Improvement of Gypsum Characteristics using (T.G.P.) and (P.V.A.) Additives

In this research an attempt has been made to study the effect of adding T. G. P and P. V. A. additives (by weight) separately and together on gypsum characteristics. The research plan consists of investigating two main gypsum properties, namelythe compressive strength and the setting time. According to the plan, the total number of gypsum mixes used is sixteen ( eight for each characteristic) which had been divided in to four groups according to T. G. P. and P. V. A. contents (by weight) 0.0 %, 0.4 % ( for T. G. P), and 0 %, 4 % ( for P. V. A. ). Each group was divided in to two sub-groups according to (water/gypsum) ratios (0.3 and 0.4). Each sub-group has three cubic (5*5*5) cm samples ( to take their average result). It was found that, the addition of only T. G. P. to the gypsum mixes, increases the setting time, but decreases the compressive strength of gypsum. It was also found that, the addition of only P. V. A. increases the compressive strength but has no obvious effect to setting time. Consequently, it was found that the addition of both T. G. P. and P. V. A. increases (slightly) the compressive strength and (obviously) the setting time. Finally, it was found that, decreasing (water/gypsum) ratio from (0.4) to (0.3), improves both the compressive strength and the setting time of gypsum mixes.