论文部分内容阅读
本工作旨在深入研究水泥的陈化对水泥与化学外加剂相互作用的影响。将Portland水泥分别暴露于35℃和相对湿度为90%的环境中1和3d。选取3种高效减水剂(萘系减水剂NSF、聚羧酸减水剂PCE和干酪素)、1种保水剂(MHEC,甲基纤维素)及两种促凝剂(甲酸钙和无定形氧化铝),研究了水泥与化学外加剂的相互作用。结果表明:水泥的陈化显著改变了新拌浆体的流动性、保水性与凝结行为。由于暴露过程中水泥表面部分水化,水泥的比表面积以及表面电荷均发生变化,进而影响了水泥与化学外加剂的相互作用。具体表现在以下3个方面:1)与新鲜水泥相比,减水剂在陈化水泥中的减水效果减弱,干酪素的分散能力略微降低,而PCE和PNS的分散能力均显著下降,尤其是PNS下降最大;2)陈化水泥呈现较好的保水能力和更高的需水量,因此,为了达到相同的保水效果,其所需的保水剂掺量较新鲜水泥低;3)在陈化水泥中,甲酸钙和无定形氧化铝的促凝效果显著下降,在水泥陈化3d后,这些促凝剂甚至可能延缓水泥水化。
This work aims to delve into the impact of cement aging on the interaction between cement and chemical admixtures. Portland cement was exposed to 1 and 3 days at 35 ° C and relative humidity of 90%, respectively. Three types of superplasticizers (NSF, PCE and casein), one super absorbent polymer (MHEC, methylcellulose) and two coagulants (calcium formate and none Shaped alumina), the interaction of cement with chemical admixtures was studied. The results show that the aging of cement significantly changes the fluidity, water retention and coagulation behavior of the fresh slurry. Due to the partial hydration of the cement surface during the exposure process, the specific surface area and surface charge of the cement both change, which in turn affects the interaction between the cement and the chemical admixture. Specific performance in the following three aspects: 1) compared with fresh cement, superplasticizer in the aging of cement in the water reducing effect of weakening the casein dispersion capacity decreased slightly, while the dispersion capacity of PCE and PNS decreased significantly, especially The PNS dropped the most; 2) The aged cement showed better water holding capacity and higher water demand, therefore, the required amount of water retaining agent was lower than fresh cement in order to achieve the same water retention effect; 3) In cement, the procoagulant effect of calcium formate and amorphous alumina decreased significantly, and even after 3 days of cement aging, these accelerators may even delay the hydration of cement.