PSI - Issue 70

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

593

40mm × 160mm are measured using ASTM C348's three-point bending test. The stress is applied at the center until failure. Bond Strength (BS) measures the adhesion between geopolymer mortar and substrates and is assessed using pull-off tests on cylindrical specimens (50mm diameter, 100mm height) in accordance with ASTM C882 standards. A direct tensile force is used to determine the maximum pull-off strength. Moderate neem fibre addition improves interfacial bonding by increasing matrix cohesion, however high fibre concentration may lower bond strength due to poor compaction and unequal stress distribution.

Fig.3.Compressive strength of GP mortar specimen

3.5. Discussion on results on mechanical properties of GP mortar

The mechanical properties of geopolymer mortar, such as Compressive strength (CS), Flexural strength (FS), and Bond strength (BS), are impacted by the mix composition, alkali concentration, and fibre content. The findings illustrate that the addition of neem fibre increases flexural and bond strength up to an optimum dosage, beyond which a drop occurs. Table 4 summarizes the various mechanical properties on GP mortar specimens Table 4. Mechanical properties on different dosages of neem fibres. Mix ID Compressive strength (N/mm 2 )

Flexural Strength (N/mm 2 )

Bond Strength (N/mm 2 )

7 days

28 days 36.40 37.13 38.37 38.05 35.58 37.08 38.20 39.62 37.64 36.15

28 days

M0-10M 22.10 M1-10M 22.56 M2-10M 23.06 M3-10M 22.87 M4-10M 21.50 M0-12M 22.90 M1-12M 23.46 M2-12M 24.25 M3-12M 22.98 M4-12M 21.86

4.5 4.8 5.2 5.0 4.6 4.7 5.0 5.9 5.2 4.8

1.85 2.10 2.42 2.15 1.92 1.95 2.25 2.60 2.30 2.00

Fig.4.Development of compressive strength of various GP mortars

Fig.5. Test findings on flexural and bond strength

Fig.4 demonstrates the curing age of the mortar specimen’s compressive stress characteristics at 7and 28 days. Compressive stress characteristics values range from 21.10 N/mm 2 to 24.25 N/mm 2 during 7days of ambient curing. At 28days the strength value varies from 35.58 N/mm 2 to 39.62 N/mm 2 . At 10M and 12M concentration the 0.5% of neem fibre added geopolymer composites shows maximum compressive stress value at both curing period of 7 and