There Is More To Recycled Concrete Aggregate
Than Just Aggregate
Author(s)
Z. A. Krezel, K. J. McManus, N. Cumbo, H. Karlie & C. Cox
Abstract
In Australia, recycled concrete aggregate (RC Aggregate) is produced mainly
from two sources, viz. crushed demolition waste concrete and relatively ‘fresh’
crushed construction waste concrete. Apart from standard fine and coarse
particles, RC Aggregate consists of a significant amount of very fine dust
intrinsic to the crushing process of concrete waste. The amount and
characteristics of the very fine particles and presence of cement paste residue
(CPR) differentiate RC Aggregate from commonly used crushed natural
aggregate. The aggregate fines and CPR impact a number of basic engineering
properties of the aggregate and also have potential to influence behaviour of the
aggregate’s varies applications, including road base and concrete.
This paper reports on an investigation into mineral composition and
re-cementing potential of RC Aggregate. Scanning Electron Microscopy with
Energy Dispersive X-ray analysis and the X-Ray Diffraction examination were
used to determine elemental and compound composition of solid CPR and fines
of the aggregate. The re-cementing potential of the fines was assessed by a
method, commonly used in determination of cement content in cement treated
aggregate used in roads construction.
The results indicate that mineral composition of RC Aggregate is different
from that of natural crushed aggregate or commonly used fine concrete sand.
Preliminary results also indicate that RC Aggregate contains some anhydrous
materials that react with Portland or Blended cements, or undergo a pozzolanic
reaction with some hydration products such as calcium hydroxide.
Keywords: recycled concrete aggregate, mineral composition, re-cementing.
Keywords
recycled concrete aggregate, mineral composition, re-cementing.
Related Book
Other papers in this volume
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