1 Introduction
2 Experimental Program
2.1 Methodology
Parameters | Level 1 | Level 2 | Level 3 |
---|---|---|---|
GGBFS content (kg/m3) | 350 | 450 | 550 |
W/B ratio | 0.3 | 0.4 | 0.5 |
Admixture dosage* (%) | 1 | 2 | 3 |
Mix No. | GGBFS content (kg/m3) | W/B ratio | Admixture dosage (%) |
---|---|---|---|
Mix1 | 350 | 0.3 | 1 |
Mix2 | 350 | 0.4 | 2 |
Mix3 | 350 | 0.5 | 3 |
Mix4 | 450 | 0.3 | 2 |
Mix5 | 450 | 0.4 | 3 |
Mix6 | 450 | 0.5 | 1 |
Mix7 | 550 | 0.3 | 3 |
Mix8 | 550 | 0.4 | 1 |
Mix9 | 550 | 0.5 | 2 |
2.2 Materials
Component | SiO2 | Fe2O3 | Al2O3 | CaO | MgO | SO3 | Cl |
---|---|---|---|---|---|---|---|
Content (%) | 39.8 | 1.20 | 11.2 | 34.4 | 7.6 | 0.45 | 0.013 |
Component | Na2O | H2O |
---|---|---|
Content (%) | 60.25 | 39.75 |
Component | Na2O | SiO3 | H2O |
---|---|---|---|
Content (%) | 11.98 | 31.0 | 57.0 |
Base | Appearance/color | Density (at 20 °C) | Chlorides |
---|---|---|---|
Naphthalene formaldehyde sulphonate | Brown liquid | 1.20 kg/l | No |
Base | Appearance/Color | pH value | Solid content | Density (at 20 °C) | Chlorides |
---|---|---|---|---|---|
Polycarboxylates | Clear liquid | 4.0 | 40% | 1.08 kg/l | No |
2.3 Design of Mixes
Mix No. | GGBFS | SS | SH | Water | F.A.a | C.A.b | NPA |
---|---|---|---|---|---|---|---|
Mix1-N | 350 | 113 | 36 | 24 | 665 | 1330 | 3.5 |
Mix2-N | 350 | 113 | 36 | 57 | 635 | 1269 | 7.0 |
Mix3-N | 350 | 113 | 36 | 90 | 604 | 1208 | 10.5 |
Mix4-N | 450 | 145 | 46 | 29 | 605 | 1209 | 9.0 |
Mix5-N | 450 | 145 | 46 | 71 | 565 | 1130 | 13.5 |
Mix6-N | 450 | 145 | 46 | 122 | 526 | 1051 | 4.5 |
Mix7-N | 550 | 177 | 56 | 32 | 544 | 1088 | 16.5 |
Mix8-N | 550 | 177 | 56 | 94 | 496 | 991 | 5.5 |
Mix9-N | 550 | 177 | 56 | 146 | 447 | 895 | 11.0 |
Mix No. | GGBFS | SS | SH | Water | F.A.a | C.A.b | PCA |
---|---|---|---|---|---|---|---|
Mix1-P | 350 | 113 | 36 | 24 | 665 | 1330 | 3.5 |
Mix2-P | 350 | 113 | 36 | 57 | 635 | 1269 | 7.0 |
Mix3-P | 350 | 113 | 36 | 90 | 604 | 1208 | 10.5 |
Mix4-P | 450 | 145 | 46 | 29 | 605 | 1209 | 9.0 |
Mix5-P | 450 | 145 | 46 | 71 | 565 | 1130 | 13.5 |
Mix6-P | 450 | 145 | 46 | 122 | 526 | 1051 | 4.5 |
Mix7-P | 550 | 177 | 56 | 32 | 544 | 1088 | 16.5 |
Mix8-P | 550 | 177 | 56 | 94 | 496 | 991 | 5.5 |
Mix9-P | 550 | 177 | 56 | 146 | 447 | 895 | 11.0 |
2.4 Mixing Protocol
2.5 Specimens Preparation and Testing
3 Tests Results and Discussion
3.1 Slump Test
3.1.1 NPA-based Mixes
Parameter | GGBFS content (kg/m3) | W/B ratio | Admixture dosage (%) |
---|---|---|---|
Percentage of participation (%) | 57.09 | 29.89 | 13.02 |
Optimum level | 550 | 0.5 | 1.0 |
3.1.2 PCA-based Mixes
Parameter | GGBFS content (kg/m3) | W/B ratio | Admixture dosage (%) |
---|---|---|---|
Percentage of participation (%) | 31.28 | 11.56 | 57.16 |
Optimum level | 450 | 0.5 | 2.0 |
3.1.3 NPA vs PCA Mixes
Admixture Type | Optimum level | Maximum obtained slump value (mm) | ||
---|---|---|---|---|
GGBFS content (kg/m3) | W/B ratio | Admixture dosage (%) | ||
NPA | 550 | 0.5 | 1.0 | 200 |
PCA | 450 | 0.5 | 2.0 | 120 |
3.2 Slump Loss
3.3 Compressive Strength
3.3.1 NPA-based Mixes
Parameter | GGBFS content (kg/m3) | W/B ratio | Admixture dosage (%) |
---|---|---|---|
Percentage of participation (%) | 42.53 | 20.63 | 36.85 |
Optimum level | 550 | 0.3 | 1.0 |
3.3.2 PCA-based Mixes
Parameter | GGBFS content (kg/m3) | W/B ratio | Admixture dosage (%) |
---|---|---|---|
Percentage of participation (%) | 15.47 | 50.90 | 33.63 |
Optimum level | 450 | 0.4 | 2.0 |
3.3.3 NPA vs PCA Mixes
Admixture type | Optimum level | Maximum obtained 28-day compressive strength (mm) | ||
---|---|---|---|---|
GGBFS content (kg/m3) | W/B ratio | Admixture dosage (%) | ||
NPA | 550 | 0.3 | 1.0 | 69 |
PCA | 450 | 0.4 | 2.0 | 54 |
4 Conclusions
-
The efficiency of naphthalene-based admixtures (NPA) on improving the workability, in terms of initial slump value and slump loss rate, of the geopolymer concrete mixes was better than that of polycarboxylate-based admixtures (PCA). The NPA-based mixes achieved the best initial slump value of 200 mm and the lowest rate of slump loss (90 mm after 15 min and 55 mm after 20 min), while the best PCA-based mix achieved an initial slump value of 120 mm and a rate of slump loss (10 mm after 15 min and zero after 20 min).
-
Using NPA, in the geopolymer concrete, improved the compressive strength compared to PCA. The NPA-based mixes achieved the highest 28-day compressive strength of 69 MPa, with about 27.8% more than the highest 28-day compressive strength achieved by the PCA-based mixes (54 MPa).
-
Among the studied parameters, the GGBFS content was the most significant parameter that affected both workability and compressive strength of NPA-based mixes, while the admixture dosage and W/B ratio were the most significant parameters that affected the workability and compressive strength of PCA-based mixes, respectively.