Physical properties of marine aggregates in the extraction areas in Kollafjörður, Iceland. Pétur Pétursson, PP Consult Kristinn Lind Guðmundsson, University of Iceland (MSc thesis) Erla María Hauksdóttir, Icelandic Innovation Center Margrét I. Kjartansdóttir, Icelandic Innovation Center Bryndís G. Róbertsdóttir, Icelandic National Energy Authority Presentation at the NordMin s workshop on natural construction materials November 18-19 at NGU, Trondheim Pétur Pétursson, PP Consult e-mail: petursson.p@gmail.com
Co-authors before sampling
Geological map of Iceland
Licensed extraction areas close to Reykjavik in 2009 to 2019 Total sand and gravel extraction from 1999 to 2009, thousands of m 3
Extraction areas in Kollafjordur 2005. in use not in use Reykjavik
The purpose of the project The extraction areas are licensed by the Icelandic National Energy Authority. They decided to start a research project to know more about the physical properties of the sand and gravel deposits in the licensed extraction areas in Kollafjordur. The main purpose of the research project is: 1. To establish a database covering data on physical properties of sand and gravel in the shallow waters around Iceland 2. To make a quality evaluation and classification of sand and gravel in the licensed areas a base for a common tariff 3. To make physical properties of aggregates a prior condition for decision on granting licenses in the future, i.e. for choosing extraction areas
MSc thesis at University of Iceland On behalf of the National Energy Authority Bryndís G. Róbertsdóttir has been in close contact with the Faculty of Earth Sciences at University of Iceland regarding involvement of students in practical research projects. As a result Kristinn Lind Guðmundsson wrote his MSc thesis in connection with this project under the supervision of Dr. Hreggviður Norðdahl and Pétur Pétursson.
Testing at Icelandic Innovation Center All tests were carried out at the Icelandic Innovation Center, former Building Research Institute, by the co-authors Kristinn Lind Guðmundsson, Erla María Hauksdóttir and Margrét I. Kjartansdóttir. Test results of older samples taken in 2008 by Björgun dredging company and analysed by the consulting company Mannvit were taken into account when evaluating each licensed extraction area.
Sampling Dredging vessels from the dredging company Björgun were used for sampling
Dredging in action in Kollafjörður
The material is dredged from the seabed and discharged in the hopper of the dredging vessel. There, after considerable dredging, samples were gathered. Each sample was gathered in 6 plastic bags, about 150 to 200 kg s each sample.
How does one choose exactly where to lower the pipe to take representative samples?
Extraction areas and sampling Samples marked A and B were taken by Björgun in 2008 and grading and petrographic description analysed by Mannvit. Samples 1 to 6 taken in 2011 and 2012 as a part of this project and grading, petrographic description, freezing and thawing resistance and resistance to fragmentation analysed by Innovation Center, total 38 samples from 7 areas.
Test methods EN 933-1: Determination of particle size distribution: Grading curve
Test methods EN 932-3: Procedure and terminology for simplified petrographic description
Test methods EN 1367-6: Determination of resistance to freezing and thawing in the presence of salt (NaCl) 6
Test methods EN 1097-2: Methods for the determination of resistance to fragmentation, Los Angeles test
Testing of samples from Engey extraction area License area 4
Engey grading curves
Engey petrographic classification 6,3-8 mm 8-11,2 mm 6,3-8 mm 6,3-8 mm Altered, dense basalt 6,3-8 mm 16-31,5 mm 4-11,2 mm Shell fragments Fresh, porous basalt Fresh, dense basalt Fresh, dense basalt, glassy
ENGEY Resistance to freezing and thawing Resistance to fragmentation
ENGEY EXTRACTION AREA CONCLUSION The sand and gravel deposits sampled at the Engey license area are considered to be a good aggregate for concrete and bituminous mixtures. It is relatively high in gravel and is mostly fresh basalt and fresh glassy basalt. The resistance to freezing and thawing and resistance to fragmentation is relatively good. This evaluation is made with regard to samples taken from the existing pits, but sample 4 is not a part of the evaluation as it is most likely taken outside the pit and therefore not representative.
SUMMARY OF TEST RESULTS
All grading curves
Fine and coarse grading curves excluded
Average grading curves for each extraction area
Petrographic types of all samples from Kollafjördur
Petrographic types of all samples ranked by combined fresh basalt
Fresh basalt and altered basalt plotted together Only samples from extraction pits and analysed by the same geologist
Resistance to freezing and thawing all samples tested
Resistance to freezing and thawing only samples from existing pits
Resistance to fragmentation all samples tested
Resistance to fragmentation only samples from existing pits
CONCLUSIONS 1. Engey and Saltvík extraction areas are considered of best quality Average grain size coarse highest amount of fresh basalt types the resistance to freezing and thawing and resistance to fragmentation give the best test results 2. Þerney, Lundey and Viðeyjarflak extraction areas are considered of good to medium quality slightly poorer freeze/thaw resistance than Engey and Saltvík more samples would be needed to draw a definite conclusion 3. Leiruvogur and Álfsnes extraction areas are considered of the poorest quality highest amount of altered basalt and other poor quality petrographic types of aggregates resistance to freezeing and thawing is poor and resistance to fragmentation is relatively poor
Physical properties of marine aggregates in Kollafjördur based on sampling and testing good medium poor
Origin of the marine aggregates The main conclusions of Kristinn Lind s MSc geological studies related to this project about the origin of the marine aggregates are: that most of the aggregates at the seabed of Kollafjörður do not come far away originally it is likely that the source material is local and a large part of it is formed by erosion of lava beds at surrounding islands and on land the original rock is probably lava beds, pillow lava and pillow lava fragments Samples from Álfsnes and Leiruvogur extraction areas are considerably mixed with altered basalt sediments, originated and eroded from inland, similar to that found in Leirvogstungumelar
Pillow lava and glassy pillow lava fragments at the shore near Saltvík extraction area
Sediments with some altered basalt at Leirvogstungumelar
Co-authors after a long day sampling Thank you