Characterization of granite and limestone powders for use as fillers in bituminous mastics dosage

This paper discusses the importance of studies on materials known as fillers from different mineral origins, used in asphalt mixes, specifically in the formulation of mastics. The research was carried out on samples of limestone and granite rock filler and asphalt binder (50/70). The samples were evaluated through semiquantitative chemical analyses by X-ray fluorescence, granulometry by low angle laser emission, scanning electron microscopy, softening point tests, penetration tests, and aggregate-asphalt binder and aggregate-mastic adhesion tests. The results highlighted convergent trends, indicating that the active behavior of the fillers in the mastic formulation is not related to the size of the particles, but rather to their form, surface texture, specific surface area and mineralogical nature, allowing the filler activity concept to be divided into two components: physical (hardening) and chemical (adhesion).

Effects of Mnemonic Reconstructions on the Spatial Learning of Adolescents with Learning Disabilities

Thirty-nine seventh- and eighth-grade students with learning disabilities received verbal and spatial information about eighteenth-century North American battles under two conditions. In the control condition, learners were provided a map depicting locations of battles, accompanied by descriptive/decorative pictures. Mnemonic condition learners received the same map with the exception that pictures accompanying place names represented reconstructed keywords of those names. In both conditions, pictures were colored red if they represented British victories, blue if they represented American victories. After a training session and a 90-second filler activity, students were asked to locate each battle on an unlabeled map and indicate which side had won the battle. Analysis of results indicated that mnemonic condition students significantly outperformed controls on measures of spatial relocation and correct matching of place name with victor. Effects were especially pronounced on the measure of spatial relocation, in which an effect size of over two standard deviations was obtained. Implications for research and practice are discussed.

Structure and Properties of Filled Stocks XVI. Polybutadiene Filled with Colloidal Silica

1. Colloidal silica can be partially or completely removed from filled rubber stocks by boiling in 1% aqueous NaOH. 2. Degree and rate of extracting directly depend on the reinforcing effect of the silica. The higher the filler activity, the more complete its extractability from the rubber. Inactive samples of silica practically cannot be extracted from filled rubber stocks. 3. The active silica forms a thixotropic chain structure in the rubber, but inactive silica is distributed in rubber as isolated particles or aggregates. 4. The rubber portion that remains after extraction of the active silica is insoluble in common rubber solvents. 5. The equilibrium swelling value in binary solvents (butanol-toluene) is lower, the higher the reinforcing action of the silica. 6. The reinforcing effect of silica is proportional to its moisture takeup capacity, which may be determined by a simple method described. 7. Based on the experiments described, the type of linkages involved and the structure of the rubber stock filled with silica are considered.