Stress generation in mass concrete blocks with fly ASH and silica fume – An experimental and numerical study

A new Economic city project is being built by Saudi Aramco in Jizan, off the coast of Red Sea in Saudi Arabia. It includes a refinery, a sea port and associated infrastructures. The wharves at the sea port is constructed using a large number of massive concrete blocks, 11 m to 13.7 m long, 1.9 m high and 2 m in width. Due to heat of hydration of the cement, temperatures in excess of 70 °C at the core of the block could result in delayed ettringite formation (DEF), and excessive temperature differential between the core and the surface would result in cracking at the surface. Both phenomena would seriously compromise the durability of the blocks in marine environment. To ensure long-term durability and control temperature rise and differentials, the concrete blocks for the wharves were constructed using concrete mix in which 25% of Portland cement was replaced with Class F fly ash. For achieving strength and durability, additional 7.5% of cement was replaced with silica fume. This paper presents the field, experimental and numerical investigation conducted for a typical mass concrete blocks used in the wharves. Evolution of temperature at the core and the surface of these blocks, compressive and tensile strength of the concrete mix were measured. The heat of hydration for the concrete mix was determined in laboratory using semi-adiabatic calorimeter. Nonlinear finite element analyses were carried out to investigate the effect of heat of hydration and environmental loading stress generation and crack development in the blocks.