Cement Systems Research Articles

Potential applicability of calcium phosphate modified portland cement paste for geologic sequestration of CO2

In order to increase the integrity of the wellbore which is used to prevent the leakage of supercritical CO2, it is necessary to develop a concrete that is strongly resistant to carbonation. In an environment where the concentration of CO2 is exceptionally high, Ca2+ concentration in portland cement concrete drops significantly due to the rapid consumption of calcium hydroxide, which decreases the stability of the calcium silicate hydrate. In this work, it is hypothesized that if fairly large quantity of the hydration product becomes more thermodynamically stable than calcite, the damage caused by rapid carbonation will certainly be minimized. For this purpose, portland cement system was modified by monocalcium, dicalcium and tricalcium phosphates to produce hydroxyapatite in portland cement paste. According to the experimental results, addition of calcium phosphate produced hydroxyapatite. Among three different calcium phosphates, monocalcium phosphate showed the most significant impact on hydration. It caused faster stiffening and delayed calcium silicate hydration. Although cement pastes modified by calcium phosphates showed less compressive strength than plain cement paste, they showed an excellent durability after exposure to supercritical CO2. It is clear from the results that the potential applicability of calcium phosphate modification in portland cement for geologic sequestration of CO2 was successfully proven.

Impact of Calcined Natural Clinoptilolite Zeolite on Hydration Kinetics and Shrinkage of Cementitious Materials

Abstract Previous literature has provided contradictory results, so we present the current investigation to provide additional information to assess the suitability of using soak calcination as a pretreatment method to increase the performance of calcined zeolite when used as the supplementary cementitious material. In this study, natural clinoptilolite zeolite was calcined for three hours at 200°C, 400°C, 600°C, 800°C, and 1,000°C, and the effects of calcination on different physical and chemical properties were observed using a range of experimental tests. The impacts of calcined zeolite were investigated in the hydrated system with the replacement of portland cement up to 20 % by mass on hydration kinetics (i.e., heat of hydration, setting time, chemical shrinkage, degree of hydration), drying shrinkage, and compressive strength. Results revealed that calcination minorly decreased the crystallinity, particle size, and peak pore size of the zeolite, leading to a slightly increased external specific surface area, whereas it increased the rate of moisture absorption and pH of zeolite particles. In the hydrated cementitious system, calcined zeolite reduced the workability and heat of hydration and retarded the initial setting time. The calcined zeolite particles absorbed a part of the water from the fresh mixture and expanded volumetrically, which led to a negative volume of chemical shrinkage up to the final setting time and increased the drying shrinkage. As the dosages of calcined zeolite increased, the compressive strength substantially decreased because of the lower degree of hydration. Overall, soak calcination pretreatment decreased the reactivity of clinoptilolite zeolite particles and impacted the performance of calcined zeolite in the blended system.

Basic oxygen furnace (BOF) slag as an additive in sodium carbonate-activated slag cements

Basic oxygen furnace slag (BOFS) is a high-volume waste resulting from the production of steel from pig iron. Due to its high free lime content, BOFS is difficult to recycle and/or include into conventional cement systems. Alkali-activation technology offers a pathway to transform industrial wastes such as BOFS into low-carbon cements. Alternative precursors for cement systems are needed as the reliance on commonly used materials like ground granulated blast furnace slag (GGBFS) is becoming unsustainable due to decreasing availability. This study investigates alkali-activated cements incorporating 20 and 30 wt.% of naturally weathered BOFS as a replacement for GGBFS, in both sodium silicate- and sodium carbonate-activated systems. A fraction of BOFS subject to mechanical activation is compared against the untreated BOFS in the 20 wt.% systems. It is observed that in naturally weathered BOFS, a significant portion of the free-lime is found to convert to portlandite, which accelerates alkali-activation kinetics. In sodium silicate-activated systems, the high pH of the activator results in incomplete reaction of the portlandite present in BOFS. The sodium carbonate-activated system shows near complete conversion of portlandite, causing an acceleration in the kinetics of reaction, setting, and hardening. These findings confirm the viability of sodium carbonate activated GGBFS-based systems with only a minor loss in strength properties. BOFS can be utilised as a valuable cement additive for the production of sustainable alkali-activated cements utilising sodium carbonate as a less carbon-intensive activator solution than the more commonly used sodium silicate. Mechanical activation of BOFS offers further optimisation potential for alkali-activation.

Closed wellbore integrity failure induced by casing corrosion based on solid-chemical coupling model in CO2 sequestration

The safety and stability of carbon sequestration are key in CCS technology, and the wellbore is a critical pathway for leakage, which can lead to the failure of sequestration. In this study, the process of casing corrosion-induced closed wellbore integrity failure is investigated based on a solid-chemical coupling model. The influence of temperature and CO2 pressure on the development of cement damage is also investigated. The results show that the corrosion rate increases and then decreases with increasing depth, and the time of damage initiation gradually shifts backward. During the process of casing corrosion-induced cement damage, the corrosion scale that accumulates on the surface of the casing causes stress redistribution within the cement system. The damage initiates at the interface between the bottom of the cement system and the casing, progressing upwards to create a potential leakage pathway. Moreover, the damage in the cement sheath develops more rapidly, while the rate of damage development in the cement plug gradually decreases. This study will be helpful for understanding the initial stage of closed wellbore failure in carbon sequestration and for implementing corresponding preventive measures in engineering practice.

Study on the composite compatibility and interfacial properties of excess sulfate phosphogypsum cementing system to OPC and C[formula omitted]A

Releasable sulfate contained in the Excess Sulfate Phosphogypsum Cementing System (ESPCS) potentially degrades interfaces when contacted with conventional cements, raising incompatibility concerns. This work evaluated fresh connection, adhesion, and aggregate embedment of ESPCS to ordinary Portland cement (OPC) and Calcium sulfoaluminate cement (CS¯A), with mechanical and interfacial properties studied. Results indicate the discrepancy in hydration properties gives Excess-sulfate Phosphogypsum Slag Cement (EPSC) uncoordinated expansion to OPC, followed by cracks (95 μm) generation. Meanwhile, expansive ettringite forms in the interface due to bleeding sulfate-rich water concentration, thus leaving a porous contact zone (1240 μm, 11.29%) and resultant flexural strength reduction of OPC-EPSC mortar (by > 36%). Conversely, EPSC and CS¯A are close in phase assemblages, resulting in compact interface and higher bond strength. Incorporating the Phosphogypsum-based Cold Bonded Aggregates (PCBAs) into OPC induces the interfacial ettringite formation-sulfate attack by internal curing water, yielding the worst composite performance, i.e., the lowest 360 d compressive strength (38.8 MPa) of concrete OPCC, lower than EPSCC (48.6 MPa) and CS¯AC (50.3 MPa). ESPCS is more compatible to CS¯A than OPC which is advised against exposing directly with ESPCS. This work helps specify composite feasibility and conditions of ESPCS with typical cement composites.

A multi-performance comparison between lime, cementitious and alkali-activated TRM systems: Mechanical, environmental and energy perspectives

The combined need to propose new solutions for the structural reinforcement of existing buildings and for the reduction of CO2 emissions is leading to the development of more sustainable composite materials, such as those based on alkali-activated mortars (AAM). In this study, different formulations of AAM, based on metakaolin or fly ash, have been evaluated as possible matrices for Textile Reinforced Mortar (TRM) systems. Two different bidirectional textiles, made of AR glass or basalt fibers, were used as internal reinforcement. The physical-mechanical properties of TRM systems based on AAM were evaluated and compared with those of commercial systems with cementitious or lime-based matrices. Direct tensile tests on TRM coupons and shear bond tests on clay brick substrates were carried out. Then, their energy and environmental-related performance have been compared. Results showed that alkali-activated matrices can be very promising and eco-friendly alternative solutions to traditional mortars in TRM systems.

Feasibility of using calcined clays and reclaimed coal ashes in binary and ternary cementitious systems

This study evaluates the feasibility of using three different calcined clays (CCs) to partially replace ordinary Portland cement (OPC) in concretes. Furthermore, the best performing CC was investigated in conjunction with the addition of reclaimed fly ash (RFA) or reclaimed ground bottom ash (GBA) to partially replace OPC. OPC replacement levels by mass considered in the present study for both binary (i.e., OPC + CCs) and ternary (i.e., OPC + CC + GBA or RFA) cementitious systems were 10, 20, and 30 %. It was shown that, relative to the control mixture (CO), the utilization of CCs can significantly improve properties of the hardened concrete, at the cost of significantly reducing the workability of fresh concrete mixtures. Conversely, the incorporation of coal ashes to form ternary system produced concretes with superior hardened properties (relative to CO) while partially mitigating workability loss. Overall, both binary and ternary systems can produce concretes with significantly higher strength and surface resistivity. Additionally, characteristics of CCs that could be used as rapid indicators to predict their performance as supplementary cementitious materials (SCMs) in concrete were identified by coupling materials characterization techniques and concrete test results.

Reconstruction of mechanical leg axis using non-modular cemented hinged prosthesis in complex primary total knee arthroplasty.

Modular cementless knee arthroplasty systems are capable of precise reconstruction of the mechanical axis. However, they are considered more susceptible to complications. In contrast, non-modular cemented systems are said to be more forgiving and show good long-term results. The aim of this study was to investigate the resulting leg axis after implantation of a non-modular cemented rotating hinged knee prosthesis. Furthermore, potential risk factors for the occurrence of malalignment and complications should be identified. Between 2005 and 2015, 115 patients could be included in this monocentric retrospective cohort study. All patients underwent primary hinged non-modular cemented total knee arthroplasty. Preoperative and postoperative standardized long radiographs were analysed to determine resulting leg axis. Furthermore, epidemiological and intraoperative data as well as perioperative complications were surveyed. Average leg axis was 5.8° varus preoperatively and 0.6° valgus postoperatively. Considering an axis deviation of 3° as the target corridor, 27% of all cases examined were outside the desired range. 21% cases showed a femoral deviation from the target corridor and 15% showed a tibial deviation. There was a significant relationship between the preoperative mLDFA and the mechanical alignment of the femoral component (R = 0.396, p < 0.001) as well as between the preoperative mMPTA and the mechanical alignment of the tibial component (R = 0.187, p = 0.045). The mean operative duration was 96min. No periprosthetic fractures were observed within the study cohort. The main result of the present work is that a non-modular cemented rotating hinged knee arthroplasty system can reconstruct the mechanical leg axis precisely and comparable to modular cementless and unconstrained total knee prostheses. Component malalignment is primarily dependent upon extraarticular deformity preoperatively. Periprosthetic fracture rates and duration of surgery were lower compared with current literature. Level III: Retrospective cohort study.

Study on the Influence of Waste Rock Wool on the Properties of Cement Mortar under the Dual Fiber Effect of Polyvinyl Alcohol Fibers and Steel Fibers.

In this paper, the effect of waste rock-wool dosage on the workability, mechanical strength, abrasion resistance, toughness and hydration products of PVA and steel fiber-reinforced mortars was investigated. The results showed that the fluidity of the mortar gradually decreased with the increase in the dosage of waste rock wool, with a maximum reduction of 10% at a dosage of 20%. The higher the dosage of waste rock wool, the greater the reduction in compressive strength. The effect of waste rock wool on strength reduction decreases with increasing age. When the dosage of waste rock wool was 10%, the 28 days of flexural and compressive strengths were reduced by 4.73% and 10.59%, respectively. As the dosage of waste rock wool increased, the flexural-to-compressive ratio increased, and at 20%, the maximum value of 28 days of flexural-to-compressive ratio was 0.210, which was increased by 28.05%. At a 5% dosage, the abraded volume was reduced from 500 mm3 to 376 mm3-a reduction of 24.8%. Waste rock wool only affects the hydration process and does not cause a change in the type of hydration products. It promotes the hydration of the cementitious material system at low dosages and exhibits an inhibitory effect at high dosages.

Multi-objective optimization of cement-based systems containing marine dredged sediment

This study presents the integrated use of particle packing methodology and response surface methodology as an innovative mixture design for developing eco-friendly cement-based systems containing marine dredged sediment. The objective was to reduce the sand and cement contents of mortar mixtures for island applications, while maintaining the same properties as a reference mixture. The study examined three input variables for mixture design and optimization: sediment-to-total sand ratio ranging from 0.1 to 0.4, water-to-binder ratio ranging from 0.4 to 0.5, and cement paste content ranging from 0.35 to 0.45. As a result, three mixtures were developed based on three optimization objectives: (1) maintaining the same fresh and hardened properties as the reference (110 mm spread flow and 49.5 MPa strength); (2) maximizing the reduction of cement and sand contents with the use of a superplasticizer; and (3) maximizing the durability (as measured with the bulk electrical resistivity). The optimal mixture proportions showed reduced sand and cement contents up to 38 % and 15 %, respectively, with mechanical properties comparable to that of the reference. Moreover, capillary absorption and drying shrinkage of the optimized mixtures were reduced compared to the reference by up to 36 % and 16.5 %, respectively. It was evidenced that the combined use of mixture design methods can significantly contribute to the development of cementitious systems with balanced eco-efficiency and properties.

Experimental investigation of the temperature-dependent dissolution process of aluminosilicate glass and low-calcium supplementary cementitious materials under alkaline conditions

High-temperature curing is commonly employed to promote the pozzolanic activity of supplementary cementitious materials (SCMs) in cementitious systems. Herein, the temperature-dependent dissolution processes of low-calcium SCMs and synthesised aluminosilicate glass were examined at pH 13 for cementitious systems. The dissolution rate and thermal activation energy (TAE) were estimated using nonlinear fitting and the Arrhenius equation. Experimental and analytical findings demonstrated that the TAEs of investigated SCMs and aluminosilicate glasses were temperature-dependent, decreasing with increasing temperature. Moreover, the TAE of aluminosilicate glasses increased with increasing Al/Si ratio, mainly due to the higher TAE of Al2O3 compared to SiO2. In addition, the TAE of fly ash was higher than that of investigated glass, largely because the Si and Al coordination numbers increased with decreasing cooling rates, according to molecular dynamics analysis. The topological TAE derived from molecular dynamics analysis is a promising parameter for estimating the TAE of aluminosilicate glass.

Comparison of eggshell powder blended cementitious materials with ASTM Type IL cement-based materials

The present study explores the potential of producing an alternative ASTM Type IL portland-limestone cement (PLC) using up to 20 % eggshell powder (ESP) by mass as crushed ESP is similar in chemical composition to limestone. To this aim, the hydration, durability, and mechanical properties of the ESP blended cementitious system (using ASTM Type I/II portland cement) are compared to a commercially available ASTM Type IL cement system containing approximately 10 % limestone. ESP was prepared by milling for 3 h upon drying. Characterization of the ESP was done by x-ray diffraction for phase analysis, scanning electron microscopy for microstructural observation, and laser diffraction analysis for particle size distribution. A range of experimental tests were undertaken on both the ASTM Type I/II cement replaced with ESP and the ASTM Type IL systems. Results revealed that the utilization of up to 20 % ESP enhanced the heat of hydration secondary peak (C3A) by increasing the aluminate phase kinetics in the blended system at a favorable pH pore solution. Also, an accelerating effect on the setting time (increased by 20–100 mins) was observed for ESP samples. Chemical shrinkage, compressive strength, and degree of hydration were similar between the ESP and PLC samples. Results also revealed that ESP particles were relatively more effective in minimizing drying shrinkage by 20–35 %, which is attributed to possible internal curing effects. Overall, 10 % ESP blended with ASTM Type I/II cementitious system was similar to the 10 % limestone containing PLC system and could be used as waste material in producing an alternative ASTM Type IL cement.

Effect of dispersion behavior of silica fume on the rheological properties and early hydration characteristics of ultra-high strength mortar

Silica fume plays a crucial role in ultra-high performance cementitious materials, but its dispersion, influenced by varying densification levels, leads to different degrees of agglomeration. However, the precise impact of this on rheological properties and early hydration characteristics of ultra-high performance cementitious materials remains unclear. This study assesses the impact of highly densified silica fume (HDSF), moderately densified silica fume (MDSF), and raw silica fume (RSF) on the rheological prperties of ultra-high strength mortar (UHSM). Additionally, the early hydration characteristics of UHSM influenced by these silica fumes are investigated through both heat of hydration and penetration resistance methods. The results showed that HDSF contained numerous large agglomerates, contrasting with MDSF and RSF, where the agglomerate sizes were comparable to those of cement particles. As the content of HDSF increased, the yield stress, viscosity, and thixotropy of UHSM gradually rose, accompanied by a notable decrease in hydration rate. Conversely, increasing MDSF and RSF content initially decreased and then increased these rheological properties, while the hydration rate remained relatively unchanged. The distribution behavior of the silica fumes influences the rheological properties of UHSM through water film thickness (particle spacing). Large agglomerates in HDSF reduce the activity of the entire cementitious system, significantly decreasing the hydration rate. In contrast, MDSF and RSF primarily influence the particle spacing within the cementitious system, subsequently impacting the hydration rate. This study provides theoretical insights and practical guidance for construction professionals in selecting appropriate silica fume for designing and regulating ultra-high performance cementitious materials performance.

Modelling of energy harvesting with bendable concrete and surface-mounted PVDF

Polyvinyl alcohol fiber reinforced engineered cementitious composite (ECC) using piezoelectric polymer film has attracted significant interest due to its energy harvesting potential. This work provides a theoretical model for evaluating the energy harvesting of bendable ECC using surface-mounted polyvinylidene fluoride (PVDF). In the mechanical part, concrete damage plasticity model based on the explicit dynamic analysis was utilized to simulate the dynamic flexural behavior of ECC beam under different dynamic loading rates. The mechanism of force transfer through the bond layer between the PVDF film and ECC specimen was simulated by a surface-surface sliding friction model wherein the PVDF film was simplified as shell element to reduce computational cost. Then, the electromechanical behavior of the piezoelectric film was simulated by a piezoelectric finite element model. A simplified model was also given for a quick calculation. The theoretical model was verified with the experimentally measured mechanical and electrical results from the literature. Finally, a parametric analysis of the effects of electromechanical parameters on the efficiency of energy harvesting was performed. The verified theoretical model can provide a useful tool for design and optimization of cementitious composite systems for energy harvesting application.

A Numerical Hydration Model to Predict the Macro and Micro Properties of Cement–Eggshell Powder Binary Blends

This study aims to propose a hydration kinetic model for the cement–eggshell powder binary system and predict the performance development of composite concrete through this model. The specific content and results of the model are as follows. First, based on the cumulative hydration heat of the cement and eggshell powder binary system in the first seven days, the parameters of the cement hydration model and the eggshell powder nucleation parameter are calibrated. These parameters remain constant regardless of the mix ratio. Secondly, the hydration heat of the cement–eggshell powder binary system over 28 days is calculated using the hydration model. The results show that at 28 days, for specimens with 0%, 7.5%, and 15% eggshell powder substitution, the cement hydration degrees are 0.832, 0.882, and 0.923, respectively. The hydration heat per gram of cement is 402.69, 426.88, and 446.73 J/g cement, respectively, while the hydration heat per gram of binder is 402.69, 394.86, and 379.72 J/g binder, respectively. Additionally, the hydration model is used to calculate the chemically bound water and calcium hydroxide content of the cement–eggshell powder binary system. At 28 days, for samples with 0%, 7.5%, and 15% eggshell powder, the chemically bound water content is 0.191, 0.188, and 0.180 g/g binder, respectively, and the calcium hydroxide content is 0.183, 0.179, and 0.173 g/g binder, respectively. Finally, a power function is used to regress the calculated hydration heat with experimentally measured compressive strength and surface electrical resistivity. The correlation coefficients for compressive strength and surface electrical resistivity are 0.8474 and 0.9714, respectively. This is because the strength weak point effect of eggshell powder has minimal impact on hydration heat and surface electrical resistivity experiments but significantly affects the strength experiment.

Characterization of Nanoparticles in Ethanolic Suspension Using Single Particle Inductively Coupled Plasma Mass Spectrometry: Application for Cementitious Systems.

Single particle inductively coupled plasma mass spectrometry (spICP-MS) is a well-established technique to characterize the size, particle number concentration (PNC), and elemental composition of engineered nanoparticles (NPs) and colloids in aqueous suspensions. However, a method capable of directly analyzing water-sensitive or highly reactive NPs in alcoholic suspension has not been reported yet. Here, we present a novel spICP-MS method for characterizing the main cement hydration product, i.e., calcium-silicate-hydrate (C-S-H) NPs, in ethanolic suspensions, responsible for cement strength. The method viability was tested on a wide range of NP compositions and sizes (i.e., from Au, SiO2, and Fe3O4 NP certified reference materials (CRMs) to synthetic C-S-H phases with known Ca/Si ratios and industrial cement hardening accelerators, X-Seed 100/500). Method validation includes comparisons to nanoparticle tracking analysis (NTA) and transmission/scanning electron microscopy (TEM/SEM). Results show that size distributions from spICP-MS were in good agreement with TEM and NTA for CRMs ≥ 51 nm and the synthetic C-S-H phases. The X-Seed samples showed significant differences in NP sizes depending on the elemental composition, i.e. CaO and SiO2 NPs were bigger than Al2O3 NPs. PNC via spICP-MS was successfully validated with an accuracy of 1 order of magnitude for CRMs and C-S-H phases. The spICP-MS Ca/Si ratios matched known ratios from synthetic C-S-H phases (0.6, 0.8, and 1.0). Overall, our method is applicable for the direct and element-specific quantification of fast nucleation and/or mineral formation processes characterizing NPs (ca. 50-1000 nm) in alcoholic suspensions.

Cementless Total Knee Arthroplasty: A State-of-the-Art Review.

» The demographic profile of candidates for total knee arthroplasty (TKA) is shifting toward younger and more active individuals.» While cemented fixation remains the gold standard in TKA, the interest is growing in exploring cementless fixation as a potentially more durable alternative.» Advances in manufacturing technologies are enhancing the prospects for superior long-term biological fixation.» Current research indicates that intermediate to long-term outcomes of modern cementless TKA designs are comparable with traditional cemented designs.» The selection of appropriate patients is critical to the success of cementless fixation techniques in TKA.» There is a need for high-quality research to better understand the potential differences and relative benefits of cemented vs. cementless TKA systems.

Role of Anionic Group of Methylallyl Ether-Based PCEs on Behavior of Cementitious Systems with Various C3A Contents

Role of Anionic Group of Methylallyl Ether-Based PCEs on Behavior of Cementitious Systems with Various C3A Contents

Research on the Performance and Application of a Low-Carbon Waste-Recycling Cement

This paper mainly introduces the history of the formation and development of an ultra-high performance low-carbon waste-utilizing cement (fast-setting and fast-hardening high-belite sulphoaluminate cement). This cement not only uses a large amount of solid waste (fly ash, blast furnace slag, industrial waste gypsum, alkali slag, etc.) as raw materials, and the waste utilization can reach 40%~95%, but also has a calcination temperature of 150~200℃ and 50 ℃ lower than that of traditional ordinary Portland cement and sulphoaluminate cement, and the carbon emission is equivalent to 30%~60% and 50%~80%. Through the elaboration of its main mineral composition, chemical composition, physical properties and action mechanism, the reasons for its excellent properties such as good whiteness, fast setting and hardening, high late strength, and small dimensional deformation are analyzed. And the application research is focused on the fields of inorganic flooring, airports, road quick repair, prefabricated walls, ultra-light and efficient A-level fire insulation, cement crafts, inorganic artificial stone, and UHPC ultra-high performance concrete. At present, there are many types of low-carbon cement in the world, including Porsol cement, Alinit cement, Celitement cement, Japanese eco-cement, multi-component high-mixture cement, high-belite cement, Anther cement, BCT cement, etc., but most of the products have a slow coagulation and hardening speed, and cannot meet the needs of rapid demolding, turnover, and traffic opening for mortar, concrete, cement products or pavements; at the same time, the production process is complicated and cumbersome, the later strength is low, the deformation is large, and the durability is poor. Therefore, in the actual promotion process in the engineering field, there are great difficulties and many constraints. Among them, Aether cement and BCT cement belong to the belite-sulfoaluminate cement system. Aether cement has 6h early strength performance. Compared with Portland cement (burning temperature1400~1500℃), it can significantly reduce production energy consumption, reduce CO2 emissions by 25%~30% per ton of cement, and the 28-day compressive strength reaches the strength level of standard cement (CEMⅠ52.5R); the size shrinkage of this concrete is less than 50% of that of OPC concrete, but its raw materials still use limestone, bauxite, gypsum, iron raw materials and marl raw materials, without effective utilization of bulk industrial waste, and CO2 emissions are far from meeting the low-carbon environmental protection requirements. BCT cement can be produced at a lower temperature (1250~1300℃), and its raw materials use industrial waste residues such as limestone, marl, fly ash and industrial by-product gypsum. CO2 emissions are 30% lower than traditional OPC cement clinker, but there is no early hourly strength, and the strength after 1~2 days is higher than that of ordinary Portland cement. This is far from the goal of using bulk industrial waste as raw materials to produce green, low-carbon, energy-saving and high-performance cement materials, which is currently widely used at home and abroad. At the same time, the above-mentioned low-carbon cement cannot effectively and reasonably control key indicators such as cement whiteness value, early strength before 4 hours, and dimensional change rate, and cannot meet the requirements of high-performance cement. At the same time, the production process is not mature and stable enough, and there is still a long way to go to meet the comprehensive popularization of production industrialization and promotion scale.

CONSTRUCTION AND OPERATIONAL PROPERTIES OF CONCRETE ON MODIFIED BINDER

The most important tasks of science in the field of construction: facilitating reinforced concrete structures, accelerating and reducing the cost of technological processes, in particular, abandoning heat treatment of products, increasing the durability of concrete can only be solved by giving special properties to binders. The way to solve this problem lies through the expansion of the range of complex mineral additives. Natural and man-made substances in a dispersed state, insoluble in water and characterized by grain size less than 0.16 mm, are used as mineral additives for binders and concretes. Despite the different effectiveness, mineral additives have a similar qualitative chemical composition (oxides of silicon, aluminum and others). The differences are in their mineralogical composition, the ratio of components and the degree of dispersion, which determine the predominant mechanism of their action in cement systems. Depending on the properties of the mineral additive, it is possible to obtain multicomponent binders for concretes with special properties: fast-hardening, high-strength, sulfate-resistant and others with significant savings in the cement component. The effectiveness of superplasticizers in dispersed systems can be increased due to a different procedure for their introduction or by combining them with finely ground mineral fillers of various chemical nature. The article presents the possibility of obtaining heavy concretes with specified construction and operational characteristics using a complex mineral additive, which includes waste from the tailings of the Balkhash mining and Processing plant and silica, as well as superplasticizers of various natures: MasterGlenium 305, Master Rheobuild 1000K and Master Air 200.