Factors analysis on autogenous volume deformation of MgO concrete and early thermal cracking evaluation

• MgO agent tailored to shrinkage-compensating hydraulic concrete was obtainable.
• Volume stability and distribution uniformity of MgO concrete was ensured.
• Concrete with 4% MgO with RT of 100 s had the best thermal cracking resistance.

Micro expansive MgO concrete was produced by batching conventional raw materials and expansion agent light-burnt MgO obtained by magnesite decomposition through rotary kiln. Many factors, including calcinations condition, batching method as well as variations in raw materials had been investigated. Results indicated that MgO agent tailored to shrinkage-compensating hydraulic concrete was obtainable by adjusting calcinations condition and uniform distribution of MgO in concrete was gainable by premixing MgO agent with other cementitious materials for 20 min and fed in the mixer all at once. Autogenous volume deformation of MgO concrete with reaction time ranging between 50 s and 200 s tended to stabilize after approximate two years development with no retraction or drop-back, and it exhibited good relationship with long-term water absorption of aggregates while alternative method to accurately quantify the effective periclase in clinker should be explored. Concrete with incorporation of 4% MgO agent with reaction time of 100 s was ranked the best in thermal cracking resistance and this solution was adopted for diversion tunnel sealing off in Xiluodu, Xiangjiaba and Baihetan hydropower stations.