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Lateritic soil, a prevalent geological material in tropical regions, often exhibits poor engineering properties, leading to road pavement failures. Meanwhile, the alarming rise in plastic waste poses environmental concerns. This innovative study explores the potential of utilizing waste plastics as a lateritic soil addictive for sustainable road construction. Varying percentages by weight of shredded waste plastic (2%, 4%, 6%, 8%, and 10%) were incorporated into lateritic soil samples, evaluating its effects on soil geotechnical properties. The results revealed that lateritized plastic (shredded plastic waste and lateritic soil) containing 2% shredded plastic waste gave the optimum maximum dry density of 1.985 g/cm3, and the lateritized plastic containing 10% shredded plastic waste gave the highest optimum moisture content of 18%. However, the lower California bearing ratio obtained on the addition of plastic waste showed that the lateritized plastic is relatively weak and can only be used for roads with low traffic. The incorporation of shredded plastic waste into lateritic soil for stabilization is a promising polymer science-based method. By reducing the need for conventional materials and diverting plastic waste from landfills, this approach contributes to a more environmentally friendly infrastructure supporting the achievement of United Nation Sustainable Development Goals. [ABSTRACT FROM AUTHOR]

Although many commercial stabilizers are available for the treatment of poor soils; agricultural, agro-industrial, and environmentally friendly stabilizers are always encouraged. In this study, an attempt has been made to assess the effects of brewery spent grain ash (BSGA) on lime-treated clay for stabilization of an expansive clay to be used as road construction material. Brewery spent grain (BSG) is an agro-industrial solid waste product obtained during the brewing of beer. Through burning in an open cylinder, it is converted to BSGA. The clay was subjected to preliminary tests to classify and identify some required engineering properties of the sample. Initially, samples were thoroughly mixed with lime by weight of clay to determine the optimum amount of lime needed throughout the experiments. Through laboratory execution trials, 10% lime was determined to be the optimal amount. Following, BSGA was added to the treated clay, which was previously treated with 10% lime, at various percentages of 2, 4, 6, 8, and 10% BSGA by weight of clay. At 0% BSGA, the unsoaked and soaked California bearing ratio (CBR) rose from 13.56 and 8.24% to their greatest values of 14.99% and 9.3%, respectively, at 6% BSGA. Unconfined compressive strength (UCS) values rose from 112.63 kN/m2 at 0% BSGA to 130.31 kN/m2 at 6% BSGA, which is the highest value. Therefore, it was discovered that BSGA can be a beneficial addition to lime stabilization in clay soil. [ABSTRACT FROM AUTHOR]

Growing concern over the combustion cost and environment has made road engineers and scientists to explore the possible use of locally available materials for the construction of roads. The present study evaluated the strength and durability characteristics of five sites having locally available silty soils using lime and cement–sand stabilization technique. The test results showed that the cement–sand stabilization technique using 6% cement and 5% local sand resulted in higher strength and durability as compared to lime stabilization. There is also a significant increase in the value of the soaked California bearing ratio (CBR). As unconfined compressive strength (UCS) attained the threshold strength as prescribed by IRC SP 72 2015 for the granular sub-base (GSB) layer, by the use of sand cement stabilization, this technique of stabilization for local silty soils could be used for GSB for low volume road (LVR) construction. As observed from microstructural results which were performed by analysing SEM images, sand cement stabilisation leads to CSH gel and agglomerate formation thereby increasing strength and durability properties. The cost analysis for the replaced stabilized GSB layer showed that using sand–cement stabilization, the estimated cost can be reduced by 56% of the total cost as compared to the conventional method. [ABSTRACT FROM AUTHOR]

In recent years, a sudden upsurge in the quantity of municipal solid waste (MSW) has been observed, and the status quo demands a constructive and economically viable solution. The use of stabilized municipal solid waste (SMSW) in road construction can help in reducing the burden on landfills and waste management authorities. In the existing study, SMSW was accumulated from the Okhla landfill which is situated in New Delhi that is rich in an organic content. This SMSW was then blended with soil (5%, 10%, and 15%) and bottom ash with varying percentages (10%, 20%, 30%) individually and a mix of soil and bottom ash in the ratio of 1:1 to reduce the content of organic matter. The blended sample was then tested to check its compaction value, California bearing ratio (CBR), unconfined compressive strength (UCS), durability, and scanning electron microstructure (SEM). The results indicated that the addition of bottom ash to SMSW decreases the maximum dry unit weight that varies between 1.65 and 1.51 KN/m3 while this value reduces to 1.72 to 1.67 KN/m3 in the case of the bottom ash–soil blend. Also, CBR value reduces to 25.50 to 18.00% in case of bottom ash and 25.89 to 21.92% for bottom ash–soil samples and inverse in the case of SMSW samples blended with soil ranges between 19.95 and 22.59%. The California bearing ratio value of all samples under soaked condition meets the minimum criteria (> 10%) as specified in IRC SP-72 for low-volume roads, but at the same time failed to meet the durability specifications. Thus, it is recommended to use this soil subgrade material in arid regions. [ABSTRACT FROM AUTHOR]

This paper analyzes the stabilizing effect of stone dust, granite dust, marble dust, and calcium lignosulphonate on construction materials and natural soils during road construction. The ultimate aim was to enhance the soil's engineering properties such that the pavement constructed could correctly withstand the load applied. To achieve this, every stabilizer was amalgamated with the soil at various percentages between 5 and 50%. Measurements were made of Atterberg limit tests, moisture content, and specific gravity. The research demonstrated that a diminution in optimal moisture content was seen, with an elevation in maximum dry density and California bearing ratio (CBR). Enhancements in the unconfined compressive strength were also identified. The outcomes determined that the untreated soil's CBR was 2.27% and in the case of soil with 45% additives, the CBR attained was 5.05%. When the soil was mixed with 50% additives, performance of 30.21%, 17.42%, and 12.82% was exhibited for (a) liquid limit, (b) plastic limit, and (c) plasticity index. Moreover, via the addition of presented stabilizers, the soil's mechanical properties were elevated appreciably. [ABSTRACT FROM AUTHOR]

A methodology of in-situ mixing of soil concrete in a quarry has been proposed to guarantee the required characteristics after implementation. The manufactured soil concrete is a mixture of granitic aggregates and lateritic gravels. Geotechnical tests were used to determine the physical and compaction characteristics of the studied materials. The results obtained show that the rocks encountered in the Gamboula area are granites with good to excellent impact resistance (LAA < 45%), good wear resistance (Micro Deval < 15%), and compaction characteristics (Maximum dry density MDD = 2.29 g/cm3, California bearing ratio CBR = 100%) suitable for use as a base course for T1 to T4 volume traffic. The nodular materials developed on these granitic rocks are thick (2.55 m) and present geotechnical characteristics required for use in sub-base (MDD = 2.09 g/cm3, CBR = 56%). The addition of 25% of 0/31.5 granite aggregates improves the characteristics of the lateritic gravels by decreasing the plasticity index, increasing the MDD, and obtaining a CBR value > 60%. A mixing logigram of the aggregate-soil mixture with the mechanical shovel was proposed. This logigram indicates that for these materials, mixing step number 5 gives a better homogeneity of the mixture and the best geotechnical characteristics, especially the CBR. After this step, the mixtures obtained can be implemented without risk of segregation or alteration of the geotechnical characteristics of the mixture. [ABSTRACT FROM AUTHOR]

Red beds (RBs) are widely distributed in all continents of the world. With the rapid development of road and railway construction, the construction of roads and railways in RB areas is increasing. However, when RB is the filler, it will expose three aspects of serious deficiencies in compaction, mechanical bearing capacity, and water stability, which will cause fatal harm to the subgrade. Therefore, RB has to be abandoned and cannot be used as a subgrade filler. In this paper, different microwave irradiation temperatures (DMITs) from room temperature of 25°C to 700°C were used to reveal the enhancing mechanism of RB in three aspects based on the analysis results of microscopic composition and structure. The microscopic composition and structure show that RB can be divided into a low-temperature section (25°C–400°C) and a high-temperature section (500°C–700°C) under the microwave condition. The low-temperature section has some improvement in the engineering performance of RB, but the influence is limited. The engineering performance of RB is improved completely in the high-temperature section. Specifically, the coarse size of RB increases with the rise in microwave temperature, which is beneficial for improving fine size. The compaction property of RB is not largely affected by the water content and can still meet the most stringent subgrade filler requirements, even under saturated conditions or 0. The California bearing ratio (CBR) value can maintain more than 20% under the ultimate working condition, far higher than the code requirements. The increase of internal friction angle and cohesion can enhance the stability of the cut slope, which is conducive to construction in remote mountainous areas. The water resistance of RB is positively correlated with the microwave irradiation temperature, especially at 700°C; RB experiences secondary hardening after encountering water, the mechanical strength increases, and the softening coefficient reaches 107.44%. The research shows that after microwave high-temperature stabilization, the engineering characteristics of the RB are thoroughly strengthened, and it becomes a high-quality subgrade filler to eliminate the three diseases of RB subgrade completely. Compared with the traditional method of adding stabilizers, microwave in situ RB stabilization reduces the site construction's complexity, saves a lot of stabilizer use and transportation costs, and can effectively reduce carbon emissions. This study provides a positive perspective on the in situ application of the RB soft rock subgrade. It could be a starting point for understanding the microwave-based stabilization of soft rock soils subgrade filler in situ. [ABSTRACT FROM AUTHOR]

Sustainable pavement is the need of the hour using the mechanistic and robust pavement design approach, eliminating empiricism in the present IRC SP 72-2015 design guidelines, if any. Giroud and Han (2004) (GH) approach has confirmed existing empiricism in IRC SP 72-2015 design guidelines and permits the use of locally available material, thus saving transportation costs and reducing air pollution. IRC SP 72 – 2015 recommends design thickness only for the unreinforced condition in gravel roads for the maximum rut of 50mm. This paper presents the comparative study of an unreinforced and geotextile-reinforced gravel road design for Indian conditions with the rut as a vital design parameter using the GH method for subgrade classes with 2% to 5% CBR and the maximum traffic count of 100,000. The proposed unique equation provides Allowable Rut Depth (ARD) based aggregate thickness for 10,000 to 100,000 traffic count apart from simplifying the complex procedure of the GH approach for IRC SP 72-2015 data. The unique equation's result reveals an increase of 22.65% in aggregate thickness is attributed to the increase in ARD of 30mm using locally available poor aggregates. This confirms the practical relevance of ARD in pavement design that may help in planning maintenance programs and road rehabilitation strategies. The results obtained from the unique equation match 85 to 100% with GH results. Saving up to 36.5% to 76.9% of costly aggregate is found in the case of geotextile-reinforced gravel roads in Indian conditions. [ABSTRACT FROM AUTHOR]

This study investigates the effects of mucilage from Opuntia ficus-indica cladode (MOFIC), a bio-modifier, on Lime-stabilized Lateritic soil's durability and index features. Specifically, this research assessed the alterations to the Atterberg limits, compaction characteristics, California bearing ratio (CBR), index values and the unconfined compressive strength (UCS) properties of the soil samples and the stabilised samples through laboratory experiments. Lime + MOFIC was added to the soil at 0%, 2%, 4%, 8%, 12% and 16% wt (%) of soil. The result confirms alteration in the index and strength characteristics of the soil upon the addition of MOFIC to the Lime-treated Lateritic soil. The geotechnical characteristics of the soil improved from a subgrade soil to a subbase material upon the addition of 2% of LIME + MOFIC; with the presence of Lime + MOFIC at 2–4%, the bearing capacity of the soil improved from a subgrade material to a subbase material according to the Nigerian General Specification. The highest CBR value in Lime-stabilised was 56%, while the CBR value of Lime + MOFIC-stabilised soil was 70%. This represents a 20% increment in CBR. The presence of polysaccharides in MOFIC enhanced the soil binding attributes of the Lime and hence accelerated the strength properties of the soil. The promotion of green construction and reduction in environmental impacts of using Lime motivates the use of MOFIC in the study. Based on the result of the experimental research, MOFIC is thereby recommended as an eco-friendly alternative for enhancing engineering properties of pavements interlayers. The addition of MOFIC improved the index and strength properties of pavement interlayer material in road construction. [ABSTRACT FROM AUTHOR]

Black cotton soil is highly susceptible to volume change due to moisture fluctuations. This leads to the deformation of structures built on such soil. Therefore, the aim of this study is to improve the soil-bearing capacity and deformation analysis of black cotton soil. The laboratory tests were done according to the American Association State of highway and Transport Official (AASHTO) and the American Society for Testing and Materials (ASTM). These tests were natural moisture content, grain size distribution, X-ray diffraction test, Atterberg limit test, modified compaction, California bearing ratio, and triaxial test. Soil sample was stabilized with a ratio of 0%, 4%, 8%, 12%, and 16% of brick dust and 0%, 1%, 3%, 5%, and 7% of lime, respectively. The result of the laboratory test at the optimum percentage of 12% brick dust and 5% lime shows that the liquid limit improved from 93.2% to 67.5%, plastic limit improved from 48.71%, to 58.2%. The optimum moisture content improved from 26.76 to18.5% and Maximum dry density improved from 1.42 g/cm3 to 1.58 g/cm3. The California bearing ratio improved from 1.29%, to 13.6%. The deformation analysis result shows that at optimum percentage of stabilizing agent, the deformation reduced from 2.087 mm to 0.973 mm. Therefore, brick dust-lime soil stabilization shows the promising improvement of weak subgrade soil. [ABSTRACT FROM AUTHOR]

Sediments are dredged from waterways to maintain maritime activities and prevent floods. Exorbitant amounts of money are budgeted for the removal of dredged material (DM) and its disposal in landfills. We investigated the potential for reuse of DM as a road construction material using so-called bio-enzyme products as stabilizing agents. To improve the mechanical properties of DM, such as compressive strength, compressibility, Atterberg limits and the California bearing ratio (CBR), mixtures of DM were tested with two different amounts of a commercially available bio-enzyme product, which yielded enzymatically stabilized dredged material (ESDM). Unconfined compressive strength (UCS), compaction and Atterberg limits were measured in accordance with ASTM specifications on all samples. Data show that the addition of bio-enzymes resulted in increases in UCS but did not affect the optimum moisture content (OMC), maximum dry unit weight or Atterberg limits of the DM. A comparative field study was carried out to evaluate the CBR of the CH subgrade before and after treatments with the bio-enzyme product and with lime as a traditional stabilizing agent. The results of the field study supported the laboratory findings. Based on these data and results from the literature, models predicting the effect of bio-enzyme treatments on the value of CBR and of UCS were developed statistically. These models also underlined the importance of the clay fraction and PI values for the improvement of the engineering properties of soil using bio-enzyme additives. [ABSTRACT FROM AUTHOR]

Traffic congestion is ubiquitous in major cities around the world. Congestion is associated with a slew of negative effects, including delays and local air pollution. Because of the negative effects of congestion, governments invest billions of dollars into the highway system to try to reduce congestion and accommodate peak-hour automobile travel demand. The COVID-19 pandemic presented a significant disruption to transportation systems globally. One impact was a drastic reduction in travel, leading to free-flowing traffic conditions in many previously-congested cities. As lockdowns eased, traffic volumes returned to near-normal levels. However, the temporal pattern of demand may differ, due to increased remote work or other factors. In this article, we examine the temporal distribution of highway demand in California, using data from over 3,500 traffic sensors. We find that peak-hour automobile travel is spreading in the post-lockdown period. In addition to decreased traffic congestion, this finding also has implications for infrastructure investment. Roadways are generally sized based on peak-hour demand. As the peaks spread, some highway construction project may prove unnecessary. It may be possible to reallocate road space to other uses with fewer tradeoffs in terms of traffic congestion. [ABSTRACT FROM AUTHOR]

The California bearing ratio (CBR) is one of the basic subgrade strength characterization properties in road pavement design for evaluating the bearing capacity of pavement subgrade materials. In this research, a new model based on the Gaussian process regression (GPR) computing technique was trained and developed to predict CBR value of hydrated lime-activated rice husk ash (HARHA) treated soil. An experimental database containing 121 data points have been used. The dataset contains input parameters namely HARHA—a hybrid geometrical binder, liquid limit, plastic limit, plastic index, optimum moisture content, activity and maximum dry density while the output parameter for the model is CBR. The performance of the GPR model is assessed using statistical parameters, including the coefficient of determination (R2), mean absolute error (MAE), root mean square error (RMSE), Relative Root Mean Square Error (RRMSE), and performance indicator (ρ). The obtained results through GPR model yield higher accuracy as compare to recently establish artificial neural network (ANN) and gene expression programming (GEP) models in the literature. The analysis of the R2 together with MAE, RMSE, RRMSE, and ρ values for the CBR demonstrates that the GPR achieved a better prediction performance in training phase with (R2 = 0.9999, MAE = 0.0920, RMSE = 0.13907, RRMSE = 0.0078 and ρ = 0.00391) succeeded by the ANN model with (R2 = 0.9998, MAE = 0.0962, RMSE = 4.98, RRMSE = 0.20, and ρ = 0.100) and GEP model with (R2 = 0.9972, MAE = 0.5, RMSE = 4.94, RRMSE = 0.202, and ρ = 0.101). Furthermore, the sensitivity analysis result shows that HARHA was the key parameter affecting the CBR. [ABSTRACT FROM AUTHOR]

By adjusting the content of geopolymer in geopolymer stabilized phosphogypsum (GSP) as roadbed filler, along with the mixing ratio, this paper mainly explores tendencies in the mechanical properties and water stability of GSP. This research is based on macro-mechanical properties such as unconfined compressive strength, resilience modulus, California bearing ratio and shear strength. It is also based on water stability tests, such as the water soaking test, dry and wet cycle test and expansion test, to explore changes in water stability. As for the durability of GSP, this paper is mainly based on the realization of a long time observation of mechanical properties and water stability. In the existing research, most of the stabilized phosphogypsum (PG) base material or roadbed filler consists of cement, lime, etc. In this paper, a new exploration is carried out on the composition of stabilized PG material, realized without the participation of cement. The 28 d compressive strength of GSP reaches 2.5 MPa, and over time this strength grows, which prevents the phenomenon of strength inversion that may occur in conventional cement-stabilized PG. In addition, a long-term soaking experiment was designed in this study based on the material after the strength was stabilized for up to 90 d. After the strength was steady, the GSP with the best water stability still had a softening coefficient of 80% after experiencing water immersion for 7 d. After determining the feasibility of the mechanical properties and water stability of GSP as roadbed filler, we further explored the strength formation mechanism of GSP by microscopic tests (XRD and SEM). This shows that geopolymer can stabilize PG in two main ways: one is the hydration reaction with PG to generate C-S-H gel and ettringite, and the other is to connect PG not involved in the chemical reaction to form a dense whole through generated hydration products. Geopolymer, stabilizing a high amount of PG, not only provides a new method for the consumption of PG, but also has more stable performance than cement, and has certain advantages in economy. In addition, the advantage of this study is that good performance can be achieved by simply sieving PG and adjusting the geopolymer ratio in practical engineering projects. [ABSTRACT FROM AUTHOR]

This work presents an experimental study on the physico-mechanical and microstructural characteristics of stabilised soils and the effect of wetting and drying cycles on their durability as road subgrade materials. The durability of expansive road subgrade with a high plasticity index treated with different ratios of ground granulated blast furnace slag (GGBS) and brick dust waste (BDW) was investigated. Treated and cured samples of the expansive subgrade were subjected to wetting–drying cycles, California bearing ratio (CBR) tests, and microstructural analysis. The results show a gradual reduction in the California bearing ratio (CBR), mass, and the resilient modulus of samples for all subgrade types as the number of cycles increases. The treated subgrades containing 23.5% GGBS recorded the highest CBR value of 230% under dry conditions while the lowest CBR value of 15% (wetting cycle) was recorded for the subgrade treated with 11.75% GGBS and 11.75% BDW at the end of the wetting–drying cycles, both of which find useful application in road pavement construction as calcium silicate hydrate (CSH) gel was formed in all stabilised subgrade materials. However, the increase in alumina and silica content upon the inclusion of BDW initiated the formation of more cementitious products due to the increased availability of Si and Al species as indicated by EDX analysis. This study concluded that subgrade materials treated with a combination of GGBS and BDW are durable, sustainable and suitable for use in road construction. [ABSTRACT FROM AUTHOR]

California bearing ratio (CBR) is an indispensable parameter in the design of road pavement, repeated carrying out of this test has been chiefly monotonous and time wasting, also the use of cement as stabilizer has also been increasingly expensive, hence, the need for admixing with agrowaste ash such as rice husk ash (RHA). This research is carried out for the prediction of the CBR of lateritic soil admixed with cement and RHA by means of an artificial neural network (ANN). Six parameters are selected as input variables to obtain results that are accurate and precise. The six input variables are cement, RHA, liquid limit, plasticity index, maximum dry density and optimum moisture content, while CBR Unsoaked and CBR Soaked are the output variables. The study consists of a database of 1288 samples obtained from laboratory experiments which were subdivided into 70% for training, 15% for testing, and 15% for validation. The training operation is performed by a multilayer perceptron-back propagation algorithm. The network topology is achieved after fixing a number of hidden neurons. Thereafter, statistical indices are used in evaluating the performance of the ANN model. It is established that this model is appropriate for accurate prediction of CBR results. [ABSTRACT FROM AUTHOR]

The management of waste and its environmental impact remains an issue. Thus, various strategies are being explored to mitigate this problem. For this research case, the ash of plantain peel and coal was harnessed to enhance soil for usage in designing road pavements. The form of the soil, as regards its plasticity and grain assortment, positions it as a sandy lean clay material. Geotechnical parameters of the natural soil were established before being treated with coal ash (CA) and plantain peel ash (PPA), and subjected to tests for the Atterberg limits, California bearing ratio (CBR) and compaction, as well as investigations pertaining to its crystallinity and morphology. These assessments showed that strength parameters of soil increased on adding CA and PPA. However, the inclusion of these admixtures should be conducted until optimal strength is achieved as seen in 9% CA + 6% PPA. The use of soil stabilised with CA and PPA is suitable for general fillings and embankments. These findings revealed that integrating CA and PPA together would have the potential of stabilising soil as pavement layer material while also eliminating the pollution that emerges from the improper disposal of coal and plantain peels from the environment. [ABSTRACT FROM AUTHOR]

This study delves into the potential of using modified sabkha soil, a lowquality material, as a cost-effective solution for road construction in Kuwait, a country grappling with resource limitations. The research evaluates the effects of adding different percentages of bitumen (0%, 4%, 8%, and 10%) to sabkha soil samples, specifically looking at their load-bearing capacity under long-term soaking conditions. The findings indicate that adding up to 8% bitumen enhances the soil's geotechnical properties and its loadbearing capacity. However, any further addition leads to a decline in these properties. Importantly, the soil's load capacity shows significant improvement under soaked conditions. These encouraging laboratory results suggest that utilizing waste sabkha soil could pave the way for effective soil waste management techniques, thereby addressing environmental concerns related to sabkha soil disposal. [ABSTRACT FROM AUTHOR]

Along with the economic loss caused by the non-use of waste worldwide, uncontrolled storage also brings an additional cost. Today, the rapid increase in the population and the rapid depletion of natural resources in nature lead us to research the recycling possibilities of waste materials. In this context, using marble waste in road pavements is one of the best areas of use. This study investigated the suitability of substituting the marble waste obtained from a marble quarry in Bilecik, Turkey, in the road base layer instead of the aggregate, which was used all the time in the base layer in highway construction at different intervals. The physical tests carried out in this context have met the base material limit conditions of the Turkish Highways Technical Specification (THTS). Mixtures obtained in modified Proctor experiments, and optimum water contents (wopt) and maximum dry unit volume weight (rdmax) were determined for each mixture. California bearing ratio (CBR) values remained above the limit value of all mixtures for 0 days and 7 days of curing according to the specifications for THTS. In addition, CBR values were obtained after freezing-thawing at 4, 12, and 20 cycle numbers. According to the freezethaw test results, there was an increase in CBR values in the first 4 cycles and a decrease in the following cycles. Still, all the test results obtained remained above the limit value according to the specifications for THTS. Aggregate unit cost constitutes approximately twice the unit cost of marble waste. Besides, this difference has created an economic equality distance of 18.9 km. Therefore, a marble quarry, a road construction site within the calculated economic equality distance and marble waste material will provide a financial gain for our country. With the evaluation of quarry waste all over the world, we can leave a liveable world with rich raw material resources and a strong economy for future generations. [ABSTRACT FROM AUTHOR]

The increase in population has made it possible for better, more cost-effective vehicular services, which warrants good roadways. The sub-base that serves as a stress-transmitting media and distributes vehicle weight to resist shear and radial deformation is a critical component of the pavement structures. Developing novel techniques that can assess the sub-base soil's geotechnical characteristics and performance is an urgent need. Laterite soil abundantly available in the West Godavari area of India was employed for this research. Roads and highways construction takes a chunk of geotechnical investigation, particularly, California bearing ratio (CBR) of subgrade soils. Therefore, there is a need for intelligent tool to predict or analyze the CBR value without time-consuming and cumbersome laboratory tests. An integrated extreme learning machine-cooperation search optimizer (ELM-CSO) approach is used herein to predict the CBR values. The correlation coefficient is utilized as cost functions of the CSO to identify the optimal activation weights of the ELM. The statistical measures are separately considered, and best solutions are reported in this article. Comparisons are provided with the standard ELM to show the superiorities of the proposed integrated approach to predict the CBR values. Further, the impact of each input variable is studied separately, and reduced models are proposed with limited and inadequate input data without loss of prediction accuracy. When 70% training and 30% testing data are applied, the ELM-CSO outperforms the CSO with Pearson correlation coefficient (R), coefficient of determination (R2), and root mean square error (RMSE) values of 0.98, 0.97, and 0.84, respectively. Therefore, based on the prediction findings, the newly built ELM-CSO can be considered an alternative method for predicting real-time engineering issues, including the lateritic soil properties. [ABSTRACT FROM AUTHOR]

The purpose of this research was to establish a correlation between the DCP Index measured with the Dynamic Cone Penetrometer (DCP) device and the CBR laboratory test results of the Vicho quarry soil, evaluated on the same compacted specimens, which allows the evaluation of the in situ CBR of the pavement subbase courses constructed with material from the Vicho quarry, during the construction process of road projects in the city of Cusco. The bi-logarithmic correlation equation, determined based on the laboratory test results, between the DCP Index and the CBR values for the Vicho quarry soil is Log(CBR)= 2.6838 - 1.21189 Log(DCP) with a reliably coefficient of determination of R²= 95.91%. This coefficient represents that the equation is appropriate for evaluating the in situ CBR value of the subbase course in road pavements of Cusco city constructed with the Vicho quarry soil, allowing also the evaluation of the adequate functional and structural performance of the pavement structural layer according to the provisions of the project design. The test specimens were compacted with certain percentages of the modified Proctor compaction energy, and then the DCP Index values were evaluated on the compacted specimens previously tested with the CBR laboratory tests. As part of the laboratory test results, the physical properties of the material from the Vicho quarry, to construct the subbase course of pavements, are: w = 5.67 %, LL = 23.74%, LP = 18.09%, PI = 5.65%, thus, the soil is type A-1-a(0) according to the AASHTO soil classification system, and the results of the modified Proctor compaction test are: γd(max) = 21.87 KN/m³ and wopt = 7.10 %. [ABSTRACT FROM AUTHOR]

Waste crushed rock (WCR) and spent carbide (SC) composite were used to stabilise lateritic soil (LS) as a road base material. Laboratory investigations were conducted on LS blended with up to 80% WCR by weight of the dry soil to determine the ideal grading and Atterberg limits, which satisfy the Ghana Ministry of Transport (MoT) specification. 40% WCR content was noted as the ideal content. The 40% WCR was then treated with up to 10% SC by weight and subjected to geotechnical tests. The findings revealed notable improvements in the properties of the WCR/LS blend with increasing SC content. The improvement in terms of strength was assessed using California bearing ratio (CBR), which showed ascending values with SC contents. The addition of SC also increased the fines content. Despite the improvement in geotechnical properties of the stabilised LS, comparison with the Ghana MoT standards for road base material indicates that only 10% SC content met the minimum swell specification. However, the grading curves for 0%–7% SC contents substantially fell within the grading envelope. Similarly, all the CBR values passed the minimum specification. Based on the CBR and grading specifications, 40% WCR with 7% SC content is recommended for road base construction. [ABSTRACT FROM AUTHOR]

Peat generally found in thick layers in limited areas such as Urmia Lake, Iran has low shear strength and high compressive deformation. Therefore, an appropriate soil improvement method is required. This paper presents an experimental study of the stabilisation of Urmia Lake peat on the Urmia–Tabriz highway, 7·8 km to the east of Urmia city in Iran. A type of fly ash (artificial pozzolan) and two types of volcanic ashes (natural pozzolans) were used in this investigation. Unconfined compressive strength (UCS) and California bearing ratio (CBR) tests were conducted on stabilised mixtures and untreated soil samples after 3 and 7 d of curing. According to the obtained results, the UCS of peat can be increased by using both the fly ash and the volcanic ash, but the amount of strength increase depends on the organic content, water content, stabiliser content and its particle size. Furthermore, the CBR test showed that the filling property of the stabiliser is as useful as its pozzolanic activity in increasing the bearing capacity of peat in road constructions. [ABSTRACT FROM AUTHOR]

Failure of roads is common in most part of the tropical region of the world. Majority of which can be attributed to poor selection of soil materials for road construction and climate. This study is aimed at investigating the properties of lateritic soil as material for road construction. Following an initial visit to the study area, soil samples were taken and subjected to geotechnical analyses such as particle size analysis, natural moisture content, Atterberg limits, compaction test, California Bearing Ratio (CBR), and direct shear test. All the tests were carried out according to the BS standard 1377 (1990). Results revealed a well graded fairly coarse soil with natural moisture content varying from 6.2-29.4 %. Atterberg limits shows a medium plasticity soil with medium compressibility and the soils classified within the A − 2, A − 6 and A − 7 of the AASHTO classification scheme. In terms of soil strength, the maximum dry density (MDD) and optimum moisture content varies from 1210-1520 kg/m3 and 13-24 %, respectively while California Bearing Ratio (CBR) value varied between 2.27- 45.32 % at 2.5 mm and 3.01 - 44.59 % at 5.0 mm. The shear strength of the samples ranged from 31.28-186.41 kN/m². Based on the results, the study concluded that the clayey nature of the soils was responsible for poor geotechnical properties which were generally below the specifications of the Federal Ministry of Works and Housing (FMWH), hence mostly not suitable in its present condition but could be improved to satisfy the conditions for use as sub-grade and sub-base soil in road construction. [ABSTRACT FROM AUTHOR]

Road pavement thickness and their depth of construction take a chunk of the overall cost of road construction. This has called for a need for reduced road pavement thickness by improving the engineering properties of subgrade such as the California bearing ratio (CBR). The CBR of road subgrade has been a major determining factor for road pavement thickness, and expansive subgrades generally have a low CBR, resulting in major road defects. In this study, road pavement thickness and construction depth optimization were conducted using the CBR values achieved in this study. Additives proportions of 8% lime and 20% cement were used in expansive subgrade to improve their engineering properties, making them suitable for use in road construction. The study investigated the characteristics, mineral structure, Atterberg limit, compaction, CBR, swell and microstructural properties of expansive subgrade. The results show a reduction in road pavement thickness and a construction depth with an increase in CBR value. All CBR values for treated samples were above 2%, making them usable in road construction. A reduction in swell potential up to 0.04% was observed for treated expansive subgrade. The study concluded that pavement thickness and construction depth can be reduced by enhancing subgrade materials and using cement and lime as binders. [ABSTRACT FROM AUTHOR]

This study considered the need for sustainable road construction using recycled materials. Lignocellulosicbiomass fly ash (LcBFA) gotten from Berlinia Grandiflora (Vahl) Hutch. & Dalziel (Ububa tree, in common Nigerian parlance) was used to stabilise a soil sample characterised as A-2-7 soil. The LcBFA was added to the lateritic soil at varying proportions of 0%, 10%, 20%, 30% and 40%. Chemical characterization of the LcBFA was obtained; particle size analysis, moisture content test, atterberg limit test, proctor compaction test, California bearing ratio value (CBR) test, and specific gravity test were conducted on the soil sample. The results showed an increase in plasticity, an increase in maximum dry density, a decrease of optimum moisture content and an increase in CBR value. It was concluded that LcBFA lacks the potential of serving as a pozzolan. [ABSTRACT FROM AUTHOR]

Increasing road construction activities in Nigeria has led to increased demand for lateritic soil (LS), whose properties vary from one location to another, and. The properties of some of this laterite deposits along road alignment can be improved to enable it withstand traffic loads. This paper presents results of the laboratory evaluation of LS stabilised with oil palm fibre ash and cement blends, with a view to determine its suitability as flexible pavement construction material. The mixtures were subjected to British Standard heavy (modified Proctor) compaction energy to determine their strength characteristics. Test results show that the properties of LS improved with oil palm fibre ash and cement treatment. The maximum dry density decreased with corresponding increase in optimum moisture content as the cement content increased from 0% to 6% and the LS content of the mixtures decreased with increased oil palm fibre ash, at a fixed per cent of cement. The peaked California bearing ratio of 190.09% (soaked) recorded for the 80% LS + 14% OPFA + 6% C mix proportion, with 14th day unconfined compressive strength of 785.75 kN/m2, cohesion of 140 kN/m2 and angle of internal friction of 25°, can be used as a base material in road construction. Further work may be encouraged to assess resilient modulus of this material under cyclic load. [ABSTRACT FROM AUTHOR]

This study is aimed at using geotechnical properties and statistical relationship between geotechnical parameters to evaluate the performance of subsoil derived two different rock types for pre- and post-engineering construction planning and design of roads. Twelve soil samples underlain by two rock types (granite gneiss & grey gneiss) were taken at the depth of 1 m for analysis. The geotechnical properties of these soils were tested. The atterberg limit, grain size analysis, California bearing ratio (CBR) and compaction tests of both soils types met the Nigeria specifications of good subgrade material. Soil derived from grey gneiss has better ratings in linear shrinkage, grain size analysis, specific gravity, compac- tion and CBR tests. Twelve parameters of the soil samples were correlated against each other and sixty-six values of correlation coefficient were recorded for each rock type. Soil derived from grey gneiss has more positive pairwise Pearson’s (r) correlation (37) than the soil derived from granite gneiss (34). Granite gneiss derived soil has better ratings in thirty-three (33) out of sixty-six (66) Pearson’s correlation (r) values to thirty-two (32) of grey gneiss with one of the variables correlation having the same value. There exist five strong positive and five strong negative correlation variables that are common to the two rock types’ derived soils. The Pearson’s correlation coefficient (r) values that are within the critical (r) value are negligible. For regression analysis, granite gneiss derived soil has better ratings than the grey gneiss derived soil with both rock types derived soils having these two pairwise correlation variables (GRV-SAND and OMC-MDD) for excellent prediction. [ABSTRACT FROM AUTHOR]

Abundance of natural waste such as seashells and emission of carbon dioxide when stabilizing soil using cement/lime becomes a great concern in protecting the environment and economic impacts in infrastructure engineering projects especially road pavement construction. The low strength and bearing capacity of subgrade pavement layer due to traffic loadings can cause road damage effects. This study assesses the failure strength and bearing capacity effects of single and combined additives on the stabilization of marine subgrade soil. The effectiveness of cockle shell powder (CSP) as a natural waste product and lime powder (LP) as an industry by-product in treated marine soil with the addition of different percentages of stabilizers to predict the strength and bearing capacity of marine stabilized soil was assessed. The effects of CSP and LP contents on the strength stabilized soil samples were examined through the unconfined compressive strength (UCS) test and soaked California bearing ratio (CBR) test. The study demonstrated the feasibility of using a simple ANN to predict the UCS by using additives. A relationship between UCS and bearing capacity ratio is established. Based on the CBR and UCS, the addition of CSP alone in stabilized soil gave low values. However, the combination of both additives CSP and LP resulted in considerably higher UCS and CBR values. The ANN prediction shows good performance and regression values. However, the relationship between UCS and CBR gives a fair coefficient of determination of R2 = 0.706. [ABSTRACT FROM AUTHOR]

This article studies cost‐plus‐time (A+B) procurement contracting with time incentives in the highway construction industry. In the presence of construction uncertainty, the contractor's actual completion time may deviate from the bid completion time, and the A+B contract design is not ex post efficient. Using data from highway procurement contracts in California, we show that an ex post efficient lane rental contract would reduce the social cost by $41.39 million (43.11%) on average. Moreover, the average commuter cost would decrease by $62.06 million (78.96%), suggesting a substantial reduction in the construction externality to commuters from lane rental contracts. [ABSTRACT FROM AUTHOR]

Strength enhancement of waste wood ash (WWA) stabilized lateritic soil, classified as A-7-5(11) and ML (silt), was investigated using sodium sulphate (Na2SO4) as an activator. Basic laboratory geotechnical tests for assessing compacted soil as road construction material were carried out on the samples prepared by admixing the lateritic soil with the predetermined percentages of WWA and Na2SO4 relative to the mass of the soil. The results showed reductions in the percentage of fines as both WWA and Na2SO4 contents increased. Liquid and plastic limits of the lateritic soil increased with the increasing contents of both WWA and Na2SO4, and this led to reduction of the plasticity index and hence improved the workability of the soil. The maximum dry density (MDD) of soil increased with corresponding decrease in optimum moisture content (OMC) as the percentage of Na2SO4 increased. However, MDD increased up to 3% WWA and thereafter decreased. OMC decreased at 3% WWA and then increased with increasing content of WWA. The California bearing ratio increased with increasing contents of WWA but with pronounced increment at 4% Na2SO4. Satisfactory performance of the lateritic soil was observed with up to 9% WWA and 4% Na2SO4 activation, at which the soil could be used as road subgrade material. [ABSTRACT FROM AUTHOR]

During road construction, granular materials for the unbound base course (UBC) and cement-bound base course (CBC) are mostly compacted by vibratory rollers. A widespread laboratory test for determining the optimal moisture content (OMC) and maximum dry density (MDD) of the mixture for installation in UBC and CBC is the Proctor test. Considering that the Proctor test does not produce any vibrations during compaction, this paper compares the Proctor test and the vibrating hammer test. The examination was conducted on UBC and CBC with varying cement content and aggregate types. All mixtures were compacted by both methods with the aim of determining the compaction and strength characteristics. The results indicated the high comparability of the two test methods for mixtures with natural aggregate in terms of MDD, OMC, density and strength characteristics (California bearing ratio (CBR) for UBC and 28-day compressive strength for CBC). For mixtures with higher cement content, the OMC difference depending on the laboratory compaction method used can be significant, so the laboratory compaction method should be chosen carefully, particularly for moisture-susceptible materials. This paper also reveals that by increasing the proportion of rubber in the mixture, the compaction and strength characteristics differ significantly due to the compaction method. Therefore, when using alternative and insufficiently researched materials, the compaction method should also be chosen carefully. [ABSTRACT FROM AUTHOR]

The Caspar Creek Experimental Watersheds are the site of a long‐term paired watershed study in the northern Coast Ranges of California. The watersheds are predominately forested with coast redwood and Douglas‐fir. Old‐growth forest was logged between 1860 and 1904. Two harvesting experiments have been completed since then and a third experiment is currently underway. Caspar Creek data are split into three phases corresponding to three experiments: Phase 1 (1962–1985) reports on a selection harvest (1971–1973) and initial recovery in the South Fork watershed; Phase 2 (1985–2017) includes clearcut harvesting of ~50% of the North Fork watershed (1985–1992) and recovery; and Phase 3 (2017 onward) corresponds to a second selection harvest in the South Fork watershed with a range of subwatershed harvest intensities (2017–2019) and recovery. All three experiments included harvest‐related road‐building and relied primarily on measurements of streamflow and sediment delivery from both treated and reference watersheds. Major findings include modest increases in post‐harvest peak flows and cumulative flow volumes, post‐harvest low flows that initially increased and then decreased 12 to 15 years after harvesting, and the consequences of different yarding techniques and road design on sediment yields. Some of the data for Phase 1 and Phase 2 are available in a USDA Forest Service online archive. The archived data include precipitation, streamflow, suspended sediment concentrations, turbidity, accumulated weir pond sediment volumes, bedload transport rates, water stable isotope data, and geospatial data. Archiving activities are ongoing. Phase 3 data are currently being collected and will be archived after a post‐harvest monitoring period. [ABSTRACT FROM AUTHOR]

Steel slag accumulation is one of the major issues for steel manufacturing companies, because it occupies a large portion of a company's yard. Investigators have suggested various applications for using slag in other industries. There is great potential for using slag as an aggregate in road and railway construction. Evidence demonstrates the compatibility of slag for road base and subbase construction. However, the use of slag as a subballast for railway construction has not been investigated thoroughly. This research studied the application of slag to subballast railway construction. A railway subballast layer requires a high shear strength, which is greater than slag's shear strength. Therefore, the authors modified the slag with 1%, 2%, and 3% gilsonite, or natural binder, and performed Los Angeles abrasion, direct shear, and California bearing ratio tests on the modified slag. The results of all experiments indicated significant improvement in the modified slag's shear strength properties, which makes gilsonite-modified slag a potential replacement for traditional subballast material. [ABSTRACT FROM AUTHOR]

Recycled asphalt pavement (RAP) materials are an alternative to natural aggregate (NA) because they reduce environmental pollution and provide energy and cost savings. In many countries abroad, the usage of RAP materials in road pavement layers are permissible at certain rates. However, the mechanical properties of RAP materials are dependent on; the materials are derived from the in which pavement layer, the service life and construction characteristics of the road it is milled, the properties of the materials used (bitumen and aggregate) in the layer and the characteristics of the milling machine. In this study, two types of RAP materials (RAP1 and RAP2) obtained from the degraded wearing layers of two different roadway using milling machine were mixed with NA in different rates (0%, 15%, 30%, 45%, 60%, 100%). Some of the characteristics of the mixtures were examined with reference to 100% NA mixture values by performing laboratory tests such as bitumen ratio, sieve analysis, modified proctor and California bearing ratio (CBR) on the mixtures obtained. According to the results, maximum rates of RAP1 and RAP2 which can be used in plantmix base type-1 layer as an alternative material to NA is determined according to Turkey Highway Technical Specification. In addition, in the case of using RAP materials, the profit rates of material costs to be reduced by the reduction of the need for NA material are also determined by cost analysis. [ABSTRACT FROM AUTHOR]

Flood-induced moisture damage of flexible pavements is a serious concern for many road authorities. Reports from several studies confirm the significant structural damage that is caused by flooding on pavements. In general, there is a consensus to design and construct roads that are resistant to flooding. Simultaneously, the concept of resilience has gained popularity – frameworks and specifics are being developed to make civil infrastructure components resilient to natural and manmade disasters. This study provides a framework for quantitatively assessing the resilience of flexible pavements to flooding. The different interlinked steps consist of utilising unsaturated flow through the different layers to estimate drainage, interpretation of the results in terms of stiffness of the relevant layers, estimation of the impact of the change in stiffness on the overall structural condition of the pavement and then translating that change to a resilience index. The paper provides an illustrative example of such an estimation of resilience for a pavement. The results demonstrate the need for providing base course materials with appropriate gradation to ensure adequate hydraulic conductivity, and/or thicker surface layer, to avoid a reduction in service quality and loss of resilience for an extended period of time, in flood-prone areas. Abbreviations: CBR: California bearing ratio; D60: diameter corresponding to 60% passing in results of sieve analysis; FE: finite element; FWD: falling weight deflectometer; HMA: hot-mix asphalt; keff: effective hydraulic conductivity; ksat: saturated hydraulic conductivity; MEPDG: mechanistic empirical pavement design guide; MR: resilient modulus; MRopt: optimum resilient modulus; Q (t); Q: quality; RL: loss of resilience; R: Resilience; S Saturation; SNCratiof: post and pre-flood modified structural numbers (SNCs); SWCC: soil–water characteristic curve; wPI: percentage passing No. 200 sieve × plasticity index. [ABSTRACT FROM AUTHOR]

Cost-effective construction techniques, such as reusing waste materials, play important role in dramatically reduce costs. In recent years, sludges have gained considerable attention as a geotechnical material. Increase in the demand of drinking water from purification plants produces a huge amount of water treatment residuals (WTRs). The disposal of such residues can be considered problematic issue. In this study, innovate and economic method to disposal of WTRs was presented. Comprehensive experimental investigations have been done to determine the effect of utilizing WTRs as a substitution layer in collapsing soil through roads construction processes. The investigations extended to the geotechnical and spectroscopic properties. Tests were carried out on the soil sample mixing with 0, 4, 8, 12, and 16% of WTRs. The samples morphology and composition are characterized by scanning electron microscopy (SEM) and the energy dispersive spectroscope analyzer (EDS). The microstructure and organic constituents are analyzed by X-ray diffraction (XRD) and the Fourier transform infrared (FTIR). The geotechnical measurements include particle size distribution (PSD), single odometer test (SOT), modified proctor test, and the California bearing ratio (CBR). The microstructure analysis confirms that WTRs acted as a pore filler to decrease in porosity and create a denser and solidified structure which reduces the suction and maximum collapse potential. Mineralogical analyses implied that the soil with WTRs turns into a rich medium with metal cations and organic matters that react with minerals to form binding materials. From the geotechnical point of view, WTRs can be safely deposed by mixing with collapsing soil as a subgrade of road construction up to a value of 10% without any impact or reduction on CBR values. The reduction in the required amount of subgrade required by 10% effectively decreases the cost of road construction. Moreover, the results illustrate the remarkable improvement in the collapse potential of the soil, which is reduced by about 24.7% by mixing it with 10% WTRs. [ABSTRACT FROM AUTHOR]

Steel manufacturing factories usually dump byproduct recycled steel randomly in open areas, creating environmental hazards. Using such materials in highway construction could be a solution to the environmental hazards generated from their disposal. A combined method of physical and chemical stabilization was used in this study to investigate the value of using mill scale (MS) and cementitious materials in improving the strength and deformation properties of subgrade soil. The results showed that MS additives effectively reduced plasticity and increased maximum dry unit weight, unconfined compression strength (UCS), and California bearing ratio (CBR). Subgrade soil with 20% MS was treated with cement and lime to obtain a strength value of 1.7 MPa (after 7 days of curing) for subbase application. A repeated load triaxial (RLT) device was used to perform resilient modulus (MR) and permanent deformation tests in order to evaluate the response of laboratory-molded stabilized specimens under cyclic loading in accordance with a standard testing procedure. Study findings are explained through a microstructural analysis that used scanning electron microscopy (SEM) supplied with energy-dispersive X-ray spectroscopy (SEM/EDX). The test results showed that, in addition to solving the MS disposal problem, the use of MS as an additive had a favorable influence on the geotechnical properties of the soil. [ABSTRACT FROM AUTHOR]

One of the challenges of road construction is encountering soils with lack of required strength and durability. Nowadays, various stabilization techniques are applicable for improving the engineering properties of soils. In the present study, dune sand, as subgrade of pavements, was treated using various contents of fibrillating network (FN) fiber and cement. Dune sand has low bearing capacity that makes it unsuitable for construction activities such as pavement applications. The common solution is improving the strength properties of dune sand so that it can be used for civil engineering projects. Stability of subgrade is very important since the layer provides the stability for the whole pavement structure and the upper layers, namely subbase, base, and asphalt layers. In this regard, compression strength and California bearing ratio (CBR) tests were carried out. Freezing-thawing cycle is one of the most important factors affecting the mechanical properties of soils. Several researchers reported that freezing-thawing cycle could change the physical and mechanical behaviours of soils. The influence of freezing and thawing (up to 18 cycles) on the properties of samples was also studied. Based on the results, the inclusion of FNfiber to the sand led to increasing the ductility and compressive strength. Also, the addition of cement reduced the ductility, and increased the compressive strength. By increasing the freezingthawing cycles, the soil strength significantly decreased. Results showed that the stabilized sand soil as subgrade layer led to reducing the compressive strain under the applied wheel load, and therefore reduced the possibility of rutting failure of subgrade. [ABSTRACT FROM AUTHOR]

Performing Constructability Review Processes (CRPs) during the highway design development has been found to save transportation agencies twice their input costs. However, existing literature has identified three areas of CRP improvement: reduction of required agency resources, incorporation of Road User Cost (RUC) scheduling constraints, and integration of assessment visualizations. The authors propose to fill this gap by integrating the Construction Analysis for Pavement Rehabilitation Strategies (CA4PRS) v.3 software into the CRP. This module provides agencies with road widening project schedule capabilities, which enhances CRPs by providing accurate RUC-constrained critical path schedules using minimal resources. The module was developed through interviews with subject matter experts from six public and two private California transportation organizations. Said experts also tested the CA4PRS v.3 alpha and beta pre-release versions using data collected from eight Caltrans road widening projects. The potential value-adding of integrating the CA4PRS v.3 software with existing CRPs has been tested through its application on the California State Road 91 (SR-91) Corridor Improvement Program (CIP), resulting in 24-months of construction acceleration. The findings and presentation of the schedule model within this paper provide practitioners an accurate and resource-efficient tool to estimate the schedule impacts of road widening constructability options. [ABSTRACT FROM AUTHOR]

Natural laterite soil, classified as A-5 (4) based on American Association of State Highway and Transportation Officials (AASHTO) soil classification system and ML-CL according to Unified Soil Classification System (USCS), was admixed with ordinary Portland cement and synthetic hair fibers (SHF) were evaluated as road construction material. Soil specimens were made by mixing lateritic soil with up to 4% cement in 1 % step concentration and up to 12% SHF in 2 % step concentration of by dry weight of the soil and subjected to British Standard Light (BSL) or Standard Proctor method of compaction, unconfined compressive strength (UCS), and California bearing ratio (CBR) tests. Results indicated a decrease in the values of optimum moisture content (OMC), while no general trend was established for maximum dry density (MDD). The values of UCS and CBR increased as the content of both cement and SHF increased. Analysis of variance (ANOVA) of the results shows some level of significance on some geotechnical properties considered. Regression analysis on the results shows that MDD, OMC, cement, and SHF significantly influenced the UCS and CBR values of the stabilized soil with correlation coefficient values (R2) of 82.9 and 83.3%, respectively. Based on the results, an optimal blend of 3% cement 9% SHF significantly improved the soil properties and is recommended for improving the geotechnical properties of lateritic soil treated with cement/ synthetic hair fiber as road construction material. [ABSTRACT FROM AUTHOR]

Construction and demolition recycling is regarded as an essential subject in the EU, as the target established by its policies to 2020 ratio is far from being achieved. The use of materials recycled from such waste has been widely deemed a contribution to the sustainability of the construction sector. Gypsum is one the limiting components of recycled aggregates used as a base layer in road construction. The aim of this research was to analyse the effect on mechanical properties, leaching behaviour and dimensional changes at long term in recycled aggregates with different gypsum contents. Load bearing capacity was conducted by California bearing ratio on prepared samples. Moreover, the compressive strength was conducted on samples prepared with a 3% cement addition. Both tests were studied long term. Dimensional changes were studied through swelling in California bearing ratio test mould under the modified Proctor conditions for 1 year and using an oedometer device for 5 months. Furthermore, environmental risk assessment was performed, classifying the material with gypsum addition as non-hazardous, given that sulphate anion was above the inert limit. Good mechanical behaviour in the long term and no significant dimensional changes were found regardless of gypsum content. [ABSTRACT FROM AUTHOR]

For highway construction or any superstructure, on dune sand, designers and construction teams must ensure that the foundation soil is stable enough to provide support for the applied loads. Sand dunes are stretched across Libyan deserts that make road construction a challenge because of the poor soil base. Replacement of such a weak soil is very expensive and not economically feasible, and, in many cases, there is no alternative soil nearby. This study used two different mix designs aimed at stabilizing the existing base course using a mix of dune sand and manufactured sand with a small percentage of Portland cement. Compaction, unconfined compressive strength and California bearing ratio tests were conducted on the treated sample with a varying cement proportion of 0%, 3%, 5% and 7% by weight. The first tests were done with a mix of 50% dune sand and 50% crushed sand that is shown to have excellent results. For a more economic design, this study also included testing of another mix design with 70% dune sand and 30% crushed sand; laboratory results show this 70%/30% mixture was appropriate to use as a base-treated material for road construction material. This mix resulted in overall superior performance. Its use will reduce the cost of road construction by saving materials and time, and it will also have lower environmental impacts in desert areas. This study has shown that the stabilization of weak material (desert sand) by using cement improves the strength characteristics of the treated soil. [ABSTRACT FROM AUTHOR]

Lateritic soil treated with up to 12% periwinkle shell ash (PSA) by dry weight of soil was evaluated for use as road pavement material. Three compaction energies were used: British Standard light (BSL), West African Standard (WAS) and British Standard Heavy (BSH). The maximum dry density increased with decrease in optimum moisture content for all compaction efforts. Peak unconfined compression strength (UCS) and California bearing ratio (CBR) were obtained at a threshold of 6% PSA content for all compaction efforts. Durability assessment showed that the resistance to loss in strength increased with increase in PSA content but did not show any consistent trend with increasing compaction effort. Peak resistance to loss in strength of 24.3% was obtained at 8% PSA treatment for British standard heavy compaction effort. Microanalysis studies revealed that improvement in soil properties was due to the formation of cementitious products of calcium silicate hydrate and calcium aluminate hydrate at inter particle contact of soil grains. The study showed that PSA can be used to improve lateritic sub-base of lightly trafficked roads, but would be more effective as admixture in either lime or cement stabilization of lateritic soil. [ABSTRACT FROM AUTHOR]

This paper presents the result of a laboratory study carried out on an expansive tropical black clay (also known as black cotton soil because the cotton plant thrives well on it) treated with locust bean waste ash (LBWA) using cement kiln dust (CKD) as an activator. Compaction was carried out using British Standard light energy. Results of index properties, compaction characteristics (maximum dry density, MDD and optimum moisture content, OMC) and strength characteristics (California bearing ratio, CBR and unconfined compressive strength, UCS) of black cotton soil treated with a maximum 8% CKD/10% LBWA blend by dry weight of soil is presented. Test results show that the strength properties of the treated soil generally increased with higher additive contents and peak values were recorded at 6% CKD/6% LBWA content. Based on strength criterion, an optimal 6% CKD/6% LBWA is recommended for treatment of black cotton soil for use as sub base material in road construction. [ABSTRACT FROM AUTHOR]

The article discusses the state of the highway systems in California, claiming that the state's roads are well-placed but are becoming aged and outdated. The article states that the state cannot afford all the repairs that are desired and that the transportation networks must be handled more efficiently and effectively in order to compensate for the lack of funding. The article discusses how state legislature has caused the funding shortage and also worked to solve it. The article discusses the role of transportation in economic development and also how both the state and the U.S. governments can work to raise money for infrastructure repairs.