The Effect of Reclaimed Asphalt Pavement (RAP) Aggregates on the Reaction, Mechanical Properties and Microstructure of Alkali-Activated Slag

CivilEng

Augusto Cesar S. Bezerra¹  Paulo H. R. Borges¹  Juliana O. Costa¹  Flávio A. dos Santos¹  Johan Blom²  Wim Van den bergh² 

[1] Department of Civil Engineering, Federal Center for Technological Education of Minas Gerais (CEFET-MG), Belo Horizonte 30510-000, Brazil;EMIB Research Group, Faculty of Applied Engineering, University of Antwerp, 2020 Antwerp, Belgium;

关键词: RAP;    alkali-activated materials;    recycled aggregates;    calorimetry;    microstructure;   

DOI  :  10.3390/civileng2030043

来源: DOAJ

【 摘 要 】

Reclaimed asphalt pavement (RAP) is a recyclable aggregate produced during the demolition of old flexible pavements and consists of natural aggregates (NA) coated with aged bitumen. The detrimental effect caused by the bitumen coating on strength and porosity has limited the use of RAP on traditional cementitious systems. This study investigates the potential use of fine RAP to substitute NA in the production of alkali-activated slag mortars (AAM). The effect of different activator dosages was assessed, i.e., either 4% or 6% Na₂O (wt. slag) combined with a modulus of silica equal to 0, 0.5 and 1.0. The characterisation of 100% RAP-AAM consisted of hydration kinetics (Isothermal Calorimetry), pore size distribution (Mercury Intrusion Porosimetry), mechanical performance (Compressive and Flexural strength), and microstructure analysis (Scanning Electron Microscopy and Confocal Laser Scanning Microscopy). The results show that RAP aggregates do not compromise the reaction of the matrices; however, it causes a significant strength loss (compressive strength of RAP-mortars 54% lower than reference NA-mortar at 28 days). The higher porosity at the interface transition zone of RAP-AAM is the main responsible for the lower strength performance. Increasing silicate dosages improves alkaline activation, but it has little impact on the adhesion between aggregate and bitumen. Despite the poorer mechanical performance, 100% RAP-AAM still yields enough strength to promote this recycled material in engineering applications.

【 授权许可】

Unknown