Compressive strength of green concretes with low cement and high filler content

It is estimated that by the end of the current decade, about 26% of clinker will be replaced by suitable alternative materials, among which limestone filler probably has the greatest potential due to its wide availability and relatively low price. Although codes allow as much as 35% of clinker to be replaced by limestone filler, the amounts used in practice are far less and average only 6-7% globally, with no growth trend over the past ten years. In order to use the great potential of fillers, it is necessary to know the key parameters that affect the properties of green concrete with low cement and high filler content in fresh and hardened state. For that purpose, a total of 18 concrete mixtures were designed, in order to analyse the effects of the percentage of cement replacement, water-cement ratio, but also the particle size of the applied filler. The results of experimental research show that at the same w/c ratio there is an increase in compressive strength with increasing percentage of cement replacement and that it is possible to make medium-strength concretes with a significantly reduced amount of cement (180 kg/m3) compared to traditional concretes. In this way, economic benefits can be achieved, but also the negative impact of the cement industry on the environment can be reduced. Unfortunately, the workability of such mixtures can be impaired to the extent that their practical application is prevented, so it is necessary to take further steps to solve this problem