Publication: Development and evaluation of volcanic ash based high performance Sustainable concrete incorporating metakaolin, micro and nano silica
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Date
2024-09-01
Authors
Kaffayatullah, Khan
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Abstract
Reducing carbon emissions and energy consumption in concrete production is
an effective strategy for addressing global environmental challenges. The efficient and
viable use of available SCMs resources for producing high-performance green
concrete is critical for achieving high resilience and sustainability in our built
environment. Therefore, this study was aimed on optimizing the use of high volumes
of volcanic ash (VA) combined with metakaolin (MK), micro-silica (MS), and
colloidal nano-silica (NS) to develop high-performance and sustainable concrete. To
optimize the dosage and particle size of NS, mortar composites were designed and
analysed and statistical modelling based on Response Surface Methodology (RSM)
and Artificial Neural Networks (ANN) was employed. Mortar testing revealed
enhanced strength and durability properties, a denser microstructure and lower
environmental impact for NS80 at medium (5%) and high dosages (10%), while
the developed RSM and ANN models validated the experimental results.
Subsequently, binary, ternary and quaternary concrete mixes were designed having
high volume VA in the range of 20%-40% along with 5%-10%, each of MK, MS or
NS and their blends. Mechanical, durability, microstructural and pore-structure
properties were studied for the designed concrete mixes followed by evaluation of their
global warming potential (GWP) and embodied energy (EE). Experimental results
showed that ternary and quaternary concrete mixes containing 30% of coupled SCMs
exhibited better compressive strength both at early and later ages. Moreover, the
ternary and quaternary mixes containing (30%-50%) of coupled SCMs demonstrated better resistance to chloride ion penetration and water absorption compared to the
control and binary mixes. A remarkable decrease of autogenous shrinkage was
recorded in ternary concrete mixes (-261 to -667 με) as compared to control (-701 με)
and binary concrete mixes (-516 to -668 με). Moreover, the ternary mixes exhibited
lowest shrinkage rate and ultimate drying shrinkage as compared to that of control and
binary concrete mixes. Furthermore, the SEM and BSE imaging with EDS analysis
and N2 adsorption analysis demonstrated refined micro and pore structure of ternary
and quaternary mixes owing to formation of high density C-S-H and C-A-S-H gels.
Moreover, the ternary and quaternary concrete mixes demonstrated lower GWP and
EE along with better strength and durability properties. Consequently, the current
research findings indicated that high volumes of VA in combination with MK, MS, or
NS be effectively used as a substitute of cement at up to 50% to produce high
performance concretes with a significantly reduced ecological footprint.