Page 27 - ICJ Jan 2026

TECHNICAL PAPER

to repair cycle of the element and maintenance of the structure.
In some cases, the whole structure may require rehabilitation.
Service life, therefore, can also be considered from the time of
last repair. To increase the reliability against loading, redundancy
in terms of excess capacity is always ensured in structure, so,
even if one member becomes incapable of carrying the load
other members share it by redistribution. Thus, the capacity
to redistribute the load provides additional cushion against
failure to collapse due to deterioration. Service life of concrete
elements, therefore, is related to maintenance cost rather than
collapses, as deterioration rarely leads to sudden collapse of
the structure. Maintenance of concrete structures is a necessity;
economic and appropriate maintenance policies and repair
Figure 30: Thermodynamic tendency and kinetics strategies for concrete structures can be formulated throughout
the service life. The exposure environment, concrete material
and quality etc., control the rate of degradation and hence,
and in steel reinforced concrete, the degradation may also take the service life of concrete structural members. Actual time of
place by carbonation and chloride ingress leading to corrosion attainment of serviceability limit relates to cover depth and
of rebar. varies from member element to member element as; neither
the exposure condition of all elements is same nor their
Serviceability limit states are important concerns for structures,
resistance against deterioration is identical. The uncertainties
like bridges and buildings in addition to limit state of collapse. of exposure environment and material shall be accounted for
Repair and rehabilitation can often take care of serviceability service life design of structure. The concept of service life is
limit failures without complete replacement or reconstruction of further elaborated in Figure 31 and 32. In Figure 33 service life in
structures. relation to maintenance and repair is explained [9-11,58-61] .

Defining service life of structure in the context of durability All the deterioration process mentioned earlier involves
is related to serviceability limit, although physical life up to ingress of water and / or oxygen or some other agent causing
collapse or demolition, may extend to a much longer period. degradation. Permeability is a measure of the ease with which
For concrete, performance is dynamic and changes with time. liquid or gases can travel through the concrete. It is used as a
Service life can be understood as the period after inception of qualitative measure of durability. The Darcy’s Law in saturated
the structure, during which all the essential properties of the state is popular in water flow through soil, and the same concept
structure meet or exceed the minimum acceptable value [9-11,58-61] . was used in the early days of durability research. Rate of flow per
Design against deterioration is not related to collapse, as the unit area (q), is given as q = k dh/dx, where, k is the coefficient
process of deterioration is slow, can be detected early in most of permeability in m/s; dh/dx is steady hydraulic gradient. Power
cases and the impending danger of collapse can be avoided by et al. [7,12] reported the variation of permeability with the w/c,
appropriate and timely repair of element. Service life is related age and hence, with capillary porosity. Segmentation age plays

Figure 31: Performance against time Figure 32: Degradation and service life (time)

32 THE INDIAN CONCRETE JOURNAL | JANUARY 2026