Hybrid One-Part alkali activated binder: impacts of activator dosage on fresh and hardened properties

The production of cement requires significant energy and is responsible for more than 5% of global CO2 emissions; therefore it is imperative to reduce the production and use of ordinary portland cement (OPC). This paper examines the compressive strength development of low water-to-binder (w/b) ratio self-consolidating concrete (SCC) in which 90% of the cement is replaced with industrial by-products including ground granulated blast furnace slag (GGBS), fly ash, and silica fume. The emphasis in this paper is on replacing a large volume of cement with GGBS, which represented 10% to 77.5% of the cement replaced. Fresh properties at w/b ratio of 0.27 were examined by estimating the visual stability index (VSI) and t50 time. The compressive strength was determined after 3, 7, 28, and 56 days of curing. The control mix made with 100% OPC developed compressive strength ranging from 55 MPa after three days of curing to 76.75 MPa after 56 days of curing. On average, sustainable SCC containing 10% OPC developed strength ranging from 31 MPa after three days of curing to 56.4 MPa after 56 days of curing. However, the relative percentages of fly ash, silica fume, and GGBS in the 90% binder affect the strength developed as well. In addition, this paper reports the effect of the curing method on the 28 day compressive strength of environmentally friendly SCC in which 90% of the cement is replaced by GGBS, silica fume, and fly ash. The highest compressive strength was achieved in samples that were cured for three days under water, then left to air-dry for 25 days, compared to samples cured using chemical compounds or samples continuously cured under water for 28 days. The study confirms that SCC with 10% OPC and 90% supplementary cementitious composites (GGBS, silica fume, fly ash) can achieve compressive strength sufficient for many practical applications by incorporating high amounts of GGBS. In addition, air-curing of samples in a relatively high temperature (after three days of water curing) produce a higher 28 day compressive strength compared to water curing for 28 days, or membrane curing.

Effect of nano silica on compressive strength and microstructures of high volume blast furnace slag and high volume blast furnace slag-fly ash blended pastes

Optimum mix design of geopolymer pastes and concretes cured in ambient condition based on compressive strength, setting time and workability

Development of sustainable concrete using recycled coarse aggregate and ground granulated blast furnace slag

Seawater can be used as mixing water for concrete with no steel reinforcement in some areas with difficult access to fresh water. Diatoms such as Phaeodactylum tricornutum are among the most abundant micro-organisms living in seawater, and they could be unavoidable when collecting seawater. In fact, diatoms can provide bio-SiO2 and bio-CaCO3 sources, namely amorphous nano-SiO2 and crystallised nano-CaCO3, which could be beneficial to cement hydration. Thus, the effects of different Phaeodactylum tricornutum concentrations (0%, 2.5% and 5% by weight of suspension of seawater and diatoms) in seawater on cement hydration in ordinary Portland cement (OPC) mixes (100% OPC) and ground granulated blast-furnace slag (GGBS) mixes (70% OPC + 30% GGBS) were investigated through tests of compressive strength, XRD, DTG–DTA and SEM. The results show that diatoms accelerated cement hydration by providing the nucleus for C-S-H structure and contributed pozzolanic reactions by amorphous nano-SiO2 and nano-CaCO3. The accelerated cement hydration was also confirmed by the fact that more Ca(OH)2 was formed in cement pastes with diatoms. However, it has also been found that diatoms decreased the compressive strength of cement pastes by leaving more weak bonds between the C-S-H structure, which was considered to be caused by the organic parts and the micron gap formed in diatoms. When comparing an OPC paste mix with 5% diatoms to a blank OPC paste, the reduction in compressive strength at 28 days can reach a maximum of 50.1%. The ability to provide bridging effects between C-S-H particles in GGBS paste was discovered to depend on the development of additional ettringite. This resulted in a 7.6% loss in compressive strength after 28 days in a GGBS paste with 5% diatoms.

The depletion of natural resources and the substantial carbon emissions associated with ordinary Portland cement (OPC) production pose critical environmental challenges to the construction sector. This study investigates the development of a sustainable quaternary blended cement system incorporating steel and iron industry by-products, i.e. Linz-Donawitz slag (LDS), ladle furnace slag (LFS), and ground granulated blast furnace slag (GGBFS), in combination with OPC. Binder pastes were formulated with varying proportions of LDS and LFS, while maintaining OPC at 50% and GGBFS at 10% by mass. The blended systems were comprehensively evaluated with respect to mechanical performance, durability in aggressive environments, phase assemblage, microstructural characteristics, and thermogravimetric behaviour. The optimised composition, consisting of OPC (50%), GGBFS (10%), LDS (20%), LFS (20%), and 10% chemical activator, achieved a 28-day compressive strength of 62.9MPa, significantly surpassing the OPC control (53.4MPa). Microstructural and mineralogical analysis confirmed the formation of a dense and homogeneous calcium silicate hydrate (C-S-H) gel network, consistent with thermogravimetric findings indicating enhanced hydration and reduced portlandite content. Durability assessment of the optimised mix demonstrated superior resistance to exposure to MgSO₄ and HCl. The control mix showed weight changes of 0.70% and 0.64% in the presence of MgSO4 and HCl, respectively, while the optimised mix exhibited the lowest gains at 0.45% and 0.49%, respectively. Furthermore, exposure to sulphate and acid solutions reduces strength. The control mix exhibited strength losses of 6.37% and 9.55% under sulphate and acid exposure, whereas the optimised mix demonstrated comparatively lower reductions of 1.74% and 5.08%, respectively. The ingress of sulphate and chloride ions from the MgSO4 and HCl solution into the pore structure of the binder matrix initiates chemical reactions with the calcium hydroxide and monosulphate phases, leading to the formation of expansive products, such as gypsum and ettringite. Although a marginal increase in drying shrinkage of the optimised mix (0.038%) compared with the control (0.034%) was observed, the overall durability performance remained superior to that of conventional OPC systems. The optimised blends met the requirements of Indian and ASTM standards for OPC 43-grade cement, confirming their technical viability for practical implementation. Beyond performance improvements, the study highlights significant sustainability and economic implications. Partial substitution of clinker with steel and iron slags reduces embodied CO₂ emissions, diverts industrial by-products from landfills, and advances circular economy principles within the construction industry. While initial production costs are comparable to conventional OPC due to supplementary cementitious material processing, lifecycle benefits, including reduced clinker demand, improved durability, extended service life, and potential environmental incentives, enhance overall cost-effectiveness. In conclusion, this research establishes steel and iron slags as viable constituents in high-performance quaternary blended cements. By demonstrating enhanced strength, improved durability, regulatory compliance, and environmental benefits, the study provides a practical pathway for lowering the carbon footprint of cementitious materials.

This research represents experimental work for investigation of the influence of utilising Ground Granulated Blast Furnace Slag (GGBS) and High Calcium Fly Ash (HCFA) as a partial replacement for Ordinary Portland Cement (OPC) and produce a low carbon cementitious material with comparable compressive strength to OPC. Firstly, GGBS was used as a partial replacement to OPC to produce a binary blended cementitious material (BBCM); the replacements were 0, 10, 15, 20, 25, 30, 35, 40, 45 and 50% by the dry mass of OPC. The optimum BBCM was mixed with HCFA to produce a ternary blended cementitious material (TBCM). The replacements were 0, 10, 15, 20, 25, 30, 35, 40, 45 and 50% by the dry mass of BBCM. The compressive strength at ages of 7 and 28 days was utilised for assessing the performance of the test specimens in comparison to the reference mixture using 100% OPC as a binder. The results showed that the optimum BBCM was the mix produced from 25% GGBS and 75% OPC with compressive strength of 32.2 MPa at the age of 28 days. In addition, the results of the TBCM have shown that the addition of 10, 15, 20 and 25% of HCFA to the optimum BBCM improved the compressive strength by 22.7, 11.3, 5.2 and 2.1% respectively at 28 days. However, the replacement of optimum BBCM with more than 25% HCFA have showed a gradual drop in the compressive strength in comparison to the control mix. TBCM with 25% HCFA was considered to be the optimum as it showed better compressive strength than the control mix and at the same time reduced the amount of cement to 56%. Reducing the cement content to 56% will contribute to decrease the cost of construction materials, provide better compressive strength and also reduce the CO2 emissions into the atmosphere.

The major problem the world is facing today is the environmental pollution. In the construction industry mainly the production of Portland cement will causes the emission of pollutants results in environmental pollution. We can reduce the pollution effect on environment, by increasing the usage of industrial by-products in our construction industry. Geo- polymer concrete is such a one and in the present study, to produce the geo-polymer concrete the Portland cement is fully replaced with GGBS (Ground granulated blast furnace slag) and Metakaolin and alkaline liquids are used for the binding of materials. The alkaline liquids used in this study for the polymerization are the solutions of Sodium hydroxide (NaOH) and sodium silicate (Na2Sio3) of A53 which consists of SiO2 = 29.4%, Na2O = 14.7%, and water = 55.9% by mass is used. 10Molar Sodium hydroxide is taken for the preparation of different mixes by varying the percentages of GGBS (Ground granulated blast furnace slag) and Metakaolin. The cube specimens are taken of size 150mm x 150mm x 150mm for compression test. The curing was done directly by placing the specimens to direct sunlight. The geo- polymer concrete specimens are tested for their compressive strength at the age of 3, 7 and 28days and compared with conventional concrete. For this study M30 concrete mix was used for experimental work. The result shows that there is an increase in the strength of Geopolymer concrete up to 40%GGBS content and then it is decreasing. Therefore it is preferable to use 40%GGBS with Metakaolin to get high strength. Metakaolin and GGBS can be used as a replacement material for cement gives an excellent result in strength aspect and quality aspect since it is better than the control concrete. Key Words: Geopolymer concrete, GGBS, Metakaolin, Alkaline solutions, curing, compressive strength.

One-part alkali-activated materials (AAMs) are developed to improve conventional two-part systems. One-part AAMs technology has been used in cement binders to produce concrete, mortar, and paste. Current research mainly focuses on synthesizing raw materials obtained from industrial and agricultural waste as the main aluminosilicate precursors of the cement binder for a concrete application. The one-part AAMs were reported to have higher early compressive strength at 7 days of age, contributed by its fast-setting time, mainly when the binder activates by a higher dosage of alkaline activator and containing OPC-rich. Due to bonding issues, single or combination, FA/GGBFS/MK precursors were reported as unsuitable for use as a concrete repair material. They were the reason for the lack of one-part AAMs application of mortar compared to concrete usage. This study was conducted to determine the potential of one-part AAMs used as concrete patch mortar by investigating its rheology and mechanical properties. The compressive strength of the mortar was tested under lab ambient temperature in the tropical climate country of Malaysia. The setting time of fresh mortar and bonding strength were set under controlled lab temperature. The one-part alkali-activated mortar was composed of hybrid aluminosilicate precursors between fly ash (FA), Ground Granulated Blast Furnace Slag (GGBFS) and ordinary Portland cement (OPC). A low alkaline activator of solid potassium carbonate was used for the geopolymerization process. Three types of solid admixtures were added to complete the composition of the new mix design. The experiment's outcome showed that the mortar composed with the combination of conventional Portland cement and industrial waste products has compressive and pull-off adherence strength that meets with Class R3—EN1504-3 standard for structural concrete repair materials requirement.

This study focused on evaluating the resistance of 300°C-autocalved alkali-activing Class F fly ash (FAF)-rich Type II Ordinary Portland Cement (OPC) blends with 80/20 and 90/10 FAF/OPC ratios to five thermal-shock (TS) fatigue cycles (one cycle, 600°C heat – 25°C water quenching). The factors to be evaluated included the hydration behaviors, crystalline/ amorphous phaseidentifications, -compositions and -transformations, and microstructural-developments andalterations for blended cements assembled by three different alkaline activators, sodium metasilicate (SMS), soda ash (SA), and sodium sulfate (SS). All factors were related directory to the changes in compressive strength after TS testing. The setting time of cement slurries at 25° and 85°C depended on the alkaline activators; SMS and SA contributing to a strong alkalinity hastened setting, while SS with moderate alkalinity extended the setting time. A more prolonged setting time was observed from non-activated cement. In this case, there were two separated hydration reactions: The first reaction was the hydration of OPC; the second one was associated with the dissolution and pozzolanic activity of FAF. In contrast, all alkali- activated cements engendered the concomitant hydration of OPC and FAF, thereby conferring a higher compressive strength on them than that of the non-activator one. The principal contributor to the development of strength of both the non-activated and activated cements at 300°C was the amorphous NaO₂ - or CaO-Al₂O₃ - SiO₂ -H₂O (N,C-A-S-H) phase formed by the interactions between alkaline activator, OPC, and FAF. This phase played an important role in minimizing the loss in strength after TS. On the other hand, adding SMS and SA introduced the mixed crystalline FAF-OPC hydrates, such as garranite and wairakite, as the major phases, into the autoclaved cement bodies. Also, these activators induced the formation of two FAF-related crystalline hydrates, analcime as the major phase and riversidelite (0.9 nm tobermorite) as the minor one. However, these identified phases were sensitive to TS, so converting the major phases into minor phases or vanishment. In contrast, three crystalline phases including calcite and anhydrous sodium sulfate as the major ones and 1.1 nm tobermorite as the minor one, that formed in non-activated and activated cements remained unchanged after TS. Additionally, SAactivated cement revealed porous microstructure created by the incorporation of copious amount of carbonate reaction products into the cement, raising concerns that cements might enhance the rate of water transportation and reduce compressive strength. Nevertheless, TS-insensitive amorphous N,C-A-S-H phase as the major cementitions structure coexisting with TS-insensitive crystalline products were responsible for sustaining the integrity of alkali-activated FAF-rich OPC cement systems in such harsh heat-cooling fatigue environments.

Stabilization of iron ore tailing with low-carbon lime/carbide slag-activated ground granulated blast-furnace slag and coal fly ash

Effect of slag and solid activator on flowability and compressive strength of fly ash based one-part geopolymer pastes

The mechanical strength and durability of eco-friendly mortars used in the repair of marine concrete structures exposed to freshwater and seawater environments were evaluated in this paper. The eco-friendly mortar samples were produced using various ratios of fly ash (FA), ground granulated blast-furnace slag (GGBFS), and silica fume (SF) as cementitious materials. Seven mixtures of eco-friendly mortars, including a control mixture; three mixtures with respective substitutions of GGBFS for Portland cement of 10, 20, and 30% by cement mass; and three mixtures with respective additions of SF of 5, 10, and 15% by total binder mass, were used to produce the samples. Tests, including compressive strength, flexural strength, ultrasonic pulse velocity (UPV), electrical surface resistivity (ESR), rapid chloride ion penetration (RCP), thermal conductivity (TC), and microstructure analysis, were conducted to determine the mechanical strength and durability values of the samples. The experimental results show that replacing Portland cement with GGBFS negatively affected the properties of the mortars by reducing the mechanical strength, UPV, ESR, and TC while increasing the RCP in the samples. Also, adding an appropriate amount of SF could improve the mechanical strength and durability characteristics of the eco-friendly mortars. As a result, the mortar sample containing 30% GGBFS and 10% SF earned compressive and flexural strength values of approximately 49.2 and 13.8 MPa, respectively, at 56 days of curing age. Mortar samples with UPV values >3660 m/s were identified as “high quality”. The corrosion resistance of all of the samples was found to be high, particularly in chloride-contaminated environments, due to relatively low (1000 - 2000 Coulombs) RCP values. The best overall performance was recorded for the sample containing 30% GGBFS and 10% SF.

Ordinary Portland cement (OPC) is one of the most widely used construction materials in civil engineering infrastructure construction but it is susceptible to sulfate attack. One of the ways to improve the sulfate resistance of an OPC mortar/concrete is to replace a certain amount of OPC with different pozzolanic materials such as ground granulated blast furnace slag (GGBFS) and metakaolin. The use of pozzolanic materials to mortar/concrete not only enhances durability but also reduces carbon dioxide (CO2) emission due to the less usage of OPC at the initial construction state. As considering these aspects, limestone calcined clay cement (LC3) has been developed in recent decades. However, the influence of LC3 on sulfate attack resistance has not been fully evaluated. Therefore, this study investigated the efficiency of LC3 mortar mixtures against sulfate attack at an early age (approximately 4.5 months) after two different curing periods, namely 1-day and 3-day curing, since the strength of the LC3 mixture is lower than OPC mixtures. To evaluate the synergistic effect of a combination of LC3 and GGBFS on the sulfate resistance, the LC3 and OPC mixtures containing 25% GGBFS were also assessed in terms of density, porosity, compressive strength, volumetric expansion, and weight changes. The experiment results show that the expansion of the LC3 mixture regardless of the addition of GGBFS and an initial curing strength made a plateau after a rapid increase up to 7 days, while the expansion of the OPC mixture kept increasing throughout the period. Furthermore, the addition of GGBFS to OPC or LC3 mixture provides the synergistic effect on reducing the expansion due to sulfate attack. Therefore, if LC3 mixture has high initial strength (min. 15 MPa) and dense microstructure to minimize the penetration of sulfate ion into the mixture, it is expected that LC3 mixture is more efficient than OPC mixture against the sulfate attack.

This paper presents the results of an experimental investigation on strength development and chloride resistance of low-reactivity ground granulated blast furnace slag (GGBFS) incorporated concretes. Fine and coarse GGBFS samples were used to replace the Portland cement at 20 %, and a series of tests were conducted to investigate the effects on conventional and high strength concretes. Compressive strength, RCMT, RCPT and electrical resistivity tests were carried out at different ages up to 180 days. Furthermore, half-cell potential test was conducted weekly on steel reinforced specimens exposed to wet–dry cycles for 30 weeks. The results imply that despite the low activity index of the local GGBFS, it could be used at low levels of Portland cement replacement. Of note, however, is that despite its positive effect on the chloride resistance of concrete, a reduction in compressive strength (mainly at early ages and for conventional concrete mixes) should be expected. Furthermore, the test results indicate that increasing fineness of low-reactivity local GGBFS (within the studied range) does not lead to higher resistance of concrete against chloride attack.