Papers by Keyword: Polycarboxylate

Abstract: Water-soluble polymer and latex additives are used to give the gypsum building plaster elasticity and placeability, improved water resistance and increased bending strength. The nanomodifiers in the form of carbon single-layer and multi-layer nanotubes, fullerenes and other nanoparticles are used for the formation of the structure of a gypsum stone with improved strength characteristics and improved weather resistance. In this work, the joint effect of the plasticizer based on polycarboxylate and the carbon nanomodifier on the structure, physicomechanical properties, and water resistance of the gypsum stone is investigated. It is shown that nanomodifiers contribute to the increase in the plasticizing ability of carboxylate additives, which leads to the significant decrease in the amount of mixing water, and as a result, to the increase in density, decrease in the porosity of the gypsum stone and the increase in its strength characteristics and water resistance.

Abstract: This article uses hydroxylethyl acrylate and phosphorylation reagent for esterification reaction, synthesis of a phosphate ester monomer with double bonds, and phosphate ester monomer ,Participation as the third monomer polymerization of acrylic acid and isoprene polyoxyethylene ether (TPEG). Polycarboxylate was synthesized with phosphoric acid ester structure,Investigate the impact of Phosphate ester content in single and double to polycarboxylate performance. The results showed that the polycarboxylate with phosphate structure has excellent adaptability and reduction of water slump performance.

Abstract: In order to study the suppression effect of increasing concrete shrinkage induced by limestone powder, the aliphatic water reducer and polycarboxylate superplasticizer was used in experiments about effect of limestone powder content on concrete shrinkage. The results showed that the concrete shrinkage increased as the limestone powder content increasing. Comparing to the aliphatic water reducer, the polycarboxylate superplasticizer showed obviously effect on concrete shrinkage suppression. Besides, the polycarboxylate superplasticizer can reduce the sensitivity of concrete cracking. The polycarboxylate superplasticizer using in concrete can effectively reduce the emission amount and environmental pollution in the production process of artificial sand, simultaneously, this is helpful to improve the volume stability of concrete.

Abstract: Polycarboxylate was synthesized and the structure of the superplasticizer was characterized by FTIR. The water reducing effect of the synthesized copolymers was studied in terms of stirring time, the surface tension of superplasticizer and the adsorption on cement particles of superplasticizier. For all the samples tested in this research, increase in stirring time caused an increase in fluidity. The surface tension of the product solution (1wt%, w/w) is 51.2536 mN/m and the maximum value of adsorption was at about 2.6 mg/g at the concentration of 6wt%.

Abstract: There existed a competitive adsorption of polycarboxylate (PC) molecular between cement particles and clay particles, and the amount of effective adsorption of PC on the cement particles was decreased. The clay particles carry a negative charge, so the Ca²⁺ that produced by the hydration of cement clinker minerals could be adsorbed. The positive charge density on the surface of cement particles was decreased. The amount of effective adsorption of PC on the cement particle surface was also decreased. The basic reason of the reduction of water-reducing rate of PC was the decreased of the amount of effective adsorption of PC on the cement particle surface.

Abstract: Based on polycarboxylate chemistry, polycarboxylate superplasticizers (PCs) with hydrophobic side chains were synthesized through radical copolymerization reaction. The molecular weight and polydispersity index were analyzed by gel permeation chromatograph (GPC), and the results showed the same structural information. The performances of PCs in cement paste were tested by measuring the fluidity and fluidity retention. The slump and the compressive strengths of concrete were also determined. Additionally, the foaming behavior of PCs was investigated by the foam volume, the surface tension of PCs aqueous solution,and the air content of concrete. According to the data, the hydrophobic side chains of PCs may affect the hydration reaction of cement resulting in better workability.

Abstract: Polycarboxylate superplasticizer (PCE) was synthesized in non-aqueous system to achieve the rapid transportation and convenient preparation. The results showed that, PCE using isopentenyl polyethylene glycol (TPEG) or isobutenyl polyethylene glycol (IPEG) as macromonomer exhibited excellent paste fluidities and retaining properties at 80°C and 75°C, respectively. Fourier Transform infrared spectroscopy (FTIR) measurement confirmed the polymerization between monomers. The synthesized PCE as solid state was dissolved into water to prepare the PCE solution, and its cement application performances were studied systematically. The results showed that PCEs with good paste fluidity retentions exhibited the longest final setting time and the shortest setting time interval. The hydration heat results showed that PCEs with good fluidity properties can significantly delay the hydration process and lower the hydration heat.

Abstract: Polycarboxylate was synthesized by using polyethylene glycol monomethyl ether methyl-acrylate (PEG16), methylacrylamide sodium (MAS), methacrylic acid (MAA), methyl acrylate (MA), acryl amide (AM), and sodium persulfate (SPS) and evaluated as a superplasticizer for cement particles. The formulation of the superplasticizer: n (PEG16): n (MAS): n (MAA): n (MA): n (AM) =10:18:20:37:20, and the content of the SPS was 1.2wt% of all the monomers and optimized reaction conditions (80°C, 6h) were obtained via orthogonal test and single factor experiments. The water reducing effect of the synthesized copolymers was studied in terms of reaction temperature, reaction time and PEG side chain length. In this study, flow test of cement paste measurements were performed to compare the molecular weight effect on fluidity of the copolymers. It was observed that the reaction temperature had a noticeable effect on the molecular weight of the PEG-grafted samples thus causing a significant effect on fluidity. The polycarboxylate synthesized at about 80°C has given the highest fluidity result. In addition, the reaction time 6~7 hrs was identified for the best. Furthermore, copolymers with mPEG side chains with a degree of 16 gave the highest fluidity and viscosity average molecular weight value. The initial fluidity of the cement paste containing the prepared superplasticizer (1wt%, w(water)/w(cement)=(0.29)) was 316 mm.

Abstract: Polycarboxylate superplasticizers have become the superstar for high-performance concrete. Because their molecular structure can be easily manipulated by impart new materials to acquire new performance. In this paper, the synthetic parameters adjusting experiment is utilized to get the optimal synthetic formulations. The reaction control factors and polymerization mechanism are also discussed. After characterization, we concluded that the expected performance of polycarboxylate superplasticizer could fabricate through radical graft copolymerization reaction by molecular designing.

Abstract: According to the demanded functions, a novel hardening accelerating and water reducing admixture has been excogitated which is based on a polycarboxylate superplasticizer and cooperated with some other hardening accelerants at the same time, and has many merits such as chloride free、sulfate free、low total alkali content、low dosage、high water reducing rate、high early strength and so on. The performance of this admixture has proved to be outstanding especially in accelerating the early strength of 12 hours and 24 hours age in the concrete tests.