Compaction Energy Research Articles

Vibrorheology of fresh cement-based materials with different compaction energy

Vibration is commonly applied to the placement of cement-based materials to improve their fluidity and compactness. Appropriate compaction could ensure the designed performance by preventing the formation of voids and cavities within a structure. In recent years, the application of vibration has been extended to the rheology control of 3D printable concrete as well. While previous studies have reported on the effective radius of compaction and rheological changes in cement-based materials induced by poker-type vibrators, there has been limited in-depth research on the rheological behavior beyond this effective radius, particularly in relation to the compaction energy. This study investigates the rheological behavior of a cement-based material under controlled vibration energy across a wide range of shear rates. A novel device is proposed for the precise control of compaction energy, in terms of the energy transfer rate per unit volume (power density) of vibration, and the vibrorheology under various power densities is measured. Experimental results reveal that viscosity at a low shear rate decreases proportionally to power density, while vibration has negligible effects on viscosity at a high shear rate. Furthermore, a correlation between power density and normalized yield stress is established, along with the effects of varying water-to-cement ratios. The study also discusses the influence of the vibration frequency on the effective radius of the poker-type vibrator.

Quantification and Optimization of Compaction Energy Used in Earth Construction: Case of Static and Dynamic Compaction

Earth construction is a sustainable and environmentally friendly approach to building. In addition to their good thermal performance, earth materials are abundant, inexpensive, and readily available, reducing the need for resource-intensive materials like concrete and steel. Regarding the construction process of earth structures, which is based on compaction, there is often a difference between the laboratory compaction process and the onsite one. The energy consumed onsite to produce earth structures is still approximative and uncontrolled, which affects considerably the mechanical performances of earth walls. Then, the investigation of the optimal compaction energy is necessary. To optimize the on-site compaction energy used in rammed earth (RE), an experimental study is carried out to compare the dynamic compaction usually applied to produce RE walls to the static compaction using a mechanical press. By considering increasing dynamic and static energies, the physical and mechanical properties are analyzed for each case. The obtained results show that RE walls can be replaced by prefabricated pressed earth blocks where the compaction energy is reduced by 60% and the compressive strength is enhanced by 70% using static compaction, thus achieving 4 MPa without stabilization. This solution allows to reduce the execution time and to control the quality of earth buildings.

Soft computing to predict the porosity and permeability of pervious concrete based on mix design and ultrasonic pulse velocity

ABSTRACT The present study explores the potential of machine learning to predict the porosity and permeability of pervious concrete constructed on mix parameters (compaction energy, aggregate-to-cement ratio and aggregate size) and ultrasonic velocity. The prediction models use non-destructive measurements and mixed design variables, which can help the construction sector apply the models without any theoretical expertise. The study uses 225 data samples from an experimental study. This study used six machine learning algorithms, namely, linear regression, artificial neural networks, boosted decision tree regression, random forest regression, K-nearest neighbour and support vector regression, to determine the best predictive model. The results show that the ANN model is the best technique for predicting the porosity of pervious concrete (R2 = 0.9502 for training datasets and R2 = 0.8958 for testing datasets) and boosted decision tress for permeability of pervious concrete (R2 = 0.9323 for training datasets and R2 = 0.7574 for testing datasets). The sensitivity analysis of the random forest regression model reveals that ultrasonic pulse velocity is the most influential parameter for the prediction of porosity and permeability of pervious concrete. The proposed models provide a more accurate method for estimating the porosity and permeability of pervious concrete.

The Friction-Lubrication Effect and Compaction Characteristics of an SMA Asphalt Mixture under Variable Temperature Conditions.

The aim of this article is to explore the dynamic compaction characteristics of stone mastic asphalt (SMA) and the friction-lubrication effect of internal particles during the superpave gyratory compaction (SGC) process. Firstly, a calculated method for the compaction degree of an asphalt mixture in the gyratory compaction process was defined based on the multiphase granular volume method. Secondly, the gyratory compaction curves of asphalt mixtures were taken based on this calculation method of compaction degree. The dynamic change law of each compaction index (compaction, percentage of air voids, compaction energy index, etc.) during the compaction process was analysed. Finally, the effects of different initial compaction temperatures and different asphalt content on the friction-lubrication effect and compaction characteristics of asphalt mixtures were studied. Research shows that it is reasonable to define the compaction degree by the ratio of the apparent density of the asphalt mixture to the maximum theoretical density of the asphalt mixture during gyratory compaction. The dynamic prediction equations of the compaction degree K and the compaction energy index CEI with the amount of compaction were established, and could effectively predict the compaction degree, percentage of air voids and compaction energy index CEI. The compaction process of the asphalt mixture needed to go through three phases, including periods of rapid growth, slow growth, and stabilisation, and the compaction degree increased by about 10%, 5%, and 1%, in that order, finally tending towards a stable value. The effect of the initial compaction temperature on the forming compaction degree of the asphalt mixture is significant; therefore, it should be controlled strictly in the compaction construction of asphalt mixtures. When the initial compaction temperature of SMA-13 is about 170 °C, the compaction effect is optimal, and the effect of the increase in the amount of compaction at a later stage on the increase in the compaction degree of the asphalt mixture is very low. With the optimal asphalt content, the friction-lubrication effect between the asphalt and aggregate particles is optimal, because it can effectively form an asphalt film, reducing the frictional resistance of the particles moving each other during the compaction process, and the voids will be embedded and filled with each other, finally producing the best compaction result.

Crushing characteristics and particle size distribution of steelmaking slag according to repetitive compaction loads

Steelmaking slag, which is used as a construction material, can be crushed during compaction or repetitive loading in construction work. This crushing has a considerable influence on its physical and mechanical properties. Therefore, this study aims to evaluate/estimate the crushing properties and particle size distribution of steelmaking slag under various compaction loads. Accordingly, compaction tests were conducted by subjecting steelmaking slag with 10 different particle sizes to an increasing number of compaction cycles (1–15 times) to simulate repetitive compaction loading. The compaction test results were analyzed by considering the particle size distribution, particle size distribution curve, breakage factors, and fractal dimension. The results revealed that these factors could be influenced by changing the voids in steelmaking slag by altering the repetitive compaction load and particle size. An equation for predicting the particle size distribution from the compaction energy and particle size based on the sequence limit with the rational and the recurrence formulas was proposed. The proposed equation demonstrated excellent accuracy, and it can be utilized in efficiently predicting the particle size distribution curve.

Effect of Initial Conditions on the Pore Structure and Bimodal Soil–Water Characteristic Curve of Compacted Granite Residual Soil

Granite residual soil typically forms complex pore structures and exhibits high water sensitivity due to physical and chemical weathering processes. Changes in initial compaction conditions significantly affect the mechanical and hydraulic properties of in situ granite residual soil subgrades, with these variations fundamentally related to changes in pore structure and soil–water characteristics. This study investigates the pore structure and bimodal soil–water characteristic curve (SWCC) of a compacted granite residual soil through laboratory tests and mercury intrusion porosimetry tests. Nine initial conditions were selected based on potential in situ compaction conditions of subgrades, and their effects on the pore size distribution (PSD) and SWCC were thoroughly analyzed. The results show strong correlations between bimodal pore structure and SWCC. The size and volume of inter-aggregate pores exhibit noticeable changes with initial conditions, affecting SWCC within the low and middle suction range. Conversely, the intra-aggregate pores, which constitute over 60% of the pore structures, remain nearly intact across different initial conditions, resulting in similar SWCCs within the high suction range. As the compaction energy increases, the inter-aggregate pores are compressed and lead to a higher water retention capacity. In addition, as the compaction water content increases, the SWCC becomes less sensitive to compaction energy after the aggregates in the pore structure are fully saturated. Additionally, a three-dimensional bimodal SWCC equation is proposed and validated using test data with an R2 value above 0.98. These findings offer valuable insights for the design and quality control of granite residual soil subgrades.

Experimental investigations on the compaction energy for a robotic rammed earth process

Rammed earth is a construction material with a long history of traditional manufacturing. Due to its low environmental impact, positive impact on indoor climate and completely recyclable nature, its demand is also increasing in modern construction industry. However, as a consequence of the predominantly manual manufacturing processes, the production of rammed earth components is both inefficient and costly. Through the implementation of automated and robot-aided fabrication processes in the field of rammed earth construction, the opportunity to advance the digitalization of the field can raise to a new level. In this paper, general studies on the interrelation of process and material parameters and their influence on the compaction results were conducted as a basis for the development of a prototypic robotic manufacturing process. The results show that reducing the layer height can significantly decrease the impact energy. Additionally, it was shown that there is a minimum number of strokes and a minimum ramming frequency required for sufficient compaction. Furthermore, a possible workflow for a specific control of the required dry density through variation of the compaction energy with regard to the present moisture content was identified.

Laboratory Evaluation of the Hydraulic Conductivity as a Function of Changes in the Particle Size of a Cubitermes Sp Termite Mound Soil Treated with Lime

This work characterizes the geotechnical properties and microstructure that served as a fundamental and more practical basis for describing the hydraulic conductivity of the lime-treated cubitermes sp termite mound soil. The results show that changes in particle size lead to a decrease in dry density and linear swelling. Permeability is strongly correlated with particle size distribution and compaction. Permeability increases up to the lime fixation point obtained at 6% of the lime content. Compaction for micropore reduction in treated soil is higher than in raw soil. The treated soil has a denser internal structure with agglomerations of dispersed clay particles. The increase in compaction energy reduces macropores and permeability, and the soil microstructure becomes homogeneous. Natural soil is highly impermeable, and soil-lime mixes are among the least draining materials. Higher values of hydraulic conductivity were obtained as a function of time. Soil and mixtures can be used in civil engineering works (earthworks). Correlations between hydraulic conductivity and particle size fractions are polylinear fits with R2 (0.962-0.993) and the Slogistic1 model with χ²(2.06E-15) for the mean silt fraction. This study is decisive for predicting hydraulic conductivity from the geotechnical properties of the soil, by solving the mathematical expressions of the models used.

Cement-Stabilized Granular Volcanic Ash Materials for Construction of Low-Traffic Roads in Yemen

Granular volcanic ash (GVA) is a volcanic activity material with low density, high porosity, and other undesirable properties that must be improved prior to use in any construction. This material can be considered an alternative for use in road building, given its availability in many locations and in large quantities in Yemen. This article aims to investigate the potential use of GVA for the construction of roads in Yemen when treated with cement stabilizer. Two types of GVA materials with different colors were selected and referred to as red and black GVA materials. Tests performed included the unconfined compressive strength (UCS), compaction, indirect tensile strength (ITS), wetting–drying durability test, and ultrasonic pulse velocity (UPV) test for samples curried for 7 and 28 days. For each GVA–cement mixture, the cement content varied as 2%, 5%, and 8% by dry weight of GVA. Test results revealed that the compaction energy applied during sample preparation led to a significant reduction in the finesse modulus for red and black coarse GVA materials, with reductions of 10% and 23%, respectively. In addition, the cement content and curing period had a significant effect on UCS, ITS, and UPV for cement-treated GVA. The applicable quantity of cement required stabilizing GVA and achieving the base course specification for strength and durability criteria in flexible pavement with low traffic is 8% cement.

At-rest lateral earth pressure of compacted expansive soils: Experimental investigations and prediction approach

This paper presents experimental studies on a compacted expansive soil, from Nanyang, China for investigating the at-rest lateral earth pressure σL of expansive soils. The key studies include (i) relationships between the σL and the vertical stress σV during soaking and consolidation, (ii) the influences of initial dry density ρd0 and moisture content w0 on the vertical and lateral swelling pressures at no swelling strain (i.e. σV0 and σL0), and (iii) evolution of the σL during five long-term wetting-drying cycles. Experimental results demonstrated that the post-soaking σL-σV relationships are piecewise linear and their slopes in the passive state (σL > σV) and active state (σL < σV) are similar to that of the consolidation σL-σV relationships in the normal- and over-consolidated states, respectively. The soaking σL-σV relationships converge to the consolidation σL-σV relationships at a threshold σV where the interparticle swelling is restrained. The σL0 and σV0 increase monotonically with ρd0; however, they show increasing-then-decreasing trends with the w0. The extent of compaction-induced swelling anisotropy, which is evaluated by σL0/σV0, reduces with an increase in the compaction energy and molding water content. The σL reduces over moisture cycles and the stress relaxation in the σL during soaking is observed. An approach was developed to predict the at-rest soaking σL-σV relationships, which requires conventional consolidation and shear strength properties and one measurement of the σL-σV relationships during soaking. The proposed approach was validated using the results of three different expansive soils available in the literature.

Influência da energia de compactação nas propriedades do concreto permeável e na distribuição vertical da porosidade

Abstract Compaction is a fundamental step in pervious concrete production and affects its mechanical and hydraulic properties. In this study, two pervious concrete mixtures were compacted with three different energies, distributed in two and three layers. The effects on porosity, mechanical strength and hydraulic conductivity were evaluated. The increase in compaction energy resulted in a proportional reduction in porosity. Increases in compressive strength from 17 to 36% were observed. However, permeability reduced proportionally, with decreases of 0.2 to 0.4 cm/s. The three-layer compaction resulted in a more homogeneous vertical distribution of porosity when compared to the two-layer compaction. Although the aggregate/cement ratio was the most influential parameter, the compaction energy should also be considered in the pervious concrete mixture design. While increasing the compaction energy enhances the mechanical strength of pervious concrete, excessive compaction may cause the fracture of the coarse aggregate, reducing its mechanical and hydraulic performance. Thus, for each mixture an optimum compaction energy can be defined to maximize the performance of pervious concrete.

On the behavior of compacted filtered iron ore tailings submitted to high pressures

Mine tailings have been disposed of in a slurry form in tailings dams for many years. However, recent disasters involving conventional disposal in dams reinforced the need for alternative structures to store these materials safely. One alternative is dry stacking of tailings. In these structures, tailings are filtered to low moisture content and then compacted in layers. Due to material compaction, dry stacks tend to be stable and are usually built with elevated heights to use the available area better. So, it becomes essential to understand the mechanical behavior of tailings subjected to high pressures, especially concerning the possibility of grain breakage. In this context, the present research focuses on studying the geotechnical behavior of iron ore tailings from different stages of ore beneficiation plants in Quadrilátero Ferrífero, Brazil, when subjected to high pressures both in compression and in shear paths. The results demonstrate that the inclusion of fines can change the geotechnical performance of the dry stack tailings considering the same compaction energy (greater strength, stiffness, and lower permeability) both in drained and undrained conditions. No breakage could be identified for the stress level studied (6 MPa).

Pull-Out Tests for GFRP/BFRP/Steel Bars Used as Nailing for Coal-Bearing Soil Slopes in Humid Regions

Abstract Coal-bearing soil slopes are associated with a high risk of landslides when subjected to high soil water content. Steel bars have been used as soil nailing for slope stabilization; however, corrosion may occur in an aggressive environment. Glass fiber reinforced polymer (GFRP) and basalt fiber reinforced polymer (BFRP) bars have higher resistance to corrosion and could be alternatives to steel bars, but their elastic modulus and bonding strength with cement concrete are inferior to steel bars, which may result in lower reinforcement effects against landslides and hence require further investigation. In this study, the mechanical properties of different types of bars were investigated using tensile tests. The mineral composition of the soil samples was analyzed. Subsequently, pull-out tests were conducted on three types of bars (steel, GFRP, and BFRP) embedded in grouts in the soil. Up to 38 test scenarios were investigated, and the results were statistically analyzed using an analysis of variance test. The effects of several factors were studied, including the bar type, water content, soil compaction degree, and soil surcharge. The results showed that the bar type had an insignificant effect on the maximum pull-out loads, indicating the feasibility of using GFRP and BFRP bars as alternatives to steel bars for soil nailing in coal-bearing soil slopes. The reinforcement effect can be weakened by rainfall or drought events and enhanced by higher compaction energy and surcharge loads.

Effect of Compaction Energy on Selected Physical and Hydraulic Properties of Soils Amended With Different Sources of Organic Matter

Soil compaction has been recognized as a severe problem in mechanized agriculture and influences soil properties and processes. A study evaluated the effect of different energy levels on selected properties of Alfisols treated with different sources of organic amendments. The treatments consisted of soils with compost (10 pots), cow dung (10 pots), and control. These were laid out in a completely randomized design and replicated two times. All pots (soil ± amendment) were saturated and allowed to drain freely for 24 hours and 48 hours, respectively, and compacted to 0, 75, 150, 225, and 300 Joules of energy. Bulk density (BD), penetration resistance (PR), saturated hydraulic conductivity (Ksat), particle size distribution (PSD), gravimetric moisture content (GMC), and moisture retention (MR) was determined from treated plots. Results obtained indicated that the soil is sandy. BD and PR were highest in control, with mean values of 1.803 g cm-3 and 1.762 kg F cm-2, respectively. Treatment with compost improved the BD and PR with lower mean values of 1.320 g cm-3 and 1.283 kg F cm-2 respectively, compared to cow dung and untreated control. With increasing energy inputs, there was a highly significant difference amongst the studied soil properties at all the energies at p&lt;0.0001. Minimum tillage is recommended to reduce the stress caused by heavy energy inputs on these soil properties. The organic matter will directly contribute to plant nutrients such as nitrogen, phosphorus, and micronutrients.

Effects of water content change path on laboratory and field compaction of lime stabilized expansive soil

Generally, the soil requires to be compacted in highway construction. The expansive soil is a special type of soil that is highly susceptible to variations in water content, which affects the degree of compaction at the same compaction energy. In the present study, a series of wet compaction tests and dry compaction tests were carried out in the laboratory. Laboratory test results show that dry compaction will produce a higher optimum water content and a higher maximum dry unit weight compared to wet compaction, because its matric suction is smaller. Field compaction tests were also conducted, the results showed that there might be a risk of under-compacting soils during construction caused by different water content change path in actual field conditions.

At-rest lateral earth pressure in compacted silica sand

ABSTRACTAt-rest lateral earth pressure is one of the major sources of disturbing force on retaining structures and provides resisting force for anchors and piles. A theoretical model is proposed, and experimentally validated, for the normally and overconsolidated at-rest lateral earth pressure coefficients in silica sand. In addition, the experiment illustrates a procedure to determine the maximum historic vertical stress equivalent to the standard and modified Proctor energies of compaction. The previous equivalent maximum historic vertical stress, which is found to be constant for the relative density reached by each energy of compaction, is then proposed as a parameter to determine the overconsolidation ratio within the backfill and its resultant at-rest lateral earth pressure distribution behind a vertical wall. The at-rest lateral earth pressure distribution incorporated with the overconsolidation ratio naturally results in a greater magnitude and is curved in contrast to the linear distribution characteristic of a normally consolidated state. A limit equilibrium analysis and a plane-strain particle-scale model of a granular media under critical state were used to derive the equations herein.

Strength and deformation characteristics of compacted loess with different moisture content and compaction energy

The normal operation of superstructure in loess areas will be related closely to the strength and stability of compacted loess. Loess samples derived from two different engineering sites in China were compacted with different compaction energy, and the main factors which will affect the strength and deformation of compacted loess were analyzed. Different soil samples were prepared with varying moisture content of 11 %–19 %. As the moisture content increases, the compression deformation of compacted loess increases. The immersion influence coefficient suitable for compacted loess was calculated in this study. During soaking in water for 4 days, the California Bearing Ratio (CBR) decreases gradually. Especially, in the process of soak, the lower the initial moisture contents of sample, the more obvious the CBR degradation of sample. It is suggested that soil should be compacted with appropriate compaction energy and moisture content. Furthermore, the loess should be compacted under the condition that the moisture content is slightly greater than the optimal moisture content. When the current moisture content is about 1.02 times the optimal value, the compaction performance of loess is better. As disclosed in this research, the compacted loess in optimal compaction state has smaller compression deformation, better stability and weaker sensitivity to saturation.

Insight on characterization through porosity-to-lime index of a stabilized soil for the long-term

The strength of lime-cemented soils has received significant attention in previous studies. However, limited research has focused on studying soil mixtures for extended durations beyond 365 days, which is essential for understanding shear strength, microstructure, unconfined compressive, and matric suction. Consequently, there is a need to explore the long-term behavior and unsaturated properties of soil specimens cured for up to 500 days using appropriately hydrated lime, considering the semi-empirical porosity/lime index. By investigating various curing times ranging from 15 to 500 days, as well as employing different compaction energies (standard, intermediate, and modified) and lime content ranging from 3% to 9% by weight, this study aims to characterize the evolution of resistance and unsaturated properties of lime-cemented soils. The semi-empirical porosity/lime index is employed to guide the characterization and analysis of the mixtures' resistance properties. By developing equations to estimate the resistance of these mixtures, the study contributes to reducing lime consumption (and reducing CO2 emissions during its production) and optimizing curing time, leading to environmentally friendly geotechnical projects. Due to the utilization of the porosity/lime ratio, lime consumption can be minimized, and curing time can be fixed, resulting in a significant reduction in energy requirements, which is beneficial for the environment. The outcomes of this research have profound implications for the design and construction of sustainable structures such as dams, pavements, and slope protection systems, ensuring their long-term stability, resilience, and ecological balance.

Influence of Compaction Energy on the Mechanical Performance of Hot Mix Asphalt with a Reclaimed Asphalt Pavement (RAP) and Rejuvenating Additive

The Mexican asphalt paving industry is increasingly interested in using reclaimed asphalt pavement (RAP) to produce hot mix asphalt (HMA) due to its economic and environmental advantages. However, an ill-defined methodology for integrating RAP into the HMA mix design has hindered its use. This paper investigates how compaction energy affects both rejuvenated and non-rejuvenated recycled HMA mixtures. A Superpave gyratory compactor was used to determine the optimal binder content and find a balance between flexibility and stiffness that meets cracking and rutting resistance requirements. Various recycled HMA mixtures were subjected to different compaction energy levels (75, 100, and 125 gyros), different RAP contents (15%, 30%, and 45%), and various dosages (10%, 15%, and 36%) of the rejuvenating additive Maro-1000®, following the blending chart. Performance was evaluated using the Hamburg wheel tracking test (HWTT) and the fracture energy flexibility index test (I-FIT). The results demonstrate that mixtures with RAP, a rejuvenating admixture, and varying compaction energies exhibit favorable mechanical behavior. However, both rejuvenated and non-rejuvenated mixes with 15% RAP showed performance comparable to conventional mixtures. They improved stiffness by up to 46% while reducing the flexibility index to 25%, striking a balanced equilibrium between rutting resistance and cracking susceptibility.

Mechanistic analysis of splash erosion on loess by single raindrop impact: Interaction of soil compaction, water content, and raindrop energy

Theoretical and experimental studies have demonstrated that splash erosion on agricultural land can affect agricultural production and the ecosystem. However, the splash erosion process mechanism of loess erosion under the effects of a single raindrop remains unclear. Therefore, this study investigates the effects of single-raindrop splash erosion on the cohesion and internal friction angle of compacted loess under multiple compaction, water contents, and single-raindrop kinetic energies. The results showed that the depth and diameter of the crater were linearly related to both the raindrop kinetic energy and the loess compaction. The variation of crater depth is always lower than the variation of crater diameter, and the effect of the amount of raindrop energy on crater splash erosion is higher than the effect of the variation of compaction on crater splash erosion. Raindrops with higher kinetic energy have higher erosiveness, and this can shorten the ponding point time. When the water content is constant, the fitting curve of cohesion and compaction is the exponential relationship. The increment of cohesion decreases with increasing water content when the water content is lower than the optimum water content (12.7%) and increases with increasing water content when the water content is higher than the optimum water content. However, the increment of internal friction angle consistently increases with increasing water content, which is not affected by the optimum water content. This study could be a reference for soil erosion control in the Loess region.