In this study, the interaction between glucose and raw bentonite is investigated, aiming towards the preparation of a new type of water-retentive admixture for cement-based mortar. A series of laboratory experiments is designed and analysis of the results shows that glucose is indeed intercalated into the bentonite, which implies that a new kind of complex admixture (glucose-bentonite, G-Ben) has been prepared; the mechanism is analysed by X-ray diffraction and infra-red absorption spectra. The effect of G-Ben on both water retention and compressive strength of mortar is studied. The experimental results show that in the glucose mass ratio region of 4-7%, the water retention value obtained is higher than 94%, with no decline in the compressive strength of mortar cured for 28 d. Results confirm that the retardation of glucose is definitely inhibited while glucose plays its role in water-retaining. The findings in this study will be useful for the preparation of a low-cost admixture to take the place of expensive cellulose ethers. [ABSTRACT FROM AUTHOR]