不同工艺粉煤灰与外加剂适应性及机理分析

Adaptability and Mechanism Analysis on Fly Ash and Additives with Different Processes

采用净浆流动度方法,较为系统地研究了普通低钙灰、高钙灰、粉磨灰、脱硫灰、脱硝灰与萘系、聚羧酸减水剂的适应性,并通过SEM微观形貌、表观吸附及Zeta电位测试,初步分析了不同粉煤灰与外加剂适应性差异的原因。结果显示,粉煤灰对不同外加剂具有明显的选择性和适应性,外加剂掺量与粉煤灰需水量比正相关但无正比例关系;与普通低钙灰相比,脱硝灰具有同等的减水、保塑作用甚至更优,与外加剂适应性良好,粉磨灰、脱硫灰对初始掺量和经时流动性均有显著负效应,与外加剂适应性差;高钙灰与外加剂适应性不佳主要表现为增大经时损失;微观结构特性及未燃碳含量影响粉煤灰对外加剂的吸附和Zeta电位,从而影响不同粉煤灰与外加剂的适应性,高钙灰、脱硝灰具有与普通粉煤灰相似的微观形貌,对外加剂饱和吸附量小,因而适应性良好;粉磨灰、脱硫灰的粗糙表面以及较高含碳量造成大量外加剂的无效损耗,从而严重弱化外加剂与其适应性。

The adaptability of low-calcium fly ash, high-calcium fly ash, ground fly ash, desulfurized fly ash, denitrified fly ash with naphthalene and polycarboxylic superplasticizer was systematic researched by comparing cement paste fluidity method. The differences of adaptability between fly ash and admixtures are analyzed through SEM, adsorption and Zeta potential experiments. The results show that the fly ash has high selectivity and adaptability to different admixtures obviously. The amount of additive is positively correlated to water demand ratio, but not existed a proportional relationship.Compared with low-calcium fly ash, denitrified fly ash can adapt additives well by fine water-reducing, slump-remaining characteristic or even better in these aspects. Ground fly ash and desulfurized fly ash have bad adaptability to additives because they have a negative effect on initial fluidity and fluidity retaining. High-calcium fly ash also can ＇t adapt additives well because it makes the slump loss aggravated. The microstructure and unburned carbon content determined the adaptability of different fly ash and admixtures through the effect on adsorption and Zeta potential properties. High-calcium fly ash and denitrified fly ash can adapt additives well because they have the similar micro morphology and adsorption performance to ordinary fly ash, while ground fly ash and desulfurized fly ash have bad adaptability to additives for its rough surface and high carbon content increased additives serious loss.