Suitability of various supplementary cementitious admixtures for RAP inclusive RCCP mixes

Utilisation of reclaimed asphalt pavement (RAP) aggregates in concrete mixes generally results in strength reductions owing to asphalt-cohesion failure. Therefore, the present investigation is an effort to improve the RAP inclusive roller compacted concrete pavement (RCCP) properties by incorporating supplementary cementitious mineral admixtures (SCMs). Incorporation of 50% RAP aggregates lowered the strength and durability properties of the RCCP mix considerably. Inclusions of SCMs showed an almost negligible effect on the fresh properties; but had a prominent effect on the mechanical properties of 50RAP mix, thus, indicating their unsuitability for RAP-RCCP mixes if added in a sight to enhance its strength. However, almost all the mixes achieved the minimum stipulated flexural strength benchmark, and hence, could be recommended for RCCP mixes. Utilisation of silica-fume and bagasse-ash were further noted to improve the abrasion resistance of 50RAP mix. Likewise, the considered SCMs were also able to reduce the porosity and absorption related properties considerably and enhanced its durability in acidic environments of sulphate and chloride-rich ions. Based on the study, it is suggested to avoid the use of SCMs, if strength enhancement is the requisition, however, its utilisation is firmly suggested in order to enhance the durability performance of RAP-RCCP mixes.

Automated summary

The study found that the addition of 50% RAP aggregates significantly reduced the strength and durability of RCCP mixes, while SCMs had a negligible effect on fresh properties but a significant impact on mechanical properties. It is not recommended to use SCMs for strength enhancement, but their use can greatly improve the abrasion resistance and durability of the mixtures.