Feasibility of use of glass powder and/or ground granulated blast furnace slag in place of cement in ultra high performance concrete

Abstract

 Reducing the amount of cement in UHPC mixture is feasible with the partial uses of GP and/or GGBFS.  The compressive strengths of 28 and 56 day of UHPC increased with 12.5% GGBFS use.  The impacts of GP and GGBFS on compressive strength are more apparent with the steel fiber and steam curing Ultra High Performance Concrete (UHPC) is a new generation concrete type having very high concrete compressive strength, post-cracking tensile behavior, durability and mechanical properties. The amount of cement used in the UHPC is higher than conventional normal strength concrete. In recent years, some additive materials such as, glass powder (GP), ground granulated blast furnace slag (GGBFS) or fly ash can be used to reduce the negative effects of cement due to high cost, environmental effects and shrinkage. These materials fill voids between the cement particles, resulting a less permeable concrete. These materials react chemically with steam or pressure curing due to their pozzolanic properties. Thus, they exhibit binding agent and hence, have significant potential to improve the mechanical properties of concrete. Figure A. The impacts of GP and GGBFS uses on concrete compressive strengthPurpose: In the study, the feasibility of GP and / or GGBFS uses in place of the cement in the UHPC content has been investigated in terms of concrete compressive strength. However, the effects of these additives on the compressive strength were investigated for the cases of steel fiber inclusion and / or steam curing application. Theory and Methods:The total of 16 UHPC mixtures with single, double and triple binder systems were produced by the independence and dual-uses of GP and GGBFS of 12.5% and 25% by volume as well as additive-free control mixture. The compressive strengths of cube specimens for each mixture were determined for 7, 14, 28, 56 and 90 days by considering with and without steel fiber and steam curing. Results:The test results showed that while the compressive strengths were decreasing trend at all concrete ages as the GP amount increases, relative differences were very small at 28 day and beyond. While the compressive strength of UHPC mixture containing the GGBFS of 12.5% increased at the concrete ages of 28 and 56 day, the strength decreased for the ratio of 25%. However, the compressive strengths showed a slightly decreasing trend for the dual-uses of GP and GGBFS in the mixture. Conclusion:It can be deduced that the target compressive strengths of UHPC can be obtained with the partial uses of GP and/or GGBFS by reducing the amount of cement in the mixture in order to obtain eco-friendlier and more economical concrete. Noted that the effects of these additive materials on the compressive strength become more apparent with the inclusion of steel fiber to the UHPC mixture and steam curing application.