SA Affordable Housing March / April 2018 // Issue: 69 | Page 18

FEATURES
Preventing costly repairs
Spalling of joints in concrete floors should be regarded as
early warning of more serious potential long-term damage.
By The Concrete Institute | Photos by The Concrete Institute
Pictured above and below: Examples of spalled concrete floors.
S
palling is the peeling, popping out or flaking of a concrete
surface. Moisture and often salt too, pushes outward from
the inside. The size and cost of spalling repairs can be
reduced if the damage is detected and repaired at an early stage.
On any construction site, whether a single storey stand-alone
unit or multi-storey project – from the civils work onwards –
concrete forms the basis for many components. Concrete’s
quality and stability can speak directly to the safety of the users
or occupants – from foundations to heavy traffic areas and from
slabs to stairways. It is therefore important to ensure proper
identification of any concrete that may be compromised.
Although concrete is already a technical subject, basic
knowledge, such as best practice for repairs, can assist in long-
term effects that would otherwise create unnecessary risk.
Spalling of joints is the cracking, breaking or chipping in the
immediate vicinity of joints, usually within 100mm of the joint.
A spall usually does not extend vertically through the slab but
extends to intersect the joint at an angle. Spalling at joints
usually results from:
• Excessive stress at the joint caused by accumulation of
incompressible material in the joint and subsequent
expansion of adjoining slabs in concrete pavements;
• Weak concrete at the joint;
• Poorly designed or constructed load-transfer devices or
failure of such devices; and
• Poorly constructed joints.
Early repair of spalling is needed to improve serviceability, deter
further deterioration and provide proper edges so that the joints
can be resealed effectively. Before any repairs are carried out, it
should be determined if the spalling is due to a loss of load
transfer at the joints. If this is the case, the load transfer needs to
be restored before edge spalls are repaired. Reinstating load
transfer generally requires full-depth, partial panel repair or
reconstruction of the joint.
Although concrete is already
a technical subject, basic
knowledge, such as best
practice for repairs, can
assist in long-term effects
that would otherwise create
unnecessary risk.
See more on page 18.
16
MARCH - APRIL 2018
AFFORDABLE
SA HOUSING