Cement CEM Research Articles

THE IMPACT OF RECYCLED FINE AGGREGATE ON SELECTED PROPERTIES OF CONCRETE

The use of recycled fine aggregate in the production of concrete mixes is one of the elements of a circular economy. However, it is important to ensure that such a modification does not significantly affect the durability of the produced concrete elements. One possible criterion to check whether this condition is met is the practical application of the concept of equivalent concrete properties. The presented studies analyzed the properties of concrete with multi-component cement CEM V/A (S-V) and with recycled fine aggregate. The conducted analyses of the research results showed that with a 15% replacement level of natural sand with recycled sand, it is possible to maintain durability characteristics compared to concrete using only natural sand.

Increasing the reliability of oil and gas well fastening with polycomponent plugging systems

Purpose. Development of effective composite plugging systems for reliable fastening of oil and gas wells in difficult mining-geological conditions of deposits of Ukraine. Methods. The proposed research is based on an analytical and industrial study of the problems of the well construction and fastening in the conditions of chemogenic deposit occurrence when applying the analysis of geophysical research materials. The research of tamponage solutions and buffer liquids was carried out using standard devices and methods that meet the set of requirements for testing cements and technological systems for well construction. Processing of research results was carried out in MATHSAD and EXCEL. Composite cement CEM V according to the European standard EN 197-1, tamponage cement 1-G, krents - high-basic C2F CaSO4 and low-basic 3(CF) CaSO4 calcium sulfoferites were used for the research. Findings. It was established that the basic plugging material, as well as technological solutions for fastening wells in difficult mining-geological conditions, do not ensure compliance of the well as an engineering structure with operational reliability indicators. As a result, violations in the fastening system are quite often recorded, which require significant time and financial costs for their elimination, and sometimes lead to well liquidation. In order to increase the reliability of fastening wells, it is necessary to use multi-component tamponade systems modified by krents. Calcium sulfoferrite admixtures have been proved to accelerate the kinetics of early strength and contribute to the formation of cement stone with improved characteristics. The need to use effective buffer systems to improve the quality of fastening is substantiated. Originality. On the basis of assessment, systematization and detailed study of geophysical material and features of well fastening under the conditions of exposure to chemogenic sediments, the necessity of using composite plugging material was established. The conducted studies have proved that to ensure reliable fastening of wells in difficult mining-geological conditions, it is necessary to use multicomponent composite plugging material modified by calcium sulfoferites with accelerated kinetics of early strength, which form cement stone with a densely packed structure. Practical implications. Based on the industrial material evaluation and detailed laboratory studies, technological solutions have been developed to increase the reliability of well fastening due to the introduction of multi-component composite plugging material modified by krents and buffer liquids.

Shrinkage and Creep Properties of Low-Carbon Hybrid Cement.

Hybrid cements combine clinker with large amount of supplementary cementitious materials while utilizing hydration and alkali activation processes. This paper summarizes shrinkage and creep properties of industrially produced H-cement, containing only 20% of Portland clinker. In comparison with a reference cement CEM II/B-S 32.5 R, autogenous shrinkage is smaller after 7 days, and drying shrinkage is similar at similar times. A different capillary system of H-cement leads to faster water mass loss during drying. Basic and total creep of concrete remains in the standard deviation of B4 and EC2 creep models. The results demonstrate that shrinkage and creep properties of concrete made from H-cement have similar behavior as conventional structural concrete or high-volume fly ash concrete.

Perspective of concrete with Portland composite cement CEM II/C-M (S-LL)

Perspective of concrete with Portland composite cement CEM II/C-M (S-LL)

Effect of nano-silica on the flexural behavior and mechanical properties of self-compacted high-performance concrete (SCHPC) produced by cement CEM II/A-P (experimental and numerical study)

The extensive use of cement exacerbates the greenhouse effect by increasing carbon dioxide (CO2) emissions. So, many standards recommend using Portland-composite cement in construction as one of the methods for reducing CO2 emissions, especially cement CEM II/A-P. This paper presents an extensive experimental and numerical study to investigate the effect of micro and nano-silica on the flexural behavior and mechanical properties of Self-Compacted High-Performance Concrete (SCHPC) produced by cement CEM II/A-P. The extensive experimental work consisted of eight mixtures: three with micro-silica (MS), four with nano-silica (NS), and a reference mixture without silica. For both MS and NS, different percentages of adding or replacement content were tested to study their effect on the following: (a) the workability of fresh concrete, (b) concrete compressive strength, (c) splitting tensile strength, (d) flexural behavior including flexural tensile strength, and (e) the optimum percentage of each of the MS and NS to get the maximum structural and economic benefits of using for SCHPC with CEM II/A-P. Also, through a statistical program, these experimental results were used to obtain accurate formulae that could predict both the splitting tensile strength (fsp) and modulus of rupture (fctr) for SCHPC with adding nano-silica. In addition, the numerical study verified the experimental results based on the finite element program ANSYS. The flexure behavior of SCHPC beams is verified using the Microplane model (recently added to ANSYS). The experimental results showed that adding NS is more effective than replacing or adding MS for SCHPC mixture with CEM II/A-P to increase the concrete compressive strength, splitting tensile strength, and flexural tensile strength, especially for the mixture with adding NS content of 4 %. The numerical results showed the ability of the coupled damage-plasticity microplane model to simulate the flexural behavior of the tested SCHPC beams with MS or NS well. This research confirms nano-silica's structural and economical efficiency in the behavior of SCHPC beams. It was found that the optimum percentage of adding NS is 4 % for SCHPC mixtures with CEM II/A-P.

Investigation of Materials for Enhanced Vibrational Insulation in Ground Structures Using Concrete Mixtures: A Case Study of Rubber Aggregate Addition.

The reduction of vibrations in concrete has been a topic of discussion among scientists. This article presents research on designing concrete mixes for constructing ground barriers with enhanced vibration isolation using waste materials. This study discusses the design of concrete mixes for the construction of concrete partitions with increased vibration isolation, using the polish standards. The experiments were conducted at the Laboratory of Building Materials Engineering at the Cracow University of Technology as part of the project entitled "Innovative construction of vibration-insulating barriers to protect the environment from transport vibrations and similar sources". The concrete composition utilized blast furnace cement CEM III/A 42.5 N, with mineral and chemical additives. Recycled rubber aggregate from used tires was employed to enhance vibration isolation. Measurement results demonstrated the effectiveness of the concrete in dampening vibrations, confirming its suitability for practical use.

Environmental and technical assessment on the application of slate waste in Portland-composite cement CEM II

Large volumes of waste are generated from the manufacture of slabs, roofing, and tiles using slate stone. The use of waste in the construction industry is prevalent due to the environmental advantages associated with the implementation of circular economy standards. This paper examines the production of Portland cement CEM II using heat-treated slate waste. The fineness index results were 10.95 % for the 75-μm sieve and 23.53 % for the 45-μm sieve. Assessment of reactivity using mechanical methods showed that mortars produced with 20 % slate waste (SW) achieved a strength of 42.35 MPa and a mechanical index of 84.93 %. Direct measurement (FTIR), along with chemical methods (Frattini Test and Saturated lime test), confirm the pozzolanic activity of the slate waste. The environmental impact assessment demonstrated a reduction in the carbon dioxide emission rate by 21.49 % (6.54E+02 kgCO2-eq/t) with the use of Portland cement CEM II/CSW. The valorization of slate waste can contribute to the availability of an alternative source of raw material and the reduction of natural resource consumption. However, further studies on mechanical performance and durability are necessary for this waste to be applied in structural cementitious matrices.

CEMENTITIOUS SYSTEMS FOR HIGH-PERFORMANCE CONCRETES WITH IMPROVED CORROSION RESISTANCE

The article presents the results of research on cementitious systems "Portland cement CEM I 42,5 R - active mineral additives - microfillers - superplasticizer - hardening accelerators" for high-performance concrete with improved corrosion resistance. The resistance of concrete to corrosion caused by the influence of chemical substances was investigated - sulfate corrosion (class XA), which combines the processes of formation and accumulation of sparingly soluble salts in concrete, which are accompanied by internal stresses and destructive phenomena in concrete. The increase in corrosion resistance of high-performance concretes based on modified cementitious systems is explained mainly by the creation of a fine-crystalline microstructure with the formation of C-S-H phases, which contribute to the pores colmatation with age of hardening.

Mechanical properties of cement pastes containing plasma-treated silicon-based materials

The study delves into the impact of waste silicon-based materials on the mechanical characteristics of the resulting cement pastes. The investigation uses Portland cement CEM I 42.5R in conjunction with silicon-based waste materials sourced from the packaging industry, specifically from Recifa, a.s. Variations between the sample groups arise from differences in the concentration of silicon-based materials and the method of surface treatment. The inquiry seeks to assess the effects of two distinct levels of Si-based material incorporation, namely 10 wt. % and 20 wt. %, along with plasma treatment involving two different gases: oxygen (O2) and hydrogen (H2). The mechanical attributes under scrutiny encompass compressive and flexural strengths. The evaluation of mechanical properties is carried out on samples aged 28 days, with dimensions measuring 20 × 20 × 100 mm.

Experimental and operations viability assessment of powder-to-powder (P2P) mixture of graphene and cement for industrial applications

Studies have demonstrated that a minute quantity of graphene is sufficient to boost cement characteristics, but the attainment of good dispersion and uniformity of the resultant graphene-cement mixture remains a challenge. To alleviate these challenges, this study proposes a low-energy powder-to-powder homogeniser for dispersing reasonably large quantities of graphene powder into cement powders. Microscopic analysis of graphene dispersion from two samples (1% and 0.02% graphene) at 5x, 10x and 20x objectives revealed that graphene accounts for 1.3% and 0.09% over the cement area respectively, which is relatively uniform across all selected samples. Furthermore, four different dosages of graphene were used to validate the impacts of various proportions of graphene, i.e., 0%, 0.02%, 0.04% and 0.06% (by mass of cement) on two types of cement (i.e., Portland cement CEM I 52.5 N and Portland cement CEM II 42.5 N) which also revealed compressive strength increases up to 25% at 7 and 28 days.

Experimental Investigation and Classification of Wastewater Treatment Sludge as Pozzolan for Cement

This paper presents an investigation conducted to evaluate wastewater treatment sludge for potential use as a cement extender or pozzolan. Two varieties comprising the digested wastewater sludge (DWWS) and activated wastewater sludge (AWWS) materials, were finely ground then calcined at 750 °C for 30 min. Subsequently, the calcined sludge waste materials were blended with ordinary Portland cement CEM I 52.5 N at 0, 10, 20, 30% DWWS or AWWS, and used to prepare mortar mixtures at proportions of 1:3:0.61 cement to sand to water. Various tests were conducted including workability, compressive strength, pozzolanic activity with lime, drying shrinkage and alkali-silica reaction. It was found that both varieties of the sludge waste materials, once blended with CEM I at 20% DWWS or 20% AWWS, satisfied the ASTM C618 criteria for Class C pozzolan, and may be classified as CEM II /A-P 32.5 N,R cement type of EN 197-1/SANS 50197-1. The overall performance of DWWS was relatively better than that of AWWS.

The Influence of Corrosion Processes on the Degradation of Concrete Cover.

In this work, two methods were used to accelerate the corrosion of concrete. In the first method, chloride ions were injected into the concrete using the migration method. The moment of the initiation of the corrosion process was monitored using an electrochemical method of measuring polarization resistance. In the next step, the corrosion process was accelerated by the electrolysis process. Changes on the sample surface were also monitored using a camera. In the second method, the corrosion process of the reinforcing bar was initiated by the use of the electrolysis process only. Here, changes occurring on the surfaces of the tested sample were recorded using two web cameras placed on planes perpendicular to each other. Continuous measurement of the current flowing through the system was carried out in both cases. It was assumed that in conditions of natural corrosion, a crack would occur when the sum of the mass loss of the reinforcing bar due to corrosion reached the same value in tcr(real) (real time) as it reached in the tcr (time of cracking) during the accelerated corrosion test. The real time value was estimated for C1 concrete with cement CEM I. The estimated value was tcr(real) = 1.1 years and for C2 concrete with cement CEM III, tcr(real) = 11.2 years. However, the main difference that was observed during the tests was the nature of the concrete cracks. In the case of the C1 concrete sample, these occurred along the reinforcing bar, while in the C2 concrete, the failures occurred on a perpendicular plane transverse to the direction of the reinforcing bar.

DURABILITY OF RIGID PAVEMENT CONCRETE REINFORCED WITH BASALT FIBER

The purpose of the work is the development of fiber-reinforced concrete compositions for rigid pavements with properties of high strength, frost resistance and wear resistance due to the use of polycarboxylate type superplasticizer and dispersed reinforcement. The experiments were conducted according to an optimal 3-factor 15-point plan. The following composition factors were varied: the amount of Portland cement CEM I 42.5 R (from 290 to 350 kg/m3); the amount of basalt fiber BAUCON®-bazalt (from 0.9 to 1.5 kg/m3); the amount of polycarboxylate superplasticizer STACHEMENT 2570/5/G (from 0.6 to 1 % by weight of cement). The workability of all developed mixtures was S1, which corresponded to a cone slump 2...3 cm. Research results shows when increasing the amount of cement and the amount of superplasticizer to 0.9 – 1.0 %, the W/C of the mixtures decreases. The amount of basalt fiber practically does not affect the W/C of the mixture. Due to increase in the amount of Portland cement, the strength of fiber-reinforced concrete is increases, as expected. With an increase in the amount of basalt fiber to 1.3 – 1.4 kg/m3, the tensile strength in bending of concrete increases by 12 – 21 %, while the compressive strength changes insignificantly. Fiber concrete with a superplasticizer content of about 0.9 % has the highest compressive and tensile strength in bending. Moreover, due to increase in the amount of Portland cement from 290 to 350 kg/m3, the frost resistance of concrete increases to about 100 cycles. Due to the increase in strength of that composition, the wear resistance of concrete was increased. With an increase in the amount of basalt fiber from 0.9 to 1.3 – 1.4 kg/m3, the wear resistance of concrete increases by 11 – 16 %, and frost resistance increases to approximately 50 cycles. The change in the amount of superplasticizer has little effect on the wear resistance of concrete. However, with an increase in the amount of additive STACHEMENT 2570/5/G from 0.6 to 0.9 % by weight of cement, the frost resistance of fiber-reinforced concrete increases to about 50 cycles. Fiber concretes with a rational amount of dispersed reinforcement (1.3 – 1.4 kg/m3) and superplasticizer (0.9 %), depending on the amount of cement, have compressive strength from 43 to 60 MPa; tensile strength in bending from 4.9 to 6.4 MPa; wear resistance from 0.31 to 0.37 g/cm2 and frost resistance from F200 to F300. This ensures the high durability of the developed fiber-reinforced concrete for rigid pavements.

Investigations on the Suitability of Alternative and Supplementary Cementitious Materials to produce High Performance Aerogel Concrete

AbstractHigh Performance Aerogel Concretes (HPAC) are produced by embedding silica aerogels in high‐performance matrices, which were previously based on finely ground Portland cement CEM I 52.5 R and microsilica. On the one hand, this ensured a comparatively high compressive strength, but on the other hand it was associated with large shrinkage strains and a high global warming potential (GWP). In the following, approaches are presented on how these disadvantages can be counteracted by replacing Portland cement with alternative (ACM) or supplementary cementitious materials (SCM). In the experimental investigations, calcium aluminate cement, calcium sulfoaluminate cement, calcium sulfoaluminate belite cement and a CSH phase binder were used as ACMs; limestone powder, calcined clay, fly ash, glass powder, rice husk ash, brick dust and ground granulated blast‐furnace slag were used as SCMs. Based on extensive fresh and hardened concrete tests, it could be shown that with the (partial) replacement of Portland cement by ACMs or SCMs, High Performance Aerogel Concretes can be produced that have significantly reduced shrinkage deformations and a lower GWP with an unchanged good relationship between compressive strength and thermal conductivity.

MECHANICALS PROPERTIES OF MORTARS BASED ON GLASS WASTE AS A PARTIAL REPLACEMENT FOR CEMENT

The various activities of man continuously generate countless quantities of waste (plastics, glass, wood, domestic waste, etc.), a significant proportion of which inevitably ends up in inappropriate landfill sites. Since the beginning of the 21st century, many materials have been recycled. The present study is part of this recycling effort, with the aim of using construction waste to reduce the environmental footprint of cement. An experimental campaign was carried out to assess the effect on the physico-mechanical properties of mortars to which recovered and finely ground glass powder was added. Cement CEM II 32.5 R was substituted by glass powder in proportions of 5, 10, 15 and 20 %. The water/cement ratio was set at 0.26 to ensure consistency and set time, while a W/C ratio of 0.5 was used for the manufacture of mortars subjected to compression and bending tests. The results were compared with those obtained with the reference mortar. Maximum optimum strength was obtained at a dosage of 20 %. These comparisons show that the addition of glass powder has a beneficial effect on the mechanical and physical characteristics of the various mortars studied. This is a promising application for this waste, which still needs to be confirmed by further testing.

Comparative Study of Mortars Made with Sands of Different Geological Origin

The present work is a comparative study of sand mortars from various geological origins to highlight their influence on mortar qualities. Five different sands and the cement CEM II/B–P 42.5R were used to produce mortars with similar water/cement ratios (W/C). These are the “Sanaga” sand from the Sanaga River, the “Wouri” sand from the Wouri River, the Nyambaka basalt sand, the Meiganga granite sand, and the Leboudi gneiss sand. The physical, chemical, and mineralogical features of these sands were used to characterize and classify them. They were then used to formulate mortars, which were analyzed and compared. According to the results of the mortar setting time tests, the initial setting time ranges from 195 minutes for Sanaga sand mortar (MS04) to 210 minutes for gneiss sand mortar (MGN03), passing Wouri sand mortar (MW05) with 200 minutes, basalt sand mortar (MB01) with 198 minutes, and granite sand mortar (MGR02) with 196 minutes. The final setting time ranged from 496 minutes (MGR02) to 510 minutes (MGN03), with an average of 300 minutes added to the initial setting time. The flexural strength tests of the mortars reveal that crushed sands outperform alluvial sands. They range from 1.64 to 2.18 MPa after 2 days, 3 to 3.90 MPa after 7 days, and 7 to 14.84 MPa after 28 days. The results of the compressive strength tests show that quarry sand mortars have greater average compressive strengths than alluvial sand mortars, with basalt sand providing the greatest performance. These strengths range from 6.35 to 10.83 MPa after 2 days, 7.55 to 18.96 MPa after 7 days, and 22.81 to 34.58 MPa after 28 days, with the MB01 being the best sand. These findings reveal that the geological origin of sands, which specifies certain of their physicochemical and mineralogical attributes, has an impact on the properties of mortars. This impact is also influenced by granulometry and organic matter concentration.

Physico-Mechanical and Durability Characterization of Eco-Ternary Cementitious Binder Containing Calcined Clay/Rice Husk Ash and Recycled Glass Powder.

The objective of this study is to determine the influence of recycled glass powder (GP) on the physico-mechanical behavior and durability of a ternary cementitious binder containing calcined clay_metakaolin (MK) or rice husk ash (RHA). Different mortars were produced and characterized in fresh and hardened states. Reference mortars were produced using 100% cement CEM II/B-L 42.5R and 70% CEM + 30% MK or RHA. Test mortars were produced with the substitution of the MK or RHA with the GP and keeping the rate of the substitution at 30%; i.e., in ratios of 20:10, 15:15, and 20:10 of MK/RHA:GP. The water/binder weight ratio was maintained at 0.5, and the consistency of all mortars was adjusted using an admixture (superplasticizer/binder weight ratio of 0.75%). The substitution of MK and RHA with GP reduces the water demand to achieve the normal consistency of pastes and therefore increases the workability of mortars containing both binders CEM+MK+GP and CEM+RHA+GP. The substitution of MK and RHA with GP slightly reduces the compressive strength for both binders. The water-accessible porosity slightly increases for the substitution of MK and reduces for the substitution of RHA with GP. The mass losses after acid attack slightly increase with the substitution with GP, lower for the MK than the RHA up to 15% GP, but it remained far below that of 100% CEM. The results show that the substitution of MK and RHA with GP can improve the physical properties and durability of the mortars compared with that of 100% CEM, but it slightly decreases the mechanical properties due to the low rate of the pozzolanic reactivity of the GP. Further studies should seek to understand the reactivity behavior of the GP at the microstructure scale and therefore improve the mechanical performance of GP based mortar.

Influence of the Amount of Conductive Component on the Electrical Resistivity of Fine-Grained Electrically Conductive Concrete

Approaches to the production of electrically conductive concrete and the possibility of its application through the use of electrical properties in various industries are considered. The results of testing the compositions of fine-grained self-compacting concrete based on Portland cement CEM I 52.5 N, sand with a size modulus Mk=2.43 and polycarboxylate plasticizer for changes in electrical resistivity during hardening are presented. The increase in specific electrical conductivity was provided by the introduction of conductive components in various quantities, such as construction soot, carbon black K-354, graphite EUT-2. The positive effect of increasing the amount of the conductive component on the electrical resistivity for 28 days of normal hardening of the samples and on the ability to resistive heating by changing the surface temperature of the samples when passing a direct current with a voltage of 30 V. is shown.

Using of Limestone Cement in Fibre-Cement Corrugated Sheets Production

The paper deals with the production of fibre-cement and the use of limestone cement in its production. The paper describes the basic properties of final products, the basic raw materials and the Hatschek production technology used for the production of corrugated sheets. The attention is paid especially to the wet part of the production when describing the production process. The emphasis was mainly placed on the preparation of fibre-cement slurry and the gradual formation of a layer of fibre-cement on the surface of the cylindrical sieve. The paper describes the possible use of limestone cement in the production of corrugated sheets. Trial recipes were designed with using limestone cement CEM II with and without separately dosed limestone. The fibre-cement corrugated sheets were produced with using Hatschek technology. Mainly was investigated the influence of limestone dosing on the strength characteristics and the volume weight of the final products. The produced sheets were tested according to EN 494+A1: 2016 Fibre-cement profiled sheets and fittings - Product specification and test methods. The tested samples reached comparable results like sheets produced according to standard recipe. No negative effect on the strength characteristics of final products was proven between the standard and the trial recipes.

Stabilization of Chromium Waste by Solidification into Cement Composites.

This article deals with the study of hazardous chromium leaching, stabilized/solidified by cement CEM II after 28 days of curing, in an acidic environment. The mortars subjected to this study were investigated by X-ray diffraction (XRD) characterization to evaluate the influence of chromium waste on their mineralogical structure. In the study range (0.6-1.2%), increasing the mass percentage of Cr2O3 in the mortars indicates that chromium accelerates the hydration process and setting of the mortar and increases the mechanical strength of the mortars compared to the control sample. It was observed that the release of chromium during the Toxicity Characteristic Leaching Procedure (TCLP) test and the efficiency of the stabilization/solidification process depended on the initial Cr concentration and the leaching time. The use of XRD allowed the identification of new crystallized phases in the cement matrices, namely, CaCrO4·2H2O and chromium-ettringite Ca6Cr2(SO4)3(OH)12·26H2O, which confirms the immobilization of chromium and the efficiency of the stabilization/solidification process. In this research, the release mechanism was found to be primarily a surface phenomenon by modeling the experimental data (dissolution or precipitation).