TESTING A 550 PORTLAND CEMENT

The high initial strength cement was investigated as a possible alternative to steam curing during precasting of concrete elements. A 500 m²/kg specific surface of cement resulted in high initial strength. In a summer climate the 550 portland cement is effective without plastificator admixture since the 1 day strength of the plastic concrete is about 30% of the 28 days' strength. With 2 m% plastificator the 1 day strength is about 40% of the 28 days' strength. If concrete is stored at 40°C for 24 hours the 12 -16 hours' strength is already enough to allow the elements to be removed from the form work. Lower cement content (250-300 kg/m³) results in higher tensile strength relative tothe compressive strength which is an advantage when from work is removed. Inceasing the cement content marginally increases the initial strength. During cold weather the role of grading (fine grinding) is more important