Experimental investigation on the monotonic, cyclic and post cyclic interfacial behavior of non-water reacted polymer and concrete

Abstract

The safety performance of geotechnical engineering is obviously affected by the interface characteristics of geotechnical materials. With widely use of the polymer in geotechnical engineering, the investigation for interface characteristics of polymer and concrete structure is necessary. In this paper, to investigate the interfacial shear properties of non-water reacted polymer and cement concrete, a series of displacement controlled monotonic direct shear (MDS) tests, cyclic direct shear tests (CDS) and post cyclic direct shear (PCDS) tests were carried out by using a newly designed direct shear test apparatus. The compressive strength of the polymer and cement concrete blocks are 2 MPa and 20 MPa respectively. The effects of vertical stress (50 kPa, 100 kPa, 150 kPa, 200 kPa), shear rate (1 mm/min, 2 mm/min, 3 mm/min, 4 mm/min and 5 mm/min), and cycle number on the investigated interface characteristics were studied. The results show that, with the increase of the vertical stress, the average peak shear stress of the interface gradually increases. As the vertical stress increase from 50 kPa to 200 kPa, the average peak shear stress increased by more than two times under various conditions. While with the increase of the shear rate, the average peak shear stress of the interface gradually decreases, but the reduction is small. And the reductions are all not more than 10% when the shear rate increases from 1 mm/min to 5 mm/min under all conditions; with the increase of the number of cycles, the average peak shear stress of the interface gradually decreases, and the decrease rate gradually decreases. When the vertical stress is 100 kPa and the shear rate is 3 mm/min, the average peak shear stress is reduced by 4.4% as the number of cycles increases from 1 to 5, while that is reduced by 1.2% as the number of cycles increases from 5 to 10; Under the given shear rate and vertical stress, the interface between polymer and cement concrete shows the shear softening in both MDS test and PCDS test. However, under the same vertical stress and shear rate, the shear strength and shear modulus of the MDS tests are greater than those of the PCDS tests. While the differences for MDS and PCDS are almost all not more than 5 kPa; with the increase of vertical stress, the shear strength and shear modulus of MDS test and PCDS test increase gradually. The shear strength increased by more than two times and the shear modulus increased by more than one times as the vertical stress increases from 50 kPa to 200 kPa. The shear strength is reduced by not more than 6% and the shear modulus is reduced by not more than 11% as the shear rates increase from 1 mm/min to 5 mm/min. The apparent cohesions are obviously influenced by cyclic direct shear, while the effective friction angles are a little influenced by CDS.