FDN减水剂对再生石膏性能的影响

Influence of FDN Superplasticizer on Properties of Recycled Gypsum

实验室模拟制备含萘系减水剂FDN的再生二水石膏样品,经煅烧得到再生半水石膏(RNP),对其进行了力学性能试验,并通过BET,DSC/TG及SEM-EDS研究了FDN对其性能的影响及作用机理.结果表明:相比未掺加FDN的原生半水石膏(POP)及其再生半水石膏(R-P),掺加FDN的原生半水石膏(PONP)及R-NP的力学性能均有所提高,且R-NP的强度提高幅度较大;相比POP和PONP,R-P与R-NP的力学性能均有所降低,且R-P的强度降幅更大;在POP中掺加FDN后,经过煅烧,FDN并未分解、脱附,且R-P的细度较大,有助于FDN的分散,使R-NP硬化体晶体发育完整,搭接紧密,孔径细化,孔隙率降低,而这正是减水剂提高R-NP硬化体强度的原因所在.

The recycled gypsum sample with naphthalene-type（FDN）superplasticizer added was prepared under the condition of laboratory simulation.The sample was dehydrated by calcination to hemihydrate and its mechanical properties were tested.The influence of FDN on the performance of recycled gypsum and its mechanism were investigated by BET,DSC/TG and SEM-EDS.The results show that the mechanical performance of plaster of Paris（PONP）and its recycled plaster（R-NP）with FDN are increased compared with the plaster of Paris（POP）and its recycled plaster（R-P）without FDN.The strength increasing rate of R-NP is much higher.The strength of R-P and R-NP both are decreased in comparison to POP and PONP,while the strength of R-P#is dropped much compared with that of R-NP.The analysis results indicate that the FDN still works in R-NP due to the undecomposition and adsorption of FDN during the recycled gypsum calcination,and the greater fineness of R-P also contributes to the dispersion of FDN,leading to the complete development of crystals and their close overlapping,which results in the decrease of porosity and average pore size.This is the very reason that superplasticizer reinforces its hardened R-NP.