Formulation and characterization of self compacting concrete with silica fume

Self-compacting concrete (SCC) was elaborated using local materials and silica fume (SF) as admixture in 15% of cement quantity, two different Portland cements (PC) and two different superplasticizer that the chemical nature is polycarboxylate and plynaphtalene, the aggregates used are (AG 3/8 mm, AG 8/15 mm), coarse and fine sand (SC, SF) witch fineness modulus 3.2 and 1 in the order. The dosage of the different superplasticizer used is chosen after experimental spreading tests of each self compacting concrete formulation. Results of fresh concrete tests executed, as L-box and segregation resistance are on concordance whit values recommended by the French association of civil engendering. Also the mechanical characterization was conducted by compressive strength and splitting compression testing procedure, results values are in the range higher than 20 Mpa at the seven day by the compressive test for the all compositions, and the highest value was 40.93 MPa at the 28 day bay compressive test of the fourth’s formulation specimens, the values of splitting compressive tests of al formulation specimens at 7, 14 and 28 days, was situated between 2.01 and 4.40 MPa. In order to determine the superplasticizer saturation assay in of cement pasts used in self compacting concrete, the stady was completed by a rheological stady with a variable velocity gradient, so as to estimate the quantity of saturation assay of superplasticizer and the formulation, also the flow models of cement past

Distribution and mobility of arsenic species in solids and leachate composts

Because arsenic can exist in toxic and non-toxic forms, it is important to identify them in compost. This organic material prepared from urban and agricultural wastes, is often used for recovering or remedying soils. As a matter of fact, it’s important to control the mobility of arsenic and its different forms present in leachate composts. In this work total arsenic was determined in compost samples, previously submitted to acid digestion using Inductively Coupled Plasma Mass Spectroscopy (ICP–MS). Total inorganic arsenic and As(III) results were compared with those directly determined in solids samples by Square Wave Voltammetry (SWV). It was found that two thirds of arsenic present in solids are in inorganic forms. As(III) is a minor component in the solid, detectable only in agricultural composts. In leachates, the inorganic arsenic was mobilized in his majority as As(III)

High-efficiency air conditioning - Improving comfort and reducing impact on fuel consumption

International audienceDue to its widespread diffusion, cars A/C systems will face two challenges: a better evaluation of perceived thermal comfort and the reduction of the impact on fuel consumption. In summer and during an urban cycle, the A/C system can increase fuel consumption up to 70%. In view of future regulations and of environmental concern, actions are needed to reduce A/C impact. This paper describes the development of an innovative climate control system accomplished by Fiat Research Center on a B Class Car. Significant results can be achieved thanks to externally controlled variable displacement compressors and to the integration of several control systems