Flexural fatigue strength of demolition aggregates stabilized with alkali-activated calcium carbide residue

Replacing the base and subbase layers in flexible pavements and sub-ballast layer in railway tracks with recycled materials has attracted significant attention from industry and researchers alike. The semi-rigid stabilized layers in the flexible pavement structure and railway tracks sustain high flexural and tension stresses which reduces the serviceability life of the superstructure. The flexural and compressional modulus of the stabilized materials under repeated loads and at at-rest k 0 condition is highly dependent on the specifications of the binder. Industrial by-products including calcium carbide residue (CCR), Fly Ash (FA) and Slag (S) were utilized to improve the compressional resilient modulus, flexural strength, durability and fatigue life of recycled aggregates. The variation of ductility in the blend with different precursors indicated that the service life of the stabilized layers not only depended on the strength but was also controlled by the deterioration rate of the flexural modulus and stiffness of the sample. The ductility of binder with aluminosilicate gels fabric can potentially absorb the stresses of the cyclic loading and postpones development of tension cracks

Evaluation of Strength and Resilient Modulus Characteristics of Fly Ash Geopolymer Stabilized Reclaimed Asphalt Pavement Material

Utilization of sustainable road construction materials has been the focus of research worldwide in recent times. Virgin aggregate is a primary material in the pavement industry; hence, finding an alternative is of extreme importance, concerned with the more prudent use of natural resources and the protection of the environment. The present research explored the usage of a significant portion of reclaimed asphalt pavement (RAP), activated with low calcium fly ash (FA) as a binding material. A liquid alkaline activator comprising sodium silicate solution (Na2SiO3) and sodium hydroxide (NaOH) was used for the alkali activation of the mix. The fundamental design parameters including Unconfined Compressive Strength (UCS) and resilient modulus (Mr) characteristics of the stabilized RAP:VA+FA geopolymer specimens were studied at room temperature. The resilient modulus (Mr) value in mechanistic-empirical analyses has been widely accepted in design/analysis of the pavement structures. Therefore, the present study aims to examine the resilient behaviour of the pavement base material stabilized with alkali activated low calcium Indian fly ashes, obtained from the southern region of India. The effect of additives on the microstructure of RAP:VA+FA blends were verified for one day and 28 days cured samples using X-ray diffraction (XRD) studies. Since the UCS and Mr values met the specified strength requirements, the stabilized mix can be used as a pavement base material