木质纤维碱激发地聚物胶凝材料的制备及力学性能研究

Preparation and Mechanical Properties Study on Wood Fiber Alkali-activated Geopolymer Cementitious Materials

地聚物因其较低的碳排放、优异的耐久性和力学性能日益受到关注,但其普遍存在收缩大、易产生脆性破坏现象,限制了其推广和应用。为改善地聚物的收缩性,提高其强度,研究了木质纤维含量对粉煤灰—矿渣地聚物物理性能和力学性能的影响,并对其微观组织进行了分析。研究结果表明,木质纤维含量达12.5 kg/m^(3)时,地聚物试块养护28 d干缩量为0.58 mm,相较于不添加木质纤维的地聚物胶凝材料试块降低了52.5%;木质纤维地聚物胶凝材料试块的抗折强度、抗压强度均随木质纤维掺量的增加先增大后减小,当木质纤维掺量为10 kg/m^(3)并养护28 d时,其抗折、抗压强度最大,分别为6.3、79.8 MPa,抗折、抗压强度分别达到了普通混凝土试块的C60、C80标准;掺入木质纤维可以显著提升地聚物胶凝材料试块的抗收缩性和力学性能,主要得益于其内在水分调节能力,在地聚物基体水化反应需要水分时释放储存的水分,维持反应连续性并促进产物形成,同时,高比表面积的木质纤维易与地聚物基体紧密结合,并使其成为增强相,从而在提高材料的抗收缩性和力学性能中发挥关键作用。

Geopolymers have attracted increasing attention due to their low carbon emissions,excellent durability and mechanical properties.However,they generally have large shrinkage and are prone to brittle failure,which limits their promotion and application.In order to improve the shrinkage and strength of geopolymer,the effect of wood fiber content on the physical and mechanical properties of fly ash-slag geopolymer was studied,and its microstructure was analyzed.The results show that when the wood fiber content reaches 12.5 kg/m^(3),the dry shrinkage of the geopolymer test block is 0.58 mm after 28 days of curing,which is 52.5%lower than that of the geopolymer cementitious material test block without wood fiber.The flexural strength and compressive strength of wood fiber geopolymer cementitious materials increase first and then decrease with the increase of wood fiber content.When the wood fiber content is 10 kg/m^(3) and cures for 28 d,the flexural strength and compressive strength are the largest,which are 6.3 MPa and 79.8 MPa,respectively.The flexural strength and compressive strength reach the C60 and C80 standards of ordinary concrete test blocks,respectively.The incorporation of wood fibers can significantly improve the shrinkage resistance and mechanical properties of geopolymer cementitious materials test block,mainly due to its inherent water regulation ability.When the hydration reaction of geopolymer matrix requires water,the stored water is released to maintain the continuity of the reaction and promote the formation of products.At the same time,the wood fiber with high specific surface area is easy to be closely combined with the geopolymer matrix and makes it a reinforcing phase,which plays a key role in improving the shrinkage resistance and mechanical properties of the material.