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Burnt clay bricks are one of the most important building units worldwide, are easy and cheap to make, and are readily available. However, the utilization of fertile clay in the production of burnt clay bricks is also one of the causes of environmental pollution because of the emission of greenhouse gases from industrial kilns during the large-scale burning process. Therefore, there is a need to develop a new class of building units (bricks) incorporating recycled industrial waste, leading toward sustainable construction by a reduction in the environmental overburden. This research aimed to explore the potential of untreated coal ash for the manufacturing of building units (coal ash unburnt bricks). Coal ash unburnt bricks were manufactured at an industrial brick plant by applying a pre-form pressure of 3 MPa and later curing them via water sprinkling in a control shed. Various proportions of coal ash (i.e., 30, 35, 40, 45, 50, and 55%) were employed to investigate the mechanical and durability-related properties of the resulting bricks, then they were compared with conventional burnt clay bricks. Compressive strength, flexural strength, an initial rate of water absorption, efflorescence, microstructural analysis via scanning electron microscopy, and cost analysis were conducted. The results of the compressive strength tests revealed that the compressive strength of coal ash unburnt brick decreased with an increase in the content of coal ash; however, up to a 45% proportion of coal ash, the minimum required compressive strength specified by ASTM C62 and local building codes was satisfied. Furthermore, bricks incorporating up to 45% of coal ash also satisfied the ASTM C62 requirements for water absorption. Coal ash unburnt bricks are lighter in weight owing to their porous developed microstructure. The cost analysis showed that the utilization of untreated, locally available coal ash in brick production leads us on the path toward more economical and sustainable building units.

Many risks are associated with construction industry because of its highly diversified nature. Contingency reserves are designed and added to the project's estimate to cater for these risks. Different techniques are used worldwide to calculate contingency but unfortunately, Pakistan's construction industry continues to use the 'traditional percentage methodology'. In this technique, a preset amount, usually 5%-10% of the project's cost is added to the base cost estimate without identifying and analysing the risks. Time contingency is over looked in majority of the projects and if considered, it is based on subjective opinion of experts. This predetermined amount of uncertainty denotes the arbitrariness and becomes a reason for cost and time overrun in majority of projects in the country. This research aims to develop a framework that can circumvent this uncertainty by using probabilistic quantitative risk techniques. It proposes a probabilistic model for predicting total cost and duration of the project by translating the effect of risks. Rational contingency reserves for cost and time are predicted using the model by determining risk contingency factors.