Abstract
Considering its superior engineering properties, ultrahigh performance concrete (UHPC) has emerged as a strong contender to replace normal strength concrete (NSC) in diverse construction applications. While the mechanical properties of UHPC have been thoroughly explored, there is still dearth of studies that quantify the durability of UHPC, especially for sustainable mixtures made with local materials. Therefore, this research aims at investigating the alkali-silica reactivity (ASR) potential in sustainable UHPC in comparison with that of NSC. Sustainable UHPC mixtures were prepared using waste untreated coal ash (CA), raw slag (RS), and locally produced steel fibers. UHPC and benchmark NSC specimens were cast for assessing the compressive strength, flexural strength, and ASR expansion. Specimens were exposed to two curing regimes: accelerated ASR conditions (as per ASTM C1260) and normal water curing. UHPC specimens incorporating RS achieved higher compressive and flexural strengths in comparison with that of identical UHPC specimens made with CA. ASR expansion of control NSC specimens exceeded the ASTM C1260 limits (>0.20% at 28 days). Conversely, experimental results demonstrate that UHPC specimens incurred much less ASR expansion, well below the ASTM C1260 limits. Moreover, UHPC specimens incorporating steel fibers exhibited lower expansion compared to that of companion UHPC specimens without fibers. It was also observed that the mechanical properties of NSC specimens suffered more drastic degradation under accelerated ASR exposure compared to UHPC specimens. Interestingly, UHPC specimens exposed to accelerated ASR conditions attained higher mechanical properties compared to that of reference identical specimens cured in normal water. Therefore, it can be concluded that ASR exposure had insignificant effect on sustainable UHPC incorporating CA and RS, especially for specimens incorporating fibers. Results indicate that UHPC is a robust competitor to NSC for the construction of mega-scale projects where exposure to ASR conducive conditions prevails.
Highlights
Recent developments and advances in chemical and mineral admixtures have led to the introduction of various types of ultra-durable cement based materials
It was observed that the mechanical properties of normal strength concrete (NSC) specimens suffered more drastic degradation under accelerated alkali-silica reactivity (ASR) exposure compared to ultrahigh performance concrete (UHPC) specimens
Decreased flow of the UHPC mixture with coal ash (CA) was mainly attributed to its high loss on ignition content primarily consisting of unburnt carbon, which tends to compromise the effect of the superplasticizer
Summary
Recent developments and advances in chemical and mineral admixtures have led to the introduction of various types of ultra-durable cement based materials. Shafaatian et al (2013) [44] reported that the replacement of cement with supplementary cementitious materials (SCMs) limits the amount of alkalis in the paste, reducing the ASR expansion. UHPC incorporating locally available raw materials and using the normal curing regime and undamaged UHPC specimens showed ASR expansion of 0.02% after 600 days [50]. Under conditions can provide insight into the potential application of sustainable dition (1N NaOH at 80 C) as compared to that of identical control specimens cured in UHPCThe in large-scale construction exposed of to UHPC. The outcome of this study will benefit restakeholders and decision makers in appraising UHPC incorporating local waste materials searchers and of other construction stakeholders for better understandingunder the improved dufor the design sustainable, resilient and durable civil infrastructure severe ASR rability performance sustainable mixtures, in aggressive exposures. Of sustainable UHPC mixtures incorporating waste materials reduces the environmental overburden due to the deposition of byproducts in open landfills
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