Mechanical Properties of Geopolymer Mortar Based on Metakaolin and Fly Ash

Abstract

Abstract: In this study, geopolymer mortar specimens were prepared with metakaolin and fly ash as raw materials, potassium sodium silicate with different modulus (0.75, 1.00, 1.25, 1.50) and alkali concentration (mass fraction) (40%, 44%, 48%) as alkali activator, and microbeads, vermiculite and perlite as fine aggregate. The compressive strength of geopolymer mortar specimens at room temperature and 1 000 ℃ high temperature were tested, the influences of the modulus and concentration of alkali activator on the mechanical properties of mortar specimens were explored, and the phase composition and micro-morphology of geopolymer were characterized by XRD and SEM. The test results show that when the alkali concentration is unchanged (except concentration of 40%), the compressive strength of most specimens increase first and then decrease slightly or remain basically unchanged with the increase of modulus. When the modulus remains unchanged (except modulus of 0.75), the compressive strength of most specimens increase first and then decrease with the increase of alkali concentration. When the modulus is 1.00 and the alkali concentration is 44%, the compressive strength of the specimen is the highest. After 1 000 ℃ high temperature, the relative residual strength of the sample still maintains at 42% or above. The hydration products after 1 000 ℃ are leucite (KAlSi₂O₆) and potassiumnephritic (KAlSiO₄). And a large number of flocculent hydration products are formed at room temperature and the microstructure is relatively compact.

Key words: geopolymer based on metakaolin and fly ash, mortar, compressive strength, alkali concentration, modulus, high temperature, microstructure

CLC Number:

TU526

GUAN Bolun, GUO Rongxin, QI Rongqing, FU Chaoshu, ZHANG Min, ZHANG Wenshuai. Mechanical Properties of Geopolymer Mortar Based on Metakaolin and Fly Ash[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2021, 40(4): 1250-1257.

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