Climate change and limited power supplies receive significant incentives to develop alternative paving materials and technologies. Reclaimed asphalt pavement (RAP) and Warm Mix Asphalt (WMA) are technologies that can provide significant benefits to both the environment and the economy. This study used response surface methodology (RSM) to analyze the rutting resistance and moisture susceptibility of asphalt mixtures containing different amounts of RAP and doses and types of WMA. The experimental design was established utilizing the RSM with a central composite design (CCD) for varying RAP dosages (25–50%), WMA amounts (1.5-4%), and WMA types (waxy organic Asphaltan type A ® , and waxy organic Asphaltan type B ® ). The moisture sensitivity and rutting resistance of asphalt samples were evaluated using the Modified Lottman method (AASHTO T 283) and wheel tracking test, respectively. RSM’s statistical and mathematical models were employed to estimate the optimal value for RAP dose and WMA content and type. The results demonstrated that adding RAP to WMA mixtures increased the rutting and moisture resistance of asphalt samples. Also, the analysis of variance (ANOVA) results indicated that the increase in the WMA content led to a significant decrease in the rutting resistance, while the rise in the RAP content contributed to a significant enhancement in the rutting performance of the samples. The statistical outcome also showed that the moisture susceptibility of the mixture decreased significantly after increasing the RAP content, while the increase in WMA content did not have a significant influence on the moisture performance of the mix regardless of the WMA type. The research indicated that rutting resistance and moisture susceptibility have significant correlation coefficients (R2) of > 0.92, indicating that the model is highly correlated with the experimental results. Multi-objective numerical optimization led to the optimal design with 50% RAP and 1.5% WMA-type A. Validation findings indicate strong agreement and model effectiveness, with an error variance of less than 5% for all responses.

Controlling the hydraulic heads along a coastal aquifer may help to effectively manage
saltwater intrusion, improve the conventional barrier’s countermeasure, and ensure the coastal
aquifer’s long-term viability. This study proposed a framework that utilizes a decision-making model
(DMM) by incorporating the results of two other models (physical and numerical) to determine proper
countermeasure components. The physical model is developed to analyze the behavior of saltwater
intrusion in unconfined coastal aquifers by conducting two experiments: one for the base case, and one
for the traditional vertical barrier. MODFLOW is used to create a numerical model for the same aquifer,
and experimental data are used to calibrate and validate it. Three countermeasure combinations,
including vertical barrier, surface, and subsurface recharges, are numerically investigated using
three model case categories. Category (a) model cases investigate the hydraulic head’s variation
along the aquifer to determine the best recharge location. Under categories (b) and (c), the effects
of surface and subsurface recharges are studied separately or in conjunction with a vertical barrier.
As a pre-set of the DMM, evaluation and classification ratios are created from the physical and
numerical models, respectively. The evaluation ratios are used to characterize the model case results,
while the classification ratios are used to classify each model case as best or worst. An analytical
hierarchy process (AHP) as a DMM is built using the hydraulic head, salt line, repulsion, wedge area,
and recharge as selection criteria to select the overall best model case. According to the results, the
optimum recharging location is in the length ratio (LR) from 0.45 to 0.55. Furthermore, the DMM
supports case3b (vertical barrier + surface recharge) as the best model case to use, with a support
percentage of 48%, implying that this case has a good numerical model classification with a maximum
repulsion ratio (Rr) of 29.4%, and an acceptable wedge area ratio (WAR) of 1.25. The proposed
framework could be used in various case studies under different conditions to assist decision-makers
in evaluating and controlling saltwater intrusion in coastal aquifers.