Geopolymer is an inorganic polymeric material, which consists primarily of alumina, silica and alkali metal oxides. Geopolymer exhibits excellent adhesive, thermal, and chemical properties making them relevant in a diverse range of applications such as fire resistant materials, environment-friendly binders, composites for infrastructure repair/strengthening, radioactive waste containment, furnace molds etc. Geopolymer has lately been considered as an alternative to traditional Ordinary Portland Cement because of above mentioned properties as well as higher compressive strength, rapid strengthening, lower creep and shrinkage and a lower carbon footprint compared to OPC. Despite an increased interest in geopolymeric materials, use of geopolymer in construction has been restricted. An inadequate comprehension of the relation between composition and performance has been a big obstacle in the adoption of geopolymer-based materials in standards and building codes. In this study, we aim to understand the microstructure-strength relationships in geopolymer composites. The geopolymer precursor is an amorphous aluminosilicate gel and the plastic yield criterion is pressure sensitive owing to the nanoporous nature. Although the material is homogeneous at the macro scale, it is composed of the matrix, micro-pores, inclusions and unreacted phases at the meso-scale. It has been observed experimentally that factors like volume fraction, processing route and nature of the reinforcing material have a significant influence on the overall response of the composite at the macro-scale. To better understand the elasto-plastic behavior of geopolymers composites by connecting the meso- and macroscopic scales, non-linear analytical and computational models are developed. Depictive geometries of a representative elementary volume are created where filler is modeled as inclusions randomly dispersed in a homogeneous matrix. Uniaxial tests are performed using Finite Element Analysis to predict the overall strength response. The analytical upscaling model is developed within the framework of micromechanics using a Linear Comparison composite approach to predict the uniaxial tensile and compressive strength of the two phase composite, as a function of volume fraction of reinforcement. Both the approaches are validated against experiments on particle-reinforced and fiber-reinforced potassium-based geopolymer composites. The yield strength was found to increase with an increase in the filler volume fraction and filler aspect ratio. Stronger interface bonding and uniform filler distribution also enhanced strength characteristics. Our model enables virtual mechanical testing of geopolymer-based composites, thus accelerating the development of geopolymer as a future material.
|Original language||English (US)|
|State||Published - Jun 26 2017|