Blockchain is an emerging backbone technology behind different crypto-currencies. It can also be used for other purposes and areas. There are different scalability issues associated with blockchain. It is important to know the in depth structure of blockchain by identifying common behaviors of the transactions and the effect of these behaviors on the nodes of the network. Dominant set approach can categorize the blockchain transactions into different clusters without mentioning number of clusters in advance. The experimental evaluation of blockchain transactions shows better clustering accuracy of dominant set approach than existing method of central clustering approach.