The investigation on the pozzolanic reactivity of different materials and their effects on the properties of ultra-high performance concrete

One of the disadvantages of ultra-high performance concrete (UHPC) is high content ‎consumption of cement which leads to high level of material cost compared to ordinary ‎concrete. Therefore, finding appropriate supplementary cementitious materials could reduce the environmental CO2 ‎emission due to the reduction of cement consumption and may enhance the mechanical properties ‎of ultra-high performance concrete. In this study, the pozzolanic activity of five ‎industrial waste materials including silica fume, glass powder, copper slag, coal waste and silica floor has been investigated.‎ It is expected that these materials in concrete can react with calcium hydroxide from ‎cement hydration and produce C-S-H compounds. The pozzolanic, mechanical and diffusivity properties of ultra-high performance concrete ‎made from the aforementioned materials ‎as well as the pozzolanic properties were studied under standard and thermal treatment from 3 days up to 120 days.‎ The results showed that the temperature and time are two significant factors on the ‎performnce and pozzolanic activity of materials and use of higher curing temperatures led to improved mechanical properties for the mixtures containing silica fume. However, higher curing temperatures led to weaker durability and mechanical characteristics of UHPC with the other supplementary cementitious materials.