Colloidal gels have a large number of applications in personal care, pharmaceutical, food products and engineering industries. The interaction between particles in a colloidal dispersion can be tuned to induce aggregation leading to the formation of colloidal gels which consist of a volume spanning particles network. Rheological behaviour of such particulate gels are influenced by the size, shape, concentration and colloidal interactions. In particle mixtures, relative concentration, size ratio and charge ratio provide additional handles to control the rheological behaviour. In this work, hetero-aggregates of silica based nanoparticles at high concentrations are studied using rheology. The overall goal of this study is to provide insights into mechanism of gel formation, microstructural features and ageing behaviour of oppositely charged particle gels. The steady and oscillatory shear are used to characterize the response of the aggregates formed from oppositely charged particles at different mixing fractions and concentrations. The storage modulus and loss modulus increase with the concentration. Stability of gels with time has also been investigated. Steady shear test shows that these gels exhibit yield stress behaviour. Flow visualisation of the gels has been carried out for better understanding the nature of flow.