Curing Agent, cements

NITCAL^® can be used as a curing agent, meaning that concrete will loose less water upon drying in the fresh state. The effect is most likely an indirect effect of the set acceleration.

Neat concrete with nominal w/c = 0.45, both without and with 2% NITCAL^® of the cement weight is chosen. The aggregate was natural sand and crushed granite gravel. Slump, air content, fresh density and 100×100×100 mm cube strengths (2 parallels) were tested and the results presented in the table below:

NITCAL®dosage	0%	2%
Slump (mm)	190	130
Air (vol%)	2.0	2.3
Fresh density (kg/m3)	2400	2395
1 day compressive strength (MPa)	23.8 +/- 0.3	26.5 +/- 0.4

Fig. 1: Photo of the wind rig with concrete specimen on the weighing platform.

Concrete rings were subjected to drying in a wind rig shown in Fig. 1 with a wind speed of 4.5 m/s over the concrete surface,temperature 20 +/- 1°C and relative humidity 43 +/- 3%. The mass loss as a function of time until 24 h is shown in Fig 2. The reference concrete had drying shrinkage cracks (Fig. 3a) after 24 h, while none was observed in the concrete with 2% NITCAL^®.

Fig. 2: Mass loss as a function of time for neat concrete with 0 and 2% NITCAL®.

2% NITCAL^®.

Fig. 3: Photo of the reference concrete (w/c=0.45) with marked up cracks (a) and the concrete with 2% NITCAL® without cracks (b) after the experiment.