Influence of Different Lithium Compounds on Hydration and Mechanical Properties of Calcium Sulfoaluminate Cement.

Hongyang Deng,Xinhua Cai,Shan Li,Xuanchun Wei,Shaoyan Liu

doi:10.3390/ma13163465

Abstract

This work investigated the influence of three different lithium compounds, lithium carbonate (Li2CO3), lithium sulfate (Li2SO4) and lithium chloride (LiCl), on the hydration and mechanical properties of calcium sulfoaluminate (CSA) cement mixtures. Five concentrations of Li+, 0, 0.05, 0.11, 0.16 and 0.22 mmol/g of cement, were chosen, and then the proportions (by mass) of three lithium compounds were determined. Compressive strengths at 8 h, 24 h and 28 days were tested. Meanwhile, an early hydration heat test, thermogravimetric (TG) analysis, X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques were performed to study the influences of different lithium compounds on properties of CSA cement mixtures. The experimental results show that three lithium compounds can all accelerate the early hydration process of CSA cement. There is not a remarkable difference on the properties of CSA cement pastes with a different content of Li+. The anion of lithium compounds can also affect the properties of CSA cement pastes, the accelerating effects of LiCl and Li2SO4 are more significant than that of Li2CO3, but there is not a distinct difference between LiCl and Li2SO4.

Highlights

Cement-based materials are the most used artificial materials in the world attributing to their favorable features such as low prices, reliable mechanical properties, high versatilities [1,2,3], etc
The early hydration acceleration caused by Li2 CO3 hindered the subsequent hydration of calcium sulfoaluminate (CSA) cement minerals to a certain extent
For the CSA cement pastes mixed with large concentration of lithium chloride (LiCl) and Li2 SO4, the compressive strength of 24 h can be higher than 30 MPa

Summary

Introduction

Cement-based materials are the most used artificial materials in the world attributing to their favorable features such as low prices, reliable mechanical properties, high versatilities [1,2,3], etc. As a kind of promising cement-based material [4], calcium sulfoaluminate (CSA) cement was developed in the 1970s [5], and manufactured by calcining natural materials such as limestone, bauxite and clay together with gypsum or anhydrite at 1250–1350 ◦ C, which is lower than Portland cement’s [6]. The main constituents of CSA cement are ye’elimite (3CaO·3Al2 O3 ·CaSO4 , C4 A3 S), belite (2CaO·SiO2 , C2 S) and calcium sulfate (anhydrite, CS; or gypsum, CSH2 ) [7,8,9]. In contrast to Portland cement, CSA cement has many advantages, such as low energy consumption during manufacturing, low CO2 emission, high early strength development and very good durability under normal service conditions, in marine construction [7,11,12,13].

Results

Discussion

Conclusion