Mechanical properties of lightweight ceramic concrete

Concrete produced using a magnesium phosphate binder can exhibit faster strength gain and result in lower overall environmental impacts than concretes produced with Portland cement binders. This paper reports a study to develop and characterize the rheological and mechanical properties of lightweight ceramic concretes (LWCC) that use a magnesium potassium phosphate binder. The aggregate type and the overall mix composition were primary variables in the study. Aggregate types included expanded clay, expanded slate, and expanded shale. Crushed bottom ash aggregate from a local coal-fired thermal generating station was also used. The aggregates of a given material varied by size fraction and by surface characteristics in some cases. The test results showed that increases in the water/binder ratio increased the slump flow but had negligible influence on the setting time. The compressive strength and density of the LWCCs both decreased with increases in the aggregate/binder mass ratio and the water/binder ratio, regardless of the type of lightweight aggregate. The 28 day compressive strength and density ranged from 17 to 36 MPa and 1600 to 1870 kg/m(3) respectively. Regardless of the aggregate type, increasing the water/binder ratio also reduced the elastic modulus, modulus of rupture and direct shear strengths. Relationships were developed to directly relate these mechanical properties to the corresponding compressive strengths. The results indicate that LWCCs using a magnesium phosphate binder and lightweight aggregates can be formulated with rheological and mechanical properties suitable for structural applications.