This document discusses various types of concrete degradation including corrosion of reinforcement bars due to carbonation or chloride attack when wet. It also discusses concrete spalling which occurs when water in capillaries expands during freezing and thawing cycles, applying pressure and causing fragments to chip away over time. Additionally, it mentions longitudinal and transverse cracks on concrete surfaces in relation to reinforcing steel, as well as cracking, swelling, dislocations, and internal cracking caused by corrosion of steel reinforcement.

1. STUDENT NAME Fazl ullah
RERISTRATION NO 16878
TRIMESTER 7th
SUBJECT Material Testing Repair & Maintenance
ASSIGIMENT NO 01
TEACHER NAME Engr. Asif Nawaz
DATE 12-02-2022
Passion to Design Future

2. Deterioration Due to Corrosion
Concrete degradation may have many different causes. Concrete is mostly damaged by the
corrosion of reinforcement bars due to the carbonatation of hardened cement paste or
chloride attack under wet conditions. The most destructive agent of concretestructures and
components is probably water. Indeed, water often directly participates to chemical
reactions as a reagent and is always necessary as a solvent, or a reacting medium, making
transport of solutes and reactions possible. Without water, many harmful reactions cannot
progress, or are so slow that their harmful consequences become negligible during the
planned service life of the construction. Dry concretehas a much longer lifetimethan water
saturated concrete in contact with circulating water.

3. Spalling Of Concrete Cover:
Concrete spalling is a defectthat appears in a hardened concrete structure or blocks situated
in colder climates, where the concrete is slowly broken down into small flakes known as
spalls from a larger solidified concrete body. Concrete spalling is also known as concrete
scaling.
When a concrete structure is exposed to freezing temperatures, the water stored in the
capillaries of the concrete solidifies and expands, creating an internal pressure on the top
solidified layer. Over time, due to the force applied by freezing and thawing cycles along
with the internal pressure of expanded water, the top layer of the concrete tends to chip
away leaving pit marks, concrete fragments or spalls.
Cracks Parallel To The Reinforcement:
Surface crack width is considered to be the most important parameter that affects the
corrosionof steel in concrete. Cracks on concrete surface which are perpendicular to the
reinforcing steel known as “transverse cracks” and those parallel to longitudinal
reinforcing bars as known as “longitudinal cracks”. Generally, the transverse cracks are
most common in RC.

4. Spalling At Edge:
Cracking, breaking or chipping of joint/crack edges. Usually occurs within about 0.6 m (2
ft.) of joint/crack edge.
Swelling Of Concrete:
When bridges, dam walls and concrete foundations form cracks, AAR is often the culprit:
the alkali-aggregate reaction. It causes the concrete to swell and renders renovations or
even reconstructions necessary.
Dislocation:
A dislocation is simply a defect in the lattice structure in which a few ions in a layer are
missing. This causes the neighboring layers to be displaced slightly to minimize the strain
from the defect. Grain boundary initiation and interface interaction are more common
sources of dislocations.

5. Internal Cracking & Reduction In Area Of Steel Reinforcement:
A common cause of cracking is the corrosionof internal steel reinforcement, a
deterioration process that can affect the bond behavior and anchorage capacity of
reinforcing bars. Corrosion leads to a reduction of the reinforcing bar diameter, the
formation of a weak layer of corrosionproducts around the bar and expansive forces on
the surrounding concrete (that can lead to cracking).