Cement Consumption Research Articles

Replacing fly ash with a natural pozzolan in normal strength concrete and ultra-high performance concrete

Fly ash is a widely-used supplementary cementitious material (SCM) in concrete. Common reasons for using fly ash in normal strength concrete (NSC) are to reduce cement consumption and mitigate alkali-silica reaction. Additionally, fly ash is being used in ultra-high performance concrete (UHPC) to reduce use of silica fume which is more expensive than fly ash. Fly ash and silica fume are important SCMs in UHPC that provide a dense microstructure, improving UHPC strength and durability. However, fly ash is becoming less available because the energy industry has been investing in renewable energy production and removing coal burning power plants from operation. Therefore, there is a need to identify sustainable SCMs to replace fly ash in NSC and UHPC mixtures. Natural pozzolans are a diverse class of siliceous or siliceous and aluminous materials that can form compounds possessing cementitious properties in the presence of water. Since natural pozzolans are easily mined, they are usually considered to be more sustainable than Portland cement and nearly as sustainable as other SCMs such as fly ash and silica fume. This experimental study evaluated the effects of a natural pozzolan (pumicite) as a potential replacement for fly ash that can produce comparable rheological and mechanical properties in NSC and UHPC mixtures. Results indicated that workability of both NSC and UHPC mixtures containing pumicite was consistent enough to achieve the targeted workability in just a few trials. Additionally, NSC mixtures with 30% pumicite had comparable compressive strength compared to NSC mixtures with 30% fly ash. Modulus of rupture (MOR) for NSC mixtures containing 30% pumicite (greater than 4.10 MPa) exceeded the MOR for specimens containing 30% fly ash. For UHPC mixtures, results showed that up to 75% of the fly ash in the control mixture could be replaced with pumicite while still producing acceptable compressive and flexural strengths. Based on these results, it appears that pumicite can be a reliable alternative for fly ash in NSC and UHPC mixtures in terms of rheological and mechanical properties.

Development of Self-Compacting Geopolymer Concrete Using Fayalite Slag Aggregates

Because of its high cement consumption, which limits its use in concrete construction, self-compacting concrete requires a higher cement content and various admixtures. Therefore, it is prudent to explore alternative options to minimize environmental impacts while creating environmentally friendly self-compacting concrete. This study examines the use of fly ash (FA) and ultrafine slag (UFS) in self-compacting geopolymer concrete (SGC), supplemented with fayalite slag aggregates (FSA). These aggregates, in varying quantities up to 60%, were used instead of traditional sand. The rheological properties and compressive strength of SGC were investigated. The analysis revealed that the addition of FSA improved the flowability of SGC. Notably, using a combination comprising 60% FSA, the largest slump measurement of 683.5 mm was achieved. Substituting up to 20% of FSA generally improved the properties of SGC at all ages. After one year, the mixture containing 20% FSA outperformed other compositions, with a maximum compressive strength of 49.38 MPa.

Changing the Technological Properties and Strength Characteristics of Highly Mobile Concrete by Introducing a Complex Modifier

The article considers the effect of a complex modifier consisting of a superplasticizer and cement crystallohydrates on the properties of cement dough, a highly mobile concrete mixture and heavy concrete obtained by hardening the mixture under normal conditions over a different period of time. As an additive of the superplasticizer, Relamix-PK was studied, administered in an amount of 0.6–0.8 wt. % of cement consumption. The authors investigated finely dispersed hydrated cement as additional crystallization centers. With the introduction of this complex modifier, the delamination of a highly mobile concrete mixture decreases (water separation – by 2 times, water separation – by 3.8 times). There is a significant acceleration of hardening in the initial periods of concrete hardening. Thus, in relation to the additive–free composition, the strength of concrete, which hardened for 1 day under normal conditions, increased 3.5 times, 3 days – 2.5 times, 28 days – 2 times. At the same time, it should be noted that when cement crystallohydrates are added, the hardening process is accelerated more in the initial terms of strength gain. The greatest strengthening effect was obtained by adding a complex modifier consisting of 0.8% plasticizer and 2% hydrated cement.

Impact of Gross Domestic Product, Government Capital Expenditure, Interest Rates and Remittance Inflow on Domestic Cement Consumption of Nepal

Impact of Gross Domestic Product, Government Capital Expenditure, Interest Rates and Remittance Inflow on Domestic Cement Consumption of Nepal

Air-conditioning supports for buildings: Challenges for a sustainable city

With the advancement of technology and the increase in global temperatures, there has been a demand for individual and collective cooling systems in residential and commercial buildings, leaving air conditioning equipment and their respective supports exposed on their facades. The objective of this study is to evaluate the degradation of reinforced concrete supports in a case study. It was found that 49.5% of the buildings have supports for air conditioners in the external area of their facades and of these 69% are reinforced concrete. From the aerial images it was possible to observe cracks in 90% of the supports and 21% presented partial collapse of the structure. It is concluded that the failure in the design of the reinforced concrete support without giving importance to the minimum requirements of coverage and quality control in the manufacture of concrete, are decisive in the increase of porosity and the entry of aggressive agents. The low useful life of these supports is associated with the risk of serious or fatal accidents with the fall of parts of these structures and leads to frequent replacement, demanding more cement consumption and more construction waste.

Modified high strength lightweight-aggregate concrete based on expanded clay: composition, structure, properties

The study is devoted to the development of increased strength lightweight concrete based on Portland cement modified with a complex organo-siliceous additive containing a polycarboxylate superplasticizer and an active fine-ground siliceous component. The effect of this complex additive on the physical and chemical characteristics of the hydration and structure formation processes was investigated and it was shown that the high kinetics of the strength gain is provided by directional formation of low-basic calcium hydrosilicates, hydrogranates and plazolite, which are crystallo chemically similar to each other, and provide a dense and strength cement stone matrix.
 Modification by a complex additive makes possible to obtain concrete mixes with S4 consistency while a portland cement consumption per 1m3 of not more than 330 kg, with a compressive strength of 55 MPa, watertightness up to W8, frost resistance up to F400, corrosion resistance coefficients Kc in the magnesium sulfate, sodium and ammonium solutions by 10 to 24%. The introduction of a complex additive also helps to reduce the relative shrinkage by 16 ... 19% compared to the control composition, which has a positive effect on the durability of the resulting concrete.

Вплив механохімічної активації композиційного цементу на міцність будівельного розчину

The article discusses issues related to the use of technology for the production of mortar mixtures and mortars based on high-speed mixers, the operation of which causes mechanochemical activation of the binder. The rotary counterflow mill used in the work acts as an activator of the surface zone of both Portland cement grains and quartz sand grains and, thus, contributes to the intensification of the processes of structure formation of cement paste and mortar based on it. Based on the fact that one of the promising ways to reduce the cost of cement activation is to reduce the energy intensity of the dispersion process itself, the use of relatively low-energy rotary mills can be considered as an effective way to increase the activity of the binder. After the joint activation of Portland cement and unground quartz sand (the amount of which was adjusted from 0 to 50 % of the cement mass; activation period - 300 seconds), samples were made from equal-viscosity cement paste. It was experimentally established that the maximum strength of cement stone at 28 days of age was achieved when using composite cement with a 20 % content of activated sand. To determine the influence of the studied factors, such as the consumption of mechanically activated composite binder, the concentration of superplasticizer C-3 (0...1,5 %) and the consumption of microsilica (0...10 %) on the strength of the mortar in 2 and 28-day old, a 3-factor experiment was conducted. It was established that in the studied hardening period, the content of mechanically activated composite cement has the greatest influence on the compressive strength for the studied mortar compositions (from 1:3 to 1:1). The next most important influence on the strength of the mortar is the consumption of superplasticizer C-3. The increase in compressive strength of a mortar from the introduction of microsilica into its composition does not exceed 10-15 %. The combined effect of mechanical activation of the binder and the use of the C-3 additive ensures an increase in the strength of the mortar (mortar composition 1:1) at 28 days of age from 43,5 MPa (non-activated binder; no C-3 additive) to 63 MPa, that is, almost by 45 %. For a mortar of similar age with a lower consumption of composite cement (mortar composition 1:3), mechanical activation of the binder in the presence of 1,5 % C-3 additive ensures an increase in the compressive strength of the mortar from 21 MPa (non-mechanically activated binder; C-3 = 0 %) to 39 MPa.

Low-carbon effects of constructing a prefabricated subway station using a trenchless method: A case study in Shenzhen, China

The traditional open-cut construction method for subway stations poses significant social and environmental challenges, and a trenchless method represents a promising alternative. This study uses the construction of a subway station in Shenzhen using a trenchless pipe-jacking method, as a case study. The design concept and construction scheme of the station are presented in detail, and the technical benefits of the technology are analysed. To assess the low-carbon effects of the method, this study uses life cycle assessment (LCA) theory. The findings indicate that the greenhouse gas (GHG) emissions of the station constructed this way are 10.5% less than those of the open-cut cast-in-situ (CIS) method. This decrease is attributable to reduced GHG emissions of 9.39% and 20.14% from building materials and related to energy consumption, respectively, achieved by reducing material consumption and improving electrification. Soil reinforcement engineering at the launching and receiving shafts is a significant factor affecting 34.17 % of the GHG emissions of the trenchless method, primarily owing to the significant cement consumption. The trenchless construction method used for the middle part of the station, which is beneath a large box culvert section, can decrease GHG emissions by 52.66% compared with open-cut CIS schemes. This is due mainly to the avoidance of additional GHG emissions resulting from the relocation of large box culverts required before open-cut construction of the station. Trenchless method, therefore, offers many advantages in reducing emissions and generating social benefits in complex urban environments compared with open-cut method, making it an essential approach to assist sustainable underground space development.

A study on waste PCB fibres reinforced concrete with and without silica fume made from electronic waste

This research goal is to appraise the effect of electronic waste on concrete properties by examining the mechanical properties of concrete reinforced with waste printed circuit boards (PCBs). PCB fibres, each 50 mm long, were mixed in varying proportions (1–5% by weight of cement). Silica fume (SF) was used as a 12% weight replacement for cement to conserve the properties of PCB fibre-reinforced concrete while tumbling cement consumption. Following a 28-day curing period, the fresh and hardened characteristics of PCB fibre-reinforced concrete were juxtaposed with those of conventional concrete. The experimental results led to the conclusion that 5% by weight of cement is the most effective proportion of PCB fibres to include in both PCB fibre-reinforced concrete and silica fume-modified PCB fibre-reinforced concrete. The addition of PCB fibres and silica fume significantly increased the mechanical strength of the concrete, making it suitable for high-strength concrete applications. Based on a similar investigational research design, an artificial neural network model was created, and it played a critical role in predicting the mechanical properties of the concrete. The model produced accurate results, with an R-squared (R2) value greater than 0.99.

Investigation into compressive property, chloride ion permeability, and pore fractal characteristics of the cement mortar incorporated with zeolite powder

As a non-homogeneous porous material, the microstructure of cementitious composites critically affects the mechanical and durability properties. This paper aims to analyze the effect mechanism of cement replacement by zeolite powder on the microscopic pore structure characteristics, macroscopic mechanical behavior, and durability of mortar to reduce cement consumption and improve mortar performance. The compressive strength and chloride ion permeability of mortar incorporated with zeolite powder were experimentally determined, and the effects of zeolite powder content on the composition of cement hydration products and pore structure were further analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and mercury intrusion porosimetry (MIP). The pore structure characteristics were quantitatively analyzed by fractal theory. The results shows that incorporating zeolite powder in cement mortar fills the pores, promotes secondary hydrate formation, reduces the Ca/Si ratio, refines the pore size, and reduces the porosity of large pores. Thus, the internal pore structure of the matrix is significantly improved, reducing the pore fractal dimension and improving the compressive strength and chloride ion penetration resistance. 15% cement replacement zeolite powder has been found optimal in reducing the porosity and chloride ion permeability coefficient while enhancing the compressive strength. The pore structure fractal dimensions calculated by the Menger sponge fractal model can quantitatively describe the pore structure distribution characteristics, which can help ascertain the relationship between zeolite powder content, pore structure quantitative characteristics, and macroscopic mechanical behaviors.

Functionally Graded Concrete: Structural Design and Effect on Sustainability Parameters

Researchers have become interested in functionally graded concrete (FGC) in recent years due to its potential to enhance the desired performance. Functional gradation can be carried out in a continuous or stepped/layered manner. Most studies have been conducted on two layered FGC beams by substituting the richer mixes in either tension or compression zone. Previous studies have incorporated and presented the structural design approach of such two-layered beams. Moreover, the layer in the compression zone was assumed to bear entire compressive stresses. Previous studies exhibited savings in cement by up to 37% using a layer of the concrete class defined by exposure conditions around reinforcement and the concrete of minimal structural class. However, using structural concrete of minimal class in the remaining segments may result in a higher reinforcement requirement, reducing the benefits of savings in embodied CO2 offered by reduced cement consumption. This paper examines how designing the beam as a Functionally Graded Reinforced Concrete (FGRC) beam following Indian Standard 456:2016 affects the cost and embodied CO2 based on cement and steel consumption through the durability approach of design, wherein the substitution of the layer is considered in the tension zone. The study revealed that a 10% and 16% reduction in cost and embodied CO2 could be accomplished.

High-ductility basalt fiber reinforced cement composite with low CO2 emission by interface property transformation: Hydrogen bond transformed into covalent bond

Despite the beneficial features and reduced carbon footprint afforded by basalt fibers, the widespread use of basalt fiber-reinforced cement composite (BFRCC) has issues linked to decreased compressive strength beyond 28 days and insufficient toughness. This study aims to address these constraints by changing the chemical bonding between basalt fibers and the cement matrix from hydrogen bonds to covalent bonds via the use of a surface modification. In accordance with the results, a concentration of 2.5 % of the modifier yields the greatest improvement. The 2.5 % modified BFRCC has a compressive strength 1.88 times that of unmodified BFRCC and an elastic modulus 2.02 times that of unmodified BFRCC. Tensile strength and peak tensile strain are improved by 1.95 times and 2.99 times, respectively. The increased threshold for fracture initiation and the increased energy required for crack propagation are both attributable to the more uniform strain distribution within the improved BFRCC, which allows for higher load sharing. The weakening of the chemical bonds aids in reducing “Z”-type fiber failure. In comparison with conventional BFRCC, the use of modified BFRCC contributes to reducing reductions in cement consumption and greenhouse gas emissions.

SUBSTANTIATING THE CONCEPTS OF COMPONENTS COMPOSITION AND METHOD OF OBTAINING SOIL-CEMENT ELEMENT FOR REINFORCEMENT OF EMBANKMENTS

Purpose. Substantiating of the choice of components of materials and methods of obtaining a soil-cement element for strengthening the ground bases in Ukraine, taking into account the European experience. Methodology. The concepts of embankment reinforcement developed and implemented in Ukraine and the European union using horizontal reinforcement (geosynthetic materials), vertical reinforcement (vertical piles or micropiles) and a combination of geosynthetic materials with piles are analyzed. Advantages and disadvantages of physic-chemical and mechanical strengthening methods are considered. Findings. The substantiation of the material and constituent components of soil-cement elements and methods of their creation for strengthening the embankment of railways was carried out. One of the effective directions for obtaining vertical reinforcing elements and reducing the cost of work on strengthening and strengthening the embankment is the use of a mixture of soil with the addition of cement, obtained by drilling mixing technology. To modify the structure of soil cement and minimize cement consumption, it is suggested to use fiber fibers, chemical additives and finely dispersed industrial waste in the form of ash or ground slag as reinforcing components. A study was conducted to establish the basic parameters of the soil-cement composition for further modification of the structure of the element under the specific situational conditions of the embankment. Originality. The originality of the work is that, for the first time, based on the strengthening experience, the justification of the directions of strengthening the ground bases with vertical soil-cement elements at different stress-deformation conditions of the soil foundations and the composition of vertical elements in Ukraine and the European union was performed. Practical value. The practical value of the presented research is that when choosing one or another method of strengthening soil bases, the appropriate composition of the strengthening material is selected, that is, its efficiency and rationality can be determined during implementation in the specific conditions of operation of the railway, the embankment of which needs to be strengthened or rearranged for a combined or European track.

Mechanical and Microstructural Properties of Bamboo Fiber-Reinforced Concrete Containing a Blend of Waste Marble Powder and Waste Glass Powder

Using blended supplementary cementitious materials in the production of concrete has a contribution to make in reducing cement consumption, as well as having a negative environmental impact. The main objective of this study was to investigate the mechanical and microstructural properties of bamboo fiber-reinforced concrete containing a blend of waste marble powder (WMP) and waste glass powder (WGP) as a partial replacement for cement. To achieve these objectives, the physical and chemical properties of concrete ingredients were studied. The design mix was done as per the American Concrete Institute (ACI) mixing procedure by using 5%, 10%, 15%, and 20% blended WMP and WGP as a replacement for cement and 0.75% bamboo fiber as an addition. The mechanical tests were conducted after samples were cured for 7 and 28 days in water. The microstructural properties of the hardened concrete from three different mixes were also determined for the 28-day cured specimens. The study result indicated improvement in compressive strength, shear stress, and bond stress at M2 (10%), whereas maximum splitting tensile strength was achieved at M1 (5%). Moreover, scanning electron microscopy (SEM) showed a denser microstructure, whereas X-ray diffraction (XRD) illustrated portlandite, calcium aluminum silicate, quartz, and calcium silicate hydrate as common phases of the concrete structure. Eventually, the experimental finding implied that using a 10% blend of WMP and WGP as a partial replacement for cement and 0.75% bamboo fiber improves fresh and hardened concrete properties.

Utilization of ground granulated blast-furnace slag and electrolytic manganese residue as a low-carbon cementitious material

Ground granulated blast-furnace slag (GGBS) is a common substitute for ordinary Portland cement (OPC). However, GGBS–OPC lacks early strength when OPC content is low (<50%). A new cementitious material called GGBS–OPC–EMR (GOE) was developed by adding electrolytic manganese residue (EMR) to address this issue. Tests were conducted using XRD, SEM, and TG to analyze the micro-structural mechanisms of strength development in GOE. Environmental and economic evaluations were conducted, including CO2-eq (carbon dioxide equivalent) analysis, leaching tests, and economic analysis. Results showed that mixture of GGBS, OPC, and EMR in a 4:2:1 ratio increased the unconfined compressive strength by 25% after 28 days compared to OPC while reducing cement consumption by 70%. Major hydration products in GOE were C–S–H and ettringite (AFt), with approximately 14% EMR promoting AFt production. GOE reduced CO2-eq emissions by 35.9% and saved $46.6/ton compared to OPC. Leaching tests demonstrated GOE's ability to stabilize heavy metals, sulfate, and ammonia nitrogen.

Effects of FeNi3 Nanoparticles and Coal Slag on Mechanical and Durability Properties of Concrete against Acidic Environments

In recent years, natural pozzolans have been proposed as a way to improve the mechanical and biocompatible properties of concrete. This study investigated the effects of different amounts of nanoparticles, coal slag pozzolan, and their combination on the mechanical properties and durability of concrete. For each mixed design, nine cubic samples of 10 × 10 × 10 cm and 30 × 15 cm were made and then cured in water for 28 days before being tested for compressive and tensile strength. According to the results, pozzolan at about 5% of cement weight increased the compressive strength of concrete compared to samples without pozzolan. Nanoparticles of FeNi3 greatly enhanced the compressive and tensile strength of concrete in most samples containing nanoparticles. The compressive and tensile strength of 28-day concrete increased by 27% and 18%, respectively. Pozzolan (10%) and 2% of FeNi3 (CP10F2) in concrete also reduced the water absorption of the samples, which can improve the durability parameters of concrete. In concrete exposed to sulfuric acid, sample CP0F2 (2% of FeNi3 nanoparticles) had a positive effect on compressive strength, and samples containing 2% of FeNi3 nanoparticles had higher compressive strength than those with pozzolan replacing cement. The simultaneous use of coal slag and FeNi3 nanoparticles has increased the mechanical properties and durability of concrete in addition to reducing cement consumption.

RESEARCHING THE INFLUENCE OF PLASTICIZERS ON THE TECHNOLOGICAL AND PHYSICAL-MECHANICAL PROPERTIES OF COMPOSITE BINDING SUBSTANCES OF THE СаО – Al2O3 – SO3 – H2O SYSTEM

Problem statement. Composition of modern concretes and mortars includes surface-active substances that regulate processes of hydration, structure formation and, accordingly, properties of artificial stone. One of the types of surface-active substances are plasticizers, their main purpose is to reduce water consumption. When considering their influence, a wider range of changes in the properties of solutions and concretes can be noted. In this regard a particular attention should be paid to aluminate, sulfate and sulfo-aluminate binders. Therefore, the development of composite binders of the CaО – Al2O3 – SO3 – H2O system based on alumina cement and gypsum with the use of plasticizers requires research in this direction. The purpose of the article – to investigate the effect of plasticizers on the technological and basic physical and mechanical properties of alumina cement and composites based on it. Conclusions. A complex of experimental and statistical models of nanomodified compositions based on alumina cement and gypsum was obtained, and these models make it possible to determine influence of input factors on the growth of the main physical and mechanical properties. Research has established the ratio of the basic components of the composite based on 70 % alumina cement, 30 % gypsum and Sika VG Sika plasticizer = 0.10 ÷ 0.40; alumina cement = 69.72 ÷ 69.93; Gypsum = 29.88 ÷ 29.97. According to the manufacturing technology, the number of components was reduced to a minimum and a binder-filler-plasticizer system was obtained. From the economic point of view, depending on the customer’s requirements, it is possible to regulate the consumption of alumina cement and gypsum binder within the limits of approximately 10 %.

Designing sustainable high-strength self-compacting concrete with high content of supplementary cementitious materials

A sustainable and green approach to concrete mix design is fundamental for the construction sector in terms of reducing carbon dioxide ( CO 2 ) emissions and conserving non-renewable natural resources. This article proposes a novel mix design method for sustainable high-strength self-compacting concrete (HSSCC) based on rheological and mechanical properties with the aim of reducing cement content in such mixes. HSSCC mixes were designed using ground granulated blast furnace slag (GGBS) and fly ash to replace up to 40% of the cement content and tested for target compressive strengths ranging between 70 and 100 MPa. The proposed design method was numerically programmed to provide straightforward and realistic guidance in the form of design charts and verified through the design and production of sixteen HSSCC mixes consisting of varying sand-to-aggregate ratios (S/A). All mixes satisfied the self-compacting concrete criteria in the fresh state and achieved the targeted viscosity and compressive strength values. The effects of S/A and paste-to-solid (P/S) ratios on the rheological properties were evaluated. The experimental results demonstrated that the proposed mix design method could produce HSSCC with excellent fresh and mechanical characteristics while being eco-efficient with respect to CO 2 emissions and cement consumption.

ON THE PROPERTIES OF CEMENT-SAND MORTARS PLASTIFIED WITH CARBONATE CLAYS

The use of cement-sand mortars plasticized with carbonate clays in earthquake-resistant construction has been demonstrated in experimental tests. The compositions and physical-and-mechanical characteristics of these mortars have been identified for the first time, allowing for a reduction in cement consumption of up to 40% as well as a complete elimination of the costly lime while enhancing the mortar's strength. The use of cement-sand mortars plasticized with carbonate clays has been suggested for performing earthquake-resistant construction from local sawn limestone. The experiments’ findings were put to the test and put into practice in Nagorno-Karabakh's construction complex. The study's finding s are in line with research and regulatory documents for cement-clay mortars for masonry.

Experimental study and simulation of workability and compressive performance of SCC with high-volume mineral admixtures

Using industrial waste such as fly ash and silica fume to substitute most of the cement to prepare self-compacting concrete can not only greatly reduce the cement consumption, but also improve the resource utilization of solid waste powder, which is conducive to cost reduction and environmental protection. In this paper, the fly ash (FA) and silica fume (SF) replacement ratio of 40%, 50% and 60% was adopted to produce self-compacting concrete with high-volume mineral admixtures (HVMA-SCC). The slump flow test, L-box test and compression test were conducted, and the effect of different high replacement ratio on the workability, compressive performance and stress–strain relationship of HVMA-SCC were analyzed. The experimental results showed that when the total content of mineral admixtures was the same, an increase in SF content was beneficial for the development of early compressive strength. Under the same SF dosage, the larger the FA dosage, the faster the strength development rate, which was conducive to the sustained growth of HVMA-SCC strength in the later stage. Moreover, a stress–strain calculation model of HVMA-SCC was proposed based on damage theory. Besides, the workability and compression tests were simulated with the discrete element method (DEM). The results showed that the simulated stress–strain curves were in good agreement with experimental curves, and the mesoscopic failure characteristics of HVMA-SCC were analyzed from the development of cracks, stress conditions, and failure modes.