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The building defects are always of great concern for construction industry as they cause delays before handing over and increase maintenance costs during occupancy of the buildings. Due to the rapid development and population growth in Gaza Strip, many residential buildings and housing projects are being constructed in a short space of time, especially after Gaza war in 2014. Therefore, many errors and defects are expected to arise during the construction stage. The aim of this paper is to identify and rank the factors affecting the defects occurrence in the construction stage of the residential buildings in Gaza Strip. A survey was conducted in 134 randomly selected engineers working for engineering offices as design engineers, supervisors and project managers in Gaza Strip. The study revealed five most effective main factors during the construction stage, namely construction materials, factors due to inspections, factors due to construction equipment, factors due to constructions and factors due to construction management, respectively. The most important factors in each group were poor soil compaction, exceeding the allowable limits of verticality of the structural elements, insufficient reinforcement concrete cover, owner's negligence of inspections, absence of engineer in most of construction phases, using expired material, material or component failure, using corroded or secondhand reinforcement steel, using materials not of acceptable quality and not conforming to the specifications or design and lack of required equipment. This research is the first attempt at identifying factors affecting defect occurrence in the construction stage of residential buildings of the developing countries. The findings will be useful for the construction firms and regulatory bodies to deal with the critical factors affecting defect occurrence and device such policies that improve the design and construction of residential buildings.

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Cost effective management of construction and demolition waste (C&DW) has become a serious issue with increased construction activity and modern urban lifestyle which is damaging environment, eating up resources and causing rapid land use changes. These factors have influenced the construction industry significantly and therefore gained the practitioners' attention in recent past. New strategies of C&DW reduction management are being devised and reported; this research aims at providing a better C&DW management technique which will benefit the construction industry in terms of waste reduction and consequent cost-benefit. The main focus of this research is restrained to prefabrication of construction material and its effects on economy of tall buildings. The data collected from traditional methods for CDW management and prefabrication factories is based on interviewed surveys from project managers, quantity surveyors and experienced site managers. The collected data is then processed into System dynamics using "VENSIM PLE" by creating causal relationships with dependent and independent variables. Economic theory in contrast with conventional and prefabrication methods of construction has been incorporated in this study. Results show that usage of prefabrication technique proves to be more economical in managing C&DW. Construction waste management through prefabrication technique shows a reduction of cost around 79% as compared to that in construction through conventional methods. This suggests that prefabrication technique can considerably reduce C&DW as well as costs for its management accordingly.

This study examines the effect of elevated temperature on various properties of reactive powder concrete (RPC) containing varying percentages of recycled fine aggregates as sand replacement. Recycled fine aggregates were collected from two sources, i.e., demolished normal strength concrete and demolished RPC. The specimens were prepared using 25%, 50%, and 75% replacement of natural sand with recycled fine aggregates, exposed to two different curing conditions and were subjected to four temperatures, i.e., 25, 200, 400, and 600 °C. Later, the specimens were tested for mass loss, compressive strength test, split-tensile strength test, flexural strength test, and water absorption test at all temperature ranges. Results determined that although the mechanical properties degraded with the temperature rise, the recycled aggregates can be employed as a partial replacement of natural sand in RPC without causing a significant decrease in the performance of RPC, and can help to produce more sustainable RPC by using recycled aggregates.

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