PSI - Issue 64

Zohaib Hassan et al. / Procedia Structural Integrity 64 (2024) 1184–1191 Hassan / Structural Integrity Procedia 00 (2024) 000 – 000

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Fig. 1. Particle size distribution of cement and steel slag

Table 1. Chemical composition of cement (%)

CaO 62.8

MgO

SiO 2 20.1

Al 2 O 3

Fe 2 O 3

Na 2 O

K 2 O

TiO 2 0.27

P 2 O 5 0.13

Cr 2 O 3 0.009

Mn 2 O 3

SO 3

SrO 0.09

ZnO

LOI

2.0

5.2

3.1

0.2

0.9

0.067

2.8

0.066

2.3

Table 2. Chemical composition of steel slag (%)

CaO

MgO

SiO 2

Al 2 O 3

Fe 2 O 3 15.59

Na 2 O

K 2 O 0.01

TiO 2 1.08

P 2 O 5 0.11

Cr 2 O 3

V 2 O 3 0.095

ZnO

MnO

ZrO 2

LOI 5.94

36.56

12.2

20.07

5.01

0.13

0.45

0.03 2.015

0.19

2.2. Preparation of mortars The mortars for lab scale printing were prepared in a mixer of 360-litre capacity and a mixing speed of 35 rpm. First, ordinary Portland cement, steel slag, and sand in a saturated surface dry state were mixed for 60 seconds without adding water. Superplasticizer was added to the water, and final wet mixing was performed for 6-7 minutes. Shrinkage-reducing admixture, Sika control-600 SRA, was used only for mix design in the third lab-scale print. Table 3 shows the mix design of the mortar used for lab-scale printing. Table 3: Mix design

Cement (kg)

Steel slag (kg)

Sand (kg)

Water / (Cement + Steel Slag)

Superplasticizer (kg)

0.285

0.715

0.377

0.125

0.010

2.3. Experimental setup and methodology Three lab-scale printings were performed using a printer that can inject the chemical admixture into the printing head to trigger the fast setting of the mortar. These types of printers are called bi-component or 2K type printers (Kuzmenko et al., 2022). Figure 2 shows the schematic diagram of the printing sequence for a 6-axes robotic arm printer, IRB 6700, manufactured by ABB group, connected with a printing head and a 90-litre feeding system. The printing head and feeding system are developed by XtreeE, France. The tool path was generated in Grasshopper and Rhino software. Table 4 shows the printing process parameter for all three lab-scale prints. 1st lab-scale print: The mortar used in this printing was prepared following the mix design with superplasticizer Type-1. A hollow cylindrical geometry (outer diameter = 330 mm, height = 500 mm) was printed. Printing started