CURRENT APPROACHES AND NEW RESEARCH IN
MODERN SCIENCES
International scientific-online conference
111
FACTORS AFFECTING THE DURABILITY OF MONOLITHIC
ELEMENTS OF LOW-CARBON BUILDINGS UNDER OPERATING
CONDITIONS
Rashidov J.G.
1
Ruziev B.D.
2
1
PhD in Technical Sciences, Associate Professor, Tashkent University of
Architecture and Civil Engineering;
2
Acting Head of the Architectural and Construction Department, JSC
"BOSHTRANSLOYIHA" Main Design and Survey Institute for Transport
https://doi.org/10.5281/zenodo.16880882
Abstract
The mechanisms of degradation of monolithic elements in low-carbon
buildings—carbonation, reinforcement corrosion, fatigue damage, and crack
formation—are analyzed. It is established that low-carbon concretes have
different carbonation and moisture transport dynamics compared to
conventional mixtures. The necessity of a comprehensive approach, integrating
building physics methods and simplified finite element analysis for predicting
the residual service life of structures, is substantiated.
Keywords:
low-carbon concrete, durability, carbonation, reinforcement
corrosion, moisture transport, cracking, building physics, finite element analysis.
Introduction.
In the context of a global transition toward sustainable construction and
the reduction of carbon footprints, the use of low-carbon concretes has gained
particular importance. These materials, achieved by reducing clinker content
and incorporating mineral additives, allow a significant decrease in CO₂
emissions at the production stage[1-3]. However, despite their environmental
advantages, the durability of such concretes under real operating conditions
remains insufficiently studied. Their physico-mechanical properties, moisture
transport behavior, carbonation rates, and corrosion resistance may differ
significantly from those of traditional cement compositions.
The purpose of this study is to identify and systematize the key factors
determining the durability of monolithic elements made of low-carbon
concretes, and to substantiate predictive methods for estimating their residual
service life.
Degradation mechanisms in low-carbon concretes.
The long-term performance of low-carbon concretes is determined by a
set of interrelated degradation processes that gradually alter their
microstructure and mechanical integrity [4-5]. Among the most critical
CURRENT APPROACHES AND NEW RESEARCH IN
MODERN SCIENCES
International scientific-online conference
112
mechanisms is carbonation, a physicochemical reaction in which carbon dioxide
from the surrounding environment penetrates the pore system of the hardened
material and reacts with calcium hydroxide, forming calcium carbonate. This
reaction progressively lowers the alkalinity of the cement matrix, reducing the
pH below the threshold required to maintain the passive oxide film on
embedded steel reinforcement. Once the protective layer is compromised, the
steel becomes susceptible to electrochemical corrosion. The rate of carbonation
in low-carbon concretes can vary widely, depending on mix design parameters,
degree of hydration, curing conditions, and the resulting pore structure. In mixes
with increased total porosity or greater connectivity between capillary pores,
carbon dioxide ingress is facilitated, potentially accelerating depassivation.
Conversely, formulations achieving a dense, well-hydrated microstructure, often
through optimized water-to-binder ratios and supplementary cementitious
materials, can significantly slow the progression of the carbonation front.
Closely linked to carbonation is reinforcement corrosion, which can also
be initiated by the ingress of chloride ions. In coastal or urban-industrial
environments, airborne chlorides from sea spray, de-icing salts, or vehicular
emissions can penetrate the concrete cover, accumulate near the steel surface,
and locally disrupt the passive film even in the absence of complete carbonation.
The presence of aggressive gases such as sulfur dioxide, combined with fine
particulate matter, can further intensify this process by creating localized acidic
conditions within the pore solution. Low-carbon concretes that incorporate
finely divided mineral additives such as microsilica or fly ash often exhibit a
more refined pore structure and reduced permeability, which can lower chloride
diffusivity and delay corrosion onset.
However, these potential benefits are highly dependent on workmanship
and curing quality. Poor compaction can create interconnected voids that act as
preferential pathways for moisture and chlorides, while inadequate curing can
hinder the pozzolanic reaction and leave the matrix more permeable than
intended.
The interplay between carbonation and chloride-induced corrosion is
particularly important in the service life assessment of low-carbon concretes. In
some exposure conditions, the two mechanisms can act synergistically—
carbonation lowers alkalinity while chlorides attack steel directly—leading to an
accelerated deterioration rate compared to either mechanism acting alone.
For this reason, a comprehensive durability design for low-carbon
concretes must consider the combined effects of environmental exposure,
CURRENT APPROACHES AND NEW RESEARCH IN
MODERN SCIENCES
International scientific-online conference
113
material composition, and construction practices. This approach ensures that
the ecological benefits of reducing cement clinker content are not offset by
premature structural degradation, thereby aligning sustainability objectives
with long-term performance requirements.
Fatigue damage and crack formation.
Under variable mechanical loads, shrinkage deformations, and cyclic
temperature fluctuations, microcracks inevitably develop in the cementitious
matrix and at the aggregate–paste interface. While initially microscopic, these
defects act as capillary pathways, significantly increasing the rate of moisture
ingress and facilitating the transport of chlorides, sulfates, and other aggressive
agents. This accelerated penetration intensifies reinforcement depassivation and
corrosion processes, ultimately reducing the structure’s service life.
Experimental observations indicate that even a network of microcracks with
widths below 0.1 mm can increase chloride diffusion coefficients by 30–50 %
compared to uncracked specimens. In low-carbon concretes, the substitution of
clinker with supplementary cementitious materials alters fundamental
mechanical properties such as elastic modulus, creep compliance, and tensile
strength. For example, studies show that certain fly ash–based mixes may
exhibit up to 12–18 % lower initial modulus of elasticity than ordinary Portland
cement concretes of the same compressive strength class, while long-term creep
strains can be 10–15 % higher. These shifts in mechanical behavior influence
crack initiation thresholds, propagation rates, and closure tendencies under
sustained or cyclic loading.
Consequently, structural design codes and predictive service-life models
calibrated for conventional concretes require adjustment to accurately reflect
the deformation characteristics of low-carbon systems. Without such
recalibration, there is a risk of underestimating the rate of stiffness loss,
overestimating crack healing potential, and failing to predict accelerated
durability loss under combined mechanical and environmental stressors.
Moisture transport within the pore structure of concrete is a critical factor
influencing its freeze–thaw durability, especially in climates with pronounced
seasonal or daily temperature fluctuations. When free water within the
capillaries freezes, its volumetric expansion exerts internal tensile stresses on
the surrounding cement paste. Repeated cycles of freezing and thawing
gradually weaken the microstructure, leading to scaling, surface delamination,
and progressive loss of material integrity. In low-carbon concretes, the presence
of higher capillary conductivity—often linked to specific binder compositions or
CURRENT APPROACHES AND NEW RESEARCH IN
MODERN SCIENCES
International scientific-online conference
114
insufficient curing—can accelerate the rate of water migration, increasing the
degree of saturation in critical zones. This makes such concretes more
vulnerable to frost-induced damage, particularly when the air-entrainment
system is poorly developed or the quality of aggregates is suboptimal. Field
studies in cold and temperate continental climates indicate that inadequate air-
void parameters can reduce freeze–thaw resistance by more than 40 %, even in
otherwise dense concretes.
To mitigate these degradation risks and extend the service life of monolithic
elements, a multi-faceted approach is required. First, concrete mix designs
should be optimized with respect to anticipated environmental exposure,
balancing workability, strength, and durability parameters while ensuring a
refined but adequately air-entrained pore system. The selection and quality
control of aggregates must minimize freeze–thaw susceptibility and alkali–silica
reactivity. Second, the application of surface protective coatings can reduce
direct water ingress and shield against chloride penetration in aggressive
environments. Hydrophobic impregnations, especially silane- and siloxane-
based formulations, can further lower water absorption without significantly
altering vapor permeability, thus helping maintain the hygrothermal balance of
the structure. Third, systematic structural monitoring—using non-destructive
testing methods such as ultrasonic pulse velocity, ground-penetrating radar, or
electrical resistivity measurements—enables early detection of moisture-related
deterioration before it becomes critical. Finally, the adoption of finite element
modeling tools allows engineers to simulate coupled hygrothermal and
mechanical processes within the concrete, predicting the progression of damage
under combined environmental and load-induced stresses. This predictive
capability supports proactive maintenance planning, ensuring that the
environmental benefits of low-carbon concretes are matched by their long-term
structural reliability.
Conclusion.
The durability of monolithic elements in low-carbon buildings is determined by
a combination of factors—from material composition and microstructural
characteristics to climatic influences and service conditions. The adoption of
low-carbon concretes demands careful consideration of their specific properties
during both design and operational stages. Integrated diagnostic and predictive
approaches, combining building physics methods with simplified finite element
analysis, offer a viable path to prolonging service life while enhancing
environmental and economic performance over the building’s lifecycle.
CURRENT APPROACHES AND NEW RESEARCH IN
MODERN SCIENCES
International scientific-online conference
115
References:
1.
Geng, H., Ma, Y., Li, Z., Liu, Z., & Zhang, Y. (2023). Long-term carbonation
resistance of low-carbon concrete incorporating supplementary cementitious
materials.
Construction
and
Building
Materials,
397,
132523.
https://doi.org/10.1016/j.conbuildmat.2023.132523
2.
Li, C., Wang, Q., Huang, Z., & Shi, C. (2024). Durability of low-carbon
concretes under combined carbonation and chloride ingress. Cement and
Concrete
Composites,
150,
105157.
https://doi.org/10.1016/j.cemconcomp.2023.105157
3.
Scrivener, K.L., John, V.M., Dhandapani, Y., et al. (2022). Eco-efficient
cements: Potential economically viable solutions for a low-CO₂ cement-based
materials industry. Cement and Concrete Research, 154, 106718.
https://doi.org/10.1016/j.cemconres.2022.106718
4.
Soutsos, M., Kwasny, J., & McCarter, W.J. (2021). Influence of curing on the
durability
of
low-carbon
concrete.
Materials,
14(15),
4252.
https://doi.org/10.3390/ma14154252
5.
Provis, J.L., Scrivener, K.L., & van Deventer, J.S.J. (2020). Low-CO₂ cements:
Extending sustainability in construction. Nature Reviews Materials, 5(9), 673–
689. https://doi.org/10.1038/s41578-020-0206-4
