Investigating the Mechanical Properties and Durability of Metakaolin-Incorporated Mortar by Different Curing Methods.

Yudong Dong,Lianjun Pei,Yalong Yang,Huihui Liang,Tong Liu,Jindong Fu,Hongjian Yang

doi:10.3390/ma15062035

Abstract

In this paper, the traditional, silicate-based Portland cement (PC) was employed as the control to explore the impact of adding varying amounts of metakaolin (MK) on the mechanical properties of cement mortar. In fact, as a mineral admixture, metakaolin (MK) has the ability to significantly improve the early strength and sulfate resistance of cement mortar in traditional, silicate-based Portland cement (PC). In addition to this, the performance of Portland cement mortar is greatly affected by the curing mode. The previous research mainly stays in the intermittent curing and alkaline excitation mode, and there are few studies on the influence of relatively humidity on it. Moreover, the paper investigated the impact of four different curing methods about humidity on the mechanical properties and sulfate resistance. The results show that the best content of metakaolin in Portland cement is 10% (M10), and the best curing method is 95% humidity in the first three days followed by 60% humidity in the later period (3#). Based on previous literature that suggests that adding MK thickens water film layer on the surface of mortar, the mechanism of MK increasing the early strength of cement was analyzed. The compressive strength of the Portland cement containing 10% MK (M10) after 1 day curing is 3.18 times that of pristine PC mortar, and is comparable if PC is cured for three days under the same curing conditions. The traditional PC mortar is highly dependent on the wet curing time, and normally requires a curing time of at least seven days. However, the incorporation of MK can greatly reduce the sensitivity of Portland cement to water; MK cement mortar with only three days wet curing (3#M10) can reach 49.12 MPa after 28 days, which can greatly shorten the otherwise lengthy wet curing time. Lastly, the cement specimens with MK also demonstrated excellent resistance against sulfate corrosion. The work will provide a strong theoretical basis for the early demolding of cement products in construction projects. At the same time, this study can also provide a theoretical reference for the construction of climate drought and saline land areas, which has great reference value.

Highlights

Ordinary Portland cement with its stable performance, less pollution, and high yield characteristics has been the most important and the most widely cement used in the building materials market
Ordinary Portland cement has the shortcomings of low early strength and late strength, but most of the previous studies only focus on the improvement of Portland cement late strength, rather than the early strength change
Because the hydration process of Portland cement is highly dependent on water, it is very important to explore the influence of different curing methods on it

Summary

Introduction

Ordinary Portland cement with its stable performance, less pollution, and high yield characteristics has been the most important and the most widely cement used in the building materials market. The early strength of ordinary Portland cement is a very important mechanical property index of cement products, which determines the demolding time, production efficiency and production cost of cement products. The early hydration process (in the first 7 days) of traditional Portland cement is highly dependent on water, and the required wet curing time is very lengthy [1,2]. It is necessary to find a suitable modifier to maintain the mechanical properties of Portland cement in a low humidity environment. Because the hydration process of Portland cement is highly dependent on water, it is very important to explore the influence of different curing methods on it

Methods

Results

Conclusion