International audienceCellulose ethers (CE) are commonly used as additives to improve the quality of cement-based materials. As admixtures, they improve the properties of mortars such as water retention, workability, and open time. Also, polysaccharides such as starch derivatives are used to improve the consistency of the fresh material. The properties of cement-based mortars at fresh state were investigated. The effect of CE and their physico-chemical parameters (molecular weight, substitution degrees, etc.) on both water retention and rheological properties of mortars were studied. Moreover, some starch derivatives were also examined in order to better understand the water retention mechanisms. Rheological measurements showed that CE have a thickening effect for a content of 0.27 wt.%. Besides, a fundamental effect of CE molecular weight on mortar consistency and its water retention capability was highlighted. Finally, the comparison with starch ethers proved that, for those admixtures, water retention is not directly linked to mortar's viscosity
The goal of this study was to elucidate the influence of the intrinsic properties of roughness, porosity, and surface pH on the susceptibility of mortars to biodegradation by phototrophic microorganisms. An accelerated fouling test was performed allowing a periodic sprinkling of an algae suspension on sample surfaces. The green alga Klebsormidium flaccidum was chosen due to its representativeness and facility in culturing. The biofouling of sample surfaces was evaluated by means of image analysis and color measurement. Two porosities, three roughnesses, and two surface pHs were examined. The colonization by algae of sample surfaces was not influenced by porosity because of the specific conditions of testing that led to a constant high level of moistening of mortar samples. The roughness, in contrast, played an important role in biological colonization. A rougher surface facilitates the attachment of algal cells and so favors the extension of algae. The surface pH was the most important parameter. A lower surface pH accelerated considerably the development of algae on the samples surface.
This paper evaluates and compares the impact of cellulose ethers (CE) on water transport and porous structure of cement-based materials in both fresh and hardened state. Investigations of the porous network (mercury intrusion porosimetry, apparent density, 2D and 3D observations) emphasize an air-entrained stabilisation depending on CE chemistry. We also highlight that CE chemistry leads to a gradual effect on characteristics of the water transport. The global tendencies brought by CE are: higher water retention, lower capillarity water absorption, lower liquid water permeability as well as higher water vapour permeability. All things considered, we demonstrate that CE chemistry is an important controlling factor on water transport and porous structure evolution.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.