Reduction of the Carbon Footprint of Precast Columns by Combining Normal and Light Aggregate Concrete

To reduce the global emission of CO2 from the building industry, researchers, architects and manufacturers must consider new ways of constructing precast concrete buildings. Modern concrete columns and walls are not optimized to the applied load, and there is potential to save material. By creating a stronger column core and a lightweight concrete cover, it is possible to reduce the carbon footprint. A method is proposed to calculate such eccentrically loaded columns of two or more materials. The analytical method is developed for straight columns and columns with Entasis. Production of curved Entasis columns is possible by using textile molds due to the low mold pressure from the light aggregate concrete. Two column types are load tested to confirm the method. The CO2 emission is calculated for some column examples, and it shows that an optimized column geometry often leads to a reduced carbon footprint compared to regular columns. The concept is especially efficient for slender columns. Furthermore, the external light aggregate concrete layer ensures protection against fire if high-strength concrete is applied as the column core

Laboratory Tests of Low-Strength Mortars for Precast Concrete Buildings Designed for Disassembly

Direct reuse of precast concrete elements is possible if disassembly is considered in the design phase. An unusual way of designing for disassembly is to use “wet” joints as usual but to optimise the mortar to be less strong and, therefore, easier to remove at the end of the life of the building. A method is presented to test mortars with lime content to determine the shear capacity in the connection between mortar and concrete. Tests are performed with and without an applied normal force and with and without steel bars through the interface. The results show that applying a lime content to the mortar reduces the compressive strength, shear strength and flexural strength. Using steel bars in the connections increases the ductility from less than 1 mm to several mm at the point of failure. The results can be used in future checks of mortar joints in buildings, where it is required to have a minimum strength during the service life and a maximum strength when dismantling. The future mortar requirements will depend on the disassembly method