PSI - Issue 70

Kavitha E. et al. / Procedia Structural Integrity 70 (2025) 588–595

591

2.5. Neem fibre The neem fibre is supplied by the Vruksha composites, Guntur, Andhra Pradesh. These fibres are used in various forms in concrete as chopped fibres and long fibres. The neem fibre is whitish brown in colour, with a length of 30 mm and a thickness of 0.2 mm. The sample of neem fibre is shown in Fig.1.

Fig.1. Sample of neem fibre

3. Methodology 3.1. Mix Proportion

Geopolymer mortar was made using FA, GGBFS, M-Sand and alkaline activator solution with neem fibre. The total water content was determined using the water present in both alkaline activator solution with no additional water. A basic materials, solution and water were used to generate geopolymer mortar with 1:3 ratio. Neem fibers are incorporated into the total mass of binder component. (Dathe et al., 2024). The materials required for the mix proportion and mix ID’s of geopolymer mortar with the two different molarity are tabulated in Tables 2 and 3.

Table 2. Material Quantities for 10M and 12M NaOH Solutions (per 1 m³ mix) Molarity

Materials kg/m3

Fly Ash (50%)

GGBFS (50%)

Fine Aggregate (M Sand)

Na 2 SiO 3

NaOH Water in Na 2 SiO 3

Water in NaOH Solution

Total Water Content

10M 275 12M 275

275 275

1650 1650

165 165

66 66

74.25 74.25

43.56 39.6

117.81 113.85

Table 3. Mix proportions

Mix ID Fly Ash (%)

GGBFS (%)

Neem Fibre (%)

Fine Aggregate NaOH

Alkaline/Binder Ratio

Water/Binder Ratio

Molarity (M)

M0-10M 50 M1-10M 50 M2-10M 50 M3-10M 50 M4-10M 50 M0-12M 50 M1-12M 50 M2-12M 50 M3-12M 50 M4-12M 50

50 50 50 50 50 50 50 50 50 50

0.00 0.25 0.50 0.75 1.00 0.00 0.25 0.50 0.75 1.00

1:3 1:3 1:3 1:3 1:3 1:3 1:3 1:3 1:3 1:3

10 10 10 10 10 12 12 12 12 12

0.42 0.42 0.42 0.42 0.42 0.42 0.42 0.42 0.42 0.42

0.21 0.21 0.21 0.21 0.21 0.21 0.21 0.21 0.21 0.21

3.2. Mixing, Casting and Curing Fly ash and GGBS were initially dry mixed for 5 minutes. M-sand was subsequently added and mixed for a further 5 minutes. The dry mix included pre- mixed NaOH and Na₂SiO₃ solutions. This was blended for 4 minutes. Finally, fibers were added and well mixed for 1 minute to produce a homogenous concrete mix. After mixing, the fresh geopolymer mortar was evaluated for workability before being cast into moulds. The specimens were cured for 7 and 28 days to evaluate the mechanical and durability characteristics.For each mix 3 samples were casted to examine the behavior of mortar.