Nanoindentation Characterization of a Ternary Clay-Based Composite Used in Ancient Chinese Construction.

Dongwei Hou,Jack Shen,Guoping Zhang,Hao Luo,Rohit Pant,Mingming Liu

doi:10.3390/ma9110866

Abstract

Ternary clay-based composite material (TCC), composed of lime, clay and sand, and usually modified with sticky rice and other organic compounds as additives, was widely used historically in Chinese construction and buildings due to its high mechanical performance. In this study, to gain an insight into the micromechanical mechanism of this cementitious material, the nanomechanical properties and volume fraction of mechanically different phases of the binder matrix are derived from the analysis of grid nanoindentation tests. Results show that there are five distinct mechanical phases, where the calcium silicate hydrate (C-S-H) and geopolymer present in the binder matrix are almost identical to those produced in ordinary Portland cement (OPC) and alkali-activated fly-ash geopolymer materials in nano-mechanical performance. The nano-mechanical behavior of calcite produced by the carbonation of lime in this binder is close to the calcite porous outer part of some sea urchin shells. Compared to OPC, the C-S-H contained in the TCC has a relatively lower ratio of indentation modulus to indentation hardness, implying a relatively lower resistance to material fracture. However, the geopolymer and calcite, at nearly the same volume content as the C-S-H, help to enhance the strength and durability of the TCC by their higher energy resistance capacity or higher strength compared to the C-S-H. Rediscovering of TCC offers a potential way to improve modern concrete’s strength and durability through synergy of multi-binders and the addition of organic materials if TCC can be advanced in terms of its workability and hardening rate.

Highlights

Significant carbon emissions and high energy consumption in the production of Portland cement, as well as the durability problems occurring in modern concrete materials and structures, have prompted increasing interest in the search for greener and more sustainable cementitious materials for construction
The main binder phases, calcite, calcium silicate hydrate (C-S-H), and geopolymer products were distinct, and in these the C-S-H and geopolymer present in the ternary clay-based composite (TCC) binder matrix were found to be almost identical to those produced in ordinary Portland cement (OPC) and alkali-activated fly-ash-based geopolymers, respectively, in nanomechanical performance, while the calcite produced by the carbonation of lime in TCC is close to the porous outer part of calcite in some sea urchin shells
Nuclear magnetic resonance (NMR) spectra suggested the presence of three-dimensional aluminosilicate networks, which are characteristic of geopolymer products [22]

Summary

Introduction

Significant carbon emissions and high energy consumption in the production of Portland cement, as well as the durability problems occurring in modern concrete materials and structures, have prompted increasing interest in the search for greener and more sustainable cementitious materials for construction. At least since the early Northern and Southern Dynasty (386–581 AD), organic constituents such as sticky rice soup, vegetable juice, egg white, brown cane sugar solution, tung oil, fish oil, and animal blood, have been introduced to improve the performance of the TCC materials significantly [6,8,9,10,11]. It may be the first widespread inorganic-organic composite mortar technology in China, or even in the world. Many surviving ancient Chinese structures, such as the Qiantang River Embankment, the Ming Dynasty City Wall, and the Hakka House, are still in service after many centuries, demonstrating TCC’s excellent durability

Methods

Results

Conclusion