Bentonite is able to meet the low permeability requirements.Thus

it was considered as buffer/backfill material in deep geological disposal repository for high-level radioactive nuclear waste.This clay plays a major role in retarding groundwater infiltration and radionuclide leakage.Usually

the infiltration prevention capacity of bentonites can be enhanced through improving compaction degree.The common and direct method for compaction degree improvement is to use high compaction energy

but this method is not economical in practice.Therefore

a low energy consuming method for compaction degree improvement was presented through adjusting agglomerate composition.First

the bentonite samples with different agglomerate compositions and water contents were prepared.Then the samples were compacted under force 45 kN.Finally

the compacted blocks with different compaction degrees were dried using liquid nitrogen freeze-drying method

and their pore distribution curves were obtained through mercury porosimeter.The compaction results show that

under the same compaction force（45 kN）

the dry density of the samples increases at first and then decreases with water content increasing.The optimum water content is about 20%.Among them

O-B and A-B-3 samples show double peaks in the compaction curves.Compared with O-B assembly

the A-B-3 samples are more easily to be compacted

with maximum dry density increasing from 1.64 g/cm3 to 1.72 g/cm3.This phenomenon proves that compacted effect can be improved significantly through adjusting agglomerate composition.The pore distribution curves show that pores with diameters range from 3.59μm to 0.188μm can be compacted effectively

and the compaction loading has little effect on pores with diameters around 26 nm.When water content exceeds 20%

there is no useful in improving compacted degree by increasing compacted energy solely.But

the compacted degree can be improved effectively by changing agglomerates size combination.