Lean concrete has been used for pavements or footpaths. However, the production of cement generates CO2, and thus to achieve green construction, we need to use less cement or substitute materials for cement. One method to reduce cement usage is to modify the aggregates used for lean concrete so that the bonding between cement and aggregates can be stronger and thus less cement can be used. A Microbial Induced Carbonate Precipitation (MICP) process has been adopted to treat aggregates used for lean concrete. The study shows that the aggregates modified by a MICP treatment could increase the cubic strength by 21.4% at 28 days of curing. Further studies were also carried out to use sea sand rather than river sand for lean concrete. The results also indicate that the strength of lean concrete made with MICP-treated sea sand was also increased by 24.8% at 28 days of curing when compared to untreated lean concrete made with river sand. This study is meaningful as the supply of river sand is much less than sea sand. On the other hand, sea sand is considered not suitable for lean concrete as chloride in sea sand will weaken the strength of lean concrete. This study appears to have established a method for sea sand to be used for lean concrete for pavements.