Cold in-place recycling asphalt mixtures: Laboratory performance and preliminary m-e design analysis

Cold in-place recycling (CIR) asphalt mixtures are an attractive eco-friendly method for rehabilitating asphalt pavement. However, the on-site CIR asphalt mixture generally has a high air void because of the moisture content during construction, and the moisture susceptibility is vital for estimating the road service life. Therefore, the main purpose of this research is to characterize the effect of moisture on the high-temperature and low-temperature performance of a CIR asphalt mixture to predict CIR pavement distress based on a mechanistic–empirical (M-E) pavement de-sign. Moisture conditioning was simulated by the moisture-induced stress tester (MIST). The moisture susceptibility performance of the CIR asphalt mixture (pre-mist and post-mist) was estimated by a dynamic modulus test and a disk-shaped compact tension (DCT) test. In addition, the standard solvent extraction test was used to obtain the reclaimed asphalt pavement (RAP) and CIR asphalt. Asphalt binder performance, including higher temperature and medium temperature performance, was evaluated by dynamic shear rheometer (DSR) equipment and low-temperature properties were estimated by the asphalt binder cracking device (ABCD). Then the predicted pavement distresses were estimated based on the pavement M-E design method. The experimental results revealed that (1) DCT and dynamic modulus tests are sensitive to moisture conditioning. The dynamic modulus decreased by 13% to 43% at various temperatures and frequencies, and the low-temperature cracking energy decreased by 20%. (2) RAP asphalt incorporated with asphalt emulsion decreased the high-temperature rutting resistance but improved the low-temperature anti-cracking and the fatigue life. The M-E design results showed that the RAP incorporated with asphalt emulsion reduced the international roughness index (IRI) and AC bottom-up fatigue pre-dictions, while increasing the total rutting and AC rutting predictions. The moisture damage in the CIR pavement layer also did not significantly affect the predicted distress with low traffic volume. In summary, the implementation of CIR technology in the project improved low-temperature cracking and fatigue performance in the asphalt pavement. Meanwhile, the moisture damage of the CIR asphalt mixture accelerated high-temperature rutting and low-temperature cracking, but it may be acceptable when used for low-volume roads

A case study of the comparison between rubberized and polymer modified asphalt on heavy traffic pavement in wet and freeze environment

Ground tire rubber (GTR) usage in asphalt pavement with the dry process has gained more prominence in recent times. The objective of this work is to investigate the pavement performance of GTR-modified asphalt pavement and polymer-modified asphalt pavement on heavy volume of traffic conditions in Michigan\u27s wet and freeze environment. A suite of laboratory tests was done to evaluate the pavement performance of GTR-modified and polymer-modified asphalt mixtures. To reveal the strain and stress relationship under different frequencies and temperatures, the dynamic modulus test was applied. The Hamburg wheel tracking device (HWTD) was used to assess the high-temperature deformation resistance. The disc-shaped compact tension (DCT) test was used to evaluate the low-temperature cracking characteristics. The characteristics of the asphalt binder were assessed by the dynamic shear rheometer (DSR) for high-temperature properties and the asphalt binder cracking device (ABCD) for low-temperature properties. After the construction, a field noise test was conducted. The experimental results stated that the polymer-modified asphalt mixture and GTR-modified asphalt mixture showed higher dynamic modulus and better ability to prevent cracking than the conventional asphalt mixture at low temperatures, as well as better permanent deformation and stripping resistance than the conventional asphalt mixture. The fracture energy of the GTR-modified hot mix asphalt (HMA) is 13–16 % larger than the polymer-modified HMA. The number of passes to the stripping point of GTR-modified was 510–518 % higher than the conventional HMA. When compared to the field core, the lab-compacted HMA offers superior pavement performance. The extracted asphalt binder test results show the GTR-modified asphalt has better rutting resistance and cracking resistance than polymer-modified asphalt, and the results in the noise test demonstrated that the rubber-modified asphalt pavement mitigated the noise level by 2–3 dB on the road at different vehicle speeds. Moreover, the pavement condition was noticeably enhanced after the reconstruction of the surface course. The total number of passenger tires to be used in this project is about 2270. To summarize, better rutting and cracking properties in asphalt pavement are shown by the project\u27s utilization of rubber technology. And the GTR-modified HMA is comparable to polymer-modified HMA. Therefore, it may be appropriate to utilize rubber technology on high-traffic volume asphalt pavement in Michigan\u27s wet and freeze climate

Abstract 15295: Molecular Mechanism of Chronic Sildenafil-Caused Regression of Heart Failure: Effects on the Express of Cardiac SR Ca2+-ATPase, Subtype of β-Adrenergic Receptors and Nitric Oxide Synthase Isoforms

Background: Sildenafil (SIL), a selective inhibitor of PDE5 has been shown to exert profound beneficial effects in heart failure (HF). Recently we further found that SIL caused regression of cardiac dysfunction in a rat model with isoproterenol (ISO)-induced progressive HF. However, the molecular basis is unclear. We hypothesized that reversal of HF-induced detrimental alterations on the expressions of cardiac SR Ca 2+ -ATPase (SERCA2a), β-adrenergic receptors (AR) and nitric oxide synthase (NOS) isoforms by SIL may play a key role for its salutary role in HF. Methods: Left ventricular (LV) and myocyte function and the protein levels of myocyte β 1 - and β 3 - AR, SERCA2a, phospholamban (PLB) and three NOS were simultaneously evaluated in 3 groups of male rats (6/group): HF , 3 months (M) after receiving ISO (170 mg/kg sq for 2 days); HF/SIL , 2 M after receiving ISO, SIL (70 μg/kg/day sq via mini pump) was initiated and given for 1 M; and Controls (C). Results: Compared with controls, ISO-treated rats progressed to severe HF at 3 M after ISO followed by significantly decreased LV contractility (E ES , HF: 0.7 vs C: 1.2 mmHg/μl) and slowed LV relaxation, reductions in the peak velocity of myocyte shortening (77 vs 136 μm/sec), relengthening (62 vs 104 μm/sec) and [Ca 2+ ] iT (0.15 vs 0.24) accompanied by a diminished myocyte inotropic response to β-AR agonist, ISO (10 -8 M). These abnormalities were associated with concomitant significant decreases in myocyte protein levels of β 1 -AR (0.23 vs 0.64), SERCA2a (0.46 vs 0.80), PLB Ser16 /PLB ratio (0.24 vs 0.40) and eNOS (0.28 vs 0.46), but significantly increases in protein levels of β 3 -AR (0.29 vs 0.10) and iNOS (0.18 vs 0.08) with relatively unchanged nNOS. Chronic SIL prevented the HF-induced decreases in LV and myocyte contraction, relaxation, peak [Ca 2+ ] iT , and restored normal myocyte contractile response to ISO stimulation. With SIL, protein levels of myocyte β 1 - and β 3 -AR, SERCA2a were restored close to control values, but eNOS was significantly elevated than controls (0.77). Conclusions: Chronic SIL prevents HF-caused downregulation of cardiac β 1 -AR and reverse contrast changes between iNOS and β 3 -AR with SERCA 2a and eNOS expression, leading to the preservation of LV and myocyte function, [Ca 2+ ] iT , and β-adrenergic reserve. </jats:p

Discrete element analysis of friction performance for tire-road interaction

Purpose This study aims to investigate the influence of surface texture distribution in respect to the procedure of pavement surface wear on friction performance. Design/methodology/approach The Weierstrass–Mandelbrot (W-M) equation is used to appropriate pavement surface profile. Through this approximation, artificial rough profiles by combining fractal parameters and conventional statistical parameters for different macro-texture are created to simulate the procedure of pavement surface wear. Those artificial profiles are then imported into discrete element model to calculate the interaction forces and friction coefficient between rolling tire and road. Furthermore, wavelet theory is used to decompose the profiles into different scales and explore the correlation between the profiles of each scale and pavement friction. Findings The influence of tire vertical displacement (TVD) on friction coefficient is greater than fractal dimension of road surface texture. When TVD decreases, the profiles can provide higher friction, but the rolling stability of tire is poor. The optimal fractal dimension of road surface is about 1.5 when considering friction performance. The pavement friction performance improves with wavelength from 0.4 to 6.4mm and decreases with wavelength from 12.8 to 51.2mm. Originality/value Artificial fractal curves are generated and analyzed by combining W-M function with traditional parameter, which can also be used to analyze the influence of texture distribution on other pavement performance. The preliminary research provides a potential approach for the evaluation of pavement friction performance. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2019-0499/ </jats:sec

Relationship between Air Voids and Permeability: Effect on Water Scouring Resistance in HMA

This study explored the relationship between air voids and permeability, and investigated the correlation between air void type, coefficient of permeability, mechanical properties, and moisture damage in hot-mix asphalt (HMA). Six asphalt mixtures were prepared with air voids ranging from 4% to 19% in increments of 3%. Major tests, including two air void tests, a penetration test, and a dynamic water scouring test, were conducted to assess the moisture damage by measuring and comparing the difference in air voids and permeability before and after the dynamic water scouring. A compressive test was conducted to evaluate the residual strength of HMA with different porosities. Results indicated that the effective voids and coefficient of permeability had a strong correlation. There was an obvious increase of effective voids and permeability for specimens with air voids from 10% to 13% after dynamic water scouring tests. In terms of compressive strength, specimens with air voids from 7% to 13% had greater strength loss and deformation than other specimens, indicating that moisture damage occurred and developed rapidly in asphalt mixtures within a certain porosity range