Sustainable Cementitious Materials Research Articles

Magnesium industry waste and red mud to eco-friendly ternary binder: Producing more sustainable cementitious materials

The increasing demand for cement-based materials has led to significant energy expenditure and greenhouse gas emissions. To produce more sustainable cementitious materials, partial Portland cement (PC) substitution is proposed, reducing clinker consumption and mitigating negative environmental impacts. Magnesium and aluminum industries produce tons of waste annually, including magnesium industry waste (MW) and red mud (RM). This study evaluated the feasibility of using industrial waste (i.e., MW and RM) as supplementary cementitious materials. A PC/MW/RM mixture containing 75% PC substituted with 25% of MW and RM (20% + 5%, 5% + 20%, and 12.5% + 12.5%) was developed as a ternary binder. Physical-chemical properties, such as phases, oxide composition, particle distribution and morphology, thermal behavior, and pozzolanic potential, were identified for the residues; the compressive strength of the prepared mortars was compatible with current standards. Therefore, partial substitution of PC with residues is feasible for producing eco-friendly binders.

Feasibility tests on ground granulated powders compiled from waste concrete for soil solidification

The objective of the present study is to examine the applicability of ground granulated powders (GGPs) as a cementitious binding material for soil solidification. The compressive strength gain of the GGPs was tested under alkali activation treatments using Na2SO4 or a ground granulated blast-furnace slag (GGBS) compound containing 7.5% Ca(OH)2, and empirically formulated through regression analysis using test data. Two types of activated GGPs with high compressive strengths were selected from the paste samples and then applied to soft cohesive soils at different binder-to-soil ratios. The sustainability of the activated GGPs was examined using the CO2 footprint calculated for the prepared soil-solidification mixtures. Lower porosity was measured in the GGP pastes activated by the 5% GGBS compound and 30% Na2SO4 in comparison to the other specimens; this resulted in a higher compressive strength gain for the two pastes. Additionally, the present soil solidification mixtures exhibited higher compressive strength than ordinary Portland cement-based solidification and an equivalent strength to geopolymerized metakaolin-based solidification. The results indicate that the GGPs activated by the 5% GGBS compound demonstrate great potential as sustainable cementitious binding materials for the targeted application areas, considering their considerably lower CO2 footprint and common compressive strength gain requirements.

Development of a novel eco-efficient LC2 conceptual cement based ultra-high performance concrete (UHPC) incorporating limestone powder and calcined clay tailings: Design and performances

This study presents an eco-efficient cement-limestone- calcined clay tailings ultra-high performance concrete (LC2 UHPC). On the basis of the D-optimal mixture design method, the LC2 UHPC recipes and fresh behaviors are firstly proposed and optimized. Then, the macro and micro characteristics of produced LC2 UHPC are evaluated. The obtained experimental results show that when the added total amount of limestone powder and calcined clay tailings reach 56.8% of the cementitious materials, the corrosion resistance properties of LC2 UHPC are optimized and advanced compared to normal UHPC. Afterwards, the microstructure and hydration properties of LC2 UHPC are presented. The ITZ of LC2 UHPC is denser than normal UHPC. Hydration degree of cement LC2 UHPC is higher. Moreover, the addition of limestone powder and calcined clay tailings can decrease the environmental impact by 37.1% compared to normal UHPC. The disadvantage of LC2 UHPC mainly is that the compressive strength and workability of LC2 UHPC is lower than normal UHPC. Considering the fact that the LC2 system is a low-carbon and more sustainable cementitious material than normal cement, the produced LC2 UHPC can be treated as an eco-friendly construction product, which is suitable to be wildly utilized to some area with plenty of clay sources in China in the future.

A Review on Cementitious Materials Including Municipal Solid Waste Incineration Bottom Ash (MSWI-BA) as Aggregates

Waste management is a vital environmental issue in the world today. Municipal solid wastes (MSWs) are discarded in huge quantities on a daily basis and need to be well controlled. Incineration is a common method for reducing the volume of these wastes, yet it produces ashes that require further assessment. Municipal solid waste incineration bottom ash (MSWI-BA) is the bulk byproduct of the incineration process and has the potential to be used in the construction sector. This paper offers a review of the use of MSWI-BA as aggregates in cementitious materials. With the growing demand of aggregates in cementitious materials, MSWI-BA is considered for use as a partial or full alternative. Although the physical and chemical properties of MSWI-BA are different than those of natural aggregates (NA) in terms of water absorption, density, and fineness, they can be treated by various methods to ensure suitable quality for construction purposes. These treatment methods are classified into thermal treatment, solidification and stabilization, and separation processes, where this review focuses on the techniques that reduce deficiencies limiting the use of MSWI-BA as aggregates in different ways. When replacing NA in cementitious materials, MSWI-BA causes a decrease in workability, density, and strength. Moreover, they cause an increase in water absorption, air porosity, and drying shrinkage. In general, the practicality of using MSWI-BA in cementitious materials is mainly influenced by its treatment method and the replacement level, and it is concluded that further research, especially on durability, is required before MSWI-BA can be efficiently used in the production of sustainable cementitious materials.

Durability Evaluation: Sustainable Semi-flexible Pavement Mixtures

The modern paving industry requires the production of high-performance pavement using more sustainable approaches. Semi-flexible pavement (SFP), prepared by filling an open-graded asphalt skeleton with cement-based grouting material, has been shown to offer high performance for heavily loaded highway and airport pavement applications. The major aim of this study was therefore to evaluate SFP durability based on more sustainable preparation techniques and materials. In this research, a half warm bitumen emulsion semi-flexible mixture (HWBESFM) was designed using local materials and low energy heating technique; the contribution of various sustainable cementitious grout materials on the durability properties of the mix was then evaluated. The developed grouts were prepared using paper sludge ash (PSA) and silica fume (SF) as supplementary cementitious materials (SCM), and the durability of the HWBESFM was assessed with regard to ageing and water sensitivity. The results showed improvements in water sensitivity of HWBESFM containing OPC+PSA and OPC+SF to 66.62% and 65.73%, respectively, compared with the control mix, which demonstrated sensitivity of roughly 55%. Additionally, slight improvements were noticed in ageing resistance on incorporating SCM, those these results remained uncompetitive to traditional SFP mixtures. Overall, this initial investigation of a sustainable approach could, with some improvement, encourage further development and studies in this area.

Solidification of waste excavation clay using reactive magnesia, quicklime, sodium carbonate and early-age oven curing

Kaolin production requires large amounts of excavation waste to be removed, with each tonne of kaolin recovered typically producing up to 9 tonnes of waste. This study introduced quicklime (i.e., CaO), reactive magnesia (i.e., MgO) and sodium carbonate, together with an early-age oven curing regime as a means of re-using kaolin excavation waste to produce more sustainable cementitious materials. The strength development of solidified clay samples was measured and later interpreted by pH tests, porosity measurement, Fourier-Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy-Energy-dispersive X-ray spectroscopy (SEM-EDX). Besides, the environmental impacts with respect to the production of additives for clay solidification were also calculated. The results indicated that the incorporation of CaO and MgO effectively solidified the clay with acceptable compressive strength (CaO group: 12.2 MPa; MgO group: 20.3 MPa after 28 days). Meanwhile, given the strength development of samples investigated in this study, the morphology of hydration phases could be possibly more important than their contents and sample porosity. Furthermore, with the introduction of 3 days of oven curing, MgO took advantage over CaO in clay solidification, which was attributed to the formation of fibrous crystals (i.e., nesquehonite) and fewer micro-cracks. Finally, from a perspective of ‘greenness’ and sustainability, MgO is a more favorable additive than CaO and PC in soil solidification.

Characterisation of ultra-fine fly ash as sustainable cementitious material for masonry construction

The study aims to understand the strength improvement and microstructural behavior of ultra-fine fly ash particles through synthesis and characterization techniques by analyzing the fly ash mortar and masonry prism. The process of grinding alters the particle size and specific surface area but not shown any variation in chemical composition are concluded from the microstructural analysis. The multiphase crystalline structures were found through the X-Ray Diffraction. From XRD, a pattern was incorporated to measure the micro-cracks size decrease and the strain was not obtained for a lattice. The reading shows the good amplification in the use of ultra-fine fly ash blended cement mortar associated with raw fly ash. The ultra-fine fly ash masonry block shows higher compressive strength, higher resistance to shear, higher bonding between two bricks compare to conventional masonry blocks. Overall, investigations show that additional use of 45% ultra-fine fly ash in construction applications without compromising the quality.

The role of zinc in metakaolin-based geopolymers

Geopolymers are low-calcium, sustainable cementitious materials. The role of Zn, a known retardant used in Portland cement, in geopolymer systems is not well understood. This study scrutinises the effect of Zn on metakaolin-based geopolymer reaction mechanisms and kinetics, and investigates the incorporation mechanism of Zn in geopolymer gels. Isothermal calorimetry and X-ray diffraction analyses show that substitution of ZnO (20 mol% c.f. metakaolin) significantly hinders reaction, likely due to preferential formation of a Na/K-Zn containing phase. Solid-state nuclear magnetic resonance spectroscopy shows that Zn2+ partially substitutes for Na+/K+ in charge-balancing sites within the geopolymer gel. Setting time and leaching tests show that the retarding effect of Zn on reaction kinetics is significantly greater in Na-activated geopolymers compared with K-activated geopolymers, whereas Na-activated geopolymers exhibit superior fixation capacity to Zn. A lab-scale experiment demonstrates that metakaolin-based geopolymers are promising candidates for the stabilisation/solidification of Zn-rich hazardous waste.

Response Surface Analysis of the Corrosion Effect of Metakaolin in Reinforced Concrete

Concrete is one of the most utilized construction materials. The use of sustainable cementitious material is one of the new trends in concrete technology. Several cementitious materials have been used as partial and full replacement for cement in concrete. These materials have been used in a bid to improve sustainability and reduce production cost. However, the corrosion effect of these materials has been neglected. The experimental research assessed the corrosion effect of metakaolin on some samples of concrete. This was achieved by evaluating the concrete pore solution. The metakaolin was used as a partial replacement for cement at 0, 10, 20, and 30% replacement which gave the optimum mechanical strength. The concrete pore was extracted through mechanical means. The inhibition efficiency of metakaolin in concrete production was assessed using the and weight loss method by inserting the mild steel in artificial concrete pore solution. A reduction in the corrosion rate was observed at higher percentage addition of metakaolin which signifies an improvement in the inhibition of the developed concrete The relationship between the observed parameters was evaluated using response surface methodology. The result of the analysis showed that a unit increase in time would cause a 0.03 increase in the corrosion rate. Additionally, a unit increase in the temperature will have a 0.065 positive effect on the corrosion rate of mild steel. The R2 value showed that about 89.7% variation in the corrosion rate was accounted for by the effect of the independent variable (time, temperature and metakaolin). The outcome of this research will serve as a guide for construction workers, engineers and other researchers on the corrosion effect of this sustainable supplementary material in concrete technology towards the design and construction of sustainable concrete infrastructure.

Rheological and mechanical characterization of self-compacting concrete with utilization of supplementary sustainable cementitious materials

Self-Compacting Concrete (SCC) being a sustainable high-performance concrete capable of flowing through congested reinforcement and can fill the shuttering without any external energy. The investigation focuses on the effect of waste materials generated from industries on the fresh and mechanical properties of SCC. Experiments were carried out to develop SCC by using Fly Ash (FA) and Ground Granulated Blast Furnace Slag (GGBFS) as Supplementary Cementitious Material (SCM). Light weight Perlite Aggregates (PA) were used as a partial replacement material in M-Sand. Workability tests were conducted to check the rheological properties of developed SCC mix in accordance with the European Federation of National Associations Representing for Concrete (EFNARC) guidelines. An optimal mix was developed satisfying the criteria as per EFNARC. The developed mix design exhibited a significant reduction in cement content. Ordinary Portland Cement (OPC) was replaced with 31% of FA and GGBFS is kept constant at 31%. The specimens were cured in water under ambient temperature. Performance of the developed mix in terms of compressive strength at different ages of 7, 28, 56 and 90 days were also examined. The results showed that SCC developed with industrial wastes provide adequate workability and strength with a substantial reduction in the cement content. Hence, the developed SCC with FA and GGBFS along with PA can be used as a sustainable concrete due to its high strength for the infrastructure development.

Early properties of concrete with alkali-activated fly ash as partial cement replacement

Cement manufacture is one of the reasons for society's increasing carbon dioxide footprint. The development of a sustainable construction material is therefore needed to replace Portland cement fully or partially in building construction applications. Geopolymer concrete is a sustainable cementitious material, which is claimed to reduce carbon dioxide emissions and utilise waste materials such as fly ash, metakaolin and blast-furnace slag. Fly-ash-based geopolymer concrete with an activating solution of a mixture of silica fume, sodium hydroxide and water was investigated. Four Portland cement replacement weight ratios (0%, 5%, 10% and 15% by weight of fly ash) were studied. The effects of the Portland cement replacement on the early geopolymerisation process, compressive strength, modulus of elasticity and Poisson's ratio were investigated. Acoustic emission monitoring results showed that the early geopolymerisation process was enhanced when Portland cement replacement was increased. The compressive strength and modulus of elasticity were significantly increased when the Portland cement ratio increased, while Poisson's ratio was adversely affected.

Development of Sustainable Performance Index (SPI) for Self-Compacting Concretes

Selecting a preferred material among a pool of alternatives to perform as desired is a crucial task for promoting sustainability. Evaluation of material performance considering subjectivity and conflicting criteria is the major concern of stakeholders in the construction and is a Multi-Criteria Decision problem. Investigating the sustainable performance of Supplementary Cementitious Material (SCM) considering multi-dimensional and interdependent target-based criteria is the major concern in decision making. The present study has developed an approach, Sustainable Preference Index (SPI) in selecting the optimum sustainable cementitious material considering fresh and hardened properties, durability, service life and Life-Cycle Cost (LCC) aspects. A case study has been considered to illustrate the approach by varying Fly ash (FA) and Ground Granulated Blast Furnace Slag (GGBS) by 20%, 30%, and 40% of the weight of cement in Self Compacting Concrete (SCC). Among the seven mixes, the sustainable alternative in SCC could be identified based on the SPI. For the alternative GGBS 40% based SCC, the highest SPI is found to be 0.893, which is 30.2% more sustainable than the conventional SCC. This simple and lucid approach will facilitate designers and engineers to prioritize and choose a right cementitious material to achieve sustainability.

Limestone and Calcined Clay-Based Sustainable Cementitious Materials for 3D Concrete Printing: A Fundamental Study of Extrudability and Early-Age Strength Development

The goal of this study is to investigate the effects of different grades of calcined clay on the extrudability and early-age strength development under ambient conditions. Four mix designs were proposed. Three of them contained high, medium, and low grades of calcined clay, respectively, and one was the reference without calcined clay. In terms of extrudability, an extrusion test method based on the ram extruder was introduced to observe the quality of extruded material filaments, and to determine the extrusion pressure of tested materials at different ages. For evaluating the very early-age strength development, the penetration resistance test, the green strength test, and the ultrasonic pulse velocity test were applied. Furthermore, the mechanical properties of the developed mix designs were determined by the compressive strength test at 1, 7 and 28 days. Finally, the main finding of this study was that increasing the metakaolin content in calcined clay could significantly increase the extrusion pressures and green strength, shorten the initial setting time and enhance the compressive strength at 1, 7, and 28 days.

Characterization on the recycling of waste seashells with Portland cement towards sustainable cementitious materials

This work introduces a cleaner production practice of transforming waste seashells into new minerals for sustainable cementitious materials. Waste seashells were recycled into fine powder through regular crushing and ball-milling processes. Multi-scale studies characterized systematically the reaction mechanisms of waste seashell powder in ordinary Portland cement system. Seashell powder was studied as both a cement replacement and an additional mineral filler, and its roles were explored through workability of fresh cement mixtures, hydration of cement, and mechanical behaviors of hardened cement mixtures. The results indicated that seashell powder enhanced the hydration of cement through its physical and chemical interactions with both cement clinker phases and hydration products. The mechanical strength of hardened cement mixtures was directly improved when the seashell powder was used as an additional filler. Additions of seashell powder, either as a cement replacement or an additional filler, modified the rheological behaviors of fresh cement mixtures. The hydrated CSH matrix phases developed with seashell powder were clearly enriched by the embedded well-dispersed nanosized clusters (with diameter around 5–10 nm). Parallel comparisons between seashell powder and limestone powder confirmed the higher surface properties and chemical reactivities of seashell powder than limestone powder in cement system.

Sustainable cementitious materials: The effect of fly ash percentage as a part replacement of portland cement composite (PCC) and curing temperature on the early age strength of fly ash concrete

This research aims to determine the effect of fly ash percentage as a part replacement of Portland cement and curing temperatures to the early age strength of concrete. The percentages of fly ash used were 0, 10 and 15% by cement weight. The cured temperatures were 25, 30 dan 50°C. The concrete specimens were cubes of 150 x 150 x 150 mm3. The cubes, which were cured at 25°C, placed in water tank, while those cured at 30 and 50°C cured in oven until 7 days and then continued in water. The testing was conducted at ages 3, 7, 14 dan 28 days. The results showed that at early ages, the strength of concrete without fly ash cured at 25°C were higher than that of fly ash concrete. The higher level replacement of cement with fly ash, the lower strength of concrete obtained. The higher the curing temperature at earlier age resulted the higher the strength of concrete. The strength of concretes with 10% of fly ash cured at 25, 30 and 50°C at age three days were 15.111, 15.481 and 16.296 MPa respectively. Conversely, the strength of concrete that of cured at higher temperatures at ages 28 days, were lower than that of concretes cured at lower temperature. The results of this research also showed that fly ash could improve the workability of concrete.

High volume fly ash mortar containing nano-calcium carbonate as a sustainable cementitious material: microstructure and strength development

The mechanisms underlying the effects of nano-calcium carbonate (NC) on the strength of high volume fly ash (FA) mortar are discussed. Two NCs are used as 2%, 4%, 6%, and 8% by weight of cementitious materials. Hydrated products of fly ash mortar containing NC was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG) and differential thermal gravity (DTG) analysis. Results indicate that NC could improve strength of FA mortar due to the more rapid growth of hydrated products induced by NC through additional nucleation sites. Corresponding to the highest measured strength of FA mortar, the optimal contents of NC are around 2%. In addition, the presence of 2% NC improved the microstructure of FA mortar after 180 days due to the formation of calcium carbonaluminate hydrate.

Utilization of vegetable fibers for production of reinforced cementitious materials

Vegetable fibers produced from agroindustrial resources in the macro, micro and nanometric scales have been used as reinforcement in cementitious materials. The cellulosic pulp, besides being used as the reinforcing element, is also the processing fiber that is responsible for the filtration system in the Hatcheck method. On the other hand, the nanofibrillated cellulose has the advantage of having good mechanical performance and high specific surface, which contributes to improve the adhesion between fiber and matrix. In the hybrid reinforcement, with micro and nanofibers, the cellulose performs bonding elements with the matrix and acts as stress transfer bridges in the micro and nano-cracking network with the corresponding strengthening and toughening of the cementitious composite. Some strategies are studied to mitigate the degradation of the vegetable fibers used in cost-effective and non-conventional fiber cement, as well as to reach a sustainable fiber cement production. As a practical example, the accelerated carbonation curing at early age is a developing technology to increase the durability of composite materials: it decreases porosity, promotes a higher density in the interface generating a good fiber–matrix adhesion and a better mechanical behavior. Thus, the vegetable fibers are potentially applicable to produce high mechanical performance and sustainable cementitious materials for use in the Civil Construction.

Nanoscale Chemical Degradation Mechanisms of Sulfate Attack in Alkali-activated Slag

Chemically induced material degradation is a major durability issue facing many technologically important materials systems, including conventional and new sustainable cementitious materials. In this study, the nanoscale chemical degradation mechanisms have been elucidated for an amorphous sodium hydroxide-activated slag paste (one type of sustainable cement) exposed to different types of sulfate-bearing solutions (i.e., Na2SO4, MgSO4, and H2SO4), by combining synchrotron-based X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and X-ray pair distribution function (PDF) analysis. The XRD, FTIR, and PDF results show that the chemistry and structure of the paste is essentially immune to Na2SO4 attack, whereas exposure to 5–10 wt % MgSO4 and H2SO4 cause complete disintegration of the main binder gel (i.e., sodium-containing calcium–(alumino)–silicate–hydrate), along with formation of magnesium–silicate–hydrate or silica-rich gels and extensive precipitation of gypsum. These differences a...

Challenges of the growing African cement market – environmental issues, regulative framework, and quality infrastructure requirements

The African cement, concrete and construction business is growing at rapid pace. The cement sales are expected to grow rapidly until 2050. The number of newly built cement plants increases dramatically and in addition more cements are being imported from outside the continent, e.g. from Turkey, Pakistan, Indonesia, and China, driven by overcapacities in the countries of origin. This causes a high number of potentials and challenges at the same time. Newly built cement plants can operate directly at best technological state of the art and thus incorporate more sustainable technologies as well as produce new and more sustainable products such as cements blended with sustainable supplementary cementitious materials such as calcined clays, and industrial or agricultural by products. At the same time the new variety of binding agent as well as the international imports, which are driven by price considerations, make the cement market prone to quality scatter. This puts pressure on the quality control regulations and institutions to ensure safety of construction, healthy application, and environmental safety for the population. The paper presents possible solutions to build up the rapidly increasing African cement production more sustainably than in the rest of the world as well as the related challenges and obstacles that need to be overcome. Based on experiences with a series of pan-African cement testing laboratory proficiency schemes conclusions are made on technical, regulative and political level.

Fiber reinforced mortars based on free Portland-CSA binders under high stress rate

In this paper, dynamic behaviour of fiber reinforced mortars manufactured with innovative binders based on calcium sulphoaluminate cement (CSA), supplementary cementitious materials (SCMs), gypsum (G) and hydrated lime (CH) was investigated. Fly ash (FA) and ground granulated blast furnace slag (GGBFS) were used to develop sustainable Portland-free cementitious materials. Polypropylene structural fibers (1% by mortar volume) were used to reinforce the cementitious matrix. Fresh properties of mortars were evaluated in terms of workability and specific mass. In addition, elastic modulus, compressive and flexural strength were determined up 28 days from casting. The dynamic behaviour was studied by means of Split Hopkinson Tensile bar having 60 mm in diameter. Preliminary dynamic results reported in terms of stress versus crack opening displacement were evaluated and discussed.