Preparation and Formation Mechanism of High-Toughness Organic Polymers Modified Geopolymers

In recent years, geopolymers have shown potential to replace ordinary cement materials due to their simple preparation, low cost, and excellent performance. Adding organics to geopolymers can enhance toughness and broaden their application potential as building materials. However, the effect of common molding processes to enhance the toughness of organic polymers modified geopolymers remains very limited. In this study, high-toughness organic polymers modified geopolymers were prepared using vacuum-vibration-compaction (VVC) molding. The incorporation of 3-methacryloy loxypropyl trimethoxysilane (KH570) and sodium polyacrylate (PAAS), (KH-PAAS), was evaluated on the toughness system of the slag-based geopolymers. The micromechanical properties of the different hydrated phases were analyzed using a nano-scratch test (NST) and atomic force microscopy (AFM). The high fracture toughness (1.6-2.6 MPa*m0.5) and low elastic modulus (20-30 GPa) of the hydrated new phase C-(A)-S-H/Polymer gels were proposed. KH-PAAS modified geopolymers produced 57-59% C-(A)-S-H/Polymer gels in which C-(A)-S-H/Polymer gels, C-(A)-S-H gels, and KH-PAAS were planarly cross-distributed to form a 3D network structure. The toughness of KH-PAAS modified geopolymers is related to the amount of C-(A)-S-H/Polymer gels generation and distribution form. Finally, the formation mechanism of the C-(A)-S-H/Polymer gels was analyzed using time-of-flight secondary ion mass spectrometry (ToF-SIMS) to quantify the ratio of different chemical reactions. The specific ratio was C-(A)-S-H-KH: C-(A)-S-H-PAAS: Ca-PAAS: KH-C-(A)-S-H-PAAS = 2.42 : 6.78 : 47.58 : 1. This study provides ideas for subsequent investigation of the toughening mechanism of organic polymers modified geopolymers.