Modification of Gypsum Products (Part II): The Effect of Drying Methods on The Compressive Strength and Surface Hardness of Modified Gypsum Products

Aims: Studying the effect of microwave drying on the physical and mechanical properties of modified Iraqi plaster and modified Plaster of Paris in comparison with open air drying method. Materials and methods: Two types of gypsum products were used in this study (Iraqi plaster, Plaster of Paris) with the combined additives (gum arabic 0.5%, calcium oxide 0.75%, and ferric oxide 0.2%) that incorporated within the two gypsum products. Physical and mechanical properties of the experimental gypsum products have been evaluated by measuring the compressive strength, surface hardness, and surface roughness. Mean, standard deviation, analysis of variance (ANOVA), and Duncan's multiple range statistical test were used to analyze the data. Results: ANOVA analysis showed that there was a significant difference in the compressive strength, surface hardness, and surface roughness between Iraqi plaster (I.P) and Plaster of Paris (P.O.P) with or without additives. Conclusions: At two hours time interval microwave oven drying, Iraqi plaster and Plaster of Paris samples were stronger than air dried samples; and microwave oven at 10 minutes for 800 Watt not only increased the strength of gypsum products samples, but also save time.