Hydration of Early Age Cement Paste with Nano-CaCO3 and SAP by LF-NMR Spectroscopy: Mechanism and Prediction

Haitao Zhao,Gaoyang Sun,Yi Wan,Shihai Li,Kaidi Jiang,Lu Yu,Ruiming Jia,Xiaodong Chen

doi:10.1155/2019/8384051

Abstract

In this paper, by testing the evolution of the physically bound water using the low-field nuclear magnetic resonance (LF-NMR) technology, the hydration process of cement paste with nano-CaCO3 (NC) and superabsorbent polymer (SAP) at early age is investigated. Results indicate that the hydration process can be divided into four periods according to the zero points of the second-order differential hydration curve: initial period, acceleration period, deceleration period, and steady period. Firstly, with the increase in the water to cement ratio, the starting time of the hydration period is delayed, and the duration becomes longer. Secondly, the addition of NC leads to the speedy arrival of each period and shortens the duration of each period in the hydration process, and the optimal NC content is 1.5%. Thirdly, with the increase in SAP content, the starting time of the hydration period is delayed and the duration becomes longer. Finally, based on the experimental results and the existing hydration model, the modified hydration model considering the content of NC and SAP is proposed.

Highlights

Concrete is the most widely used man-made construction material in the world, and the mechanical property and durability are focused in recent studies [1,2,3,4,5]
Internal curing with superabsorbent polymer (SAP) is an effective method to reduce the decrease in internal relative humidity by supplying additional water [15] and to prevent the detrimental effects of shrinkage by producing a dense crack-free microstructure [16]
E influencing factors of the hydration are selected as w/c, NC content, and SAP content. e NC content is 1.0%, 1.5%, 2.0%, and 3.0% replacing the cement by weight. e dosage of SAP is 0.15% and 0.30% by mass of cement, and the w/c ratios are 0.30, 0.35, and 0.40

Summary

Introduction

Concrete is the most widely used man-made construction material in the world, and the mechanical property and durability are focused in recent studies [1,2,3,4,5]. Nanomaterials, as products of nanotechnology, are defined as materials with particle sizes less than 100 nm and have many superior properties that differ from traditional materials [6, 7]. Nanomaterials can enhance the physical and mechanical properties of the cement-based materials effectively, reduce the porosity, and help in manufacturing the concrete with better performance [8]. Traditional external curing methods are not effective because the curing water penetrates only the surface layer of the concrete [14]. Internal curing with SAP is an effective method to reduce the decrease in internal relative humidity by supplying additional water [15] and to prevent the detrimental effects of shrinkage by producing a dense crack-free microstructure [16]

Methods

Results

Conclusion