Papers by Keyword: Polymer Modified

Abstract: Shrinkage of repair material is the major factor inducing cracking in concrete repairs. Induced cracks in repair materials are due to restrained shrinkage. The ring test is commonly used to assess the potential for restrained shrinkage induced cracking due to its simplicity and versatility. The restrained ring test is becoming widely used as a standard test method to assess the potential for early-age cracking in concrete. In this investigation, a ring test set up was developed to measure the restrained shrinkage of various repair materials available in the local market. Keeping in view the importance of the local environment, two environment conditions were used; Lab Environment (Temperature 23±2°C) and the open environment of Riyadh. These environmental conditions were used taking into account the local environmental conditions. The samples were outside for almost one year and encountered all weather conditions of Riyadh. It has been observed that some materials although manufactured by highly reputed companies didnt comply fully in restrained shrinkage tests.

Abstract: This paper reports the results of experimental tests on Polyvinyl-Alcohol modified concrete. The mechanical properties, such as uniaxial compression strength and elastic modulus, and the influence of a cross-linking agent are investigated. Uniaxial tests under displacement control both monotonic and cyclic are performed to study the ductility properties of the new composite material and the degradation evolution of the secant stiffness. Moreover, SEM observations and EDX spectroscopy analyses are carried out. In some cases a really significant reduction of the compressive strength is observed due to a pronounced air entrapment in the mixture. Nevertheless, the presence of the polymer introduces a considerable improvement in the ductility of the material, drastically reduces the surface cracking, which is prerequisite for increasing the durability and for reducing stiffness damage.

Abstract: The main difference between normal mortar and polymer modified mortar is the microstructure. Whereas cement is the only binder in normal concrete, the binder of PCM contains cement and polymer. It is known, that these polymer modified cementious matrixes show a higher shrinkage than the non-modified ones. But it is also known, that the PCMs show fewer cracks due to shrinkage. A lot of different investigations have been carried out to find the reason for this con-tradiction. The measurement of shrinkage of PCMs and polymer modified cement stones will be presented in this paper. The prisms were stored under various climate conditions and show a varying shrinkage accordingly. Taking these results into account it becomes obvious that the shrinkage of PCMs depends considerably on the hydration shrinkage, to a lesser extent on the drying shrinkage. Furthermore, a model experiment as to the adhesive bond of cement stones compared to natural stones was introduced.

Abstract: The most common form of rehabilitation for a deteriorated structure is to remove the deteriorated concrete and replace it with a new material, thus increasing the design life of the structure. Good adhesion of a repair material to concrete is of vital importance in the application and performance of concrete repairs. A major factor that influences the durability of the repair is the bond strength between the new material and the substrate. In this investigation, the most common repair materials, produced by international reputed manufactures, available in the local market were selected from cementitious repair mortars and cementitious polymer modified mortars. The performance of these materials were evaluated in terms of compressive strength, tensile strength, bond strength in tension and bond strength in modulus of rupture.