New Composite Cement for High Early Strength Concrete

Even small repairs on roads and runways are time consuming and lead to long time obstructions. Normal cement type mortars and concretes do exhibit iallier long hardening times and are therefore, not suitable for fast track repair. Non cementitious repair materials like resin types have other disadvantages as being only usable in dry conditions to ensure complete bonding between old concrete and repair material. A new composite cement is now presented which is based on burnt oil shale, a material which is produced on burning oil shale from Lias t at ca. 8000 C. The resulting material hardens hydraulically but very slowly. With the introduction of an activator system this material exhibits very high early strength at 3 - 5 hrs. with a remarkable workability of 30— 40 minutes. An accelerator system for cold weather applications and a retarder for higher temperatures extend the possibility of applications to various fields. Lab results as field test results are presented.