偏高岭土-粉煤灰基地聚物砂浆力学性能研究

本研究以偏高岭土和粉煤灰为原料,以不同模数(0.75、1.00、1.25、1.50)和碱浓度(质量分数)(40%、44%、48%)的钾水玻璃为碱激发剂,微珠、蛭石和珍珠岩为细骨料来制备地聚物砂浆试件。主要通过测试地聚物砂浆试件常温及1 000 ℃高温作用后的抗压强度,探明碱激发剂模数和浓度对砂浆试件力学性能的影响,并利用XRD、SEM手段对地聚物的物相组成及微观形貌进行表征。结果表明:当碱浓度不变时,除40%碱浓度外,其余试件的抗压强度随模数的增大先升高后略微降低或者基本不变。当模数不变时,除模数为0.75的试件外,其余试件的抗压强度随碱浓度的增大先升高后降低。当模数为1.00且碱浓度为44%时,试件的抗压强度最高,历经1 000 ℃高温后地聚物砂浆试件相对残余强度仍能维持42%及以上,该温度下水化产物为白榴石(KAlSi₂O₆)和钾霞石(KAlSiO₄),地聚物在常温下有大量絮状的水化产物生成且微观结构较为致密。

Mechanical Properties of Geopolymer Mortar Based on Metakaolin and Fly Ash

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.