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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 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.

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.

More than twenty naphthalene sulphonated formaldehyde condensates have been synthesized with various degrees of polymerization. This was evaluated by viscosity measurements of the polymer in water solution. Polymer adsorption, zeta potential, fluidity and compressive strength of cement mixtures have been examined as a function of the degree of polymerization and the polymer dosage. Polymer adsorption, zeta potential and fluidity increase by increasing the polymer dosage in the range of 0.25 -2.00 % by weight of cement. Polymer adsorption, zeta potential, fluidity increase by increasing the degree of polymerization. However, above a certain degree of polymerization all the above mentioned properties do not change further. Cement particles adsorb the polymer molecules and this causes an increase in the electrical charge on the cement surface. This results in a better dispersion of cement particles and a more fluid system. However, even if there is a certain interaction between fluidity and zeta potential, the latter is not the only parameter controlling the fluidity of the system. At the same water/cement ratio, by increasing the degree of polymerization the strength is, in general, slightly increased and this seems to be related to a better dispersion of cement particles.

The principle of a free orifice rheometer is used in a development of a device for site-tests of consistency of fresh superplasticized concretes. The new test is designed to complement the '2-point' test and to provide an alternative or even to replace the DIN Flow Table (1) test. Full scale prototype of the Orifice Rheometer was constructed and tests confirmed the capacity of the rheometer to detect differences between fresh flowing mixtures. Using an appropriate orifice the sensitivity of the device was sufficient to indicate excessive bleeding or segregation caused by an overdose of an admixture. Influence of factors such as the composition of a mixture, type and dosage of a superplasticizer on the consistency of a fresh flowing concrete and on its retention were also investigated. In its present form the Orifice Rheometer is a simple, rugged and easily portable apparatus which has provided encouraging results from its first site trials.