PSI - Issue 70

Yankesh et al. / Procedia Structural Integrity 70 (2025) 311–318

315

The fresh mix was placed in mould in two layers and compacted on a vibration table for 45 – 60 seconds (as per IS 516:2018). After 24 hours, specimens were demoulded and cured under two conditions: ambient temperature and heat curing at 60°C. And test was conducted at 7 and 28 days.

Table 4 Ingredient proportions for the production of mix design for Geopolymer Concrete

Curing period (days) 7 & 28 7 & 28 7 & 28 7 & 28 7 & 28 7 &28 7 & 28 7 & 28 7 & 28 7 & 28 7 & 28

No. of cubes casted

No.

of

No. of beams casted

Activator (%)

ASMs (Kg/m3)

GGBS (Kg/m3)

ASMs/ GGBS

GGBS: FA:CA

Mix ID

W/B

SP

cylinder casted

M1 M2 M3 M4 M5 M6 M7 M8 M9

0

0.0 7.2

359.7 352.5 345.3 338.1 330.9 323.7 316.0 309.3 302.0 295.0 287.8

0

0.41 5.9 1: 1.9: 3.5

12 12 12 12 12 12 12 12 12 12 12

6 6 6 6 6 6 6 6 6 6 6

6 6 6 6 6 6 6 6 6 6 6

0.02 0.04 0.06 0.08 0.12 0.14 0.16 0.18 0.1

0.02 0.41 5.9 1: 1.9: 3.5 0.042 0.41 5.9 1: 2.0: 3.6 0.064 0.41 5.9 1: 2.0: 3.7 0.087 0.41 5.9 1: 2.0: 3.8 0.111 0.41 5.9 1: 2.1: 3.8 0.136 0.41 5.9 1: 2.1: 3.9 0.163 0.41 5.9 1: 2.2: 4.0 0.19 0.41 5.9 1: 2.2: 4.1 0.22 0.41 5.9 1: 2.3: 4.2 0.25 0.41 5.9 1: 2.4: 4.3

14.4 21.6 28.8 36.0 43.1 50.4 57.5 64.7 71.9

M10 M11

0.2

3. Results and Discussion 3.1. Effect of activator (%) on the development of compressive strength of GPC

The percentage of alkaline activators play an important role in developing the strength of GPC because of geopolymerisation. In this study sodium metasilicate was used as an activator by varying the percentage from 0 to 20 %. The effect of alkaline activator was observed on the compressive Strength which shows an increase in the compressive strength was achieved from 6.7 MPa to highest value of 47.97 MPa for mix design of M8 at 14 percent of sodium metasilicate. Further addition of sodium metasilicate shows a downward trend in compressive strength because the excessive alkalinity may lead to rapid dissolution which can cause the formation of porous and brittle geopolymer matrix. These results highlight the effectiveness of ingredients ratio of GGBS-to-activator in enhancing GPC performance, making it viable for many structural applications. From the fig.4. it was concluded that the compressive strength increases steadily with addition of alkaline activator from 0% to 14% content, but after that, further increase in activator shows minimal reduction in strength. 3.2 Effect of curing methods on strength development of GPC In order to investigate the effect of curing on performance of GPC, the concrete specimens were heat cured in oven at temperature of 60 o C. The test results show that temperature curing significantly improves early-age strength, as seen in Mix M8. The compressive strength increases from 18.85 MPa (water curing) to 26 MPa (heat curing) at 7 days. However, at 28 days, no significant effect was observed in the rate of increment of the compressive strength of concrete. It was observed from fig.5. that heat curing accelerates early-age strength gain in the GPC however the effect of curing becomes less significant at 28 days which can be utilize in the removal of formwork in the early period on the construction site.