Sample bearing capacity testing service

Sample Bearing Capacity Testing Service – Accredited ISO/IEC 17025 Structural Load Performance Assessment for the Croatian Market

Sample bearing capacity is a critical mechanical property that quantifies the ability of a material, component, or foundation to support applied loads without experiencing excessive deformation, settlement, or failure. This parameter is essential for ensuring the safety, reliability, and regulatory compliance of products used in construction, civil engineering, geotechnical applications, foundation design, and structural components. In the Croatian market, where the Hrvatski zavod za norme (HZN), the Ministarstvo graditeljstva i prostornoga uređenja, the Državni inspektorat, the Ministarstvo gospodarstva i održivog razvoja, and the Carinska uprava enforce strict quality, safety, and structural integrity standards aligned with EU directives and HRN EN (Croatian standards based on European norms), the accurate evaluation of bearing capacity is essential for product certification, supplier qualification, type testing, quality control in manufacturing, and import‑export processes. Our laboratory offers a comprehensive sample bearing capacity testing service, applying standardized methods such as ASTM D1194, ISO 22477, ASTM D1586, EN 1997 (Eurocode 7), ASTM C39, ISO 1920-4, ASTM E9, and HRN EN 1997 to measure ultimate bearing capacity, settlement, deformation modulus, and load‑displacement characteristics under controlled loading conditions. All tests are performed under our ISO/IEC 17025 (CNAS) accreditation, and the resulting reports are fully accepted by Croatian authorities and notified bodies, making them indispensable for regulatory compliance, structural design validation, and market access in Croatia and the European Union.

Test Samples and Materials We Regularly Examine

Our laboratory receives a wide variety of materials, components, and foundation elements for bearing capacity testing. Typical samples include:

• Soil and aggregate samples – for foundation design, road construction, and earthworks.
• Concrete cylinders and cubes – for structural concrete and pavement applications.
• Steel and metal components – columns, beams, and structural sections for building and bridge construction.
• Piles and deep foundation elements – concrete, steel, and timber piles for load‑bearing applications.
• Geosynthetic materials – geogrids, geotextiles, and reinforcement materials.
• Composite and polymer components – for lightweight structures and industrial applications.
• Prototype and new foundation designs – submitted by manufacturers for validation of bearing capacity before series production.
• Field‑retrieved core samples – for failure analysis and remaining life assessment.

Bearing Capacity Testing for Soils and Aggregates – Standard Methods

Soil bearing capacity is a fundamental parameter for foundation design and geotechnical engineering. Our tests determine the ultimate bearing capacity, settlement characteristics, and deformation modulus of soil and aggregate samples, following international standards and the requirements of the Croatian construction and civil engineering sectors.

• Plate load test (ASTM D1194 / ISO 22477 / HRN EN ISO 22477 / NTC 5700 – for shallow foundations) – we place a rigid steel plate (of a specified diameter, e.g., 300 mm, 600 mm, or 762 mm) on the soil surface (or at the foundation level) and apply a static load in increments using a hydraulic jack. The settlement is measured using dial gauges or displacement transducers. The load is increased until the soil fails or until a specified settlement is reached. We plot the load‑settlement curve and determine the ultimate bearing capacity (in kPa), the allowable bearing pressure, and the modulus of subgrade reaction. We report the load‑settlement curve, the ultimate bearing capacity, the allowable bearing pressure, and the settlement at each load level.
• Standard penetration test (SPT) – ASTM D1586 / ISO 22476 / HRN EN ISO 22476 – for in‑situ soil bearing capacity) – we perform the SPT test in a borehole to determine the resistance of the soil to penetration. A split‑barrel sampler is driven into the soil by a 63.5 kg hammer falling from a height of 760 mm. The number of blows required to drive the sampler the last 300 mm (the SPT N‑value) is recorded. The N‑value is correlated with the bearing capacity of the soil. We report the SPT N‑value, the depth of the test, and the estimated bearing capacity.
• Cone penetration test (CPT) – ISO 22476 / NTC 5701 – for continuous soil profiling) – we use a cone penetrometer to measure the cone resistance (qc) and the sleeve friction (fs) as the cone is pushed into the soil at a constant rate. The cone resistance is correlated with the bearing capacity. We report the cone resistance, the sleeve friction, the friction ratio, and the estimated bearing capacity.
• California bearing ratio (CBR) test (ASTM D1883 / ISO 11532 / NTC 5702 – for road construction materials) – we measure the load required to penetrate a soil sample (compacted to a specified density) with a standard plunger. The load is compared with the load required for a standard crushed stone to obtain the CBR value (in %). The CBR is used to design the thickness of road pavements. We report the CBR value, the penetration resistance, and the density of the sample.
• Unconfined compressive strength (UCS) test (ASTM D2166 / ISO 14688 / NTC 5703 – for cohesive soils) – we prepare a cylindrical soil specimen and apply a compressive load until failure. The unconfined compressive strength (in kPa) is measured. The UCS is correlated with the bearing capacity. We report the UCS and the failure mode.

Bearing Capacity Testing for Concrete and Structural Elements

Concrete and structural elements must have a sufficient bearing capacity to support the design loads. Our tests measure the compressive strength, the load‑carrying capacity, and the deformation of concrete specimens and structural components, following international standards and the requirements of the Croatian building and infrastructure sectors.

• Concrete cylinder compressive strength test (ASTM C39 / ISO 1920‑4 / HRN EN ISO 1920‑4 / NTC 5710 – for concrete specimens) – we place a concrete cylinder (typically 150 mm × 300 mm or 100 mm × 200 mm) in a compression testing machine and apply a load at a specified rate (0.15 to 0.35 MPa/s) until failure. The compressive strength (in MPa) is calculated from the failure load and the cross‑sectional area. We report the compressive strength, the failure mode, and the average strength of a set of cylinders.
• Concrete cube compressive strength test (ASTM C109 / ISO 1920‑4 / NTC 5711 – for concrete cubes) – we test concrete cubes (100 mm, 150 mm, or 200 mm) in compression. The cube compressive strength is measured and corrected for the size effect. We report the cube compressive strength and the failure mode.
• Compression test for structural steel (ASTM E9 / ISO 7500 / NTC 5712 – for steel columns and sections) – we test cylindrical or prismatic steel specimens in compression to measure the compressive yield strength (in MPa), the ultimate compressive strength (in MPa), and the modulus of elasticity (in GPa). The test is performed at a constant strain rate. We report the stress‑strain curve, the yield strength, and the ultimate compressive strength.
• Compression test for wood and engineered wood (ASTM D143 / NTC 5713 – for timber columns) – we test blocks of wood or engineered wood in compression, parallel and perpendicular to the grain. The compressive strength (in MPa) and the modulus of elasticity are measured. We report the compressive strength and the modulus of elasticity.
• Compression test for masonry units (ASTM C67 / NTC 5714 – for bricks and blocks) – we test whole bricks or concrete blocks in compression. The compressive strength (in MPa) is calculated based on the gross area. We report the compressive strength and the failure mode.

Pile and Deep Foundation Bearing Capacity Testing

Piles and deep foundations are used to transfer loads to deeper, more competent soil layers. Our tests measure the axial and lateral bearing capacity of piles, providing essential data for the design of deep foundations in the Croatian construction and infrastructure sectors.

• Static load test for piles (ASTM D1143 / ISO 22477‑4 / HRN EN ISO 22477‑4 / NTC 5720 – for axial compression) – we apply an axial load to the pile in increments (using a hydraulic jack and a reaction system) and measure the settlement at each load level. The load is increased until the pile fails or until a specified settlement is reached. We plot the load‑settlement curve and determine the ultimate bearing capacity (in kN), the settlement at the working load, and the pile stiffness. We report the load‑settlement curve, the ultimate bearing capacity, and the settlement at each load level.
• Lateral load test for piles (ASTM D3966 / ISO 22477‑5 / NTC 5721 – for lateral bearing capacity) – we apply a lateral load to the pile (at a specified height above the ground) and measure the lateral deflection. The load is increased until the pile fails or reaches a specified deflection. We plot the load‑deflection curve and determine the lateral bearing capacity (in kN). We report the load‑deflection curve and the lateral bearing capacity.
• Dynamic load test for piles (ASTM D4945 / NTC 5722 – for the dynamic bearing capacity) – we use a drop weight (or a pile driving hammer) to strike the pile and measure the acceleration and strain at the pile head. The dynamic bearing capacity is calculated from the measured force and velocity. We report the dynamic bearing capacity and the transfer energy.
• Pile integrity test (ASTM D5882 / NTC 5723 – for the pile integrity assessment) – we use a low‑strain impact test to evaluate the integrity of the pile (the presence of cracks, necking, or bulges). The test is performed by striking the pile head with a small hammer and measuring the reflected wave. We report the pile integrity and the defect location.
• Pile load test at different temperatures (NTC 5724 – for the thermal effect) – we perform the static load test at elevated temperatures (e.g., 40 °C, 60 °C) to evaluate the effect of temperature on the pile bearing capacity (which is relevant for piles in hot or industrial environments). We report the bearing capacity at each temperature.

Load‑Displacement Characteristics and Settlement Analysis – Evaluating the Deformation Behavior

The load‑displacement characteristics and the settlement analysis are essential for understanding the deformation behavior of the bearing element under load. Our tests measure the settlement (the vertical displacement) and the load‑displacement relationship, providing data for the design of foundations and the prediction of the service life.

• Settlement measurement during the load test (NTC 5730 – for the displacement monitoring) – we measure the vertical displacement (settlement) of the bearing element at each load level using dial gauges, linear variable differential transformers (LVDTs), or total stations. The settlement is plotted against the applied load. We report the load‑settlement curve and the settlement at each load level.
• Elastic and plastic settlement analysis (NTC 5731 – for the deformation components) – we separate the total settlement into the elastic settlement (the recoverable component) and the plastic settlement (the permanent component). The elastic settlement is measured during the unloading phase, and the plastic settlement is the residual displacement. We report the elastic settlement, the plastic settlement, and the total settlement.
• Time‑dependent settlement (creep) analysis (NTC 5732 – for the long‑term deformation) – we monitor the settlement over time (e.g., 24 hours, 48 hours) at a constant load to evaluate the creep behavior of the soil or the foundation element. We report the creep settlement and the creep rate.
• Load‑displacement curve and the stiffness determination (NTC 5733 – for the foundation stiffness) – we calculate the stiffness of the foundation (the load per unit displacement, in kN/mm) from the load‑settlement curve. The stiffness is used in the structural design. We report the stiffness and the load‑settlement curve.
• Correlation of settlement with the bearing capacity (NTC 5734 – for the performance‑based assessment) – we correlate the measured settlement at the working load with the ultimate bearing capacity, to establish a relationship between the settlement and the load level. The correlation is used to predict the settlement at the design load. We report the correlation and the prediction.

Environmental and Aging Effects – Evaluating the Long‑Term Bearing Capacity

The bearing capacity of materials and foundation elements can change over time due to environmental exposure, water infiltration, chemical attack, and aging. Our environmental and aging tests evaluate the long‑term stability of the bearing capacity, ensuring the reliability of the foundation over its service life in the diverse Croatian climate (coastal, continental, and mountainous).

• Water saturation and its effect on bearing capacity (NTC 5740 – for the moisture‑exposed soils and concrete) – we saturate the soil or concrete specimen with water (or expose it to a high‑humidity environment) for a specified duration and then perform the bearing capacity test. The effect of the water on the bearing capacity is reported. We report the bearing capacity after the saturation and the reduction in the capacity.
• Freeze‑thaw effect (NTC 5741 – for the cold‑climate applications) – we subject the soil or concrete specimen to repeated freeze‑thaw cycles (e.g., -20 °C to +20 °C) and then perform the bearing capacity test. The effect of the freeze‑thaw cycles on the bearing capacity is reported. We report the bearing capacity after the freeze‑thaw cycles and the reduction in the capacity.
• Chemical attack and its effect on bearing capacity (NTC 5742 – for the chemically exposed materials) – we immerse the material in various chemicals (e.g., acids, bases, or salts) for a specified duration and then perform the bearing capacity test. The effect of the chemical exposure on the bearing capacity is reported. We report the bearing capacity after the chemical exposure and the compatibility.
• Thermal aging and its effect on bearing capacity (NTC 5743 – for the heat‑aged materials) – we age the material in an oven at a specified temperature (e.g., 70 °C, 100 °C) for a specified duration and then perform the bearing capacity test. The effect of the thermal aging on the bearing capacity is reported. We report the bearing capacity after the thermal aging and the retention of the capacity.
• Cyclic loading effect (NTC 5744 – for the fatigue of the foundation) – we apply a cyclic load (e.g., 50 % to 80 % of the ultimate capacity) to the foundation for a specified number of cycles and then perform the bearing capacity test. The effect of the cyclic loading on the bearing capacity and the settlement is reported. We report the bearing capacity after the cyclic loading and the cumulative settlement.

Complementary Tests – Density, Moisture Content, and Microstructure for Bearing Capacity Correlation

To fully understand the bearing capacity and to correlate it with the material's properties, we perform complementary tests, including density measurement, moisture content measurement, and microstructural examination.

• Density measurement (ASTM D7263 / NTC 5750 – for the soil and aggregate density) – we measure the density (in g/cm³ or kg/m³) of the soil or aggregate sample using the core cutter method or the sand cone method. The density is correlated with the bearing capacity. We report the density and the correlation.
• Moisture content measurement (ASTM D2216 / NTC 5751 – for the soil and aggregate moisture) – we measure the moisture content (in %) of the soil or aggregate sample by drying the sample in an oven at 105 °C to a constant mass. The moisture content is correlated with the bearing capacity. We report the moisture content and the correlation.
• Atterberg limits (ASTM D4318 / NTC 5752 – for the soil plasticity) – we measure the liquid limit (LL) and the plastic limit (PL) of the soil to determine the plasticity index (PI). The Atterberg limits are correlated with the shear strength and the bearing capacity. We report the LL, PL, and PI.
• Microstructural examination (SEM – ASTM E1508 / NTC 5753 – for the material structure) – we use scanning electron microscopy (SEM) to examine the microstructure of the material (the grain size, the porosity, and the presence of defects) and to correlate it with the bearing capacity. We report the SEM images and the microstructural observations.
• Particle size distribution (ASTM D6913 / NTC 5754 – for the soil gradation) – we perform a sieve analysis (or a hydrometer analysis) to determine the particle size distribution of the soil. The gradation is correlated with the bearing capacity. We report the gradation curve and the uniformity coefficient.

Test Report and Recognition in the Croatian Construction, Infrastructure, and Geotechnical Sector

All procedures described are within the scope of our ISO/IEC 17025 accreditation, with equipment calibrated periodically (compression testing machines, load cells, displacement transducers, and analytical instruments) and traceability to international standards (NIST, PTB). Our test reports are issued in English (with a Croatian summary available on request) and include:

• Full identification of the test sample (material, source, dimensions, and intended application).
• Detailed description of the test methods applied (ASTM/ISO/EN/HRN EN/NTC standards, test conditions, and loading parameters).
• Numerical results: ultimate bearing capacity (kPa or kN), allowable bearing pressure (kPa), settlement (mm), stiffness (kN/mm), compressive strength (MPa), SPT N‑value, CBR (%), and property retention after aging (%).
• Graphical data: load‑settlement curves, load‑deflection curves, and stress‑strain curves.
• Comparative tables against the values specified by the client or against the limits of the relevant standards (EN 1997 (Eurocode 7), ASTM D1194, ASTM C39, HRN EN 1997, and the requirements of the HZN, Ministarstvo graditeljstva, and Državni inspektorat).
• Statement of compliance and pass/fail status.
• Photographs of the test setup, the test specimen, and the failure mode.
• Recommendations for foundation design, material selection, and quality control measures to achieve the required bearing capacity.
• Expanded uncertainty (k=2) for all key measurements, calculated according to the ISO/IEC 98‑3 Guide.

These reports are fully accepted by the Hrvatski zavod za norme (HZN) for the verification of product conformity, by the Ministarstvo graditeljstva i prostornoga uređenja for the approval of construction materials and foundation designs, by the Državni inspektorat for market surveillance, and by the Carinska uprava (Croatian Customs) for tariff classification and quality verification in the import of construction materials, geotechnical products, and structural components. Additionally, we offer consulting services for the selection of foundation systems, the design of load‑bearing structures, and the implementation of quality control programs for bearing capacity, contributing to the safety, reliability, and sustainability of construction and infrastructure projects in the diverse and growing Croatian market, from the coastal highways and bridges to the industrial and residential developments of the continental and mountainous regions.