Effects of hauling time on self-consolidating mortars containing metakaolin and natural zeolite

Abstract

Concrete should preserve its adhesion property and workability during the process of transportation to the construction site so that no sign of instability (e.g., bleeding and segregation of aggregates) takes place in concrete. In some cases, long-time mixing process of concrete in truck mixers and the imported energy caused by them inside this system may lead to workability loss or dynamic instability (as the essential factors affecting mechanical properties and durability) in the concrete, and this issue is deemed more important in self-consolidating concrete (SCC) that contains chemical and mineral additives. This study investigated the effect of hauling time and pozzolanic minerals on the fluidity, viscosity, stability, and compressive strength of self-consolidating mortars (SCMs). Therefore, 16 mix designs were totally made as binary and ternary mixtures, including metakaolin (MK) and natural zeolite (NZ), and were subjected to the prolonged mixing time (8, 30, 60, 90, 120, and 150 min). The results showed that when the hauling time increased up to a certain level, which is called stabilization time (the shortest mixing time that has been considered to be 30 min in this study), the fluidity and viscosity of mixtures increased and decreased, respectively. However, by prolonging the hauling time up to 150 min, the workability of binary and ternary mixtures will be reduced to 64% and 68%, respectively. Moreover, dynamic segregation resistance in all ternary mixtures was considered in a stable workability region after mixing for 90 min, while all mixtures were subject to high viscosity and high accumulation (at the center of mixture) at intervals of 120 min and 150 min. Moreover, when the hauling time increases up to 150 min, the compressive strength is reduced in binary mixtures with MK and NZ contents maximally to 54% and 57%, and this rate is equal to 67% in ternary mixtures.