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.

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.

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.

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.

Most of the roads constructed in Ethiopia fail prematurely before serving the design life due to various causes arising from many factors. One of the roads that failed before reaching its design lifetime is the Bako to Nekemte Trunk Road. This road was constructed and opened to traffic in 2013. The design pavement life was estimated at 20 years. However; pavement failures have manifested since 2014 after it was opened for traffic. The main objective of this research was to investigate the cause for the failure of flexible pavement on the Bako to Nekemte road segment. To achieve this objective, the study was followed by the experimental research type and purposive sampling method. Also, field observation and pavement condition survey methods for data collection were used. The asphalt, base course, subgrade, and sub-base layer material sampled from the road segment are the material used for this study. Different pavement failures such as rutting, pothole, alligator cracking, raveling, edge cracking, depression, and corrugation were observed along the road section. For estimations of pavement condition index, the road was divided into five different sections based on distress densities, which were measured during the pavement condition survey. From those five sections, four sections were selected for the determination of the Pavement Condition Index (PCI). Using systematic random sampling 159 sample units were evaluated for Pavement Condition Rating (PCR) and the result shows 1.89% excellent, 8.18% very good, 20.13% good, 31.45% fair, 18.87 % poor, 18.24% very poor, and 1.26% failed. Based on PCI value, samples of pavement layer were taken from failed surface condition (1), poor surface condition (2), and none distressed area (1) for comparison purposes. Different quality tests like Atterberg limit, wash gradation, soil classification, compaction test, California Bearing Ratio (CBR), Los Angeles Abrasion (LAA), Flakiness Index ( FI), Aggregate Crushing Value (ACV), Ten percent fines value (TFV), bitumen content, and gradation of asphalt were carried out. The results of these tests were compared with ERA specifications to identify the probable cause of pavement failure. The study found that the cause for failure of flexible pavement in the case of Bako to Nekemte was: insufficient and absence of side drainage structure, traffic loading, poor gradation of base course and sub-base material, and poor quality of subgrade soil. The study also recommended that the road urgently needed routine maintenance as a treatment option to reduce further deterioration and extend its service time.

Currently, researchers are more focusing on eco-friendly materials, sustainability, and low consumption of energy during the stage of handling, low initial cost, have appropriate mechanical properties and biodegradable and less susceptible to health hazards are the main challenge facing in the present day across the world especially to developing new materials that would improve the industrial supplies for making lightweight materials. Therefore; natural cellulosic fiber one, of effective strategies to substitute artificial fibers for its own benefits when compared and mainly concentrating to reinforce polymer matrices by natural cellulosic fiber due to their decomposable characteristic in nature. This an overview mainly discussed on commonly available natural fiber property such as physical property, chemical composition analysis, surface morphology analysis such as thermal stability analysis (TGA), Fourier Transform Infrared (FTIR) analysis and Scanning Electron Microscopy (SEM) to be adopted in order to characterized natural fiber and impact of treating natural fibers by appropriate chemical on certain properties was discussed by supporting literature. In addition to this the significance of characterization of natural fiber briefly discussed and this an overview will helps other researcher’s source for natural fiber composite studies in future studies.

Understanding the behavior of expansive soil and adopting the appropriate control measures should be great for civil engineers. Extensive research has been going on to find the solutions associated with problems of expansive soils. There have been many methods available to control the expansiveness of these soils. The removal of expansive soils and replacement with suitable material has been widely practiced worldwide. Reasonable material is available within economic distances; however, suitable materials is not readily an available in urban areas for borrowing, which has to be hauled from a long distance. Instead of borrowing suitable soil from a long distance away, after stabilization with cost effective and readily available industrial and agricultural waste materials, it is economical to use locally available plastic soil. Such wastage products are also used to minimize environmental hazards such as CO2 in the atmosphere to minimize the percentage of industrial products used for stabilization, such as cement. Marble dust (MD), an industrial waste product, Rice husk ash (RHA), agricultural waste products, and cement are industrial products in this present study. The general objective of study was to examine the effects of poor subgrade soil stabilization using the mixture of MD, RHA and cement to enhance sub-standard soil engineering properties to be used as subgrade materials. Moisture content, Atterberg limits, grain size analysis, soil classification, free swell index, basic gravity, compaction (maximum dry density, optimum moisture content) and CBR value test have been calculated in this analysis. The design of the analysis followed by the experimental method of study were adopted, which started with sample selection. A disturbed samples was collected from the pit at a depth of 1.5 m to 2m from ground level in order to avoid the inclusion of organic matter by considering the free swell index value and observation was considered. The chemical analysis of MD and RHA was conducted in laboratory and the main oxides are (SiO2+Al2O3+Fe2O3) were 70.13% for RHA and 42.43% for MD. The RHA chemical properties satisfy the requirement, while MD did not meet the requirement of ASTM C 618. The Gomata Teachers’ Condominium (GTC) soil sample laboratory result have 42.72% plastic index (PI), 85% free swell index and its CBR value of 2.265%. The Millennium Secondary school (MSS) soil sample has a 48.79% PI, 87% free swell index and 2.121% CBR value. Therefore this soil samples are highly expansive were checked before any stabilizations process based on  their plasticity index and CBR value based on standard specification requirement , then stabilization was achieved by stabilization by proposed (0,8MD,6MD+2C,4MD+4C,2MD+6C,8C,6MD+2RHA, 4MD+4RHA, 2MD+6RHA,8RHA,6RHA+2C,4RHA+4C,2RHA+6C,2MD+2RHA+4C,4MD+2RHA+2C, 2MD+4RHA+2C) proportion. Then LL, PI, OMC, and CBR decreased as the cement ratio increased, while PL, MDD and CBR value increases instead of MD and RHA increases, however, as MD and RHA increase, the quantity of cement decreases. The laboratory outcome was compared with the requirement of Ethiopian road authority standard, ASTM and AASHTO. Based on this study all mixing stabilizers (MD-cement, RHA-cement, MD-RHA, MD-RHA-cement) and 8% of RHA and cement fulfill the ERA standard specification requirements for its CBR swell value. However, 8% of marble dust alone does not fulfill the Ethiopia road authority requirements for CBR swell. The MD and RHA standalone does not improving some of the engineering properties of soil samples used for subgrade construction. However, they mixed with different percentages of cement can effectively stabilizer for this expansive soil for road sub-grade construction.