Abstract
HypothesisPolycarboxylate ether (PCE) comb-copolymers are widely used as water reducing agents in the concrete industry while maintaining a high fluidity via the polymer adsorption to the cement particles. PCE copolymers with a broad range of structures are well established by Free radical polymerization, however, understanding the structure-property relationship is still complex due to the high polydispersity of PCE copolymers prepared by conventional polymerization. The influence of different structural parameters using well-defined polymeric structures is yet to be explored. ExperimentsIn this study, two different types of comb-like random copolymers, namely polycarboxylate ether (PCE; poly(oligo(ethylene glycol) methyl ether methacrylate/methacrylic acid)) and polysulfonate ether (PSE; poly(oligo(ethylene glycol) methyl ether acrylate/sodium 4-styrenesulfonate)), were synthesized by RAFT polymerization to enable the synthesis of polymers with controlled features. The effect of charge types and side chain lengths on the adsorption, rheology, and dispersing ability of cement pastes have been studied. FindingsRAFT polymerization could be used to prepare PCE random copolymers with good control over the polymer molecular weight and narrow polydispersity (Đ < 1.3). Results revealed that the ζ-potential values depend on both the charge type and side chain lengths. Copolymers containing SO3− exhibited higher absolute negative ζ-potential values than COO− while PCE copolymers with shorter side chains developed higher absolute negative ζ-potential values. On the other hand, the adsorption study demonstrated that decreasing the side chain lengths lead to higher adsorption of PCE copolymers while Copolymers with COO− groups were found to be adsorbed more than SO3− counterparts. These results are further confirmed with the rheological studies and it is found that the shorter the side chain, the lower the yield stress and the higher the dispersion of cement pastes but to a limited effect. Additionally, the charge types have a major influence on the performance of superplasticizers. This study could make further progress in establishing superplasticizers with controlled architectures for better performance.
Highlights
Chemical admixtures are of high demand in concrete technology to enhance their properties such as durability, flowability, setting, and mechanical performance [1,2]
This work features the potential use of Reversible-addition fragmentation chain transfer (RAFT) polymerization to prepare well-defined PCE random copolymers as superplasticizers
In contrary to previous literature [16,17,19,53], that manipulated Free radical polymerization (FRP) as a tool to synthesize PCE copolymers without optimum chemical architectures, this study revealed that PCE random copolymers could be obtained with a narrow polydispersity (Ð < 1.3)
Summary
Chemical admixtures are of high demand in concrete technology to enhance their properties such as durability, flowability, setting, and mechanical performance [1,2]. Among these chemical admixtures, superplasticizers are mainly used to enhance the flowability at relatively low water-cement ratio (W/C) [3,4,5,6]. The first generation of superplasticizers (SP) such as sulphonated naphthaleneformaldehyde condensates (SNF) and amino sulphonateformaldehyde condensates (ASF) can disperse cement particles via electrostatic repulsion mechanism [3]. PCE copolymers can create both electrostatic repulsion and steric hindrance and they provide better performance than the older generations [9,10]. The molecular weight and side chain lengths of PCEs can be tailored, making them superior to other kinds of SPs
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
