Abstract
There is a constant drive for the development of ultra-high-performance concrete using modern green engineering technologies. These concretes have to exhibit enhanced durability and incorporate energy-saving and environment-friendly functions. The object of this work was to develop a green concrete with an improved sulfate resistance. In this new type of concrete, recycled aggregates from construction and demolition (C&D) waste were used as coarse aggregates, and granulated blast furnace slag (GGBS) and fly ash-based geopolymer were used to totally replace the cement in concrete. This study focused on the sulfate resistance of this geopolymer recycled aggregate concrete (GRAC). A series of measurements including compression, X-ray diffraction (XRD), and scanning electron microscopy (SEM) tests were conducted to investigate the physical properties and hydration mechanisms of the GRAC after different exposure cycles in a sulfate environment. The results indicate that the GRAC with a higher content of GGBS had a lower mass loss and a higher residual compressive strength after the sulfate exposure. The proposed GRACs, showing an excellent sulfate resistance, can be used in construction projects in sulfate environments and hence can reduce the need for cement as well as the disposal of C&D wastes.
Highlights
The new global standards of modern engineering technologies, continuously requiring more energy-saving and environment-friendly infrastructure [1,2], are driving the development of recycled construction materials
Notes: S%, percentage of GGBS by weight; W/B, water-binder ratio; NCA, natural coarse aggregates; RCA, recycled coarse aggregates; SA, river sand; OPC, ordinary Portland cement; S, GGBS; F, flay ash; W, total water, including water in the retarding water-reducer, NaOH solution and Na2 SiO3 solution; NaOH, prepared NaOH solution; Na2 SiO3, prepared Na2 SiO3 solution; AW, additional water needed for the pre-wetting of RCA, according to the water absorption of RCA, shown in Table 2; retarding water reducer (RWR), retarding water-reducer
To examine the hydration mechanism and sulfate resistance of geopolymer recycled aggregate concrete (GRAC), X-ray diffraction (XRD), and Scanning Electron Microscopy (SEM) tests were conducted for the samples, from different depths
Summary
The new global standards of modern engineering technologies, continuously requiring more energy-saving and environment-friendly infrastructure [1,2], are driving the development of recycled construction materials. Transforming C&D waste into aggregates in concrete production is considered a promising recycling technology, promoting the reuse of solid waste and reducing environmental pollution, and the consumption of raw materials [24,25]. This may be one of the significant efforts required for achieving sustainable construction.
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