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

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