METHODS AND SURFACE MATERIALS REPAIR FOR CONCRETE STRUCTURES – A REVIEW

Concrete is a very critical material that may require maintenance and possible repair periodically, especially in important structure such as bridges. In general, concrete in structures (e.g. reinforced concrete) may be subjected to cracks due to a variety of reasons. These include, design and external environments such as the ingress of harmful ions into the concrete, unexpected extra loads including earthquakes. These cracks can affect not only the appearance of the structure but more importantly the structural performance of concrete and the integrity of the concrete structure. Therefore, when cracks occur a proper repair method should be selected, based on the intended performance of the structure and economy. This should be taken into consideration while choosing the repair method in order to end up with a structure that can serve for the intended service life. The type of crack, its location, dimensions, and many other factors shall be taken into account while selecting the suitable repair method. This paper is a review of the various types of cracks and repair techniques used in each case

MECHANICAL AND DURABILITY PROPERTIES OF GEOPOLYMER CONCRETE – A REVIEW

Owing to the ongoing increase in human population, there is a need for more construction projects including residential buildings and other amenities. Concrete is by far the dominant material used in construction and cement is a main ingredient. Cement manufacture is an energy intensive process and emit large amounts of carbon dioxide into the atmosphere. A reduction in the amount of cement used in construction is greatly beneficial. The use of geopolymer or alkali activated materials can serve this purpose as it attempts to totally replace cement in concrete. Geopolymers are materials that consist mainly of silica and alumina materials and activated using alkali such as sodium silicate and sodium hydroxide. This paper attempts to review recent articles on the production and properties of geopolymers and alkali activated materials. Different hardened, structural, and durability properties are studied. These include; compressive strength, flexural strength, modulus of elasticity, ultrasonic pulse velocity, shrinkage, expansion, creep, weight loss, carbonation, sulfate, and corrosion

AN EXPERIMENTAL STUDY ON THE EFFECT OF SALT AND SUGAR COMBINATION ON MORTAR PROPERTIES

The most important engineering material nowadays, used in construction is concrete. Concrete consists mainly of sand, cement and aggregates. However, weather conditions play a crucial role in affecting concrete characteristics and its serviceability. Weather conditions could be the reason to delay or accelerate the setting time of the concrete. As a result, and in order to deal with weather conditions and its effect on the setting time of concrete, accelerators and retarders must be added to the concrete mix. This research paper focuses on the impact of the use of salt and sugar on the setting time of concrete. Accelerators, like salt, speed up the setting time, while retarders, like sugar, delay it. This paper specifically examines the effects of sugar and salt as separate materials on mortar mixes, with sugar and salt being cost-effective compared to traditional commercial admixtures in delaying setting time It also introduces a novel idea where the combined effects of salt and sugar on mortar is investigated. Different mortar mixes were prepared containing sugar or salt separate or combined. Tests included density, ultrasonic pulse velocity, compressive strength, and flexural strength. The dosages of sugar and salt are 0.15% and 0.3% by weight of cement. Tests are conducted at 7, 28, 56 and 90 days of curing where the water to cement ratio is set constant in all mixes at 0.5