André and coworkers [23] used marble industry waste. Baeza- Brotons and coworkers [24] used sewage sludge ash in Portland cement systems. Bravo and coworkers [25] used aggregates from construction and demolition recycling plants. Discarded tire rubber has been used by Thomas and Gupta   [26].

Our work reported below consisted of two series. In the first series we have mixed waste marble aggregates with CEM I 42.5 Portland cement. In the second series we have used CEM IV poz- zolanic cement—in order to evaluate the effects of natural poz- zolans. Moreover, fly ash has also been utilized to  replace  a portion  of  the cement.

2. Materials and methods

2.1. Cement

We have used Portland cement CEM I 42.5R, subsequently called A1, and CEMIV/B-M (P-LL) 32.5 R, subsequently called A5, (with trass) donated to us by Bati Soke Cement Factory. These materials comply with the requirements of the Turkish TS  EN 197-1 [27] standard, equivalent to the European  Standard  EN 197-1. These cement types are commonly used in construction. Their properties are summarized in Tables 1 and   2.

2.2. Fly ash

Fly ash (FA) used is in compliance with ASTM C 618 [28]. The use of FA as an additive in cement based concretes is classified in ASTM C 618 into two types, as class C and class F. Content of major oxides, SiO2 + Al2O3 + Fe2O3, must be more than 50% for class C and more than 70% for class F. Our FA belongs to the F type since its total of major oxides amounts to 79.4%. Our fly ash was obtained from the Yatagan thermal power plant, Mugla, Turkey. Its chemical composition is provided in Table 2. The respective Blaine fineness which serves as a measure of the particle size, or fineness  of cement    including    supplementary    cementitious    materials,   is

4860 cm2/g. The specific gravity is 2.55 g/cm3. Cement paste is cru- cial as an agent to keep together the aggregates and we expected that FA will increase the paste   amount.

2.3. Aggregates

Waste marbles were prepared as an aggregate by crushing and grinding  in  a  laboratory  mill,  then  sorting  via  sieves  into   two Physical properties of aggregates.

groups of coarse (>4 mm) and fine (<4 mm)  aggregates. Particle size distribution is displayed in Fig. 1. The maximum aggregate size was 25 mm. Size of aggregate and grading of mixture play an important role to get a good composite. Specific gravity and water absorption were determined according to ASTM C127 [29]; the results are reported in Table 3. Photographs of concrete with waste marble aggregates are shown in Fig. 2. The aggregates are calcare- ous (mostly containing calcium oxide), as seen already in Table 2.

2.4. Mix design

Mix design was made in accordance with the absolute volume method. Binder content was kept constant ast 350 kg/m3. To pro- duce ‘‘green concrete”, the cement content was kept low since cement production is responsible for about 8% of CO2 emission in the world. Further, cement was replaced with fly ash at 10%, 20% and 30%. One can assume that approximately 1.5% air is trapped in fresh concrete. The concrete compositions are listed in Table 4; the water/cement ratio is listed as W/C. The aggregate content con- sisted of 67% coarse and 33% fine aggregate. Marble dust was used in the amount of 6% in all mixtures. No superplasticizer was used because it was not necessary and moreover it would have increased the costs.

2.5. Mixing, casting, curing and testing specimens

Concrete mixtures were prepared in a laboratory mixer with the capacity of 150 dm3. In a typical mixing procedure, materials were placed in the mixer as follows: first coarse aggregates and fine aggregates and filler together, this initially dry material was mixed for 1 min; then cement and finally water were added. The total mixing time was 5 min. After the mixing procedure was com- pleted, slump tests according to ASTM C143 [30] were conducted