This paper introduces the new RILEM Technical Committee on Alternative Paving Materials – Design and Performance (TC APD), which builds upon the foundational efforts of the former TC 279-WMR focused on the Valorisation of Waste and Secondary Materials for Roads. The TC APD aims to advance the understanding of alternative paving materials, emphasizing their design and performance as essential components of road composites. The committee addresses three areas of investigation, each dedicated to examining the current technological state of the art, the design process and the field performance of composites incorporating alternative paving materials. The manuscript provides a comprehensive overview of the TC's background, outlines the research objectives and activities proposed, and discusses the committee's position within RILEM and the broader research community. Additionally, it details the anticipated outcomes and the potential impact of the committee's work on advancing the field of sustainable road construction.

Glass transition parameters can be used to study the miscibility, or lack of it, in polymer-modified asphalt binders. In this study, the contribution of thermodynamics of mixing to glass transition was quantitatively assessed in a differential scanning calorimeter for four asphalt binders partially and fully replaced by an epoxy system. The values of heat capacity (C_p) and, subsequently the glass transition temperature (T_g) of all binders were determined to quantify the miscibility based on the entropic changes. Emphasis was also given to examining the enthalpy of mixing as a function of epoxy system composition during curing to ensure that these binders were completely crosslinked for further analyses. In all cases, the positive deviations of the measured T_g of epoxy-modified asphalt binders (T_g,mix) obtained from the ideal mixing rule led to negative values of the entropy of mixing (ΔS_mix^c), dictating the presence of internal repulsive forces between the asphalt and epoxy components. Softer binders were associated with binders of low deviations of T_g,mix values from the ideal mixing rule. Lastly, the partial replacement of asphalt binders by the epoxy system increased the T_g and decreased the amount of ΔS_mix^c, and such performance imposes the formation of immiscible products.

The RILEM TC 272 PIM (Phase and Interphase behaviour of innovative bituminous Materials) – TG1 Binder has initiated an inter-laboratory program investigating the phase and interphase behaviour of bituminous binders. Five laboratories evaluated the low temperature properties of seven standard and complex binders with differential scanning calorimetry (DSC). DSC has been accepted as a powerful tool to evaluate, among others, the glass transitions, Tg, monitoring the endothermic or exothermic heat flow of a material under controlled temperature conditions. There are different ways to run the test, conventional temperature linear-DSC (TL-DSC), and temperature modulation-DSC (TM-DSC). The latter has been proven as an efficient method differentiating the structural relaxation phenomena from the heat capacity. In this study, emphasis was laid on comparing the Tg measured by TL- and TM-DSC improving the interpretation of binder glass transitions. To restrain the scope of this study, two SBS polymer modified binders (PmBs), a commercially available PmB and an highly modified PmB (7.5 % SBS) , were evaluated and compared with two neat bituminous binders. It was observed that the modification by 7.5% SBS resulted in a decrease of the Tg. This reduction of Tg reflects the positive influence of SBS at low temperatures.

The glass transition parameters are used to study the miscibility, or lack of it, in polymer modified asphalt binders. In this study, a quantitative assessment of the contribution of thermodynamics of mixing to glass transition was conducted in a differential scanning calorimetry for four asphalt binders modified with an elastomeric epoxy system. Especially, the values of heat capacity (Cp) and subsequently the glass transition temperature (Tg) of all binders were determined to quantify the miscibility based on the entropic changes. Emphasis was also given on examining the enthalpy of mixing as a function of the composition of epoxy asphalt binders during curing to ensure that these binders were completely crosslinked for further analyses. In all cases, the positive deviations of Tg,mix obtained from the ideal mixing rule, or 𝛥𝑇𝑔,𝑚𝑖𝑥, led to negative values of the entropy of mixing (𝛥𝑆𝑚𝑖𝑥𝑐), dictating the presence of internal repulsive forces between the asphalt and epoxy components. The soft in properties and sol type base binders are also associated with epoxy asphalt binders of low 𝛥𝑇𝑔,𝑚𝑖𝑥 values. Overall, the incorporation of the epoxy system in asphalt binders increases the Tg and decreases the amount of 𝛥𝑆𝑚𝑖𝑥𝑐, and such performance imposes the formation of phase-separated binders.

InfraRed spectrometry is a powerful technique to characterise bituminous binders. The methodology is not fully harmonised and may lead to vari-ability. The RILEM-272-PIM-TG1, evaluated seven complex bituminous, for which eleven laboratories performed FTIR. While, the spectra showed sim-ilar trends, further analysis was needed to improve comparison. A specific approach was applied on two binders, unmodified and polymer modified bitumen, and two ageing conditioning. Combining a Gaussian distribution
and derivative analysis confirmed a good alignments of laboratory results. A two-step model was developed improving further interpretation. It con-sists of a baseline adjustment with eight points and normalisation over the maximum aliphatic peak. Furthermore, a specific fingerprint model was determined with the main absorption peaks defined by their location and shape. Only the intensity varies from laboratory to laboratory and binders. This general approach can be used as a platform to characterise aging or binder complexity

The RILEM TC 272 PIM (Phase and Interphase behavior of innovative bituminous Materials)—TG1 Binder has initiated an inter-laboratory program investigating the phase and interphase behaviour of bituminous binders. Within the scope, four laboratories evaluated the low temperature properties of seven binders with differential scanning calorimetry (DSC). DSC has been accepted as a powerful tool to evaluate, among others, the glass transitions, Tg, monitoring the endothermic or exothermic heat flow of a material under controlled temperature conditions. There are different ways to run the test, conventional temperature linear-DSC (TL-DSC), and temperature modulation-DSC (TM-DSC). The latter has been proven as an efficient method differentiating the structural relaxation phenomena from the heat capacity. In this study, emphasis was placed on comparing the Tg measured by TL- and TM-DSC to improve the interpretation of binder glass transitions. In this study, the scope was restrained to two Polymer modified Binders (PmBs): a commercially available modified binder named PmB1 and a highly modified binder (7.5 wt% high vinyl SBS) named PmB2, were evaluated and compared with two neat bituminous binders. Based on the thermographs of the PmB2 obtained through this inter-laboratory program, it was observed that the modification by 7.5% SBS resulted in a decrease of the Tg. This reduction of Tg reflects the positive influence of SBS at low temperatures.