1 Introduction
2 Experimental Investigation
2.1 Materials
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The cement used in all mixture was normal OPC (53 grade) conforming to IS: 12269 (BIS 1987). Commercially available MK was used as mineral additive. Their chemical composition is specified in Table 1. The X-ray diffraction (XRD) pattern of the MK used in this study is shown in Fig. 1.Table 1Characteristics of cement and metakaolin.Chemical compositionCement (%)Metakaolin (%)Silica (SiO2)3454.3Alumina (Al2O3)5.538.3Ferric oxide (Fe2O3)4.44.28Calcium oxide (CaO)630.39Magnesium oxide (MgO)1.260.08Sodium oxide (Na2O)0.10.12Potassium oxide (K2O)0.480.50Sulphuric anhydride (SO3)1.920.22Loss on ignition (LOI)1.30.68Blaine (m2/kg)36015,000aSpecific gravity3.152.5×
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Good quality aggregates have been procured for this investigation. Crushed granite with nominal grain size of 20 mm and well-graded river sand of maximum size 4.75 mm were used as coarse and fine aggregates, respectively. The specific gravities of aggregates were determined experimentally. The coarse aggregates with 20, 12.5 mm fractions had specific gravities of 2.91 and 2.80, whereas the fine aggregate had specific gravity of 2.73, respectively.
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Commercially available poly carboxylate ether (PCE)-based super-plasticizer (SP) was used in all the concrete mixtures.
2.2 Mixture Proportions
Constituent | MK0 | MK5 | MK10 | MK15 |
---|---|---|---|---|
Cement | 533.33 | 506.67 | 480.0 | 453.33 |
Water | 160 | 160 | 160 | 160 |
Fine aggregate | 677 | 666 | 655 | 645 |
20 mm | 602 | 593 | 583 | 574 |
12.5 mm | 599 | 589 | 580 | 570 |
Metakaolin | 0 | 26.67 | 53.33 | 80.0 |
S·P | 2.13 | 2.93 | 3.47 | 4.26 |
Slump (mm) | 130 | 110 | 110 | 100 |
Plastic density | 2,520 | 2,477 | 2,446 | 2,421 |
2.3 Mixing and Casting Details
2.4 Specimens and Curing
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Three 100 × 100 × 100 mm cubes for the compressive strength.
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Three 100 × 200 mm cylinders for the splitting tensile test.
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Three 150 × 300 mm cylinders for the modulus of elasticity test.
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Two 100 × 100 × 100 mm cubes for water absorption study.
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Two 150 × 150 × 150 mm cubes for the GWT water permeability test.
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Three 150 × 150 × 150 mm cubes for the water penetration depth test.
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Two 100 × 200 mm cylinders for the rapid chloride penetrability test. Samples of 100 × 52 mm were prepared from these cylinders.
2.5 Experimental Procedures
3 Results and Discussions
3.1 Fresh Properties
3.1.1 Plastic Density
3.1.2 SP Demand
3.2 Mechanical Properties
3.2.1 Compressive Strength
Name | Compressive strength age (days) (MPa) | Splitting ten. str. (MPa) | Elastic modulus (GPa) | f
sp
/f
ck
(%) | |||
---|---|---|---|---|---|---|---|
3 days | 7 days | 28 days | 90 days | 28 days | 28 days | ||
MK0 | 56.4 | 78.23 | 91.87 | 101.00 | 4.76 | 45.43 | 5.18 |
MK5 | 59.45 | 78.74 | 95.60 | 102.50 | 4.78 | 46.57 | 5.00 |
MK10 | 53.96 | 77.85 | 98.81 | 106.13 | 5.19 | 47.16 | 5.25 |
MK15 | 48.93 | 79.88 | 91.04 | 102.96 | 4.69 | 45.42 | 5.15 |
3.2.2 Splitting Tensile Strength
3.2.3 Elastic Modulus
3.3 Durability Studies
Name | Permeability (×10−12 m/s) | Water penetration depth (mm) | Absorption (%) | Chloride permeability (Coulombs) | |
---|---|---|---|---|---|
30 min | Total | ||||
MK0 | 0.918 | 17.08 | 1.198 | 2.81 | 1,162 |
MK5 | 0.226 | 11.2 | 1.197 | 2.53 | 305 |
MK10 | 0.203 | 8.0 | 1.09 | 2.15 | 218 |
MK15 | 0.198 | 6.83 | 0.828 | 2.05 | 148 |