Strength and durability studies on air cured alkali activated pavement quality concrete mixes incorporating recycled aggregates

There is a huge demand for managing the disposable desecrates generated as Construction and Demolition (C&D) wastes due to the increased growth of the construction sector in developing countries. The recycled aggregates utilized in this study were procured from one of such demolished building sites. The present investigation endeavours a detailed assessment of the performance of pavement quality Activated Concrete (PQAAC) mixes utilizing the recycled aggregates as a replacement to the conventional granite stone aggregates. The PQAAC specimens developed were subjected to air-curing and the strength-durability performances were studied and presented in this paper. Initially, PQAAC mixes are designed (adopting standard methods of mix design) to a strength grade of M-40 using Ground Granulated Blast Furnace Slag (GGBS) and fly ash (FA) as cementing materials by maintaining weight ratios of 75:25. At regular intervals, the conventional granite coarse aggregates (CAG) were replaced with recycled concrete coarse aggregates (CAR) till 100%, and the mechanical strengths in terms of compressive, split tensile and flexural strengths were investigated. Based on the results, the selected mixes were subjected to durability studies (i.e., Prolonged strength, VPV and SWA, acid and sulphate attack tests) and the microstructure studies. Compressive strength of 50 MPa and flexural strength of 4.72 MPa was achieved for C-50 at 28 days. However, the use of CAR after some limits may prove detrimental to the quality of concrete in the long run, as the durability results have shown a comparatively lesser performance while compared with the controlled mix (C-0). Hence, the test results clearly indicate that the inclusion of CAR may be proven to be helpful in producing a desirable quality of pavement quality concretes up to a limited extent of 50%. Thus, the use of PQAAC mixes in the association of CAG and CAR is considered to be one of the eco-friendly solutions to the associated disposal problems of construction and demolition wastes.