Mixture design and early age investigations of more sustainable UHPC

Abstract

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Investigating the early-age diffusion of chloride ions in hardening slag-blended mortars on the light of their hydration progress

“…The second peak, observed by other authors [23], characterizes the contribution of slag to the hydration reaction; this contribution is not readily apparent given that the studied materials are mortars and the binder volume is small. The curves plotted however reveal that the peak heat flow becomes flatter as slag content rises [23,35]. Table 4 indicates both the measured and normalized characteristic values of the isothermal microcalorimetry curves; the substitution of cement by 30% and 60% slag results in a decrease of 18% and 51% of the primary peak heat flow, respectively.…”

“…This phenomenon is directly correlated with the dilution effect of slag plus the fact that both hydraulic and pozzolanic reactions release less heat than Portland cement hydration [21,33,34]. The second peak, observed by other authors [23], characterizes the contribution of slag to the hydration reaction; this contribution is not readily apparent given that the studied materials are mortars and the binder volume is small. The curves plotted however reveal that the peak heat flow becomes flatter as slag content rises [23,35].…”

“…Nevertheless, their incorporation, notably in high volumes, greatly decreases the early-age performance of concrete. By virtue of their slow reaction, BFS particles decelerate the hydration reaction in a blended matrix and delay its rise in compressive strength [21][22][23]; moreover, the chemical shrinkage is decreased [24]. In the presence of this mineral admixture, the binder exhibits high porosity at an early age, which in turn raises the risk of aggressive agent ingress, as reported in [4].…”

Synthesis and characterization of a novel early‐strength polycarboxylate superplasticizer and its performances in cementitious system

“…At present, there are two main methods to obtain the early‐strength PCEs: on the one hand, compounding inorganic or organic accelerators of cement slurry with ordinary PCE to make up complex early‐strength PCEs, these accelerators include calcium chloride, sodium sulfate, calcium sulfate, calcium nitrate, triethanolamine, diethanolamine, and so forth; however, the complex early‐strength PCEs have certain restrictions in practice such as higher dosage, corrosive to the steel, storage instability, and may decrease the later strength of concrete . On the other hand, according to the designability of PCE molecular structure, the research idea that preparing novel early‐strength PCE and exploring the influence of PCE molecular structure on the cement hydration process has been adopted as the main development direction of early‐strength PCE . According to Yamada et al ., the concrete that included the PCEs with longer polyoxyethlene (PEO) side chains had significantly shorter setting time.…”

Synthesis of Alkali-Activated Binary Blended Silico-Manganese Fume and Ground Blast Furnace Slag Mortar

“…The quantity of potassium in SMF could be higher than 15% due to the presence of potassium aluminosilicate (KAlSi 3 O 8 ) (Najamuddin et al 2019) or other impurities, such as potassium feldspar generally occurring in manganese oxide ore (Zhong et al 2017). Abdulkareem et al (2018) reported that high K 2 O content could contribute to the strength in the presence of silica and lime in the OPC-based binder. However, the role of K 2 O in AAB synthesis co-existed with MnO in SMF and their synergy with BFS, is not yet fully elucidated.…”