Resistance to Moisture-Induced Damage of Half-Warm-Mix Asphalt Concrete with Foamed Bitumen

Abstract

Hot-mix asphalt (HMA) remains the predominant material for pavement surfacing. Mixing is performed at about 180 °C, depending on the bitumen used. Environmental concerns in terms of emissions and energy demand are fostering new sustainable technologies in road construction. Warm-mix asphalt (WMA) and half-warm-mix asphalt (HWMA) mixtures meet current expectations in that they are produced at lower temperatures, 100–130 °C, ensured by foaming the bitumen with water. The extent of temperature reduction requires that the mixture has adequate moisture and frost resistance, which is particularly important in countries that have a low-temperature climate. Asphalt concrete AC 8 S with 50/70-grade foamed bitumen modified with 0.6 wt.% surface-active agent (SAA) was used in the tests. To provide the AC mixture with the required resistance to climatic factors (water, temperature below 0), hydrated lime was added at 0, 15, 30, and 45 wt.% as limestone filler replacement. The influence of the hydrated lime addition on the air void content and resistance to moisture and frost damage was investigated according to the WT-2 2014 methodology based on EN 12697-12: 2008 and to the modified AASHTO T283 method. The optimum content of hydrated lime for filler replacement was determined through statistical analysis of the test results. With the optimum hydrated lime replacement of 30%, the required level of moisture and frost resistance of HWMA concrete with foamed bitumen is achieved. The results of this study confirmed the suitability of HWMA concrete with foamed bitumen for application in road construction practice.

Synergistic Effect of F–T Synthetic Wax and Surface-Active Agent Content on the Properties and Foaming Characteristics of Bitumen 50/70

“…Increasing the SAA amount reduces the softening point and hence the plasticity range. As a result, concrete durability at low winter and high summer temperatures may be reduced [ 34 , 35 , 37 ].…”

“…The continued search for other types of additives has aroused interest in surface-active agents (SAA), which, according to the results of the pilot study, have a very positive effect on the bitumen foam characteristics. Good foam parameters guarantee excellent coating of aggregates by the binder, which in turn provides the mixture with the required resistance to moisture and frost [ 34 ]. One limitation of this solution is that the standard and rheological properties of the binder may decrease [ 20 , 35 , 36 ], and the bituminous mixture will have lower mechanical parameters compared to the mixture that does not contain SAA [ 37 ].…”

“…The search for high values of foam parameters and high levels of standard and rheological properties at the same time should be continued to provide bituminous mixtures with proper durability and resistance to water, frost and rutting [ 34 , 41 ]. Additives such as F–T synthetic wax and SAA added to the bitumen before foaming appear to be the right solution; F–T synthetic wax improves the standard and rheological characteristics of the modified binder within a wide temperature range [ 42 , 43 ] and SAA will play a special role in terms of the mixture compaction temperature [ 36 ].…”

Effect of Hydrated Lime on Indirect Tensile Stiffness Modulus of Asphalt Concrete Produced in Half-Warm Mix Technology

“…The air void content in AC 8 S was determined in accordance with the methodology set forth in EN 12697-6:2008. Asphalt concrete AC 8 S should have 2.0% to 4.0% air voids [ 68 , 69 , 72 ]. Each test series consisted of nine trials, the number of which was determined in accordance with [ 70 , 71 ].…”

“…The basic frame-compositions of the mineral mixture and bituminous mixture are summarized in Table 4 and the particle size design of AC 8 S is plotted in Figure 2 [ 68 , 72 ].…”