Low-cement Concretes Research Articles

Optimizing aggregate grading and residual mortar coefficient in low-cement concrete by using crushed coal mine waste rock as base layers for low-traffic roads

In the context of depleting natural resources and environmental challenges posed by large-scale extraction and use of natural aggregates, this study investigates the use of crushed coal mine waste rock (CCMWR) as a sustainable alternative for low-cement concrete in the base layers of low-traffic roads. The primary goal is to optimize the aggregate grading and the residual mortar coefficient (RMC) to enhance the performance and durability of low-cement concrete. Utilizing the I-optimal design methodology and curve of Fuller for particle size distribution, this research evaluates the mechanical properties, workability, and environmental impact of incorporating CCMWR in low-cement concrete. The findings demonstrate that with the appropriate optimization, CCMWR can effectively replace natural aggregates, significantly reducing the ecological footprint and providing an effective solution for sustainable road construction. This research holds substantial engineering application significance by offering an innovative approach to classify and reuse waste from the coal mining industry while addressing the urgent need for sustainable infrastructure development.

Mechanical behavior and damage constitutive relationship of basalt-brucite hybrid fiber reinforced low-heat cement concrete

In this study, the mechanical properties and microstructure of basalt-brucite hybrid fiber reinforced low heat cement concrete was explored. The results indicated that the mechanical properties of low heat cement concrete first increase and then decrease with the increase of hybrid fibers volume fraction, and the cubic compressive strength, splitting tensile strength, and axial compressive strength of the optimal strengthening group, that volume fraction is 0.20% for basalt fiber and 0.15% for brucite fiber, respectively, increased by 40.16%, 70.61%, and 56.16%, respectively. Under a reasonable volume fraction of hybrid fibers, the mechanical properties of concrete could be significantly improved. By comparing the bonding effect between fibers and concrete, fibers exhibited different distribution patterns in concrete matrix, that could improve the compactness of concrete matrix through filling effect, optimize internal structure, and delay the connection and expansion of microcracks. The causes of the bonding effect between fibers and concrete was discussed from the perspective of chemical bonding effects. Based on the above analysis, the reinforcement mechanism of hybrid fibers on concrete was explored. Based on statistical damage theory, a damage constitutive equation for hybrid fiber reinforced low heat cement concrete considering fiber volume fraction was established by modifying the model parameters, and the model curve fitted well with the experimental curve.

Investigation of the Cementing Efficiency of Fly Ash Activated by Microsilica in Low-Cement Concrete.

This paper presents experimental results on the influence of concrete composition factors on the criterion characterizing the ratio between the compressive strength of activated low-cement concrete and clinker consumption. The investigation was carried out using mathematical planning of the experiments. Experimental and statistical models describing the influence of the fly ash, activating additive (microsilica), consumption of cement and aggregates, as well as the superplasticizer on the strength of low-cement concrete under normal hardening conditions and after steaming were obtained. The values of the clinker efficiency criterion and the mineral additive cementing efficiency coefficient were calculated, and models of these parameters were obtained for the investigated concrete compositions. It was shown that the activating effect of microsilica yields an increase in ash cementing efficiency and clinker efficiency criterion in concrete. Using the obtained models, an example for calculating the ash cementing efficiency coefficient is given.

ВЛИЯНИЕ МИКРОНАПОЛНИТЕЛЕЙ НА ЭФФЕКТИВНОСТЬ СУПЕРПЛАСТИФИКАТОРОВ И ПРОЧНОСТЬ БЕТОНОВ С НИЗКИМ СОДЕРЖАНИЕМ ЦЕМЕНТА

In concretes of ordinary grades with a cement consumption of 180–250 kg/m3, the reduction in the water demand of the concrete mixture, even with the maximum consumption of superplasticizers, does not exceed 10 %. In this regard, the influence of micro-fillers with various electrosurface properties on the effectiveness of the superplasticizer and the strength of low-cement concrete is investigated. 
 It is shown that in the concrete mixture of the control composition, achieving a normal consistency (PK = 106–115 mm) is possible only due to high water consumption, the water-reducing efficiency of the joint venture was only 4,5 %. It was found that with the addition of fine quartz from 20 to 70 %, the consumption of the powder part increased from 230 to 452 kg/m3, while there was a decrease in W / C from 0,68 to 0,51 (33 %), as well as an increase in strength by 40,5 % (R7comp) and 30,6 % (R28 comp). With an increase in the dosage of limestone microfillers from 20 to 70 % W / C decreased from 0,66 to 0,5 (32 %), the strength increased by 145 % (R7 comp) and 74% (R28 comp). Thus, the use of fine-dispersed fillers in low-cement concretes makes it possible to achieve a significant reduction in W/C by 23,6–43,8 % in equally mobile mixtures (GOST 310.4), depending on the dosage of the powder filler (20–70 %), while the type of filler does not have a noticeable effect on the water-reducing ability of the superplasticizer, but plays a significant role in the processes of structure formation of cement concrete matrices, due to the influence of their electrosurface properties on the adhesion between filler particles and cement stone. In low-cement concretes, with the growth of fine fillers from 20 to 70 %, the strength of concrete increases.

Effect of the outer UHDC layer on shear and flexural behavior of RC beams produced with low binder concrete

Composite beams with a cement distribution along the cross-section more efficient can be used to increase their durability and simultaneously decrease the ecological footprint related with cement production. The higher dosages are used only on the cover layer, to provide a higher protection of the steel reinforcement, and the core of the beams is produced with a low cement concrete, using in this case 125 kg of cement per m3. In addition, the core is not subjected to such higher normal stresses as on both bottom and top of the cross section, so the mechanical performance of this concrete is not so challenging and, consequently, the cement dosage can be thus reduced.This experimental study aims to analyze how the strength capacity and stiffness of beams are affected using the ‘superskin’ concept, particularly the influence of how the external layer made with an ultra-high durability concrete (UHDC) is applied, being the core produced with a low binder concrete (LBC).Nine different beams were tested, until bending or shear-controlled failure occur, varying the longitudinal tensile reinforcement ratio and the way how the UHDC layer is applied: i) one single layer with a ‘U’ shape around cross-section and, ii) three separated thin plates, cast against the core concrete. The followings parameters were analyzed: load–displacement relation, flexural strength, shear strength, ductility, crack pattern and failure mode. The results show that this type of beams present a better structural behavior relatively to the reference beams, beyond the two benefits already identified, the durability and eco-efficiency increase. In certain beams the flexural strength increased around 70% and the shear strength almost 90%. The results also reveal the advantages of using a monolithic UHDC layer, namely, in terms of cracking.

ANALYSIS OF THE DEGREE OF INFLUENCE OF INTERNAL AND EXTERNAL FACTORS ON THE TEMPERATURE REGIME OF A LOW-CEMENT CONCRETE DAM

In this paper, we consider the issue of assessing the degree of influence of the selected factors on the temperature regime and the thermally stressed state of a concrete gravity dam being built from low-cement concrete for several possible construction scenarios. The studies were carried out in relation to the design and conditions of the construction area of ​​the Pskem hydroelectric complex in the Republic of Uzbekistan. Variation factors were: cement consumption in the mixture, the initial temperature of the concrete mixture, the heat release of cement, the thickness of the laid concrete layer, the month of commencement of work. The environmental factors were the variable ambient temperature during the year by months and the influence of solar radiation. The calculations were carried out taking into account the seasonality of the moment the construction of the structure began. 2 options were considered: autumn-winter with concreting of the zone at the base of the dam from September to February inclusive; spring-summer with concreting of this zone from March to August inclusive. In addition, options were considered taking into account additional heating from exposure to solar radiation and without it. The studies were carried out using the methodology of experiment planning in the search for optimal solutions (method of factor analysis). The numerical experiment was carried out on the basis of the finite element method using the ANSYS software package. Using the method of factor analysis, the influence of the main acting factors on the temperature regime of a gravity dam made of rolled concrete was studied. A variant of a combination of factors is proposed to obtain the most favorable temperature regime. Regression equations are obtained for predicting the temperature regime of concrete gravity dams being built from low-cement content concrete. The results of studies using the factor analysis technique can be used in the design of concrete dams from rolled concrete.

Cement with Fly Ash and Metakaolin Blend—Drive towards a More Sustainable Construction

This article presents experimental studies that have shown the effectiveness of using a composition of fly ash and metakaolin as an active mineral admixture to cement. It is shown that composite ash–metakaolin additives (AMAd) have on the one hand increased pozzolanic activity and surface energy, and, on the other hand, moderated water demand and provided a significant increase in strength, which is especially important for low-cement concretes. The obtained experimental–statistical models make it possible to determine the effect of the AMAd composition, its content in combination with the addition of a superplasticizer on the rheological properties, the kinetics of structure formation and the main physical and mechanical properties of cement.

The effect of dispersants on the properties of low-cement concrete for the furnace of smelting of jewelry waste

Melting in ceramic crucible is one of the stages of recycling jewelry production. Conceptivity of concrete mass plays an important role in molding a large-scale refractory crucible to vibration. The impact of a number of commercially available dispersants (CASTAment FS 10, MELFLUX 1641 F, peramin al 200, FF7 SPEZIAL and PC-1701) on the rheology of the low-cement concrete mass of corundo-mullite-zirconium composition and the physico-mechanical properties of the material are considered. The best results were obtained using the PC-1701 dispersant.

Low-Cement Refractory Concretes of Aluminum Silicate Composition Based on Submicron Aluminum Oxide Grade NK-Alumina 14

Low-Cement Refractory Concretes of Aluminum Silicate Composition Based on Submicron Aluminum Oxide Grade NK-Alumina 14

Effect of Dispersants on the Properties of Low-Cement Concrete for Jewelry Waste Melting Furnaces

Effect of Dispersants on the Properties of Low-Cement Concrete for Jewelry Waste Melting Furnaces

Study of low-cement concrete mix-design through particle packing techniques

The cement production is responsible for about 7% of global emissions of carbon dioxide (CO2) into the atmosphere. One way to mitigate this impact is through the consolidation of techniques involving the production of environmentally sustainable mixtures, such as partially replacing cement for mineral admixtures. This paper aims to use a mix-design method based on particle packing techniques to produce and evaluate the properties of a low-cement concrete (LCC). This mix-design method is based on cyclic interactions, where the particle packing, the water demand and a prediction of the concrete compressive strength is performed. Granular optimization studies of the aggregates and the fine materials, rice husk ash and quartz powder, were carried out to reduce the number of voids in the concrete and partially replace Portland cement. A concrete designed by a conventional mix-design method was taken as a starting point for the application of the particle packing techniques, in the quest to reduce cement consumption, so that it was called initial concrete (C0). Concrete properties evaluated, in the fresh state, were consistency through slump test and specific gravity. In the hardened state, properties of compressive strength, tensile strength by diametrical compression, specific gravity and water absorption tests by immersion and capillarity were studied. As a result, it was possible to reduce 40% of the cement consumption by applying the particle packing techniques, resulting in 164 kg of cement/m³. The LCC presented compressive and tensile strengths, at 28 days, of 31 MPa and 2.9 MPa, respectively.

Influence of Pozzolan, Slag and Recycled Aggregates on the Mechanical and Durability Properties of Low Cement Concrete.

The sustainability of the construction sector demands the reduction of CO2 emissions. The optimization of the amount of cement in concrete can be achieved either by partially replacing it by additions or by reducing the binder content. The present work aims at optimizing the properties of concrete used in the production of reinforced concrete poles for electrical distribution lines, combining the maximization of compactness with the partial replacement of cement by fly ash, natural pozzolans, and electric furnace slags. Natural aggregates were also partially replaced by recycled ones in mixtures with fly ash. Two types of concrete were studied: a fresh molded one with a dry consistency and a formwork molded one with a plastic consistency. The following properties were characterized: mechanical properties (flexural, tensile splitting, and compressive strengths, as well as Young’s modulus) and durability properties (capillary water absorption, water penetration depth under pressure, resistance to carbonation, chloride migration, and concrete surface resistivity). The service life of structures was estimated, taking the deterioration of reinforcement induced by concrete carbonation or chloride attack into account. Results revealed that mixtures with fly ash exhibit higher mechanical performance and mixtures with fly ash or pozzolans reveal much higher durability results than the full Portland cement-based mixtures.

Enhanced Mechanical and Durability Performances of Low Cement Concrete with Natural Pozzolan Addition

Enhanced Mechanical and Durability Performances of Low Cement Concrete with Natural Pozzolan Addition

Experimental development of low cement content and recycled construction and demolition waste aggregates concrete

Innovative eco-efficient concrete was developed and characterized, to reduce the environmental impact related to construction and demolition waste, extraction of natural aggregates, and CO2 emissions of Portland cement. Several concrete mixtures with low cement content and incorporating construction and demolition waste (CDW) recycled aggregates, herein named “low cement recycled aggregates concrete” (LCRAC), were newly developed. Characterization tests were performed to minimize cement dosage and maximize the replacement of natural by CDW aggregates. An optimized matrix of low cement concrete was developed and high replacement volume rates of CDW aggregates (43–80%) were considered, leading to different LCRAC, to evaluate their influence on concrete properties. The mechanical properties of LCRAC are highly influenced by the aggregates composition and its replacement rate. A reduced and optimized cement dosage, of 175 kg/m3, allows producing sustainable LCRAC for structural applications. The strength reduction of LCRAC is limited to only 30% when incorporating high volume of CDW, up to 60%, since the strength loss of CDW is balanced by the matrix high compactness and higher strength, resulting in equivalent strength of ordinary concrete formulation.

Efficiency of cement content and of compactness on mechanical performance of low cement concrete designed with packing optimization

The unavoidable concern with developing sustainable materials in the construction sector has led to the attempts to reduce the content of Portland cement in structural concrete mixtures. Thus, the main objective of this research was to develop low cement concrete (LCC), maximizing the replacement rate of cement by additions and/or reducing the amount of binder through combining the design parameters of concrete, such as water/cement, water/binder, and compactness, without compromising the specified mechanical performance and consistency. The mix-design and characterization of various LCC mixtures were developed, considering two amounts of powder in the binder paste, 350 and 250 kg/m3, being the first with very plastic consistency and the latter with dry consistency and low cohesion, due to the reduced proportion of water and binder. These were combined with large spectrum of cement replacement rates, through adding fly ash and limestone filler, as well as with different compactness levels, and with the variation of aggregates proportions. The concrete mixtures were characterized in fresh and hardened states, in terms of consistency, compressive, tensile and flexural strengths and the Young’s modulus.Results revealed that a lower amount of powder in the binder paste leads to lower consistency and cohesion. However, it is possible to improve the workability if a powder content up to 350 kg/m3 is adopted. Thanks to the optimized combination of Portland cement, fly ash and limestone filler additions, and the granulometric optimization and the use of superplasticizer, it is possible to produce LCC with good workability, stability, and mechanical performances, thus mitigating the limitation of using high content of fly ash as partial substitute for cement. The characterization of the mechanical strengths and the Young’s modulus revealed that is possible to substantially reduce the Portland cement content of LCC mixtures, up to about 50%, being however possible to increase that replacement rate up to 70%, assuming simultaneously an adequate performance for structural purposes. The variation of aggregates proportioning, which is controlled by different granulometric curves, revealed high influence both on consistency and on Young’s modulus.

The study of the destruction of heat-resistant chamotte concrete during its sharp heating and cooling

The article investigates the destruction of heat-resistant chamotte concrete of various classes: low-cement and medium-cement with the addition of quartz sand (to increase alkaline resistance) and with the addition of metal fiber (to reduce cracking) after exposure to thermal shock. Two methods for determining the heat resistance of concrete were used, in which the destruction of the material was evaluated using ultrasound using the method of a water-cooled plate and the method of one-sided heating-cooling. Studies conducted using the method of unilateral heating-cooling, revealed the formation of macrocracks in samples of low cement concrete. This method turned out to be more sensitive when evaluating concrete destruction.

Study on the Destruction of Heat-Resistant Chamotte Concrete During Sharp Heating and Cooling

This study investigates the destruction of heat-resistant chamotte concrete of various classes: low-cement and medium-cement after exposure to thermal shocks. The influences of the addition of quartz sand (to increase alkaline resistance) and the addition of metal fiber (to reduce cracking) were also studied. Two methods were used to determine the heat resistance of concrete, according to the material destruction: a water-cooled plate method based on ultrasound and a method of unilateral heating-cooling. The results obtained via the method of unilateral heating-cooling revealed the formation of macrocracks in samples of low-cement concrete. This method was found to be more sensitive for evaluating concrete destruction.

Durability and Time-Dependent Properties of Low-Cement Concrete.

The sustainability concerns of concrete construction are focused both on the materials’ eco-efficiency and on the structures’ durability. The present work focuses on the characterization of low cement concrete (LCC), regarding time-dependent and durability properties. LCC studies which explore the influence of the formulation parameters, such as the W/C (water/cement ratio), W/Ceq, (which represents the mass ratio between water and equivalent cement), W/B (water/binder) ratio, and the reference curves, on the aforementioned properties are limited. Thus, several LCC mixtures were formulated considering two dosages of binder powder, 350 and 250 kg/m3, the former with very plastic consistency and the latter with dry consistency, which were combined with a large spectrum of cement replacement rates (up to 70%), through adding fly ash and limestone filler, and with different compactness levels. The main objectives were to study the influence of the formulation parameters on the properties: shrinkage and creep, accelerated carbonation and water absorption, by capillarity, and by immersion. The lifetime of structures produced with the studied LCC was estimated, considering the durability performance, regarding the carbonation effect on the possible corrosion of the steel reinforcement. LCC mixtures with reduced cement dosage and high compactness, despite the high W/C ratios, have low shrinkage and those with higher strength have reduced creep, however depending on W/Ceq ratio. Those mixtures can be formulated and produced presenting good performance regarding carbonation resistance and, consequently, a long lifetime, which is mandatory for a sustainable construction. LCC with 175 kg/m3 of cement dosage is an example with higher lifetime than current concrete with 250 kg/m3 of cement; depending on the XC exposure classes (corrosion induced by carbonation), the amount of cement can be reduced between 37.5% and 42%, since the LCC with 175 kg/m3 of cement allows reducing the concrete cover below the minimum recommended, ensuring simultaneously the required lifetime for current and special structures.

Low-cement concrete dams: construction, structures and innovations

Introduction. Low-cement concrete dams are water-retaining structures frequently used in modern hydraulic engineering. The number of facilities of this type goes up every year due to their simple design, speedy construction and high economic efficiency. However, a number of problems may arise in the construction and operation of such facilities. In particular, reduced strength and water permeability of interlayer joints may constitute a problem. Temperature effects arising in the course of construction and operation may cause additional deformation of their structure, changes in their stress-strain state, opening of existing cracks and further cracking. The study of the design experience, building and operation of dams made of low-cement concrete will lay the groundwork for the development of similar structures and defect elimination methods. It will also provide an opportunity to learn more about thebehaviour of structures exposed to various conditions, including climatic ones.
 Materials and methods. Data on existing dams made of low-cement concrete, research articles, technical reports and conference proceedings, including those issued by the International Commission on Large Dams (ICOLD), have been collected and analyzed.
 Results. The comparative analysis of designs of dams in operation and future-oriented solutions is performed. The co-authors have demonstrated the need for an integrated approach to solving temperature cracking problems by using filtration through the dam body.
 Conclusions. The results can be used as the basis for further detailed studies. The comparative analysis of traditional and innovative waterproofing liners will help to effectively choose the protection solution for an upstream face of a facility. New forecasting methods and recommendations aimed at the reduction of negative temperature effects on the operation of facilities can solve the temperature cracking problem.

Mix design of low-cement concrete with particle packing concept and superplasticizer application

The amount of cement paste used in concrete depends on aggregate particle packing, where the denser combination among particles with different particle sizes results in a minimum volume of voids (Vv). Theoretically, cement paste volume (Vp) is required to fill the void with the combination of fine and coarse aggregate, i.e., Vp/Vv = 100%. The purpose of this paper was to propose a concrete mix design method that could maximize the particle packing of aggregates to reduce the cement content in concrete mixture, hence producing low-cement concrete (LCC). The variables proposed were the ratio between the volume of paste to the volume of voids (Vp/Vv) as opposed to the cement content and the use of superplasticizer to control the workability of the fresh concrete. The results showed that by the combination of multi-sized coarse aggregates and fine aggregate, the smallest void volume of 23.5% could be achieved. The theoretically lowest cement content needed for a mixture with w/c 0.5 was 287 kg/m3. However, after trial mixing, the cement requirement was found to be almost equal with conventional concrete, i.e., about 310 kg/m3. Workability of the mixture depended on the paste volume to void volume ratio (Vp/Vv > 100%) and was greatly influenced by the superplasticizer content. The use of excessive superplasticizer could cause bleeding due to lack of fine particles in the low cement concrete mixture. The use of cementitious material, such as fly ash by 50%, to replace cement, significantly improves the workability and reduces the cement content below the minimum cement requirement with similar compressive strength as the water to cementitious ratio mainly controls compressive strength.