Search results for "superplasticizer"
showing 7 items of 7 documents
Effect of superplasticizers on the rheological properties of fly ash suspensions containing activators of the pozzolanic reaction
2000
Rheological studies have been carried out on the effect of a superplasticizer from the sulphonated melamine formaldehyde (SMF) group upon the properties of fly ash suspensions containing a small quantity of mineral admixtures such as cement, lime and gypsum. The superplasticizers' efficiency has appeared to depend greatly on the admixture used. The highest liquefaction degree was found in fly ash suspensions containing both cement and gypsum together and the next it was, when only cement was added. These suspensions exhibit features of a newtonian fluid of low plastic viscosity, when the water to solid ratio (w/s) is 0.3 and a superplasticizer has been used. However, fly ash suspensions wit…
Changes in Cement Paste and Mortar Fluidity after mixing induced by PCP: A parametric study
2006
International audience; The interaction mechanism between polycarboxylate-type superplasticizer (PCP) and cement hydration is not fully understood and incompatibilities between concrete and additive are sometimes observed. In some cases, the fluidity tends to increase (“overfluidification”) few minutes after mixing. This is a problem because the overfluidification leds to bleeding of the concrete which could be critical on job site. Our study consisted first in highlighting the phenomenon of “over-fluidification” by slump flow tests on mortar. Next, the time evolution of the rheological behaviour of cement pastes in the presence of PCP was analysed thanks to a rheometry protocol in order to…
Modification of the rate of formation and surface area of ettringite by polycarboxylate ether superplasticizers during early C3A–CaSO4 hydration
2015
Abstract Early C3A–CaSO4 hydration was studied in the presence of various amounts of two polycarboxylate ether superplasticizers differing in their grafting degree. Hydration and surface area developments were investigated by in-situ NMR relaxometry coupled with BET and DSC during the first 2 h after mixing. This study enables a quantitative comparison of the amount and the specific surface area of the ettringite precipitated along the C3A–CaSO4 hydration with or without PCE. The main effect of PCE is to strongly increase ettringite specific area for a variable period. These effects are clearly dependent on the PCE charge and dosage and are reduced when using delayed addition. In this conte…
Influence of three types of superplasticizers on tricalciumaluminate hydration in presence of gypsum.
2006
International audience; 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 d…
Reactive Powder Concrete Containing Basalt Fibers: Strength, Abrasion and Porosity
2020
The paper presents the test results of basalt fiber impact on a compressive and flexural strength, resistance to abrasion and porosity of Reactive Powder Concrete (RPC). The reasons for testing were interesting mechanical properties of basalt fibers, the significant tensile strength and flexural strength, and in particular the resistance to high temperatures, as well as a relatively small number of RPC tests performed with those fibers and different opinions regarding the impact of those fibers on concrete strength. The composition of the concrete mix was optimized to obtain the highest packing density of particles in the composite, based on the optimum particle size distribution curve acc.…
Tailoring the anionic function and the side chains of comb-like superplasticizers to improve their adsorption
2015
Nowadays admixtures and especially superplasticizers are unavoidable components of the concrete formulation. The high fluidizing efficiency of the comb-like superplasticizers must not overshadow their high costs. This study aims to determine the PCE structure parameters which influence their adsorption in order to enhance their resistance to sulfate competitive adsorption and thus minimize their dosage. The PCE adsorption has been studied on calcite and ettringite which are both surfaces representative of early hydrating cement. The effect of the POE side chain length and density and also of the PCE anionic function i.e. carboxylate, dicarboxylate or phosphate on the adsorption has been ana…
Fluidizing efficiency of comb-like superplasticizers: The effect of the anionic function, the side chain length and the grafting degree
2015
Superplasticizers and especially polycarboxylate grafted polyethylene oxide (PCE) demonstrated their efficiency to fluidify concrete. The aim of this work is to investigate the evolution of the fluidity as a function of adsorption in a sulfated solution with a wide variety of comb-like superplasticizers and at incomplete adsorption rate. Polymers with various side chain lengths, grafting ratios and also with modified anionic functions (carboxylate, dicarboxylate and phosphate) were synthesized. Inert calcite suspensions were used to mimic early age cementitious materials avoiding the cement hydration. Models of polymer conformation and yield stress prediction have been tested. But the most …