Repository of the Institute for Material Testing (RIMS)
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Estimating the concrete compressive strength using ultrasound tomography
No full textEvaluating the compressive strength of concrete without altering the structure is often
achieved using non-destructive testing (NDT) methods. These techniques are popular in practice
due to their low cost and the fact that they leave the structural elements intact. Among them, the
rebound hammer and ultrasonic pulse velocity tests are the most frequently applied. However, a
major drawback is their limited precision when compared to destructive methods. To overcome this
issue, various analytical models have been introduced to better link NDT measurements with actual
compressive strength values. In this investigation, a combined approach using both destructive and
non-destructive techniques was adopted to assess in-situ concrete quality. Due to structural
limitations, core extraction was only feasible from fourteen columns. A polynomial regression
model was applied to establish a relationship between the compressive strength and the velocity of
shear waves obtained from ultrasonic tomography
External validation of the recently reported drying theory
No full textEven though developed drying theory and Deff-MR curves were successfully used, for modelling the suitable drying regimes of roofing tiles on laboratory and industrial scale during last 15 years, its theoretical contribution as a tool on which all internal moisture mechanisms can be easily registered is still not close enough to the brick and tile companies. The main goal of this paper was to additionally externally validate the developed drying theory and to reveal the universal potential of variable Deff-MR curves for various drying application. The first step was to digitalize the various MR vs – time and MR vs linear shrinkage data taken from the literature. These data were further processed in accordance with the reported drying theory. Deff – MR curves were constructed in the next step. These curves were compared with the originally reported one. The shape of curves was at the first sight similar but after a close look actually all deviation of original data from fitted Deff - MR curves had its theoretical explanation. The transition points of internal mechanisms registered on theoretical Deff – MR curve were revealed on externally taken literature data. It is interesting that this pattern was revealed regardless to the fact that the calculation method for time-dependent Deff coefficient was different. This was reliable external validation proof that that the developed drying theory and Deff-MR have universal theoretical and practical significance
Recycling possibilities of wood-plastic composites (WPC)
No full textNowadays, the main goal is to minimize the negative impact of a product or service on
the environment. Wood-plastic composites (WPC) can be produced in a sustainable way, with
minimal waste. WPC composites can be produced from natural raw materials. They can also be
produced as a result of recycling, where either wood or plastic come from the recyclate. In WPC
production a large percentage of waste can be reused. WPC does not contain formaldehyde or
aggressive organic compounds, it is usable product (it can be grinded and reused), as waste it is
not hazardous and can be disposed of with other waste
Fire Simulation in the Garage
No full textThis article presents a fire simulation of a simple garage which is a template for learning fire simulation in
garages. This model is used for academic purposes created in PyroSim Software with an academic license. First of all, the
garage is drawn in AutoCAD 2D. After that geometry is imported into PyroSim as a 2D object. The 3D model was created
in PyroSim. Boundary and initial conditions are declared for the developed model. Also, jet fans are modeled like HVAC
elements with predefined flow. In the simulation, the five jet fans are used. The simulation time is 50 s. The results are
shown as graphical results of smoke production, heat production, temperature, and velocity distribution. It could be
concluded that jet fans work on the exhaust of the smoke
Shortening of Fast Firing in the Ceramic Tile Production by Inorganic Additives – An Upscale to the Industry
No full textThe paper discusses the usage of additives that are protected by the European patent to enhance
the features of ceramic tiles. Under laboratory conditions, various types of additives in different
concentrations (0.15, 0.30 and 0.50%) were added to the ceramic mass, and changes in shrinkage,
modulus of rupture and water absorption were observed. After selecting the appropriate additive
and its concentration, a series of industrial tests is performed. The characteristics of regular
ceramic mass and mass with the selected additive were monitored without adjusting process
parameters in the industrial conditions. Furthermore, utilizing additives allowed for shortening of
the fire time without distorting the characteristics of the final products. The application of additives
in industrial settings has demonstrated that floor tiles can be produced with improved
characteristics and increased production capacity by 6.8%. Thus, significant energy savings and
a lowered CO2 footprint can be provided
Assessment of the Compositional and Radiological properties of Raw Clay and Shale Blends used in Ceramic Brick manufacturing
No full textThe use of shale ore in ceramic brick manufacturing offers numerous advantages, including the possibility of improved strength and thermal stability. Moreover, the environmental impact associated with mining can be minimized by partially replacing raw clay with other alternatives such as shale. The feldspars and other minerals in shale affect the raw brick mixture's workability and plasticity. Therefore, this study examined the mechanical, thermal, and radioactive properties of raw clay and shale mixtures to assess their suitability for ceramic brick production. Key parameters like shrinkage, loss on ignition, compressive strength, and water absorption are specifically examined to determine the effects of adding 10 % and 20 % shale by weight to the factory raw clay mixture. The concentrations of natural (238U, 235U, 226Ra, 232Th, 40K) and artificial (137Cs) radionuclides were measured before and after the firing process to determine the radioactivity of raw clay, shale, and the resulting burnt bricks. Hazard indices and annual effective dose estimations for consumers and industrial personnel were used to assess the radiological dangers related to these products. A comparison of the results of this study with those of related research and regulatory criteria was done to ascertain the safety of the bricks when used for construction. This study provides useful details on potential radiological hazards and the safe use of Serbian shale in ceramic brick production, and suggestions for enhancing the security and usability of building materials.poste
Effect of higher CO2 content on physical and mechanical properties of aerial lime mortars for conservation purposes
No full textUntil the end of the 18th century, lime-based mortars were considered as an element of continuity in built heritage. Repercussions of using incompatible materials in restoration practice were reflected in the development of requirements for using repair mortars that are compatible with the original materials, as lime mortar is. Even though this topic has been extensively investigated from both structural and material point of view, use of lime mortars in restoration works is yet scarce.
This study investigates the influence of increased CO2 content on physical and mechanical properties of aerial lime mortars. As lime mortar is a material that uses CO2 for its hardening process, this consumption is beneficial for environment and material quality as well. After 7 days of curing, samples were placed in accelerated carbonation chamber, with high CO2 content (5%). The results were compared with a reference mortar, cured in standard condition and tested after 180 days. Results show that full carbonation was achieved in accelerated carbonation conditions, verified by both TGA and phenolphthalein test. In reference samples, 8% of still uncarbonated lime was observed after 180 days. These results were in accordance with results of open porosity, showing lower values of samples under higher CO2 conditions. UPV results, used as a tool for accessing anisotropy showed lower values of anisotropy in accelerated carbonation conditions, meaning that higher level on homogeneity in these samples was achieved. Regarding mechanical strengths, flexural strength was 57% higher for accelerated carbonation conditions, when compared with 180-days old reference sample. In the case of compressive strength, this difference was around 32%.This study suggests that trapping CO2 into the structure of aerial lime mortar, have positive effect its hardened properties, making it adequate for its use in conservation practice. Therefore, it opens up new questions regarding filed application of these findings
Interpretable machine learning for predicting complex properties of ceramic materials: A Big Data approach
No full textAs ceramic production evolves toward digital transformation, the role of data-driven modeling becomes
increasingly vital. This work explores how advanced machine learning (ML) techniques can extract actionable
insights from large, multi-dimensional datasets describing the chemical, mineralogical, and granulometric
characteristics of ceramic raw materials. Two key production phases—shaping/drying and firing—are
modeled to predict critical quality parameters such as plasticity, drying loss, water absorption, and bending
strength. Ensemble models, particularly Gradient Boosting and CatBoost, delivered superior performance
(R² > 0.98), while SHAP analysis enabled interpretability of feature contributions. By revealing complex, nonlinear
relationships and material thresholds, these models support real-time process tuning, smarter material
selection, and enhanced sustainability. The study showcases how big data and explainable AI (XAI)
techniques can drive innovation in materials science and industrial process control
Verification of Results of Pile Integrity Test
No full textThe Sonic Integrity Test (SIT) is a sonic echo method based on the theory of one-dimensional stress wave
propagation. By striking the pile head with a hand hammer, a compression wave is generated that propagates
along the pile shaft and reflects from the pile base. An accelerometer (sensor) attached to the pile head records
the accelerations caused by the wave reflections within the pile. Any change along the pile shaft, such as
enlargement or reduction of the cross-section or variation in material quality, produces wave reflections that
are captured by the sensor as changes in acceleration. By integrating the acceleration, a velocity record over
time is obtained and displayed digitally. This represents the final product of the test, providing data on the
quality of the constructed pile. Pile integrity testing is the first step in quality control of constructed piles
followed by load-bearing capacity control by static or dynamic method. Interpretation of the test results is
subjective and may contain a certain degree of uncertainty. In this paper, two practical examples are presented
in which deviations from the expected shape of the reflectogram were identified by integrity testing. The
irregularities were located in the shallow zones of the pile shaft, which enabled visual verification of the
results after excavation around the pile head. In the first case, instability of the embankment during pile
construction caused soil collapse into the borehole, which resulted in a negative reflection immediately after
the initial impulse on the signal. The pile concrete within the top 5 m was of poor quality and prone to
disintegration, and the remediation measure was to replace the pile with a new one. In the second case, the
anomaly observed on the signal was the consequence of heavy inflow of groundwater, which washed out the
concrete in the upper 3 m of the pile. After reaching sound concrete during excavation, formwork was placed
and the pile was concreted up to the design level. The integrity test was repeated, and the return signal showed
a positive result, with a minor negative reflection at the interface between the new and old concrete. These
examples confirm the reliability and efficiency of this simple and rapid method in assessing the integrity of
constructed piles. The experience of the engineer conducting the test is of crucial importance for the proper
interpretation of the reflectogram. Pile integrity testing provides a fast and economical means of detecting
potential irregularities at an early stage of the project, which may otherwise compromise the safety and
functionality of the structure in service. In such cases, remediation during the foundation construction phase is
technically simpler and more cost-effective, which emphasizes the significance and justification of
implementing pile integrity testing