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Effect of Sodium Tripolyphosphate on Clay Tolerance of Polycarboxylate Superplasticizer
Hongbo Tan,Yulin Guo,Baoguo Ma,Jian Huang,Benqing Gu,Fubing Zou 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.8
High fluidity concrete has been widely used in modern civil engineering project to ensure that the highly efficient construction process canbe achieved. Generally, the fluidity can be obtained with the incorporation of superplasticizer system composed of polymers and retarders. Sodium tripolyphosphate (STPP), a commonly used retarder in cement-based material, can obviously increase the dispersion ofpolycarboxylate superplasticizer (PCE), and this has been widely employed in real concrete. However, the effect of STPP on clay toleranceof PCE has not been confirmed until now, and it is still uncertain whether STPP in PCE system has positive or negative effect on workabilityof fresh concrete with poor-quality aggregates containing montmorillonite (Mt) which is one of the most harmful clay minerals. In this study,the effect of STPP on fluidity of cement-Mt paste with PCE has been investigated. The fluidity was tested with mini slump to assess the claytolerance of PCE. The adsorption amount of PCE and STPP in Mt suspension was tested with total organic carbon analyzer and inductivecoupled plasma emission spectrometer to characterize the adsorption behavior. The interlayer spacing was evaluated with X-rayDiffractometer and the structure of intercalated Mt by PCE was characterized with Fourier-transform infrared spectrometer and thermogravimetric analyzer, and these results were used to illustrate the effect of STPP on intercalation of PCE. Finally, the dispersion model wasproposed to reveal the mechanism behind. The results show that STPP can disperse the Mt particles and increase adsorption amount of PCEin Mt suspension, thereby accelerating rather than hindering the intercalation of PCE into Mt. The fluidity of cement-Mt paste with PCESTPPsystem is depended on the added dosage of STPP: with the dosage less than 0.20%, the contribution of STPP to dispersing the cementparticles predominates, hence increasing the fluidity of the paste and improving the clay tolerance; while with the dosage more than 0.20%,the acceleration of the intercalation of PCE resulting from STPP becomes predominant, thereby reducing the fluidity of the paste. This resultcan provide useful experience for the improvement in clay tolerance of PCE in real concrete with poor aggregate containing Mt.
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Fubing Zou,Hongbo Tan,Yulin Guo,Baoguo Ma,Xingyang He,Yang Zhou 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.55 No.-
Sodium gluconate is a commonly used retarder, and the incorporation of SG has been accepted as the most efficient way to improve the basic performance of polycarboxylate superplasticizer (PCE) system in real concrete. However, this improvement cannot be always achieved, and the main reason for this uncertainty is because the interaction between PCE and SG has not completely understood. In order to gain deeper insight into this interaction, adsorption behavior and dispersion mechanism of PCE-SG system involved in two kinds of PCE with different grafting density of carboxyl groups in side chain have been investigated. Specifically, the dispersion was assessed with the fluidity of the cement paste, and adsorption behavior was estimated with total organic carbon and zeta potential. The combination between PCE and SG was characterized with conductivity, dynamic light scattering, and X-ray photoelectron spectroscopy. Finally, several models were proposed to illustrate the mechanism behind. The results show that gluconate grafted as side chain of PCE and the increase in length of PEO chain caused by addition of SG can provide contribution to dispersion. Competitive adsorption between SG and PCE would take place to reduce the dispersion, and the declining degree depends on the relative adsorption between PCE and SG. Dispersion of PCE-SG is not only dependent on added dosage of SG, but also decided by molecular structure of PCE. This result provides guidance on how to promote the basic performance of the PCE-retarder system in real engineering practice.
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Zhenzhen Zhi,Jian Huang,Yanfei Guo,Siwen Lu,Baoguo Ma 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.5
Phosphorus Gypsum (PG) based Self-Leveling mortar (GSL) is a green and efficient material for floor construction. Its hydration kinetics, rheology property and their effect on mechanical strength of hydrated GSL were crucial to its final application. This study analyzed the effect on setting time of three retarders, namely Protein Salt (PS), Citric Acid (CA), and Sodium Tripolyphosphate (STPP). The fluidity of GSL was investigated individually using three different types of superplasticizer, namely naphthalene (FDN), polycarboxylate (PCE) and melamine (MSF). Finally, the effect of these chemical admixtures on mechanical properties of GSL hardened was examined. Results showed that the optimal contents of PS were 0.1%-0.15% by weight. With 0.1% PS, setting time of GSL retarded to 80min. To reach a maximum fluidity of GSL to 350mm, the optimal contents of PCE, MSF and FDN were 0.2%, 0.6% and 1.0% respectively and corresponding compressive strength of GSL were 54.25MPa, 53MPa and 52.25MPa. Suggesting PCE is the most effective dispersant in PG based GSL system.
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