Effect of Post-Fire Curing on the Residual Mechanical Properties of Fire-Damaged Self-Compacting Concrete

Abstract

Concrete is recognized for being a fire-resistant construction material. At elevated temperatures concrete can, however, undergo considerable damage such as strength degradation, cracking, and explosive spalling. In recent decades, reuse of fire-damaged concrete structures by means of developing techniques to repair the degraded material has gained interest amongst researchers. Autogenic self-healing methods such as re-curing in water has proven to partly restore the strength of concrete. The extent of restoration is dependent upon various parameters such as concrete type, exposure temperature, and post-fire curing conditions for example. The use of selfcompacting/consolidating concrete (SCC) has become common in the construction industry due to its high workability and low permeability. This paper presents the results of an experimental study aimed at investigating the improved mechanical properties of high temperature exposed SCC concrete by the autogenic self-healing phenomenon resulting from water re-curing. The residual mechanical properties including strength, modulus of elasticity and ultimate strain of the material upon application of different post-fire curing regimes are presented herein with special emphasis on the effect of thermal profile including exposure time, temperature and cooling rate. The experimental results confirm that the recovery of material properties in fire-damaged SCC concrete is contingent on the post-fire water curing conditions.

A Literature Review of Concrete Ability to Sustain Strength after Fire Exposure Based on the Heat Accumulation Factor

“…Self-compacting concrete samples were examined in [ 63 ] by heating to 300, 450, and 600 °C and then tested after 0, 2, 7, and 28 days after cooling. The results prove the great potential of concrete to regain strength, in some instances even exceeding strength before high-temperature exposure ( Figure 10 ).…”

“…It is worth noticing that the regain occurred in the first 90 days; after that time, only a small increase was recorded.

Figure 10 Relative residual strength of concrete [ 60 ] and self-compacting concrete [ 64 ] as a function of re-curing time (t) for different re-curing methods (AC—air re-curing, WC—water re-curing) and different peak temperatures θ = 300, 450, 600, and 800 °C according to [ 60 ]—Poon and [ 63 ]—Mirmomeni.

Figure 11 Relative residual strength of concrete as a function of re-curing time (t) for different peak temperatures θ = 300, 450, 600, and 750 °C, and different re-curing methods (AC—air re-curing, WC—water re-curing, PF—re-curing in a plastic film) according to [ 61 ]—Souza and [ 50 ]—Li.

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“… Relative residual strength of concrete [ 60 ] and self-compacting concrete [ 64 ] as a function of re-curing time (t) for different re-curing methods (AC—air re-curing, WC—water re-curing) and different peak temperatures θ = 300, 450, 600, and 800 °C according to [ 60 ]—Poon and [ 63 ]—Mirmomeni. …”