Title:
A Comparative Study of Chemical and Physical Accelerators on Early Age Properties of Portland Cementitious Systems
Author(s):
Peerzada
Publication:
Web Session
Volume:
Issue:
Appears on pages(s):
Keywords:
DOI:
Date:
10/23/2022
Abstract:
The advancement in digital concrete technology, especially, additive manufacturing has changed the early-age requirements of cementitious systems. The cementitious system needs to have a very low stiffness (yield stress) in-line between the pump and the nozzle and on the other hand the printed matrix should gain stiffness rapidly for printing of subsequent layers. The control on the stiffness can be achieved through inline mixing of accelerators at the print head/nozzle. To choose the type and dosage of acceleartor which can give the desired stiffness control, a comprehensive study has been conducted. In this study, influence of two crystalline calcium silicate hydrate (C-S-H) nanoparticlebased accelerators, three tradition accelerators (chloride-based, two non-chloride) and shotcrete accelerators on early-age properties of Portland cementitious systems have been investigated through various techniques. The influence of rheology, hydration kinetics, setting time, phase evolution, compressive strength and restrained shrinkage have been studied for cement pastes and mortars with Binder fineness, water-binder ratio, accelerator type and dosage, sand-to-cement ratio, and temperature as variables. In addition to that, the study also investigates the efficacy of the chemical admixtures added inline. Results from the study show the effectiveness of the accelerators is a function of curing temperature, water-cement ratio, binder fineness etc. As the parameters are changed, the interaccelerator effectiveness changes.