Adsorption on porous Vycor glass at different temperatures at low and medium relative humidities

In this report, the measured adsorption isotherms on porous glass, obtained experimentally at different temperatures, are used to calculate the specific surface area, using two different types of BET-equations

The effect of different cements and pozzolans on chloride ingress into concrete

Chloride profiles were measured on ten different concrete qualities. The effect of two different cements, an ordinary Portland cement, OPC, and a sulfate-resistent Portland cement, SRPC, with and without inclusion of silica fume and fly ash was investigated. The samples were exposed to a 3 wt% sodium chloride solution for 119 days. Two different preparations before exposure were studied. Both types of preparations consisted of one-day membrane hardening after casting. Af ter this a set of samples were dried for two we eks and then rewetted in tap water for one week before exposure. The other set of samples were stored in tap water one week before exposure to chlorides. The chloride content profile in concrete was measured by removing approximately 1.2 mm thick layers, from the exposed surface, by grinding. The concrete powder, collected from different depths from the surface, was dissolved in an acid and analyzed for chlorides by an ion-selective electrode. The obtained chloride profiles were evaluated in two ways. The first consisted of a simple curve fitting to the solution to Fick's second law, without any special attention to boundary conditions, in order to obtain the so-called effective diffusion constant. The other method of evaluating the measured values consisted of a more detailed hypothesis accounting for dielectrical effects, diffusion of free ions in pore solution, and chemical reaction such as binding of chlorides and dissolution of hydroxide from solid hydration products. Both methods of evaluating the me asur ed data gave the result that the OPC concretes resisted chloride ingress better than SRCP concretes at the same water to binder ratios when stored in water before exposure. The OPC concrete in which 5% of the cement content were replaced by silica fume resisted chloride ingress significantly better than the SRPC with the same relative amount of silica fume. This behavior was independent of curing conditions

A theoretical model describing diffusion of a mixture of different types of ions in pore solution of concrete coupled to moisture transport

A theoretical model is established for diffusion of different types of ions in pore solution of concrete and the coupling to moisture flow and moisture content. Mass exchanges between ions in pore solution and solid hydration products in the concrete are also considered. The basic concepts behind the so-called mixture theory are used

Are boys discriminated in Swedish high schools?

Girls typically have higher grades than boys in school and recent research suggests that part of this gender difference may be due to discrimination of boys. We rigorously test this in a field experiment where a random sample of the same tests in the Swedish language is subject to blind and non-blind grading. The non-blind test score is on average 15 % lower for boys than for girls. Blind grading lowers the average grades with 13 %, indicating that personal ties and/or grade inflation are important in non-blind grading. But we find no evidence of discrimination against boys. The point estimate of the discrimination effect is close to zero with a 95 % confidence interval of ±4.5 % of the average non-blind grade.Discrimination; Field experiments; Grading; Education; Gender