Mitigating the Risk of Early Age Cracking in Fly Ash Blended Cement-Based Concrete Using Ferronickel Slag Sand

Abstract

A concrete mix (FNS25) including 50% natural sand replacement by ferronickel slag (FNS) sand and 25% ordinary portland cement (OPC) substitution by fly ash (FA) was considered to mitigate the risk of early-age cracking in fly ash blended cement-based concrete. Experiments were carried out to accurately quantify early-age shrinkage and tensile creep and assess their influence on early-age cracking in reinforced concrete members. The results show the free shrinkage strain is not influenced by either fly ash or FNS significantly, whereas the tensile creep of FNS25 is significantly larger than that of both OPC100 and FA20. Both restrained ring test and simulations on reinforced concrete members confirm that partly replacing conventional sand by FNS sand reduces the risk of early-age cracking. Microstructural analysis of the Interface Transition Zone (ITZ) of FNS sand shows that excess in Portlandite is absent in FNS sand ITZ leading to a higher early-age tensile strength of FNS25 concrete.

A Critical Review on Early-Age Cracking in Concrete

“…They discussed the use of a fine ferronickel slaughtering aggregate (FNS) to reduce the possibility of initial cracking of ash-based concrete with travel. Their study involved 50% of natural sand replaced with FNS, and it was known that 25% of ordinary Portland cement replaced with fly ash mixed cement mitigated the risk of early cracking [43].…”

Modeling blended cement concrete tensile creep for standard ring test application

“…In addition, the applicability of these tensile creep models 19,20 does not distinguish between conventional concrete and SCMs‐based concrete. It is known that the tensile creep behavior of concrete mixes with SCMs is considerably different from that of conventional concrete 9,26–28 …”

“…It is known that the tensile creep behavior of concrete mixes with SCMs is considerably different from that of conventional concrete. 9,[26][27][28] SCMs have been widely used in concrete to reduce cement content (consequently decreasing CO 2 emission) and improve the mechanical and durability performance of concrete. 29 In addition, SCMs are mainly industrial byproducts, so more economical than cement.…”

“…[30][31][32] For instance, Khan et al reported that incorporating GGBFS can significantly increase tensile creep, 9 while the performance of fly ash concrete is similar to that of reference concrete. 26 Nguyen et al 27 pointed out that the introduction of Ferronickel Slag (FNS) can also increase tensile creep. Pane and Hansen 28 reported that the risk of early age cracking of GGBFS concrete is reduced due to increased tensile creep.…”