#18: Beams and columns of low-calcium fly ash-based geopolymer concrete

Curtin Research Report on Fly Ash-Based Geopolymer Concrete
Reinforced beams and columns
by Djwantoro Hardjito and B.Vijaya Rangan
Research Report GC 3 (120 pages) (mar. 2006)
Faculty of Engineering, Curtin University of Technology
Perth, Australia

This Research Report describes the behaviour and strength of reinforced low-calcium fly ash-based geopolymer concrete structural beams and columns. Earlier, Research Reports GC1 and GC2 covered the development, the mixture proportions, the short-term properties, and the long-term properties of low-calcium fly ash-based geopolymer concrete, see paper #17 .

Twelve reinforced geopolymer concrete beams and twelve reinforced geopolymer concrete columns were made and tested. The test results were compared with the predictions of methods of calculations available for reinforced Portland cement concrete and the design provisions given in the Australian Standard for Concrete Structures AS3600 and the American Concrete Institute Building Code ACI318-02. The major conclusions drawn from this research are:

Reinforced Geopolymer Concrete Beams :
1. The crack patterns observed for reinforced geopolymer concrete beams were similar to those reported in the literature for reinforced Portland cement concrete beams. All beams failed in flex in a ductile manner accompanied by crushing of the concrete in the compression zone.
2 As expected, the cracking moment increased as the concrete compressive strength increased.
3. As expected, the flexural capacity of the beams was influenced by the longitudinal tensile reinforcement ratio and the concrete compressive strength.
4. The ductility of reinforced geopolymer concrete beams, as indicated by the ratio of mid-span deflection at ultimate moment-to-mid-span deflection at yield moment, increased as the tensile reinforcement ratio decreased.
5. The flexural capacity of test beams were calculated using the flexural design provisions contained in the draft AS3600 (2005). Good correlation is found between the test and calculated ultimate bending moments.
6. The measured service load deflections of test beams were compared with the values calculated using the serviceability provisions of draft AS3600 (2005). Good correlation between test and calculated values is found.
7. The study demonstrated that the design provisions contained in the draft Australian Standard for Concrete Structures AS3600 (2005) are applicable to reinforced geopolymer concrete beams.

Reinforced Geopolymer Concrete Columns :
1. The crack patterns and failure modes observed for geopolymer concrete columns were similar to those reported in the literature for reinforced Portland cement concrete columns.
2. As expected, the capacity of test columns was influenced by the longitudinal reinforcement ratio, concrete compressive strength, and the load-eccentricity.
3. The mid-height deflection of test columns decreased as the load-eccentricity decreased. The behaviour of geopolymer test columns was similar to that of reinforced Portland cement columns reported in the literature.
4. The load capacity of test columns were calculated using a simplified stability analysis proposed by Rangan (1990) for reinforced Portland cement concrete columns, and the design provisions contained in Section 10.4 of AS3600 and Rule 10.12 of ACI318-02. Good correlation between test and calculated failure loads is found.
5. The study demonstrated that the design provisions contained in the Australian Standard for Concrete Structures AS3600 and the American Concrete Institute Building Code ACI318-02 are applicable to reinforced geopolymer concrete columns.

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