Abstract
The phase composition of self-healing products generated in cracks affects self-healing performance. This study investigated the self-healing products of cementitious materials using supplementary cementitious materials (SCMs), a calcium sulfoaluminate (CSA) expansion agent, and crystalline additives (CAs). Ground-granulated blast-furnace slag (GGBFS), fly ash (FA), and silica fume (SF) were used as SCMs, and anhydrite, Na2SO4, Na2CO3, and MgCO3 were used as crystalline additives (CAs). An artificial crack method was used to collect the self-healing products in the crack of the paste. The phase composition of the self-healing products was analyzed through X-ray diffraction (XRD)/Rietveld refinements and thermogravimetry/differential thermogravimetry (TG/DTG) analysis, and their morphology and ion concentration were examined through scanning electron microscopy with energy dispersive spectroscopy (SEM–EDS). From the results, the main compound of self-healing products was found to be calcite. GGBFS and FA decreased the content of portlandite, and the use of CAs led to the formation of alkali sulfate and alkali carbonate. The SEM–EDS analysis results showed that when GGBFS and FA were used, a large proportion of the self-healing products contained C-S-H and C-A-H, and the use of CSA led to the formation of monosulfate and ettringite.
Highlights
Concrete is the most widely used construction material worldwide, owing to its high compressive strength and low cost; it has a high risk of cracking because of hydration, heat and contraction resulting from its relatively low tensile strength [1,2,3,4].Cracks generated in concrete act as passages for moisture and harmful ions, degrading the durability of concrete structures [5,6]
scanning electron microscopy with energy dispersive spectroscopy (SEM–EDS) analysis results showed that when Ground-granulated blast-furnace slag (GGBFS) and Fly ash (FA) were used, a large proportion of the self-healing products contained C-S-H and C-A-H, and the use of calcium sulfoaluminate (CSA) led to the formation of monosulfate and ettringite
During the autogenous healing of cracks, unreacted cement particles on the crack surface react with water penetrating through the cracks, which are filled by the products of further hydration [19,20]
Summary
Concrete is the most widely used construction material worldwide, owing to its high compressive strength and low cost; it has a high risk of cracking because of hydration, heat and contraction resulting from its relatively low tensile strength [1,2,3,4].Cracks generated in concrete act as passages for moisture and harmful ions, degrading the durability of concrete structures [5,6]. Concrete is the most widely used construction material worldwide, owing to its high compressive strength and low cost; it has a high risk of cracking because of hydration, heat and contraction resulting from its relatively low tensile strength [1,2,3,4]. In terms of crack management, researchers have developed a self-healing concrete technology that can prevent durability reduction by healing cracks in concrete structures owing to the inherent properties of the structures [7,8,9,10,11,12,13,14,15]. Cementitious materials have a natural characteristic in that cracks of certain widths can be self-healed, in a process called autogenous healing [16,17,18]. During the autogenous healing of cracks, unreacted cement particles on the crack surface react with water penetrating through the cracks, which are filled by the products of further hydration [19,20]
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