粉煤灰地聚物反应体系下的反应影响因素分析

Analysis of Reaction Factors Under Fly Ash Based Geopolymer System

以粉煤灰基地质聚合物为研究对象,研究了粉煤灰在地聚物反应体系下的反应影响因素。主要研究内容有:反应时间、反应温度和反应碱浓度对反应过程及宏观强度的影响及相关反应机理。结果表明:在反应中后期,粉煤灰反应速率明显下降而此时地聚物的宏观性能反而呈现最大值。以75℃为例,反应时间从24h延长到672h的过程中,反应程度仅从20.8%增加到了32.4%,平均反应速率仅为0.0179%/h,而此时样品的抗压强度则从1.31MPa增加到了7.98 MPa;在地聚物反应体系下,反应产物为无定形的硅铝胶凝体,该物质的致密程度与地聚物宏观性能直接相关;温度的升高可有效提高粉煤灰的反应速率及地聚物的宏观性能,促进无定形胶凝体的形成和硬化。反应24h,75℃下的反应程度和抗压强度可以达到20.8%和1.31 MPa,而同期35℃下的反应程度只能达到7.8%且尚未形成宏观强度;碱浓度的变化不仅可影响反应速率和宏观性能,还可改变粉煤灰在地聚物反应体系下的最终反应程度,在反应温度为75℃和50℃时,10 mol/L体系下672h的反应程度比5 mol/L体系分别高了90%和28.6%。

Focusing on the fly ash geopolymer,the reaction factors under fly ash based geopolymer system were studied.The effect of reaction time,reaction temperature and alkali concentration on reaction process,the effect of above factors on compressive strength,the reaction mechanism under fly ash based geopolymer system were analyzed.The results showed that during the latter part of the reaction,the reaction rate decreased while the compressive strength of geopolymer exhibited a maximum value.Taking75℃for example,when the reaction time extended from24h to672h,reaction degree only increased from20.8%to32.4%,the average response rate was only0.0179%/h.While,at the same time,the compressive strength of the samples raised from1.31MPa to7.98MPa.Under geopolymer reaction system,the reaction product was amorphous silica alumina gel and the dense of the gel was directly rela ted to the compressive strength of geopolymer.Increasing temperature could effectively increase the reaction rate and the compressive strength of the fly ash based geopolymer and promote the formation and hardening of amorphous gel.After reaction for24h,the reaction degree and compressive strength at75℃could reach20.8%and1.31MPa,while at35℃,the reaction degree could only reach7.8%without the formation of macroscopic strength.The changes of alkali concentration could not only affected the reaction rates and compressive strength,but also affec ted the finally reaction degree.At75℃and50℃,under10mol/L system,the reaction degree at672h were90%and28.6%higher than that of5mol/L system.