Rahman Youssef’s research while affiliated with Al-Balqa Applied University and other places

This experimental investigation is intended to study the mechanical properties of natural building stone usually used in the construction of load-bearing concrete backed stone masonry walls and columns used in the construction of the majority of buildings in Jordan and some middle-eastern countries. Six types of building limestone, brought from different quarries in Jordan, were used in this study. The characteristics studied were the stress-strain curves, the modulus of rupture, the modulus of elasticity, the Poisson ratio and the compressive strength. An experimental method is suggested to determine the modulus of elasticity of limestone; the results were compared with those obtained from stress-strain curves carried out on prisms. The results indicated that there are remarkable differences in strength and behavior of stone specimens loaded parallel to the bedding (or rift) and perpendicular to it in both dry and wet conditions. It is also indicated that the differences in results of the modulus of elasticity obtained by the suggested method and the stress-strain curves are not significant. On the basis of the test results a new formula is suggested for estimating the modulus of elasticity of limestone when compressive strength is known.

The soil structure is very important in understanding the behaviour of soil particularly in unsaturated case. The behaviour of unsaturated soil is highly influenced by microscopic structure of soil. Many electronic and optical microscopic observation have been made in this study. This paper shows the water is never been uniformly distributed with the soil matrix. This affect the water flow, capillarity and shear strength in unsaturated soil. The smaller the particle radius has the greater effect on the behaviour of unsaturated soil.

Air exists in soil as a free continuous phase or as air-bubbles. The air-bubbles exist as free which are surrounded by water in the soil pores, or as bounded air-bubbles if they have a contact with the soil particles. Gas bubbles are present in the soil as the saturation drops than unity and greater than 57%. The air is continuous phase with atmospheric air pressure while the water is discontinuous between the soil particles when the degree of saturation is less than 20%. On the other hand, the air and the water are continuous when the degree of saturation is between 20 % and 57%.

In Jordan, considerable amount of construction activity is carried out at relatively shallow depths where soil is likely to be unsaturated and subjected to low stresses level. One particular example is the pavement. The occurrence of damage to road founded on weak subgrade in Karak. Therefore, stabilization of the base course, sub base course and subgrade is essential. The soil will be treated by using quick lime with different percentage. An experimental program was designed to study the behavior of soil as the percent of additive agent changes. Direct shear was used for the testing program on an unsaturated silty clay that was carried out as part of this research program. The results showed that; the geotechnical properties have been improved. The reaction time is a significant parameter which the strength improved as the time increases.