A comparative study of alkanolamines and inorganic additives on the microstructure development of blast furnace slag blended cement at low curing temperature

The initial reactivity and strength development of blast furnace slag cement (BFSC) are crucial factors that increase its utilization. Therefore, it is important to select the most suitable accelerator. In this study, the impact of four accelerators, namely sodium sulfate (Na2SO4), calcium nitrite (Ca(NO2)2), triethanolamine (TEA), and diethanolisopropanolamine (DEIPA), on the hydration and strength development of BFSC at curing temperatures of 5 and 20 degrees C was investigated. Isothermal calorimetry, X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) were conducted. The results revealed that Na2SO4 effectively enhanced early age strength by accelerating the hydration of the clinker and slag. Ca(NO2)2 is sensitive to temperature changes. At 20 degrees C, Ca(NO2)2 promoted the reaction of the aluminates and slag in the initial stage. However, the presence of slag inhibited clinker hydration, and the addition of Ca(NO2)2 exacerbated this effect, resulting in reduced strength at 5 degrees C. Indeed, the use of TEA and DEIPA at 0.02 % at 5 degrees C is not recommended. Complex interactions between TEA and Ca2+ may inhibit the formation of calcium hydroxide crystals, further inhibiting aluminate hydration. This may lead to low strength development at low curing temperatures such as 5 degrees C.

Automated summary

In this study, the impact of four accelerators on the hydration and strength development of blast furnace slag cement was investigated. The results showed that sodium sulfate effectively enhanced early age strength, while calcium nitrite had different effects at different temperatures. In addition, the use of TEA and DEIPA at 5 degrees Celsius was not recommended.