PSI - Issue 70

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

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3.3. Workability Test on GP Mortar Mixes For ease placing of mortar in the field, the most significant factor used is workability. The workability characteristic of GP mortar is influenced by the type, length, size, shape, aspect ratio, and quantity of fibers added to the mortar. The various tests are used for testing the fresh properties. The workability of the mortar was evaluated using the flow table test and slump test, as presented in Table 5 and Fig.2. The findings demonstrated that reduction in workability corresponding to an increase in molarity. This trend correlates with earlier research (Davidovits, 2008; Temuujin et al, 2009), which indicated that the greater molarity of the alkaline activator enhances cohesiveness within the mixture, thereby reducing workability. The flow percentage fluctuated between 95% and 83%, but the slump values ranged from 82 mm to 70 mm. The reduction in the workability occurs due to contact of rigid fibres, irregular orientation, volume of fibres used and its geometrical textures. Therefore, the geopolymer mortar with fibres shows reduced workability in fresh state of mortar. According to IS 1199-2004, the slump cone test was performed for GP Mortar with and without fibre at molarity concentrations of 10M and 12M. The slump of fresh mortar is affected by various characteristics such as aggregate moisture, mixing time, temperature variations, and reactions that occur in the binder and activator solutions. Both 10M and 12M NaOH, with and without neem fibres, have medium workability in the 50-100 range according to the IS code. The mix with a low percentage of fibre content has a high slump value of 78mm when compared to a geopolymer matrix with a high fibre concentration. The negative effects on workability, however, worsen with increasing neem fibre content because the fibres absorb more alkaline solution, reducing the amount of free liquid phase in the mixture. The presence of fibres counteracts this effect beyond an optimal level, resulting in a stiffer mix that may require additional superplasticizers or modifications in water content to maintain acceptable workability, even though increasing the molarity of NaOH generally improves the workability to some extent (Abdullah et al 2018)

Fig.2. Test findings on workability on GP mortar blends

3.4. Testing of GP mortar specimens The mortar specimens of size 70.6x70.6x70.6mm 3 were tested for compressive strength (CS) characteristics at the age of 7 and 28days. To examine the hardened property of compressive test on with and without neem fibre added geopolymer mortar of concentration 10M and 12M was performed using a capacity of 2000kN standard compression testing machine, in accordance with IS: 516-1959. At the curing ages of 7days, and 28days, a total of 120 cubical specimens were cast to evaluate the compressive stress characteristics. Each compressive strength property value point corresponds to the average compressive stress of 3 test mortar cubes. Fig.3 shows the test setup for compressive strength test. Flexural Strength (FS) measures the mortar's resistance to bending forces and is an important feature for load-bearing applications. At 28 days, prismatic specimens 40mm ×