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This research delved into the mechanical and fatigue attributes of hemp fiber–reinforced concrete (HFRC) using both natural crushed aggregates (NCA) and recycled concrete aggregates (RCA) for sustainable rigid pavements. The additional hemp fiber ratios were 0%, 0.5%, 0.75%, and 1.0% by volume of concrete. The accelerated setting times were found due to hemp fibers facilitating rapid cement hydration. The compressive strengths were found to typically decrease with increasing hemp content. Mixes with 0.5% hemp (NCA-0.5H-FRC and RCA-0.5H-FRC) met the local road authority's rigid pavement standards, with enhanced energy absorption and ductility. Flexural strength was optimal at 0.5% hemp, with all mixes meeting the standard 4.2 MPa. The flexural fatigue test indicated that higher hemp content significantly improved the fatigue life of HFRC under repetitive loading. Scanning electron microscopy (SEM) analysis demonstrated hemp fibers' role in enhancing bond strength and interactions with cement matrix, thereby improving the concrete performance. While NCA mixes outperformed RCA ones, hemp fiber's reinforcing effect was consistent across both types of aggregates. The study indicated hemp fiber's potential in applications like pavements, highlighting 0.5% as the optimal hemp content for balancing enhanced mechanical properties while mitigating potential drawbacks. This research paves the way for the broader adoption of hemp fiber–reinforced concretes in sustainable construction endeavors. [ABSTRACT FROM AUTHOR]

The porous structure in the porous asphalt concrete (PAC) mixture is achieved by incorporating a substantial amount of coarse aggregate and polymer-modified asphalt binder (PMA). Bottom ash (BA) was used to modify the properties of the conventional asphalt cement for PAC (BA-AC60/70-PAC) with various types of aggregates in Thailand such as basalt (B), granite (G), and limestone (L). With the lipophilic reaction between BA molecular and asphalt cement, the BA replacement results in the higher optimum asphalt cement, which contributes to the improvement of asphalt film thickness. Therefore, the BA replacement was found to have the potential to improve draindown, Marshall stability, resistance to particle loss, strength index, indirect tensile strength, indirect tensile resilient modulus, indirect tensile fatigue life, permanent deformation, rutting resistance, and skid resistance of PAC, which are comparable to those of PAC containing PMA (PMA-PAC) for all studied types of aggregates. Based on the analysis of cyclic test results, the distress model of both BA-AC60/70-PAC and PMA-PAC was developed and found to be unique and may also be applicable to other PMA-PAC with similar aggregates. The outcome of this research will promote the usage of BA by-products to develop a green and economical PAC. [ABSTRACT FROM AUTHOR]

The utilization of reclaimed asphalt pavement (RAP) and recycled concrete aggregate (RCA) in road infrastructure construction projects contributes significantly to the sustainable reduction of solid wastes being landfilled. This research aims to evaluate the mechanistic performance of asphalt concrete with RAP and RCA modified with natural hemp fiber (HF) reinforcement (HF-RAP-RCA-AC). The effect of influence factors, such as RAP/RCA ratio, HF length, and HF content, on the static and dynamic-mechanistic performance was evaluated. The static performance of HF-RAP-RCA-AC was assessed through the Marshall stability (MS), strength index (SI), and indirect tensile strength (ITS), while the dynamic performance was evaluated through the indirect tensile resilient modulus (IT Mr), indirect tensile fatigue life (ITFL), and rutting resistance tests. The HF-RAP-RCA-AC sample was found to have comparable static properties (MS and SI) to conventional asphalt concrete. The dynamic-mechanistic performance of HF-RAP-RCA-AC was however found to be significantly lower and hence HF-RAP-RCA-AC was found to be suitable for low-traffic roads. The improved ITS due to the addition of RCA and HF was found to influence the IT Mr improvement in the linear relationship. The improved resilient properties contribute to the ITFL and rutting resistance improvement. The optimum mix was found to be at 0.05%HF content, for all HF lengths and RAP/RCA ratios. The potential of HF reinforcement on the material properties was positively impacted by increasing the RCA content. The proposed distress model based on the critical analysis of the cyclic test data of HF-RAP-RCA-AC was developed and was found to have the same logarithm relationship. The outcome of this research will encourage the application of HF-RAP-RCA-AC as a sustainable pavement material for low-volume roads. [ABSTRACT FROM AUTHOR]

The influence of aggregate properties and natural rubber latex (NRL) additive on the performance of natural rubber modified asphalt (NRMA) concrete mixtures was investigated. The NRMA mixtures were prepared using three types of aggregate (granite, limestone, and basalt), asphalt cement AC60/70 and NRL with different rubber to binder (R/B) ratios of 3%, 5%, and 7%. A series of laboratory tests including Marshall stability and flow, indirect tensile strength, indirect tensile fatigue, resilient modulus, wheel tracking test, dynamic creep, and skid resistance tests were conducted to investigate the mechanical properties and mechanistic performance of the NRMA mixtures. Statistical analysis was performed using the NLOGIT software program to evaluate the influence factors including strength, shape, and chemical properties of aggregate and R/B ratio. The R/B ratio of 3% was found to be the optimum value which provided the best mechanical properties and performance. The strength parameters and mineral compound were found to control the Marshall stability. As such, the NRMA mixtures with basalt and granite of high Marshall stability led to the high resilient modulus, rutting resistance, and permanent deformation. Because of the good strength and shape parameters of granite, the NRMA mixture with granite indicated a significant rate of improvement of fatigue life compared with the NRMA mixtures with other aggregates. Limestone's predominant mineral compounds (CaO, MgO, and SiO2) were found to influence the indirect tensile strength and skid resistance of NRMA mixtures. [ABSTRACT FROM AUTHOR]

Porous asphalt concrete (PAC) is an open-graded asphalt concrete with a high air void, which functions as permeable pavement with high surface frictional resistance. PAC typically requires a high amount of coarse aggregate to provide the required porous structure. An expensive high-quality polymer-modified asphalt (PMA) is commonly required to prevent draindown issues and to improve the performance of PAC. Bottom ash (BA), a high-porosity byproduct from coal-fired power plants, is used as a greener product to improve the quality of traditional asphalt cement penetration grade 60/70 (AC 60/70) for producing low-cost PAC in this research. The effect of the BA replacement ratio (0%, 10%, 15%, 20%, and 25% by total weight of fine aggregate) on the draindown, loss of particle, Marshall properties, indirect tensile strength (ITS), indirect tensile resilient modulus (IT Mr), indirect tensile fatigue life (ITFL), permanent deformation (PD), rut depth, and skid resistance of BA-AC60/70-PAC were measured and compared with PMA-PAC. The draindown and particle loss values of BA-AC60/70-PAC were found to decrease with an increase in the BA replacement ratio. The BA replacement improved the Marshall properties, strength index, ITS, IT Mr , ITFL, PD, rut depth, and skid resistance of PAC up to the highest value at the optimum BA replacement ratio of 20%. The improved ITS is associated with the improved IT Mr in a linear relationship for all BA replacement ratios. The change in ITFL was found to be linearly related to IT Mr at a specific stress level. At the same design criteria, the 20% BA replacement ratio yields the reduction of total construction cost of BA-AC60/70-PAC surface course by 33% benchmarked to the conventional PMA-PAC surface course. [ABSTRACT FROM AUTHOR]

The increased temperature at the early state of curing affects the fatigue properties of pavement base materials. The fatigue properties of stabilized pavement bases and subbases govern the performance and service life of pavement structures. This research study utilized natural rubber latex (NRL) to enhance the tensile fatigue properties of cement-stabilized base materials at various temperatures. The effects of influence factors such as cement content (3%, 5%, and 7%), NRL replacement ratio (0%, 10%, 15%, 20%, 25%, and 30%), and temperature (25°C, 40°C, and 60°C) on indirect tensile strength (ITS), indirect tensile resilient modulus (IT Mr), and indirect tensile fatigue life (ITFL) were studied in this research. NRL replacement was found to improve the UCS, ITS, IT Mr , and ITFL of cement (C)-stabilized soil up to the highest values at the optimum NRL replacement ratios, which were 20%, 15%, and 10% for cement contents of 3%, 5%, and 7%, respectively. The cement-NRL (C-NRL)-stabilized samples were found to have superior ITS, IT Mr , and ITFL values compared with C-stabilized samples for the same cement content but had the same rate of reduction in ITS due to the raised temperature. For the NRL replacement ratio on the dry side of optimum, the C-NRL-stabilized samples had lower rate of IT Mr reduction than the C-stabilized samples, although they had the same ITS due to the higher toughness. Therefore, the rate of ITFL reduction of C-NRL-stabilized samples was lower than that of the C-stabilized samples. It was proven in this research that the NRL replacement could reduce the thickness (superior IT Mr) of a cement-NRL-stabilized base course for a given traffic volume and service life, and therefore the construction (material and operation) cost by 17.26% benchmarked to a C-stabilized base course. Finally, the cost-effective design method for C-NRL-stabilized bases course was proposed, which will promote the use of NRL as an alternative green additive instead of synthetic polymer. [ABSTRACT FROM AUTHOR]

Repetitive loads result in increased irrecoverable strain and, consequently, fatigue cracking failure. Fatigue resistance is the prime factor controlling the service life of the concrete pavements. This research study utilized natural rubber latex (NRL) to enhance the mechanical strength and flexural fatigue resistance of normal concrete. The effect of influence factors, such as water to cement (w/c) and dry rubber to cement (r/c) ratios, on the compressive and flexural strengths and flexural fatigue behavior was studied. Normal and NRL concretes were subjected to compressive, flexural, and flexural fatigue tests. At all w/c ratios, a higher r/c ratio resulted in a lower compressive strength but higher flexural strength. The highest flexural strength was found at the optimum r/c ratios of 0.58, 1.16, and 1.73 for w/c=0.3 , 0.4, and 0.5, respectively. Concrete modified by NRL at the r/c ≤ optimum ratio had lower plastic deformation than normal concrete at the same applied flexural stress, hence, higher fatigue life (Nf). As a result, the NRL-concrete pavement at the optimum r/c ratio was found to have a thinner thickness than the normal concrete pavement for the same traffic load conditions at the same service life, which can reduce the operational cost. A cost-effective mix design method of NRL-concrete pavement with the optimized construction (operation and material) cost was also recommended. The outcomes of this research will facilitate the utilization of the NRL additive alternative to synthetic polymer for sustainable NRL-concrete pavement in Thailand and other Southeast Asian and South American countries, which are major global producers of natural rubber. [ABSTRACT FROM AUTHOR]

Unpaved cement-stabilized roads are commonly used for vehicular transportation in the rural areas of developed and developing countries. The high cement content of such roads, however, reduces the tensile fatigue life, especially at locations with a large strain level, resulting in the occurrence of sudden failure due to the initiation of cracks. In order to mitigate this current shortcoming, natural rubber latex (NRL) was studied in this research as an environment-friendly additive for cement stabilization works. The addition of NRL in a liquid state was found to be convenient for fieldwork implementation. The effect of influence factors was studied in this research, which included types of soil, NRL replacement ratio, water content, cement content and compaction energy on unconfined compressive strength (UCS), indirect tensile strength (ITS), and indirect tensile fatigue life (NF). Portland cement (Type I) contents were varied to 3%, 5%, and 7% by weight of dry soil, and NRL replacement ratios were varied to 10%, 15%, 20%, 25%, and 30% by weight of liquid admixture of water and NRL. The UCS, ITS, and NF values were found to increase when increasing the NRL replacement ratio, up to the highest value at the optimum NRL replacement ratio. The maximum ITS, which is directly related to UCS, was found at optimum liquid content (OLC). Although the cement-NRL-stabilized samples exhibited higher total deformation under a particular fatigue tensile stress, the plastic deformation was found to be significantly lower when compared with cement-stabilized samples at similar cement contents. This indicates that NRL replacement improves the capacity to withstand the developed plastic strain against fatigue. Furthermore, the CO2-e emission values for cement-NRL-stabilized soil were found to be lower than that of cement-stabilized soil at a similar ITS. [ABSTRACT FROM AUTHOR]

The comparative performance between steel slag (S) and limestone (L) as aggregates in dense-graded asphalt concretes were investigated in this research. The performance tests for fatigue cracking were undertaken using indirect tensile strength (ITS) tests, indirect tensile fatigue life (ITFL) tests, and indirect tensile resilient modulus (MR) tests. Dynamic creep tests and wheel tracking tests were also performed to assess the rutting behavior of these pavement materials. A heavy metal leaching test was also carried out to ensure that asphalt concrete with the usage of S, as a sustainable aggregate, was safe for the environment. The results indicated that asphalt concretes with S had better Marshall's stability than the asphalt concretes with L, even though they had slightly less ITS values. The ITFL and MR of S asphalt concretes were higher than those of L asphalt concretes, indicating higher fatigue cracking resistance. The MR of S asphalt concretes were found to be higher than the required 3,100 MPa value recommended by AASHTO, while L asphalt concretes did not meet this requirement. In addition, the dynamic creep and wheel tracking test results showed that the S asphalt concretes had superior resistance to permanent deformation as compared to the L asphalt concretes. The usage of medium-sized S aggregate in developing asphalt concrete was evidently more sustainable in terms of engineering and economic perspectives than the usage of large-sized S aggregate. The research results indicated that the sustainable usage of S in asphalt concrete was suitable for the development of heavy traffic volume roads. [ABSTRACT FROM AUTHOR]

Assessment of rainfall-induced shallow slope failures is important for reducing damage to infrastructures as well as for the safety of people living close to hazardous areas. The rainfall intensity-duration thresholds for initiation of slope failure (ID thresholds) based on the historical slope failure data are commonly used to assess slope failure. However, in these slope-stability assessments, the critical influence factors triggering shallow slope failures are often disregarded. Three sets of parametric studies were performed through finite-element modeling to investigate the effects of saturated permeability of soil, slope angle, and antecedent rainfall on instability of a shallow slope. It was found that the hydrological mechanism involving the rainfall-induced shallow slope failure is either (1) the rising of water table mode or (2) the rainfall infiltration mode. The hydrological mode during the failure depends on the magnitude of rainfall intensity compared with the infiltration capacity at the soil saturation state. The rate of reduction of safety factor (FS) increases with an increasing intensity of rainfall, only in a range lower than the infiltration capacity at the soil saturated state. As such, the saturated permeability of the soil, which is equal to the infiltration capacity at the soil saturated state, plays an important role in the shallow slope failure. The saturated permeability was also found to govern a range of applicability of the ID thresholds. If the rainfall intensity is not greater than the infiltration capacity at the soil saturated state, the rainfall duration to failure (Trf ) can be read from the ID thresholds. Slope angle and antecedent rainfall were found to play significant roles in the instability of shallow slopes, because they control the initial stability of slope, which results in the different linear relationship of ID thresholds. In addition, the slope angle might accelerate the rate of rainwater infiltration; hence, it reflects the slope of the ID thresholds. [ABSTRACT FROM AUTHOR]

Lightweight cellular cemented clays have wide range of applications in the infrastructure rehabilitation and in the construction of new facilities. Since the inception of this method, the developments in the plant and machinery as well as associated field techniques have surpassed the basic understanding of strength developments in lightweight cellular cemented clay. In this paper, an attempt is made to identify the dominant parameter, governing the unit weight, strength, and compressibility characteristics of lightweight cellular cemented clay, which helps control input of water, air foam, and cementing agent to attain unit weight and strength development with curing time. From this research, it is discovered that water-void/cement ratio, is the dominant parameter for the above purposes. From the critical analysis of test results, a mix design method to attain the target strength and unit weight is suggested. This method is useful from both engineering and economic perspectives. [ABSTRACT FROM AUTHOR]