Book Review: The Post-9/11 Video Game: A Critical Examination

Review of The Post-9/11 Video Game: A Critical Examination by by Jason C. Thompson and Marc A. Ouellette

Accelerated and natural carbonation of concrete with high volumes of fly ash : chemical, mineralogical and microstructural effects

Today, a rather poor carbonation resistance is being reported for high-volume fly ash (HVFA) binder systems. This conclusion is usually drawn from accelerated carbonation experiments conducted at CO2 levels that highly exceed the natural atmospheric CO2 concentration of 0.03-0.04%. However, such accelerated test conditions may change the chemistry of the carbonation reaction (and the resulting amount of CH and C-S-H carbonation), the nature of the mineralogical phases formed (stable calcite versus metastable vaterite, aragonite) and the resulting porosity and pore size distribution of the microstructure after carbonation. In this paper, these phenomena were studied on HVFA and fly ash thorn silica fume (FA + SF) pastes after exposure to 0.03-0.04%, 1% and 10% CO2 using thermogravimetric analysis, quantitative X-ray diffraction and mercury intrusion porosimetry. It was found that none of these techniques unambiguously revealed the reason for significantly underestimating carbonation rates at 1% CO2 from colorimetric carbonation test results obtained after exposure to 10% CO2 that were implemented in a conversion formula that solely accounts for the differences in CO2 concentration. Possibly, excess water production due to carbonation at too high CO2 levels with a pore blocking effect and a diminished solubility for CO2 plays an important role in this

Openings and closings in tourist offices in Belgium, France and the Netherlands.: A relational analysis of their structural properties

This paper deals with openings and closings in 400 service encounters in tourist offices situated in Belgium’s two main language communities, Flanders and Wallonia, in the north of France and the south of the Netherlands. On the basis of a detailed, bottom-up quantitative analysis of the structural properties of the openings and closings, we draw part of the interactional profiles of the tourist office encounters. Differences between the four regions are shown to be related to the degree of volubility and involvement of the interactants and to the degree of ritualisation and efficiency of the opening and the closing section

Life cycle assessment of a column supported isostatic beam in high-volume fly ash concrete (HVFA concrete)

Nowadays, a lot of research is being conducted on high-volume fly ash (HVFA) concrete. However, a precise quantification of the environmental benefit is almost never provided. To do this correctly, we adopted a life cycle (LCA) approach. By considering a simple structure and an environment for the material, differences between traditional and HVFA concrete regarding durability and strength were taken into account. This paper presents the LCA results for a column supported isostatic beam made of reinforced HVFA concrete located in a dry environment exposed to carbonation induced corrosion. With a binder content of 425 kg/m3 and a water-to-binder ratio of 0.375, the estimated carbonation depth after 50 years for a 50 % fly ash mixture does not exceed the nominal concrete cover of 20 mm. As a consequence, no additional concrete manufacturing for structure repair needs to be included in the study. Moreover, structure dimensions can be reduced significantly due to a higher strength compared to the reference concrete used in the same environment. In total, about 32 % of cement can be saved this way. The reduction in environmental impact equals 25.8 %, while this is only 11.4 % if the higher material strength is not considered

Life cycle assessment of completely recyclable concrete

Since the construction sector uses 50% of the Earth. s raw materials and produces 50% of its waste, the development of more durable and sustainable building materials is crucial. Today, Construction and Demolition Waste (CDW) is mainly used in low level applications, namely as unbound material for foundations, e.g., in road construction. Mineral demolition waste can be recycled as crushed aggregates for concrete, but these reduce the compressive strength and affect the workability due to higher values of water absorption. To advance the use of concrete rubble, Completely Recyclable Concrete (CRC) is designed for reincarnation within the cement production, following the Cradle-to-Cradle (C2C) principle. By the design, CRC becomes a resource for cement production because the chemical composition of CRC will be similar to that of cement raw materials. If CRC is used on a regular basis, a closed concrete-cement-concrete material cycle will arise, which is completely different from the current life cycle of traditional concrete. Within the research towards this CRC it is important to quantify the benefit for the environment and Life Cycle Assessment (LCA) needs to be performed, of which the results are presented in a this paper. It was observed that CRC could significantly reduce the global warming potential of concrete

Estimated Service Life of Carbonation Exposed (Cracked) Concrete with Pozzolans or Self-healing Agents

Today, concrete with large portions of ordinary Portland cement (OPC) replaced by fly ash and self-healing concrete count as potential sustainable alternatives to traditional concrete. For the first concrete type, the increased sustainability lies in lowering the carbon footprint which is largely attributable to cement. For the second one that should be able to heal cracks autonomously upon occurrence, an extended service life is the key objective. In this paper, both concrete types were evaluated in terms of service life in carbonation exposed environments. When using the probabilistic model for carbonation-induced steel depassivation of fib Bulletin 34 with mix specific curing exponents, it was found that in uncracked High-Volume Fly Ash (HVFA) and Fly Ash + Silica Fume (FA+SF) concrete carbonation should not reach the reinforcing steel at a typical cover depth of 35 mm within the envisaged design service life of 100 years. This requires a longer optimal curing period though (HVFA: ≥ 20 days; FA+SF: ≥ 9.1 days versus OPC: ≥ 4.2 days). Evaluation of cracked concrete suggests that in presence of a 25 mm deep, 300 µm wide crack the depassivation period would take no longer than 5 years. In case of partial crack healing with the proposed encapsulated polymer, this could be extended to only 11 years regardless of the carrier concrete type (OPC, HVFA or FA+SF, all properly cured for a sufficiently long time). A 100 % crack healing efficiency implying a return to the uncracked state should therefore always be aimed for. The now considered polymer seems reasonably efficient since this was the case for 8 out of 9 samples. To account for the risk of insufficient curing in combination with possibly having an unhealed/partially healed crack anyway, OPC binder systems still have the preference as carrier concrete for incorporation of the healing agent in exposure class XC3