Dilatancy mitigation of cement powder paste by pozzolanic and inert fillers

Abstract

Third generation polycarboxylate‐based superplasticiser (SP) can easily extend the maximum concurrent design limits of strength and flowability of concrete or cement paste, but simultaneously creates unfavorable dilatancy (or shear thickening) that decreases mixing efficiency and pumping range of concrete. The dilatancy is created initially by clustering of free and adsorbed polymers of SP, but further addition of SP can conversely mitigate the dilatancy by improved wet packing density. Because of the negative correlation of packing density and dilatancy, it is believed that partial replacement of cement by finer pozzolanic or inert filler can decrease the dilatancy via improved filling effect. Herein, the dilatancy of cement powder paste with or without pozzolanic fly ash or inert limestone powder replacing partial cement was studied using a coaxial rheometer. The results revealed that there exists a threshold limit of SP, beyond which the effect on dilatancy reverses. At a given SP dosage, partial cement replacement by either filler decreases dilatancy via improved packing density up to an optimal ratio, after which the dilatancy increases because the packing density reverses.

The effects of synthetic wollastonite developed with calcite and quartz on high performance mortars

“…Therefore, environmental and economic factors played an important role in the utilization of pozzolanic minerals such as blast furnace slag, silica fume, and fly ash as well as better performance in terms of strength and durability by improving microstructure of concrete 12–17 . Not only supplementary cementitious minerals (pozzolanic minerals) but also inert minerals can provide better filling effect for cement paste, mortar and concrete, 18 and also these minerals. One of them is wollastonite utilized as a reinforcing material/filler in cement‐based composites (concrete pavements, high strength concrete, cement board, etc.)…”

Characteristic properties of fly ash-based self-compacting geopolymer mortars with synthetic wollastonite microfiber produced from silica and calcite

“…SWM also decreased pores in the geopolymer matrix and water absorption and apparent porosity due to the filler effect by providing the condensation of the microstructure, which ensured pore discontinuity in the geopolymer matrix for Group I at high curing temperatures (22,23,42). Therefore, it was stated that SWM, defined as an inert material not reacting chemically in the pore solution, affected the formation of the pore network tortuosity of SCGs (43). However, this improvement was not observed in Groups II and III at lower and higher curing temperatures.…”

Impact of condensed silica fume on splitting tensile strength and brittleness of high strength self‐compacting concrete

“…Another reason was because of the increased dosage of SP for restoring the workability of concrete. 72 SP is known to create dilatancy that increases the viscosity and decreases flowability [73][74][75][76][77] of cement paste or concrete. Lastly, it can be seen from all V-funnel times in Table 3 that they exceed the minimum recommended value of 8 s for SCC stipulated by AFGC and EFNARC.…”