Influence of High-Robustness Polycarboxylate Superplasticizer on the Performances of Concrete Incorporating Fly Ash and Manufactured Sand

Using ethylene glycol monovinyl polyoxyethylene ether,2-acrylamido-2-methylpropane sulfonic acid(AMPS)and acrylic acid as the main synthetic monomers,a high robustness polycarboxylate superplasticizer was prepared.The effects of initial temperature,ratio of acid to ether,amount of chain transfer agent,and synthesis process on the properties of the superplasticizer were studied.The molecular structure was characterized by GPC(Gel Permeation Chromatography)and IR(Infrared Spectrometer).As shown by the results,when the initial reaction temperature is 15℃,the ratio of acid to ether is 3.4:1 and the acrylic acid pre-neutralization is 15%,The AMPS substitution is 10%,the amount of chain transfer agent is 8%,and the performance of the synthesized superplasticizer is the best.Compared with commercially available ordinary polycarboxylate superplasticizer in C30 concrete prepared with manufactured sand and fly ash,the bleeding rate decreases by 52%,T50 decreases by 1.2 s,and the slump time decreases by 1.1 s.In C60 concrete prepared with fly ash and river sand,the bleeding rate decreases by 46%,T50 decreases by 0.8 s,and the slump time decreases by 3.2 s.

Composition regulates dissolved organic matter adsorption onto iron (oxy)hydroxides and its competition with phosphate: Implications for organic carbon and phosphorus immobilization in lakes

Dissolved organicmatter(DOM)is a heterogeneous pool of compounds and exhibits diverse adsorption characteristics with or without phosphorous(P)competition.The impacts of these factors on the burial and mobilization of organic carbon and P in aquatic ecosystems remain uncertain.In this study,an algae-derived DOM(ADOM)and a commercially available humic acid(HA)with distinct compositions were assessed for their adsorption behaviors onto iron(oxy)hydroxides(FeOx),both in the absence and presence of phosphate.ADOM contained less aromatics but more protein-like and highly unsaturated structures with oxygen compounds(HUSO)than HA.The adsorption capacity of FeOx was significantly greater for ADOM than for HA.Protein-like and HUSO compounds in ADOM and humic-like compounds and macromolecular aromatics in HA were preferentially adsorbed by FeOx.Moreover,ADOM demonstrated a stronger inhibitory effect on phosphate adsorption than HA.This observation suggests that the substantial release of autochthonous ADOM by algae could elevate internal P loading and pose challenges for the restoration of restore eutrophic lakes.The presence of phosphate suppressed the adsorption of protein-like compounds in ADOM onto FeOx,resulting in an increase in the relative abundance of protein-like compounds and a decrease in the relative abundance of humic-like compounds in post-adsorption ADOM.In contrast,phosphate exhibited no discernible impact on the compositional fractionation of HA.Collectively,our results show the source-composition characters of DOM influence the immobilization of both DOM and P in aquatic ecosystems through adsorption processes.The preferential adsorption of proteinaceous compounds within ADOM and aromatics within HA highlights the potential for the attachment with FeOx to diminish the original source-specific signatures of DOM,thereby contributing to the shared DOM characteristics observed across diverse aquatic environments.