# Modeling of Fatigue-Strength Development
Incorporation of marginal aggregates, such as reclaimed asphalt pavement and demolition wastes, into cold-mix asphalts, will further reduce costs of disposal to landfills and the cost of sourcing bitumen and virgin aggregates [5; 6; 7; 8]. In spite of the numerous positive attributes of cold-mix asphalts, characterization of their engineering properties remains a chief hindrance to their acceptance as suitable alternatives to hot-mix asphalts [9]. Whereas hot-mix asphalts attain their ultimate engineering properties immediately after batching and compaction, foamed and emulsion bitumen asphalts require time for the foaming, or emulsification water, to evaporate before bitumen can coalesce and bind the aggregates. Due to the presence of water in their matrices, cold-mix asphalts behave more like improved granular materials in the early stages of their lives but eventually attain properties similar to those of hot-mix asphalts once all the foaming, or emulsification water, is lost through evaporation [10; 11]. The ultimate engineering properties of cold-mix asphalts are attained after months, or even years, of field curing. To characterize cold-mix asphalts using methods traditionally developed for hot-mix asphalts, agencies, and institutions have proposed accelerated laboratory curing protocols to simulate field curing and strength development in cold-mix asphalt. The literature is replete with laboratory curing protocols utilized, across the globe, to simulate field curing of cold-mix asphalt. Generally, curing temperatures ranging between 5 \({}^{\circ}\)C and 60 \({}^{\circ}\)C and curing durations ranging between 3 and 28 days are widely used [12]. Curing at 60 \({}^{\circ}\)C for 3 days, a protocol proposed by [PERSON] [13], and curing at 40 \({}^{\circ}\)C for 3 days, a protocol proposed by [PERSON] et al. [14], are the most popular of the laboratory curing protocols. Prediction discrepancies among laboratory curing protocols is a major impediment to the adequate characterization of cold-mix asphalt. Curing at 60 \({}^{\circ}\)C for 3 days, for instance, has been used to variously represent early life curing [15], curing during construction [16; 17], field cure of between 23 and 200 days [16; 18], and 1 year of field cure [19]. Similarly, curing at 40 \({}^{\circ}\)C for 3 days has been used to variously simulate 1 month of field cure [14] and 6 months of field cure [20; 21]. Besides these prediction discrepancies, the curing protocols in existence are region-specific and may, therefore, not allow for universal comparison of results on cold-mix asphalt behavior [9; 22; 23]. Furthermore, it has been noted that cold-mix asphalts cured at higher temperatures attain superior engineering qualities than those cured at lower temperatures [10; 24; 25]. These inconsistencies render the existing laboratory curing protocols quite unreliable in the prediction of field performance of cold-mix asphalt. Harmonization of laboratory curing protocols has been identified in the recent past as a priority research area for cold-mix asphalts [12; 23]. The numerous protocols need to be brought to concurrence through the adoption of characterization procedures that consider the combined effects of cure temperature and cure duration. Determination of cold-mix asphalt properties at the end of the curing period, as is done in most of the existing protocols, ignores the dependence of strength gain in cold-mix asphalts on both cure temperature and cure duration [10; 26]. The maturity method, a concept borrowed from concrete technology, has recently been used to study stiffness development in both emulsion and foamed asphalt mixtures [27; 28; 29]. Asphalt stiffness, resistance to rutting and resistance to fatigue cracking are key inputs in the mechanistic-empirical asphalt pavement design process [30; 31; 32; 33; 34]. Fatigue characterization of cold-mix asphalt mixtures is a subject of current research in the field of pavement materials.