The molecular structures and the application properties of sulfonated acetone-formaldehyde superplasticizers at different synthetic methods

Nowadays, Superplasticizers (SPs) are the basic component to produce the concrete. In this study, the water-soluble sulfonated acetone-formaldehyde (SAF) SP was prepared at different synthetic methods (SAF-1, SAF-2). The molecular structures and the application behaviors of SAF-1, SAF-2 SPs in the concrete were evaluated. The molecules of SAF-1, SAF-2 SPs have the same –OH, –CH₂, –C[dbnd]O, –SO₃ groups. However, SAF-1 SP has the larger weight-average molecular weight (M_n), the number-average molecular weight (M_w), the polydispersity index (PDI) and the higher sulfonic group content than SAF-2 SP. The larger water-reducing ratio, the better fluidity preservation, the longer setting times, the larger bleeding water rate, wet density and mechanical behaviors of the concrete than those with SAF-2 SP can be found in the SAF-1 SP-blended concrete mixtures. The differences in the air content of the SAF-1, SAF-2 SPs series concrete are insignificant. Therefore, it is an effective method to prepare SAF SP using sodium pyrosulfite as sulfonating agent at four-step processes.