Comprehension of demoulding mechanisms at the formwork/oil/concrete interface

The implementation of concrete and its association with a release agent influence the aesthetics of the concrete facings. The mineral oils tend to be replaced by vegetable formulations, to reduce the impact of the substances spilled in the environment. From a technical point of view, it is important to characterize the action of these new formulations at the interface concrete/oil/formwork. Two performing techniques have been used to study the physicochemical processes, the tribometry and electrochemical impedance spectroscopy. The correlation of the results obtained allowed to improve the understanding of the mechanisms involved at the interface mould/oil, in connection with the use of an acidifier in the formulation

Friction Mechanisms of Fresh Concrete Under Pressure”,

ABSTRACT Ensuring adequate placement of concrete on site requires special consideration of rheological properties and concrete/wall interface. However, few studies were conducted on phenomena existing at the interface and particularly when the concrete is under pressure. Friction occurs in many applications in civil engineering field as slipforming, concrete pressure on formwork, or on the concrete facing quality. This paper provides experimental results to enable a better understanding of friction mechanisms. Many parameters that influence friction are being studied on different types of concrete. Friction tests on fresh concrete have been carried out using a plane/plane tribometer. Critical pressures and sliding velocities appear depending on the plate roughness and the mix design. Concerning the mix design, grains size and the water reducing agent play an important role on the friction stress. These results can contribute to adapt mix design according to the application and to perform models based on the fresh concrete friction

The antithetical poetics of Herman Melville: The shorter published poems

Herman Melville\u27s poetry was rejected by a readership that demanded a countenanced rhyme and meter, predictable form, imagery and metaphor. The repulse ensured his continued antithetical response to the condition of the country, as well as to expectations for poetic discourse. Dispossession, his long travels abroad, and civil war all precipitated Melville\u27s engagement with themes of separation and dis/memberment. Technically, the poetry confronts matters of division and reintegration by means of three recurring tropes. These are the devices known as tmesis, chiasmus, and catachresis. These rhetorical conceits apply both to individual poems and specific pairings. For example, Billy in the Darbies and Crossing the Tropics, discussed in separate chapters, are both addressed in terms of reversal and dislocation, are thematically chiastic in their temporal-spatial arrangements. Catachresis is the dominant trope for the discussion of war\u27s dissonant, cataclysmic inversion of integrity. Tmesis, the trope of self-interruption or division, figures both in the discussion of the war poems, and the reading of After the Pleasure Party. This study also focuses on certain topical and thematic issues. In this vein, I pursue Melville\u27s grappling with the tragedies that democracy creates: the unreconciled oppositional mode of Battle-Pieces and Aspects of the War, which sees the victims of war as pieces of the battle, fragments and remnants of the cataclysm. The poems in John Marr and Other Sailors With Some Sea-Pieces (1888) commemorate the dead and nearly-forgotten. I take mimesis, in this context as Melville\u27s means of reconciling discrete elements key to his representation of natural rhythm. Isolation essential to creative endeavor is central to my discussion of Melville\u27s last published volume, Timoleon Etc. (1891). In his desire to comprehend the nature of loneness, he turns to biblical and classical motifs. These motifs occupy the ground on which Melville chooses to encounter a portion of the past relevant to the poetic process and the predicament of the artist

Influence of rheological properties of concrete foundation on the implementation of continuous flight auger (CFA) piles

International audienc

Prediction of the lateral pressure exerted by self-compacting concrete on formwork

International audienc

Pozzolanic activity of kaolinite material rich in gibbsite calcined at low temperature and its effect on physical and mechanical properties of Portland cement mortars

Gibbsite in tropical kaolinite material greatly influences its reactivity as pozzolanic material. The aim of this research is to study the effect of gibbsite, Al(OH)3, (15.9 mass%) on the pozzolanic activity of a kaolinite material calcined at low temperature. To this effect, the as-received raw kaolinite material was calcined at 600°C and the output product was used to partially replace Portland cement by 0, 10 and 20 mass% to produce mortars. The calcined kaolinite material was firstly subjected to the modified Chapelle test and strength activity index in order to evaluate its pozzolanic activity and physical and mechanical properties of the as-produced specimens were assessed. The results show that the calcined kaolinite material presents a high pozzolanic activity (Chappelle test = 1665 mg of Ca(OH)2/g) compared to the reference un-calcined kaolinite material (535.0 mg of Ca(OH)2/g). After 28 days of curing, mortars obtained from partial replacement with 10 mass% of the calcined kaolinite material show higher compressive strength (54.5 MPa) compared to those obtained with 20 mass% (51.3 MPa). Indeed, these values are higher compared to those of mortars produced without replacement. In fact, aluminium compound promotes the formation of metastable hydrated phases (CAH10/C2AH8) at early age which temporally hinder cement hydration. Conversely, these phases are progressively transformed into stable hydrated phases of C3AH6 with time, thereby favoring the hardening of specimens. Thus, partial replacement of Portland Cement by 10 mass% of the calcined kaolinite material is suitable to obtain mortars endowed with enhanced compressive strength for construction purpose

Experimental study on the valorization of poplar by-products in cement-based materials

International audienc