Cement-free Concrete Research Articles

Impact of various fibers on mode I, III and I/III fracture toughness in slag, fly Ash, and silica fume-based geopolymer concrete using edge-notched disc bend specimen

There is ongoing research aimed at developing cement-free concrete that not only exhibits enhanced mechanical properties but also incorporates environmentally sustainable materials. Geopolymer represents a novel inorganic cementitious material recently developed, which facilitates utilising resources derived from solid waste from industrial operations. Geopolymer is considered an ecologically sustainable substitute for Ordinary Portland cement. It significantly reduces energy usage and minimizes carbon dioxide emissions, contributing to environmental sustainability. This study investigates the combined influence of granulated blast furnace slag, fly ash and silica fume on geopolymer concrete (GC) fracture resistance. This research aims to assess the fracture toughness of GC under modes I, III, and I/III loading conditions. Four distinct fiber types, comprising both short and long steel fibers and polypropylene fibers at 1.5 % dosage, were utilized to mitigate brittleness and enhance the ductility of the material. In addition, the microstructure of GC was analysed using X-ray diffraction and scanning electron microscopy. Findings reveal that the inclusion of short and long polypropylene fibers in GC increased mode I fracture toughness by 20.98 % and 29.62 %, respectively, compared to the fiber-free specimen, with long fiber showing superior performance due to its enhanced crack-bridging ability. Steel fibers provided a more pronounced improvement, with short and long fibers increasing mode I fracture toughness by 77.77 % and 109.87 %, respectively, attributed to their capacity to hinder crack propagation and enhance fracture toughness. The long fibers exhibited an excellent fracture resistance than the short fibers and mode III is more critical than the mode I loading.

Early-Age Shrinkage Stress of Alkali-Activated Cement-Free Mortar Using Shrinkage Reducing Agent and Expansive Additive

Cement-free concrete has a superior physical performance, such as in its strength and durability, compared to OPC concrete; however, it has the disadvantage of large shrinkage. Large shrinkage can cause cracks due to shrinkage stress in the long term. In this study, a shrinkage reducing agent (SRA) was used to reduce the shrinkage of cement-free mortar; its content was increased from 0.0 to 1.5%. For an SRA content of 1.0%, a calcium sulfoaluminate (CSA) expansive additive (EA) (2.5, 5.0, and 7.5%) was added. To calculate the shrinkage stress of cement-free mortar using the SRA and EA, the compressive strength, elastic modulus, and total and autogenous shrinkage were measured. The unit shrinkage stress of cement-free mortar was obtained by multiplying the elastic modulus by the length change and accumulated to obtain the shrinkage stress acting on the mortar according to the age. The shrinkage stress of cement-free mortar showed different tendencies as the age increased. At early ages, the shrinkage rate of the mortar occupied a large proportion of the shrinkage stress. In the long term, the shrinkage stress was significantly affected by the elastic modulus. As a result, SRA was found to be effective in reducing the shrinkage stress by decreasing both the elastic modulus and shrinkage. However, EA increased the shrinkage stress over the long term due to an increase in the elastic modulus even though it compensated for early-ages shrinkage.

New cold-bonded artificial aggregate using a Ba(OH)2-activated cementless binder for cement-free concrete production

This study introduces cold-bonded cementless artificial aggregates using a Ba(OH)2-activated GGBFS binder system through a pelletization technique to produce complete cement-free concrete as an engineering application. The developed aggregate offers mechanical properties, achieving 10.8 MPa bulk crushing strength at 28 days and satisfying the requirements of lightweight aggregates according to EN 13055. Additionally, it complies with TCLP regulations, demonstrating excellent leaching resistance. The complete cement-free concrete was produced using the developed aggregate, demonstrating promising mechanical properties, exceeding 64.5 MPa compressive strength and 35.5 GPa elastic modulus, greater than previous studies. Economic analysis revealed a production cost of approximately USD 60.85/ton. Regression analysis identified a strong correlation (R2 = 0.9979) between disk revolving speed and diameter, enabling efficient production scaling across different scales (lab-scale, semi-pilot, and pilot). This research paves the way for a sustainable, cement-free, and natural aggregate-free concrete, achieved through the introduction of an eco-friendly, high-performance cold-bonded artificial aggregate and cementless binder that preserves mechanical integrity while delivering significant sustainability values.

Research on cement-free composites based on alkaline-activated waste materials

The article presents a review of research conducted on cement-free concretes based on alkaline-activated waste materials. Research is conducted in order to create concretes that are in line with the doctrine of sustainable development. Their main assumption is the reuse of recycled materials in newly produced building materials without compromising their properties. In addition, attempts are made to eliminate Portland cement, replacing it partially or completely with fly ashes or metakaolin. Another modification of concrete consists of replacing natural aggregate with artificial aggregate. The research conducted on lightweight concretes based on fly ashes, and alkali-activated porous ash aggregate is also presented.

Investigation on enhancing the mechanical properties of Alkali-Activated concrete based on fly ash with wollastonite

Alkali-activated concrete (AAC) is one of the cement-free concretes. It has attracted attention as a notable alternative to conventional Portland Cement Concrete (PCC) due to its superior mechanical properties and environmental benefits. This study investigates the impact of wollastonite, an industrial mineral composed chemically of calcium, silicon, and oxygen, on the mechanical properties of fly ash-based AAC. The compressive strength, split tensile strength and flexure strength at the different liquid-to-binder ratios (such as 0.35, 0.40 and 0.45) are examined. The partial replacement of fly ash with mineral wollastonite powder was carried out at different percentages varying from 5% up to 30%. Samples are cured using both oven curing and ambient curing procedures, and the test results are obtained. In the observation, the best test results are obtained at 20% replacement of fly ash with wollastonite irrespective of liquid-to-binder ratio values. Hence, the AAC with a composition of 20% wollastonite and 80% fly ash has been recognized to have optimum mechanical properties. The findings of this study would largely help to achieve the goals of “zero-waste” production.

Performance evaluation on engineering properties of sodium silicate binder as a precursor material for the development of cement-free concrete

In emerging economies, huge stocks of industrial wastes are dumped in open landfills. Such wastes serve as a source for environmental pollution. Some of these materials such as Fly Ash (FA), Ground Granulated Blast Furnace Slag (GGBFS), Rice Husk Ash (RHA), and Palm Oil Fuel Shell Ash (POFA) can be used as binder materials to produce concrete mix. Aim of the study is to effectively utilize the Municipal Solid Waste (Sodium Silicate Waste (SSW)) powder as a partial replacement for FA in the development of Geopolymer Concrete (GPC). GPC requires heat curing for the attainment of early age strength. The development of GPC under heat curing conditions is a hard process in practice. To overcome such circumstances, an attempt was made to develop the GPC under ambient curing conditions with the aid of SSW. The influence of SSW on strength gain and microstructural characteristics of GPC is investigated. Mechanical properties of GPC such as compressive strength, tensile strength, and flexural strength are reported and discussed. This study focuses on the assessment of mechanical and microstructure characterization of eco-efficient GPC developed with SSW. The required optimum quantity of binder, alkali activator, alkaline liquid to binder ratio and aggregates was determined by appropriate trials. Following the properties of SSW, it is realistic to substitute up to 50% of SSW as the resulting binder mix falls within the requirements of the analyzed mix. Increase in the percentage of SSW decreases the fresh properties of GPC, such as setting time and workability; mix with 50% SSW exhibited the lowest initial and final setting time i.e., 77% and 81% than the control mix. Contrastingly, inclusion of SSW content enhances the mechanical properties of the mix. 12SSW50 mix produces the maximum compressive, tensile and flexural strength of 40.16 MPa, 2.8 MPa, and 4.18 MPa, respectively. Mix with 8 M concentration comprising 50% SSW possess higher cost efficiency than the mix with higher alkaline content. The main significance of this research work is, SSW can be used as a precursor material as an alternative for cementitious binder with better efficiency in terms of strength, microstructure, and sustainability. Therefore, GPC produced with SSW is an eco-friendly and sustainable building material. Effective use of waste materials such as fly ash and SSW for the development of GPC is another major research focus in the proposed investigation.

Optimization of the whole-waste binder containing molten iron desulfurization slag from Kambara Reactor for concrete production

Kambara Reactor desulfurization slag (KRDS) is an alkaline solid waste, which is not properly utilized. The potential applications of KRDS in ground granulated blast-furnace slag (GGBS)-based cementitious materials and cement-free concrete were investigated in this study. An orthogonal test was conducted through range analysis and a multivariate nonlinear regression model to examine the effect of three factors: the GGBS content, KRDS/flue gas desulfurization gypsum (FGDG) ratio, and water/binder (W/B) ratio on the compressive strength of mortar. Next, a cement-free concrete was prepared with different strength grades using the cementitious material at the optimal ratios of raw materials. X-ray diffraction (XRD), thermogravimetry-differential scanning calorimetry (TG-DSC), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS) analysis were carried out to reveal the hydration mechanism of the binder. The factors affecting the strength of the mortar are in this order: GGBS > KRDS/FGDG > W/B. The increase in KRDS enhances the early strength of the binder, but shows an adverse effect on its late strength. The optimum contents of GGBS, KRDS, and FGDG in the binder are 55%, 33.7% and 11.3%, respectively, with a W/B of 0.3. High levels of GGBS lead to an inhibitory effect of KRDS/FGDG on the compressive strength of the concrete. In order to improve the utilization rate and strength of KRDS, the level of GGBS should not exceed 55%. The main hydration products of the binder are needle-like ettringite (AFt) and spherical C-(A)-S-H gels. KRDS dissolution provides a strong alkaline environment, which promotes the disintegration of the Si(Al)–O tetrahedron of GGBS and the formation of the hydration products. C30–C40 concrete exhibit a small 1-h slump loss and good fluidity, making them more suitable for ready mix pumped concrete, whereas C50 and C60 concrete with a large slump loss are more suitable for high-strength precast members. This study has a theoretical and practical significance for a comprehensive utilization of multi-solid waste, energy saving, and carbon-emission reduction.

Effect montmorillonite clay as aggregate in lightweight concrete cement-free

Light weight concrete has many advantages that can be used in the construction of buildings. Perhaps one of the most important of these features is its light weight, which contributes a lot to reducing stress on the soil, which provides the possibility of rising buildings and increasing the number of floors. In addition to its role in thermal insulation and its impact on reducing the consumption of energy sources in cooling and heating, light weight concrete is considered one of the sustainability factors in buildings. One of the second major factors in sustainability is to reduce or avoid the use of cement in the manufacture of this concrete, because of the harmful effects of cement on the environment and global warming. Cement-free concrete is considered a sustainable material in terms of its depletion of the waste materials and spin-off products from different industries apposite of consumption of natural resources in the cement industry (mud, limestone). In this research first aim is to produce lightweight cement-free concrete using pozolanic material and montmorillonite clay as coarse and fine aggregate. Studying some properties of producing light weight concrete (density, compression, tensile,) with different ages (7, 28, 56) days.

Геополимерный бетон с использованием многотоннажных техногенных отходов

Introduction. Currently, in all countries, Portland cement is used as a binder in the production of concrete, and its global production accounts for 10 % of the total carbon dioxide emitted into the atmosphere. Therefore, Portland cement can be partially or fully replaced by new cement-free binders, made of large-tonnage technogenic waste with a cementing effect, for example, by finely ground blast furnace slag, fly ash generated by thermal power plants and ash formed during the combustion of rice hulls. Aqueous alkaline solutions (NaOH and Na2SiO3 or KOH and K2SiO3) should be used as activators of setting and hardening of such binders, and calcium sulfate dihydrate can be used to adjust the setting time. Concrete containing new cement-free binders is called geopolymer concrete. Materials and methods. In order to reduce mixing water consumption and maintain the required workability of the fine-grained concrete mixture, a polycarboxylate superplasticizer was introduced into its composition. All raw materials, except for the superplasticizer, were of the Vietnamese origin. The following research methods were used: the composition of the geopolymer concrete mixture was analyzed using the absolute volume method, the workability of the concrete mixture was determined according to ASTM C1611-18 и TCVN 3106:2007, compressive and tensile strength of the concrete, subjected to bending, were tested pursuant to GOST 10180-2012, and the average density of concrete was tested according to GOST 12730.1-78. Results. The co-authors have developed the composition of the geopolymer concrete containing the alkaline cement-free binder. As a result of the heat treatment of the 28-days-old concrete for 6 hours at 100 °C, its compressive strength reaches about 60 MPa; hence, it can be used in the hot and humid climate of Vietnam. Conclusions. This cement-free concrete, in addition to its high strength, has good water resistance and low water absorption. This concrete has economic benefits, and its production will help to protect the environment due to the lower consumption of natural resources and the applicability of large-tonnage technogenic waste.

Environmental impact of cement production and Solutions: A review

This paper reviews the impact of cement industry towards the global environment and solutions to the problem. The increasing harvesting of raw materials for mounting cement manufacturing causes reduction in quantity of the non-renewable resources such as limestone. The activities linked to harvesting of the resources from natural surroundings, damages the green landscape which is the habitat of flora and fauna exposing to the risk of ecological imbalance. The continuous reaping of these precious resources, exposes it to the risk of depletion in future. Furthermore, the raw materials processing phases in the factory releases dust, noises, greenhouse gases especially carbon dioxide that contaminates the environment and aggravates the climate change. These uninvited environmental issues cause distress to the lifestyle of mankind. Therefore, enhancing the manufacturing technology of cement plant for cleaner production is one of the resolutions to this issue. Approach of using industrial waste as supplementary cementitious material or cement free concrete also would reduce dependency on cement demand. Success in utilizing other alternative material which production consumes lesser natural resources, economic and has lesser harm to the nature to act as binder in concrete would contribute to sustainable and healthier environment for future generation.

Industrial solid waste management through sustainable green technology: Case study insights from steel and mining industry in Keonjhar, India

The generation of industrial solid waste is increasing at an alarming rate worldwide and landfilling is no longer a feasible method for managing various industrial solid wastes. However, recent developments in environmental policies have led to many sustainable approaches towards integrated solid waste management. Industrial waste refers to the waste produced with the aid of industrial activity comprising of materials deemed useless in the production process of factories, mills, industries, and mining activities. This paper primarily focuses on waste management strategies adopted by industries: Iron & steel, mining respectively for cleaner production and sustainable development through effective utilization of solid waste in the construction industry especially in geopolymer concrete. The 21st-century demand's low carbon cement-free concrete for smart infrastructures. Geopolymer concrete, a third-generation construction material serves in effectively utilizing various industrial solid wastes generated by steel and mining industries. Short case studies have been carried out to discuss the response from the steel industry and mines towards sustainable development and waste management following the usage of GGBFS for production of geopolymer concrete thus encouraging further debate on progressive waste management strategies for a greener future.

Cement-Free Refractory Concretes. Part 1. General Information. Hcbs and Ceramic Concretes

The general nature of the dependence of engineering and service characteristics of refractory concretes with an average cement content, and also low-cement (LCRC), ultra-low cement (ULCRC) and cement-free (CFRC), on the content of CaO (or HAC) in them is analyzed. Significant advantages of cement-free concretes are the reduced moisture content of the concrete mixture, which determines their increased density, a continuous increase in strength (absence of a softening temperature range typical for LCRC and ULCRC), and improved thermomechanical and operational characteristics. With use of CFRC, the insurmountable complexity of the LCRC and ULCRC connected with their initial heating in the dehydration temperature range of the HAC (up to 450°C) is resolved. The main provisions and stages of creating HCBS or artificial ceramic binders as a matrix system of ceramic concrete, i.e., LCRC with improved characteristics, are described. Classification of HCBS groups proposed by the author based on the chemical nature of their solid phase is considered.

Cupola Furnace Slag: Its Origin, Properties and Utilization

A cupola furnace is the most frequently used furnace aggregate for cast iron production. A by-product of the production of cast iron in cupola furnaces is cupola slag. Its amount is 40–80 kg per 1 tonne of the produced cast iron, and that is one of the reasons why this material is not as favoured as, for example, the blast-furnace slag. The purpose of this article is to provide the basic information on the formation of slag in a cupola furnace, and its chemical composition, structure and current potential applications. The greatest potential for the use of cupola slag is in the building industry; therefore, a section of the present article deals with the property that plays an important role particularly with regard to the use of slags in the building industry, i.e. the slag hydraulicity. The achieved results indicate that the hydraulicity of the cupola slag is incomparable with the hydraulicity of the blast-furnace slag; this may be associated with the problems that arise when the slag of this type is used in the building industry. The authors used the air-cooled as well as granulated slags from cupola furnaces in the production of concrete that was made from the slags alone. While the air-cooled slag may be used as a partial replacement for the blast-furnace slag in concrete mixtures, the use of granulated slag from cupola furnaces as a replacement for granulated blast-furnace slag in cement-free concrete has not proven to perform well.

Strength and heat generation of concrete using carbide lime and fly ash as a new cementitious material without Portland cement

The aim of this paper is to investigate mechanical properties and heat generation of concrete produced with a carbide lime (CL) and fly ash (FA) mixture as a new cementitious material without Portland cement. Two techniques were used to improve the strength of concrete: adding of NaOH into the new binder (1% by weight) and increasing the fineness of new binder. Microstructural mechanism in term of SEM microscopy, EDX analysis, and XRD patterns of CL-FA pastes were examined. The following properties of cement-free concrete were also examined: heat generation, compressive strength, elastic modulus, and splitting tensile strength. The results of microstructural revealed that the products of binder made from CL and FA were C-S-H and C-A-S-H phase types and the formations of C-S-H and/or C-A-S-H were attributed to components of Al, Si, and Ca. The results also showed that the peak temperature rise of concrete made from CL and FA could be reduced by 30–36 °C from that of the OPC concrete. Regarding the mechanical properties of concrete, the technique of improving strength by increasing the fineness of new cementing material was the best method and could produce the 28-day compressive strength of 55.0 MPa. CL-FA concrete had elastic modulus and tensile strength similar to those of OPC concrete. Furthermore, the techniques to improve the strength of concrete had no significant effect on the elastic modulus and tensile strength of concrete since those properties were related to the compressive strength of concrete. Moreover, the concrete had a very low heat generation as compared to the OPC concrete.

High-Strength, Cement-Free Concrete of Flue Gas Desulfurization Gypsum-Based Non-Fired Brick

High-Strength, Cement-Free Concrete of Flue Gas Desulfurization Gypsum-Based Non-Fired Brick

Development of High Strength Fly Ash based Geopolymer Concrete with Alccofine

The production of Ordinary Portland cement concrete causes havoc to the environment due to the emission of CO2 in the production of cement as well as mining which results in unrepairable damage to nature. Geopolymer concrete, a cement free concrete is an innovative green concrete in which binding properties are developed by the interaction of alkaline solutions with a source material that is rich in silica and alumina. Fly Ash, a byproduct of coal obtained from the thermal power plant is rich in silica and alumina which on reacting with alkaline solution produces aluminosilicate gel that acts as the binding material for the concrete. Geopolymer concrete develop high compressive strength on heat curing promising to be an ecofriendly substitute for ordinary Portland cement concrete in some applications. This paper briefly put the light on the development of high strength geopolymer concrete with the help of Alccofine which is a micro fine GGBS based material.

A Study on the Preparation Method of Geopolymeric Concrete using Specifically Modified Silicate and Inorganic Binding Materials and Its Compressive Strength Characteristics

Recently, research on geopolymeric concrete that does not use cement as a binder has been actively investigated. Geopolymeric concrete is cement-free concrete. Masato, ocher and/or soil has been solidified into geopolymeric concrete by the reaction of specifically modified silicate as an alkali activator and inorganic binding materials such as blast furnace slag, fly ash or meta-kaolin, which is cured at room temperature to exhibit high compressive strengths. Based on the results, this study shows how geopolymeric concrete that uses specifically modified silicate and inorganic binding materials is implemented as eco-cement with no cement.

Cement-Free Mortar Using Ground Granulated Blast-Furnace Slag with Different Alkali-Activators

The present study concerns a development of cement-free concrete using ground granulated blast-furnace slag (GGBS) with alkali-activators such as KOH, NaOH, and Ca (OH)2. To find out the development among three different activators, the concentration of hydroxyl ion was kept 0.5%, 1.0%, 1.5%, 2.0% and 3.0% by weight of binder irrespective of cations. The setting time was measured by penetration resistance immediately after casting of mortar. The development of compressive strength was measured at 7, 14, 28, and 91 days. The pore structure of cement-free mortar was examined by the mercury intrusion porosimetry (MIP) and rapid chloride penetration test (RCPT). Simultaneously, grew sample was used to microscopically observe at the XRD. For strength of cement-free mortar, mixed with KOH or NaOH was as high as OPC at 3.0 % by weight of binder. However, the compressive strength of cement-free concrete mixed with 3.0 % Ca (OH)2 by weight of binder had just half strength of OPC mortar. Cement-free concrete activated with NaOH and Ca (OH)2 had higher total pore volume, however, it had lower ionic penetrability due to the pore type which mostly consist of gel pores. For pore structure of cement-free mortar mixed with KOH, the total volume had similarity to that of OPC mortar, however, it had lower penetrability. Therefore, it may have higher resistance to chloride transport than that of OPC mortar.

Development of Cement-Free Concrete Using Finely Grained Slag for Portland Cement

Abstract. The present study concerns a development of cement-free concrete using finely grained ground granulated blast furnace slag (GGBS) rather than ordinary Portland cement (OPC) as a binder in concrete mix. The GGBS was very finely ground to the level of 10,000 cm2/g, prior to casting concrete, compared to OPC of which the Blaine value accounts for about 3,200 cm2/g. In concrete casting, the NaOH activator was added to mixing water to enhance the hydration rate for cement-free concrete. To ensure the compatibility of GGBS in concrete, a development of concrete strength, ionic penetrability and pore structure were examined. As a result, it was found that cement-free concrete using the GGBS has a higher concrete strength at all ages from 7 to 56 days. In turn, the ionic penetrability, in terms of chloride diffusivity, was slightly lower in cement-free concrete than OPC concrete, presumably due to the dense pore structure, which was confirmed by the mercury intrusion porosimetry. Simultaneously, the adiabatic temperature for cement-free concrete initially rose more rapidly, leading to an accelerated hydration process. This suggests that the cement-free concrete containing GGBS can be used for structural concrete structures, imposing an economical benefit and structural stability.

Periclase concretes based on a silicate binder

OOO Gruppa Magnezit has developed a new generation of periclase cement-free concretes based on a MgO–SiO2 binder with a service temperature from 1500 to 1700°C depending on filler composition. The technology assimilated makes it possible to prepare refractories of complex shape for lining elements of CBCM intermediate ladles and other units.