# Long-Term Deformations and Mechanical Properties of Fine Recycled Aggregate Earth Concrete
## 3 Results
### Long-Term Deformations
#### 3.1.2 Creep  
Figure 5a shows the basic creep deformations \(\varepsilon_{BC}(t)\) (after subtracting the elastic and autogenous shrinkage strains) and the total long-term deformations \(\varepsilon_{TLTD}(t)\) (which are the deformations of drying creep specimen minus the elastic strains) of NS and RS mixtures. Figure 5b shows the specific basic creep, which is the basic creep deformation per unit stress. The results show that the basic creep increases with RS mixtures following the same tendency as that observed with ordinary concrete. It may be worthwhile to state that pre-saturation was carried out to RS in our study, while additional water was added rather than pre-saturation in other study [38], and both studies reported an increase of basic creep. Thus, this indicates that basic creep increases with recycled aggregate regardless of the way adopted for RS saturation. The hard grains hardly creep. [PERSON] et al. [39], who declared higher basic creep tendencies in recycled aggregate concrete, verified that hard grains corresponded to almost 45% and 26% of the microstructure of natural aggregate concrete and recycled aggregate concrete, respectively. This validates the statement that the lower basic creep in NS earth concrete mixture may be attributed to a, probably, higher quantity of hard grains in its microstructure compared to RS mixture. Furthermore, creep can be caused by the transfer of water from micropores to macropores under a pressure [40]. Knowing that RS comprises of more water than NS and has different porosity distribution, more water may have been transferred to the larger pores due to the applied stress causing more of creep strain. The total long-term deformation \(\varepsilon_{TLTD}(t)\) also increases when RS replaces NS. While higher shrinkage in recycled aggregate mixtures is being attributed to porosity and water absorption [35], pore size distribution, lower elastic modulus [36], recycled aggregate source and particle size distribution [41], the total creep is being linked to those same factors [23]. For instance, [PERSON] el al. [42] carried out a scanning electron microscope in order to show that recycled aggregate concrete is of higher porosity to justify its higher creep deformations. In the following study, the replacement of NS by RS in earth concrete reported a 121% increase in \(\varepsilon_{TLTD}(t)\) from 3085 to 6829 \(\upmu\)m/m. Regarding basic creep, it increases by 12% from 445 to 500 \(\upmu\)m/m as RS replaces NS. On the other hand, knowing that RS specimen is of lower strength than NS specimen, it may be worthwhile to state that the basic creep per unit stress as shown in Figure 5b increases by 128% from 327 to 746 \(\upmu\)m/m.MPa. Figure 5: The basic creep and total long-term deformations (**a**) and specific basic creep (**b**) of NS and RS mixtures. Figure 6 shows the strain summation \(\varepsilon_{S}(t)\) of the individual strains from one side (without elastic strain for a better verification of \(\varepsilon_{DC}(t)\)) and \(\varepsilon_{TLTD}(t)\) related to DC specimen from other side. The difference between the two components represents \(\varepsilon_{DC}(t)\) or [PERSON]'s effect. As already shown, \(\varepsilon_{BC}(t)\), \(\varepsilon_{DS}(t)\) and total \(\varepsilon_{TLTD}(t)\) increase while \(\varepsilon_{AS}(t)\) decreases when RS replaces NS. The replacement of NS by RS also increases the drying creep by 153% from 764 to 1935 \(\upmu\)m/m. Regardless of the microstructural variations, it is important to highlight the microcracking effect. Due to drying, microcracks are formed on the surface of the specimen. Such cracks will not fully close and, thus, they are considered irreversible deformations. These deformations reduce the shrinkage of the specimen. RS drying specimens are more prone to develop drying cracks than NS, which is mainly due to the higher drying shrinkage [43]. The structural desiccation creep effect is linked to a reduction in microcracks generated by desiccation.