Preparation of amphoteric polycarboxylate superplasticizers and their performances in cementitious system

Self Cite

We synthesized various polymers with different functional groups of ─COO − , ─SO 3 − , and ≡N + ─ to study the impact of the environmental temperature (25, 50, and 80 C) on the dispersing capability by measuring the fluidity of fresh cement paste, total organic carbon, ζ potential, and isothermal calorimetry. The results show that no adsorption was observed for the cement pastes containing acrylic acid, 2-acrylamido-2-methyl propane sulfonic acid, and [3-(methacryloylamino)propyl] trimethyl ammonium chloride, probably because of the trace amount of adsorption, whereas the fluidity of the pastes was indeed improved by the addition of these chemicals. Generally, for the polymers containing various functional groups, the adsorption capability was in the order ─COO − > ─SO 3 − > ≡N + ─. The dispersing capability for the carboxylate superplasticizer was robust to the change in the temperature, whereas it was dramatically weakened by the increase in temperature for sulfonate superplasticizer, although the adsorption amount increased along with the temperature rise.

Section: Resultssupporting

confidence: 93%

Fluidizing effects of polymers with various anchoring groups in cement pastes and their sensitivity to environmental temperatures

Tian

Kong

Sun

et al. 2019

Self Cite

“…The reasonable explanation is that when the AA/TPEG monomer ratio is less than 5.5:1, with increasing AA/TPEG monomer ratio, the PCEs have an increasing amount of free carboxylic groups and graft more PEO side chains that further strengthen electrostatic repulsive and steric hindrance effects between absorbed cement particles, and thus exhibit better dispersion effect. This explanation is supported by study data of Plank et al . However, the proportion of PEO side chains is correspondingly decreased when the AA/TPEG monomer ratio is too high, thus weaken the steric hindrance effect.…”

Section: Resultssupporting

confidence: 64%

Synthesis and characterization of a novel early‐strength polycarboxylate superplasticizer and its performances in cementitious system

Xia

Zhou

Ni³

et al. 2020

A novel early-strength type polycarboxylate superplasticizer (PCE) was synthesized by a new design of molecule structure such as introducing long polyoxyethlene side chains, functional monomer (2-acrylamide-2-methylpropanesulfonic acid), and optimizing monomer composition. In this study, with introducing the sulfonate groups into PCE structure, its dispersion capacity and the absorbed amount are increased firstly and then decreased, but the retardation hydration effect is weakened gradually. The molecular weight, adsorbed amount, and dispersion capacity of PCEs firstly increased and then decreased with increasing the AA/TPEG monomer molar ratio, and the same trend as the compressive strength harden concrete with PCEs at the age of 1, 3, and 28 days. The early-strength type PCE exhibits good dispersive capacity and weak retardation hydration effect in cementitious system, and the early age strength of concrete with addition of early-strength type PCE develops quickly. This study indicates that reasonable design of PCE molecule structure and synthesis method can obtain a novel early-strength type PCE which makes a good balance between workability and fast development of early age strength in cementitious system.

“…with molecular weight cut off of 3500 Da. The dialysate was renewed every 3 h. Thus, residual monomers were effectively removed from the sample . Employing a vacuum freeze dryer apparatus (BenchTop Pro, VirTis, New York; condensation temperature of −55 °C, vacuum pressure of less than 20 Pa), the copolymer was freeze‐dried for 48 h, yielding a white powder after grinding.…”

Section: Methodsmentioning

confidence: 99%

Hydrophobic associated copolymer as a wide temperature range synthetic cement retarder and its effect on cement hydration

Xia

Guo

Chen

et al. 2017

Hexadecyldimethylpropylmethacrylamide ammonium bromide was well prepared, allowed to copolymerize with other functional monomers to develop a hydrophobic associated polymer (PIADH) as a wide temperature range cement retarder. The synthetic copolymer was testified by Fourier transform infrared spectroscopy, 1 H-nuclear magnetic resonance, thermo gravimetric analysis, and differential scanning calorimetry. Its temperature induced adaptability was verified via fluorescence probe and NaOH titration techniques, indicating that the retarding groups were increasing at elevated temperature. The applied performance of PIADH modified cement slurries was also evaluated. The results manifested that PIADH not only had excellent retarding property, but also was insensitive to its concentration and temperature variations. Meanwhile, it exhibited less impact on the compressive strength of set cement in large temperature difference. Besides, the inclusion of PIADH improved the microstructure of hardened cement, which was conducive to its mechanical property. The effect of PIADH on cement hydration was also investigated by the isothermal heat flow calorimetry and X-ray diffraction, showing that the retardation of PIADH was achieved through prolonging the induction period and inhibiting the nucleation of portlandite and ettringite crystals.