Influence of blended powders on properties of ultra-high strength fibre reinforced self compacting concrete subjected to elevated temperatures

Ultra-High Strength Fibre Reinforced Self Compacting Concrete (UHSFRSCC) is in great demand for use in construction projects around the globe. Unless fillers are utilized in this concrete, its production will come at an excessive environmental cost due to the high Carbon footprint of Portland cement. A gap in the published literature was identified, where quaternary mixes, containing Portland cement with three fillers, incorporating fibres, and achieving ultra high strength, were not cited. In this study ternary and quaternary mixes were designed and produced, satisfying the European Guidelines for SCC, with compressive strengths exceeding 115 MPa. Some mixes had compressive strengths between 125 – 150 MPa, which were not previously reported in the literature. The mixes contained Silica Fume (SF), Metakaolin (MK), Limestone powder (LS) as partial Portland cement replacement and quartz powder (QP) as partial sand replacement. Basalt Fibres were added to reinforce the matrix. Compressive & tensile strength of the mixes along with UPV, sorptivity, absorption and SEM Micro-structure features were studied at ambient temperature and after the samples were exposed to either 200 or 300 oC; since the behavior of HSC at elevated temperature is always a cause for concern. The active and inert fillers exhibited a synergic behavior at all temperature conditions. The mix containing: 15% SF, 5% MK, 20% LS and 34% QP achieved the best performance. Compressive and splitting tensile strength improve by 10% and 17% while sorptivity and absorption decline by 40% and 29% respectively at ambient temperature. Residual compressive strength improved by 10% and 19% while, residual splitting tensile strength significantly increases by 21% and 28% after exposure to elevated temperatures 200°C and 300°C respectively. Meanwhile, residual sorptivity decreases by 39% and 38% after exposure to these elevated temperatures. Microstructure properties supported and agreed with the mechanical and permeation characteristics results. The results will contribute to the development of UHSFRSCC in hot weather countries

Developing an optimized strategy achieving design flexibility in small-area units: Case study of Egyptian economic housing

Some countries, especially Egypt, have sought to use small housing units as a solution for housing financial problems. Unfortunately, householders faced various problems with units’ design which obliged them to either leave their units, modify them to meet their needs, or live in their poorly designed units. The current work aims at obtaining an optimized design strategy through applying the “design flexibility” concept on economic housing units. The achieved strategy was investigated on a selected case study in Egypt, namely: Mubarak housing for youth. This strategy led to area optimized utilization. Hence, involving design flexibility makes the units more suitable and affordable for individuals, Fundable for the economy and friendly for the environment (reduce wasted material and energy). Therefore, design flexibility matches the sustainability principles (social, economic and environmental). Keywords: Optimization strategy, Design flexibility, Sustainable design, Housing problems, Economic housin

Impact of Phase Change Materials on Cooling Demand of an Educational Facility in Cairo, Egypt

Heat gains and losses via building envelopes are impacted by varied characteristics such as geometry, orientation, properties of the building materials, and the type of construction and its interface with the exterior environment. Current studies are investigating the use of phase change materials (PCMs) characterized by high latent heat and low thermal conductivity that may cause temperature time lag and reduce amounts of heat transferred through building envelopes. The prime objectives of this research are evaluating zones’ energy consumption by type for an educational facility in a dry arid climate, examining the effects of a PCM (RT28HC) and polyurethane insulating material, comparing these effects to the existing situation with respect to cooling energy savings and CO2 emissions, and studying the effect of varying PCM thicknesses. The working methodology depended on gathering the real status and actual material of the building, constructing models of the building using Design Builder (DB) simulation software, and comparing the insulation effect of incorporating polyurethane and phase change insulating materials. A parametric study evaluated various PCM thicknesses (6, 12, 18, 24, 30, and 36 mm). Validation was performed primarily for a selected year’s energy usage; simulation results complied with field measurements. The results revealed that an 18 mm PCM had a high efficiency regarding thermal comfort attributes, which reduced cooling energy by 17.5% and CO2 emissions by 12.4%. Consequently, this study has shown the significant potential of PCM regarding improved energy utilization in buildings

Impact of Adjuvant Radiotherapy in Patients with Central Neurocytoma: A Multicentric International Analysis

Background: Central neurocytoma (CN) is a rare tumor accounting for <0.5% of all intracranial tumors. Surgery ± radiotherapy is the mainstay treatment. This international multicentric study aims to evaluate the outcomes of CNs patients after multimodal therapies and identify predictive factors. Patients and methods: We retrospectively identified 33 patients with CN treated between 2005 and 2019. Treatment characteristics and outcomes were assessed. Results: All patients with CN underwent surgical resection. Radiotherapy was delivered in 19 patients. The median radiation dose was 54 Gy (range, 50–60 Gy). The median follow-up time was 56 months. The 5-year OS and 5-year PFS were 90% and 76%, respectively. Patients who received radiotherapy had a significantly longer PFS than patients without RT (p = 0.004) and a trend towards longer OS. In addition, complete response after treatments was associated with longer PFS (p = 0.07). Conclusions: Using RT seems to be associated with longer survival rates with an acceptable toxicity profile