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This work examines the course of the adsorption and the variations in the surface charge observed when monosulphate is dispersed in an aqueous or dimethylsulphoxide solution containing li-gnosulphonate, naphtalene formadehyde condensate and formaldehyde condensate. Melamine The adsorption isotherms obtained by using dimethylsulphoxide of Langmuir type. Are In the aqueous medium adsorption is characterized by a maximum beyond which it decreases. The measurements of Zeta potential carried out on monosulphate dispersed in solutions of the admixtures pointed out a nearly linear increase in the negative charge of the particles up to a value corresponding to the maximum of the adsorption isotherms; beyond this value the potential remains constant. The values of Zeta potential justify the dispersing effect caused by the admixtures due to repulsion among the particles.

This paper presents the results of a laboratory investigation of 47 mixes (31 exploratory mixes and 16 replicate mixes) of superplasticized fiber reinforced concrete. All these mixes were studied for the effect of various parameters such as water-cement ratio, cement content, fiber content, air-entraining agent, and superplasticizer dosage on the plastic and hardened properties of concrete. The fresh concrete was tested for slump, flow table spread, vebe time, air-content and unit weight. The hardened concrete was tested for (i) compressive strength, and (ii) static flexural strength including load deflection curves, toughness index, determination of first crack load and determination of post crack strength. The addition of superplasticizer increased the workability of concrete and it was possible to produce workable high strength concretes with low water-cement ratios. Collating enables the fibers to be easily handled and they could be mixed with aggregates without producing "balling" or tangling during mixing. The static flexural test shows that excellent bond had developed between the fibers and the mortar matrix. The load deflection curves indicate that there is a considerable ductile behavior in the superplasticized fiber reinforced concrete. The addition of hooked and collated fibers increases considerably the post-crack load carrying capacity, the toughness, the energy absorbing capacity resulting In a high ductility of the composite material. The serious drawbacks of high strength concrete namely reduced workability and lack of ductility can be eliminated by adding superplasticizers and steel fibers which will dequately increase the workability and the ductility of the high strength concrete.

The sulphate resistance of mortar lng a superplasticizer and made with blends Type 10 cement, fly ash and granulated blast slag are compared with similar mortars conta ventional water reducing admixture. Compari made with mortars made with C.S.A. Type 50 c Changes in porosity, weight, length, dynamictain- elasticity and compressive strength of the exposed to alternate soaking and ium sulphate solutions for 300 days are desc lus of specified-Interrelationship of w/c ratio, alkalinity of the medium and porosity as primary factors in sulphate attack on the cement paste were investigated. The results indicate that mixes containing a 30% replacement of normal Portland cement by fly ash or slag and a superplasticizer are comparable to mixes made from sulphate resisting cement in their capacity to resist sulphate attack. The degree of attack noted in the superplasticized mixes was significantly reduced in com-parison with mortars where a conventional water reducing admixture was used.

This paper presents the results of a series of laboratory and field studies conducted to determine the engineering properties of superplasticized concrete made of large size aggregate. To find out the effects of dosage of superplasticizer on workability, laboratory studies were conducted on air-entrained concrete mixes having 40mm and 60mm maximum sized aggregates. The fluidizing effect of superplasticizer on such concrete was found to be similar as those in concrete with smaller aggregate, and workability increased with the dosage up to a certain content without significant reduction in entrained air and strength. Field studies were also conducted on the pumpability of superplasticized concrete of large size aggregate. Six mixes of concrete with and without superplasticizer were pumped horizontally through an 8 in. pipeline, 92m in length, and were tested for slump, air content and compressive strength before and after pumping. Pumping pressure, line-pressure and line-pressure-loss were measured at various pumping rates. The test results indicated that superplasticized concrete with large size aggregate can be pumped under 10 to 20 percent lower pumping pressure and line pressure than those of control concrete without deterioration in the properties of fresh and hardened concrete.

Compressive strength and restrained expansion tests were carried out on concretes containing naphthalene sulphonic formaldehyde type superplasticizer and an expansive agent based on processed lime. At constant expansive agent content, the higher the early strength (1 day) the higher was the restrained expansion. Therefore, if the superplasticizer is used to increase the early strength by reducing the water/cement ratio, it is possible to reduce the content of the expansive agent to obtain the same de-gree of expansion. On the other hand, if the superplasticizer is used to reduce both water and cement, and therefore the drying shrinkage, less expansive agent would be required for shrinkage compensation purposes. The results of the present work indicate that the combination of a superplasticizer and an expansive agent may be more advantageous than the use of expansive agent alone.