粉煤灰对煤矿充填膏体性能的影响

为探讨粉煤灰对煤矿充填膏体性能的影响,试验采用坍落度试验和流变试验综合评价膏体流变性,通过干缩变形研究其长期稳定性及对接顶性能的影响,研究了水泥、煤矸石用量及膏体浓度不变的情况下粉煤灰掺量64.2%~69.8%,膏体流变性、泌水率、抗压强度和干缩率的变化情况。结果表明:1随粉煤灰掺量的增加,膏体流变性减弱,黏聚性增强,泌水率减小。2随粉煤灰掺量的增大,不同龄期膏体抗压强度变化不同,3 d强度变化不大,在0.5 MPa左右;7 d强度呈先增后降的趋势,在66.7%掺量时最大达到2.5 MPa;14 d强度于67.8%掺量前在4 MPa上下变化,在68.9%掺量时达到6.9 MPa;28 d强度发展缓慢,与14 d变化趋势相似。7~14 d水化作用显著,强度增长量能达到28 d强度的40%~60%。3膏体的干缩量随粉煤灰用量增加而减小,与龄期近似满足对数关系。且膏体干缩量曲线160 d开始趋于平稳,干缩率不超过0.2%。

Influence on performance of coal mine filling paste with fly ash

To study the effects of fly ash on the properties of coal mine filling paste，a slump test and a rheological test were used to evaluate rheological property，and dry shrinkage deformation was measured to study the long term stability and the influence of contact with roof.The rheological property，bleeding index，compressive strength and dry shrinkage were studied with different dosages of fly ash from 64.2% to 69.8% under the condition of invariable mass concentration and the same dosage of cement，coal gangue of filling paste.With the increased dosage of fly ash，the results show that： ① Rheological property abates，adhesiveness enhances，and bleeding index decreases；② Different curing ages of filling paste has different compressive strength variations：3 d strength has little variation at about 0.5 MPa.The trend of 7 d strength is initial increase and then drop，the maximum strength is 2.5 MPa at 66.7% dosage of fly ash；14 d strength is about 4 MPa before 67.8% dosage of fly ash，it reaches 6.9 MPa when at 68.9% dosage of fly ash.The variation of 28 d and 14 d strength are similar.There is a significant hydration from 7 d to 14 d，which can generate from 40% to 60% of 28 d strength of filling paste；③ The dry shrinkage of filling paste decreases，obeying logarithmic relationship with its age approximately.Dry shrinkage curve of 160 d leveles off，and the dry shrinkage rate is less than 0.2%.