Admixtures water-reducing agents

Water-Reducing Agents and Superplasticizers. Common admixtures that improve fluidity of concrete mixes are often used in high strength concrete. These admixtures make possible the incorporation of siUca fume while maintaining necessary workabiUty. Three principal types of... 

The addition of a water-reducing agent to the aqueous phase is followed by a rapid reduction in the quantity of admixture in solution and an... 

Table 1.21 Sulfate resistance of concrete mixes containing water-reducing agents (no mix design changes other than addition of water-reducing admixture)...

The recorded data on lignosulfonate water-reducing agents indicate that, as far as freeze-thaw durability is concerned, because of the low water-cement ratios possible, an enhancement to the durability will invariably be obtained. When the admixtures are used to effect a reduction in the cement content, there are strong indications that a considerable enhancement of durability is obtained, presumably due to a reduction in the cement matrix which is the part of the concrete susceptible to frost damage. The higher aggregate content would therefore allow easier dissipation of stresses. 

Concrete containing No admixture Neutralized wood resin Air-entraining water-reducing agent... 

When materials other than a lignosulfonate water-reducing agent are used, in conditions where significant drying of concrete can take place, caution must be exercised where straight additions are used and where differential creep rates could be obtained in comparison to adjacent concrete containing no admixtures. 

This raw material was one of the first materials referred to in the literature as a water-reducing agent [16] yet only since 1970 has it found extensive application in admixture formulations. 

The effect produced by the incorporation of a lignosulfonate-based water-reducing agent is shown in Table 7.6. The results were obtained from a series of mixes over an 8-month period by a ready-mix plant used in the production of concrete piles. Since the standard deviation of this particular plant was 5.0 MPa for mixes produced without the use of admixtures, it is evident that the use of the admixture resulted in reduced variability. These results indicate that in high workability mixes with cement contents in the median range, the admixture may cause an increase in the standard deviation. Thus in redesigning the mix to have a lower cement content in this class of concrete, adequate consideration should be given to this difference in standard deviation. Increased uniformity can be attained in this instance... 

However, it is felt that the intrinsic property of most water-reducing admixtures is to increase the creep and shrinkage of the concretes into which they are incorporated. This is minimized by utilizing the effect of the admixture to reduce the cement and, therefore, the paste content of the mix. For corresponding mixes with lignosulfonate water-reducing agents, the FIP/CEB recommendation for creep computation can be used with confidence because of the incorporation of a cement content/water-cement ratio function in the calculation. 

Commercial admixtures employed were a polyalkyl aryl sulfonate-type high range water-reducing agent, four polyoxyethylene nonylphenol ether-type... 

Superplasticisers Also called water-reducing agents-, chemical admixtures used to disperse particles homogeneously. In concrete or mortar... 

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