Penetration Resistance Measurements Research Articles

Characterization of the soil compaction based on the mapping of the apparent electrical conductivity

Based on the measurement of soil penetration resistance (PR), it is possible to identify compacted soil layers, where root growth may be harmed, affecting crop development and yield. The objective of this work was to analyze the use of management zones (MZ), delimited on the basis of mapping of the spatial variability of the soil apparent electrical conductivity (ECa), in the differentiation of soil compaction levels. The work was carried out in a 25.8-ha no-tillage area, cultivated under a center pivot. The ECa was measured under two soil moisture conditions (13.7 and 16.45%), using the Terram® equipment. Soil penetration resistance (PR) was measured using the SoloStar PLG5500 penetrograph. Based on the spatial variability ECa mapping, management zones (2, 3, and 4 zones) were delimited. The mean PR values ??of each MZ were compared by the t-test of means. It was possible to differentiate mean values ??of penetration resistance (PR), which vary from 0.9 to 2.10 MPa, from the characterization of management classes generated on the basis of the ECa spatial variability. The highest stratification of PR values ??was obtained as a function of sampling directed at delimited management zones when the soil had lower moisture content (13.7%). The highest mean PR values ??were obtained for the split of the ECa map into at least three classes. It was identified that for the study area there is no need to perform any mechanical decompaction operation.

A hybrid method for characterizing tillage-induced soil physical quality at the profile scale with fine spatial details

Robust methods are needed to assess tillage-induced changes in the physical quality of agricultural soils. Most soil physical quality (SPQ) evaluation procedures are based on the analysis of a limited number of soil cores randomly sampled in the soil profile. Such procedures likely fail to properly capture the spatial patterns in soil structure induced by tillage implements and vehicle traffic, resulting in a misleading SPQ diagnosis. We propose a hybrid method that couples high-resolution soil penetration resistance measurements with soil core sampling to derive high-resolution data grids of SPQ indicators encompassing the soil profile structural heterogeneity. The method builds on strong experimental relationships between soil penetration resistance and bulk density, and between bulk density and the soil hydraulic properties. We tested our method on a silt-loam soil with three tillage treatments (moldboard plowing, deep loosening with a tine cultivator, and minimum tillage), each including a zone impacted by the wheel traffic. The results allow visualization and analysis of the effect of tillage treatments and vehicle traffic on the soil SPQ indicators with a high level of spatial detail. The proposed methodology can be used to compare various soil management techniques or to monitor the temporal evolution of SPQ. As such, it can be a valuable tool to guide agricultural soil management. Furthermore, the generated high-resolution soil physical parameter grids could be used to parameterize numerical hydrodynamic models and estimate water and solute fluxes with distributed parameters representing the actual soil profile heterogeneity.

Basic Digital Image Color Analysis for Nondestructive Testing of Setting and Curing Process of Building Products: Application to Thin Render Layers Sprayed at Building Site

Abstract Many building products are put in place in liquid or plastic state. During the first hours and days, the products set and dry, changing their mechanical properties, and their visual aspect also changes in parallel because of the hardening process. In the case of sprayed products, the technical supervisor must know at any time the quality of every sprayed layer and finally determine when it has reached its point of maturity that allows considering it as ready or suitable to receive the next layer. Experimented professionals often use personal visual ability to recognize the evolution of visual colors and surface textures of thin render layers applied on site as capacity to determine this right moment, especially in the case of dry mix sprayed products that harden progressively during curing process. However, these visual assessments are not considered decisive as a technical procedure to assess the evolution of the sprayed product properties. As they are thin layers, it can be considered that the information acquired from their surface is sufficiently representative of their interior qualities. The aim of this study is to correlate information obtained in successive local measurements of humidity and penetration resistance taken on the early surface of a dry mix product just sprayed (portland cement mortar and gypsum plaster) during its setting phase and to compare it with its surface digital color evolution during this process. The goal was to explore whether it is possible to establish a relationship between evolution of resistance penetration and evolution of some digital image basic parameters during the setting and drying period. If this relationship were sufficient, conventional point-to-point contact tests (destructive tests) could be replaced in the future by nondestructive surface visual tests. This is very useful at the building site where there are big surfaces to assess and only a short time to make the right decisions.

Mechanical and Durability Properties of Latex-Modified Hybrid Fiber-Reinforced Roller-Compacted Rapid-Set Cement Concrete for Pavement Repair.

This study evaluated the mechanical properties and durability performance of latex-modified hybrid fiber-reinforced roller-compacted rapid-set cement concrete (LMHFRCRSC) for emergency repair of concrete pavement. Experimental parameters included the blend ratio of the hybrid fiber, which comprised natural jute fiber (0–0.2 vol.%) and structural synthetic fiber (0–2 vol.%). The mechanical performance of LMHFRCRSC of various blend ratios was evaluated in terms of compressive, flexural, and splitting tensile strength. Durability assessment included chlorine ion penetration and abrasion resistance measurements. Compressive and flexural strength values of 21 and 3.5 MPa, respectively, were the set targets after 4 h of curing; a compressive strength of 35 MPa, a flexural strength of 4.5 MPa, a splitting tensile strength of 4.2 MPa, and chloride ion penetration of 2000 C or less were required after 28 days of curing. Our test results confirmed that all mix proportions satisfied the target values, regardless of the blend ratio of the hybrid fiber. Specifically, the mechanical performance of the concrete improved as the blend ratio of the structural synthetic fiber increased. With regard to durability, a greater amount of jute fiber, a hydrophilic fiber, enhanced the concrete’s durability. Additionally, incorporating jute fiber of 0.6 kg/m3 provided excellent chlorine ion penetration resistance. The optimal blend ratio for the hybrid fiber was natural jute fiber at 0.6 kg/m3 and structural synthetic fiber at 13.65 kg/m3 (mix: J0.6 + P13.65); with this mix proportion, a chloride ion penetration amount of 1000 C or less and maximum mechanical performance were achieved.

Impact of Tillage Systems Equipped with Row Cleaners on Some Selected Soil Physical Properties under Wheat Cropping

Availability of improved tillage and herbicides during the last decades has enhanced the acceptance of conservation tillage. The main constrain to this type of tillage, particularly, zero tillage is high level of crop residue, which reduces seeding quality, soil temperature, etc. Accordingly, a study was initiated by equipping row cleaners with no-till system under wheat cultivation. For this purpose, a field experiment was laid in a split-split plot design with three types of row cleaners, three sub-treatments of travelling speed, and two sub- sub treatments of tillage depth. The results indicated that the soil temperature was highly affected by percent of residue left. Measurement of penetration resistance indicated that hard pan was not a potential limiting factor for the crop root development. The soil water was increased by 8.83%, 15.33% and 12.54% under no-till without row cleaner (M1), no-till with narrow row cleaner (M2) and no-till with wide row cleaner (M3) respectively compared to that under conventional tillage (CT). The percentage of soil loss reduction under M1, M2 and M3 were 53.11%, 59.62% and 50.51% compared to that under CT. The water losses were also reduced by 46.19%, 48.65% and 46.86% under these treatments as compared with CT.

Development of a mobile robot-based combined sensor platform to determine the corre- lation between soil penetration resistance and electrical conductivity

Open-field farming involves successive major processes such as preparation of soil, planting the seed, adding pesticides and fertilizers, irrigation, cultivation, and harvest. The main aim of all processes is to achieve maximum yield out of the available agricul-tural landscape. It is necessary to collect geo-referenced descriptive data on soil characteristics, such as soil penetration resistance and electrical conductivity before starting all these processes. In this context, agricultural robots offer highly promising technologies provid-ing valuable soil data, lower production costs, reduced manual labour, and maximum crop efficiency. The aim of this study is to design and develop a combined sensor platform and a GPS-guided 4WD agricultural autonomous robot to provide rapid measurement and mapping of the soil penetration resistance and the electrical conductivity for precision farming applications. The agricultural robot is a nonholonomic mobile robot, which has a differential steering mechanism and can be forwarded to stable-target points. The combined sensor platform, which is a y-axis shifter driven by a DC motor with reducer, consists of the Wenner array probes and load cell-based penetration rod. AutoCAD software was used for designing and drawing of the robot and measurement platform. All software was coded in Microsoft Visual Basic.NET programming language. Field studies were conducted to measure the soil penetration resistance, electrical conductivity, and determine the correlation between soil penetration resistance and electrical conductivity. As a result, the ranges of the soil measurement were observed between 1.13 MPa-2.14 MPa for penetration resistance and 0.14-0.33 dS/m for electrical conductivity. Results showed that there is a fairly strong negative relationship between the soil penetration resistance and the electrical conductivity (R2 = -0.78).

Pedotransfer Functions For Estimation Of Soil Moisture Constants From Penetration Resistance Measurements And Some Soil Properties

Studies to prediction of soil moisture constants and other soil properties rather than direct measurements were never dwindle importance. Models were derived from other soil properties obtained easily. Therefore, in this study focused on the predictability of some moisture constants, whose determination was often difficult and time-consuming, from penetration resistance measurements. In the improvement of alternative models for the estimation of moisture constants; in addition to penetration resistance, textural fractions (sand, clay and silt), bulk density, CaCO3 % and organic matter contents were included. The models were created according to soil groups with different textures (sandy, loamy, clay) for moisture constants at 0.1, 0.33, 0.5 and 15 bar. In the models for estimation of 0.1, 0.33, 0.5 and 15 bar moisture content, the highest differences in R2 values (0.61, 0.60, 0.64 and 0.59) between the actual and the predicted data was obtained for loamy soils. For this group, the root means square error (RMSE) ranged between 1.32 and 1.90 %, and in addition, the mean error (ME) was determined to be in a range from 1.53 to 2.05 %. For the estimation of moisture content at different soil moisture tensions using organic matter, bulk density, clay and penetration resistance properties, the coefficient of determination ranged from 71 to 77 %. Therefore, it is concluded that the alternative models, developed using penetration resistance or by the addition of some other soil properties, could be used safely in the loamy texture soils.

Resistance of soil to penetration as a parameter indicator of subsolation in crop areas of sugar cane

Sugarcane is a very important economic crop that relies heavily on agricultural machinery, which contributes to soil compaction and a consequent decline in productivity. Subsoiling operation reduces the problems caused by compression; however, it is necessary to know its location and intensity. Accordingly, the aim of this work is to present a compression diagnostic method based on soil resistance to penetration as the parameter that indicates need for intervention in the subsoil. Measurements of penetration resistance was carried out in areas of sugarcane, located in the municipalities of Goianésia, Barro Alto and Santa Isabel, in the Brazilian state of Goiás. The Falker penetrometer (PLG 1020) was used, adjusted to a maximum depth of 40 cm and adopted as a critical resistance value of 4.0 MPa. The data were interpolated using kriging and adjusted in AutoCAD 2013 (Autodesk). The methodology proved effective in areas of compacted soil, and the surface layer had less resistance. The reduction in soil preparation was 96.54% and when considering the topographic adjustments, the reduction was 74.07%, showing the viability and importance of the diagnosis to show the proper management.

The Relationship Between Soil Heterogeneity and Cellulolytic Activity

Abstract This article examines the relationship between soil heterogeneity and cellulolytic activity. The investigated substrate was a typical chernozem (black soil). Cellulolytic activity was studied by the application method across a regular grid of 7×15 points (21×45 m). The distance between the measurement points was 3 m. Soil heterogeneity determined by the measurement of soil penetration resistance using a hand penetrometer Eijkelkamp. Measurements of soil penetration resistance were fixed to a depth of 100 cm at intervals of 5 cm. Geostatistical analysis showed a high level of spatial dependence of soil cellulolytic activity. Significant correlations were obtained between the spatial distribution of cellulolytic activity and soil penetration resistance at different depths. The results reflect a significant correlation of soil conditions at different depths.

Effect of Previous Crop Roots on Soil Compaction in 2 Yr Rotations under a No-Tillage System

Compacted soils affect global crop productivity and environmental quality. A field study was conducted from 2014 to 2020 in the northern Great Plains, USA, to evaluate the effect of various rooting systems on soil compaction in 2 yr rotations of camelina (Camelina sativa L.), carinata (Brassica carinata A.) and a cover crop mix planted in place of fallow with durum (Triticum durum D.). The study was designed as a randomized complete block with three replications in a no-tillage system. The soil was classified as Dooley sandy loam (fine-loamy, mixed, superactive, frigid Typic Argiustolls) derived from glacial till parent material. Three measurements of soil penetration resistance (PR) were taken with a penetrometer to a depth of 0–30 cm within each plot. Soil moisture contents were determined using a TDR sensor at the time of PR measurements. Both measurements were monitored prior to planting in spring and after harvest. Initial PR results from spring 2014 showed that all plots had an average of 2.244 MPa between the 8–20 cm depth, due to a history of tillage and wheel traffic caused by various field activities. Covariance analysis indicated that soil PR was not significantly affected by crop type and moisture content. After one cycle of the 2 yr rotation, the 2016 measurements indicated that the compacted layer existed at the same initial depths. However, after two and three cycles, soil PR values were reduced to 1.480, 1.812, 1.775, 1.645 MPa in spring 2018 and 1.568, 1.581, 1.476, 1.458 MPa in 2020 under camelina, carinata, cover crop mix, and durum treatments, respectively. These findings indicate that previous cover crop roots could effectively improve soil compaction by penetrating the compacted layer, decompose over time and form voids and root channels. Although these results are novel and significant, further research is needed on different soils and under cover crops with different root systems to support our findings prior to making any conclusion.

Within-Field Spatial Variations in Subsoil Bulk Density Related to Crop Yield and CO2 and N2O Emissions

Subsoil compaction is an increasing problem in modern agriculture, but is not easily recognized in practice, also because of possible within-field spatial variations. This paper addresses the question of how within-field spatial variations in soil bulk density and other soil characteristics relate to within-field spatial variations in crop yield and CO2 and N2O emissions from soil. Four fields (5 to 20 ha each) were selected at the suggestion of crop farmers, and sampled using a random soil sampling design (100 samples per field). Undisturbed soil samples were taken at depth of 5-10, 30-35, and 50-55 cm and soil bulk density and CO2 and N2O emissions measured under controlled conditions. At each sampling point, also top soil (0-20 cm) samples were taken for determination of pH, texture, SOM, and (micro)nutrients, and soil penetration resistance measurements and visual assessments of soil structure were made. Wheat yields were recorded with harvesters equipped with GPS and yield recorders. Mean soil bulk density in the sub-soil (30-35 cm) ranged between fields from 1.36±0.08 to 1.60±0.11 g cm-3. Mean wheat yields ranged between fields and years from 7.6±0.6 and 11.3±2.4 Mg ha-1. Semi-variogram analyses showed that crop yields and soil properties were mostly spatially dependent; nugget-to-sill ratios were < 25% with ranges of 137 to 773 m. The ratio of CO2 emissions to N2O emissions was negatively related to soil bulk density, especially following N application.In conclusion, within-field spatial variations in subsoil bulk density were successfully related to spatial variations in crop yield and in CO2 and N2O emissions. The ratio of CO2 emissions to N2O emissions had a much greater response to spatial variations in soil bulk density than wheat yield. Our study suggests that N2O emission factors may depend on (sub)soil bulk density.

Application of Portable Soil Strength Probe on Bengkalis’ Peat

Peat shear strength measurement in the laboratory is very challenging because undisturbed sampling of very soft peat is very difficult to get. Traditional in-situ test such as standard penetration test (SPT) and cone penetration test (CPT) on peat also have problems i.e. they are very heavy and the measurement is not sensitive on very soft peat. This study described the application of portable soil strength probe on peat. The tool can measure penetration resistance in term of stress and torsion in newton meter. Peat samplings and physical laboratory tests were also conducted. The location of the study is Bengkalis Regency, Riau Province. The result revealed that peat (up to 6-meter depth) at the location is mainly sapric, low ash content with water content more 1000%. Penetration resistance is predominantly 400 kPa. While shear test depicts that peat is mainly frictional with friction angle mainly between 17-21 degrees and very low cohesion i.e. 0.8-3kPa. This study revealed that fibre content correlate moderately with penetration resistance and shear strength. this preliminary work suggested that soil strength probe may be useful for peat characterization.

Penetration Resistance of Bengkalis’ Peat From Hand Cone Penetration Test

In situ soil investigation on peat is not easy due to its low bearing capacity and high compressibility. Traditional in-situ test such as cone penetration test (CPT) are quite heavy which make movability on peatland difficult and slow. This study described the measurement of peat penetration resistance using portable hand cone penetration (HCP) test. The location of this study is at Bengkalis’ Island. Visual observation and laboratory tests show that peat at the site, mainly, can be classified as sapric and low ash. Dry unit weights range from 1.06-1.54kN/m3 with specific gravity range between 1.19-1.81. HCP test show that penetration resistance range from 84-674kPa with majority of it is at 300kPa. Estimated unconfined compression test suggested soft to medium consistency. Equivalent penetration resistances of full CPT are between 110-910kPa. There is tendency that higher fibre content may increase penetration resistance.

Parameters influencing run-off on vegetated urban soils: A case study in Marseilles, France

In urban areas, episodes of extreme precipitation may generate run-off floods, but urban soils are seldom considered in spatial planning documents. Our aim was to assess the infiltration of vegetated urban soils and to identify the soil parameters affecting infiltration in order to explore the potential of these soils for run-off mitigation under a Mediterranean climate with extreme precipitation episodes. We compared vegetated soils in the “urban” zone of the Marseilles’ 16th district (France) either lying on former clay quarries or tile factories (T) or not (NT) and with different land-uses. We used a simplified method to measure field saturated hydraulic conductivity (Kfs), measured penetration resistance in the first 0.15 m (Qd) and analysed physico-chemical properties in the first horizon. Levels of run-off production were estimated according to Kfs and an adaptation of USDA Hydrologic Soil Groups. All soils were Technosols or Anthrosols regardless of their prior history. We found that land-use history influenced Kfs, with T soils and soils with current vegetated land-use younger than 13 years having lower Kfs than NT soils and soils with land-use older than 13 years. Soil organic matter content influenced Kfs positively when soils were young, while vegetation cover and penetration resistance (most of the soils had Qd > 2 MPa) had not a clear effect on Kfs. Overall, combining Kfs and soil depth, 14.3% of the T soils and 84.6% of the NT soils had low levels of run-off production. It is therefore recommended that 1) Technosols or Anthrosols should be characterised for their unique physico-chemical and physical properties but also for their land-use history, and 2) the infiltration of these soils should be considered in spatial planning documents.

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The article shows the possibility of assessing the level of recreational transformation of public green spaces in terms of the soil penetration resistance and proved that the profile distribution of soil penetration resistance values is an information valuable indicator for establishing the level of recreational load. The measurement of soil penetration resistance within the park Novooleksandrivsky (Melitopol, Ukraine) was performed at 179 points on a quasi-regular grid with a distance between the points of accounting 30–40 m. The soil penetration resistance was revealed to be naturally increases with the growth of the depth of the soil layer from 2.42±0.023 MPa in the soil layer 0‒5 cm to 9.86±0.078 MPa in the soil layer 95‒100 cm. The process of increasing soil penetration resistance with depth is not monotonous, resulting in the presence of local penetration resistance at a depth of 50‒55 or 55‒60 cm. The variability of soil penetration resistance within one layer, which is described by the variation coefficient, is in the range of 6.98‒20.54%. This indicator naturally changes by profile. The high level of variation is peculiar to the top layer of soil 0‒5 cm, where the coefficient of variation of soil penetration resistance is 12.94 %. It is proved that under the influence of recreation there is a formation of functional layering of soil, expressed in the existence of structures in which layers of soil with greater soil penetration resistance are degraded by layers of less penetration resistance. The presence of such features can cause a complex of negative phenomena, which are associated with restriction of moisture penetration into the soil, reducing the migration capacity of air in the soil, limiting the growth of root systems of plants and the movement of animals. Functional layering can form local waterproof horizons that will limit the soil’s ability to absorb moisture. Correlational analysis of the connection of soil penetration resistance and the indicator of recreational load allowed to establish that with the increase of recreational pressure soil penetration resistance increases. The established correlational dependence of soil penetration resistance indicators and the assessment of the level of recreational load allows us to consider the possibility on the basis of penetration resistance data to quantify the level of recreational load. We completed this task with the help of multiple linear regression with the procedure of step-by-step inclusion of predictors in the model. The regression model is statistically significant and has made it easy to explain 46% of the varying indicators of recreational load. The step-by-step inclusion procedure provided an opportunity to choose the 10 most informative predictors for use in the model. The following levels of recreational load were established: low level, below moderate, moderate level, above moderate to high levels, as well as the procedure for indication of these levels based on soil penetration resistance data at different depths. The levels of recreational load were indicated on the basis of the procedure of classification trees on the soil penetration resistance data

Assessing extraction trail trafficability using harvester CAN-bus data

ABSTRACT Modern forest machines with a Controlled Area Network (CAN)-bus managed diesel engine and hydrostatic transmission can continuously measure power expended in traveling. At a constant speed on level ground, the power is expended in overcoming motion resistance, which is directly related to wheel sinkage and hence to site trafficability. In cut-to-length timber harvesting, the harvester precedes the forwarder on the site, making it feasible to utilize the harvester to collect data on site trafficability to produce a trafficability map for the forwarder. CAN-bus trafficability mapping was tested with an 8-wheeled Ponsse Scorpion King harvester and an 8-wheeled Ponsse Elk forwarder instrumented for collecting transmission power expenditure, in addition to appropriate available CAN-bus information. Trafficability was also mapped based solely on momentary engine power in order to eliminate the need for additional pressure transducers. The CAN-bus data showed good results for mapping site trafficability when compared to soil penetration resistance and harvesting machinery wheel rut depth measurements. Assessing harvester rolling resistance using CAN-bus data offers an interesting possibility to map harvesting site trafficability also in Big Data scale. Since modern harvesters are practically ready for indirect power recording, the additional cost of fully automated and comprehensive trafficability mapping as part of operative forestry is negligible.

Penetration and relaxation behavior of JSC-1A lunar regolith simulant under cryogenic conditions

Lunar in situ resource utilization discussions have recently been focused on the presence and distribution of ice in the upper layers of surface regolith, in particular within the confines of the permanently shadowed regions. Extraction ideas - ranging from simple scooping to percussive drilling and thermal (optical) mining utilizing cold-trap volatile capture – require detailed knowledge of the mechanical properties of icy regolith as we are likely to encounter. Penetrometers provide a robust and straightforward measurement technique for determining soil properties, but previous research fails to reliably show measurement sensitivity to increasing ice content due to difficulties in experimentation at cryogenic conditions. To display the capability of a simple conical penetrometer to discern saturation levels of icy regolith simulant within an expected range, we conducted laboratory penetration and subsequent relaxation measurements of JSC-1A lunar simulant using a specially-designed cryogenic apparatus which minimizes sample temperature fluctuation as well as the thermal mismatch between the penetrating probe and tested sample. We measured penetration resistance and force relaxation behavior for JSC-1A lunar simulant under constant displacement rate penetration at ~300 mTorr pressure, ~110 K sample temperature, 170 K to 190 K probe temperature, and ice contents of 0% to 12% and 100%. Penetration resistance and relaxation behavior both showed sensitivity to ice content, with parameters of best-fit curve models offering simple empirical predictors of saturation. A critical ice content of 1% to 3%, wherein a significant increase in penetration resistance occurs, is identified as being fundamentally influenced by the filling of substantial pore space with grouting ice. A decrease in viscoelastic behavior of high ice content samples at cryogenic temperatures is noted, and inhibition of relaxation mechanisms due to activation-energy-based temperature effects is also demonstrated in dry, ice-free simulant. Additional research across the spectrum of ice saturations, temperatures, and pressure environments likely to be found in extraterrestrial environments is suggested to improve upon these results, in particular using cryogenic systems even more specialized to reduce thermal issues and increase load capacities and apparatus stiffness. Such additional information will serve to advance the potential use of these results and this technology in future exploratory missions.

Soil available water and plant growth in relation to K:Na ratio

The effect of K:Na ratio on plant available water (PAW), least limiting water range (LLWR), integral water capacity (IWC), penetration resistance and plant growth was assessed in this study. Treatment solutions including different K:Na ratios at two electrical conductivity levels (EC = 3 and 6dSm−1) were applied into an agricultural loamy soil in pots using capillary rise from the bottom, and the soil in the pots were kept at a water content close to field capacity for one month. In addition, maize was planted into the treated soils in three replicates. PAW, LLWR and IWC were calculated by soil available water calculator (SAWCal) software based on measurements of soil water retention and penetration resistance. In our study, LLWR was limited by PAW. The results showed that PAW of the treated soils increased significantly with increasing K:Na ratio in comparison with the control soil at both EC levels, due to increasing clay dispersion with increasing K:Na ratio. A reduction in the soil pore size due to migration of dispersed clay particles into soil pores could be a possible reason for the increase in PAW. Positive relations were found between PAW and meso-porosity and micro-porosity at both EC. Maize growth significantly increased with increasing PAW at EC = 6dSm−1. It can be concluded that the application of different K:Na ratios induced different degrees of dispersion of clay particles, which presumably migrated into soil pores, changing the soil pore size distribution towards smaller pores. This increased PAW in our studied soil, with positive effects on plant growth.

The Effect of Accelerator Dosage on Fresh Concrete Properties and on Interlayer Strength in Shotcrete 3D Printing

Recently, the progress in 3D concrete printing has developed enormously. However, for the techniques available, there is still a severe lack of knowledge of the functional interaction of processing technology, concrete rheology and admixture usage. For shotcrete 3D printing technology, we present the effect of accelerator dosages (0%, 2%, 4% and 6%) on fresh concrete properties and on interlayer strength. Therefore, early yield stress development up to 90 min is measured with penetration resistance measurements. Deformation of layers under loading is investigated with digital image correlation and a mechanical testing machine. One point in time (10 min after deposition) is examined to quantify vertical buildability of elements depending on the accelerator dosage. Four different interlayer times (0, 2, 5 and 30 min), which occur for the production of small and large elements as well as due to delay during production, are investigated mechanically as well as quantitatively with computed tomography regarding the formation of cold joints. With increased accelerator dosage, an instantaneous increase in early age yield stress and yield stress evolution was observed. An increase in interlayer time leads to a reduced strength. This is mainly attributed to the observed reduced mechanical interlocking effect of the strands. Finally, a model to describe interlayer quality is presented. In the end, advantages as well as limitations of the findings are discussed.

Wear modelling of soil ripper tine in sand and sandy clay by discrete element method

Wear and friction cause huge economic losses in the agriculture and mining industries. Wear simulations of working elements, materials, and surfaces that can reduce downtime and economic losses. This work proposes the use a cone penetration resistance measurement result as option to determine movement resistance of soil ripper tine by the discrete element method. It allows avoiding mechanical properties investigation of soil. Simulation made in sand and sandy clay helps to compare wear track of tine wear plates with actual wear. The actual wear was evaluated by 3D scanning of a soil ripper tine wear plates made from tungsten carbide and cobalt alloy and compared with simulated tines. Wear loss expressed as loss of area at the cross-section of tine wear plate. The maximum wear loss of scanned ripper wear plate at 0–150 mm working depth is 1.8% and simulated-in-sand and simulated-in-sandy-clay 1.2 and 1.7%. The maximum actual wear loss caused 57.9% wear loss of cross-section area at 150–204 mm working depth. Simulation in sand and simulation in sandy clay soil 6.9 and 9% caused by lower soil resistance than in field experiments. Simulations in sandy clay soil increased the draft force by 3.9 and 2.8 times that in the sand, at 0–200 mm depth, for tine parts to account for the stiffness fraction of sandy clay soil. As an alternative, tine wear evaluation is also suggested from shear energy values.