Fiber reinforcement is widely used in construction engineering to improve the mechanical properties of concrete such as compressive and tensile strengths. Concrete is strong in compression but weak in tension and is a brittle material. In the construction industry, strength, durability and cost are among the major factors for selecting the suitable construction materials. During this investigation, the mechanical properties of sisal fibers reinforced concrete (SFRC) were assessed namely, flexural strength, tensile strength ad interfacial bond strength. The said properties were assessed in two types of reinforcement namely, randomly oriented sisal fibers and parallel oriented sisal fibers reinforcement. In both cases the sisal fibers were varied in volume fractions so as to establish the optimum value. The mechanical properties of flexural and tensile strengths were found to increase considerably with increasing fiber volume fractions until an optimum volume fraction is reached, thereafter, the strengths were found to decrease continuously. The prominent increment of 32.4% in flexural strength at fiber volume fraction of 2.0% parallel reinforced fiber concrete composite was observed. There was very small increment on both flexural and tensile strength for randomly oriented chopped sisal fibers reinforced concrete (SFRC). The Interfacial bond strength was found to be 0.12 N/mm2 and was observed to be prominent for chopped sisal fibers reinforced concrete specimens tested for flexural strength. During failure, fiber pull-out was observed and the composite was observed to behave in a ductile manner whereby the fibers were able to carry more load while full fracture had occurred on the specimen. The water absorption capacity of the SFRC was found to increase with increasing sisal fiber volume fraction.

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Looking at current state of most repaired historic buildings in Stone Town of Zanzibar, it is quite clear that the repair attempts made have not been very successful. Modern materials and techniques introduced in the repair works have often proven to be incompatible with the original materials causing accelerated deterioration of buildings fabric. This shows that, there is no comprehensive study undertaken so far on identifying the appropriate materials and restoration techniques. To solve this problem, a study has been made with the main objective of developing the means of restoring historic buildings by using materials existing in Stone Town of Zanzibar. The study was conducted through visual investigation and laboratory testing of materials taken from existing historical buildings and those that are currently being used for repair. Laboratory test conducted includes chemical analysis, grading, compressive strength and water absorption. The results showed some similarities in both materials, however, the combination ratios are not the same resulting into different properties. It has therefore been established that sand of the same grading pattern as the one found in the historic building mortar must be sought and utilized in making repair mortar at a ratio of 1 part lime to 3 parts sand.

Concrete is a building material that is used in great quantities second only to our use of water. The ingredient materials of concrete include cement, fine and coarse aggregates plus a reasonable amount of water, and sometimes additives. The construction of various structures like, residential buildings, commercial buildings, hospitals, schools, bridges, etc, needs good quality concrete. Good modern technologies are needed by the construction industry in order to effectively construct buildings which are durable. A study has been done with the main objective of assessing the concrete technologies existing in rapid growing cities in Sub-Sahara Africa like Dar es Salaam, and the challenges faced in attaining good quality constructions. The study was done through site visits, observations, sampling and testing. From the results, it has been found that traditional concrete technologies are still prevailing, while new technologies are starting to be adopted. Also there is a problem of conformance to the standards. It was therefore recommended that investment in Cement production industries is needed and that regulatory bodies must enforce builders to adhere to the standards in order to yield good quality constructions.

Concrete industry poses a great threat to the environment not only by its consumption of natural resources, but also in its role on the global emission of carbon dioxide in the atmosphere from cement industries which in turn results into global warming. In light of these scenarios, serious interventions have to be incorporated in designs to promote sustainable construction and prevent environmental pollution and degradation. In order to minimize the use of cement, a study has been done by developing simple soil arch elements which can be used to support the topping concrete slab of around 30 mm thick. The technique utilizes the semi-prefab technology and therefore eliminates the use of shuttering for slab panel construction. Through this study, it has been shown that the consumption of cement is reduced to 49.32% while the timber formwork is reduced to 60.00%. The technique is recommended for application in upper floor slab casting as it reduces the cost of construction and is environmentally friendly.