Industrial Potentiality of Alluvial Clays Deposits from Cameroon: Influence of Lateritic Clayey Admixture for Fired Bricks Production
The cartography and characterization of an alluvial clay deposit from Ebebda (Central region of Cameroon) were carried out in order to assess its suitability for the production of fired clay bricks. The clayey area investigated is ~ 50,000 m2 with an average thickness of the exploitable layer of 2.2 m, suggesting a deposit of about ~2.2 × 105 tonnes of clay. Mineralogy, physico-chemical and thermal analyses as well as firing properties were performed on representative clay samples. Kaolinite and quartz are the major minerals associated to illite. Upon heating to 900℃ - 1200℃, the linear shrinkage varies from 1.5% to 15%, the water absorption from 1.5% to 24% and the bending strength from 2 to 12 MPa. The admixture of lateritic clays (widely available) at 50%, 60%, 70% and 80% allow to decrease the shrinkage and bending strength, and to increase the water absorption. Overall, properties were satisfying the requirement for fired brick with 70% of laterite in the mixture.
Utilisation of glass wool waste and mine tailings in high performance building ceramics
Abstract The generation of glass wool waste and mine tailings has raised increasing concerns. This paper deals with the reuse of glass wool waste and lithium mine tailings from spodumene ore (quartz feldspar sand; QFS) in the development of building ceramic materials. The effect of glass wool particle size and sintering temperatures (750, 850 and 950 °C) were investigated. Phase composition and sintering reactions were studied using several techniques including X-ray diffraction with Rietveld refinement, differential scanning calorimetry, scanning electron microscopy, density, water absorption and mechanical tests. The results showed that glass wool acted as fluxing agent, with melting reactions observed from about 700 °C. Grinding glass wool improved its reactivity, enhancing densification and strength development at lower temperatures. The properties of the prepared building ceramics satisfied the requirement of building materials according to ASTM C62 , achieving high performance values of 90 MPa and 25 MPa for compressive and flexural strength respectively. These results are of interest for the reuse of glass wool waste, QFS and similar waste streams in building ceramics.
Time and Heritage
As a historian studying what can be considered a form of intellectual history, I have slowly come to adopt Michel de Certeau’s observation made at the end of the 1980s that ‘objectifying the past, for the last three centuries, has undoubtedly left unconsidered time within a discipline that has continued to use it as a taxonomic instrument’. To a certain degree, time has become commonplace for the historian who has preserved or instrumentalized it. It is not considered because it is inconceivable, but because we do not think of it or, more simply, we do not think about it. As a historian attempting to pay attention to the time I’m living in, I have thus, like many others, noticed the swift development of the category of the present until it has become obvious that the present is omnipresent. This is what I refer to here as ‘presentism’.