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Highlights • De-agglomeration of oxidized asphaltenes can be a measure of true rejuvenation. • Introduction of bio-rejuvenator increases colloidal stability of the aged asphalt binder. • Introduction of bio-rejuvenator decreases large molecule size of aged asphalt binder. • Adding 10% and 30% bio-Rejuvenator to the aged asphalt binder reduces its complex modulus by 34% and 76%, respectively. Abstract To promote sustainable engineering practices in construction, repeated use of reclaimed asphalt pavement (RAP) has been promoted. This in turn has led to the second and third generation of reclaimed materials containing severely aged asphalt binders. To facilitate recycling and reuse of these resources, there is a need to synthesize sustainable chemicals and modifiers, which can truly rejuvenate severely aged asphalt binder. This paper investigates mechanisms of true rejuvenation and introduces the ability to deagglomerate asphaltene nano-aggregates as a measure of true rejuvenation. Molecular dynamics simulations followed by rheometry and chemical characterization is used to evaluate the effect of a Bio-Rejuvenator (BR) made from bio-mass on asphalt binders aged for 60 h and 100 h in the laboratory as surrogates for highly aged asphalt binders found in the 2nd and 3rd generation of RAPs, respectively. Introduction of BR is found to be effective to disturb the nano-aggregates formed during oxidation due to the increased polarity of oxidized molecules. Some of the BR molecules are found to be more effective than others to interact with the oxidized asphaltene molecules and cause deagglomeration, whereas others play as dispersant agents to promote separation of nano-aggregates. Chemical characterization of the aged asphalt binder doped with BR shows that the colloidal stability of the systems increases and the large molecule size decreases when the BR is introduced to the aged asphalt binder. It is further observed that addition of 10% and 30% Bio-Rejuvenator to the aged asphalt binder reduces its complex modulus by 34% and 76%, respectively, bringing it closer to that of the neat binder. Overall, the study results show that the ability to de-agglomerate oxidized asphaltenes can be used as one of the measures of true rejuvenation. Such findings can help manufacturers develop effective rejuvenators to facilitate recycling and promote sustainability of construction practices. [ABSTRACT FROM AUTHOR]

Highlights • The effects of NaOH content on rheology and microstructure were studied. • The agglomerate structure of fresh pastes was investigated by G3 microscope. • HS Circularity and Elongation of solid particles were effected by NaOH content. Abstract This paper investigates the effect of NaOH activator content on the rheological properties of the fresh geopolymer pastes. Measurements on fluid, rheological properties (yield stress and plastic viscosity), microstructure (particle size distribution), geometrical property (HS Circularity and Elongation), and zeta potential of geopolymer fresh pastes were accomplished. Microstructure and geometrical property of geopolymer suspensions were observed by Morphologi G3 microscope. Results show that different NaOH activators content leads to notable changes on the microstructure and the rheological properties through significantly altering the charge characteristic of geopolymer surface. High NaOH activators content has low HS Circularity, high Elongation and zeta potential on the geopolymer suspensions. And as the main force between the particles, electrostatic repulsion plays an important role in the aggregation state of the particles in the early age. Higher zeta potential influences superior dispersion state of solid grains and stronger rheological properties of the geopolymer fresh pastes. [ABSTRACT FROM AUTHOR]

• Utilizing lime mud as a filler can lead to the production of high-strength materials. • Lime mud can enhance material hydration by creating more nucleation sites. • The use of lime mud can refine pores and decrease pore structure. • Lime mud can be used in large replacement ratios, which can improve the sustainability of the mixture. Lime mud (LM) is a solid industrial byproduct with high alkalinity and calcium carbonate (CaCO 3) content produced by the paper industry. LM has been used and investigated as a supplementary cementitious material (SCM). However, using LM with a high replacement ratio causes agglomeration, which reduces the material's strength and has a detrimental effect on other properties. In addition to agglomeration, LM is unreactive; thus, in this work, a high replacement ratio (70%) of sand with raw LM was investigated in a mortar mixture containing silica fume (SF), considering the fast SF hydration properties of cement in a high alkaline environment, and river sand is used to reduce the agglomeration of LM. The effects of the replacement were then evaluated using compressive strength, X-ray diffraction, thermogravimetric analysis, mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM). The hydration kinetics were investigated using isothermal calorimetry. The experimental results showed that combining SF with a high replacement ratio (70%) of LM improves compressive strength and flexural strength by 16% and 59.7%, respectively. This is due to the filler nature of LM, which refines the pore structure. Furthermore, the highly alkaline environment provided by LM increased the secondary hydration of SF with cement, which also improved the strength. [ABSTRACT FROM AUTHOR]

Large amounts of powders have been collected in quarries and the storage of these by-product dusts is a serious environmental concern. In this paper, the effects of limestone filler, diabase, and gneiss quarry powders on the properties of fresh cement pastes were investigated. The influence of the mineralogy and particle size distribution was evaluated by rheological methods on cement pastes containing the materials under investigation. In addition, in-situ particle size analysis of the fresh pastes was conducted to observe how these different by-product dusts affect agglomeration kinetics. Pastes containing quarry powders showed lower yield stress and lower viscosity than pastes containing only cement. The results show the benefit (in terms of paste rheology) of partial replacement of cement by diabase or gneiss powders, and the ability of these materials to be used as an alternative substitute to limestone filler as a mineral admixture. [ABSTRACT FROM AUTHOR]