This work investigates the electrical and heating performance of conductive cement composites by using carbonaceous materials (carbon fibers (CF) and carbon nanotubes (CNT)) as conductive materials. Various volume fractions of carbonaceous materials were used to indicate the electrical heating performance of the cement composites. Experimental results showed that adding the carbonaceous materials in cement composites reduced the electrical resistance by more than 98% than that of the main cement paste. The percolation threshold of all carbonaceous cement composites was found to be between 0.1 and 0.75 vol%. By applying a potential voltage to the cement composites, different heating temperatures were investigated depending on the type of carbonaceous materials and their volume fractions. The conductive cement composites showed high heating performance exceeded 100°C within a record time when the input voltage is 60 V. At the end of the study, an analysis of electric power consumption was carried out to determine the feasibility of using carbonaceous materials as self-heating components in the suggested conductive cement composites.
More than two million school-age children in Yemen are unable to enroll in education because of a shortage of school buildings. This is one of the reasons the country missed the Millennium Development Goal of achieving Education for all by 2015. The struggle to afford school accommodation will continue, because of the lack of resources and high unit cost. Construction cost as time schedule for an identical school building vary by the implementing agency. This paper aims to study in-depth this multi-dimensional issue to find out the factors that lead to this variation, as well as the reasons for the high unit cost and lengthy periods of construction. To achieve this objective, comprehensive raw data that was resourced from agencies that are assigned to implement the largest part of the construction program along with data collected through questionnaires and semi-structured interviews were utilized. Complete sets of design and contracting documents of representative schools were used for deeper analysis and evaluation. The analysis shows that the employed design approaches lead to large structural elements and consequently to longer implementation period and 30% increase in cost. It also shows that contractors add up to 20% for the client’s procurement procedure, approvals, and payment cycle. Additionally, bidders price risks related to accessibility to building sites, availability of building materials, and how trouble-prone is the region. The findings are of relevance to researchers, education planners, and practitioners as they are of high importance to policy makers and financiers whose main concern is to meet the growing need for school accommodation.
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