Properties Of Cementitious Materials Research Articles

Effects of hydrotalcites with different laminate element composition on the properties of sulfoaluminate cement-based materials

Sulfoaluminate cement-based materials (SCBMs) are widely used for grout reinforcement. It is common to use a large water-to-binder ratio in the construction of sulfoaluminate cement-based materials (SAGMs) to obtain good workability and permeability, which results in poor early strength. Nanotechnology has been increasingly employed to enhance the mechanical properties of cementitious materials. Nano Zn-Mg-Al hydrotalcite-like (LDHs) and nano Mg-Al LDHs increased the early compressive strength, while nano Zn-Al LDHs had the opposite effect. However, the reason for this observation remains unclear. In this study, the influence of LDHs structures with different laminar element compositions on the hydration and hardening processes of SCBMs was analysed. The results showed that nano-ZnAl-LDHs, ZnAl-LDHs, and MgAl-LDHs could provide nucleation sites for ettringites. The three hydrotalcite-like materials slowly released different concentrations of zinc and/or magnesium ions and carbonate ions in the cement paste. Zinc ions entered the hydration product of ettringite and aluminum gel and promoted the transformation of amorphous aluminum gel to bayerite, which inhibited the hydration reaction of SCBMs. Magnesium ions could also enter the ettringite, and carbonate ions promoted the formation of calcium carbonate, which facilitated the hydration reaction of SCBMs. The nucleation effect and the release of zinc and/or magnesium ions and carbonate ions acted synergically to influence the hydration rate, pore size distribution, and compressive strength of SCBMs.

Numerical Simulation of Compressive Mechanical Properties of 3D Printed Lattice-Reinforced Cement-Based Composites Based on ABAQUS.

Research has established that the incorporation of 3D-printed lattice structures in cement substrates enhances the mechanical properties of cementitious materials. However, given that 3D-printing materials, notably polymers, exhibit varying degrees of mechanical performance under high-temperature conditions, their efficacy is compromised. Notably, at temperatures reaching 150 °C, these materials soften and lose their load-bearing capacity, necessitating further investigation into their compressive mechanical behavior in such environments. This study evaluates the compressibility of cement materials reinforced with lattice structures made from polyamide 6 (PA6) across different structural configurations and ambient temperatures, employing ABAQUS for simulation. Six distinct 3D-printed lattice designs with equivalent volume but varying configurations were tested under ambient temperatures of 20 °C, 50 °C, and 100 °C to assess their impact on compressive properties. The findings indicate that heightened ambient temperatures significantly diminish the reinforcing effect of 3D-printed materials on the properties of cement-based composites.

Utilizing bio-based and industrial waste aggregates to improve mechanical properties and thermal insulation in lightweight foamed macro polypropylene fibre-reinforced concrete

This research intends to examine the potential of incorporating waste materials in place of coarse aggregates to augment the mechanical characteristics and thermal insulation of lightweight foamed concrete (LWFC), along with the inclusion of polypropylene (PP) fibres. The PP fibre exhibits excellent tensile strength and enhancement on thermal insulation properties of cementitious materials. In this study, eco-friendly bio-based oil palm shell (OPS) and robust solid polyurethane (SPU) aggregates derived from industrial waste were utilized as substitutes for conventional aggregates. Additionally, silica fume was partially incorporated as supplementary cementitious materials. The addition of PP fibre impacted the workability of the LWFC with the inverted slump value decreased by 1.7 %–17.5 %. The inclusion of PP fibre proportion increased from 0 % to 0.5 % revealed a positive result in mechanical properties and thermal insulation performance. The OPSSPU/0.5 showed the significantly increment of 40.4 % compressive strength, 102.9 % of splitting tensile strength, and 70.8 % flexural strength, respectively. The optimum result was obtained in the OPSSPU/0.5 mixture, which exhibited 3.74 MPa residual compressive strength. Furthermore, utilizing PP fibres brought about a significant reduction in thermal conductivity in the environmentally sustainable LWFC, leading to improvements ranging from 0.2 % to 16.3 % when compared to the control composition. Thus, these findings are essential for encouraging the adoption of such practices in the construction industry and contributing to the reduction of environmental impacts associated with sustainable concrete production.

Calcined alunite-modified alkali-sulphate-activated slag as a novel binder for high-performance cemented paste backfill

The free water content and pore structure significantly affect the mechanical properties of cementitious materials. Because of high water-to-cement ratio and low binder dosage, cemented paste backfill (CPB) is characterized by high free water content and high porosity, which lead to a low strength. In this study, calcine alunite (CA) was used to modify the alkali-sulphate-activated slag (ASAS) to synthesis high-strength CPB with low porosity and low free water content. The results show that at dosage ≤ 3%, CA can significantly enhance the strength of ASAS-CPB, and the strengthening effect becomes more prominent as both the dosage and curing time rise. An addition of 3% CA leads to a 184% increase in strength at 14 days. However, excessive CA (5%) reduces 3-day strength by 65%, but provides the greatest strength at 56 days. As the dosage increases up to 3%, the promoting impact of CA on early hydration of ASAS-CPB gradually increases, and the duration of induction stage and acceleration stage gradually decreases. Nevertheless, 5% CA prolongs the duration of induction stage by 921%. Electrical conductivity and volume water content can be used to assessing the hydration process of ASAS-CPB. Besides, the addition of CA can promote the hydration of slag, resulting a greater formation of C-S-H and ettringite. The hydration products fill the pores and transform the macropores into micropores. Furthermore, mechanisms of CA-induced enhancement in strength is discussed. The results of this study can offer a reference for the synthesis of high performance CPB.

Advancing self-cleaning performance in metakaolin-based geopolymers through in-situ zeolite formation and TiO2 integration

The deterioration of self-cleaning properties of cementitious materials upon hydration was addressed by in-situ zeolite formation within metakaolin-based geopolymers. Pastes with varied in-situ zeolite content were formulated by adjusting the Si/Al ratio of initial raw materials and curing temperatures. The impact of in-situ zeolite formation on self-cleaning performance was systematically investigated through phase composition, optical property and microstructure analyses. Zeolite A formation notably enhances self-cleaning performance, despite contributing to higher band energy and lower Urbach energy. The increases in crystalline zeolite amount and matrix porosity enhances mass transfer capacity. The open pore structure of zeolite facilitates the formation of connective channels during particle growth, mitigating the “sheltering” effect of the surrounding media for photocatalysts and ensuring improved self-cleaning performance upon hydration. This study summarizes the synthesis conditions for zeolite A, providing mechanistic insights into in-situ zeolite formation in metakaolin-based geopolymers and emphasizes its promising potential for optimizing self-cleaning properties in cementitious materials.

Impact of Electronic Waste Glass on the Properties of Cementitious Materials

The article analyses the impact of two different types of dispersive glass on cement hydration and compressive strength at 7 and 28 days. The study employed dispersive glass from various LCDs (TV sets, computer monitors, smart phones), characterised by a composition of approximately 8% SrO, and dispersive glass from washing machines, which consists mainly of SiO2, Na2O, and CaO. The chemical composition and particle-size distribution of different types of dispersive glass were analysed. The study compares the effect of electronic waste glass on cement hydration by evaluating the amount and rate of heat released during the process. In addition, the results of X-ray diffraction (XRD), thermogravimetric analysis (TG), and scanning electron microscopy (SEM) are provided. Different types of glass were determined to have a similar effect on the physical and mechanical properties as well as the mineral composition of cementitious samples: density and UPV decrease up to 6% and compressive strength decreases by about 30%, when 5–20% of cement was replaced by glass waste. However, more prominent differences were observed in the workability of the mixtures: the waste glass from home appliances increased the spread by up to 25%, while the waste glass from electronic devices decreased the spread compared to the reference sample by approximately 20%. The mixtures modified with the waste glass of electronic devices had a higher degree of early hydration (96%) due to the higher water absorption of the mixtures compared to the waste glass of home appliances (88%).

Investigation of the effect of graphene on the properties of cementitious materials using various analytical tools

Investigation of the effect of graphene on the properties of cementitious materials using various analytical tools

Non-destructive characterization of pore structure and chloride diffusion coefficient of cementitious materials with modified non-contact electrical resistivity method

The intricate pore structure of cement-based materials passively influences chloride ion transport and mechanical properties. Existing non-contact electrical resistivity measurement (NC-ERM) methods lack precision for rigorous studies. the NC-ERM was upgraded in this research, which is suitable for assessing the pore structure and transport characteristics of hardened cementitious substrates. The results obtained from this method closely correspond to those obtained from CEMHYD3D, Mercury intrusion porosimetry (MIP), and other methods. Additionally, the impact of mixture proportions on the resistivity, pore structure parameters, and chloride ion diffusion coefficient of cementitious materials is discussed. With an increase in sand ratio and sand-to-stone ratio, the resistivity exhibits an initial rise followed by a decline. Chloride diffusion of 5 wt% NaCl-saturated specimens is 1.2–1.3 times higher than 3.5 wt% NaCl. This study provides a novel non-destructive, convenient and accurate method for characterising the pore structure and testing the transport properties of cementitious materials.

Volumetric surface area of natural coarse aggregates by interferometry-3D scanning (microscale) method

Surface (microscale) roughness of coarse aggregates influence the cement suspension’ viscosity and the interfacial bonding strength of concrete, but its characterization method is not consolidated and still a research challenge. 3D scanner determines accurately the shape, volume, but it is incapable of describing the roughness at microscale. Roughness at microscale (surface index – cm2/cm2) can be measured accurately using interferometry, but it cannot describe shape and volume of the particles. Once the volume of aggregate particles may vary 200% and it seems crucial to establish the (micro)roughness per volume (cm2/cm3) to better understand the effects in the properties of cementitious materials. This paper presents a method of obtaining volumetric surface area of coarse aggregates at micrometric scale by joining (cm2/cm3) both techniques. Three types of aggregates were assessed: gneiss, low-grade meta-carbonate (dolomite) and quartzite (gravel), with one hundred particles in the size range of 4.75 mm to 37.5 mm. For coarse aggregates, the larger the particles, the more of their surface area will be influenced by (mesoscale) shape and less by surface (microscale) roughness. However, the smaller the particles, SI index will differ considerably. The surface area determined by the method proposed in this paper provides a good correlation with the methylene blue method.

NOx removal capacity and compressive strength of photocatalytic cementitious materials with various color properties

The photocatalytic cementitious materials (PCM) are expected to alleviate air pollution due to the direct utilization of natural solar energy. However, the color properties of cementitious materials have significant effect on the photocatalytic performance of PCM. In the present study, the colorful PCM is prepared using various colorants. The effect of color properties of cementitious materials on the NOx removal capacity of PCM is researched, and the related mechanism is analyzed by optical analysis. Furthermore, the effect of colorants on the compressive strength of PCM is studied. Results showed that the NOx removal capacity of PCM is decreased by the presence of colorants. As the 5% of black, yellow, red, and blue colorants are used, the NOx removal capacity of PCM is reduced by 73%, 48%, 21%, and 19%, respectively. Both the nano-TiO2 and cement in the PCM can absorb UV light. Colorants could enhance the UV light absorption capacity of cement, leading to a decrease in the UV light absorption of nano-TiO2, which is harmful to the generation of electron-hole pairs. Moreover, the Fe-phase in colorants could improve the surface charge separation resistance of nano-TiO2, limiting the efficiently separated electron-hole pairs. Therefore, the photocatalytic performance of PCM is weakened by the presence of colorants. The compressive strength of PCM is decreased by using colorants, but the reduction ratio at 28 d is no more than 10%, with the content of colorants within 5%. This research can guide the color design of PCM in practical applications.

Study on microstructural and mechanical properties of cementitious materials composed of fly ash and dacite powder

The hydration reaction of mass concrete seriously endangers the structural safety. At present, the concrete production relies excessively on fly ash due to hydration reaction. In view of the problem that the demand of fly ash exceeds the supply, this paper proposes to use dacite powder to partially replace fly ash as the raw material for preparing cementitious materials. Through comprehensive tests and microstructure tests, various properties of dacite powder and fly ash composite cementitious materials are studied. The results show that: 1. The dacite powder with a specific surface area of 650 m2/kg, a fineness of 15% under laser particle size and a ball-milling time of 1.0 h has the best performance. 2. It is advisable to mix dacite powder and fly ash. The total amount of dacite powder should not exceed 30% of the cementitious material. It has the best performance when the amount of dacite powder and fly ash is the same. 3. The alkali activity of aggregate can hardly be inhibited by mixing dacite powder alone. The recommended measures to inhibit the alkali activity of aggregate are: i) mixing more than 20% fly ash alone. ii) mixed with 25% dacite powder and more than 15% fly ash.

Properties of Cementitious Materials Utilizing Seashells as Aggregate or Cement: Prospects and Challenges.

Nowadays, the sustainable development of the construction industry has become a focus of attention. Crushing and grinding waste seashells originating from the fishery industry, such as oyster shells, cockle shells, mussel shells, and scallop shells, into different particle sizes for usage as aggregate and cement in concrete or mortar provides an effective and sustainable solution to environmental problems by reducing natural resource dependence. Numerous studies have attempted to analyze the suitability of waste seashell as a possible alternative to natural aggregates and cement in concrete or mortar. This paper presents an up-to-date review of the characteristics of different types of waste seashell, as well as the physical, mechanical, durability, and other notable functional properties of seashell concrete or mortar. From the outcome of the research, waste seashell could be an inert material, and it is important to conduct a series of proper treatment for a better-quality material. It is also seen from the results that although the mechanical properties of seashell concrete have been reduced, they all meet the required criteria set by various international standards and codes. Therefore, it is recommended that the replacement of seashells as aggregate and cement should not exceed 20% and 5%, respectively. Seashell concrete or mortar would then have sufficient workability and strength for non-structural purposes. However, there is still a lack of investigation concerning the different properties of reinforced concrete members using seashells as the replacement of aggregate or cement. Further innovative research can solidify its utilization towards sustainable development.

Compressive behaviour and microstructure of geopolymer mortar subjected to cryogenic freeze-thaw cycle: Effects of cycles and polypropylene fiber

The in-depth investigation on mechanical and microstructural properties of cementitious materials subjected to cryogenic freeze-thaw cycles (CFTCs) is essential to efficiently improve their resistance to CFTCs. This study examines the effects of CFTCs ranging from 20 °C to −170 °C up to 9 cycles on geopolymer mortars (GPMs), including the role of polypropylene (PP) fiber on their responses to CFTCs. The compressive strength of GPMs initially improved with the CFTCs up to 3 cycles, followed by a decreasing trend with the CFTCs up to 9 cycles. The GPMs with PP fiber exhibited a monotonic and more significant decrease in the compressive strength after exposure to CFTCs. The permeability of GPMs increased with the increasing number of CFTCs due to the increasing cumulative pore volume and deteriorating microstructure, which are also found to be responsible for the decrease in compressive strength. Notably, pores with a diameter of 2500 nm are identified as a critical value in affecting GPMs' compressive strength. Higher proportions of pores with diameter smaller than 2500 nm enhance compressive strength, while pores exceeding the values have the opposite effect. Additionally, the compressive strength tends to decrease with the increase of microcrack attributes including total microcrack area, total microcrack length, and average microcrack width. GPMs with PP fiber exhibited weaker resistance to CFTCs due to the presence of more free water and the negative thermal expansion attribute of PP fiber. This exacerbates the adverse effects of frost-heave stress and thermal-stress on GPMs.

Development of non-contact ultrasonic IoT system for monitoring hardening process of concrete

The objectives of this study are to develop a non-contact ultrasonic IoT (Internet of Things) system and to investigate its applicability in monitoring the hardening process of cementitious materials. The conventional measurement methods, which include contact or embedded sensors with wires, have limited applicability on complex construction sites. Therefore, in this study, we propose the non-contact ultrasonic method for identifying the properties of cementitious materials using the characteristics of the leaky Rayleigh waves and demonstrate the effectiveness of an IoT system in improving the limitations of wired systems. The apparatus developed includes an ultrasonic transmitter, sensor board and operating software. First, we demonstrated that the non-contact ultrasonic IoT system delivers commands up to a distance of 20 m at a Wi-fi strength greater than −70 dBm. Furthermore, experimental validation was performed on three different cementitious materials (cement paste, mortar, and concrete) to investigate the applicability of the system.

Effect of Superabsorbent Polymer (SAP) Size on Microstructure and Compressive Strength of Concrete.

Superabsorbent polymers (SAPs) are hydrophilic, polymeric network materials renowned for their ability to enhance various properties of cementitious materials. This investigation examines the impact of SAP size on the hydration degree, porosity, and compressive strength of cement pastes and concrete under diverse curing conditions and ageing periods. The findings reveal that SAP addition stimulates the hydration of the C2S phase, particularly during the early curing stages, thereby favouring early strength development. However, the effect of SAPs on hydration promotion diminishes as their size increases. Conversely, the size of SAPs affects the hydration range of their action, and the 400 µm SAP demonstrates the most extensive range of hydration enhancement, reaching up to 105 µm. Additionally, SAPs effectively reduce porosity in small pores (4 nm-10 μm), with 200 μm and 400 μm SAPs exhibiting the highest efficacy. While analysing the effects of SAPs on larger pores (>10 μm), the results show that although larger SAPs result in larger average porosity, the total porosity is effectively reduced, particularly in samples incorporating 400 μm SAP. The compressive strength of cement paste, even after 28 days, is slightly reduced following the introduction of SAPs. However, the strength of concrete, due to the naturally occurring pores eliminating the negative effects of the pores produced by SAPs, is significantly increased following the introduction of SAPs, especially 400 µm SAP.

Ultrasonic monitoring of hydration behavior of cement paste doped with triethanolamine using novel piezoelectric ultrasonic transducer

The propagation of ultrasonic wave in cement paste is closely related to its physical properties, and therefore shows a potential application in fields of online monitoring of hydration and hardening properties of the cementitious materials. Here, the hydration characteristics of cement paste doped with triethanolamine were studied based on the ultrasonic transmission method using the tailor-made horizontal omnidirectional piezoelectric ultrasonic transducer. The results show that clear ultrasonic waveforms can be observed at hydration age of 2 h. The dominant frequency of the reception wave is low at early hydration age and shifts towards the high frequency direction with hydration. The amplitude of the head wave increases sharply before hydration of 24 h, and the increasing extent decreases gradually until hydration of 166 h. The hydration process of cement at early hydration age can be classified into three stages based on amplitude changes of the head wave, that is, the induction period before 4 h, the acceleration period during 4–12 h, and the deceleration period after 12 h. The acoustic parameters of cement paste at early hydration age conform well to the logistic function distribution. The research finding might provide a new method to estimate hydration and hardening properties of cementitious materials, especially on large construction sites.

Effect of waste plastic fibers on the printability and mechanical properties of 3D-printed cement mortar

Extensive use and disposal of waste plastic bags have caused significant environmental issues. However, waste plastic bags can be used as fibers to enforce the mechanical properties of cementitious materials. Therefore, the effect of waste plastic fibers on the printability and mechanical properties of 3D-printed cement mortar was investigated in this work. The experiment mainly studied how the parameters of waste-plastic-fiber contents, fiber widths, and printing spacing affected the flowability, buildability, compressive strength, and flexural strength of 3D-printed cement mortar. Additionally, the microstructure of the printed specimens was analyzed by X-ray computed tomography (CT) and scanning electron microscope (SEM). Results showed that the addition of waste plastic fibers improved the flexural strength of 3D-printed mortar to a certain extent, with the maximum value achieved at the fiber content of 0.3%, for the same fiber width and printing spacing. However, as the fiber content increased, the X-CT scan showed that the porosity of the cement mortar gradually increased, resulting in a decrease in its compressive strength. Varying fiber widths had little effect on the mechanical properties of the printed specimens, whereas the spacing between the printing filaments had a significant influence on it. Larger printing spacing lowered the bonding performance between the printing filaments, thereby weakening the mechanical properties of the cement mortar. SEM images revealed that more pores were generated in the printed mortar than in the cast, resulting in the compressive strength of the cast higher than that of the printed. However, the extrusion of the mortar through the nozzle during printing improved the bond strength between the filaments, so the flexural strength of the printed specimens was significantly higher than that of the cast. This study may provide knowledge on recycling waste plastic bags as building materials to alleviate environmental pollution and also reserve resources.

The Use of Natural Zeolites in Cement-Based Construction Materials—A State of the Art Review

Natural zeolite is a honeycomb-structured aluminosilicate mineral with an open crystalline structure which makes it suitable for a variety of applications. Given the beneficial effects of zeolites on the properties of cementitious materials, the present paper aims to summarize the recent findings reported in the scientific literature on the use of zeolites in cement-based construction materials. This paper limits the analysis to natural zeolites. The influence of natural zeolites on the workability and setting time of cement-based construction materials revealed that increasing the zeolite content led to a reduction in workability compared to the control mixes. At the same time, the initial and final setting times of cement pastes showed a decreasing trend with an increase in the replacement percentage. The slow pozzolanic reaction of clinoptilolite zeolite results in lower flexural strength and compressive strength values of mortars at the age of 28 days. Blending zeolites with other supplementary cementitious materials resulted in improved values of the mechanical properties of mortar and concrete. The findings regarding the impact of zeolite on the durability of concrete suggest that zeolite shows promise as a viable alternative to cement, with positive effects on various aspects of durability. The majority of the durability factors are interconnected. The presence of conflicting findings is particularly significant in this context, highlighting the need for a comprehensive approach to address these challenges in the future.

Monitoring the effect of MgO expansive additive on micromechanical properties of cementitious materials using a combined method of EDS-nanoindentation

The effect of MgO expansive additive (MEA) on micromechanical properties is significant for understanding both the expansive and the mechanical behavior of the shrinkage-compensating concrete containing MEA. This study monitored the stiffness of different phases appearing in the shrinkage-compensating cementitious material containing MEA by using a combined method of energy dispersive X-ray spectroscopy (EDS)-nanoindentation. The effect of MEA and hydration time on the calcium silicate hydrates (C-S-H) and portlandite was focused. The MEA weakened the micromechanical properties of C-S-H and portlandite mainly at early ages. Hydration is the main reason responsible for the elastic properties evolution of C-S-H. With a two-step homogenization scheme, the experimentally determined micromechanical properties of individual phases were successfully upscaled to the macroscopic elastic modulus of the material. This study is a pioneering study on uncovering the micromechanical signature of the shrinkage-compensating concrete containing MEA.

Preparation and properties of calcium aluminum silicate hydrate–polycarboxylate nanocomposites (CASH–PCE)

The CSH–PCE additive provides more nucleation area for cement to hydrate more quickly. Al3+ has been proven to enter the CSH structure and influence the composition and morphology. In this paper, CASH–PCE nanocomposites (CPNs) with different Al/Si ratios are synthesized at different PCE concentrations using a co-precipitation method. And the effect of various systems of CPNs on the workability, hydration kinetics, pore structure, and mechanical properties of cementitious materials are studied. In the results, PCE is observed to adsorb onto CASH surfaces, and with an increase in PCE concentration, the adsorption of PCE increases, leading to a reduction in CPNs particle size and an enhancement in the workability of cement. Al3+ can regulate the particle size of CPNs by affecting the adsorption capacity of PCE. The study on the hydration kinetics shows that the smaller particle size of CPNs has a more obvious promoting effect on cement hydration.