This research is conducted to study the experimental behavior of composite steel-concrete columns with basalt additives. Various percentages of basalt are added to the concrete mixes to investigate its effect on the total axial compressive capacity of the columns. Expected failure scenarios of the columns are: concrete compressive failure, buckling of steel section, and de-bonding between steel and concrete sections. A conventional limestone composite column was used as base mix. The results of the study indicate a significant improvement in structural behavior and strength of the columns by increasing the percentage of basalt content.
Composite columns using limestone were widely used from early 1900s. However, none or very little research conducted for using basalt in composite columns. Viest in his 1960 review of research, notes that the important factor in composite actions is the bond between concrete and steel [
The steel-concrete composite column is a new composite member that can achieve constructability and economy by filling the empty space in the steel H-flange with concrete. Composite columns are constructed with rolled or built-up steel section. The resulting members are able to support significantly higher loads than reinforced concrete columns of the same sizes.
A structural member composed of two or more dissimilar materials joined together (to act as a unit in which the resulting system) is stronger than the sum of its parts. An example in civil structures is the steel-concrete composite column in which a steel wide-flange shape (I or W shape) is filled with various percentages of basalt to be compared with base limestone concrete mix. Basalt is hard, dense volcanic igneous rock that can be found in most countries across the world.
Basaltic rocks are available in Jordan in many places especially in the Northeastern volcanic Plateau in Harrat Ash Shaam, Asi and Shalabi, 2005 [
The basalt aggregates used in this research were tested for chemical composition at the Department of Chemistry of the University of Jordan by using the X-Ray Fluorescence (XRF) test. The results of this test are summarized in
because their graphs are almost identical. The average deflections and strains represent one curve for each group of three specimens.
It is obvious from
The first author conducted laboratory tests on 18 columns. The chart in
The geometry of the steel section was shown in
Five mixes were prepared; namely limestone (0% basalt as base mix), 25%, 50%, 75%, and 100% basalt. The composition of each mix is presented in
water cement ratio was 0.7 including 0.25 for hydration, and the cement was 350 kg per cubic meter of concrete.
The center line of the composite columns were coincided with the centerline of the testing machine carefully to avoid any eccentricity and the two ends of the column were attached to the ground and to the testing machine by using rectangular steel (to avoid any horizontal movement). The mid height of the columns were marked at both sides and the dial gage (transducers) was attached to the level of marked line to measure the deflection of concentric composite columns. Similarly the other side of the column was marked, and two demic gages (transducers) (ASTM426 strain gage and BS1881:206) were attached to the column 10 cm above and below the center line. In this case the vertical distance between the two gages were 20 cm. The strain and deflection were taken from the two gages directly by using correction factor for the testing machine for both strain and deflection. The loads were applied gradually to the specimens till failure.
There was no cyclic loading applied.
After loading the column and prior to initiation of buckling, it was noted that the specimen starts to have hair horizontal cracks (parallel to the marked line). The cracks occurred in the tension region. No cracks noticed in the compression region. The load was applied gradually to the specimen and the readings were taken at various stages of loading. For this test only ascending loading was used (no cyclic loading). Out-of-plane deformation (buckling) was measured using only one dial gage since the column is short and the width is also small. The set-up of the specimen is shown in Figures 3 and 4 with strain and deflection gages attached. The strains versus loads are shown for various percentage of basalt in
1) The three steel and limestone composite columns were taken in this experimental program as a base specimen. It was noticed that, compared with steel columns for 500 kN load, the strain and buckling decreased by 13.5% and 60%, respectively for 0% basalt. The results are shown in Tables 5 and 6.
2) Now the composite columns are 25% basalt and 75% limestone, the test results show significant decrease (38% and 35%) for the strain and buckling at 600 kN load as illustrated in Tables 5 and 6.
3) In this case the three composite columns are 50% basalt and 50% limestone each, and the average results are shown in
b = basalt, L = limestone.
The strain gages were attached to the specimen as shown in
4) Three composite columns were tested with 75% basalt and 25% limestone. The average tests results for deflection are shown in
5) In the case of 100% basalt composite column, deflection decreased by 22% (
6) The results (
7) Significant reduction in strain (54%, 65% and 71%, at 200, 400 and 700 kN respectively) took place as the composite column changed from limestone to 100% basalt as in
8) Buckling (deflection) of the composite basalt columns decreased significantly (about 64%) compared with limestone composite columns. This reduction indicates that basalt composite columns are much stronger and more durable than those of limestone (
The key properties investigated in this research project included:
1) Lateral buckling conducted under axial concentrated load, three steel columns (0.08 m, 0.16 m, 1.4 m) and three composite columns for each mix percentage total of 15 columns.
2) Strain versus load.
3) Failure load for various percentages of basalt.
As the load increased gradually from 200 kN to 650 kN, the deflection at various percentages shows no significant difference, but when the load increased from 650 kN to 1050 kN, the deflection increased for the same percentage of basalt. At the same loading, the deflection decreases as the percentage of basalt increases. This indicates that the load bearing capacity of the specimens increased as the percentage of basalt increased [
The author would like to thank the Tafilah Technical University for the financial support of this research project.
It was noticed from the experimental work that the composite basalt column behaved better than limestone composite column. This improvement is relevant only to concentric axial compressive load conditions. Thus using composite basalt column rather than limestone column is highly recommended. To avoid any slip problems between steel and basalt concrete, the authors recommends future research on using mechanical stud connector to resist shear which may develop during bending. The stud should be attached to the web of the column to keep the bond in the composite section.
[
[
[