Application-Oriented Chemical Optimization of a Metakaolin Based Geopolymer

Abstract

In this study the development of a metakaolin based geopolymeric mortar to be used as bonding matrix for external strengthening of reinforced concrete beams is reported. Four geopolymer formulations have been obtained by varying the composition of the activating solution in terms of SiO2/Na2O ratio. The obtained samples have been characterized from a structural, microstructural and mechanical point of view. The differences in structure and microstructure have been correlated to the mechanical properties. A major issue of drying shrinkage has been encountered in the high Si/Al ratio samples. In the light of the characterization results, the optimal geopolymer composition was then applied to fasten steel fibers to reinforced concrete beams. The mechanical behavior of the strengthened reinforced beams was evaluated by four-points bending tests, which were performed also on reinforced concrete beams as they are for comparison. The preliminary results of the bending tests point out an excellent behavior of the geopolymeric mixture tested, with the failure load of the reinforced beams roughly twice that of the control beam.

Experimental and Numerical Analysis of Thermal and Hygrometric Characteristics of Building Structures Employing Recycled Plastic Aggregates and Geopolymer Concrete

“…The synthesis of geopolymers has been carried out starting from a wide variety of virgin raw materials, such as metakaolin [22][23][24], natural clays [25] and other natural silico-aluminates [26], as well as industrial process wastes such as coal fly ash [27][28][29] and metallurgical slag [30]. Geopolymer-based materials are attractive because excellent mechanical properties, high early strength, high durability, freeze-thaw resistance, low chloride diffusion rate, abrasion resistance, thermal stability and fire resistance, can be achieved [31][32][33]. Due to their lower Ca content, they are also more resistant to acid attack than Portland cement-based materials [34].…”

“…These experimental data have then been used in a numerical simulation code, based on finite elements, in order to reproduce the transient behavior of a typical building structure, characterized by a 3D field of the quantities of interest, defined as thermal bridge. This novel paper integrates the experiences of the authors belonging to research groups, working in two research areas: materials sciences [7][8][9][10]23,25,29,33] and thermal sciences [43][44][45][46][47][48].…”

Geopolymer/PEG Hybrid Materials Synthesis and Investigation of the Polymer Influence on Microstructure and Mechanical Behavior

“…They have been mainly proposed as more environmentally friendly substitutes of Portland cement 5,6 because of the greater energy efficiency of their manufacturing process and the substantial reduction in CO 2 emissions 7,8 . Following the particular aluminosilicate precursor 3 , the stoichiometric ratio of Si/Al [1,9] , alkali hydroxide and water content 10,11 as well as the reaction temperature, pressure 3 , activation, setting and curing procedures 11,12 , geopolymers can exhibit a wide variety of properties, such as high compressive strength, low shrinkage, fast or slow setting, acid and fire resistance, low thermal conductivity, long term durability and thermal stability. Thanks to these characteristics, geopolymers have a wide range of potential applications in construction building, in the biomedical field, in cultural heritage maintenance and renovation and immobilization of heavy metals and nuclear waste management.…”

Tensile behaviour of geopolymer-based materials under medium and high strain rates

“…GEO samples were obtained starting form an alkaline activating solution prepared by dissolving solid sodium hydroxide into a sodium silicate solution with a composition expressed as Na 2 O 1.4 SiO 2 10.5 H 2 O [12]. Then, metakaolin was incorporated into the activating solution with a liquid to solid ratio of 1.4:1 by weight, and mixed by a mechanical mixer for 10 min at 800 rpm.…”