A Review: Progress in Molecular Dynamics Simulation of Portland Cement (Geopolymer)—Based Composites and the Interface between These Matrices and Reinforced Material

Abstract

Molecular dynamics (MD) is an important method for studying the molecular and atomic scale of cement (geopolymer)-based composites which provides an effective method for the optimal design of cementitious materials. In this paper, the research progress of MD simulation in Portland cement and geopolymer-based materials is discussed in detail, including molecular structure models of calcium silicate hydrate, calcium aluminosilicate hydrate, sodium aluminum silicate hydrate gel, and auxiliary experimental techniques. The basic mechanical properties of calcium silicate hydrate, calcium aluminosilicate hydrate and sodium aluminum silicate hydrate in Portland cement-based materials (CBM) and geopolymer-based materials are reviewed. In addition, the dynamic simulation of the interface between CBM and reinforcement materials such as rebar, synthetic fibers, plant fibers and nanoparticles is also discussed. Through the macroscopic experimental results of cement (geopolymer)-based materials and the performance analysis of an MD microscopic model, MD helps to better explain the macroscopic properties of materials, and can quickly and conveniently analyze the mechanical properties, transport properties and interface properties of composite materials, so as to improve the fine design of cement (geopolymer)-based materials. Existing structural models and force fields are affected by environment and time, and MD simulation shows great differences in application range and characterization ability. It is necessary to further study and reveal the internal mechanism for improving concrete performance through a large number of experiments and MD simulation, and lay a theoretical foundation for preparing the next generation of (super) high-performance concrete.

Interaction Mechanism of Cementitious Composites Containing Different Twisted PVA Fiber Bundles

“…This study investigates four twist factors (0, 50, 100, 150) and three bundle numbers (1,2,3) to comprehensively analyze the effect of twist factors and fiber bundle numbers on the interaction mechanism of TLTP-FRCC. To examine the PVA fiber bundle used, environmental scanning electron microscopy (ESEM) [34] was utilized to observe the bundle at a microscopic level.…”

“…The silicate cement had weight percentages of approximately 2.59%, 1.46%, and 0.019% for SO 3 , MgO, and Cl − , respectively, and demonstrated 3-day bending and compressive strengths of around 6.5 MPa and 37 MPa, respectively. The fly ash had a density of about 1.3 g/cm 3 and a total weight percentage of approximately 77% for SiO 2 , Al 2 O 3 , and Fe 2 O 3 . The silica fume had a weight percentage of roughly 94% for SiO 2 .…”

“…Silicate cementitious composites are currently the most extensively employed materials in concrete structures, owing to their widespread availability, straightforward preparation, and superior mechanical properties [1,2]. However, these composites are frequently blended with other materials instead of being utilized independently due to their constrained mechanical properties for practical applications [3][4][5]. Fibers such as glass fiber, basalt fiber, forta-ferro fiber, coconut fiber, sisal fiber, steel fiber, and polyvinyl alcohol (PVA) fiber have been effectively used to reinforce silicate cement-based concrete [6][7][8][9][10][11][12][13].…”