Production of RCC Using Biomass Fly and Bottom Ashes: From Laboratory to Fieldwork

Roller-compacted concrete (RCC) is widely used as an economical and durable pavement to withstand heavy loads on large areas or logging roads. The use of by-products from the cogeneration process of the paper industry, such as biomass-fly ash (BFA) as alternative supplementary cementitious materials and biomass-bottom ash (BBA) as an alternative sand, in RCC production is a promising approach in terms of economic and environmental aims. Laboratory investigations showed that two mixtures containing $10\%\mathrm{BFA}+50\%\mathrm{BBA}$ and $20\%\mathrm{BFA}+50\%\mathrm{BBA}$ with a water-to-binder ratio of 0.35–0.37 can meet the required consistency and 7-day flexural strength. However, most laboratory optimization works must be validated in situ using representative construction equipment, casting methods, and exposed conditions. Thus, these two RCC mixtures were selected for an in situ assessment through the construction of a storage slab with an area of $792{\mathrm{m}}^2$ and thickness of 0.3 m in Sherbrooke, QC, Canada. Fresh properties, isothermal deformation, internal temperature, and strength up to 308 days were measured. Core samples were cut from the slabs at ages of 28 and 308 days to follow up the concrete behavior with time. The compressive strength of the cores at an age of 308 days reached 32.9 and 30.4 MPa for the two tested mixtures, respectively. Finally, construction of the slab has allowed the recycling of 21 t of BFA and 88 t of BBA, which significantly contributes to the sustainability of the production of RCC and management of waste from the pulp and paper industry.