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Iron Ore Technical Working Group
Submission for Evaluation and
Verification
Iron Ore Fines Proctor-Fagerberg Test
“Consider the adequacy of current methods for determining
transportable moisture limit (TML) for iron ore fines and consider new
and/or amended existing methods to be included in Appendix 2 of the
IMSBC Code.”
April 2013
All participants of the TWG operate under the international and their respective national antitrust laws
and regulations. Suitable controls are in place to ensure all meetings are minuted and discussions
and material exchanged do not transgress anti-trust requirements. All participants of the Technical
Working Group have access to in-house competition law advice, operate at all times under all
applicable international and national competition laws and regulations and have been cautioned
accordingly.
Date 19-Apr-13 Page 2 of 55
Preamble
At the 17th session of the Sub-committee on Dangerous Goods, Solid Cargoes and Containers,
Member States directed the Correspondence Group (CG) on the transportation of the iron ore fines
(established at DSC 16) to continue its work with updated Terms of Reference to:
.1) consider the adequacy of current methods for determining transportable moisture limit
(TML) for iron ore fines and consider new and/or amended existing methods to be included in
appendix 2 of the IMSBC Code – to be completed by end of May 2013 (DSC 17/4/34 and
DSC 17/INF.9);
.2) consider the evaluated and verified research into Iron Ore Fines – to be completed by end
of May 2013;
.3) prepare draft individual schedule(s) for iron ore fines and any required amendments to
appendix 2, taking into account .1 and .2 above and review the existing iron ore schedule, as
necessary; and
.4) submit a report to DSC 18.
In an effort to ensure the CG’s deliberations are informed by the latest scientific insights, the three
largest iron ore producers (with the support of their respective Competent Authorities) committed to
form an Iron Ore Technical Working Group (TWG). The TWG is coordinating research efforts into the
transportation of iron ore fines to provide independently “evaluated and verified” findings that can
serve as the basis for decision making.
To this end, the TWG will produce the following reports:
• Report #1: “Terms of Reference .1” – This report assesses the adequacy of current IMSBC
Code methods for determining the Transportable Moisture Limit (TML) of Iron Ore Fines
(IOF).
• Report #2: “Marine Studies” – This document reports the characteristics of vessel motions
and forces imposed on IOF cargoes during transit; the impacts of vessel size and sea
conditions (swell, sea and wind); and, the stability of vessels in various cargo behaviour
scenarios.
• Report #3: “Routine Test Method”– Building on the outcomes of Report #1, this document
explores potential adjustments to one of the existing routine IOF test methods – or a new test
– to better reflect actual in-hold shipping conditions and observations.
• Report #4: “Reference Tests” – This report provides further evidence to substantiate the
applicability of the routine IOF test method identified in Report #3 through the material’s
performance in real-world conditions using a variety of well-established geotechnical
methods, numerical modelling and cargo observation.
• Report #5: “Final Submission” – This report will integrate the results of all of the preceding
research into a series of recommendations that can inform the deliberations of the
Correspondence Group.
Date 19-Apr-13 Page 3 of 55
The TWG have appointed external experts (Prof Kenji Ishihara, Prof Junichi Koseki and Dr Kourosh
Koushan) in the relevant disciplines to verify each of the reports. This evaluation is followed by an
independent scientific review process undertaken by Imperial College of London (Dr Stephen
Neethling, Professor Dracos Vassalos and Professor Velisa Vesovic), under the direction of the
International Group of P&I Clubs (IG). IG represents a group of industry NGOs that includes BIMCO,
Intercargo, International Chamber of Shipping and IFAN. The finalized reports are then submitted to
the CG, fulfilling the requirement for “evaluated and verified” research.
Date 19-Apr-13 Page 4 of 55
Executive summary
The Technical Working Group (TWG), comprising one Brazilian and two Australian mining companies,
had previously undertaken a literature review and conducted extensive research into the suitability of
the current methods outlined in the International Maritime Solid Bulk Cargoes Code (IMSBC) for
determining the Transportable Moisture Limit (TML) for Iron Ore Fines (IOF). Since the IOF products
being tested are both physically and metallurgically different from the metal ore concentrates and coal
products described in the IMSBC Code, the TML tests outlined are not fully applicable for the testing
of IOF.
Based on the previous results of in the TOR1 report, it was concluded that the Proctor-Fagerberg Test
(PFT) is better suited and technically more appropriate for determining the TML for IOF. The premise
of this test is that the compaction energy used will create similar densities for given moisture contents
as will be found in a ship hold. The compaction energy, applied by varying degrees of hammer weight,
drop height and number of drops per layer, is stipulated in the IMSBC Code and based on
Fagerberg’s research completed in 1965. The compaction energy used for the PFT needs to be
updated to better reflect actual in-hold shipping conditions and observations. Therefore, a study has
been undertaken to develop a modified PFT procedure using actual in-hold cargo density and
moisture content information.
The key findings of the research are:
• The Proctor-Fagerberg test is an internationally recognised test that is suitable for determining the
compaction curves of various materials, based on their degree of saturation (IMSBC Code, 2012).
• Actual ship hold observations for IOF do not match the dry density and void ratio values obtained
by using Fagerberg’s Proctor C hammer that is currently stipulated in the code.
• There are numerous methods available to determine cargo in-hold densities, such as
internationally recognised laboratory tests, laser scanning, cargo observations, Cone Penetration
Tests and Drop Tower Tests.
• It is important that the Specific Gravity (SG) is measured as accurately as possible as small
deviations in the SG value can influence the compaction curves and saturation lines determined
in the PFT. The determination of SG should be done with a recognised international or national
standard.
• It is common across all PF methods (A-E) to use twenty-five hammer drops per layer and that the
mould is filled in five distinct layers. The large number of hammer drops gives a more uniform
density in the mould that is more repeatable between tests. Energy input can be changed by
varying the weight of the hammer and the height of the drop.
Date 19-Apr-13 Page 5 of 55
• As is consistent with Fagerberg’s original work, it was found that twenty-five drops per layer using
five layers per test was most suited for IOF. This was proven using Proctor Method C and Proctor
Method D.
• The dry density and void ratio values determined from the Proctor D hammer display the closest
alignment to the dry density and void ratio values measured from actual in-hold ship conditions for
the IOF material tested in this study.
• Past studies by Fagerberg indicated that the TML is determined from the Optimum Moisture
Compaction (OMC), which occurred at approximately 75% saturation for Scandinavian ores and
concentrates. The OMC however, for the IOF tested in this study, occurs between 90-95%
saturation. It is therefore deemed that using a saturation of 80% for the determination of the TML
is suitable for IOF. This provides a larger degree of safety to what is proposed in Fagerberg’s
original work.
• Variations to the current method outlined in the IMSBC Code (i.e. changing hammer drops/layer,
hammer drop height and hammer weight) found that variable compaction energies that are
applied to the material influence the material dry density. Whilst it is possible to change multiple
parameters, changing the hammer weight alone provides conservative results for all IOF tested.
The 150 g and 15 cm drop Proctor D hammer is the most representative of actual in-hold material
cargo observations for IOF.
• It is concluded therefore, that the TML for IOF is best determined by using the PFT D method and
the moisture corresponding to the point where this compaction curve intersects the 80%
saturation line.
Date 19-Apr-13 Page 6 of 55
Table of Contents
1 Proctor-Fagerberg Review and Void Ratio Calculations. ............................................................. 11
1.1 Proctor-Fagerberg Test Review ............................................................................................ 11
1.2 Void Ratio Calculations ......................................................................................................... 16
1.3 Bulk Density Determination ................................................................................................... 17
1.3.1 Australia-A dry density determination ........................................................................... 18
1.3.2 Australia-B dry density determination ........................................................................... 21
1.3.3 Brazilian dry density determination ............................................................................... 23
1.4 Determination of Specific Gravity (SG) and the effect on TML. ............................................ 25
1.4.1 Australia –A ................................................................................................................... 25
1.4.2 Australia –B ................................................................................................................... 26
1.4.3 Brazil ............................................................................................................................. 27
2 key findings - TWG Research on Proctor-Fagerberg Test Development. .................................... 28
2.1 The Optimum Moisture Compaction (OMC) point for the IOF tested occurs between 90-95%
saturation........................................................................................................................................... 28
2.1.1 Australia -A .................................................................................................................... 29
2.1.2 Australia –B ................................................................................................................... 30
2.1.3 Brazil ............................................................................................................................. 31
2.2 Variations in applied compaction energy have a first order impact on the dry density of IOF
material.............................................................................................................................................. 32
2.2.1 Varying number of hammer drops per layer directly impacts the dry density of the IOF
material. 32
2.2.2 Varying the hammer drop height directly impacts the dry density of the IOF material. 36
2.2.3 Dry density (t/m3) vs. compaction energy (kJ/m
3) ......................................................... 39
2.3 Compaction energies generated with the Proctor C hammer for Iron Ore Fines are
excessive........................................................................................................................................... 40
2.3.1 The key findings from this test work are: ...................................................................... 41
2.3.2 Australia – A .................................................................................................................. 42
2.3.3 Australia – B .................................................................................................................. 45
2.3.4 Brazil ............................................................................................................................. 46
2.4 Proctor D precision is deemed satisfactory when a testing method is consistently applied. 47
2.5 Scalping IOF testing samples to 10 mm is recommended for assuring proper levelling of the
sample in relation to the brim of the Proctor mould. ......................................................................... 48
3 Conclusions ................................................................................................................................... 50
Appendix – A1 ....................................................................................................................................... 52
Void Ratio Calculations: .................................................................................................................... 52
Energy Calculations: ......................................................................................................................... 55
Date 19-Apr-13 Page 7 of 55
List of Figures
Figure 1: Various compaction curves using Proctor apparatus using Methods A-E (Fagerberg ,1965)
.............................................................................................................................................................. 12
Figure 2: Testing apparatus .................................................................................................................. 13
Figure 3: Compaction curves for magnetite concentrate using Proctor C and Proctor D and compared
to actual ship cargo measurements from Fagerberg, 1965 .................................................................. 14
Figure 4: PFT for an Ilmenite Concentrate demonstrating the OMC at 70% Saturation using a Proctor
C hammer.............................................................................................................................................. 15
Figure 5: Air, water and solids phase diagram ...................................................................................... 16
Figure 6: Cargo observed after loading (left) and before discharge (right) ........................................... 19
Figure 7: Quarterly dry bulk density ...................................................................................................... 21
Figure 8: Cargo density by laser scanning ............................................................................................ 22
Figure 9: Volume change / compaction due to voyage undertaken in Q13 .......................................... 22
Figure 10: Equipment used in CPT on top of the cargo ........................................................................ 24
Figure 11: Laser scan image inside a Brazilian IOF cargo hold of a Capesize Vessel ........................ 24
Figure 12: Effect of sample pulverisation on helium pycnometry ......................................................... 27
Figure 13: Effect of SG on TML ............................................................................................................ 27
Figure 14: results for Australia-A D1 sample shows the OMC exceeding 90% saturation ................... 29
Figure 15: Close-up of Figure 9 around the OMC points for Australia-A's IOF material ...................... 29
Figure 16: Australia B Product C PFT results ....................................................................................... 30
Figure 17: PFT results for Brazilian IOF material shows the OMC exceeding 90% saturation ............ 31
Figure 18: Close-up of Figure 17 around the OMC points for Brazilian IOF material ........................... 31
Figure 19: The effect on the PF plot with varying number of drops/layer using the 350 g/20 cm
hammer for Australia-A D1 ore (Proctor C) ........................................................................................... 33
Figure 20: The effect on the PF plot when with varying number of drops/layer using the 150 g/15 cm
hammer for Australia-A D1 ore (Proctor D) ........................................................................................... 34
Figure 21: Australia B, Product A: Number of hammer drops effect on dry density ............................. 34
Figure 22: Australia B, Product C: Number of hammer drops effect on dry density ............................. 35
Figure 23: Results of compaction tests on two different Brazilian IOF (Sample 1 and Sample 2) ....... 35
Figure 24: The effect on dry density by varying the number of hammer drops per layer for Australia
A’s D1 material ...................................................................................................................................... 36
Figure 25: Proctor-Fagerberg compaction curves for Australia-A D1 ore using 150 g hammer at 5cm
and 15cm drop height ........................................................................................................................... 37
Figure 26: Australia B: Increasing drop height increases dry density ................................................... 37
Figure 27: Proctor-Fagerberg compaction curves are plotted for the same sample of Brazilian IOF
using the 350 g hammer at different drop heights with 25 drops per layer ........................................... 38
Figure 28: The standard error associated with varying hammer drop height using dry density values at
the as received moisture content. The 150 g hammer with 25 drops per layer has been used with D1,
D2 and D3 material. .............................................................................................................................. 38
Figure 29: The standard error associated with varying hammer drop height using dry density values at
the “as received” moisture content. The 350 g hammer with 25 drops per layer has been used with
D1, D2 and D3 material ......................................................................................................................... 39
Figure 30: Dry Density (t/m3) vs. Compaction Energy (kJ/m3) for D1, D2 and D3 material ................. 40
Figure 31: PF plots for determination of hammer selection for D1 ore ................................................. 42
Figure 32: PF plots for determination of hammer selection for D2 ore ................................................. 43
Figure 33: PF plots for determination of hammer selection for D3 ore ................................................. 44
Figure 34: Australia B, Product C: Proctor C hammer (150 g, 15 cm drop height, 25 drops per layer)
provides compaction comparable to loading conditions ....................................................................... 45
Date 19-Apr-13 Page 8 of 55
Figure 35: Australia B, Product B: Proctor C hammer (150 g, 15 cm drop height, 25 drops per layer)
provides compaction comparable to loading conditions ....................................................................... 45
Figure 36: Bulk density compaction curve using the 350 g, 20 cm hammer (Proctor C) with 4 drops
per layer ................................................................................................................................................ 46
Figure 37: Proctor-Fagerberg plot for ‘Brazilian IOF 1’ using Proctor D ............................................... 46
Figure 38: Proctor-Fagerberg plot for ‘Brazilian IOF 2’ using Proctor D ............................................... 47
Figure 39: Comparative results of PF tests between an external laboratory and the laboratory of
Australian-A ........................................................................................................................................... 48
Figure 40: PFT precision trial for Australia B Product A ....................................................................... 48
Figure 41: Two pictures illustrating the negative impact on levelling the sample in relation to the brim
of the mould in the presence of a particle coarser than 10 mm ............................................................ 49
Date 19-Apr-13 Page 9 of 55
List of Tables
Table 1: Variation of Proctor-Fagerberg tests and compaction procedures ......................................... 12
Table 2: Cargo compaction from cargo height measurements ............................................................. 19
Table 3: Laser scanning summary of all hold results for cargo bulk density ........................................ 20
Table 4: Bulk densities determined by Drop Tower Tests .................................................................... 20
Table 5: Densities and void ratios for Brazilian IOF .............................................................................. 23
Table 6: Australia-A changes in TML with varying SG ......................................................................... 26
Table 7: Influence of different measurements techniques of density of solids on the TML for two
different Brazilian IOF samples ............................................................................................................. 28
Date 19-Apr-13 Page 10 of 55
ABBREVIATIONS
ASTM American Society for Testing and Materials
Cargo intersection The point where the cargo meets the hold wall
Cargo peak The maximum height of the cargo after loading
CPT Cone Penetration Test
Dry bulk density This is the ratio of the dried mass of the material to its volume
DWT Dead Weight Tonnage (of a vessel)
℮ Void ratio on a Proctor-Fagerberg graph
℮v Water content on a Proctor-Fagerberg graph
IMO International Maritime Organization
IMSBC Code International Maritime Solid Bulk Cargo Code
IOF Iron Ore Fines
ISO International Organization for Standardization
OMC Optimum Moisture Compaction
OMP Optimum Moisture Point
PFT Proctor-Fagerberg Test
TML Transportable Moisture Limit
TOR Terms of Reference
TWG Technical Working Group
S Saturation degree expressed in percentage
SG Specific Gravity is the ratio of the density of a substance to the density
(mass of the same unit volume) of a reference substance. It is
dimensionless. In the context of the present report, taking density of water
equal to one tonne per cubic meter, the Specific Gravity related to water
becomes numerically equal to the Density of Solids, which is expressed in
units of mass per volume, such as tonnes per cubic meter or grams per
cubic centimetre.
X + X is nominal percent moisture value to allow scalability but preserve
masking of data to fulfil internal anti-trust requirements.
Date 19-Apr-13 Page 11 of 55
1 PROCTOR-FAGERBERG REVIEW AND VOID RATIO CALCULATIONS.
1.1 Proctor-Fagerberg Test Review
The original Proctor test was developed in the early 1930’s by Ralph R Proctor, and is used
extensively in geotechnical engineering on materials such as sand, silt and clay. This test can be
performed in the laboratory to determine the Optimum Moisture Compaction (OMC) at which a given
material will be at its most dense state. The Proctor test has undergone modifications since then; and
in 1958 the test was modified to become a standard as part of the American Society for Testing and
Materials (ASTM). The ASTM D698-07 describes a standard test method for laboratory compaction
characteristics of soil using a standard effort of 600kN-m/m3.
Fagerberg investigated a modified Proctor Test (which would later become known as the Proctor-
Fagerberg Test) in his 1965 paper “Hazards of shipping granular ore concentrates – part II”. The
simple testing procedure involved compacting material inside a cylindrical mould. The material is filled
in five separate layers, each layer receiving a specified number of drops from a standard weighted
hammer which is dropped from a specified dropping height. The sample is then levelled off along the
brim. The process is repeated for incremental moisture contents until a full compaction curve is
obtained. The weight and moisture content of each test is calculated and a graphical relationship
between dry density to moisture content is plotted to establish a set of compaction curves. Fagerberg
realised that the Proctor compaction test could be useful for determining the stability of bulk cargo
ores and produced five individual tests with varying compaction energies. Materials such as bauxite,
coal and dicalcium phosphate have been tested using this method for the determination of
compaction curves. (Kruszewski, 1985). These tests and their respective variables are described in
Date 19-Apr-13 Page 12 of 55
Table 1 and show the compaction energies range from 934 kJ/m3 for the A method to 2.5 kJ/m
3 for
the E method.
Depending on the compaction energy used as a function of the testing variables, each test will
produce a different compaction curve as seen in Figure 1. Lower applied energies see the void ratios
increase as a result of less dense compaction of particles in the material.
Date 19-Apr-13 Page 13 of 55
Table 1: Variation of Proctor-Fagerberg tests and compaction procedures
Method Weight of
Hammer(g)
Height of
Drop (cm)
Number of
drops per layer
Number of layers Compaction Energy
(kJ/m3)
A 2498 30.5 25 5 934.0
B 1000 20 25 5 245.3
C 350 20 25 5 85.8
D 150 15 25 5 27.6
E 50 4 25 5 2.5
Figure 1: Various compaction curves using Proctor apparatus using Methods A-E (Fagerberg
,1965)
The energy input can be described by the following equation:
One of the key conclusions from Fagerberg was “the investigations show that the upper critical
moisture content (of a material) can be determined accurately and rapidly by compaction tests with
the Proctor apparatus”
Fagerberg performed these above tests on mineral concentrates such as magnetite, un-floated iron
ore concentrates and flotation concentrates which were sampled from the holds of 85 vessels (which
were approximately 10,000 DWT) to get representative samples. It is interesting to note that the
number of drops per layer and the number of layers stayed constant throughout Methods A-E. It was
Date 19-Apr-13 Page 14 of 55
the weight of the hammer and the height of the drop that determined the variation in compaction
energy applied to the material. The testing apparatus consists of the compaction cylinder and
compaction hammer and can be seen in Figure 2.
Figure 2: Testing apparatus
Fagerberg noted from his test work that upon analysis of the materials within the cargo hold, the
material had undergone the same degree of compaction at the middle and bottom of the cargo. Of
the 85 vessels studied, graphical results showed that it was characteristic of all compaction curves to
have the same general shape and that the minimum point on the curve is defined as the Optimum
Moisture Compaction (OMC). Characteristic of all the concentrate material that Fagerberg studied
using the Proctor C hammer, the voids at optimum compaction are filled to 70-75% by volume of
water with the balance constituting air. It is noted that to prevent large quantities of free water, the
moisture should not exceed a 70-75% saturation limit. Figure 3 is an example of a typical compaction
curve from Fagerberg’s studies whereby the OMC occurs between the 70% and 75% saturation lines.
Importantly, the compaction of a concentrate cargo under rough weather and sea conditions lies in
the area “limited by the compaction curves obtained with Proctor Method C (350 g / 20 cm drop
height) and Proctor Method D (150 g / 15 cm drop height)” as seen in Figure 3. The symbols
represent the void ratios measured at a certain height and sampling point in the cargo heap. In order
to match the compaction curve with the dry density or void ratio values obtained from in-hold cargo
measurements, Fagerberg chose the Proctor C hammer, taking into account an appropriate safety
margin. This produced an OMC between 70% and 75% saturation.
Australia-B undertook the PFT for the Proctor C Method on an Ilmenite Concentrate to replicate the
work that Fagerberg completed. As can be seen in Figure 4, the OMC occurs at 70% saturation.
Date 19-Apr-13 Page 15 of 55
Figure 3: Compaction curves for magnetite concentrate using Proctor C and Proctor D and
compared to actual ship cargo measurements from Fagerberg, 1965
Date 19-Apr-13 Page 16 of 55
Figure 4: PFT for an Ilmenite Concentrate demonstrating the OMC at 70% Saturation using a
Proctor C hammer
Using the Proctor C hammer to represent the compaction force which the materials is subject to, it
was found that the upper critical water content was indicated by the moisture at optimum compaction.
Fagerberg deemed that anything below the OMC (the upper critical moisture limit) would be safe to
ship. At this saturation level, the Transportable Moisture Limit (TML) could be determined by reading
the moisture content directly from the compaction curve. Fagerberg noted that at this saturation state,
no “disturbing water segregation” will evolve.
In light of the information above, the compaction characteristics of a material not only depend on the
amount of input energy, but also on particle mineralogy, the spectrum of particle sizes, the shape and
specific gravity. The IOF material in this Terms of Reference 2 report differs from the concentrates
that Fagerberg used in his study, as is evident by the OMC occurring between 90-95% saturation, as
previously described in the TWG’s Terms of Reference 1 Report.
Date 19-Apr-13 Page 17 of 55
1.2 Void Ratio Calculations
Ore material represents a three-phase system, consisting of solids, air and water. The volume of air,
water and solids are represented as Va, Vw and Vs respectively, whereby the total volume is VT. The
weight of air, water and solids are represented by Wa, Ww and Ws respectively, whereby the weight of
air is equal to zero. The phase diagram is represented below in Figure 5.
Figure 5: Air, water and solids phase diagram
Calculations of void ratio can be seen in the Appendix and have been used by Australia-A to
determine the void ratio that reflects iron ore fines solid density and bulk density. The void ratio equals
the ratio of SG to dry density minus 1 as given in Appendix 2 of the IMSBC Code. Determining the
void ratio of a porous solid is not straight forward and can lead to errors in SG values such that the
solid is represented as both solid and pores. Derivations of the equations below can be found in the
Appendix.
The following equation can be used to determine the void ratio on a ‘Saturation vs. Gross H2O’ plot.
The equation below can be used to determine the void ratio using PFT data.
Date 19-Apr-13 Page 18 of 55
In order to compare the PF compaction curves to dry density and void ratios for IOF in ship’s cargoes,
bulk density assessments of the ore are performed inside the cargo hold. The bulk density (t/m3) is
defined as the weight of solids, air and water in a known volume. As outlined in the sections below,
cargo observations have been undertaken by the TWG companies and include methodologies and
measurements in relation to cargo behaviour at loading and unloading.
1.3 Bulk Density Determination
The IMSBC Code states that bulk density is the weight of solids, air and water per unit volume and in
general, is expressed as kg/m3. The void spaces within the material may be filled with either air or
water (Item 1.7 Definitions, IMSBC Code). The bulk density of a solid bulk cargo determines its
stowage factor, which according to the IMSBC Code, is a figure which expresses the number of cubic
metres in which one tonne of cargo will occupy, as seen below. The stowage factor is regarded as
mandatory information that should be provided to shippers when declaring cargo. (IMSBC Code,
Section 4.3) whereby Stowage factor (expressed in m3/t) = 1 / (bulk density kg/m
3/ 1000 kg/t)
Real world bulk densities can be determined as a result of direct measurements of mass and volume.
The assessment of bulk density is routine practice in the Australian and Brazilian iron ore industries.
The average bulk density is assessed under industrial conditions, for example onboard ships, at port
stockyards and cargo spaces. Additionally, the bulk density of a material may be determined under
laboratory conditions after a certain compaction effort has taken place, which is usually confined in
three dimensions and with no tamping force.
There are internationally published standards on bulk density determination, including the circular
issued by IMO, the MSC/Circ.908, dated 4th June 1999: ‘Uniform method of measurement of the
density of bulk cargoes’. There is one internationally recognized standard for specifically assessing
bulk densities of iron ores: ISO 3852 –‘ Iron ores for blast furnace and direct reduction feedstocks –
Determination of bulk density’. Interestingly, a scrutiny of both MSC/Circ.908 and ISO 3852 reveals
that they are basically similar methods to obtain a non compacted bulk density (sometimes referred
as ‘natural’ bulk density).
That last statement becomes obvious when examining one step of the procedures described in
MSC/Circ.908: “3.2 The container should be filled with a sample of the material so that it is trimmed
level with the top of the container. The material should not be tamped.” ISO 3852 describes a
Date 19-Apr-13 Page 19 of 55
procedure in a more in-depth level of detail. This procedure involves filling a metal cylinder, called
‘small container’ (400 mm diameter and 400 mm height – approximately 0.05 m3 inner volume) with
the solid bulk cargo, as loaded, if it is to reflect as loaded conditions. That sample is levelled off along
the brim of the cylinder, and weighed. The bulk density figure results from dividing mass of sample by
its confined volume (the cylinder). The standard also prescribes a pilot-scale method variation with a
“large container” to test samples with a minimum of 10 t of mass.
In order to correlate the PF compaction curves to dry density and void ratios for IOF, bulk density
assessments of the ore are performed inside the cargo hold. As outlined in the sections below, cargo
observations have been undertaken by the TWG companies and include methodologies and
measurements in relation to cargo behaviour at loading and unloading.
The errors for the bulk density determination are due to volumetric survey and conveyor weightometer
measurements. For volumetric measurements the errors range from ~15m3 per hold, equating to
0.5% (Aust A), ~ 50m3 (Aust B) for approx 7000m
3 survey of a single capesize vessel hold; ie <0.75%
(absolute) in volume. The weightometer error is about 0.25% (absolute). Moisture determination by
ISO3087 has a precision about 0.22% (absolute) corresponding to a 95% confidence ~0.45%
(absolute) for the moisture result. Combining these yields a 95% confidence limit for the dry density of
<1.5% (absolute). Ie for dry density of 2.2t/m3 error is +/- 0.03t/m
3.
1.3.1 Australia-A dry density determination
Over 100 observations of the behaviour of three different IOF materials have been studied by
Australia-A whereby the voyage route typically was from Western Australia to China. The cargo
appearance was visually observed and recorded before loading and after discharge and the height of
the cargo at the hold wall and hatch covers were taken (Figure 6). From these measurements, an
estimation of volume change / reduction (due mainly to compaction, material re-distribution) as a
percentage was made and the results from all 100+ observations can be seen in
Table 2. There was no correlation found between volume change and sea conditioning experienced
during the voyage.
Date 19-Apr-13 Page 20 of 55
Figure 6: Cargo observed after loading (left) and before discharge (right)
Table 2: Cargo compaction from cargo height measurements
Hold Wall - Cargo Intersection Cargo Peak
Compaction % Hold 1 Hold 9 Hold 1 Hold 9
Average 1.9 0.7 3.8 2.6
Maximum 10.2 3.2 10.3 7.3
Minimum 0.0 0.0 0.5 0.1
Additionally, a Leica HDS6200 laser scanner was accurately located inside the ship hold to map the
cargo surface and to provide a profile of the cargo after loading and before discharge. By using
surface profiles to determine the volume of cargo, this allowed for estimations of bulk density and the
degree in which it changed with time, as the mass of ore in the hold is already known from load cells
on the ship conveyor. Validation of volume measurements are confirmed using standard ISO3852-
2007 for uncompacted density tests and standard AS1141.4-1996 for compacted density
determination. The laser scanning results for cargo bulk densities are listed in Table 3.
Date 19-Apr-13 Page 21 of 55
Table 3: Laser scanning summary of all hold results for cargo bulk density
Iron Ore Fines
D1
Iron Ore Fines
D2
Iron Ore Fines
D3
Laser
Scanning
Initial Bulk
Density
(t/m³)
Final
Bulk
Density
(t/m³)
Initial Bulk
Density
(t/m³)
Final
Bulk
Density
(t/m³)
Initial Bulk
Density
(t/m³)
Final
Bulk
Density
(t/m³)
Average 2.25 2.30 2.00 2.05 1.95 2.0
Maximum 2.28 2.36 2.10 2.16 2.06 2.10
Minimum 2.16 2.20 1.96 2.01 1.90 1.93
NB. The average, maximum and minimum values are the average, maximum and minimum of all voyages, and do not
necessarily correspond with each other.
Additionally, drop tower tests were undertaken to determine the possible range of bulk densities
achievable after loading in the hold and to verify the values obtained by laser scanning. The test
involved dropping 20 kg of IOF sample at a given moisture content from a predetermined height into a
catching can of known volume. After levelling the material, the weight is taken to estimate bulk
density. Drop heights that simulate the materials path from the shiploader into the vessels cargo hold
(20 m) were performed at moistures in the range of cargo actual shipping moistures. the largest
compaction process is due to initial loading of the cargo (drop from 20+m at 12000tph). Laser
scanning of partial filled holds produced the same result as fully filled holds, confirming the loading
process governs the compaction.
Table 4 provides the results and show for the three Australia-A IOF products, the drop tower results
for bulk density are the same or slightly greater than those determined by laser scanning. This
indicates that the largest compaction process is due to initial loading of the cargo (drop from 20+m at
12000tph). Laser scanning of partial filled holds produced the same result as fully filled holds,
confirming the loading process governs the compaction.
Table 4: Bulk densities determined by Drop Tower Tests
D1 D2 D3
Average Bulk Density
(t/m3)
2.25 2.14 2.09
Date 19-Apr-13 Page 22 of 55
1.3.2 Australia-B dry density determination
Australia B conducts regular density determinations on its IOF products. The routine quarterly bulk
density determinations are based on determination of loose bulk density and firm packed density
measurements. Figure 7 shows the routine dry bulk density for Australia B products, whereby the bulk
density variation for all products is less than 0.1 t/m3.
Figure 7: Quarterly dry bulk density
As part of the cargo stability measurements, laser scanning surveys of cargo holds were undertaken
at loading and discharge ports. The Terrestrial Laser Scanning of each hold involved two instrument
setups in positions that minimised the data shadows created by the various peaks and troughs of the
product surface. The two setup locations where on alternate sides of the hold, the bow and the stern,
with one setup placed towards the port side, the other to the starboard. A high-resolution 360° scan
was performed at each setup, producing three-dimensional point spacing of 6 mm by 6 mm at 10 m.
There were two different scanners used for the project. All scans undertaken at load port were done
using a Zoller and Fröhlich Imager 5010, whereas a Leica HDS6000 was used at the discharge port.
Conformance tests to ensure that the datasets from the two different scanners were comparable were
conducted. Cloud to cloud disparities were <2 mm at 10 m, well within instrument specifications.
Altogether more than twenty one holds were scanned, of which seven were commissioning related
and only conducted at the discharge port. This density data is shown in Figure 8 and corresponds to
Quarter 13 from Figure 7.
Date 19-Apr-13 Page 23 of 55
Figure 8: Cargo density by laser scanning
There is good agreement of the bulk density data from routine measurements and the laser scanning
measurements for Quarter 13 from Figure 7 and the average for Product A and Product C in Figure 8.
The volume change for all surveyed holds is graphed in Figure 9. The measured volume change is
consistent within each product surveyed. Regardless of product, the volume change during the
journey is much less than 5%.
Figure 9: Volume change / compaction due to voyage undertaken in Q13
When the new volume is translated to a product density change for Product A the dry density increase
is about 0.08 t/m3 as per the volume change, 3%. For Product C the dry density increase is less than
0.05 t/m3 or 1%.
The moisture determination for conversion to dry bulk density is by ISO3087.
Date 19-Apr-13 Page 24 of 55
1.3.3 Brazilian dry density determination
Likewise to Australia-A testing methodology, ISO3852 is employed to determine the bulk density of
Brazilian IOF material. As is routine practice, the bulk density is assessed under industrial conditions
(i.e. onboard ships, port stockpiles, cargo spaces) and assessed under laboratory scale. Table 5
below provides data that compares real world bulk densities (i.e. under compaction) to bulk densities
used according to ISO3852 for four samples of Brazilian IOF. Further results of 147 other IOF
materials validated that the real-world dry bulk densities are between 2246 kg/m³ and 2723 kg/m³.
Table 5: Densities and void ratios for Brazilian IOF
The Cone Penetration Test (CPT) method can be employed on board vessels to determine the cargo
density profile of the material loaded. These tests are performed using a cylindrical penetrometer with
a conical tip that penetrates the stow in the cargo space at a constant rate. Here, the forces of the
cone and the friction sleeve are measured. The equipment is shown in Figure 10. Results for the CPT
work will be discussed in TWG Report 4. In order to assist in the CPT findings and validate the
compaction tests inside the cargo holds, laser scanning was also employed, as seen in Figure 11:
Laser scan image inside a Brazilian IOF cargo hold of a Capesize Vessel.
Date 19-Apr-13 Page 25 of 55
Figure 10: Equipment used in CPT on top of the cargo
Figure 11: Laser scan image inside a Brazilian IOF cargo hold of a Capesize Vessel
Date 19-Apr-13 Page 26 of 55
1.4 Determination of Specific Gravity (SG) and the effect on TML.
As previously outlined in Section 1.2, SG and solids dry density are critical in determining an accurate
void ratio value. It is important that the SG is measured as accurately as possible, as small deviations
in the SG value can influence the compaction curves and saturation lines determined in the PFT.
Techniques such as the use of water displacement methods, glass pycnometers and helium
pycnometers are readily employed in the minerals industry. The determination of SG should be done
with a recognised international or national standard.
The sections below give an indication as to how the TML changes significantly with increments in the
SG value for each of the TWG members. The Proctor C method has been used to determine the
TML.
1.4.1 Australia –A
As outlined in Section 1.2, the void ratio can be calculated by the following equation.
SG affects the void ratio and hence will alter the compaction curve and saturation lines.
According to this, if SG increases, the void ratio increases and the PF curve shifts upwards. The
negative gradient of the curve (occurring before the OMC) when shifted upwards causes the intercept
with the saturation line to occur at a higher water content. Therefore, the TML increases.
The data represented in Table 6 below give an insight into how the TML changes for three samples of
Australian-A iron ore (D1, D2 and D3) with small changes in SG. Testing has been done in
accordance with AS1289.3.5.1.
Date 19-Apr-13 Page 27 of 55
Table 6: Australia-A changes in TML with varying SG
Sample SG
(t/m3)
TML (%) TML
Difference
(%)
D1
4.4 X+6.3 -
4.6 X+6.5 0.2
4.8 X+6.6 0.3
5.0 X+6.75 0.45
D2
3.9 X+6.15 -
4.1 X+6.55 0.4
4.3 X+6.85 0.7
4.5 X+7.15 1.0
D3
3.9 X+5.7 -
4.1 X+6.15 0.45
4.3 X+6.5 0.8
4.5 X+6.75 1.05
1.4.2 Australia –B
For the PFT investigation the SG determination method has been according to AS 1289.3.5.1. A
series of replicate samples were tested to investigate the effect of particle size on the pycnometer
test. Figure 12 shows that if the sample is pulverised to 150 micron there is no difference to treating
the sample as received.
Date 19-Apr-13 Page 28 of 55
Figure 12: Effect of sample pulverisation on helium pycnometry
The SG determination is a critical part of the PFT. A key learning from developing the PFT method
and assessing results from external laboratories was around the SG determination. In particular, if a
TML curve is completed and the curve shows more than 100% saturation more it was due to an
inconsistent SG result. Figure 13 shows the variation of TML with SG.
Figure 13: Effect of SG on TML
1.4.3 Brazil
Brazil has employed two methods to determine the SG value of their IOF material, water
displacement in a glass cylinder and a high precision helium pycnometer. Two different samples of
Date 19-Apr-13 Page 29 of 55
Brazilian IOF were used (Sample 1 and Sample 2). The results can be seen below in Table 7 and
they show that the water displacement method underestimates the SG compared to the helium
pycnometry, resulting in a lower TML value.
Table 7: Influence of different measurements techniques of density of solids on the TML for
two different Brazilian IOF samples
Brazilian IOF
Glass Water Displacement
SG (t/m3)
TML (%) Helium Pycnometer
SG (t/m3)
TML (%) SG Absolute
Difference SG (t/m
3)
TML (%) Absolute
Difference
Sample 1 4.30 X+1 4.76 X+1.7 0.46 0.7
Sample 1 Duplicate
4.40 X+1.1 4.76 X+1.7 0.36 0.6
Sample 2 4.47 X+2.1 4.91 X+2.6 0.44 0.6
Sample 2 Duplicate
4.50 X+2.1 4.91 X+2.5 0.41 0.4
2 KEY FINDINGS - TWG RESEARCH ON PROCTOR-FAGERBERG TEST DEVELOPMENT.
2.1 The Optimum Moisture Compaction (OMC) point for the IOF
tested occurs between 90-95% saturation.
The key findings from this test work are:
• Research into the IOF material from Australia-A (Figure 14 and Figure 15), Australia-B
(Figure 16) and Brazil (Figure 17 and Figure 18) revealed that the OMC point occurs
between 90-95% saturation when compared with Fagerberg’s original work; whereby OMC
occurs between 70-75% saturation for mineral concentrates.
• The various compaction curves represented in the plots below are due to changing energy
inputs by varying parameters such as hammer weight, hammer drops and drop height.
Lower energy inputs results in an upwards shift of the compaction curve as the material is
less dense and hence has a higher void ratio.
Date 19-Apr-13 Page 30 of 55
2.1.1 Australia -A
Figure 14: results for Australia-A D1 sample shows the OMC exceeding 90% saturation
Figure 15: Close-up of Figure 9 around the OMC points for Australia-A's IOF material
Date 19-Apr-13 Page 32 of 55
2.1.3 Brazil
Figure 17: PFT results for Brazilian IOF material shows the OMC exceeding 90% saturation
Figure 18: Close-up of Figure 17 around the OMC points for Brazilian IOF material
Date 19-Apr-13 Page 33 of 55
2.2 Variations in applied compaction energy have a first order
impact on the dry density of IOF material.
As previously outlined in Section 1, Fagerberg developed five testing methods (A-E) that represented
different forms of compaction energy being applied to the sample in the Proctor mould. Each form of
compaction energy produces a different compaction curve. A study was undertaken to investigate the
following testing variables and their impact on the dry density of IOF.
• Number of hammer drops per layer
o This study was performed to investigate the effects of changing the number of drops
per layer and its associated error with respect to the repeatability of dry density tests.
Additionally, it is to validate the use of 25 drops per layer, as Fagerberg had originally
outlined in his original research.
• Height of hammer drop (cm)
o This study was performed to investigate the effects of changing hammer drop height
and its associated error with respect to the repeatability of dry density tests.
Additionally, it is to validate the use of the drop heights associated with the Proctor C
and Proctor D hammers, which are 20 cm and 15 cm respectively.
• Weight of hammer (g)
o Proctor-Fagerberg tests using the Proctor C and Proctor D hammers were performed
on the IOF material to align with in-hold cargo measurements (eg. bulk density and
void ratio).
Three different material types (D1, D2 and D3) from Australia-A were tested in this study.
Two different material types (A and C) from Australia – B were tested.
Two material types (Sample 1 and Sample 2) of Brazilian IOF were used.
2.2.1 Varying number of hammer drops per layer directly impacts the dry
density of the IOF material.
The key findings from this test work are:
• Increasing the number of drops per layer to 35 evidently results in higher compaction
energies when compared with 5 drops per layer.
• PF plots for Australia-A (Figure 19 and Figure 20) indicate dry density increases with
increasing the number of drops per layer.
Date 19-Apr-13 Page 34 of 55
• Australia B results show that dry density increases with the number of hammer drops per
layer (Figure 21 and Figure 22).
• Results from two different Brazilian IOF samples (Sample 1 and Sample 2) indicate a similar
trend such that dry bulk density increases linearly with the logarithm of compaction energy
(Figure 23).
• It is evident from
Figure 24 that when comparing the number of drops per layer with the dry density of the
material, there is an asymptotic relationship present. The asymptotic part of the curve begins
to develop only after about 20 drops per layer
• Therefore, in the interest of minimizing variability in results, it is optional to use between 15
and 25 drops per layer for a PFT. Based on our analysis the number of drops suggest by
Fagerberg (25 drops) is adequate.
Date 19-Apr-13 Page 35 of 55
Figure 19: The effect on the PF plot with varying number of drops/layer using the 350 g/20 cm
hammer for Australia-A D1 ore (Proctor C)
Figure 20: The effect on the PF plot when with varying number of drops/layer using the 150
g/15 cm hammer for Australia-A D1 ore (Proctor D)
Date 19-Apr-13 Page 36 of 55
Figure 21: Australia B, Product A: Number of hammer drops effect on dry density
Figure 22: Australia B, Product C: Number of hammer drops effect on dry density
Date 19-Apr-13 Page 37 of 55
Figure 23: Results of compaction tests on two different Brazilian IOF (Sample 1 and Sample 2)
Figure 24: The effect on dry density by varying the number of hammer drops per layer
for Australia A’s D1 material
Date 19-Apr-13 Page 38 of 55
2.2.2 Varying the hammer drop height directly impacts the dry density of
the IOF material.
• The key findings from this test work are: Increasing the drop height results in higher bulk
density values when compared with smaller drop heights for Australian and Brazilian IOF
material (Figure 25, Figure 26 and Figure 27).
• The 150 g and 350 g hammer showed a decreasing standard error with an increase of drop
height across all material types for Australia-A (Figure 28 and Figure 29). Note that the high
errors associated with the 350 g hammer were due to material properties.
• It is recommended to use a drop height of 15 cm or greater with 25 drops per layer and 5
layers per PFT. This supports all of Fagerberg’s original methods (Figure 28 and Figure 29).
Figure 25: Proctor-Fagerberg compaction curves for Australia-A D1 ore using 150 g hammer at
5cm and 15cm drop height
Date 19-Apr-13 Page 39 of 55
Figure 26: Australia B: Increasing drop height increases dry density
Figure 27: Proctor-Fagerberg compaction curves are plotted for the same sample of Brazilian
IOF using the 350 g hammer at different drop heights with 25 drops per layer
Date 19-Apr-13 Page 40 of 55
Figure 28: The standard error associated with varying hammer drop height using dry density
values at the as received moisture content. The 150 g hammer with 25 drops per layer
has been used with D1, D2 and D3 material.
Figure 29: The standard error associated with varying hammer drop height using dry density
values at the “as received” moisture content. The 350 g hammer with 25 drops per
layer has been used with D1, D2 and D3 material
Date 19-Apr-13 Page 41 of 55
2.2.3 Dry density (t/m3) vs. compaction energy (kJ/m3)
The following plot (Figure 30) represents the results from all the tests performed by Australia-A to
investigate the effect of compaction energy on the dry density of the D1, D2 and D3 material. It was
found that a logarithmic increase in compaction energy results in a linear increase in dry density.
These results validate that any form of compaction energy (e. g., varying hammer weight, drop height
or number of drops) has a direct impact on the dry density of the material and that each method was
equally as efficient in compacting the sample and increasing the dry density.
Figure 30: Dry Density (t/m3) vs. Compaction Energy (kJ/m3) for D1, D2 and D3 material
2.3 Compaction energies generated with the Proctor C hammer for
Iron Ore Fines are excessive.
Upon analysis of the material properties and cargo observations for IOF, it was found that the dry
density and void ratio values measured do not directly match the density and void ratio values
obtained by using the Proctor C hammer which is currently stipulated in the code. The Proctor C
hammer overestimates the dry density and underestimates the void ratio for IOF.
Date 19-Apr-13 Page 42 of 55
IOF material bulk density values have been used to calculate the corresponding dry density and
resultant void ratio for a particular material. It is important that the compaction curves relates to the
void ratio values, as Fagerberg previously found. For the IOF material tested, this can be achieved by
varying the hammer weight, whilst maintaining all other variables constant.
Date 19-Apr-13 Page 43 of 55
2.3.1 The key findings from this test work are:
- Using a lighter hammer weight increases the void ratio whereby a less dense compaction is
obtained. The curve now aligns closer with the given bulk density values from actual in-hold
cargo measurements for Australia A’s IOF material (Figure 31, Figure 32 and Figure 33).
- To be comparable with the loaded cargo conditions, as intended by the IMSBC Code,
Australia-B’s IOF material required a change in the compaction energy. To ensure consistent
application of the compaction effort a simple change from the Proctor C hammer (350 g, 20
cm drop height) to the Proctor D hammer (150 g, 15 cm drop height) was made. The result of
this change was a decrease in compaction. The resulting dry density (and void ratio) in the PF
test at the “as shipped” gross moisture (the moisture of the material at the time of loading),
being calibrated to the loaded dry density and void ratio measured in the ships (Figure 34 and
Figure 35).
- It was found that the dry bulk density of Brazilian IOF material can be matched by adjusting
the compaction energy by varying the number of hammer drops per layer using the Proctor C
hammer (Figure 36). Despite this, it is debateable as to whether 4 drops per layer is adequate
to comply with the IMSBC Code (Section 1.3.4.1) that states the material “is (to be) tamped
uniformly over the surface of the increment”. Additionally, 4 drops per layer only applies little
compaction (14 kJ/m3) to the material and does not allow for a sufficient safety margin with
respect to the in-hold dry bulk density specified. Therefore, plots have been provided using
the Proctor D hammer in accordance with the Fagerberg’s testing methods (Figure 37 and
Figure 38).
- The Proctor D hammer ( 150 g / 15 cm drop height with 25 drops per layer and 5 layers per
test) is representative of the given bulk density for all the IOF material tested in this study.
- The average bulk density is a practical and effective way to describe IOF cargo loading
conditions and it is required to be stated on the shipper’s cargo declaration as per section 4.2
of the IMSBC Code.
- Drop tower results align with the average of the measured cargo bulk densities, indicating that
the average bulk density of the cargo is governed by the loading process.
Date 19-Apr-13 Page 44 of 55
2.3.2 Australia – A
Figure 31: PF plots for determination of hammer selection for D1 ore
Date 19-Apr-13 Page 47 of 55
2.3.3 Australia – B
Figure 34: Australia B, Product C: Proctor C hammer (150 g, 15 cm drop height, 25 drops per
layer) provides compaction comparable to loading conditions
Figure 35: Australia B, Product B: Proctor C hammer (150 g, 15 cm drop height, 25 drops per
layer) provides compaction comparable to loading conditions
Date 19-Apr-13 Page 48 of 55
2.3.4 Brazil
Figure 36: Bulk density compaction curve using the 350 g, 20 cm hammer (Proctor C) with 4
drops per layer
0,4
0,5
0,6
0,7
0,8
0,9
1,0
1,1
1,2
X + 1 X + 2 X + 3 X + 4 X + 5 X + 6 X + 7 X + 8 X + 9 X + 10
Gross Moisture Content (%)
Vo
id R
ati
o (
e)
100% Saturation
Brazilian IOF 1 P/F-'D' 150 g
hammer
As loaded
As shipped conditions
Figure 37: Proctor-Fagerberg plot for ‘Brazilian IOF 1’ using Proctor D
Date 19-Apr-13 Page 49 of 55
0,4
0,5
0,6
0,7
0,8
0,9
1,0
1,1
1,2
X + 1 X + 2 X + 3 X + 4 X + 5 X + 6 X + 7 X + 8 X + 9 X + 10
Gross Moisture Content (%)
Vo
id R
ati
o (
e)
100% Saturation
Brazil ian IOF 2 P/F-'D' 150 g
hammer
As loaded
As shipped conditions
Figure 38: Proctor-Fagerberg plot for ‘Brazilian IOF 2’ using Proctor D
2.4 Proctor D precision is deemed satisfactory when a testing
method is consistently applied.
As was previously discussed in the TOR1 report, the consistent application of the PFT method yields
comparable results when compared with external labs. Figure 39 indicates minimal difference
between internal and external labs when using Australia-A’s IOF material with the application of the
Proctor D hammer.
Date 19-Apr-13 Page 50 of 55
Figure 39: Comparative results of PF tests between an external laboratory and the laboratory
of Australian-A
For twelve replicate samples of Australia B’s Product A, a precision of less than 0.2% for the TML
result was obtained for the PFT, Figure 40.
Figure 40: PFT precision trial for Australia B Product A
It can be shown that there is sufficient safety factor associated with the TML value to account for
uncertainty/variability in both the sampling and testing procedure. The 0.2% precision for the TML
obtained is one standard deviation. The 95% confidence interval is therefore +/-0.4 This confidence
interval relates to the TML / moisture content and not necessarily the saturation.
2.5 Scalping IOF testing samples to 10 mm is recommended for assuring proper levelling of the sample in relation to the brim of the Proctor mould.
Given the nature of the single effort dynamic compaction tests per layer or material in the mould, it is
strongly advisable to scalp the sample if particles coarser than 10 mm are present. In Brazilian IOF
Date 19-Apr-13 Page 51 of 55
material, there are occasions where there is a small percentage by weight (typically <5%) of particles
over 10 mm. These larger particles are problematic for proper levelling of the top layer in the mould
and impact the validity of the test. Therefore, by eliminating these particles that are larger than 10
mm, adequate levelling of the sample is obtained. Considering that IOF are nominally finer than 10
mm, the elimination of coarse particles from the test portion should be regarded more as a protection
scalp than a sample grading. In practical terms, the volume and mass readings will be facilitated and
a minimum of 95% of the particles will be effectively assessed inside the mould. Figure 41 illustrates
the negative impact caused by the presence of particles coarser than 10 mm.
The elimination of coarse particles prior to the execution of compaction tests is a practice found in
reputable standards. ASTM D698 Standard Test Methods for Laboratory Compaction Characteristics
of Soil Using Standard Effort (12 400 ft-lbf/ft3 (600 kN-m/m
3)), for instance, establishes 9.5 mm as the
maximum particle size allowed in a 4-inch diameter mould similar to the IMSBC Code Proctor-
Fagerberg recommended mould.
Figure 41: Two pictures illustrating the negative impact on levelling the sample in relation to
the brim of the mould in the presence of a particle coarser than 10 mm
Date 19-Apr-13 Page 52 of 55
3 CONCLUSIONS
• There are numerous methods available to determine cargo in-hold densities, such as
internationally recognised laboratory tests, laser scanning, cargo observations, Cone
Penetration Tests and Drop Tower Tests.
• It is important that the SG is calculated as accurately as possible as small deviations in the
SG value can influence the compaction curves and saturation lines determined in the PFT.
The determination of SG should be done with a recognised international or national standard.
• For all IOF tested, the OMC point exceeds 90% saturation. According to Fagerberg’s
literature, the TML can be taken by using the OMC less a nominal safety factor. By applying
this approach to this method for IOF, the TML can be determined by using the point at which
the compaction curve crosses S=80%.
o Proctor C OMC mineral concentrates 70-75% saturation with TML at 70% saturation
(~5% safety margin) currently accepted by IMO.
o Proctor D OMC IOF 90-95% saturation with TML at 80% saturation (10-15% safety
margin, including sampling and experimental variability)
• The Proctor C hammer, as outlined in the IMSBC Code, overestimates the actual cargo dry
density (t/m3) and underestimates the void ratio for all IOF tested. According to Fagerberg’s
literature, the specific compaction curve is therefore not representative of the material tested.
• Variations to the current method outlined in the IMSBC Code (i.e. changing hammer
drops/layer, hammer drop height and hammer weight) found that variable compaction
energies that are applied to the material influence the material dry density. Whilst it is possible
to change multiple parameters, changing the hammer weight alone provides conservative
results for all IOF tested. The 150 g and 15 cm drop Proctor D hammer is the most
representative of actual in-hold material cargo observations for IOF.
• It is concluded therefore, that the TML for IOF is best determined by using the PFT D method
and the moisture corresponding to the point where this compaction curve intersects the 80%
saturation line.
Date 19-Apr-13 Page 53 of 55
REFERENCES
ASTM D698 Standard Test Methods for Laboratory Compaction Characteristics of Soil Using
Standard Effort (12 400 ft-lbf/ft3 (600 kN-m/m3)), 2007. Current edition approved April 15, 2007.
Published July 2007. American Society for Testing Materials, West Conshohocken, PA 19428-
2959, United States of America.
Circular MSC/Circ.908: Uniform method of measurement of the density of bulk cargoes.
International Maritime Organization – IMO. London, 4th of June, 1999.
Fagerberg, B. and Stavang, A., (1971). Determination Of Critical Moisture Contents In Ore
Concentrates Carried In Cargo Vessels, In Proceedings of 1st International Symposium on
Transport and Handling of Minerals, Vancouver. (Kirshenbaum, N.W. and Argall, G.O., Eds). San
Francisco: Miller Freeman Publications, 1971, 174-85.
Fagerberg, B., (1965a). Hazards Of Shipping Granular Ore Concentrates Canadian Mining
Journal, 856, July, pp 53-57.
Fagerberg, B., (1965b). Hazards Of Shipping Granular Ore Concentrates -Parts II. Canadian
Mining Journal, 856, Aug, pp 81-86.
ISO 3852 Iron ores for blast furnace and direct reduction feedstocks – Determination of bulk
density. International Organization for Standardization – ISO. Third edition 2007-09-01.
Date 19-Apr-13 Page 54 of 55
APPENDIX
APPENDIX – A1
Void Ratio Calculations:
In order to determine the void ratio (e) for saturation lines on a ‘void ratio vs
gross plot:
Date 19-Apr-13 Page 56 of 56
Alternative Calculations
Refer to background information in Section 2.
Input data needed = Gross Water Content (GWC) and Bulk Density (t/m3)
In order to find the total volume of the material, the bulk density value is needed: