Mechanism Analysis of the Influence of Delay Period on Mechanical Properties of Reactive Powder Concrete

Xiaohui Wang,Qingxin Zhao,Xiaojun He,Shuang Zhang

doi:10.3389/fmats.2020.563234

Abstract

In order to analyze the influence mechanism of delay period on the mechanical properties of reactive powder concrete (RPC), the compressive strength of RPC with delay periods of 18, 24, and 30 h was tested at the age of 7, 28, and 90 days, respectively. The results show that compared with the RPC with delay period of 18 h, the compressive strength of the RPC with delay periods of 24 and 30 h increases by 3.2 and 4.2%, respectively, and the long-term strength reduction ratio decreases by 22.8 and 71.9%, respectively. The constitutive model curves of RPC under different delay period show that the initial elastic modulus E increases with the delay period and the strength and rigidity of RPC increase with the extension of delay period. According to the non-evaporation water quantity test, it could be speculated that the quantities of hydration products of the RPC with delay periods of 24 and 30 h slightly increase compared with the RPC with delay period of 18 h. X-ray diffraction (XRD) analysis show that the delay periods of 24 and 30 h consume more 3CaO·SiO2 (C3S) and 2CaO·SiO2 (C2S) compared with delay period of 18 h. Seen from the scanning electron microscope (SEM) image, the structures of the three groups of samples are relatively dense and have no significant difference. Through energy dispersive X-ray spectroscopy (EDS) analysis, the calcium-silicon ratios of hydration products of the RPC with delay periods of 18, 24, and 30 h are 1.81, 1.56, and 1.54, respectively. The existence of C-S-H gel and Ca(OH)2 in hydration products is confirmed by thermogravimetric-differential scanning calorimetry (DSC-TG) analysis. An appropriate delay period (30 h in this paper) generates more hydration products, then improves the compactness of the internal structure and reduces the calcium-silicon ratio of hydration products, and it is conducive to the growth of RPC compressive strength and the stability of long-term compressive strength.

Highlights

Reactive powder concrete (RPC) is a new type of concrete prepared by steam curing, which has removed the coarse aggregate to improve uniformity of the matrix (Abid et al, 2017)
The results showed that the strength of reactive powder concrete (RPC) was the highest when the delay period was 6 h, and the length of the delay period obviously affected the mechanical properties of RPC
The difference of compressive strength under different delay period was analyzed by one-way analysis of variance

Summary

Introduction

Reactive powder concrete (RPC) is a new type of concrete prepared by steam curing, which has removed the coarse aggregate to improve uniformity of the matrix (Abid et al, 2017). It was shown that the compressive strength of RPC at the age of 90 days had statistically significant difference with the prolongation of delay period.

Results

Conclusion