Advances in concrete technology

Abstract

This chapter presents a survey of recent advances in concrete technology, with a focus on research performed at the Center for Advanced Cement Based Materials (ACBM Center) at Northwestern University. It also discusses an ultra-high-strength concrete (UHSC), with compressive strength of 200MPa. Fiber reinforcement is used to overcome the inherent brittleness and increase the tensile strength of concrete, especially high- and ultra-high-strength concrete. Fiber-reinforced cementitious composites can be designed for specific applications with the use of special processing techniques, such as extrusion, and hybrid fiber reinforcement. Significant reductions in drying shrinkage are achieved with a newly developed shrinkage reducing admixture. Construction costs can be reduced with the use of self-compacting concrete (SCC), which does not require vibration at placement. The design of SCC is facilitated with a newly developed rheological model. A nondestructive evaluation technique is developed to monitor the hardening process of fresh concrete. It uses stress waves to determine mechanical properties, the presence, location, and extent of damage, or the degree of hydration of concrete structures. Stress pulses are applied to the structure, and the transmission or reflection of the resulting waves or the vibration response of the structure is measured.