Compatibility and adhesion between fiberreinforced alkali-activated repair mortar and concrete substrate
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Data
2018-01-15
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Centro Federal de Educação Tecnológica de Minas Gerais
Resumo
Concrete repairing is a complex task that requires a special knowledge of technical
building regulations and standards, deterioration mechanism and diagnosis, repair
principles and methods, repair materials, execution of repair works, inspections,
monitoring and maintenance. So far, most used patch repair mortars fall into two
categories, (i) the mortars based on inorganic binders (Portland cement, PC) and (ii)
those based on organic binders (polymers). Recent investigations reveal a third
category of mortars with high potential to be used in the field of concrete repair, i.e.
the alkali-activated based mortars. Alkali-activated materials (AAM) have been
widely promoted as a greener binder for sustainable constructions. These binders
can be generated from a wide range of aluminosilicate materials under alkaline
conditions to produce a hardened component. This study, therefore, aims to evaluate
the compatibility and the adhesion between a fiber-reinforced alkali-activated mortar
and a concrete substrate. Different formulations of AAM were initially studied, based
on the alkaline activation of metakaolin (MK) and blast furnace slag (BFS); their
mechanical properties and modulus of elasticity were assessed. Five formulations
were selected after this preliminary evaluation in order to produce the repair mortar
and to apply onto concrete substrates. A volume fraction of 0.25% of PP fiber was
used to mitigate the early-age shrinkage and to increase the adhesion bond of the
repair mortar with the concrete substrate. The bond strength was evaluated by pulloff testing. The crack and delamination behaviour were assessed by four-point
bending tests. Physical properties were also investigated: water absorption, apparent
porosity and apparent density. Results showed a good compatibility and adhesion
between alkali-activated repair mortars and the PC substrate. Satisfactory bond
strengths were found meeting the required by the structure repair standard BS EN
1504. The delamination issue was observed only in 100 % MK-based mortars and
the crack propagation behaviour was typical from brittle materials. The formulation
80MK-20BFS designed with SiO2/Al2O3 molar ratio 3.0 and fiber-reinforced was
selected as the most promising one to structural repair proposes.
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Reações agregadas alcalinas, Argamassas - Manutenção e reparos, Aderências, Compostos fibrosos