PSI - Issue 68

Eyad Shahin et al. / Procedia Structural Integrity 68 (2025) 238–244 E. Shahin et al. / Structural Integrity Procedia 00 (2025) 000–000

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2. Experimental program 2.1. Materials

In this study, the materials used in the production of PE-ECC mixture include ASTM C 150 18 TYPE I Portland cement, Ground Granulated Blast-furnace Slag (GGBS), silica fume, dune sand, water, Ultra-high Molecular Weight Polyethylene (UHMWPE) fiber 2% by total volume, and GLNM 120T Superplasticizer (SP) which is based on modified polycarboxylic ether. GGBS was tested as a potential cement substitute at three replacement levels: 30%, 60%, and 90%. The chemical composition of cement and GGBS is presented in Table 1. To minimize the matrix non-uniformity, larger aggregates was not used. Instead, fine dune sand with a maximum grain size of 300 µm was used in this research. PE fibers used in this research were provided by Quantumeta Co., Ltd., China. The mechanical and geometry properties of PE fibers are listed in Table 2.

Table 1. Chemical Composition of OPC and GGBS (%)

Binder

SiO 2

Fe 2 O 3

Al 2 O 3

CaO

MgO 0.99 6.00

SO 3 2.62 0.10

Na 2 O

Cl

LOI 2.89 1.67

Fineness (Kg/m2)

Cement (OPC)

20.70 34.90

3.86 0.60

5.40

63.22 39.80

0.56 0.55

0.02 0.02

346 430

GGBS

14.46

Table 2. Mechanical and geometry properties of PE fiber Fiber Density (g/cm3) Length (mm)

Filament Diameter (µm)

Melting Range (°C) 144-152

Tensile Strength (MPa)

Elongation at Break (%)

PE

0.97-0.98

12/18

24

3000

1-3

2.2. Mix Proportions design and preparation process The mixture proportions are shown in Table 3. Cement was partially replaced by GGBS at replacement levels of 30%, 60%, and 90% by weight, referred to as G30, G60, and G90, respectively. The water-to-binder ratio (W/B) was kept constant at 0.20 to maintain consistency across mixes. PE fibers were incorporated at a moderate volume fraction of 2%. Achieving proper fiber dispersion is crucial for ensuring excellent mechanical properties in the hardened ECC. A homogenous fiber distribution helps enhance tensile strength, crack control, and ductility, contributing to the material’s strain-hardening behavior. The uniform dispersion of fibers is particularly important in GGBS-ECC mixtures, as poor dispersion can lead to weak zones where cracks may propagate prematurely, undermining performance. Therefore, the following mixing procedure was adopted to ensure uniform dispersion of PE fibers in the fresh GGBS-ECC mortar: First, the dry materials (dune sand, cement, silica fume, and GGBS) were mixed for 1–2 minutes. Then, water and superplasticizer (SP) were added, and the mixture was stirred until the mortar achieved the desired fluidity and uniformity, which took about 3–4 minutes. Finally, the fibers were gradually introduced and mixed for an additional 6–8 minutes to ensure even dispersion without fiber clumping. The fresh GGBS-ECC was cast into various molds for different tests. The specimens were demolded after 24 hours and cured under a controlled laboratory environment (23 ± 2°C) for 28 days.

Table 3. PE-ECC Mix Proportions (g/L) Mix No. Cement GGBS

Silica Fume

Dune sand

Water

SP 25 25 25

PE Fiber

G30 G60 G90

1036

444 888

125 125 125

440 440 440

294 294 294

20 20 20

592 148

1332