CONFIDENTIAL THE IMPACT OF SUBSTANDARD AND INCONSISTENT AGGREGATES ON THE READYMIX PRODUCER Author: Matthew Barker| Date: 22 April 2016

CONSISTENCY  All manufacturing processes depend on consistency to quality control and cost their products.  For the readymix industry: aggregates are their biggest source of inconsistency.  Admixtures and cement work on less than 2% variance  Cement plants have huge stock piles that are constantly being mixed  I challenge any of you here to go back to your sand grading files and just look at the changes in the Fineness Modulus F.M.  A change from 2.7 to 2.8 can mean as much as 10 litres of water  Or 20 kg of cement, or R20.00 per m3  QC systems monitor the changes in strength where they should be watching the consistency of the aggregates 2 CONFIDENTIAL

AGGREGATES  You can make concrete out of any aggregates.  True but poor aggregates make poor concrete  That concrete is costly and will not perform its function  We have been making aggregates from this quarry for years and nothing has changed  Ja Sure  However the truth is that 70+% of the concrete is made up of aggregates 3 CONFIDENTIAL

4  Definition:  There are different types of aggregates :  fine aggregates (sands)  coarse aggregates  Different physical natures :  r olled  c rushed  Different chemical natures :  limestone  granite  silic a  etc. Limestone aggregates River aggregates Sands Raw materials: aggregates

5  Definition:  Main use in following application fields: ­Concrete ­Driveway bases ­Railway bases 1m 3 concrete : 2 tons of aggregates A residential house: 100 à 300 tons of aggregates A school or hospital : à tons of aggregates 1 km railway : tonnes of aggregates 1 km highway : ~ tons of aggegates Raw materials: aggregates

6  Differentiation between: Rolled / natural aggregates : River aggregates (silicious and silico-chalky) Dune and sea aggregates (silicious) Crushed aggregates : Limestone (sediment) Basalts (volcanic) Porphyres (volcanic) Granites and schistes (eruptive) Raw materials: aggregates

AGGREGATE GRADING  Aggregates are the cheap filler of the volume of concrete  Water and cement are the expensive glue  Admixtures reduce the water content to attain the flow or slump required; therefore reducing the cement requirement.  Surface area. Which has the most surface area per volume a stone or a grain of sand.  The finer the particle the more surface area.  THE MORE GLUE REQUIRED TO COAT THE PARTICLE  The more water and cement 7 CONFIDENTIAL

Aggregate Grading  So the more larger stones in the mix the cheaper the concrete will be  Sizes 75, 37, 26, 19, 13, 9.5, 6.7mm  The finer the sand the more expensive  Sizes 4.75, 2.36, 1.18, 0.60, 0.30, 0.15 mm  The really expensive stuff is the DUST, silt and clay  and lower  Clay Contents - very thirsty, very expensive  Only certain admixtures work with clays. Ask your friendly CHRYSO rep  To fill the volume you need a portion of all the sizes to fill the voids or gaps 8 CONFIDENTIAL

RELATIVE DENSITY  Relative Density (R.D.) or Specific Gravity (S.G.) is the weight of the aggregate relative to water.  1 litre of water = 1 kg  1 litre of your rock = 3.15 kg Norite (2.9 – 3.3) Others 2.5 – 3.5 kg  1 litre of concrete = 2.4 kg or 2400 kg/m3 Norite 2.8kg or 2800kg/m3  If you change R.D. from 2.8 to 2.9 you change the volume by 24 litres or 2.4%  Loose Bulk Density = loosely placed stones 1900 kg/m3  Compacted Bulk Density = compacted placed stones 2000 kg/m3  Bulking Factor = Sand bulks when wet.  This means you are buying water or additional volume 9 CONFIDENTIAL

Cleanliness and Shape 10 CONFIDENTIAL  Round is great. Rolls and allows the concrete to flow  Angular and flaky is horrible, the concrete will not flow  The aggregates must be sound - strong, wearing and the same geological activity  No alkali reactivity  A heap of stones with sand and dust in it is expensive as you will not get consistency when loading. Sand goes to the bottom.  Dust is a killer as its very thirsty. The dust needs washing away.  Where do the piles of dust go when cleaning under conveyor belts?

Don’t tell me they are always the same  Natural product Different parts of the quarry, the overburden is moved but what about the weathered layer on the surface of the rock.  Dykes Faults  Deleterious Materials Wood  Detonators, plastic, paper, metals all cause surface defects  Wearing sieves Holes allow larger particles through  Wet sieves can clog and the holes become smaller and thus the sand becomes finer and the water demand goes up. (40 litres/m3 at Karee 4#)  Natural Sands Need sieving and washing to remove dust and silt 11 CONFIDENTIAL

Adsorption  Some materials will adsorb moisture.  Most in SA are less than 0.5% adsorption so this is not considered.  The rest of the world experience up to 5% regularly.  5% of 1000 kg = 50 litres of water.  Can take 30 minutes to be adsorbed, in doing so what is happening to your slump?  Pre – wet aggregates. Saturated surface dried 12 CONFIDENTIAL

Wearing Surface  The aggregates give the concrete its wearing properties.  They are harder than the glue.  If not they will probably crumble while mixing and push up the water demand. A quarry at Hartebeesport battled with 30 MPa concretes with their stone.  You need enough stone close to the surface of the concrete to provide these properties.  Never just look at concrete and think its stony, compact it first then feel how deep the aggregates are. If more than a few mm deep you are giving away money and you are asking for problems.  Concrete has to be compacted. Compact properly first, then decide.  Contractors are paid to compact, without this compaction the concrete will fail. And as always you will be blamed because you did not point this out to them. 13 CONFIDENTIAL

Curing  Otherwise the complaints will be shrinkage cracks, dusting etc.  It is also your duty to point out that Curing is not a place in China.  Admixtures can assist with solving some of the minor problems  Admixtures make good concrete better not bad concrete good  Admixtures make bad concrete better 14 CONFIDENTIAL

Thank You  Any Questions  Thank You 15 CONFIDENTIAL