Ultrafine Slag Research Articles

Dynamic mechanical properties and microstructure of ultrafine slag powder cement paste utilizing solid waste industrial tailings powder and fly ash

Ultrafine slag powder cement paste (USP-CP) is a promising green cementitious material with excellent mechanical properties and environmental benefits. In this study, the effects of elemental molar ratios in raw materials (n(Si)/n(Al) ranged from 1.2 to 1.4 with a gradient of 0.1; n(Fe)/n(Al) ranged from 0.15 to 0.21 with a gradient of 0.03; and n(S)/n(Al) ranged from 0.20 to 0.28 with a gradient of 0.04.) on the workability, mechanical properties, and microstructure of USP-CP were investigated. The main products of USP-CP are α-SiO2, AFt, gypsum, and α-C2SH. The molar ratio of Si/Al has the greatest influence on workability, while the molar ratio of S/Al has the greatest influence on setting time. For mechanical property tests, higher USP content can improve the early compressive strength of USP-CP, while its long-term compressive strength is affected by the anhydrous calcium sulfate (CaSO4) content. Specifically, when the molar ratios of Si/Al, Fe/Al, and S/Al are 1.2, 0.21, and 0.24, respectively, the 28-day dynamic and static compressive strengths of USP-CP specimens reach the maximum values, which are 121.3 MPa (321/s) and 42.0 MPa (10-2/s), respectively. Furthermore, the static compressive strength is comparable to that of pure cement of the same grade.The molar ratio of S/Al has a more significant effect on dynamic compressive strength than static compressive strength. The excessive increase of Na and Si elements in the alkaline activator inhibits the dynamic mechanical enhancement performance of USP-CP. This study provides theoretical and practical reference value for the application of USP in impact-resistant structural materials and static load-bearing materials. It also fully utilizes waste materials to reduce the use of cement and achieves environmental benefits of carbon reduction.

Effect of printing parameters on extrudability and buildability of ultra-low carbon cementitious material

Cement-free cementitious materials are important for reducing the carbon footprint of 3D printing. However, for the ultra-low carbon cementitious material for 3D printing, the effect of printing parameters on its extrusion and stacking morphology has not been fully investigated. In this paper, an ultra-low carbon cement-free cementitious material (UCCCM) with ultra-fine slag and spherical fly ash as main components is developed. The influence of print head size (HS), print head height (HH), and printing speed (PS) on the extrudability and buildability are systematically investigated. Results showed that the HS had a clear influence on the extrudability, and a small print head size negatively affected the continuity of the extrudate. The HH had a greater influence on the buildability, and a low HH led to a height loss rate of more than 5 %. The PS had a greater influence on the buildability. When the PS was too slow, the mortar piled up and the printed specimens collapsed with a height loss rate of up to 35 %. When the PS was too fast, the strip cracked, and the height loss rate reached more than 10 %. The developed UCCCM for 3D printing presented optimal extrudability and buildability at a HS of 20 mm, a HH of 90 % and a PS of 20 mm/s.

Probabilistic Corrosion-free Service Life of the RCC Structures Made with OPC and Ultra-fine Slag-based Binders

The primary factor in the deterioration of reinforced concrete is chloride-induced corrosion. It has a direct impact on the service life of the structure and has been the subject of much research over the past 5 decades. One of the most cost-effective ways to lessen chloride-induced corrosion was identified to be the use of more supplementary cementitious material (SCM). Moreover, when SCMs are ground down to a smaller size, the resulting particles serve as microfillers, which have a significant impact on the improvement of mechanical properties and durability. This paper highlights the influence of grinding slag into an Ultra Fine Slag (UFS) on chloride ion penetration in the mortar specimen. A bulk diffusion test was performed on a mortar replaced with UFS which show a synergic reduction in chloride diffusivity in comparison with control mixes. In addition, an attempt is made on prediction of probabilistic service life estimation by Error function model.

Strength evolution and microstructure of alkali-activated ultra-fine slag in low-temperature environments

At low temperatures, the hydration rate of Portland cement significantly slows down, resulting in a decrease in its strength. Additionally, the pore solution freezes easily. As a kind of low-carbon cementitious material, alkali-activated slag (AAS) material has a short setting time at room temperature and a high early strength, meanwhile the alkali solution does not freeze at low temperatures. This study investigates the evolution mechanism of the strength and microstructure of AAS pastes cured at 0℃. Slag with different fineness was activated by a sodium silicate solution with different moduli, whose strength was compared with that of an AAS paste cured at 20 °C. The setting time, compressive strength, hydration process, pore structure, freezing point, and microstructure of the AAS paste were studied, whose results showed that the setting time of the AAS paste was obviously prolonged, and the compressive strength decreased under low-temperature curing. After the activation of slag ground, the early compressive strength of the AAS paste was significantly improved, whose reason was that the hydration degree of the paste was improved after slag ground, and that a dense pore structure was formed. The freezing point of the AAS paste was approximately −26 °C, which, remarkably, even at −40 °C, was still capable of undergoing a weak chemical reaction, producing an exothermic enthalpy. This characteristic makes alkali-activated ultrafine slag a highiy-promising cementitious material for curing at low temperatures.

Influence of Ultrafine Fly Ash and Slag Powder on Microstructure and Properties of Magnesium Potassium Phosphate Cement Paste.

This study investigated the influences of ultrafine fly ash (UFA) and ultrafine slag powder (USL) on the compressive strengths, autogenous shrinkage, phase assemblage, and microstructure of magnesium potassium phosphate cement (MKPC). The findings indicate that the aluminosilicate fractions present in both ultrafine fly ash and ultrafine slag participate in the acid-base reaction of the MKPC system, resulting in a preferential formation of irregularly crystalline struvite-K incorporating Al and Si elements or amorphous aluminosilicate phosphate products. UFA addition mitigates early age autogenous shrinkage in MKPC-based materials, whereas USL exacerbates this shrinkage. In terms of the sustained mechanical strength development of the MKPC system, ultrafine fly ash is preferred over ultrafine slag powder. MKPC pastes with ultrafine fly ash show greater compressive strength compared to those with ultrafine slag powder at 180 days due to denser interfaces between the ultrafine fly ash particles and hydration products like struvite-K. The incorporation of 30 wt% ultrafine fly ash enhances compressive strengths across all testing ages.

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.

Development and application of novel high‐efficiency composite ultrafine cement grouts for roadway in fractured surrounding rocks

AbstractThe fractured surrounding rocks of roadways pose major challenges to safe mining. Grouting has often been used to reinforce the surrounding rocks to mitigate the safety risks associated with fractured rocks. The aim of this study is to develop highly efficient composite ultrafine cement (CUC) grouts to reinforce the roadway in fractured surrounding rocks. The materials used are ultrafine cement (UC), ultrafine fly ash (UF), ultrafine slag (US), and additives (superplasticizer [SUP], aluminate ultrafine expansion agent [AUA], gypsum, and retarder). The fluidity, bleeding, shrinkage, setting time, chemical composition, microstructure, degree of hydration, and mechanical property of grouting materials were evaluated in this study. Also, a suitable and effective CUC grout mixture was used to reinforce the roadway in the fractured surrounding rock. The results have shown that the addition of UF and US reduces the plastic viscosity of CUC, and the best fluidity can be obtained by adding 40% UF and 10% US. Since UC and UF particles are small, the pozzolanic effect of UF promotes the hydration reaction, which is conductive to the stability of CUC grouts. In addition, fine particles of UC, UF, and US can effectively fill the pores, while the volumetric expansion of AUA and gypsum decreases the pores and thus affects the microstructure of the solidified grout. The compressive test results have shown that the addition of specific amounts of UF and US can ameliorate the mechanical properties of CUC grouts. Finally, the CUC22‐8 grout was used to reinforce the No. 20322 belt roadway. The results of numerical simulation and field monitoring have indicated that grouting can efficaciously reinforce the surrounding rock of the roadway. In this research, high‐performance CUC grouts were developed for surrounding rock reinforcement of underground engineering by utilizing UC and some additives.

Understanding the role of andesite igneous rock in enhancing the performance of alkali-activated ultrafine slag exposed to normal and elevated temperatures

According to the literature, the engineering properties of alkali-activated slag (AAS) generally decrease as temperatures rise up to 1200 °C. Although the addition of certain amorphous aluminosilicate additives can increase the residual strength of AAS, it still exhibits lower performance compared to samples cured at ambient temperature. Hence, there is a significant need to identify an effective additive that can greatly enhance the thermal stability of AAS at elevated temperatures. In this study, the contribution of andesite igneous rock (AIR) in improving the performance of alkali-activated ultrafine slag (AAUS) at normal and elevated temperatures was evaluated. The addition of AIR at a weight percentage of 10 % enhances the performance of humidity-cured AAUS through its filling and nucleating effect. However, increasing the AIR content beyond 90 wt% negatively impacts the physical and mechanical performance of AAS due to the low reactivity of AIR towards alkali activation. Nevertheless, higher AIR content enhances the tolerance capacity of AAUS to temperatures as high as 1200 °C. AIR acts as a microaggregate in the activated system, reducing the contraction of AAUS at temperatures below 1000 °C. At higher temperatures, the unreacted AIR undergoes transformation into solidified melt and thermally-stable pyroxenes. This results in microstructural compaction and an increase in compressive strength, particularly when the AIR content exceeds 50 wt%.

Surface characteristics, pore size and enhanced chemical resistance using graphene oxide nano sheets in ultrafine slag cement mortars

Concrete gets exposed to weathering. Thus, the structures sustain significant damage, significantly reducing the concrete’s durability properties. Nanofillers can improve a material’s ability to hydrate, which enhances the material’s fresh, toughened and durability assets. The presented work is cement mortar with Ordinary Portland Cement with 10% Ultrafine slag (UFS) and various Graphene oxide (GO) mixtures (0.01% to 0.04%) subjected to 3% sulphuric acid to assess their chemical resistance. The Brunauer, Emmett and Teller analysis appraised the preliminary research by exposing the surface attributes and pore size dimensions. The test result elucidates GO 0.03% with 10% UFS was best. The evaluation of acid-exposed specimens is based on changes in the specimens’ size, mass and visual scrutiny. The highest sulphate and acid resistance were observed for CMS4 and CMA4 with the least mass, length and flexure strength loss at 28 and 56 days. The surface was unaffected in microscopic studies, and there was no loss of flexural strength.

Physio-chemical characterisation of ultra-fine-slag-based ultra-high-performance concrete

Ultra-high-performance concrete (UHPC) meets the demand of modern infrastructure due to its exceptional strength and durability. The effects on concrete strength of the size and shape of fine aggregates, and binder content and type, were investigated. Particle packing concepts were adopted for fine aggregate optimisation, and the shape of the fine aggregate was assessed using an aggregate image measurement system. Further, the effects of binder content, binder type and curing age were investigated through compressive strength, thermo-gravimetric analysis (TGA) and quantitative X-ray diffraction. Mixtures with a 2.36 mm nominal maximum size of aggregates (n.m.s.a.) and angular aggregates exhibited higher compressive strength than those with a 1.18 mm n.m.s.a. No significant increase in the compressive strength was observed in mixtures with a binder content greater than the optimum 1000 kg/m3. The study also revealed that ultra-fine slag is a feasible alternative to silica fume. The TGA and X-ray results of concrete paste samples at different curing ages showed that the degree of hydration was relatively low (38.3%) with no further significant increase beyond 7 days. This work contributes to the fundamental understanding of the effect of raw materials on UHPC strength, which helps in rational selection of materials and mixture proportioning.

A Study on Experimental Analysis of Strength of Concrete incorporating Ultrafine Slag Mineral

The cement concrete has attained the status of a major building material in the modern construction because of its various advantages such as its adequate plasticity, remolding characteristics. It is used extensively all over world. But, environmental concerns both in terms of damage caused by the extraction of raw material and the emission of carbon dioxide during the manufacturing of cement have brought pressures to reduce consumption of cement by the use of relatively effective substitute materials. The substitute materials can be mineral admixtures such as fly ash, rich husk, etc. or ultra-fine material such as steatite powder, ultra-fine slag. This paper is based on the compilation of the experimental analysis done by various researchers and scientists. This paper reviews the results of an experimental study, conducted by various authors and researchers to evaluate the strengths and strength efficiency factors of hardened concrete, by partially replacing the cement by various ultrafine materials such as blast furnace slag, fly ash, alccofine, steatite powder, ultra fine calcium carbonate. This reports on the study conducted on the effect of ultrafine slag on the strength of concrete and in order to make an approach to reduce the content of Ordinary Portland Cement which ultimately results in the less carbon emission and less carbon footprints to achieve same or relatively better strength and workability.

Mechanical and microstructural properties of ultrafine slag cement mortar reinforced with graphene oxide nanosheets

Mechanical and microstructural properties of ultrafine slag cement mortar reinforced with graphene oxide nanosheets

Evaluation of the role of fibres and admixture(s) on sustainable crack reduction in expansive soil

Many geotechnical infrastructure facilities such as canals, farm ponds, reservoirs, natural slopes and landfills are prone to cracking during wetting/drying cycles, mainly due to the presence of expansive soils. The formation of cracks may result in significant ingress/loss of water and leachate percolation from landfills causing contamination of land/ground water. Proper lining/stabilization of the above stated geotechnical facilities would minimize loss of water/migration of leachate. In this context, the present study evaluates the performance of expansive soil blended with fibres, and with/without admixtures, on its cracking behaviour. Desiccation drying tests have been performed on expansive soil blended with fibres, by varying the type of fibres (viz., natural coir and polypropylene fibres), proportion of fibres (0.5% to 2% of dry soil weight) and exposure temperature, viz., 27 °C (ambient temperature) and 45 °C (representing hot arid conditions). Crack and shrinkage intensity factor (CSIF) has been computed as ratio of area of crack and shrinkage to total area of specimen. It has been observed from the study that addition of fibres substantially reduces the CSIF values, with 1% polypropylene fibres yielding maximum reduction. Further, the expansive soil has been blended with optimum proportion of polypropylene fibres (1%) and admixture with proportion varying from 2.5% to 10%, wherein a maximum reduction in CSIF values upto 73% were achieved for soil with 1% polypropylene fibres and 10% ultrafine slag. Though, complete crack mitigation could not be achieved, attributed to high cracking potential of expansive soil due to differential stresses during drying, size and area of the cracks has been substantially reduced. The study results are quite encouraging in utilization of fibres with admixtures, for sustainable reduction of cracking in expansive soil, and optimizing the thickness of lining/usage of thinner water proofing membranes for canals, farm ponds and other similar construction on expansive soils.

Experimental Study on the Effects of Corrosion in Reinforced Concrete Incorporating Steel Fiber and Ultra-Fine Slag

Abstract: In this work, a thorough review of the literature was conducted with a primary focus on accelerated corrosion-induced corrosion. The report that follows compares different reinforced concrete mixtures following corrosion. By adjusting the transparent cover and reinforcement diameter, a simple reinforced concrete specimen, a specimen of reinforced concrete mixed with steel fiber, and a specimen of reinforced concrete mixed with steel fibre and ultra-fine slag were all produced. Using the accelerated corrosion method, the rate of induced corrosion, the flexural strength before and after corrosion, and the depth of corrosion penetration were compared.

High early strength-high performance concrete produced with combination of ultra-fine slag and ultra-fine silica: Influence on fresh, mechanical, shrinkage and durability properties with microstructural investigation

This study relates to High early strength- High Performance concrete (HPC) produced with incorporation of Ultra-fine Slag (UFS) and Ultra-fine Silica (UFSi). Compressive Strength development was studied from an early period of 14–15 h of casting up to 180 days. The variations in workability and its retention levels after 60 min of mix preparation were recorded. Elastic modulus, compressive strain behaviour, flexural parameters, early age shrinkage and few durability properties were measured for resulting optimal concrete mixes. Modifications induced at microstructural level were assessed by Scanning Electron Microscopy (SEM) and Nanoindentation tests. Incorporation of UFS and UFSi resulted in reduction of fresh properties beyond certain addition percentages. Usage of UFS as part replacement to GGBS in HPC mixes showed considerable improvement with regards to mechanical and durability aspects. Incorporation of UFSi was evaluated to prominently improve early age strength of concrete in combination with UFS at optimal quantities, while moderately improving other mechanical properties. Early age shrinkage induced stress levels and the brittleness of concrete were observed to increase with use of selected admixtures under multiple blend system. Improvement in the microstructure was observed with denser hydrated matrix offering enhanced homogeneity and better bonding with aggregates. Increase in strength governing hydration phases was evidenced for optimal addition of UFS and UFSi. Durability behaviour was significantly enhanced for combination of UFS and UFSi owing to microstructural improvement through pore refinement.

A study on utilization of landfill mined soil like fraction for sustainable reduction in swelling and cracking potential for expansive and marine soils

Landfill mined soil like fraction (LMSF) is derived from mining of legacy landfill waste after removal of larger fraction such as construction debris, clothes, plastics and other recyclables, and accounts for significant proportion of the total legacy landfill waste. LMSF has found applications as landfill cover material; however, owing to its large quantity in many cities, there is a need to explore more applications for its utilization. In this context the present study explores the role of LMSF (filler replacement) with/without ultrafine slag, US (primary admixture) and lime, L (activator) in controlling the shrinkage and cracking of marine and expansive soils during drying. The ratio of the area of crack and shrinkage to total area of specimen, defined as crack and shrinkage intensity factor (CSIF), has been utilized for quantification of the cracking and shrinkage characteristics of soils with/without stabilization. Further, the effect of soil stabilization on the swelling potential (viz., free swell index and swelling pressure) has been evaluated for the soils. In the present study, complete crack mitigation for expansive soil has been achieved for the combination: 40%LMSF (<425 μm) + 50% expansive soil + 8%US + 2%L, while for the marine soil it has been achieved for combination: 40% LMSF (<425 μm/<2 mm) + 50% marine soil + 8.5%US + 1.5%L. The study findings are useful in the context of utilizing LMSF with sustainable admixtures for reducing cracking and swelling potential of soils for various infrastructure applications such as natural and stabilized slopes, embankment, canal bed and ponds.

A study on the role of metakaolin and alccofine as supplementary materials on strength properties of concrete

In recent years, the utilization of supplementary materials has played an important role in development of high strength concrete, improving the overall properties of concrete and rendering sustainability to concrete construction. Though different supplementary materials such as fly ash, silica fume, metakaolin and ground granulated blast furnace slag have been utilized for development of concrete, there is a need to understand the comparative role of these supplementary materials on workability, early strength gain, stress–strain response under compression and flexure, etc. In this context, the present study evaluates the comparative performance of metakaolin and alccofine (ultrafine slag) as supplementary materials in concrete; wherein, 30% replacement of cement with supplementary cementitious has been done (20% replacement with fly ash (class C) and 10% replacement with metakaolin, MK / alccofine, AL). The comparative assessment of the compressive strength, stress–strain behaviour and flexural response of MK- and AL- blended concrete has been carried out, and the results suggests that AL blended concrete exhibits higher early age strength (7 days curing), as compared to MK blended concrete. Similar trend in strength development is witnessed for 28 days and 56 days cured specimen; wherein, the average 56 days compressive strength of AL blended concrete observed to be 86.11 MPa, is substantially higher than 61.45 MPa strength observed for MK blended concrete (load control tests). Further, the flexural strength of AL blended concrete is noted to be higher than MK blended concrete. Moreover, the pre-peak and post-peak energy absorption capacity, evaluated from stress-strain (displacement control compression tests) and load–displacement response (flexural tests) of AL blended concrete, is higher than MK blended concrete, indicating its higher ductility under loading. Overall, the study findings suggest the beneficial contribution of supplementary materials in developing sustainable concrete with superior properties, and demonstrates the potential of AL as supplementary material in concrete.

Physico-Chemical Substantiation of Obtaining an Effective Cement Composite with Ultrafine GGBS Admixture

To solve a number of problems in construction materials science, composites with nano and ultrafine admixtures were analyzed. Their properties were studied, taking into account the variants of homogenization and stabilization of the system. To characterize the processes of the structure formation of a new material, mathematical methods were also applied. According to the literature review, the aim of the work was formulated. The subject of this research is to conduct physico-chemical studies that characterize the processes occurring during the homogenization and stabilization of the cement system with GGBS components and to establish the effect of the admixture on the properties of the composite. To achieve this goal, an ultrafine admixture based on GGBS was obtained, and the possibility of its introduction into the cement system in the form of a stabilized suspension instead of mixing water was considered. To provide increased characteristics of cement stone modified with the ultrafine admixture, a number of tests were carried out to study homogenization and stabilization of fine slag particles in suspension. The ultrasonic processing parameters were defined to provide uniform distribution of fine slag additive in the suspension: the processing time is 15–20 min, the frequency of ultrasonic vibrations is 44 kHz, the temperature of the dispersed medium is 25 ± 2 °C. To define physical and chemical processes appearing during the introduction of fine slag into water and water-polymer dispersed medium, the mechanism of interaction between fine slag and water was studied. In addition, the mechanism of chemisorption on the surface of fine slag particles and the stabilization mechanism of ultrafine slag particles with a plasticizer was studied to form the concept of aggregate and sedimentation stability of slag particles in suspension. It was found that the stabilization of fine slag particles by a plasticizer is significantly influenced by the hardness of water. The higher the water hardness, the more plasticizer required to stabilize the fine slag particles. At the same time, it was established that the concentration of the plasticizer should not exceed the critical micelle concentration value. If it is exceeded, the plasticizer solution transforms into the micellar colloidal system, and the stabilization of fine slag suspension will not occur. The studies of homogenization and stabilization of the slag suspension allowed the authors to substantiate the possibility of uniform distribution of fine particles in the cement matrix, followed by the formation of a denser and stronger cement stone structure. Cement-sand samples based on Portland cement (OPC) and slag-Portland cement (SPC) with GGBFS admixture showed higher compressive and flexural strength characteristics in the initial hardening periods and at 28 days. It was found that modified samples are more stable in an aggressive medium. On the 90th day of exposure, the resistance coefficient was 0.9 for a modified sample based on OPC and 0.98 for a modified sample based on SPC. The increased sulfate attack resistance of the samples is due to the formation of a dense stone with reduced porosity. It is noted that the porosity of modified OPC samples decreases by 14% and by 18% for SPC-based modified samples compared to the control sample at 28 days. Due to the fact that pores in the cement stone are blocked with hydration products, which make the structure of the cement stone denser, the filtration of aggressive solutions deep into its structure is difficult. Thus, the obtained concrete based on a cement composite with ultrafine slag can be applied as a protective layer of steel reinforcement in a reinforced concrete structure.

Impact of Fine Slag Aggregates on the Final Durability of Coal Bottom Ash to Produce Sustainable Concrete

In the current investigation is presented the prospective substitution of cement and fine aggregates with fine slag material (Alccofine 1203) and coal bottom ash, respectively. The investigation was carried out in two steps, viz. Phase I and Phase II. In Phase I, a control mix was designed with basic ingredients of concrete, and then fine aggregates were partially replaced with five percentages (10%, 20%, 30%, 40% and 50%) of coal bottom ash (CBA). To improve the characteristics of coal bottom ash concrete mixtures, ultra-fine slag material, i.e., Alccofine 1203 (an innovative ultra-fine slag material, low calcium silicate, which offers reduced water demand depending upon the concrete performance) was used as a partial replacement of cement. In Phase II, the inspected effect of replacing 5%, 10%, 15% and 20% cement with Alccofine, a concrete mix containing 40% coal bottom ash, on concrete properties such as workability, compressive strength, split tensile strength, flexural strength, pulse velocity, rapid chloride penetration along with a microstructural analysis using SEM was studied. It was concluded from cost analysis that the 15% replacement of cement with ultra-fine material Alccofine in 40% coal bottom ash concrete achieved the properties of high-strength concrete, with an 8.14% increase in cost compared to the control increase. The significance of this work lies in the fact that we achieved a high-strength concrete by using 40% industrial waste, i.e., coal bottom ash, as a partial replacement of fine aggregates in combination with the 15% Alccofine inclusion as a partial replacement of cement. About 58% improvement in compressive strength was recorded for 40% coal bottom ash and 15% Alccofine mix.

The Synergistic Effects of Ultrafine Slag Powder and Limestone on the Rheology Behavior, Microstructure, and Fractal Features of Ultra-High Performance Concrete (UHPC)

This study investigated the effect of the interaction between ultrafine slag powder (USL) and limestone (LS) on the rheology behavior, microstructure, and fractal features of UHPC. The results indicated that B2 with mass ratio of 2:1 between the USL and LS obtained the highest compressive strength and the lowest yield stress. The combination of the USL and LS facilitated the cement hydration, ettringite, and monocarboaluminate (Mc) formation, as well as the increase in the polymerization of the C-S-H. The synergistic action between the USL and LS refined the pore structure due to the formation of the Mc, compensating for the consumption of the CH by the pozzolanic reaction, which provided a denser microstructure in the UHPC. The fractal dimension (Ds) of the UHPC was strongly related to the concrete pore structures and the compressive strength, which demonstrated that a new metric called the Ds value may be used to assess the synergistic effect of the UHPC.