PSI - Issue 64

Shehroze Ali et al. / Procedia Structural Integrity 64 (2024) 1394–1401 Shehroze Ali et al. / Structural Integrity Procedia 00 (2019) 000 – 000

1396

3

oxide (Al 2 O 3 ), 2.6% ferric oxide (Fe 2 O 3 ) by mass and classified as class F low calcium fly ash in accordance with ASTM C618-19 (ASTM 2019). Table 1 shows the detailed chemical composition of slag and FA.

Table 1. Chemical composition (mass %) for slag and FA. Source material

Components SiO 2 Al 2 O 3 CaO Fe 2 O 3 K 2 O MgO Na 2 O TiO 2 P 2 O 5 Mn 2 O 3

SO 3 LOI*

Slag

34.5 62.4

12.8 26.2

42.7

0.4 2.6

0.3 1.1

5.3 0.4

0.8 0.6

0.8 0.9

0.1 0.2

0.4 0.1

1.7 0.2

0.1 2.0

FA

2.8

*LOI = Loss on ignition. A blended solution of 14 molar liquid sodium hydroxide (NaOH) and liquid sodium silicate (Na 2 SiO 3 ) was used as an alkaline solution in the mix. The NaOH solution of 14 mole/L was prepared by adding crystals of caustic soda (NaOH) in potable water (NaOH/H 2 0 =560g/440g). A magnetic stirrer was used to mix the pallets of NaOH until all the crystals of NaOH were completely dissolved in the water. The NaOH solution was mixed 24 hours before the mixing of concrete. The Na 2 SiO 3 Grade-D solution used in this study, contained 14.7% sodium oxide and 29.4% silicate with an activator modulus of 2.5 and specific gravity of 1.53 g/cm3. The Na 2 Sio 3 solution was provided by PQ Australia. The glass fibre used in this study was alkali resistant non-twisted multifilament loose chopped strands form provided by Domcrete Australia (Domcrete 2020). The individual strand was of 19 mm length, 0.14 mm diameter with an elastic modulus (E) of 70 GPa. A commercially available superplasticizer (Viscocrete 10) of a density 1,060 kg/m 3 was used to achieve the workability of the concrete. The superplasticizer was provided by Sika Australia (Sika 2020). In this study, two different mix designs were prepared to investigate the effect of glass fibre addition on the fresh and the hardened properties of slag-fly ash based geopolymer concrete (SFGC). The mix designs were based on a previous study conducted by Ali et al. (2020) at the University of Wollongong, Australia. All the mixes were prepared using a binder material made of 40% slag and 60% FA. The amount of alkaline solution was taken as 35% of the binder material, i.e., 157.5 kg/m 3 of alkaline solution per 450 kg/m 3 of binder material (slag/FA). In glass fibre reinforced slag-fly ash geopolymer concrete (GF-SFGC) mix, the volume of coarse and fine aggregate were adjusted to incorporate the dosage (1.5% by volume of the concrete) of glass fibre. The targeted compressive strength of both SFGC and GF-SFGC mixes were 50 MPa at 28 days. Table 2 shows the mix designs used in this study to produce plain (SFGC) and glass fiber reinforced (GF-SFGC) geopolymer concrete mixes. 2.2. Mix design

Table 2. Mix design of SFGC and GF-SFGC mixes.

Binder (kg/m 3 )

Aggregate (kg/m 3 )

Alkaline solution (kg/m 3 ) Water (kg/m 3 )

Super-plasticiser (kg/m 3 )

Glass fibre (kg/m 3 )

Mix ID SFGC

Coarse

Fine 552 550

Slag 180

FA 270

Na 2 SiO 3

NaOH

1295 1281

-

34.7 43.4

112.5

45

86.4

GF-SFGC

38.1

2.3. Mixing procedure and preparation of specimens All the mixes were prepared at the High-bay laboratory of School of Civil, Mining, Environmental and Architectural Engineering, University of Wollongong, Australia. The alkaline solution was prepared 1 hour prior to the mixing of geopolymer concrete. A standard laboratory mixer (mixing capacity = 0.1 m 3 ) was used to mix the SFGC and GF-SFGC mixes. The mixing started with the pouring of coarse and fine aggregate in the mixer and were mixed for 1 min. Afterwards, slag and FA were introduced in the mixer, while the mixing continued for another 2 min. At this stage in GF-SFGC mix, glass fibre was added in the dry material and uniform distribution was ensured. During the mixing, premixed alkaline solution was added and mixed for 1 min. At the final stage, the quantities of