Self-Healing Products of Cement Pastes with Supplementary Cementitious Materials, Calcium Sulfoaluminate and Crystalline Admixtures

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.

Analysis of a Composite Admixture Based on Ready-Mixed Concrete Waste Residuals

“…11 and 12. It can be found that all samples have an obvious mass loss in the temperature range of 30°C-400°C, 400°C-550°C and 550°C-1000°C, which is due to dehydration of C-S-H gel/AFt, the dehydration of Ca(OH) 2 and the decomposition of CaCO 3 , respectively [24,25]. Compared with the specimens of E0 group, the WRMS and composite admixtures do not change the types of hydration products.…”

“…3 shows the TG-DSC analysis result of the WRMS. It can be seen clearly that there is weight loss of the WRMS near 450°C and 700°C, which is attributed to the decomposition of Ca (OH) 2 and CaCO 3 , respectively [24,25]. Combined with the analysis results of XRD and TG-DSC, it can be determined that there is no component harmful to cement in the WRMS, so the WRMS can be used to prepare concrete admixture.…”

Preparation and Hydration Mechanisms of Low Carbon Ferrochrome Slag-Granulated Blast Furnace Slag Composite Cementitious Materials

“…Li [ 22 ] used steel slag to replace part of the slag, and sodium sulfate was used to stimulate the activity of the slag—slag gelling system. Park [ 23 ] investigated the effects of SCMs, expander, and crystallizer on the hydration products of cementified materials. These views clarify the hydration reaction characteristics of granulated blast furnace slag.…”