Effect of storage condition on basic performance of polycarboxylate superplasticiser system incorporated sodium gluconate

Abstract

Abstract As the third-generation of superplasticiser, polycarboxylate (PCE) superplasticisers used in practical makes the concrete possible for some cases such as ultra-high building and constructions with long-distance transportation. During the on-site construction, the PCEs are normally placed in a storage tanks without any protection for a few days before they are used to produce concrete. Thus, the storage condition, including the temperature and time, would in most case influence the basic performance of the PCE. Moreover, sodium gluconate (SG), a hydroxycarboxylate, has been commonly used as retarder to synergistically improve the performance of PCE product. To fully understand the effect of the storage condition on the PCE system incorporated with SG, in this study, twenty cement pastes mixed with the PCE system which was stored under different temperature and time, were investigated via central composite design (CCD). The fresh properties, such as initial minislump, 1-hour minislump retention, and initial setting time of the cement pastes were examined and analysed as the responses of the CCD. Moreover, to fully understand the mechanism, the physio-chemical properties of the PCE were then determined via GPC, DLS and FTIR. The results showed that the storage condition, including temperature and time, obviously affected the performance of PCE system. Owing to the statistical analysis, the most satisfactory condition to obtain the best plasticising effect of PCE were stored at 49\u202f°C for 24\u202fh, with 0.15% of SG, and to achieve the best fluidity retention were 25\u202f°C for 124\u202fh, with 0.14% of SG. In addition, increasing the storage temperature and storage time could trigger the post-synthesis polymerisation of the PCE by increasing the molecular weight and conversion, which benefited the further performance of PCE. The addition of SG could provide contribution to fluidity and fluidity retention by grafting as the side chain of PCE. Such results can help us to obtain a holistic understanding to guide the application of the PCE in real engineering practice.