Mix Design and Mechanical Properties of Fly Ash and GGBFS-Synthesized Alkali-Activated Concrete (AAC)

Abstract

Cement is one of the construction materials widely used around the world in order to develop infrastructure and it is also one of the factors affecting economies. The production of cement consumes a lot of raw materials like limestone, which releases CO 2 into the atmosphere and thus leads to global warming. Many investigations are underway in this area, essentially focusing on the eco-accommodating environment. In the research, an alternative material to cement binder is geopolymer binder, with the same efficiency. This paper presents scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis of factory byproducts (i.e., fly ash and ground granulated blast furnace slag (GGBFS)). The mix design process for the manufacture of alkali-activated geopolymer binders synthesized by fly ash and GGBFS is presented. The mechanical properties (compression, split tensile and flexural strength, bond strength) of geopolymer concrete at different mix proportions and at dissimilar curing conditions were also investigated. Geopolymer concrete synthesized with 30% fly ash and 70% GGBFS has better properties at 14 M of NaOH and cured in an oven for 24 h at 70 • C.Infrastructures 2019, 4, 20 2 of 11 affecting the mechanical and durable properties of geopolymer concrete. These are: fineness of fly ash and GGBFS, molarities of NaOH solution, and curing conditions (sunlight and oven) [5,6]. With an increase of molarities of NaOH solution, the mechanical properties are also increased. Generally up to 14 M NaOH solution is economic and it is suggested can improve the durability of geopolymer concrete [7]. Table 1 indicates the density, surface area and distribution of particle sizes of different materials like ordinary Portland cement (OPC), flyash, silica fume and GGBFS.

Influence of Na2O Content and Ms (SiO2/Na2O) of Alkaline Activator on Workability and Setting of Alkali-Activated Slag Paste

“…However, because the cement industry emits large amounts of CO 2 and consumes much energy in the supply of raw materials and production processes, efforts are needed to reduce CO 2 emission and energy consumption by replacing cement with supplementary cementitious materials (SCMs) such as ground granulated blast furnace slag (GGBFS) and fly ash (FA). Thus, in order to totally replace cement with GGBFS and FA attempts have been made to create zero-cement concrete by the alkali activation of GGBFS and FA [1,2,3,4,5].…”

Effect of GGBFS on Workability and Strength of Alkali-activated Geopolymer Concrete

“…However, surface cracks caused by the shrinkage of the alkali-activated slag concrete have been reported by some investigators [10]. Moderate compressive strength with the participation of slag in GPC at ambient curing has been reported by some investigators [21,25,[32][33][34]. Accelerated polymerization process among fly ash, GGBFS, and AAS are predominant at 60°C [25,35].…”

“…The concrete-filled moulds wrapped with plastic sheet were left at ambient temperature for 60 minutes. After 60 minutes of ambient curing, the moulds [21,25] were kept in an oven for heat curing at a controlled temperature of 60°C for 24 hours. The oven-cured specimen moulds shown in Figure 3 were kept at an ambient temperature of 24-26°C and relative humidity of 60 ± 5% until testing.…”

“…The compressive strength of geopolymer concrete increased with the increase of slag content and concentration of NaOH solution [10,20]. Bellum (2019) found that geopolymer concrete containing 30% fly ash and 70% GGBS yielded compressive strength of 34.15 MPa at a ratio of AAS to GSB of 0.35 and 70 • C oven curing for 24Hr followed by 28 days of ambient curing [21]. Ma et al (2019) reported a maximum compressive strength with 30% slag in geopolymer concrete.…”

Role of Sintering Temperature in Production of Nepheline Ceramics-Based Geopolymer with Addition of Ultra-High Molecular Weight Polyethylene

“…Any materials that contain mostly silica and alumina can be used as source material in the production of geopolymer. These can be industrial byproduct materials such as fly ash, ground granulated blast furnace slag (GGBFS), red mud, silica fume, and rice hush ash [ 10 , 11 , 12 , 13 ]. On the other hand, natural minerals such as kaolin and metakaolin could also be used as source materials.…”