High volume fly ash mortar containing nano-calcium carbonate as a sustainable cementitious material: microstructure and strength development

Huashan Yang,Faguang Leng,Yujun Che

doi:10.1038/s41598-018-34851-4

Huashan Yang, Faguang Leng + Show 1 more

Open Access

https://doi.org/10.1038/s41598-018-34851-4

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Abstract

The mechanisms underlying the effects of nano-calcium carbonate (NC) on the strength of high volume fly ash (FA) mortar are discussed. Two NCs are used as 2%, 4%, 6%, and 8% by weight of cementitious materials. Hydrated products of fly ash mortar containing NC was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG) and differential thermal gravity (DTG) analysis. Results indicate that NC could improve strength of FA mortar due to the more rapid growth of hydrated products induced by NC through additional nucleation sites. Corresponding to the highest measured strength of FA mortar, the optimal contents of NC are around 2%. In addition, the presence of 2% NC improved the microstructure of FA mortar after 180 days due to the formation of calcium carbonaluminate hydrate.

Highlights

The environmental impact of using ordinary Portland cement (PC) to produce concrete is primarily due to the approximately 7% of carbon dioxide emission[1,2,3,4]
This work studied the effects of nano-calcium carbonate (NC) on the strength development and microstructure of fly ash (FA) mortar
It can be concluded from the experiments in this study that: (1) Incorporating NC has positive effects on the strength of FA mortar at early ages and at later ages

Summary

Introduction

The environmental impact of using ordinary Portland cement (PC) to produce concrete is primarily due to the approximately 7% of carbon dioxide emission[1,2,3,4]. An overwhelming consensus has been reached on the use of mineral admixtures, such as FA, limestone powder, slag, and silica fume to replace the bulk portion of cement in concrete to reduce the carbon footprint of the concrete industry These mineral admixtures can improve both the mechanical properties and durability of cementitious materials at later ages[5,6,7,8]. Due to the presence of silicon oxide and aluminum oxide, FA can react with CH to form C-S-H and C-A-H These additional hydrated products fill the pores and form a denser matrix, and improve the strength and durability of concrete. It is pointed out that NC can compensate for the adverse effects of FA on the early-age performances of concrete, and promote the development of a more environmentally friendly, lower energy-intensive and cost-benefit ratio FA concrete[13]. Correspondence and requests for materials should be addressed to Y.C

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