Improving the Properties of Construction Plaster Mortar by using Portland Cement

Abstract

The study was conducted to investigate the physical properties of plaster by adding different percentages of the normal cement and white cement. These were 2.5%, 5% and 7.5% of the weight of the plaster. All the required laboratory tests were performed and the results were compared to the Iraqi Standard No. (27) for the year 1988 and also compared the results with the results of plaster mortar without adding any ratios of normal and white cement  in order to know the extent of change in the properties of plaster. The outcomes of the plaster softness test showed that the residual weight of the plaster on the sieve (1.18 mm) was equal to zero. This means that the  softness of the plaster used was  (0%)  and conformed to the Iraqi standard. Also, the results of the test of the cohesion time of plaster when adding percentages of normal cement, it is clear that the best proportion was (5%) because the time of cohesion decreased clearly and this decline is acceptable and in accordance with the Iraqi standard, However, the results of the test of the cohesion  time of plaster when adding percentages of White cement showed a huge reduction in the time of cohesion in comparison to those of normal cement and was contrary to the Iraqi standard. So, it can be said that it is possible to rely on the addition of ratios from normal cement better than the percentages of white cement due to a logical coherence time and conform to the standard . The results of the test of compressive strength of plaster showed and for all the cases mentioned that they were all in accordance with the Iraqi standard, and the best proportion was when adding (5%) normal cement because it gave the highest compressive strength from the other ratios. As for the addition of percentages of white cement, there was no increase in compressive strength when compared with the first and second cases, except at the ratio of (7.5%).