The adsorption of sodium lignosulphonate onto cement was investigated. The cement has either been pre-hydrated or hydrated with the lignosulphonate present. The pre-hydrated cement particles grow with time, thus a larger surface is created and the plateaus in the adsorption isotherms increase. With lignosulphonate present there is hardly any growth of new surface. It is found that, a lignosulphonate that adsorbs strongly to the surface causes, less retardation than weakly adsorbed lignosulphonates. This can be explained by different interactions with the different minerals present.

Different types of superplasticizers have been widely used over the past few decades in order to produce a more fluid or very high strength and durable concrete. These chemical admixtures interfere with the various physico-chemical processes occurring in early cement paste. In this paper we present results from a study on the influence of superplasticizers on pure tricalciumaluminate hydration in presence of gypsum. The suspensions hydration has been investigated by conductimetry, isothermal calorimetry and total organic carbon analysis of the liquid phase. The time taken for ettringite formation has been determined without superplasticizer and in presence of three different types of superplasticizers: polynaphtalene sulfonates (PNS), polycarboxylate-polyox (PCP) and diphosphonate terminated polyoxyethylene. Whereas diphosphonate terminated polyoxyethylene does not seem to modify tricalcium aluminate hydration carried out in presence of gypsum, PCP and even more PNS slow down ettringite formation. This effect seems to be largely due to a decrease of the C3A dissolution rate and might be connected to an adsorption of PCP. or PNS observed from the early C3A hydration. Such an adsorption does not happen with diphosphonate terminated polyoxyethylene superplasticizer. Moreover the presence of PCP superplasticizer causes a decrease in the size of the ettringite crystals formed.

Self-compacting concrete (SCC) has high flowability and can be placed without vibration. It is defined as concrete that exhibits high deformability and good resistance to segregation. This kind of concrete is of great interest and has gained wide use especially in the case of structures that presents difficult casting conditions, such as heavily reinforced sections. From a rheological point of view, the use of a viscosity-enhancing admixture (VEA) along with an adequate superplasticizer (SP) content can ensure high deformability and stability. However, little is known about the interactions between SP and VEA. Hence, a study on several cement pastes formulated from the original paste of a typical SCC is proposed. One of the major aims of this paper is to show that empirical tests, such as spread and flow time, are suitable to characterize the rheological behavior of cement paste instead of more complex ones. Rheological properties, i.e. viscosity and shear yield stress can be well correlated with empirical test results in the range of flowable mixtures. Moreover, the experimental program leads to emphasize the effects of the mixing procedure and especially the introduction of the SP on the rhelogical properties of cement paste. Finally, test results enable to underline the interactions between SP and VEA used in designing SCC. VEA affects both viscosity and shear yield stress. However, its effect depends on the SP dosage.

Natural stones have always represented major aesthetic factors in building construction. One of the more ancient and important applications, is the production of decorative floorings. The most famous example in the flooring field is the "Terrazzo alla Veneziana". In recent years, the extensive exploiting of quarries and consequent environmental problems have reduced the availability of good low cost quality stone. In the present work, artificial superplasticized aggregates have been produced and used as decorative elements in this new "Terrazzo" flooring. The substitution of natural stones with these artificial materials is a first application of new practice. These aggregates are produced by combining inorganic binders, finely divided carbonaceous and/or siliceous minerals, superplasticizers and water. The use of nanostructural polycarboxylate superplasticizers allows to obtain very low water to cement ratios and, consequently, the final products are characterised by physical and mechanical properties, similar to those of natural stones. Additional ingredients, such as pigments and other materials have been added in order to obtain artificial aggregates with the desired properties and outstanding aesthetic characteristics.

Aggregate shape, texture, and grading have been known to have a significant effect on the rheological performance of fresh concrete. Moreover, while the optimization of aggregate selection can provide both technical and economical benefits, the availability of materials and construction operations can often dictate the use and proportioning of certain aggregate sources, such as manufactured sands, which can adversely impact the rheology of cementitious mixtures. The use of certain chemical admixtures has been found to often minimize the need to increase cement and water contents in order to overcome the loss of workability that can accompany aggregate sources which feature flat, elongated, angular, and rough particles. In this study, a wide range of natural and manufactured sands, characterized for gradation, mineralogy, shape, texture, and cleanliness, are evaluated for their effect on mortar rheology, with and without a viscosifying-type chemical admixture. While associations between aggregate characteristics and their impact of mortar rheology may not be readily evident, the ability of this class of admixture can be shown to mitigate the rheological effect of certain sands, and in some cases allow for optimizing the mixture to lower paste contents.