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POTENTIALS FOR REDUCTION OF THE
CARBON FOOTPRINT OF CONCRETE:
Case study of copper slag in concrete
production.
H.C. Uzoegbo
University of the Witwatersrand
South Africa
Cement and Concrete related Issues for the African Market
INTRODUCTION
Copper slag is a waste material produced either by
hydrometallurgical or pyrometallurgical production
of copper from copper ores. a primary source of
pollution and environmental degradation
US, produced 4 million tonnes and in
Japan,
about 2 million tonnes per year. Approximately 360 000,
244 000 and 60 000 tonnes of copper slag are produced
in Iran, Brazil and Oman
INTRODUCTION
Zambia is African largest producer of copper,
generating 3.3% of the world’s copper and is
ranked seventh in the world for copper production
(Global business report 2012)
The Democratic Republic of Congo is potentially
one of the richest mining countries in Africa. Most
of DRC copper mining activities are concentrated
in the southern and eastern parts of the country (
Ndala 2011)
Palabora Company is South Africa's only producer
of refined copper producing about 80,000 tonnes
of refined copper per year. The company
produces about 200 000 tones (200kt) of slag
annually ( Palabora 2011)
Major copper reserves in the
world
Source: http://www.tcemco.com/images/CopperBelt.jpg
Copper belt in Southern Africa
INTRODUCTION
Current management options for copper slag
includes
Recycling and recovering of the Copper
metal
Production of value added products
And disposal in slag tailing dams or
stockpiles (Khazandi and Behnood
2009)
But the deposit of slag in controlled landfills
is not the best management option due to
environmental problems, high cost and lack
of land area (Khazandi and Behnood 2009)
Stock pile of copper slag in Lubumbashi DRC
Heap of Slag tailing in Panda City, DRC
Katamanda River and Slag Heap adjacent to a
Farm Plantation in DRC
Metallic trace elements such as Cu, Co, Cd, Pb,
and Zn are dispersed into the Katamanda River
Literature Review
Copper slag as cement replacement
Several Studies have been reported on the
hydration reactions (Mobasher & Devaguptapu
2000) and pozzolanic properties (Arino &
Mobasher 1999) of copper slag up to 15% by
weight replacement for Ordinary Portland
cement.
The conclusion made was, the use of ground
copper slag increased the strength of concrete
significantly beyond 91 days as long as rapid
strength gain is not a major design constraint
Copper slag as sand replacement
The use of copper slag as sand substitution
improves the strength and durability characteristics
of high strength concrete up to 50% replacement
level (Al-Jabri et al., 2009), increased the
compressive and flexural strength of pavement
grade concretes 20% higher than conventional
cement concretes of the same grade up to 40%
replacement level (Wu et al., 1999).
The results of compressive, split tensile strength
test investigated by Brindha D. et al., (2010) shows
that, the strength of concrete increases with
respect to the percentage of slag added by weight
of fine aggregate up to 40% additions and 15% of
cement replacement
Experimental Materials
Ordinary Portland cement from Pretoria Portland Cement (PPC) was used for this research study.
Coarse aggregates of sizes between 18-20mm size and fine aggregates between 8-10mm were used. The fine aggregates used for this work was crushed granite and the properties of the cement conformed as per BS EN 197-1:2000,
The copper slag used in this work was brought from the Katanga Copper slag, Democratic Republic of Congo. The physical appearance of the copper slag is black, glassy and granular in nature with similar
particle size range like sand.
Physical properties and chemical
composition
The specific gravity, water absorption and
density of copper slag and sand were
determined in accordance with ASTM C128
The copper slag was pulverise and sieve
through 0.075 micron sieve opening for setting
time and cement replacements
The initial and final setting time measurements
was performed using the Manual Vicat
apparatus as per EN 196-3:2005
Chemical analyses of OPC and the copper slag
were analysed using the XRF technique
Characteristics strength procedure
A series of concrete mixtures were cast in cubic
moulds of size nominal size 100 mm with different
proportions of pulverised copper slag ranging from
0%, 2.5%, 5%, 10% and 15% replacing Portland
cement.
Activation of pozzolanic reactions of the pulverized
copper slag using 1.5% hydrated lime by weight of
Ordinary Portland cement.
The slump of the fresh concrete was determined as
par SANS 5862-1
The mixes were compacted using a vibrating table
and demoulded after 24h, moist-cured in a water
tank at temperature of 20±1ºC and tested at the
required curing age.
Results and Discussion
In comparison with the chemical composition of natural pozzolans of ASTM C618-99, the summation of the three oxides (silica, alumina and iron oxide) in copper slag was nearly 72%,
i.e. SiO2 + Al2O3 + Fe2O3 > 70% requirement for Class N raw and calcined natural
pozzolans In assessment of the hydraulic properties of slag,
according to SANS 55167-1:2011. The result for Copper slag is approximately 0.5% which is less than the requirement to be used as constituent for cement.
i.e. (CaO + MgO)/SiO2 < 1 which is less than slag requirement to be used as
a constituent for cement in accordance to SANS 55167-1:2011
Physical Properties
Test Type Material
Sand Copper
slag
Stone
Specific gravity 2.65 3.12 -
Fineness Modulus 2.98 3.40 -
Water Absorption (%) 3.64 1.95 -
Moisture content (%) 0.54 0.05% 0.11%
Density(kg/m3) 1550 1640 1650
Uniformity Coefficient (Cu) 5.45 3.0 -
-
Undetected Major elements
Comparative sieve analysis
Sieve analysis
0.00
20.00
40.00
60.00
80.00
100.00
0.01 0.1 1 10 100
% P
assin
g
Sieve size (mm)
Stone
Sand
CuSlag
Setting Time
Mix design
Initial
setting
time (min)
Final setting
time
(min)
Delayed
in initial
setting time
(min)
Delayed
in final setting
time
(min)
0% Replacement
(control)
207 270 - -
2.5% Replacement 333 402 126 132
5% Replacement 355 436 148 166
10% Replacement 385 480 178 210
15 % Replacement 412 512 205 242
This observation could be attributed to delayed hydration
induced by the heavy ions contained in the copper slag. This
postulation is supported by Hashem et al., (2011) according to
the authors the presence of Cu (II) ions retards cement
hydration.
Slump test results
7 and 28 day strength results
60 and 90 day strengths
Strength predictions by regression
analysis
Rate of change in compr strength
Rate of change in compr strength
Cu slag as aggt
Chavan, et al, International Journal of Advanced
Engineering Research and Studies
E-ISSN2249–8974
PERFORMANCE OF COPPER SLAG ON
STRENGTH PROPERTIES AS PARTIAL REPLACE
OF FINE AGGREGATE IN CONCRETE MIX
DESIGN R R Chavan*1 & D B Kulkarni2
Cu slag as fine aggt replacement
THANK YOU