Supplementary Cementitious Materials Research Articles

Assessing the Environmental Sustainability of UHPC in Modern Construction Practices

A comprehensive examination was undertaken to investigate various aspects related to the development and application of Ultra-High-Performance Concrete (UHPC). The research explored eco-friendly approaches, such as incorporating supplementary cementitious materials and nanoparticles, optimizing binder systems, and assessing chemical activators. These modifications improved mechanical properties and reduced environmental impact, including embodied CO2 emissions. Additionally, the utilization of waste materials like CRT glass showed energy savings and reduced emissions. Studies focused on optimizing UHPC mix designs, emphasizing a balance between performance and environmental impact. Techniques like statistical mixture design methods and dynamic testing assessed UHPC's environmental and economic impacts, highlighting significant energy savings and reduced CO2 emissions with waste material recycling. Overall, the research contributes valuable insights into UHPC development and its ecological footprint in construction

Role of supplementary cementiteous materials in mitigating heat of hydration in mass concrete elements

Concrete’s heat of hydration can cause wide restraint cracks, delayed ettringite formation and low strength. The heat of hydration in concrete poses significant challenges in the construction industry particularly in mass concrete elements. Addressing these challenges, the utilization of supplementary cementitious materials (SCMs) such as fly ash (FA) and ground granulated blast furnace slag (GBFS) in concrete has been extensively studied for their individual contributions in modifying the heat of hydration. However, the comparative effectiveness of FA and GBFS, as well as the implications of their combined use in a ternary blend mix, remain underexplored. This study aims to bridge this gap by investigating the heat evolution profiles of concrete blends incorporating varying proportions of FA, GBFS, and general Portland cement (GPC). Through a series of semi-adiabatic tests, the study evaluates the hydration kinetics, maximum temperature rise, and time delay to peak temperature for binary and ternary mixes. The findings suggest that while individual SCMs like FA and GBFS offer distinct thermal benefits, their combined use in a ternary blend presents a synergistic effect, optimizing heat management in concrete. In essence, this study not only underlines the potential of ternary blends in enhancing concrete's thermal performance but also emphasizes their role in promoting sustainable and resilient construction practices.

Effects of carbonation and sponge wetting solution on diffusion potential of carbonated concrete with supplementary cementitious materials

Potential measurement of reinforced concrete is critical for identifying the corrosion state of rebar and monitoring the pH value and chloride concentration of concrete pore solution but remains a challenging task due to the many uncertainties involved. This study aims to investigate the effects of concrete carbonation and the sponge wetting solution on the diffusion potential of partially carbonated concrete blended with supplementary cementitious materials (SCMs). Portland cement is replaced by silica fume (SF), pulverized fly ash (PFA) and ground granulated blast-furnace slag (GGBS) at different replacement levels. Other experimental variables include the degree of concrete carbonation, the wetting solution of the sponge (tap water and 0.3 M NaOH) and the degree of saturation. The results indicate that concrete carbonation-induced diffusion potential would lead to significant errors on the monitoring of the pH value and chloride concentration by measuring the potential between the embedded sensors and external reference electrode. During the pH value and chloride concentration monitoring, 0.3 M NaOH should be used as the wetting solution of sponge for non-carbonated concrete and partially carbonated concrete while tap water should be used for fully carbonated concrete. To some extent, the decline in the degree of concrete saturation can reduce the diffusion potential.

Investigating the Hydration, Mechanical Properties, and Pozzolanic Activity of Cement Paste Containing Co-Combustion Fly Ash

The heat of hydration, mechanical properties, pozzolanic activity, and microscopic characteristics of cement pastes incorporating co-combusted fly ash (CCFA) were investigated, and the disparities between the CCFA/cement system and the coal fly ash (CFA) binding system were also compared. The results indicate a decrease in the heat of hydration for both CFA and CCFA samples, with a more pronounced trend observed as the fly ash content increased from 10% to 30%. The distinction in the early hydration between CFA and CCFA samples primarily manifested in the rate of heat release, potentially correlated with variations in the active Al2O3 content in the fly ash. Neither CFA nor CCFA samples exhibited significant cementitious activity at 3 days, functioning solely as inert fillers in the cement paste. By 3 and 28 days, the mechanical properties of both CFA and CCFA samples were inferior to those of pure cement paste. However, by 180 days of hydration, the compressive strength of CCFA-blended mortar notably increased, with the highest strength observed in the 10% CCFA-blended sample. Both CFA and CCFA samples produced the secondary hydration product C-A-S-H and demonstrated comparable consumption of calcium hydroxide (CH). These findings underscore the potential of CCFA as a supplementary cementitious material (SCM) and lay a foundation for its widespread adoption.

Potential Utilization of Loess in Grouting Materials: Effects of Grinding Time and Calcination Temperature

There is a huge reservation of loess in the Shanxi mining area in China, which has great potential for preparing supplementary cementitious materials. Loess was modified via mechanical and thermal activation, and the pozzolanic activity was evaluated using an Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). Moreover, the workability of grouting materials prepared using modified loess was assessed. The experimental results revealed that the number of ultrafine particles gradually increased with the grinding time, enhancing the grouting performance. The coordination number of Al decreased upon the breakage of the Al–O–Si bond post-calcination at 400 °C, 550 °C, 700 °C, and 850 °C. Moreover, the breaking of the Si–O covalent bond produced Si-phases, and the pozzolanic activity of loess increased. Furthermore, the modified loess was hydrated with different cement proportions. With increasing grinding time, the overall setting time increased until the longest time of 14.5 h and the fluidity of the slurry decreased until the lowest fluidity of 9.7 cm. However, the fluidity and setting time decreased with increasing calcination temperature. The lowest values were 12.03 cm and 10.05 h. With the increase in pozzolanic activity, more ettringite was produced via hydration, which enhanced the mechanical properties. The maximum strength of the hydrated loess after grinding for 20 min reached 16.5 MPa. The strength of the hydrated loess calcined at 850 °C reached 21 MPa. These experimental findings provide theoretical support for the practical application of loess in grouting.

Recycling of mineral wool waste as supplementary cementitious material through thermochemical treatment.

Mineral wool is commonly used in construction as thermal insulation material. After the product's lifetime, it is classified as hazardous waste if no trademark of the European Certification Board for Mineral Wool Products (EUCEB) or the German Institute for Quality Assurance and Labelling (RAL) exists. Mineral Wool Waste (MWW) is typically landfilled in Europe, which is challenging due to its low bulk density and dimensional stability. This circumstance highlights the need for alternative recycling methods that increase the recycling rate of construction and demolition (C&D) waste. This article outlines the recycling opportunities of MWW and focuses on the use of thermochemical treatment of different mixtures of input materials to produce a supplementary cementitious material (SCM). The material characterisation results and investigations on the binder suitability demonstrate that the slag fractions after the thermochemical treatment are well-qualified to be used as reactive binder components. Additionally, a material flow analysis was conducted to estimate the substitution potential of MWW as SCM in the Austrian cement industry.

New and Sustainable Coal Char-Based Paving Blocks for Roadway Applications

Paving blocks are widely used in engineering construction for durable pavement surfaces characterized by their interlocking capability to enhance structural integrity. This study explores the potential use of char as a byproduct from coal pyrolysis and an alternative raw material to natural aggregates in developing paving blocks, aiming to reduce the associated environmental issues associated with the uncontrolled and excessive mining of natural resources. This study finds the paving blocks made from char to have the required engineering properties as mentioned by ASTM standard C936. Trass and trass-lime are added as supplementary cementitious materials (SCMs) to enhance the performance of char-based paving blocks. The incorporation of SCMs as a cement replacement also aims to reduce the carbon footprint arising from increased cement use. The compressive strength increased from 55.7 MPa to 65.71 MPa at 12.5% cement replacement with trass-lime. The water absorption is reduced to 4.63% from 4.95%. Beneficial effects towards freeze–thaw durability and abrasion resistance are also observed on trass-lime-incorporated paving blocks. This study signifies the remarkable potential use of coal-derived char and SCMs in developing light, high-strength, and durable paving blocks, showcasing their competitive engineering performance. These new char-based paving blocks will contribute towards a more sustainable construction environment and advance the current construction and engineering practices.

Mechanical properties of silica fume based concrete: A review

The significant industrial growth accompanying rapid urbanization has spurred a heightened demand for concrete. Cement production, a primary ingredient of concrete, results in substantial carbon dioxide (CO2) emissions. To mitigate this impact, alternative pozzolanic materials like silica fume (SF) can be incorporated. SF, an industrial byproduct, serves as a supplementary cementitious material (SCM), offering benefits of waste recycling. This study aims to comprehensively review the addition of SF as an SCM replacement, with a specific focus on the mechanical properties of concrete. Numerous scientific papers were analyzed and carefully examined from the period of 1998 to 2023, which forms the bibliometric core of this study. The entire scopus database was examined for co-occurrence of keywords and actively contributing countries and results were shown through network diagrams. The effect of SF addition on fresh properties as well as mechanical properties were discussed. The inclusion of SF in range of 10–25% by quantity of cement was found to have increased split tensile strength, compressive strength and flexural strength. However, the addition of SF beyond 25% replacement level can have an adverse impact on the overall characteristics of the composite mix. The present study summarizes the major trends as reported in the available literature where SF has been used as SCM. Apart from finding the general trends, various research gaps have been identified.

Durability analysis of sustainable mortars with biomass fly ash as high-volume replacement of Portland cement

Utilization of various supplementary cementitious materials was in the last decades considered beneficial for the replacement of the energy-intensive Portland cement to meet sustainable targets. However, structural changes in energy production and heavy industry in Europe significantly limit the availability of coal fly ash and blast furnace slag for blended cement production. On the other hand, the increasing production of biomass ash (BA) presents not only challenges for its disposal but also new opportunities for the concrete industry. In this paper, the durability of cement composites containing up to 70 wt.% of BA as Portland cement (PC) replacement was analyzed, taking into consideration also microstructure and mechanical properties. The experimental results showed a preservation of good mechanical performance up to the 30 wt.% limit. The freeze-thaw resistance was not affected significantly up to the 40 wt.% BA dosage during the first 300 cycles. The analyzed composites also exhibited a good overall resistance to alkali silica reaction- and sulfate-induced expansion up to the 50 wt.% PC replacement. BA can thus be considered as a prospective future alternative to coal fly ash and blast furnace slag to meet the sustainable development goals in the building industry.

Ion transport mechanism and diffusion model establishment in recycled aggregate concrete subjected to magnesium, sulfate, and chloride attack

Recycled aggregate concrete (RAC), which is used in Northwest China, is inevitably subjected to various aggressive environments. However, the aggressive ions of chloride, sulfate, and magnesium and the original ions of calcium and hydroxide in RAC under the combined action of magnesium-sulfate-chloride attack and dry–wet (D&W) cycles have received little attention in previous studies. Therefore, in this study, the content of aggressive and original ions in exposed RAC was quantified, and the influence of the replacement ratio of supplementary cementitious materials (SCMs) on diffusion was investigated. Results showed that the contents of chloride, sulfate, and magnesium in exposed RAC increased with an increase in the replacement ratio of silica fume (SF) and metakaolin (MK). In contrast, the contents decreased with the increase in the replacement ratio of granulated blast furnace slag (GBFS). At the same exposure time and depth, the content of RAC with ternary cementitious materials from the highest to the lowest was in the order of cement–fly ash –SF, cement–fly ash–MK, and cement–fly ash–GBFS. Visual appearance, relative compressive strength, and the diffusion coefficient exhibited a similar change law. An exponential relationship was observed between the diffusion and time delay coefficients and the replacement ratio of SCMs, and the content of aggressive ions on the exposed surface decreased linearly with increasing exposure time. Diffusion models of aggressive ions were established to consider the multiple effects. Aggressive ion–original ion interaction influenced the mineral phases’ composition in the corrosive zone and led to a difference in the diffusion process and depth.

The improvement on calcium leaching resistance of high SCMs content cement in ammonium chloride solution using particle gradation technique

Particle gradations of Portland cement (PC), fly ash (FA), and blast furnace slag (BFS) were optimized to improve the calcium leaching resistance of blended cement with high contents (up to 70%)of supplementary cementitious materials (SCMs). The results showed that optimized blended cement showed refined initial pore volume distribution, reduced portlandite (CH) content, finer CH macrocrystals and enhanced stability of C-(A)-S-H gel. Consequently, it displayed exceptional calcium leaching resistance with reduced losses in mechanical performance, mass and pore degradation after calcium leaching. Blended cement with 30% PC (D50 = 14.46 μm), 30% FA (D50 = 10.94 μm), 20% BFS (D50 = 10.52 μm), 13% BFS (D50 = 5.31 μm) and 7% BFS (D50 = 4.71 μm), showing compressive strength retention rate of 79.05% and mass loss rate of 1.64%, was suggested as viable choice for calcium leaching resistant concrete.

Why Sustainable Concrete Cannot Penetrate Concrete Markets

Several studies have shown that sustainable concrete mixtures could be a solution to reduce the CO2 emissions of concrete while utilizing supplementary cementitious materials (SCMs) that are waste byproducts, including fly ash, metakaolin, and ground granulated blast furnace slag. However, for these sustainable concrete mixtures to be adopted as a replacement for conventional ordinary Portland cement concrete (OPCC), site engineers, decision-makers, and authorities need to be aware of the mechanical and durability properties of these sustainable concrete mixtures. A brief review of the mechanical and durability properties of both geopolymer concrete and alkali-activated cement demonstrates the objective performance relative to OPCC. Then, the results of a survey targeting researchers, site civil engineers, decision-makers, and employees in governmental agencies are presented. The results indicate that even though the mechanical and durability properties of geopolymer/sustainable concrete are recognized, limited awareness and availability present significant challenges to the adoption of sustainability concrete in infrastructure projects. The survey highlights the need for focused marketing efforts to educate decision-makers on the availability as well as mechanical and durability properties of geopolymer concrete. Additionally, it serves as a call for future research to overcome obstacles such as high initial cost, safety concerns, and limited practical applications.

Statistical assessment of the factors influencing fly ash reactivity

Siliceous fly ash is a pozzolanic supplementary cementitious material often used in cement and concrete production. The influence of the chemical, mineralogical and physical properties of 75 siliceous fly ashes on their reactivity was examined in this study. The reactivity was analyzed by relative mortar compressive strength and a rapid screening test (a version of the R³ test). A statistical data analysis was carried out to evaluate the factors influencing the reactivity of the ash. The screening test was found to be able to predict the reactivity within short periods of time, while the relative strength is not a good measure for reactivity. It was also found that the TiO2 and chloride content of the fly ash can serve as an indicator for its reactivity.

Effect of Diethanol-Isopropanolamine and Typical Supplementary Cementitious Materials on the Hydration Mechanism of BOF Slag Cement Pastes

This study investigated the effects of lithium slag and iron tailings on the hydration mechanism of Basic Oxygen Furnace (BOF) slag cement paste with the addition of 0.06% diethanol-isopropanolamine (DEIPA). This study examined the fluidity, compressive strength, pore solution pH, and hydration products of BOF slag-based composite cementitious materials. The results showed that DEIPA facilitated the conversion from ettringite (AFt) to monosulphate (AFm) and improved the early compressive strength of the BOF slag–cement mortar. Incorporating lithium slag into the DEIPA-containing BOF slag–cement system promoted AFt formation, increased calcium-silicate-hydrate production, and enhanced the microstructure. BOF slag, lithium slag, and iron tailings exhibit synergistic effects in cement pastes. BOF slag and lithium slag provided the reactive components SiO2 and Al2O3. In the early hydration stages, the iron tailings primarily served as fillers, accelerating the system’s reactions.

Efficiency of self-compacting concrete made with variable sustainable cementitious materials: A TOPSIS algorithm approach

The use of supplementary cementitious materials as a partial replacement for cement is taking the lead in the concrete production industry. Being known as by-products from various manufacturing properties, concrete produced with such materials is considered a sustainable alternative to normal concrete. Three different by-product materials have been investigated in this study for the production of sustainable self-compacting concrete (SCC), namely, ground granulated blast furnace slag (GGBS), fly ash (FA), and silica fume (SF). Compressive strength, production cost, and global warming potential (GWP) were the main testing parameters for the mixes' performances. Multi-criteria decision-making algorithm was implemented using the TOPSIS model to investigate the ultimate performance of those SCC mixes considering all tested parameters simultaneously. Results showed the best SCC performance can be attained when using about 60 % of GGBS as a partial replacement for cement.

An Experimental Study on Self Compacting Concrete with Partial Replacement of Cement by Silica Fume and Crumb Rubber

Abstract: Self-compacting concrete (SCC) is a type of concrete that can flow and consolidate under its own weight without the need for vibration. SCC has many advantages such as improved workability, durability, surface quality, and reduced noise and labour. However, SCC also requires a high amount of cement and fine materials, which increases the cost and environmental impact of concrete production. Therefore, the use of supplementary cementitious materials such as silica fume and crumb rubber is beneficial to reduce the cement content and enhance the properties of SCC. This study aims to explore the effects of mixing silica fume and crumb rubber on the fresh and hardened properties of SCC. This involves the preparation of various concrete mixes with different percentages of cement replaced by silica fume and crumb rubber. Through a series of experiments, we evaluate the fresh and hardened properties of the SCC mixes, fresh properties such as workability, passing ability, and filling ability, while hardened properties including compressive strength, tensile strength, and flexural strength. The result obtained from these tests are compared with conventional concrete of M30 grade od concrete specimens. Hence the use of silica fume and crumb rubber leads to reduction in cement quantity for construction purpose and its use should be promoted for better performance as well as environmental sustainability.

Self-Compacting Concrete Using Supplementary Cementitious Materials and Fibers: Review

Self-Compacting Concrete Using Supplementary Cementitious Materials and Fibers: Review

Replacing Fly Ash or Silica Fume with Tuff Powder for Concrete Engineering in Plateau Areas: Hydration Mechanism and Feasibility Study

Abundant tuff mineral resources offer a promising solution to the shortage of fly ash (FA) and silica fume (SF) resources as emerging supplementary cementitious materials. However, a lack of clarity on its hydration mechanism has hindered its practical engineering application. In this study, high SiO2-content tuff powder (TP) was examined to assess the mechanical and workability performance of mortar specimens with varying particle sizes of the TP as complete replacements for FA or SF. Microscopic analysis techniques, including X-ray diffraction (XRD), differential thermal analysis (DTG), and energy-dispersive X-ray spectroscopy (EDS), were employed to elucidate the hydration mechanism of the TP and its feasibility as a substitute for SF or FA. Results indicated that TP primarily functions as nuclei and filler, promoting cement hydration, with smaller particle sizes amplifying the hydration ability and increasing Ca(OH)2 and C-S-H gel content. The specimens with TP (median particle size 7.58 μm) demonstrated 9.2% and 29.9% higher flexural and compressive strengths at 28 days, respectively, compared to the FA specimens of equal mass. However, fluidity decreased by 23.1% accordingly. Due to TP’s smaller specific surface area compared to SF, the TP specimens exhibited higher fluidity but with decreased strength relative to the SF specimens. Overall, TP shows potential as a replacement for FA with additional measures to ensure workability.

Optimal utilization of low-quality construction waste and industrial byproducts in sustainable recycled concrete

Construction and demolition waste (CDW) contains abundant low-quality recycled brick aggregates (RBA) that can potentially substitute natural aggregates (NA) in concrete production. However, recycled brick aggregate concrete (RBAC) shows inferior mechanical and durability performance compared to natural aggregate concrete (NAC), posing barriers to RBAC widespread adoption. This study investigates the combined influence of supplementary cementitious materials (SCMs) derived from industrial byproducts and hooked-end steel fibers (HSF) on properties of concrete with 0%, 50% and 100% RBAs from CDW as replacement for natural coarse aggregates (NCA). Addition of 0.5% HSF and 20%, 10%, and 30% fly ash (FA), silica fume (SF), and ground granulated blast furnace slag (GGBS) as cement replacement, respectively, were considered. Effect of different SCMs and HSF on compressive strength, splitting tensile strength, flexural strength, ultrasonic pulse velocity (UPV), water absorption (WA), freeze-thaw (FT) and acid attack resistance of concrete were studied. Results indicated that individual incorporation of HSF showed more contribution towards mechanical performance while combined incorporation of SCMs and HSF enhanced both mechanical and durability properties, along with reduction of up to 15.6% in embodied carbon of RBAC. Microstructural examination showed pore refinement and interfacial transition zone densification in RBAC with SCMs and HSF. This study demonstrates that sustainable RBAC with excellent mechanical and durability requirements could be produced using demolished brick waste and industrial byproducts.

Durability of Ternary Blended Concrete Incorporating Rice Husk Ash and Calcined Clay

Research on the combined substitution of supplementary cementitious materials (SCMs) has already demonstrated that it might be one of the few viable options to produce low-carbon concrete at scale. This paper presents an experimental investigation on the performance and durability of rice husk ash (RHA) and calcined clay (CC) in ternary blended concrete exposed to chloride attacks under wet/dry cycles. Portland cement (PC) was replaced by RHA and CC up to 50% by weight to produce low-carbon concrete. Samples were subjected to wet/dry cycles in 3.5% NaCl water, with mineralogical composition and microstructure development before and after exposure analysed by TGA-DSC, MIP, XRD, and SEM. The durability of the concrete against wet/dry cycles was investigated in terms of compressive strength, water absorption, open porosity, density, thermal conductivity, and electrical resistivity. The results showed that concrete mixes with CC and RHA up to 60% exhibited an increase of 33% in compressive strength, followed by minimal changes in water absorption. While a decrease in electrical resistivity was measured in all samples with RHA and CC, increasing the CC content to 50% resulted in improved resistance to chloride penetration. Increasing the CC content resulted in a more refined microstructure, with an overall decrease in porosity of up to 32% compared to the control series. While RHA alone did not contribute to significant improvements after wet/dry cycles, the combined substitution of RHA and CC at SCM replacement levels of 60% showed an overall improvement in hardened properties and durability. This investigation provides valuable insights into the long-term performance and strength of innovative low-carbon concrete.