Study on microstructure and bond strength of interfacial transition zone between cement paste and high-performance lightweight aggregates prepared from ferrochromium slag

- High-performance lightweight aggregates (HPLWA) are successfully fabricated by using ferrochromium slag, fly ash and bauxite as raw materials.
- The high-belite sulphoaluminate clinker is prepared and coated on the surface of HPLWA by one-step sintering technique to obtain an outstanding surface reactivity of aggregates.
- The ITZ properties including the hydration products and porosity profile were investigated by means of SEM and BSE imaging technique.
- The interfacial bond strength between HPLWA and cement paste is quantitatively analyzed by a three-point bending test.

In this study, high-performance lightweight aggregates (HPLWA) are successfully fabricated by using ferrochromium slag, fly ash and bauxite as raw materials. Besides, the high-belite sulphoaluminate clinker is prepared and coated on the surface of HPLWA by one-step sintering technique to obtain an outstanding surface reactivity of aggregates. The results show that the prepared HPLWA are made up of two parts, the inner porous ceramics which consist mainly of cordierite and spinel and the outer modified layers composed of belite and sulphoaluminate. The inner porous ceramics afford the HPLWA high compressive strength more than 6 MPa and low water absorption less than 2 wt%. Furthermore, the outer modified layers would weaken the compressive strength and increase the water absorption of HPLWA, but they endow a dense microstructure and high bond strength of interfacial transition zone (ITZ) between HPLWA and cement paste.