Optimizing the Properties of Metakaolin-based (Na, K)-Geopolymer Using Taguchi Design Method

Abstract

Geopolymer paste is an innovative construction material which shall be produced by chemical action of inorganic molecules. It is a more environmentally friendly alternative to conventional Portland cement which is abundantly available worldwide. In this study, the influence of different alkaline activators (Na and K) on the mechanical and thermal behaviors of metakaolin-based geopolymer was investigated. The aims of this study is to find out the mixes and their process parameters, which are appropriate to produce Geopolymer paste with one of the highest compressive strength, highest-lowest porosity and highestlowest initial and final setting time. Taguchi method is used in the design of the experiments for the metakaolin-based Geopolymer. Five factors were selected as process parameters that are more likely to affect the Geopolymer characteristics. These are the amount of Si, alkali type, alkali reagents ratio, mixing time, and water content. The effect of these parameters on the setting time, density, porosity, compressive strengths at 7 and 28 days. The results of study found that the Geopolymer paste with high compressive strength of (107.2MPa) can be obtained with the formula (0.2K2O.0.8Na2O. Al2O3. 3.6SiO2.xH2O) using proper processing condition in which the alkali silicates to the alkali hydroxides molar ratio should be kept in the range of 2.26. The results revealed that the use of alkali solution of Kions and Na-ions improves the compressive strength of the geopolymer remarkably as compared with the use of Na-ions solution along. In addition, it has been noticed that the setting time is reduced, for geopolymers with silica content of less than 3.8, when K-ions is used. Similarly, the bulk density of geopolymers is found to be reduced by adding K-ions.

A Novel Lightweight Phase-changing Cooling Roof Tile

“…Metakaolin is widely used in mortar and concrete as pozzolanic material; it has a significant impact on improving the mechanical and durability properties of mortar and concrete [23][24][25][26]. Because of its highly amorphous structure, is known as the most reactive material for the geopolymerization process.…”

Taguchi- Grey relational analysis for Optimizing the Compressive Strength and Porosity of Metakaolin-Based Geopolymer

“…It is well known that the pores inside the material reduces the mechanical strength of the geopolymer [25,26]. On the other hand, in the many applications were desired to have a material that combines high porosity and high mechanical strength.…”

“…Usually it can only consider single quality characteristics. While, Grey Relational Analysis (GRA) is usually employed to deal with the multi-quality characteristics [26]. This is because, GRA is a normalization evaluation technique to solve a complicated multi-performance characteristics optimization effectively [27].…”

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“…This value seemed to be reasonable because the value of R + cations provide the positive charge that stabilizes the negative charge came from Al 3+ in tetrahedral sites, leading to geopolymer formation [9,10]. The effect of mixed alkali geopolymer on compressive strength instead of one type pure alkaline was studied by researchers like Duxson et al (2007) who observed that the use of mixed alkali of Na and K in geopolymer synthesis with Si/Al≥1.90 can increase the compressive strengths compared with geopolymer specimens contain Na or K, the later specimens decrease strength notably [11,12]. The compressive strength of geopolymer is time dependent property due to it increased with time increased [12].…”