关键词: 石灰石-煅烧黏土-水泥, 煤矸石, 高岭土, 力学性能, 水化产物

Abstract: Two calcined clay minerals (namely coal gangue and metakaolin) were blended to adjust the kaolinite content in calcined clay. This process was employed to prepare limestone-calcined clay-cement (LC³) with 50% (mass fraction) clinker content. The mechanical property and hydration product evolution of LC³ with calcined clay containing 20% to 90% (mass fraction) kaolinite were investigated using a variety of analytical techniques, including compressive strength tests, hydration exothermic analysis, X-ray diffraction (XRD), thermogravimetric analysis (TG), and thermodynamic simulations. The results show that the increase of kaolinite content promotes the reaction between calcium carbonate and aluminate in calcined clay, and consumes calcium hydroxide and ettringite generated during the hydration of cement clinker. When the content of kaolinite increases from 20% to 60%, the mechanical properties of LC³ gradually increase, and the 28 d compressive strength increases by 33.99%. The amount of C-(A)-S-H gel, ettringite and carboaluminate in hydration products increases, and the degree of clinker reaction decreases from 89.09% to 82.08%. When the kaolinite content exceeds 60%, with the further increase of kaolinite content, the decrease of clinker reaction degree and the increase of compressive strength obviously slow down, and the 28 d compressive strength only increases by 2.77 MPa. The content of carboaluminate in hydration products increases, but the increase is relatively limited. At the same time, the thermodynamic simulation results show that the content of C-(A)-S-H gel decreases.

Key words: limestone-calcined clay-cement, coal gangue, kaolin, mechanical property, hydration product