This CD contains 33 papers presented at the Tenth International Conference of Superplasticizers and Other Chemical Admixtures in Concrete held in Prague, Czech Republic, in October 2012. Topics include Synthesis, Characterization, and Dispersing Performance of a Novel Cycloaliphatic Superplasticizer; Compatibility between Polycarboxylate and Viscosity-Modifying Admixtures in Cement Pastes; Aspects of Gypsum-Free Portland Cement; A Novel Type of PCE Possessing Silyl Functionalities; and much more. Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-288

Superplasticizers (SP) are expected to affect cement particles colloidal interac¬tions network and yield stress. They can therefore affect apparent viscosity which depends both on yield stress and viscous dissipation. However, at high shear rates at which colloidal interactions can be neglected, cement pastes viscosity is expected to only depend on hydro¬dynamic energy dissipation in the interstitial fluid and shall not be affected by SP. Experi¬mental results show, however, that it is not the case, and that SP also affects the contribu¬tion of hydrodynamic energy dissipation to macroscopic viscosity of cement paste. The rheological and adsorption measurements presented in this work suggest that this peculiar effect can be attributed to the influence of direct contacts between cement particles on viscosity. The polymer adsorbed on cement grains seems to be able to decrease the friction coefficient between cement grains, and therefore, decrease the macroscopic viscosity of the mixture.

The development of carboxylic-based PCE superplasticizers in the last 10 to 15 years has prompted the development of concrete applications which would have been of difficult accomplishment without such materials. The main difference between PCE superplasticizers and the products which were used before lie in the long slump retention which can be obtained with such products. Another important characteristic of PCE super¬plasticizers is that their efficiency is obtained at low dosage, and consequently they alter in a minimal way the chemistry of cement hydration. However PCE superplasticizers show a high sensitivity to small changes of the chemistry of the hydrating cement paste. A range of phosphorous-based superplasticizers have been developed that show greater robustness of performance, still having the characteristics of long slump retention, low hydration and hardening retardation and low dosage efficiency. In the present paper we investigate the particle-particle interactions in the presence of PCE and phosphorous-based superplasticizers.

To reduce CO2 emission, portland clinker in industrial cement is substituted by reactive and nonreactive mineral additions. This research examines the effect of the structure of selected polymers on their dispersing activity on three different matrixes: portland cement (CEM I 52.5R), portland slag cement (CEM II/B-S 42.5N) and pozzolanic cement (CEM IV/A-P 42.5R). The role of the length of the main parts of a typical comb-polymer on its adsorption behavior and deflocculating capability has been evaluated. For the purpose different poly¬mers having Mw of polyacrylic backbone equal to 2000 and 5000Da and methoxy-PEO dispersing side chains equal to 1000 and 3000 Da were synthesized. Esterification ratio was fixed at 30%. Adsorption isotherms were evaluated by TOC technique while dispersing behavior by mini-slump test. It results that dimension of superplasticizer has a remarkable role on dispersing ability particularly in the case of pozzolanic cement.

Metakaolin (MK) comes from the calcination of kaolinite at temperatures ranging from 700°C (1292°F) to 850°C (1562°F). The resulting dehydroxylation of kaolinite produces an amorphous material (metakaolin) that is usually very reactive in alkaline media such as cement-based materials. However, the reactivity generally takes effect after a few days, so poor short-term performance is obtained, which is a disadvantage in cases where the concrete needs to be rapidly stripped of its formwork. The aim of this work was to test different chemical activators for metakaolin, in order to obtain short-term strength similar to that obtained without metakaolin. Twelve activators were selected and tested in mortars at different concentrations, using two modes of intro¬duction (in solution and in solid form). Four cements were used in the experiments (2 CEM I and 2 CEM II). Workability and compressive strength tests were carried out (at 16 h, 24 h, 48 h, 7 d, and 28 d). The results show disparities in the efficiency of the activation. Products very active at early ages often led to a decrease in strength at 28 days of age, compared to activator-free mixtures.