Superplasticizers compressive strength

Fig. 2.20 The relationship between water-cement ratio and compressive strength of concretes containing superplasticizers.

The lower water-cement ratio afforded by the use of a superplasticizer may be used to increase existing compressive strengths or to reduce cement content. Thus the use of superplasticizers may enable the precast producer to use lower cement content without reduction in mix workability and rate of strength development. The actual amount of cement reduction achieved will depend on the cement type used and the mix proportion used in the concrete. Previous work [63] indicates that even with low cement content (306 kg m 3) a normal dose of superplasticizer can accelerate 3- and 28-day strengths by 90% and 55%, respectively, over levels attained with a plain mix. Cement reductions in the range of 11-20% have been achieved in mixes with a cement content of 415 kg m, while maintaining desired strength... 

The compressive strength of concrete is increased by the use of a superplasticizer to reduce the water content while maintaining workability. The increase in strength is, as with a normal water-reducer, a direct result of the lower water/cement ratio. The increase in strength will follow the strength/water-cement relationship for the particular cement. 

The cement pastes, with or without colloidal sihca, had a water to cement ratio of 0.35 and contained sulfo-nated naftalene formaldehyde resin (NSF) superplasticizer. The colloidal silica was added to the concrete mixture after the superplasticizer so as to minimize prema-mre gelling. The compressive strength of the concrete samples are shown in Table 57.5. 

Figure 13.4. Compressive strength of concrete with and without superplasticizer (0.25 wt% of sodium salt of P-naphthol sulfonate formaldehyde condensate) vs. curing time. [Data from El-Hosiny F I Gad E A M, J. Appl Polym. Set., 56, No.2, 11th April 1995, p. 153-9.]...

Bouzoubaa, N., Zhang, M.H., and Malhotra, V.M. (1998) Superplasticized Portland cement production and compressive strength of mortars and concrete. Cement and Concrete Research 28, 1783-1796. 

Wang et al. (1992b) combined ferroaluminate cement with micro-silica and fly ash. Mortars made from such blends with an added superplasticizer attained higher strengths even at fly ash contents of 30 per cent. Remarkably, the flexural/compressive strength ratio of such mortars was exceptionally high, i.e. around 0.2. (Table 4.3). 

A new water-soluble sulfonated phenolic resin as a potential superplasticizer was prepared from formaldehyde, phenol, and sodium bisulfite (NaHSOs) through a four-step reaction procedure. It was found that this resin could reduce the water content and improve the workability and compressive strength of concrete. The best results were obtained for concrete containing 2 wt% resin, which are comparable with commercial superplasticizers (128,174-176). 

HPC mixes with particularly low water-to-cement ratios, resulting in high compressive strengths, have been achieved with superplasticizer additives. These additives obviously play a crucial role in ensuring satisfactory workability at the low water contents. High density and low permeability typically characterize such mixes, which can be expected to represent an effective barrier to the ingress of corrosive species, provided the concrete is in the uncracked condition. Certain... 

On the other hand, the addition of limestone powder to the mixture produced higher thermal conductivity as well as higher compressive and flexural strength. In particular, in the presence of a superplasticizing admixture and 10% PU particles, similar thermal and mechanical performance of the reference mortar could be achieved. 

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