaction timing proposed by the orthogonal test was optimized by TGA results. The fitting accuracies of the prediction model had been significantly improved, and the coefficients of determination increased from 0.86 and 0.88 to 0.93 and 0.94, respectively.