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Advances in Materials Science and Engineering
Volume 2017 (2017), Article ID 1264590, 9 pages
https://doi.org/10.1155/2017/1264590
Research Article

Preparation and Performance of a New-Type Alkali-Free Liquid Accelerator for Shotcrete

1School of Materials Science and Engineering, Chang’an University, Xi’an 710064, China
2School of Highway, Chang’an University, Xi’an 710064, China
3College of Architecture and Civil Engineering, Xi’an University of Science and Technology, Xi’an 710054, China
4Qinghai Research Institute of Transportation, Xining 810008, China

Correspondence should be addressed to Bin Xue

Received 1 March 2017; Accepted 20 April 2017; Published 17 May 2017

Academic Editor: Aboelkasim Diab

Copyright © 2017 Yanping Sheng et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

A new type of alkali-free liquid accelerator for shotcrete was prepared. Specifically, the setting time and strength and shrinkage performance of two kinds of Portland cement with the accelerator were fully investigated. Moreover, the accelerating mechanism of alkali-free liquid accelerator and the hydration process of the shotcrete with accelerator were explored. Results show that alkali-free liquid accelerator significantly shortened the setting time of cement paste, where the initial setting time of cement paste with 8 wt% of the accelerator was about 3 min and the final setting time was about 7 min. Compressive strength at 1 day of cement mortar with the accelerator could reach 23.4 MPa, which increased by 36.2% compared to the strength of cement mortar without the accelerator, and the retention rate of 28-day compressive strength reached 110%. In addition, the accelerator still shows a good accelerating effect under low temperature conditions. However, the shrinkage rate of the concrete increased with the amount of the accelerator. 5~8% content of accelerator is recommended for shotcrete in practice. XRD and SEM test results showed that the alkali-free liquid accelerator promoted the formation of ettringite crystals due to the increase of Al3+ and concentration.