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TECHNICAL PAPER

prescriptive guidelines in most of the codes specify upper limit
of w/c and minimum cement content to ensure adequate paste
content. Exposure conditions are specified from experiences,
the minimum cover to rebar is also specified. Recommended
types of cement are specifically prescribed for specific
deterioration etc.

An elaborate review on degradation phenomena with reference
[60]
to durability of concrete is presented by Glasser et.al . In
their article the authors first investigate general transport
mechanisms, followed by chloride ingress and corrosion,
carbonation, decalcification and sulphate attack. The authors
would expect a transition of durability research from empirical
state to quantitative basis in future.
Figure 33: Service life in the context of maintenance and repair
6.2 Service life in Indian tropical environment
an important role in the durability hence, curing is important.
Segmentation of capillaries by gel ensures less inter-connectivity Quantification of service life of concrete element is environment
of capillaries. Concrete, a composite material consisting of specific. While the major problem faced in subtropical America
particulate natural material bonded with some binder system. and Europe is de-icing chloride salt induced rebar corrosion,
The aggregation of particulate materials of different size is frost action etc., In tropical India, the major problem is rain
commonly known as aggregate, which forms the skeleton matrix induced carbonation and consequent rebar corrosion in
of the composite. The packing of this particulate system is more continental areas other than 700 km long seacoast. In the
compact with maximum size of aggregate (MSA) and leaves seacoast, sea water attack is the main concern. Therefore, the
[5]
less void for paste which again can be attributed to Power . need for climate and country specific exposure conditions
for exposed concrete is recognized and proposed as given in
Simple estimation of packing density, hence the minimum paste
content requirement for avoiding compaction pores through Table 18 and proposed guidelines for service life prediction are
[63-65]
experimental investigation and using Power’s equations for given in Table 19 .
binary mixtures have been reported in literature [5,16,62] . Currently, These zones are superimposed over climatic zones as shown
packing density models are available as proposed by F. D. in Figure 34 [63-65] . Looking at Tables 18 and 19, the Non-Marine
[26]
Larrard . However, need for a minimum paste content for Zones, i.e., hot dry desert climate, warm humid climate,
avoiding compaction pores can increase permeability. Current composite monsoon climate, and very high precipitation zones,

Table 18: Proposed durability zones for Indian condition and possible proposition
MAIN ZONES SUB ZONES PRESCRIPTIVE POSITION PROPOSED GUIDELINES
Use PSC or composite cement with w/c Error function solutions can be used with equivalent
Submerged (MZ1)
< 0.4, appropriate cover after calculation diffusion coefficient, or else nonlinear better solution.
Use PSC or composite cement with w/c Periodic boundary conditions varying with time, velocity
Marine zone Splash zone (MZ2)
< 0.4 flux, wetting and drying.
On shore (5-10 km) Low w/c 0.4 or so Wind driven rain induced velocity flux, wetting and drying.
(MZ3)
Wind driven rain induced velocity flux, wetting and drying
Important structure use
Hot dry desert (NMD) and periodic wetting and drying in case of partially
w/c < 0.4
submerged structure
Wind driven rain induced velocity flux, wetting and drying
Important structure use
Warm Humid (NMW) and periodic wetting and drying in case of partially
w/c < 0.4 submerged structure
Non-marine zone
Wind driven rain induced velocity flux, wetting and drying
Composite Monsoon Important structure use and periodic wetting and drying in case of partially
(NMM) w/c < 0.4
submerged structure
Wind driven rain induced velocity flux, wetting and drying
Very high precipitation Important structure use and periodic wetting and drying in case of partially
(VHP) w/c < 0.4
submerged structure

THE INDIAN CONCRETE JOURNAL | JANUARY 2026 33