Byoungsun Park

This study investigated the grinding characteristics, hydration behavior, and physical properties of cement containing the alkanolamine-based grinding aids (GAs) triethanolamine (TEA) and triisopropanolamine (TIPA). Fractal theory was applied to particle size distributions (PSDs) to determine their correlation with compressive strength. Four GA-modified cements were prepared by adding TEA or TIPA at 300 or 600 ppm, alongside two reference cements without GAs but with different specific surface areas. The addition of 600 ppm TEA markedly increased specific surface area, whereas TIPA produced comparable surface areas at both dosages. For cements containing TEA or TIPA, the proportion of particles smaller than 3 μm increased. X-ray diffraction revealed a distinct monosulfate peak at 7 d in GA-modified cements, indicating accelerated C₃A and C₄AF hydration. TEA and TIPA-containing cements achieved higher 3-d compressive strength; however, after 7 d, all samples except the cement with 600 ppm TIPA exhibited strengths similar to or slightly lower than the cement without GAs. Two fractal dimensions, obtained by dividing PSD into < 3.596 μm and 3.596–38.844 μm size ranges, exhibited strong correlations with compressive strength at 3 and 7 d, respectively. These results confirm that early-age strength is strongly associated with the fractal dimensions of cement particles.

This study investigated the effects of the fly ash (FA) particle size and chemical activators on the hydration reactions of high-volume fly ash (HVFA) cement pastes and the mechanical properties of HVFA mortars, with five types of FA with varying proportions of particles smaller than 10 μm prepared to assess the influence of particle size. In addition, the effect of chemical admixtures on the early-age hydration of the HVFA cement paste was evaluated. Quartz powder with the same fineness as that of normal FA was prepared to specifically examine the pozzolanic reaction of FA. The hydration reactions of the HVFA cement pastes were analyzed using isothermal calorimetry to measure the heat of hydration for 72 h. The results showed that an increase in the contents of FA particles with a diameter lower than 10 μm increases specific heat flow. Chemical activators, including Na₂SO₄, triethanolamine (TEA), and triisopropanolamine (TIPA), promote early-age hydration of HVFA cement pastes. The mechanical properties of the HVFA mortar were evaluated by measuring its compressive strength at 3 d, 7 d, and 28 d, with the findings revealing that the compressive strength of HVFA mortar improved with an increased proportion of FA particles smaller than 10 μm. Na₂SO₄, TEA, and TIPA consistently increased the compressive strength of the HVFA mortars.

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.

In this study, we investigated the effects of mineral admixtures on the autogenous healing of flexural mortar members through a chloride ion penetration test. The mineral admixtures used were ground granulated blast-furnace slag (GGBS), fly ash, silica fume (SF), clinker binder, and clinker sand. Through a four-point bending test, a crack of approximately 100 μm was induced at the bottom of the flexural mortar member, and the chloride ion penetration depth through the crack was measured to evaluate the self-healing performance. Additionally, we analyzed the correlation between the self-healing performances, which was measured through water flow and water absorption tests. The experimental results showed that the chloride ion penetration depth decreased due to crack healing, and the self-healing performance of the GGBS and SF was the highest. It was found that the subtle change in the self-healing performance was more accurately evaluated by the chloride ion penetration test.