(Received 18 December 2003; accepted 28 February 2005)
Published Online: 2005
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At the present time, there are essentially two types of water-reducers: high-range water-reducers and conventional water-reducers. Superplasticizers allow a 15–30 % water reduction. They are very efficient to disperse cement particles in concretes made with W/C ratios between 0.25 and 0.45. For concrete having a W/C ratio between 0.45 and 0.60, the optimal dosage is not generally very high and lacks robustness. In industrial applications, the use of superplasticizer in 0.45–0.60 W/C ratio concrete can result in segregation (light over-dosage) or a rapid slump loss (light under-dosage).
The use of conventional water-reducers, obtained mostly from more or less processed and treated industrial by-products, results in a water reduction of between 5 and 10 %. Moreover, because they almost always contain some impurities, essentially sugars and surfactants, their dosage cannot be increased without causing excessive air entraining and a long delay in setting.
To cover the W/C ratio range between 0.45 and 0.60, it is necessary to use admixtures of the mid-range family, which are usually obtained by mixing a superplasticizer and a conventional water-reducer or a water-reducer and an accelerator. This method presents several disadvantages linked to formulation adjustment and to the availability and quality of lignosulfonate water-reducers, which may decrease in the future due to a drastic change in the production of pulp and paper worldwide.
A new type of synthetic mid-range water-reducer has been developed in order to meet the requirements of the mid-range water-reducers: comfort of rheology, no effect on setting time, and no air entrainment. It is a co-polymer of the polysulphonate family adapted for concretes made with a W/C ratio between 0.45 and 0.60. The performance of the last version of this product has been studied on grouts having a water/cement ratio of 0.45 and on concretes having a water/cement ratio of 0.44. This performance has been compared to the performance of two commercial mid-ranges and a classic water-reducer, lignosulfonate-based.
The synthetic mid-range showed a very promising dispersing performance and robustness adapted to the concrete formulation generally covered by mid-range water-reducers. Its very definite chemical composition and its controlled production make this new polysulphonate co-polymer an interesting alternative for the formulation of mid-range water-reducers.
Ph.D., holder of an Industrial Research Postdoctoral Fellowship (IRF), NSERC (Natural Sciences and Engineering Research Council of Canada), and Handy Chemicals, Handy Chemicals Ltd., Candiac, Québec
M.Sc.A., Research Engineer in charge of the concrete laboratory, Handy Chemicals Ltd., Candiac, Québec
Ph.D., Executive Vice-President, Handy Chemicals Ltd., Candiac, Québec
Ph.D., Professor Emeritus, Université de Sherbrooke, Sherbrooke, Québec
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