Chemically modified bitumens with enhanced rheology and adhesion properties to siliceous aggregates

Abstract

Moisture damage is one of the major premature failures that worsens the performance and shortens service life of pavements. This research assesses the effect that two chemical modifiers (thiourea and an isocyanate-functionalized castor oil prepolymer) exerts on the bitumen rheology and on the resistance to potential moisture damage of asphalt mixtures based on siliceous aggregates. Both thiourea and the isocyanate-based prepolymer improve the viscous and viscoelastic behaviours of bitumen at high inservice temperatures, particularly the isocyanate-based reactive modifier. Likewise, the visual inspection of the degree of bitumen coating on loose mixtures exposed to water in a "rolling bottle" test, and further surface free energy measurements, showed that the bitumen modification by the isocyanate-based prepolymer seems to reduce moistureinduced damage on siliceous aggregates. Conversely, thiourea-based modification increases sensitivity of the bitumen-aggregate mixture to water. Different adhesion mechanisms, based on chemical or physical bonds with the aggregate surface, have been proposed for each modifier.

Waste materials in highway applications: An overview on generation and utilization implications on sustainability

“…The presence of moisture and compounds of high volatility is dependent on the waste material's source; this phenomenon is also a limitation in the replacement of asphalt with bio-oil-based binders. Also the adoption of non-standardized traditional techniques for appraisal, which may not properly represent the real-time resistance to moisture of these alternatives is serious challenge; as such, new and reliable methods, such as surface-free energy should be encouraged (Al-Sabaeei et al, 2020;Cuadri et al, 2015;Gedik, 2020).…”

Evaluating Fatigue Behavior of Asphalt Binders and Mixes Containing Date Seed Ash

“…In order to prepare the modified binders, three types of additives were added to bitumen at three different levels of 3%, 6% and 9%. The mixing procedure was prepared applying two steps as recommended by some researches (Cuadri et al 2015;Köfteci et al 2014). Firstly, the bitumen was heated to 160 °C and DSA as other additives was poured slowly into the mixing container.…”

Investigation on the use of a novel chemical bitumen additive with reclaimed asphalt and at lower mix production and construction temperatures: a case study

“…The working principle is that the isocyanate functional groups (-NCO) react with the nucleophilic groups within the bitumen, creating a new type of flexible network. State of the art on the use of isocyanates in bitumen has been well described in the literature and the versatility of this chemistry permit different ways of additions, reactive modifications and combination with different chemicals (Cuadri et al, 2013;Cuadri et al, 2015;Navarro et al, 2007). Bitumen modification with isocyanates has been already described.…”