**7. Conclusion**

*Sandy Materials in Civil Engineering - Usage and Management*

*Volume strain, axial strain responses for bio-cemented specimens (2.8–3.4% calcite).*

*Deviator stress, axial strain responses for bio-cemented specimens (2.8–3.4% calcite).*

expected for cemented specimens and are similar to gypsum cement.

ally similar to those of the lower calcite content.

confining stress of more than 200 kPa, the resistance becomes more obvious. This could be due to the lower calcite content in the more heavily stressed sample. It can also be noted that the cumulative response of the sample subjected to higher stresses shows less compression and more gradual expansion, which corresponds to a lesser effect of cementation. Thus, the calcite content is not only low but also the level of increased stress. Nevertheless, the general behavior patterns correspond to those

**Figures 19** and **20** show the effects of confining stress for a series of triaxial CID tests with calcite contents between 2.8 and 3.4%. Another UCS test is available for a saturated test in this cement content range, as previously following the rupture of the membrane. The UCS resistance of 820 kPa is again significantly higher than expected in the UCS tests of **Figure 4**, giving a value of 450 kPa for a calcite content of 3.4%. Reasonably consistent, all bio-cemented specimens showing increased in strength and stiffness as containment stress increases. For lower calcite levels, the rate of expansion tends to decrease as the level of stress increases, although the effect is less pronounced for those more cemented specimens. The trends are gener-

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**Figure 20.**

**Figure 19.**

The following concluding remarks are made based on the performance and behavior of bio-cemented Sydney sand:

