No abstract

The mix proportion design methods for full-depth reclamation mixtures using foamed bitumen normally fix a constant active filler content, and an indirect tensile strength (ITS) test is used to determine the optimum bitumen content. However, it has been reported in the literature that for some materials the ITS test is not sufficiently sensitive to bitumen content. This lack of sensitivity is a problem for the practitioner engineer who has to validate the bitumen content adopted in the mixture design. The main objective of this work is to examine the sensitivity to bitumen content of additional laboratory tests that could complement current design methods based on ITS. The mixtures used in the study were prepared by using three recycled blends of reclaimed asphalt pavement and aggregate that were mixed with bitumen foam contents of 1.25%, 2.5%, and 3.75%. Test results confirmed the low sensitivity of the ITS test, and it was found that the indirect tensile fatigue (ITF) test was the most sensitive among all tests. To explain the higher sensitivity of the ITF test compared with the ITS test, a stress–strain diagram and a simple unidirectional mechanical model were developed. In addition, an S-N fatigue diagram was used to illustrate that at a larger number of load cycles, the effect of the foamed bitumen content is clear, as shown in the experimental work. Overall, the laboratory program and material behavior analysis indicate that when the ITS test does not provide conclusive results, the laboratory program should be complemented with ITF tests to determine the optimum foamed bitumen content with more reliability.

Leachate reuse is a helpful tool that contributes to the sustainability of agricultural systems, but it requires previous disinfection. Hydrogen peroxide can be found among the disinfectants frequently applied in ecological production systems. Moreover, it can improve the oxygenation of the root system. The objective of this work was to study its effect on C. fruticosa plants fertigated with leachates. A split-plot design with six treatments, three without an H2O2 supply (S0) and three with an H2O2 supply dosage at 2% (SH2O2), was arranged: raw leachate from C. lanatus (L100), raw leachate from C. lanatus diluted with tap water until EC of 2.5 dS m−1 (LWD), and raw leachate from C. lanatus diluted with standard nutrient solution until EC of 2.5 dS m−1 (LNSD). The results produced data about the evolution of the nutrient and leachate solutions throughout the cultivation period. Morphological (height, leaf number, leaf area, total fresh weight, relative water status, and dry weight) and physiological (chlorophyll a, chlorophyll b, carotenoids, chlorophyll a+b, and proline) parameters were studied to reveal the plant response. The efficiency of nutrient utilization was higher with the LWD treatment, and water and nitrogen utilization efficiency decreased under the H2O2 supply. In conclusion, the reuse of diluted leachate is advised for nutritionally undemanding crops, such as C. fruticosa; moreover, the H2O2 supply improved tolerance to salinity and enhanced root growth and Red-Green-Blue (RGB) values.

Hygroscopy is the main stabilization mechanism that explains the good performance of magnesium chloride hexahydrate (6H2O•MgCl2 or simply MgCl) roads, as it absorbs and retains relative humidity (RH), reducing erosion and increasing durability. However, road users have observed that the skid resistance of MgCl roads decreases with increased RH. To study the skid resistance of MgCl roads, the study calculated the drag factor or friction coefficient of the road surface with a braking test, in which an accelerometer was installed in a vehicle and deceleration was recorded during braking. The braking test was used to calculate the effect of RH and surface condition on skid resistance in 30 road sections located in the northern region of Chile. The testing was designed with a factorial experiment that took the following into consideration: surface condition (well-graded, sealed, and loose aggregate), whether water was artificially added to the surface (normal or wet), and a wide range of RH (between 10% and 70%). The results showed that when RH was greater than 35% to 40%, the friction of MgCl roads decreased as RH increased. In environments in which the air humidity was lower than 60%, the friction coefficient was higher than 0.55, a value that provides suitable friction conditions for most geometric designs for low-volume roads. The study showed that a braking test is a simple and consistent tool for assessing braking performance on MgCl roads. In addition, the study concluded that special attention should be given to surface characteristics and geometric design where MgCl road sections are exposed to RH greater than 60%.