Development of UHPC concrete using mostly locally available raw materials

Abstract: The concrete technology has during the last century changed dramatically where the concept of high strength concrete has gone from 30MPa to well over 100MPa. UHPC has many areas of application and is used more and more frequently in all manner of structures. It is also a suitable concrete in areas and environments that are demanding and harsh for the concrete due to its overall excellent durability properties which suggest lifespans of reinforced structure elements that far exceeds what is economically available to design for today with a low cost of maintenance. The aim of this research was to produce Ultra High-Performance Concrete using mostly locally available materials. Tests were made on the binary materials where the particle packing was optimized through the Punkte method. A series of smaller mortar mixes was made where the effect of different proportions of i.e. silica fume, flyash, superplasticizer had on the concrete mix. The fresh and hardened properties of the mix as mini cone flow, slump flow, density, compressive strength and flexural strength was evaluated to obtain a mix which exhibited the properties sought for, high strength and good workability. The results showed that it is difficult to find an optimum mixture since the design of a recipe always has compromises and rarely all criteria’s can be met fully. The concrete produced had a W to C ratio between 0,21, 20wt% of silica fume, 4,5wt% of superplasticizer and max filler size of 1mm. Some mixes of the concrete were also produced with flyash replacement and with steel fibers. This resulted in concretes exhibiting compressive strength over 140MPa, flexural strength of 18MPa without fiber reinforcement and with self-consolidating properties. The replacement of cement with 30wt% of flyash resulted in better workability and long term(1year) compressive strength almost equaled the concrete without flyash replacement.