Experimental Study on Full-Scale Beams Made by Reinforced Alkali Activated Concrete Undergoing Flexure
Abstract
:1. Introduction
2. Materials and Methods
2.1. Specimens Geometry
2.2. Material Properties and Curing Conditions
2.3. Test Setup and Investigation
3. Results and Discussion
3.1. Modulus of Elasticity and Compression Tests
- fcm = peak stress;
- εcm = strain corresponding at peak stress;
- n = 0.8 + (fcm/17);
- k = 0.67 + (fcm/62), if εc/εcm > 1; and
- k = 1, if εc/εcm ≤ 1;
- fcm = peak stress;
- η = εc/εcm;
- εcm = strain corresponding at peak stress; and
- k = 1.05 Ecm|εcm|/fcm.
3.2. Material Flexural Behavior (MOR Tests)
3.3. Structural Response
- d = effective depth (260 mm);
- As = longitudinal reinforcement (402 mm2);
- fy = steel yield strengths (546 MPa); and
- a = shear span (1150 mm).
3.4. Numerical Analyses
3.5. Crack Pattern
- c = concrete clear cover;
- s = distance between longitudinal reinforcement bars;
- k1 = coefficient regarding bond between bars and concrete (k1 = 0.4)
- k2 = coefficient regarding stress distribution in the cross section (k2 = 0.125);
- Ф = longitudinal reinforcement bars diameter; and
- ρeff = effective reinforcement ratio.
4. Conclusions
- (1)
- Due to heat process, no increase in compressive strength over time (between 7 and 28 days) was noticed.
- (2)
- MOR tests, besides the peak strength, pointed out a rather brittle behavior in tension of the AAC herein considered, coincident to OPC.
- (3)
- Experimental Young’s modulus resulted around 20% lower than OPC concrete, which might be due to the use of a 10 mm maximum aggregate size in the mix design.
- (4)
- Constitutive law in compression was found to have a trend similar to analytical formulas proposed for OPC only in the pre-peak response. On the contrary, in the post-peak response, AAC presented rather higher ductility, in contrast with other authors.
- (5)
- Despite a difference in testing time, flexural behavior of full-scale beams did not show significant differences in terms of the overall response, uncracked and cracked-elastic parameters, yielding and ultimate load.
- (6)
- The overall behavior under flexure (cracking formation and development included) was seen to be similar to an ordinary reinforced beam made of OPC concrete, showing failure due to concrete crushing after rebar yielding.
- (7)
- The preliminary nonlinear finite element analyses performed, using a set of equations describing the linear and nonlinear phenomena of classical OPC reinforced concrete elements, gave a rather good modeling of the AAC tested beams, promoting the utilization of these already available tools for further analyses able to improve the structural understanding of ACC members.
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Component | Al2O3 | SiO2 * | CaO | Fe2O3 | MgO | K2O | Na2O | TiO2 | SO3 |
---|---|---|---|---|---|---|---|---|---|
(%) | (%) | (%) | (%) | (%) | (%) | (%) | (%) | (%) | |
Percent Composition | 28 | 56 | 2 | 5.5 | 0.2 ÷ 3 | 0.2 ÷ 2 | 0.1 ÷ 0.6 | 0.1 ÷ 1.7 | 0.2 ÷ 2 |
Parameter Investigated | Best Value |
---|---|
Extra water content, kg/m3 | 25–35 |
Total mixing time, min | 8–10 |
Rest period, h | 48 |
Curing time at 60 °C, h | 24 |
Results Investigated | AAC1-HC | AAC2-HC | VT2 | Comparison AAC1-HC-VT2 (%) | Comparison AAC2-HC-VT2 (%) |
---|---|---|---|---|---|
Maximum Load, kN | 95 | 92 | 99 | 4.0 | 7.1 |
Displacement at maximum load, mm | 131 | 90 | 136 | 3.7 | 33.8 |
Ultimate displacement, mm | 156 | 123 | 146 | −6.8 | 15.8 |
Ultimate load, kN | 86 | 88 | 94 | 8.5 | 6.4 |
Ultimate displacement/span length | 1/29 | 1/37 | 1/32 | −10.3 | 13.5 |
Yielding displacement, mm | 37 | 38 | 38 | 2.6 | 0.0 |
Yielding load, kN | 85 | 86 | 93 | 8.6 | 7.5 |
Ductility | 4.22 | 3.24 | 3.84 | −9.7 | 15.8 |
Mean crack spacing, mm | 102 | 113 | - | - | - |
Unreinforced Concrete Parameters | |
Cylinder compressive Strength f’c | 32 MPa |
Elastic modulus E | 24.6 GPa |
Maximum aggregate size | 10 mm |
Reinforced Concrete Parameters | |
Cylinder compressive strength f’c | 32 MPa |
Elastic modulus E | 24.6 GPa |
Maximum aggregate size | 10 mm |
Reinforcement direction | 90 deg |
Reinforcement ratio | 0.67% |
Transverse reinforcement yield strength fy | 545 MPa |
Transverse reinforcement ultimate strength fu | 649 MPa |
Transverse reinforcement elastic modulus Es | 206 GPa |
Transverse reinforcement strain hardening εsh | 7 millistrain |
Transverse reinforcement ultimate strain εu | 100 millistrain |
Longitudinal Steel Reinforcement Parameters | |
Yield Strength fy | 545 MPa |
Ultimate Strength fu | 649 MPa |
Elastic Modulus Es | 206 GPa |
Strain Hardening εsh | 7 millistrain |
Ultimate Strain εu | 100 millistrain |
Bearing Material Parameters | |
Direction | 90° to the horizontal |
Structural Steel Parameters | |
Yield Strength fy | 500 MPa |
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Monfardini, L.; Minelli, F. Experimental Study on Full-Scale Beams Made by Reinforced Alkali Activated Concrete Undergoing Flexure. Materials 2016, 9, 739. https://doi.org/10.3390/ma9090739
Monfardini L, Minelli F. Experimental Study on Full-Scale Beams Made by Reinforced Alkali Activated Concrete Undergoing Flexure. Materials. 2016; 9(9):739. https://doi.org/10.3390/ma9090739
Chicago/Turabian StyleMonfardini, Linda, and Fausto Minelli. 2016. "Experimental Study on Full-Scale Beams Made by Reinforced Alkali Activated Concrete Undergoing Flexure" Materials 9, no. 9: 739. https://doi.org/10.3390/ma9090739