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Home > Publications > International Concrete Abstracts Portal
Showing 1-5 of 34 Abstracts search results
Document:
SP119-10
Date:
September 1, 1989
Author(s):
S. Kakuta and T. Kojima
Publication:
Symposium Papers
Volume:
119
Abstract:
The rheological properties of fresh concrete were studied with three types of mixes containing a superplasticizer, an air-entraining agent, or a soluble polymer. A rotating fan-type rheometer with a table vibrator at the bottom of the container was used for studying the rheological properties of concrete under vibration. The acceleration and the pore water pressure of concrete were also determined. Although the flow curves of these mixes without vibration were of Bingham type, with vibration, they behaved as a Newtonian or a non-Newtonian fluid. The effect of admixtures under vibration could, therefore, be determined by rheological parameters such as coefficient of viscosity or a non-Newtonian power number. The flowing behavior of concrete was related to the pore water pressure and the acceleration. The excess pore water pressure was affected by the type of admixture. High pore water pressure resulted in concrete containing the soluble polymer.
DOI:
10.14359/2468
SP119-11
F. Basile, S. Biagini, G. Ferrari, and M. Collepardi
Eight samples of sodium salts of naphthalenesulfonic acid-formaldehyde condensates with different molecular weight have been synthesized by stopping the polymerization process at different reaction times between zero (monomer) and 14 hr at 112 C using a molar H2SO4/naphthalene ratio of 1.07 and a molar HCHO/naphthalene ratio of 1.20. The longer the reaction time, the higher the molecular weight. The condensates have been analyzed by Gel Permeation Chromatography to determine the chemical composition and average molecular weight. The condensates have been used as superplasticizers (0.4 percent of dry product by weight of cement) for cement paste (water/cement ratio = 0.35) and the fluidifying effect has been determined by the mini slump test. It was found that the fluidifying effect increased by reducing the content of monomer and increasing the molecular weight of the condensate. To confirm that the fluidifying effect of the condensate substantially depends only on the content of the higher molecular weight fraction, two samples of the condensate, with different reaction times and then with a different condensation degree have been subjected to an ultrafiltration process. This technique allows removal of the monomer and the lower molecular weight fraction. The two samples of the condensate, which had different fluidifying effects before the ultrafiltration process, behaved similarly as superplasticizers after the ultrafiltration process.
10.14359/2472
SP119-12
J. J. Beaudoin and V. S. Ramachandran
Study was designed to assess the merits of polymer addition to superplasticized cement paste, mortar, and concrete. Three superplasticizers--a sulfonated melamine formaldehyde, a sulfonated naphthalene formaldehyde, and a commercial superplasticizer--were used in combination with experimental polymers. Polymer and superplasticizer dosages ranged from 0 to 15 percent and 0 to 0.3 percent, respectively. The effect of binary admixture systems (superplasticizer and polymer) on the physicomechanical properties of the cementitious systems was determined. Properties investigated included slump, slump retention, setting time, compressive strength, flexural strength, surface area, porosity, and density. Compatibility of the polymers with the superplasticizer was assessed with respect to the influence of the individual admixtures on the properties of the various systems. Synergistic effects were observed for one polymer, the results of which are discussed in detail.
10.14359/2480
SP119-13
T. Izumi, T. Mizunuma, M. Iizuka, and M. Fukuda
A new technology of slump control with a reactive polymeric dispersant was studied. The mechanism of slump loss prevention as well as the physical properties of concrete containing the dispersant were discussed. To solve the slump loss problem, the authors developed ultra-fine particles of reactive polymer. It is a dispersant precursor originally insoluble in water but is gradually converted into a dispersant by hydrolysis with strong alkaline materials in concrete. It was found that the workability of concrete was controlled favorably with the reactive polymeric dispersant.
10.14359/2486
SP119-14
S. Chandra and P. Flodin
Certain polymer dispersions interact with calcium hydroxide and form precipitates. The amount thereof increases until a specific limit above which the volume of precipitate becomes constant. This could be illustrated photographically. By x-ray diffraction analysis, it was shown that increasing the amount of polymer gradually decreased the height of the diffraction peaks of calcium hydroxide, and finally only a broad shoulder was observed. In microscopic analysis, no typical distinct crystals of calcium hydroxide could be seen. A mechanism for the influence of the polymer on the crystallization process is proposed.
10.14359/2491
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