1 Introduction
2 Background and Literature Review
2.1 Fiber-Reinforced Concrete
2.2 Previous Studies on Hemp Fibers
2.3 Previous Studies on RCA
3 Research Objectives
4 Materials and Mixes
4.1 Fibers
4.1.1 Fiber Treatment
4.1.2 Fiber Characterization
4.2 Coarse Aggregates
NCA | RCA | |||
---|---|---|---|---|
N20 | N10 | R20 | R10 | |
Maximum size aggregate (MSA) (mm) | 20 | 10 | 20 | 10 |
Specific gravity (oven-dry) | 2.59 | 2.63 | 2.3 | 2.35 |
Absorption (%) | 1.93 | 1.63 | 5.37 | 4.91 |
Dry rodded unit weight (kg/m3) | 1653 | 1579 | 1401 | 1386 |
Wear (%) (Los Angeles abrasion) | 22.16 | 29.04 |
4.3 Concrete Mixes
Mix no. | Mix ID | MSA (mm) | %Replacement of NCA by RCA | Fiber length (mm) | Fiber treatment |
---|---|---|---|---|---|
Group 1 MSA = 10 mm | |||||
1 | N10 (control 10) | 10 | 0 | – | – |
2 | R10 | 10 | 50 | – | – |
3 | N10–H20–T1 | 10 | 0 | 20 | Alkali |
4 | R10–H20–T1 | 10 | 50 | 20 | Alkali |
5 | R10–H20–T2 | 10 | 50 | 20 | Acetyl |
6 | N10–H30–T1 | 10 | 0 | 30 | Alkali |
7 | R10–H30–T1 | 10 | 50 | 30 | Alkali |
Group 2 MSA = 20 mm | |||||
8 | N20 (control 20) | 20 | 0 | – | – |
9 | R20 | 20 | 50 | – | – |
10 | N20–H20–T1 | 20 | 0 | 20 | Alkali |
11 | R20–H20–T1 | 20 | 50 | 20 | Alkali |
12 | N20–H20–T2 | 20 | 0 | 20 | Acetyl |
13 | R20–H20–T2 | 20 | 50 | 20 | Acetyl |
14 | N20–H30–T1 | 20 | 0 | 30 | Alkali |
15 | R20–H30–T1 | 20 | 50 | 30 | Alkali |
16 | R20–H30–T2 | 20 | 50 | 30 | Acetyl |
Mix ID | Cement | Water | NCA | RCA | Sand | Fibers |
---|---|---|---|---|---|---|
Group 1 MSA = 10 mm | ||||||
N10 (control 10) | 450 | 243 | 652 | 0 | 930 | – |
R10 | 450 | 243 | 326 | 326 | 930 | – |
N10–H20–T1 | 489.13 | 264.13 | 386.42 | 0 | 1010.87 | 11.41 |
R10–H20–T1 | 489.13 | 264.13 | 193.21 | 193.21 | 1010.87 | 11.41 |
R10–H20–T2 | 489.13 | 264.13 | 193.21 | 193.21 | 1010.87 | 11.41 |
N10–H30–T1 | 489.13 | 264.13 | 386.42 | 0 | 1010.87 | 11.41 |
R10–H30–T1 | 489.13 | 264.13 | 193.21 | 193.21 | 1010.87 | 11.41 |
Group 2 MSA = 20 mm | ||||||
N20 (control 20) | 400 | 216 | 905 | 0 | 763 | – |
R20 | 400 | 216 | 452.5 | 452.5 | 763 | – |
N20–H20–T1 | 434.78 | 234.78 | 630.43 | 0 | 829.34 | 11.41 |
R20–H20–T1 | 434.78 | 234.78 | 315.22 | 315.22 | 829.34 | 11.41 |
N20–H20–T2 | 434.78 | 234.78 | 630.43 | 0 | 829.34 | 11.41 |
R20–H20–T2 | 434.78 | 234.78 | 315.22 | 315.22 | 829.34 | 11.41 |
N20–H30–T1 | 434.78 | 234.78 | 630.43 | 0 | 829.34 | 11.41 |
R20–H30–T1 | 434.78 | 234.78 | 315.22 | 315.22 | 829.34 | 11.41 |
R20–H30–T2 | 434.78 | 234.78 | 315.22 | 315.22 | 829.34 | 11.41 |
MIX ID | Cement | NCA | Sand | Total Cost (USD) | |||
---|---|---|---|---|---|---|---|
Weight (kg) | Cost (USD) | Weight (kg) | Cost (USD) | Weight (kg) | Cost (USD) | ||
N20 | 400 | 60.00 | 905 | 9.05 | 763 | 12.21 | 81.26 |
R20 | 400 | 60.00 | 452.5 | 4.53 | 763 | 12.21 | 76.73 |
N20–H20–T1 | 434.78 | 65.22 | 630.43 | 6.30 | 829.34 | 13.27 | 84.79 |
R20–H20–T1 | 434.78 | 65.22 | 315.22 | 3.15 | 829.34 | 13.27 | 81.64 |
5 Test Results and Analysis
5.1 Fibers
5.1.1 Morphology
5.1.2 Crystallinity
I002 | Iam | Ic (%) | |
---|---|---|---|
Untreated | 226 | 67 | 70.35 |
Alkali | 250 | 67 | 73.20 |
Silane | 83 | 31 | 62.65 |
Acetyl | 268 | 74 | 72.39 |
5.1.3 Thermal Analysis
5.2 Slump
Mix ID | Slump (cm) | Compressive strength | Modulus of elasticity | MOR | Splitting tensile strength | ||||
---|---|---|---|---|---|---|---|---|---|
Value (MPa) | Ratioa | Value (GPa) | Ratioa | Value | Ratioa | Value | Ratioa | ||
Group 1 MSA = 10 mm | |||||||||
N10 (control 10) | 23 | 38 | – | 30.8 | – | 5.1 | – | 2.24 | – |
R10 | 22 | 34.25 | 0.90 | 28.8 | 0.94 | 4.8 | 0.94 | 2.21 | 0.99 |
N10–H20–T1 | 16 | 23 | 0.61 | 22.2 | 0.72 | 4.95 | 0.97 | 2.08 | 0.93 |
R10–H20–T1 | 13 | 24.5 | 0.64 | 22.8 | 0.74 | 4.35 | 0.85 | 2.10 | 0.94 |
R10–H20–T2 | 14 | 24.5 | 0.64 | 22.9 | 0.74 | 4.2 | 0.82 | 2.14 | 0.96 |
N10–H30–T1 | 13 | 24 | 0.63 | 22.7 | 0.74 | 4.8 | 0.94 | 1.94 | 0.87 |
R10–H30–T1 | 13 | 24 | 0.63 | 22.5 | 0.73 | 4.2 | 0.82 | 1.99 | 0.89 |
Group 2 MSA = 20 mm | |||||||||
N20 (control 20) | 20 | 39 | – | 33.2 | – | 5.25 | – | 2.64 | – |
R20 | 20 | 35 | 0.90 | 31.4 | 0.95 | 4.57 | 0.87 | 2.53 | 0.96 |
N20–H20–T1 | 14 | 28 | 0.72 | 26 | 0.78 | 5.1 | 0.97 | 2.51 | 0.95 |
R20–H20–T1 | 10 | 25 | 0.64 | 23.7 | 0.71 | 4.65 | 0.89 | 2.31 | 0.88 |
N20–H20–T2 | 12 | 27 | 0.69 | 24.9 | 0.75 | 4.65 | 0.89 | 2.55 | 0.97 |
R20–H20–T2 | 11 | 25 | 0.64 | 23.4 | 0.70 | 4.5 | 0.86 | 2.52 | 0.95 |
N20–H30–T1 | 14 | 32 | 0.82 | 27.2 | 0.82 | 4.95 | 0.94 | 2.3 | 0.87 |
R20–H30–T1 | 10 | 26 | 0.67 | 24.3 | 0.73 | 4.5 | 0.86 | 2.1 | 0.80 |
R20–H30–T2 | 12 | 25 | 0.64 | 23.7 | 0.71 | 4.5 | 0.86 | 2.4 | 0.91 |
5.3 Mechanical Properties
5.3.1 Compressive Strength
5.3.2 Modulus of Elasticity
5.3.3 Flexural Strength
Mix ID | Fracture energy | µa |
---|---|---|
(kN-m) | ||
Group 1 MSA = 10 mm | ||
N10 (control 10) | 3.77 | – |
R10 | 4.04 | 1.07 |
N10–H20–T1 | 11.52 | 3.06 |
R10–H20–T1 | 8.53 | 2.26 |
R10–H20–T2 | 13.29 | 3.53 |
N10–H30–T1 | 7.37 | 1.95 |
R10–H30–T1 | 9.22 | 2.45 |
Group 2 MSA = 20 mm | ||
N20 (control 20) | 3.21 | – |
R20 | 2.71 | 0.84 |
N20–H20–T1 | 18.02 | 5.61 |
R20–H20–T1 | 6.66 | 2.07 |
N20–H20–T2 | 9.09 | 2.83 |
R20–H20–T2 | 10.47 | 3.26 |
N20–H30–T1 | 8.18 | 2.55 |
R20–H30–T1 | 11.11 | 3.46 |
R20–H30–T2 | 8.63 | 2.69 |
5.3.4 Splitting Tensile Strength
5.4 Durability Testing
5.4.1 Absorption
Mix ID | Absorption | |
---|---|---|
Value (%) | Ratioa | |
Group 1 MSA = 10 mm | ||
N10 (control 10) | 6.19 | – |
R10 | 7.53 | 1.22 |
N10–H20–T1 | 8.75 | 1.41 |
R10–H20–T1 | 9.93 | 1.60 |
R10–H20–T2 | 9.51 | 1.54 |
N10–H30–T1 | 9.01 | 1.46 |
R10–H30–T1 | 9.60 | 1.55 |
Group 2 MSA = 20 mm | ||
N20 (control 20) | 6.51 | – |
R20 | 7.93 | 1.22 |
N20–H20–T1 | 9.63 | 1.48 |
R20–H20–T1 | 10.10 | 1.55 |
N20–H20–T2 | 9.58 | 1.47 |
R20–H20–T2 | 10.35 | 1.59 |
N20–H30–T1 | 9.69 | 1.49 |
R20–H30–T1 | 10.22 | 1.57 |
R20–H30–T2 | 10.05 | 1.54 |
5.4.2 Thermal Conductivity
Mix ID | Thermal conductivity | |
---|---|---|
Value (watt/meter. °Kelvin) | Ratioa | |
Group 1 MSA = 10 mm | ||
N10 (control 10) | 1.728 | – |
R10 | 1.977 | 1.14 |
R10–H20–T1 | 1.605 | 0.93 |
R10–H20–T2 | 1.622 | 0.94 |
N10–H30–T1 | 1.401 | 0.81 |
Group 2 MSA = 20 mm | ||
N20 (control 20) | 1.939 | – |
R20 | 1.821 | 0.94 |
R20–H20–T1 | 1.513 | 0.78 |
N20–H20–T2 | 1.691 | 0.87 |
N20–H30–T1 | 1.575 | 0.81 |
R20–H30–T2 | 1.544 | 0.80 |
5.4.3 Resistance to Freeze–Thaw Cycles
Mix ID | Relative dynamic modulus of elasticity PC (%) | ||||
---|---|---|---|---|---|
c = 0 | c = 36a | c = 72 | c = 108 | c = 144 | |
Group 1 MSA = 10 mm | |||||
N10 (control 10) | 100 | 94.1 | 90.2 | 86.2 | 83.5 |
R10 | 100 | 98.2 | 89.5 | 87.5 | 77.0 |
N10–H20–T1 | 100 | 93.8 | 87.2 | 81.6 | 77.0 |
R10–H20–T1 | 100 | 90.5 | 90.5 | 90.5 | 88.5 |
R10–H20–T2 | 100 | 90.2 | 88.5 | 83.7 | 79.5 |
N10–H30–T1 | 100 | 95.2 | 93.0 | 93.0 | 90.4 |
R10–H30–T1 | 100 | 95.2 | 93.0 | 90.4 | 90.4 |
Group 2 MSA = 20 mm | |||||
N20 (control 20) | 100 | 93.2 | 79.2 | 62.4 | 51.0 |
R20 | 100 | 92.7 | 70.2 | 57.8 | 31.0 |
N20–H20–T1 | 100 | 88.1 | 79.2 | 70.8 | 42.0 |
N20–H20–T2 | 100 | 83.2 | 75.3 | 63.7 | 55.5 |
R20–H20–T2 | 100 | 85.8 | 78.3 | 69.5 | 53.2 |
R20–H30–T1 | 100 | 87.7 | 77.2 | 70.5 | 56.5 |