Cement-based Mixes Research Articles

Investigating Australian Calcined Clays as Supplementary Cementitious Materials

Limestone Calcined Clay Cement (LC3) has become a highlighted research topic over the past decade. Through various research, LC3 demonstrated the capability to supplement portions of cement, highlighting the possibility to decrease CO2 emissions due to the low calcination temperatures and low levels of CO2 released from the material during calcination. At this stage, there is no research into the feasibility of LC3 in any parts of Australia, limited research in finding clay, and incomplete research understanding how low calcination temperatures affect the compressive strength. The results show the feasibility of LC3, where we demonstrated the feasibility of a low calcination temperature of 650 °C and found that various overburden waste clays (clay in quarries and mines that are not needed) across the East Coast of Australia produced comparable compressive strength results to conventional Portland cement-based mixes. The results also indicate that optimising the particle size distribution of the calcined clay enhanced both the workability and compressive strength of the mortars.

An effect of nano alumina and nano titanium di oxide with polypropylene fiber on the concrete: mechanical and durability study

For a long time, researchers have worked to improve the qualities of cement-based mixes. Because of their small size, strong reactivity, and huge surface area, nanoparticles are becoming more and more regarded as one of the greatest substitutes for cement because of their capacity to increase durability and strength. This work presents the results of an experimental investigation into the strength and durability properties of fiber-reinforced concretes with polypropylene (PP) fibers added to the concrete by volume and nano Al2O3 and nano TiO2 are used as partial substitutes for cement. Nano Al2O3 and nano TiO2 particles used ranged in size from 30 to 300 nm. The specimens were cast using cement blended nano Al2O3 and nano TiO2 percentages of 1%, 2%, 3%, and 4% by weight of cement. M55 grade concrete was employed for the casting process. The addition of PP fibers to the concrete was 0.5% by volume. The specimens underwent a battery of mechanical tests, including microstructural testing, compression testing, split tensile strength testing, and rupture modulus testing. Furthermore, tests for durability factors such as porosity, sorptivity, and degradation were conducted, and the findings are presented. By comparing the outcomes, it was shown that the inclusion of 0.5% PP fibers and 2% nano Al2O3 or nano TiO2 improved the mechanical qualities, but a decrease followed this in strength. The findings demonstrated that 2% nano Al2O3 combined with 0.5% PP fiber had a greater mechanical strength than 2% nano TiO2.

Properties of alkali activated cellular lightweight binder blocks with industrial and agro waste

The construction industry is continuously seeking sustainable alternatives to conventional building materials. Alkali-Activated Cellular Lightweight Binder Blocks (AACLBs) present a promising solution by utilizing alkali activation technology to augment the properties of lightweight concrete. This research focuses on optimizing the composition of AACLBs by replacing conventional binders with alkali-activated materials derived from industrial by-products and agro waste with the help of a protein based foaming agent (FA). The industrial waste materials investigated include Fly Ash (F) and Blast Furnace Slag (BFS) while agro waste such as Rice Husk Ash (RHA) are considered as sustainable alternatives. With Sodium Hydroxide (NaOH) and Sodium Silicate (Na2SiO3) as activators, 8 different combinations are adopted in this study. Properties such as density and compressive strength (CS) are analyzed to assess the structural capabilities of the AACLBs and are compared with that of cement-based blends. The alkaline solution to binder ratio is kept constant as 2.5 for two dilution ratios (1:30 & 1:60) and ambient curing is adopted. The target densities for conventional cement-based mixes are set as 1200–1600 kg/m3 and 1500–1800 kg/m3 for alkali-based mixes. The findings show that, the highest CS of 42.76 MPa and a density of 1870 kg/m3 is observed for FB1 combination at a dilution ratio of 1:30. Conversely, the FBR2 combination at a dilution ratio of 1:60 yielded a CS of 21.23 MPa, accompanied by a minimum density of 988 kg/m3.

Silicomanganese fume-based alkali-activated mortar: experimental, statistical, and environmental impact studies.

This paper evaluates the flowability and strength properties of alkali-activated mortar produced using silicomanganese fume (SiMnF) as the sole binder, combined with alkaline activators and sand, cured at room temperature (23 ± 1 °C). A total of 18 mixes were prepared by varying binder content (370, 470, and 570 kg/m3), alkaline activator content (33, 43, and 53% of binder by weight), and NaOH concentration (8 M and 12 M). The SiMnF-based alkali-activated pastes were characterized using SEM, XRD, and FTIR techniques to study morphology, mineral composition, and functional groups, respectively. Statistical modeling, including analysis of variance (ANOVA) and response surface method (RSM), was performed to optimize the mixes, and a life cycle assessment was conducted to evaluate the environmental impact of the developed SiMnF-based alkali-activated mortars (SiMnF-AAM). The experimental results showed that an optimal mix design with 470kg/m3 SiMnF, 43% alkaline activator content, and NaOH concentrations of 8M and 12M achieved the best balance of flow and strength. XRD and FTIR analyses confirmed that Nchwaningite was the primary reaction product, with secondary phases including magnetite, manganese ferrite, and potassium feldspar, influenced by alkali concentration. The SiMnF-based mixtures had a significantly lower CO₂ footprint (0.08kg CO₂/kg) compared to the cement-based mix, with alkali activators being the primary contributors to emissions. The developed SiMnF-AAM mixes, cured at room temperature, exhibited improved workability, mechanical properties, and reduced environmental impact, making them adaptive to real-life applications.

High-volume recycled glass cementitious and geopolymer composites incorporating graphene oxide

This study presents the development of high-volume recycled glass construction materials using recycled glass aggregate (RGA) as a 100 % sand replacement, recycled glass powder (RGP) as 40 wt% of the binder, and 0.1 wt% graphene oxide (GO) as nano-reinforcement. The research investigates the individual and their combined effects on the engineering performance, reaction kinetics (using calorimetry, X-ray diffraction-XRD, Fourier Transform Infrared-FTIR and Thermogravimetric analysis-TGA), and microstructure (Scanning Electron Microscopy/ Energy Dispersive X-ray Spectroscopy-SEM/EDS) for both cementitious and geopolymer systems. The results indicate that while RGA reduces strength and exacerbates alkali-silica reaction (ASR), the presence of 40 wt% RGP significantly mitigates ASR despite a lower strength gain in both systems. Geopolymers exhibit significantly lower ASR expansion compared to cementitious matrices owing to their superior alkali-binding capacity and denser microstructure, which restricts water and alkali ion mobility. 0.1 wt% GO was found to accelerate geopolymerisation, enhancing the strength of geopolymer mixes, but it decreased compressive strength in cement-based mixes due to self-desiccation-induced micro-cracking under ambient curing condition. The study also highlights that cement and metasilicate, as well as slag, are the main contributors to cost and CO2 emissions in cementitious and geopolymer systems, respectively. Overall, geopolymers exhibit a significantly lower global warming potential (< 180 kg CO2-eq/m3) compared to cement-based mixes (> 365 kg CO2-eq/m3) with a comparable cost (190–230 AUD/m3). The results indicate the potential for sustainable construction applications using high volumes of recycled glass, incorporating over 70 % of the mixture by weight.

Design, calibration and performance evaluation of a small-scale 3D printer for accelerating research in additive manufacturing in construction

3D printing in construction presents numerous advantages, such as geometric flexibility, potential cost and time savings, the incorporation of recycled and sustainable materials, and reduced waste, thereby reducing the construction sector's environmental impact. Despite these advantages, the widespread adoption of AM in construction faces hurdles, primarily due to the prohibitive costs of large-scale concrete printers — typically ranging from $180,000 to over $1 million — and technological constraints that impede research and development efforts within the construction sector. To address these challenges, our study focuses on designing, developing, calibrating and evaluating an affordable lab-scale 3D printer specifically tailored for cement-based materials, aiming to lower the entry barrier for AM research in construction. This paper presents a proof-of-concept for a simple, yet functional printing technology that meet the requirements for research studies. The study details the development process, from the conceptual design to the calibration of printing parameters. The development process included the assessment of preliminary extrusion system designs integrated with the motion systems of a fused deposition modeling 3D printer. Subsequently, material studies were carried out to determine optimal material mix compositions and ratios. A comprehensive calibration of printing parameters using statistical analysis was proposed to ensure consistent and quality printing. The printability and applicability of the proposed small-scale 3D printer were assessed by printing samples and testing their thermal properties. Cost analysis showed that the proposed 3D printer, costing $273, offers benefits compared to existing market alternatives. The study illustrates the potential of small-scale 3D printers to facilitate construction research and practices, thereby promoting the development of sustainable construction methods.

Additively manufactured steel reinforcement for small scale reinforced concrete modeling: Tensile and bond behavior

Small scale (∼1:30–1:40) Reinforced Concrete is useful for centrifuge testing. However, manufacturing the reinforcing cages by hand at this scale is practically difficult. This paper suggests that small scale reinforcement can be manufactured using a metal 3D printer. Mechanical properties of 3D printed submillimeter rebars are discussed and compared to properties of typical prototype rebars. Different model concrete mix designs are tested to identify optimal mixes. Pullout tests of rebars with different surface rib configurations embedded in different concrete mixes are discussed.Based on the test results, by modulating the printing parameters it seems feasible to obtain 3D printed submillimeter bars that can be used as physical models of prototype rebars. A gypsum-based model concrete was more similar to prototype concrete than cement-based mixes. Most importantly, bond slip behavior that is comparable to full-scale concrete could be achieved, something that is vital and has never been reported before.

A novel structural and energy cementitious material for nearly-zero energy buildings

A novel material with tunable dynamic insulations, thermal energy storage, and structural properties is presented in this work. The so-presented NRG&STRUCT concrete is a porous concrete made of microencapsulated phase-change materials (mPCM) which are embedded within the cement-based mix. A strength-based theory accounting for the porosity together with a quality-based index, and the mPCM content are the most relevant parameters to control the structural and energy performance in an NRG&STRUCT concrete. The work thus presents the energy performance of a demo-building made of this material. Layer-wise graded NRG&STRUCT concrete are used in external walls. At each layer, the material is characterized by its strength index and mPCM content, which both play the role of design variables to be determined by solving an optimization problem where the objective function is the energy consumption for keeping the indoor thermal comfort, computed by EnergyPlus. These design variables are continuous, allowing the use of gradient-based optimization solvers. The structural stability of the energetically optimal solutions is forced via constraints on minimal density.

Performance of mortar and concrete containing artificial aggregate from cold-bonded sulphidic mine tailings

Repurposing sulphidic tailings in construction products offers a sustainable solution for this mining waste. Aggregates (1–4 mm and 2–8 mm) were produced at pilot scale using cold granulation with minimal cement content (6 wt% CEM III/B + 94 wt% tailings). Superplasticizer dose was optimized in mortar and concrete mixes replacing 17 % and 32 % of natural aggregates. The concretes benefit from the additional buffering capacity from cement hydrates in granules (relevant for carbonation and chloride penetration), but their increased porosity lower freeze–thaw resistance. Cement-based mixes offer a sustainable solution for this waste in applications with moderate or non-structural requirements.

Influence of effective microorganisms on the rheology and fresh state properties of SCMs-based concrete for digital fabrication

A reduction in the cost and anthropogenic CO2 emissions of Portland cement production can be achieved by adding supplementary cementitious materials (SCMs) obtained from industrial origins, like fly ash, silica fume, slagments, and naturally available such as limestone and kaolinitic clay. Replacement of large quantities of cement with SCMs profoundly influences the fresh and mechanical characteristics of structural concrete. This study presents an experimental investigation to evaluate the influence of effective microorganisms (EM) on freshly mixed fly ash- and limestone calcined clay (LC2) cement-based fibre-reinforced printable concrete (FRPC). EM is a mixture of three different microorganisms: photosynthetic bacteria, lactic acid bacteria, and yeast. Its inclusion complements green concrete and is environmentally friendly for a sustainable environment. Four mixes (i.e., fly ash cement-based mix, LC2 cement-based mix, and both mixes induced by EM) were prepared and examined to achieve printable concrete of varying rheological properties, and tested for slump and slump flow, setting/open time, rheological characterisation of various parameters, and buildability performance. The findings from this study revealed that the SCMs and the EM considered exhibited satisfactory material rheological performance and other unique characteristics identified as critical early-age properties for suitable 3D printability. In addition, near zero slumps were displayed for all the mixes and the slump flows were in the range of 140 – 160 mm after standard small slump flow table impact agitation, implying remarkable and adequate results for printable concrete. The penetration, bleeding, and segregation was also reduced when compared with no SCM inclusion. Conclusively, good relationships between the fresh properties and buildability quantification are also presented.

Effect of size variation of fibre-shaped waste tyre rubber as fine aggregate on the ductility of self-compacting concrete.

Abandoning shredded waste tyre rubber (WTR) in cement-based mixes facilitates safe waste tyre disposal and conserves the natural resources used in construction materials. The engineering properties of such environment-friendly materials needed to be evaluated for field applications. This study examined integrating WTR fibre on microstructural, static load, and ductility properties of self-compacting concrete (SCC). The WTR fibre of 0.60-1.18-, 1.18-2.36-, and 2.36-4.75-mm sizes was used as fine aggregate at 10%, 20%, and 30% replacement levels. Microstructural characterisation of hardened concrete specimens was done by scanning electron microscopy. The compressive strength and static modulus of elasticity tests were used to examine static load resistance, while drop weight and rebound impact tests were used to investigate impact load resistance. The water permeability test was performed as a measure of the durability of SCC with WTR fibre. Relationships have been studied between dynamic MOE and impact tests and rebound and drop weight impact testing. The Weibull two-parameter distribution was used to analyse the drop weight test statically. The results show that WTR fibre size variations efficiently lowered the concrete stiffness reducing the brittleness. Furthermore, incorporating WTR fibre improved the impact resistance of SCC.

Fractional factorial design to study admixtures used for 3D concrete printing applications

• The methodology reduces the material required to assess the importance of admixtures. • The same conclusions were drawn following a full and a fractional factorial plan. • Half of the experiments could be avoided, reducing the amount of resources needed. Mortar mix design for 3D printing applications is growing at a fast pace. The array of available materials proposed for such an application creates a lot of opportunities for mix designs. However, it makes the selection between the available options an onerous task to fulfill. The objective of this study is to reduce the material required to assess the importance of admixtures on fresh properties of cement-based mixes. Among the competing objectives required in a mix design for 3D printing applications, the dynamic yield stress and the flow are investigated. The dynamic yield stress of the cement-paste mixtures is measured by a rotary rheometer and the ASTM C1437 flow test is used to measure the spread of the mortar mixes. The spread is correlated with the pumpability of the mixes, whereas the dynamic yield stress indicates the extrudability and the structure deformation of the mixes. The cement used is blended with silica fume. Fine local sand is selected and the admixtures used are a superplasticizer based on synthetic organic polymers, a biopolymer polysaccharide viscosity modifying agent, a nanoclay made of magnesium silicate, crystalline calcium silicate hydrates, and an accelerator with a water-reducing effect. Design of experiments methods are employed. To evaluate the influence of each admixture, the main effects and interactions are measured and the probability plots are graphically illustrating the results. First, an analysis is made on a two-level full factorial design with four factors. The results of the analysis are then compared with a half-fractional factorial design of a resolution IV. A fractional factorial design accurately discriminates the factors and reduce the number of experiments in mortar mix designs for 3D concrete printing applications.

Analysis of the Influence of Crystalline Admixtures at Early Age Performance of Cement-Based Mortar by Electrical Resistance Monitoring.

Crystalline admixtures are employed for waterproofing concrete. This type of admixtures can affect the early age performance of cement-based mixes. The electrical resistance properties of cement have been related to the initial setting time and to the hydration development. This paper proposes a system for remote monitoring of the initial setting time and the first days of the hardening of cement-based mortars to evaluate the effect of the incorporation of crystalline admixtures. The electrical resistance results have been confirmed by other characterization techniques such as thermogravimetric analysis and compressive strength measurements. From the electrical resistance monitoring it has been observed that the incorporation of crystalline admixtures causes a delay in the initial setting time and hydration processes. The measurements also allow to evaluate the influence of the amount of admixture used; thus, being very useful as a tool to define the optimum admixture dosage to be used.

Smart Materials: Cementitious Mortars and PCM Mechanical and Thermal Characterization

Climate change (CC) is predominantly connected to greenhouse gas (GHG) emissions from the construction sector. It is clear how it is necessary to rethink construction materials in order to reduce GHG emissions. Among the various strategies proposed, recent research has investigated the potential of smart materials. This study in particular aims to develop an innovative building component that combines high energy performance with reduced thickness and weight. For this reason, the potential of Phase Change Materials (PCM) in cement-based mixes is investigated, comparing the performance of a traditional mix with two innovative mixes made with the addition of 3% and 7% PCM. This work characterizes the new material, analyzing its mechanical and thermal performance, highlighting how the mix strength decreases as the PCM ratio increases; however, both mixes may be considered suitable for masonry structures and may be classified as M5 and M15. Furthermore, from the analysis of the thermal performance, it emerges that the mix presents good behavior in terms of insulating properties.

Production of reactive magnesia from desalination reject brine and its use as a binder

This study investigated the feasibility of producing reactive MgO cement from reject brine obtained from a desalination plant and evaluated its use as a binder in comparison to a commercial MgO. The mechanical performance of the samples cured under carbonation conditions for up to 28 days were further supported by x-ray diffraction (XRD), thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) and field emission scanning electron microscopy (FESEM) analyses. Samples involving synthetic MgO revealed higher strengths than those with commercial MgO, in line with the higher reactivity of the former. The increased dissolution of synthetic MgO led to its enhanced hydration and carbonation, resulting in samples with denser structures and improved performances. The findings highlighted issues regarding the large-scale production of MgO from reject brine and CO2 emissions of this process. The major environmental impact was associated with the production of the alkali base (NaOH), which could be improved via the identification of sustainable alkali sources used during production. Overall, the production of MgO from reject brine can save natural resources and pave the way for the sequestration of CO2 as stable carbonates in cement-based mixes.

A study on cement-based mixes with partial wood bottom ash replacement

Solid waste management is a global concern, due to the ever-increasing quantities of waste materials. The scarcity of landfill space and economic challenges have urged researchers to utilise waste materials in construction as a potential solution. One such waste material is wood bottom ash that is collected from residential fireplaces. In this study, wood ash (WA) partially replaces cement and sand to produce a controlled low-strength concrete and save raw material and natural resource depletion. The chemical composition properties of WA are determined. The current research considers the effect of WA, varying from 0 to 50% by weight, on cement consistency and setting time, and fineness of cement, in addition to the concrete relative density and temperature. Additionally, the mechanical properties of mortar and concrete mixes, including WA, are investigated. Accordingly, the compressive strength, modulus of elasticity, flexural strength and splitting tensile strength are determined. Specifically, with 20% WA in concrete mixes, for tested standard cylinders at 28 d, the compressive strength, modulus of elasticity, and splitting flexure strength ranged between 10−12 MPa, 17 100−21 800 MPa and 1·2–1·8 MPa, respectively, for cement and sand replacement.

Flexural resistance of the polypropylene fibres reinforced cement mixes with waste material

The polypropylene (PP) fibers in shotcrete has been used for ground support and building strengthening, since several decades. However, the recent trend is to use the waste material in cementbased mixes to produce an eco-friendly material. Such waste material is the incineration fly ash (FA) that is classified as a hazardous product. This study is intended to establish the mechanical properties of fiber reinforced mortar in addition to cement or sand partial replacement by fly ash, in terms of flexural strength testing. The mechanical properties reflect the influence of the dosage of fiber content and the proportion of the fly ash on the flexural strength. The percentage of cement or sand was replaced by 0, 10, 20, and 30% fly ash. The dosage of fibers was 0, 0.6, 1.2, and 1.8 kg/m3. This green mix with fibers provides a partial substitute of cement as it is cheaper, by incorporating waste product, and saving energy consumption in the production. Due to growing interest in sustainable construction, engineers and architects are motivated to choose such materials which are more sustainable.

Coupling the transient plane source method with a dynamically controlled environment to study PCM-doped building materials

In recent years the combination of latent and sensible thermal energy storage processes within passive and active building components has gathered increasing attention among researchers all over the world. All this considered, an ever-increasing hunger for bridging the gap between chemistry-based characterization methods and engineering-scale monitoring solutions is spreading worldwide, with the aim of developing new experimental procedures allowing to test these advanced systems under realistic operative environmental conditions. In this view, the present paper aims at proposing an innovative characterization procedure for real-scale engineered applications with reference to dynamically variable composites, such as PCM-doped cement-based mixes for building envelope applications. Therefore, in this work, thermally enhanced concretes were produced using micro-encapsulated paraffin and their activation was investigated by means of an innovative experimental technique coupling transient plane source method and controlled environmental dynamic forcing. The dynamic-TPS analysis allowed to produce temperature dependent profiles for three basic material thermal properties, i.e. thermal conductivity, thermal diffusivity and volumetric specific heat. Results show that the proposed methodology is capable of detecting PCM activation within the engineered composites during the imposed hygrothermal cycle, where, for example, the effective thermal conductivity of the composites varied between 40 and 90% amid the melting/freezing process. Furthermore, the transient plane source method also showed to be suitable to investigate PCM dispersion within the composites.

PERFORMANCE CHARACTERISTICS OF 3D PRINTING CONSTRUCTION MIXES DEPENDING ON THERMALLYMODIFIED PEAT ADDITIVE

The paper presents the research results on the development of scientifically valid compositions of 3D printing construction mixes with improved performance characteristics. To regulate the physical, mechanical and technological properties of cement-based mixes, thermallymodified peat additive MT-600 is developed. The paper studies the world experience in the construction additive technology field. The experimental results are presented for cement paste and construction mixes with MT-600 additive for 3D printing. It is established that using the proposed fine additive increases the strength of the cement paste at early stages of hardening, which is the determining factor in the formation of building and technical characteristics for 3D printing. The X-ray phase analysis is carried out for the new composition of cement paste modified with MT-600 additive, which allows studying characteristics of the structure and properties of construction mixes during the hardening process.

Sequestration of CO2 in reactive MgO cement-based mixes with enhanced hydration mechanisms

Strength development of reactive MgO cement-based concrete is limited by the low hydration and carbonation of MgO. This study aims to improve the hydration and mechanical performance of carbonated MgO mixes with the introduction of various hydration agents (HAs) at different concentrations. Influence of these HAs on the hydration and carbonation mechanisms under ambient and accelerated curing conditions was evaluated through isothermal calorimetry, TG, XRD and FTIR analyses. Introduction of HAs enabled extensive carbonation and strength development reaching up to ∼60MPa at 28days, which was 107% and 53% higher than the corresponding MgO and PC-based control mixes, respectively.