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In October, 1994, CANMET in association with the American Concrete Institute sponsored a fourth conference on the superplasticizers and chemical admixtures in Montreal. The objective of this conference was to bring to the attention of the concrete community the new developments in chemical admixtures since the last conference in 1989. A total of 25 papers were accepted for publication in this special proceedings from the conference. If you are involved with superplasticizers and chemical admixtures, this special publication is a must. Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP148

This paper reports on part of a substantial research programme on properties of condensed silica fume (CSF) concretes cured in temperate and climates, carried out in the Department of Civil Engineering at Loughborough. The hot The research approach was to investigate mixtures proportioned to have equal workability and 28 day strength (when water cured at 20°C). This paper examines the effect of superplastizer, curing method (water and polythene) and curing environment (temperate and hot) on the compressive strength, permeability and pore structure of 40 MPa concretes. More specifically, the paper contrasts the performance of two 15% CSF mixtures (replacement by weight of cement) where workabilities were controlled by the addition of extra water or superplasticizer. The development of the concretes’ strength and subsurface permeability index (air and water) with age (from 7 to 180 days) is described, together with the intrinsic permeability (air and water) and pore structure of their equivalent mortar fraction. The use of superplasticizer to control workability increased the compressive strength of CSF concrete mixtures by around 18% and 10% in the temperate and hot environments respectively. The super-plasticized concrete had lower air and water permeabilities which is attributed to an improved pore structure as confirmed by mercury intrusion porosimetry date. The improvements were more marked in the CSF concretes cured in a hot environment.

Aim of this study is to estimate the workability of highly superplasticized concrete, which can satisfactorily fill up all the corners of the forms in reinforced concrete without using a mechanical compactor. To place concrete into reinforced concrete members, it must have segregation resistance and high fluidity. These properties are obtained by using very fine powders with an AE-type high-range water-reducing admixture. The highly superplasticized concrete was prepared by mixing blast furnace slag and limestone powder or silica fume with ordinary portland cement. The fluidity was measured by the box flow test (with and without the reinforcement) and by rheological tests of wet-screening mortar. The effects of mix proportioning and spacing of reinforcements on the fluidity of highly superplasticized concrete have been determined.

To place ultra-high-strength concrete with a compressive strength exceeding 100 MPa on site, technology is required to impart high fluidity to the concrete, with a water-to-cementitious material ratio in an extremely low range, 0.25 or less. For this purpose, the authors synthesized a new superplasticizer comprising water-soluble acrylic graft copolymer, which has excellent cement-dispersing capability. Paper reports investigation of the surface chemical properties of the new superplasticizer and those properties of the cement paste and mortar containing it. It was confirmed that the new superplasticizer imparts a higher fluidity to cement paste and mortar, with a lower range of water-to-cementitious material ratio than conventional superplasticizers. It was also found that the surface tension of the solution of the new superplasticizer is similar to that of conventional polycarboxylate superplasticizers, whereas the adsorption by cement and zeta potential of the new superplasticizer is between those of the ¯-naphthalene superplasticizers and the polycarboxylate superplasticizers. The high fluidity of the cement paste and mortar containing the new superplasticizer with a low-range water-to-cementitious material ratio may be particularly attributable to the preceding properties with respect to surface tension as well as molecular weight and chemical structure of the graft copolymer.

High-purity lignin-based methylsulfonates were prepared by sulfomethylolation of different lignin fractions obtained in an organosolv pulp mill. These methylsulfonates were characterized and their performance in cement slurries and mortars was studied. The chemical analysis focused on determining the degree of sulfonation and molecular weight distribution. Then the 12 samples were tested as possible water-reducing admixtures for concrete. The fluidifying influence of these lignin-based methylsulfonates on cement slurries was evaluated by measuring the torque resistance in a specially developed mixing chamber. Each test involved adding the methylsulfonate in four steps of 0.2 percent by weight of cement to a portland cement slurry of water-cement ratio of 0.45. The decrease of torque resistance indicated there lative effectiveness of the various lignin samples. This test also provided a simple indication of the change in time of set caused by a particular admixture. The sulfomethylolated lignin samples were tested in cement mortars as well. The mortars were prepared with graded silica sand and normal portland cement. The plasticizing effect was determined using the flow table. The increase of flow caused by the addition of different samples in the range of 1.0 and 2.0 percent by weight of cement was tested. The air-entraining effect of these samples was determined from the unit weight measurement of fresh cement mortar. The results of this testing indicated the importance of the chemical characteristics of sulfomethylolated lignin-based water-reducing admixtures on their effectiveness in cement mortar and concrete.