**3.1 Characterization of FSC in fresh state**

The results of the ceramic waste effect on the slump flow diameter and V-funnel flow time for FSC mixes are given in **Table 3**. The results displayed that the workability of FSC decrease with the increase of ceramic waste. This decrease in workability is maybe due to the high water absorption (**Table 1**), angular shape and rough surface texture of -ceramic waste grain compared to natural sand, which had a rounded shape of the grains (**Figures 3** and **5**). The decrease in workability of concrete, made with CW, was observed also by Abadou et al. [2] Guendouz and Boukhekhal [23] and Daniyal et al. [24].

In order to limit the number of compositions and to be able to compare them in the hardened state on a common basis, the workability was fixed by a constant slump flow diameter, with a value close to 27 mm, and fixed water to binder ratio at 0.4. The workability measure was adjusted by varying the superplasticizer quantity for each mixture contains ceramic waste as reported in **Figure 8**. It is clearly shown from this figure that superplasticizer demand increased with the increase of ceramic waste content in FSC.

**Figure 9** shows that the substitution of sand by ceramic waste causes a slight decrease in bulk density of mixes, which is probably due to the lower density of the ceramic waste aggregate grains compared with natural sand (**Table 1**). The decrease in density of concrete made with CW was proved also by many authors [5, 10, 25–29] which reported that the use of ceramic waste as aggregates reduced the concrete density.


### **Table 3.**

*Properties of FSC mixes at fresh state.*

**Figure 8.** *Superplasticizer need of fresh FSC as function of ceramic wastes content.*

**Figure 9.** *Bulk density of fresh FSC as function of ceramic wastes content.*

### **3.2 Mechanical properties of FSC in hardened state**

The results of compressive and flexural strength for all FSC mixes, at 28 days of age are presented in **Figures 10** and **11** respectively. This results show an improvement in compressive and flexural strength of FSC mixes with ceramic waste for all ages compared to FSC without ceramic waste. An increase of about 30 and 57% was observed at 28 days in compressive and flexural strength respectively, for a replacement ratio of 25% of sand by ceramic waste. This increase in mechanical strength is due to the hardness of ceramic waste grains compared to those of natural sand, and to their rough and irregular shape which fill the void. This later led to higher frictional resistance and improves their good adhesion with the cement paste (**Figure 12**).

Similar results were observed by Abadou et al. [5] for dune sand mortar containing CW. They found an increase in compressive strength of dune sand mortar with 40 and 50% of CW. Elçi [10] has reported similar mechanical properties to those of traditional limestone concrete when using ceramic as recycled aggregates. Anderson et al. [27] studied also the effect of ceramic waste on concrete mechanical strength; they observed an increase in concrete strength with the incorporation of fine ceramic aggregates along with the coarse. Tennich et al. [30] reported that the compressive strength of concrete containing CW is higher than those of concrete made with natural aggregate.

The results of modulus of elasticity tests carried out on the different FSC mixes at 28 days are summarized in **Figure 13**. As shown in this figure, the elastic modulus of all concrete mixes, increases when ceramic waste aggregates content increases.

**Figure 10.** *Effect of ceramic waste on compressive strength of FSC.*

*The Effect of Ceramic Wastes on Physical and Mechanical Properties of Eco-Friendly... DOI: http://dx.doi.org/10.5772/intechopen.95041*

**Figure 11.** *Effect of ceramic waste on flexural strength of FSC.*

**Figure 12.**

*SEM image showing the good adhesion of CW with cement matrix in FSC.*

Its value varies between 25 GPa for control flowable sand concrete, and 34.92 GPa for mixtures containing 25% of CW, with a gain of about 28.4%. This increase on modulus of elasticity is due to the high compressive strength of mixtures, the angular particles shape that occupy the voids between sand grains, and to the better adherence between CW and paste. Thus, FSC mixes become more compact and, as a consequence, the modulus of elasticity increased. The modulus of elasticity may be directly related to the compressive strength. The results agree with those in [27] for CW aggregates. Tennich et al. [30] studied the effect of partial replacement of natural sand by ceramic waste with different percentage (0, 20, 35, 50, 65, 80 and 100%) on the elastic modulus of natural concrete. It observed that the elastic modulus of ceramic waste series increased by 27% with 100% replacement. Abadou et al. [5] also reported that the mortar incorporating ceramic waste has a higher modulus of elasticity compared to the ordinary mortar. Contrarily, Elçi [10] found that there was a decrease of in modulus of concrete made with CW compared to reference concrete.
