a b s t r a c t ：We have used waste marble aggregates, marble dust and fly ash from thermic power plants as fillers in concretes for replacing natural aggregates. We have used two different kinds of cements. After curing, we have determined the workability (by slump tests), air content, unit weight, Schmidt hardness, ultrasound pulse velocity, compressive strength and carbonation depth. The concretes containing waste marble at least match or exceed the workability and strength of the control concrete type. Fly ash significantly improves the workability. Utilizing waste marble aggregate at the replacement ratio of 100% along with waste marble dust, fly ash and pozzolanic cements in concrete leads to lower cost – achieving at the same time environmentally friendly production process with decreased consumption of natural resources and energy. Our work also contributes to enhancement of sustainability by finding a use for marble waste and fly ash.

1. Introduction

More and more materials to be used for any application are con- sidered not only from the point of view of properties and cost, but also from the point of view of sustainability [1–3]. Therefore, mate- rials based on waste have an advantage over virgin ones. In the case of concretes, other factors that need to be considered are light weight [4,5] and  the service environment   [6].

Turkey has significant marble reserves that constitute over 40% of total worldwide reserves. Over 7 million tons of marble are pro- duced in Turkey annually. Egypt produces over 50 different types of marble and granite—with annual production of    approximately

3.5 million tons [7]. While marble blocks are being processed, mar- ble wastes are produced as dust and aggregates. Stored marble waste constitutes an environmental hazard [8]. Already in 2009, 1400 tons of waste marble per day were stored in depots in Turkey [9]. Similarly, waste from the cutting and sawing process in Brazil- ian decorative stone industry constitutes 20–25% of the total vol- ume of the blocks [10]. Likewise, Hebhoub et al. [11] have reported on the considerable waste generated during marble pro- duction; almost 70% of the mineral gets wasted in the mining, pro- cessing and polishing stages—with an obvious impact on the environment.

The environmental impact of marble waste could be lowered in a cost-effective manner by utilizing the waste material in value- added applications. Some of us have demonstrated [12] the feasi- bility of using marble waste as aggregate in concrete paving blocks. Further, it has been shown in the same work that blocks prepared from a cement called CEM with marble waste substituted for a por- tion of the aggregate exhibits suitable mechanical strength along with improved freeze-thaw durability and abrasive wear resis- tance in comparison to   controls.

Depending on the application, a choice has to be made between mineral and polymer concretes [13]. Previously we have consid- ered the use of marble powder and other fillers in polymer con- cretes [14]. We now discuss effects of fillers in mineral concretes that are byproducts of industrial processes, therefore quite cheap, and finding use for these byproducts contributes to protection of our environment.

Fly ash (FA) is a by-product of coal thermal power plants. There are estimates showing that fly ash is created worldwide in the amount of some 500 million tons every year [15,16]. There is no dispute that fly ash by itself causes environmental pollution. Stor- age costs of fly ash are quite high—and constitute a palliative only. Given those costs, at some point the storage would have to stop—even if it suddenly became more affordable. Clearly progres- sive accumulation and storage of fly ash goes against the very idea of sustainability.

There are possibilities of using fly ash in mortar and concrete, an effort in which we also participate [16–20]. Thus, it is already known that fly ash improves mechanical properties as well as freeze–thaw resistance, sulphate resistance, alkali–silica reaction, durability and abrasion resistance when used as a supplementary cementitious material. Also, shrinkage and permeability of hard- ened concrete are decreased, a consequence of the filling of   micro- ditional fine and coarse aggregates fully by marble fine and coarse aggregates.