Is Cement Paste Modified with Carbon Nanomaterials Capable of Self-Repair after a Fire?

Abstract

This manuscript presents preliminary results on the cement paste potential, with and without carbon nanomaterials, to heal high-temperature cracks. Cement paste beams were subjected to thermal loading of 200°C and 400°C after 28 days of water curing. High temperature caused the formation of microcrack networks on the specimen’s surface. Self-healing was achieved by exposing the cracked samples to cyclic water immersion. The efficiency of the process was evaluated based on the crack closure and mechanical properties recovery after 24 days. The results indicated a distinct dependence of the healing on the loading temperature. Carbon nanotubes had a positive effect on self-repair efficiency.

Autogenous self-healing of thermally damaged cement paste with carbon nanomaterials subjected to different environmental stimulators

“…The following specimens were tested: three undamaged beams (marked as "0 ′′ ), three after 200 • C and 400 • C (marked as "bh") exposure, and three after self-healing in each environmental stimulator (marked as "h"). The recovery of flexural strength was defined by two parameters, FSR0 and FSRt [29]:…”

“…The following specimens were tested: five intact samples (marked as "0 ′′ ), five samples after 200 • C and 400 • C exposure (marked as "bh"), and five samples after the healing process for each exposure (marked as "h"). The recovery of compressive strength was defined by two parameters, CSR0 and CSRt [29]:…”

“…where σ c,0 depicts the compressive strength of the intact specimen at 28 days; σ c,bh and σ c,h represent the compressive strengths before and after healing, respectively [29].…”

“…In addition, the rehydration of Ca(OH) 2 occurs in the presence of moisture after cooling [27]. The binder matrix alterations cause coarsening porosity and microcracks formation [28,29].…”

“…The re-curing regime seemed to be a dominant factor for the self-healing of the thermally cracked concrete [42]. Most studies applied a combination of air cooling and continuous water immersion re-curing regime, which is challenging to accomplish in field conditions [29,34,35,37,38,40]. Water is necessary to transport and dissolve the material, e.g., calcium ions, into the cracks.…”