Concrete crack is one of the main problems observed in concrete technology due to drying shrinkage. Incorporating fibers in concrete production is one of the mechanisms implemented to mitigate cracks. Nowadays, investigators concentrate on different techniques to replace human-made fiber with existing natural fibers for fiber-reinforced composite material. Utilization of natural fiber has an initiation for the development of eco-friendly materials by reducing damages caused by human-made materials and saving nonrenewable resources. Natural fibers are readily and abundantly available, sustainable, and biodegradable, with low cost and low density, and have superior specific properties. Nevertheless, there are some limitations of natural fiber compared to human-made fiber. Consequently, significant energy was applied to alter natural fiber’s surface and morphology using physical, chemical, and biological treatment techniques to overcome the limitation. The primary intention of surface treatment is to modify the bond between the fiber surface and the polymer matrix. However, based on this literature review, there were no specific treatment techniques to be followed to select the best one from the others as criteria. It should include all parameters to consider starting from the stage from the cradle to the grave, cost of chemicals, transportation, and labors, including energy consumption and effluent energy. Additionally, their environmental effect also investigated in detail to compare each other.
Cinder gravels are pyroclastic materials associated with recent volcanic activity which occur in characteristically straight sided cone shaped hills. The aim of this study was to use this marginal material which is abundantly available in many parts of Ethiopia by modifying their properties through mechanical blending and chemical stabilization. Results of physical and mechanical test conducted on cinder gravel samples prove their marginality to be used as base course materials especially for highly trafficked roads. An experimental investigation were carried by blending cinder gravels with conventional crushed stone bases course material, Crushed Stone Aggregate (CSA), in proportions of cinder/ Crushed Stone Aggregate (CSA) (10/90, 20/80, 30/70, 40/60 and 50/50) and treating with 6. 8 and 10% of cement. According to results of sieve analysis, Aggregate crushing value (ACV), flakiness index and California Bearing Ratio (CBR), 30% of Crushed Stone Aggregate (CSA) can be replaced by cinder gravels for use as Fresh, crushed rock (GB1) material and for cement treated cinder gravels adding 6% and 8% cement make them suitable for use as Stabilized base course (CB2) and (CB1) base course materials respectively, referring to their 14 day compressive strength as determined by Unified compressive strength test(UCS) test.
Unsuitable soil materials along the alignment of road projects have a significant influence on planning, design, construction, and maintenance. Expansive soils are susceptible to considerable volume changes due to seasonal variations and moisture content. Most soils found in Jimma and Ambo Zones composed of plastic clay soil, causing severe damage at the intermittent of pavement sections. This research study conducted laboratory investigation considering combinations of materials blended to stabilize the expansive soil for subgrade construction. An experimental type of study performed which started by collecting specimens. Two clayey soil specimens considered to test the free swell index obtained from a depth of 1.5m to remove the organic impurities. Results indicated the chemical analysis of pumice contained 82.68%, while its physical properties of the test of fineness specific surface and residue on 45 microns showed 3770 cm2/gm and 30%, respectively. As the lime content increased, the CBR strength also increased. But, if the percent content of lime decreased with an increasing pumice content, the CBR value did not show any significant increase. Both the chemical and physical properties satisfied the requirements according to ASTM C-618. Hence, this experiment obtained 7% lime + 3% pumice as an optimum mix ratio to stabilize expansive soils.
Recently, highway and construction industries utilize a substantial quantity of conventional aggregates. The increasing demands for conventional aggregate cause an increase in the cost of construction, reduction of natural resource, and continuing deterioration of the earth's surface. On the other hand, the waste generated from the marble industries during the process of cutting and polishing was increasing day by day all over the world. In Ethiopia, the use of Marble Waste Aggregate materials in road construction as a base course material was not well-known, and it was simply wasted at every place where the marble production was continuing. Therefore, this paper focused on evaluating the possibility of using marble waste aggregate as conventional aggregate in the base course layer of flexible pavements by experimental method. To achieve the objectives of the research, mechanical stabilization and laboratory tests have been carried out at different percentage replacement of Conventional Aggregate by (0%, 20%, 40%, 50%, 60%, 80%, and 100%) of Marble Waste Aggregate weights. Marble wastes materials are collected from Burayyu city, Alisha marble processing industry. The laboratory test results for MWA indicated SG, ACV, AIV, LAA, Flakiness Index , Elongation Index, Plastic Index, Water Absorption, and CBR of 2.74%, 23.63%, 26.21%, 27.03%, 26.48%, 13.29%, Non Plastic, 0.50% and 73.3%, respectively. These test results fulfilled the ERA standard specification for some tests, and it showed marginal quality values to the standard specification for GB2 and GB3 base course materials. CBR and gradation test results shown failure to meet the standard specification. Thus, mechanical stabilization was done to improve the mechanical and physical properties of Marble Waste Aggregate. Blending of 80%MWA with 20% CA results in SG, ACV, AIV, LAA, Flakiness Index, Elongation Index, Plastic Index, Water Absorption, and CBR of 2.83%, 18.2%, 21.52%, 22.58%, 23.79%, 16.29%, Non Plastic, 0.80%,and 82.5% respectively. At this proportion the gradation also observed to fit with the required ERA standard specification of GB2 and GB3 materials. Therefore, the use of marble waste aggregate up to 80% by weight is recommended for road base course layer, when it is found near to the construction site and in places where the materials are abundantly available.
Expansive soil refers to a particular type of soils -almost clayey soils in property -that expand as they absorb water and shrink when they dry out. The process of swelling generates pressures that can cause lifting, or heaving of structures whilst shrinkage process can cause differential settlement on civil structure. A large number of buildings and roads are placed on such type of soil and exposed to the danger from this swelling and shrinkage processes. In order to avoid the previous mentioned risk from the expansive soil, a technique of soil stabilization should be made for this type of soil to enhance some of its properties. In this study, the experimental investigations have been made to study the suitability of natural gravel from jiren quarry site to improve properties of expansive soil. The important parameters to be determine the geo-technical properties such as Specific gravity, Liquid limit, Plastic limit, Plasticity index, dry density and California Bearing (CBR) ratio values. According to ERA 2002 this type of soils is poor for subgrade for road construction. In order to realize the desired objective, a purposive sampling technique which is non -probability method was adopted in order to collect disturbed soil samples at depth of 1.5m and natural gravel from jiren quarry site used for the preparation of different laboratory tests. The laboratory work involved sieve analysis along with consistence test to classify the soil sample. The preliminary investigation of the soil shows that it belongs to A-7-5 class of soil in AASHTO and CH in USCS soil classification system. Soils under this class are generally of poor for subgrade road construction. Atterberg limits, compaction and CBR tests were used to evaluate properties of stabilized soil. The soil was stabilized with natural gravel in stepped concentration of 5%, 10%, 15%, 20% and 25% by dry weight of the soil. Analysis of the results shows the addition of natural gravel improve the geotechnical properties of the expansive black cotton soil. The addition of natural gravel reduces plasticity index, swelling and OMC with an increase in MDD and CBR with all increased natural gravel contents. The addition of 20% and 25% of natural gravel established an increased CBR value by 670% and 958% respectively, indicating the subgrade class falling under S4 and S5 respectively. From this study it was found out that natural gravel stabilized with soil do meet the minimum requirement of ERA pavement manual specification for use as a sub-grade material in road construction.
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