Effects of Nano-SiO2 and SAP on Hydration Process of Early-Age Cement Paste Using LF-NMR

Haitao Zhao,Ruiming Jia,Yi Wan,Jun Xie,Kaidi Jiang,Xiaodong Chen,Gaoyang Sun,Shihai Li,Donghui Huang

doi:10.1155/2020/6089482

Abstract

The effects of nano-SiO2 and superabsorbent polymer on the hydration process of early-age cement paste are investigated through the physically bound water evolution test by means of the low-field nuclear magnetic resonance technology. The test results show that the hydration process can be characterized by four-stage patterns based on the zero points of the second-order differential hydration curve, i.e., the initial, accelerated, decelerated, and steady periods. The beginning time of each stage is postponed and the hydration duration is prolonged with an increasing water to cement ratio. The beginning time of each stage and the hydration duration are shortened with an increasing content of nano-SiO2. And the beginning time of each stage and the hydration duration are prolonged with an increasing content of superabsorbent polymer. Based on the test data and the Avrami–Erofeev model, a modified hydration model taking the influence of nano-SiO2 and SAP into account is proposed, and the predicted results are consistent with the test results.

Highlights

Nanomaterials had been increasingly used in the construction and building materials with the rapid development of nanomaterials
The internal humidity field is closely related to the early-age crack of cement-based materials (CBMs) [5]. e internal curing (IC) of CBM can improve the internal humidity field in CBM [6]. erefore, the IC method can mitigate the autogenous shrinkage (AS) and the early-age crack risk of CBM
Sneff et al [14] investigated the effects of NS on the hydration heat of cement paste and the results suggested that the addition of NS made the peak of cement hydration heat increased, the arrival time of hydration heat peak shortened, and the reaction rate accelerated obviously

Summary

Introduction

Nanomaterials had been increasingly used in the construction and building materials with the rapid development of nanomaterials. Previous studies have shown that the addition of nanomaterials can effectively enhance the physical and mechanical properties of cement-based materials (CBMs) [3, 4]. Erefore, the addition of SAP to the NS CBM can ensure the hydration of the cement paste more completely and decrease self-shrinkage. Some researches have been conducted on the hydration process of CBM with the addition of SAP. Low-field nuclear magnetic resonance (LF-NMR) is applied to monitor the physically bound water content in the cement paste on the ground of proton relaxation characteristics of water molecules and to characterize the hydration of cementitious materials [20, 21]. The influences of water-to-cement ratio (w/c), NS, and SAP on the hydration process of the cement paste were studied by employing LF-NMR. A prediction model of hydration taking the influences of NS and SAP into account was proposed

Materials and Methods

Results and Discussions

Hydration Model

Conclusions