Modified calcium oxide expansion agent for cement concrete

The invention provides a modified calcium oxide expansion agent for cement concrete and a preparation method of the modified calcium oxide expansion agent. The modified calcium oxide expansion agent for the cement concrete has the specific surface area of 100-600m /kg and is prepared from long-chain fatty acid and a calcium oxide expansion agent, wherein the surface of the calcium oxide expansion agent is coated with the long-chain fatty acid, and the mass ratio of the calcium oxide expansion agent to the long-chain fatty acid is (90: 10) to (999: 1). According to the modified calcium oxide expansion agent for the cement concrete, the humidity resistance is improved, the hydration of a plastic stage of the cement concrete is reduced, the hardened expansion quantity of the concrete is increased, and the concrete cracking resistance of the calcium oxide expansion agent can be improved.