Plain Cement Research Articles

Development of eco-friendly binder using waste cement powder-silica fume and micro steel fibres

Interest has grown in recycled cement powder waste’s application in building projects as a workable, long-term solution to environmental issues. This work presents experimental results investigating the behaviour of plain and fibre-reinforced waste cement paste with different volume fraction percentages of micro steel fibres (1% and 2%), where densified micro silica partially replaces 10% of the waste cement. For each mix, the superplasticiser and water-cement ratios were maintained constant. The study involved a number of studies, including flow table inspections, Field emission scanning electron microscopy (FE-SEM) tests, scanning electron microscopy with energy dispersive X-ray (SEM–EDX) testing, compressive and flexural strength assessments, dry density measurements, and ultrasonic tests. These evaluations aimed to analyse the specimens’ mechanical and physical characteristics thoroughly. The results showed that substituting densified micro fume and micro steel fibres (SF) for a certain amount of cement could improve waste cement’s properties. Using 2% of the micro-steel fibres significantly affected the cement paste’s compressive and flexural strengths. Nevertheless, an investigation revealed that the inclusion of fibres resulted in a reduction in the amplitude of the sound waves and a decrease in the stagnation flow. The SEM–EDX tests revealed satisfactory adherence between the cement paste and SF. This clarifies why adding SF causes the compressive strength to increase.

Transforming contaminated biosolids into biochar for a sustainable cement replacement material

Abstract Contaminated biosolids especially with per- and polyfluoroalkyl substances (PFAS) in biosolids pose significant environmental risks, restricting their potential applications and necessitating sustainable solutions to address these challenges. In this context, pyrolysis emerges as a promising technology capable of degrading contaminants while transforming biosolids into useful products like biochar. This study demonstrates the application of pyrolysis at different temperatures of 450–750 °C to investigate its effect on contaminant removal and the properties of the resulting biochars. Subsequently, the biochars were utilized to prepare cement mortars by replacing 0.5, 1, 2, 4, and 6% of cement weight with biochar, and their compressive strengths were determined after 7 days of curing. The findings revealed that biosolids contained significant levels of PFAS, including perfluorooctanesulfonic acid (PFOS), 324 ng/g, perfluorohexanesulfonic acid (PFHxS), 9.15 ng/g, and heavy metals. Pyrolysis at 450 °C effectively degraded most contaminants, including PFAS. The biochar produced at 450 °C exhibited the highest concentrations of inorganic nutrients such as potassium (K), calcium (Ca), nitrogen (N), and phosphorus (P), though their levels decreased with increasing pyrolysis temperature. On the other hand, compressive strength tests for cement mortars with varying proportions of biochar replacement demonstrated that a 0.5% replacement was beneficial for all biochars (except 650 °C—biochar that achieved the maximum compressive strength with 2%). This resulted in a 30–45% increase in compressive strength compared to plain cement mortar. However, increasing the biochar content to 6% significantly reduced compressive strength. Overall, this study highlights the potential of biochar as a sustainable solution for enhancing cement mortar strength while mitigating biosolid contamination. Graphical abstract

Performance of Cement Mortar Mixtures Containing Fine Aggregate and Admixtures

The purpose of this study is to investigate the influence of the cement/sand (c/s) ratio on the behavior of cement mortar. The used c/s ratios in this study were 1:0, 1:0.45, and 1:0.83. The findings of this study showed that increasing the sand content reduces the compressive strength of the mortar mixture by 41.5 and 28.2% for the c/s ratios of 1:0.45, and 1:0.83, compared to the plain cement mortar (c/s: 1:0). The increase in sand content requires more water content to increase the workability and strength of the mixtures. However, the flexural strength slightly increased compared to the control mortar. In addition, to enhance sustainability, the cement was replaced with two waste industrial materials namely, micro silica (MS) and fume treatment plant (FTP) dust by 20% of cement weight. The modified mixtures (c/s: 1:0) also showed reduced strength at the testing age. The compressive strength of the modified mixtures was reduced by 50% and 19% for the FTP and MS-modified mixtures, respectively. On the other hand, the flexural strength was reduced by 19.1 and 30.2% for the FTP and MS-modified mixtures. This reduction can help achieve certain strength requirements by lowering the cement content in cement concrete mixtures.

Insights on the representative elementary volume of plain cement paste from a micromechanical perspective

Insights on the representative elementary volume of plain cement paste from a micromechanical perspective

Analysis on the expansion mechanical characteristics and anchoring force evolution of self-expanding anchorage body

Adding a large proportion of a self-expanding agent11SEA Self-expanding agent (SEA) to a plain cement slurry under limited space conditions can greatly improve its anchoring force. This effect is closely related to the type and dosage of the SEA. Therefore, various types of self expanding cement22SEC Self-expanding cement, which refers to cement mixed with accelerator and a large amount of self-expanding agent(SEC) have been proposed, and the XRD, XRF and basic property testing experiments using a customized mold and steel pipes were used to examine the composition and mechanical properties and the self-expanding cement anchorage body33SEB Self expanding cement anchorage body, which refers to solid formed by the reaction of self expanding cement with a certain proportion of water (SEB). The chemical structure composition, mineral compositions, expansion pressure, uniaxial compressive strength, fundamental mechanical properties, and ultimate anchoring force generated by SEB under different experimental conditions are analyzed. The results showed the following. (1) The expansion pressure of the SEB peaked and then gradually stabilized within 1–2 days. SEA proportions of 5–15 % provided a greater stable expansion pressure. (2) When the dosages of the SEA were within 15 %, adding three types of SEA to plain cement effectively improved the uniaxial compressive strength of the SEB. (3) The SEA greatly improved the anchoring force. The CSA, HSCA, and UEA SEBs had the highest anchoring force when the dosages were 20 %, 20 %, and 15 %. The peak anchoring forces were 190.3, 185.1, and 125.8 kN, respectively, increases of 107.3 %, 101.6 %, and 37.0 % compared to plain cement anchorage body.

Transfer learning for probabilistic localization of hidden cracks in concrete structures

AbstractThe utility of discriminative supervised learning models built using multiple training-data sources is investigated for hidden crack localization in concrete. Feed-forward neural network (FFNN) is chosen as the model architecture, and transfer learning is used to assimilate the information obtained from different sources (computational physics simulations and laboratory experiments). The labeled training data consists of values of a damage index and the known locations of hidden cracks. The classification models need to learn how the presence of damage (hidden cracks) affects the damage index at different sensors for different test conditions. To this end, diagnostic FFNN models are built by sequentially adding and training new hidden layers to assimilate labeled information from computer models (different model geometries, test conditions, crack lengths, crack locations) and laboratory experiments on a plain cement slab. These transfer learning-based models are then used to localize damage in concrete specimens that reflect real-world conditions (i.e., specimens with steel reinforcement and randomly distributed aggregate). The actual damage state in these specimens is determined by extracting cores and performing petrographic studies on the extracted cores. The damage probability estimated by transfer learning-based models is compared with the petrographic damage rating index (DRI) to identify the most suitable approach to train the diagnostic models. The transfer learning-based diagnostic methodology shows promise and could be used in various structural health monitoring applications, where sufficient labeled data are typically not available from a single data source.

Mixed hydrogen and biofuels cement clinker: Characterisation, microstructure, and performance

Over 35 % of the CO2 associated with cement production comes from operational energy. The cement industry needs alternative fuels to meet its net zero emissions target. This study investigated the influence of hydrogen mixed with biofuels, herein designated net zero fuel as an alternative to coal, on the clinker quality and performance of cement produced in an industrial cement plant. Scanning electron microscopy, X-ray diffraction and nuclear magnetic resonance were coupled to study the clinker mineralogy and polymorphs. Hydration and microstructure development in plain and slag blended cements based on the clinker were compared to commercial cement equivalent. The results revealed a lower alite/belite ratio, but a significant proportion of the belite was of the α′H-C2S polymorph. These reacted faster and compensated for the alite/belite ratio. Gel and micro-capillary pores were densified, which reduced total porosity and attained comparable strength to the reference plain and blended cement. This study demonstrates that the investigated net zero fuel-produced clinker meets compositional and strength requirements for plain and blended cement, providing a feasible pathway for the cement industry to lower its operational carbon significantly.

Utilization of incense stick ash as a supplementary cementitious material: Effects on strength, cement chemistry, and sustainability

Incense stick ash (ISA), a by-product generated from the combustion of biomass during religious rituals, presents challenges regarding its high-volume disposal despite some emerging technologies offering avenues for its reuse. This study aims to investigate the feasibility of utilizing ISA as a supplementary cementitious material and its impact on fresh and hardened properties, hydration kinetics, microstructure, and environmental and economic aspects of Portland cement (PC) pastes. Results reveal that incorporating 5–20 % ISA increases the cumulative heat release per gram of PC. Specifically, replacing 5 % of PC with ISA enhances the 28-day compressive strength, with an increase of 19.78 % compared to plain cement paste. However, further elevation in ISA substitution leads to a decline in compressive strength. The utilization of 5 % ISA refines the pore structure of samples and elevates the content of calcium silicate hydrate (C-S-H), particularly the proportion of high-density C-S-H. Additionally, carbonates present in ISA react with AFm to form monocarbon calcium aluminate, which stabilizes AFt and enhances the microstructural compactness of cement paste. Compared to plain cement paste, the paste with 5 % ISA exhibits lower coefficients for the cost of pastes per cubic meter, CO2 emission of pastes per cubic meter, and non-renewable energy consumption, underscoring the effective utilization of ISA and its role in promoting sustainability. This study will facilitate the application of ISA in cement-based materials and provide technical guidance for subsequent research.

Number of Doses of Systemic Antibiotic Prophylaxis May Be Reduced in Cemented Primary Knee Arthroplasty Irrespective of Use of Antibiotic in the Cement: A Multiregistry-Based Meta-Analysis.

The use of systemic antibiotic prophylaxis (SAP) and antibiotic-loaded bone cement (ALBC) is the accepted practice to reduce the risk of periprosthetic joint infection (PJI) in primary total knee arthroplasty (pTKA). However, practice varies internationally. This study's primary aim was to compare the risk of PJI revision after pTKA with ALBC + SAP vs. plain bone cement (PBC) + SAP, and the secondary aim was to assess whether the risk of PJI revision varies with the number of SAP doses. Cohort of 289,926 pTKAs for osteoarthritis from arthroplasty registries in Denmark, New Zealand, Norway, Romania, and United States registered from 2010 to 2020. One-year revision for PJI following pTKA with ALBC + SAP vs. PBC + SAP, and single vs. multiple SAP doses was compared. We computed cumulative percent revision (1 minus Kaplan-Meier) using distributed analysis method and adjusted hazard rate ratios (HRRs) using Cox regression analyses within each registry. Advanced distributed meta-analysis was performed to summarize HRRs from all countries. Among all pTKAs, 64.4% were performed with ALBC + SAP. Each registry reported a 1-year cumulative percent revision for PJI of <1.00% for both pTKAs with ALBC + SAP (0.34%-0.80%) and with PBC + SAP (0.54%-0.69%). The distributed meta-analysis showed HRR = 1.21; (95% confidence interval [CI], 0.79-1.87) for ALBC + SAP compared with PBC + SAP. Similar risk of PJI revision was observed between pTKAs with ALBC + single vs. multiple doses of SAP: 2 doses (0.95; 95% CI, 0.68-1.33), 3 doses (1.09; 95% CI, 0.64-1.87), and 4 doses (1.23; 95% CI, 0.69-2.21). Comparable results were found for the PBC + SAP group except for higher risk of PJI revision with 4 doses of SAP (2.74; 95% CI, 1.11-6.75). ALBC and PBC entailed similar risk of PJI revision when patients received SAP in pTKA, regardless of number of SAP doses. ALBC or PBC used in combination with SAP in pTKAs, with one single preoperative dose of SAP may be sufficient without compromising the patient safety. Level III. See Instructions for Authors for a complete description of levels of evidence.

Novel approach for strengthening of column by external wrapping with Carbon Fiber and Internally Embedded Damper System for resilient infrastructure

Abstract Columns as major structural components, lose strength due to sudden and accidental impacts. Such impacted columns can be restored by retrofitting, which increases their load-carrying capacity and lifespan, rather than reconstructing them. The common method of retrofitting involves externally wrapping the columns with fibre sheets. Numerous research studies have been conducted on enhancing the load-carrying capacity of a column by jacketing it with Fiber Reinforced Polymer (FRP). However, there is a lack of research on retrofitting columns internally to overcome vibrations produced due to impact loading. This paper addresses the retrofitting of a column both internally and externally. The external retrofitting is done by CFRP jacketing, and the internal retrofitting is achieved by developing a damper system to overcome damping forces. The experimental work aims to compare the load-carrying capacity of columns retrofitted internally with dampers and externally with CFRP jackets, with a plain concrete column. Dampers are evaluated based on energy absorption in comparison to plain cement mortar. It was found that energy absorption increased by 50% when the concrete was reinforced with 1mm chopped carbon fibers. Such reinforced concrete behaved as dampers, when placed inside the column to absorb the impact energy leading to a 9% increase in load-carrying capacity. The maximum load-carrying capacity was observed in columns wrapped with CFRP and damped with dampers, showing an increase of 25%. Finite Element Analysis is carried out to compare the experimental results and evaluate the damping property. Retrofitting a new column can enhance its initial load-carrying capacity, this helps in reducing the cross-section and percentage of steel usage in columns, contributing to sustainability. Retrofitting approaches to achieve 9th, 12th, and 13th sustainable goals, this leads to a significant contribution in the construction sector.

Investigation of Sugarcane Bagasse Ash (SBA)-Based Engineered Geopolymer Mortar Reinforced with Coconut Fibre for Engineered Geopolymer Composites

In recent years, there have been growing demand for fibre-reinforced cementitious composites using materials wastes to reduce cost and cement usage in concrete production. Therefore, this study aims to prepare sugarcane bagasse ash (SBA)-based geopolymer reinforced with coconut fibre as a material suitability evaluation for engineered geopolymer composites. The sugarcane baggase ash was characterised for its physical and chemical properties using scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD). The coconut fibres was added at 0%, 1%, 2%, and 3%, while the plain cement mortar was used as the control mix. Both destructive (compressive and tensile strength) and non- destructive test (water absorption, and ultrasonic pulse velocity test) were conducted on the resulting geopolymer mortar. The result of the SBA characterisation showed that the SBA met the ASTM C618 requirement for a pozzolanic material. The addition of 1% fibre to the geopolymer composite resulted in enhanced durability property than the plain cement mortar. The ultrasonic pulse velocity test demonstrated that bagasse ash-based geopolymer composites can be classified as a excellent cementitious material. The study also found the engineered cementitious composite showed better compressive and tensile strength than the plain concrete mortar, while the addition of fibre provided a denser microstructure for additional strength. The optimum fibre content was found at 1% for improved water absorption performance, UPV, and compressive strength. The study concludes that SBA composite reinforced with coconut fibre can provide better alternatives to achieve sustainability in engineered geopolymer concrete applications.

Analysis of Reinforced Concrete Structures by Using Concrete with Heterogeneous Grade with Pre-Fabricated Structural Steel

The purpose of this article is to review the beams made up of reinforced concrete which is added or prepared with by inclusion of Fabrication material in the form of structural steel which can be known as Pre-fabrication steel material. However, here beams were analysed under construction with a pre-fabrication steel cage, and the flexural tests. For columns, the prefabrication columns showed the results in a very positive manner in terms of time and economy. As per the results investigated for columns with pre-fabricated, time was saved by nearly 33.3 % and cost was saved by nearly 7.1% for each. Results were analysed by comparing with a moment of resistance by experimental ultimate moments and theoretical design moments. This method used was an alternative to rebar specimens &amp; had achieved positive strength with very economical sections. Studies regarding dual-grade concrete or both different concrete grades for beams in Plain cement concrete and reinforced concrete reported that low-grade concrete is placed near the neutral axis zone of the beams and flexural behavior of the beams was carried out. Usually, two zones appear: a tension zone at the bottom and a compression zone at the top. Steel is added to the tension zone to absorb the tension caused by the weakening of concrete, however, the strength of the concrete is disregarded in the tension zone relative to the compression zone. The depth of higher-grade concrete increases in the compression zone, and resistance to first crack development also increases.

Reinforcing biomimetic cementitious composites by aligned hierarchical carbon fibers

Cementitious composites reinforced by carbon-based fibers of varied length scales still face limitations of a single dimension, anisotropic alignment, smooth surface, or poor dispersion. In this study, we developed a bioinspired, hierarchical reinforcing structure that enables multiscale coupling of mechanical properties and directional fiber alignment, significantly improving the load-bearing capacity of cementitious composite. The aligned hierarchical reinforcing structure was synthesized by grafting CNTs onto microscale CFs-COOH via an esterification reaction and a nozzle-injected technique. Parameters for synthesizing the CNTs grafted aligned CF (ACF-CNTs) were optimized considering oxidation solutions, grafting techniques, CNTs geometry, and CNTs concentrations. The chemical bond between CF and CNTs was examined by Laser Raman Spectrometer (LRS), Fourier Transform Infrared Spectrometer (FTIR), and X-ray photoelectron spectroscopy (XPS), respectively. Results indicate that CNTs are uniformly and densely grafted onto CF via ester linkage, forming a hierarchical reinforcing structure. Mechanical measurements show that 1 wt% ACF-CNTs results in a maximum flexural strength of 34.76 MPa and a maximum improvement of 297.12 % (compared to plain cement paste) in the biomimetic cementitious composites. Analysis based on fiber alignment, interface transition zone, and failure mode of CF-CNTs/CNTs suggests that multiscale coupling of mechanical properties and directional fiber alignment are the main reinforcing mechanisms.

Analysis of Mechanical Properties of Fiber Reinforced Concrete Using RCC and PCC

The addition of macro fibers to concrete pavements has been used to improve the cracking of concrete pavement, reduce slab thickness and contribute to increasing the joint spacing. A laboratory test was carried out in the study to analyze the impact of fiber reinforced concrete (FRC) on plain cement concrete (PCC) and roller compacted concrete (RCC), determining the flexural strength by performing ASTM-1609 tests and compressive strength by ASTM C-39 tests. Two synthetic fiber types selected with different geometries and different dosages (0.25% and 0.5% by volume) were tested for both RCC and PCC. To examine the effect of fiber contents and property, statistical testing was done using strength-test data. The test result showed that flexural strength was not affected by fibers. As fiber content increased, both residual strength (F600 and F150) and specimen toughness (T150) increased for each fiber type. To the contrary, the compressive strength of specimens with higher fiber contents was lower in every case. Fiber properties including length and shape affected the residual strength of RCC more, than PCC. It is notable that the residual strength of RCC and PCC with the same fiber condition is very similar, even though the mix design and compressive and flexural strengths are different. In this paper, the strength-test data results are discussed, and the factors affecting the test results and the limitations of the testing methods are suggested.

Potential applicability of calcium phosphate modified portland cement paste for geologic sequestration of CO2

In order to increase the integrity of the wellbore which is used to prevent the leakage of supercritical CO2, it is necessary to develop a concrete that is strongly resistant to carbonation. In an environment where the concentration of CO2 is exceptionally high, Ca2+ concentration in portland cement concrete drops significantly due to the rapid consumption of calcium hydroxide, which decreases the stability of the calcium silicate hydrate. In this work, it is hypothesized that if fairly large quantity of the hydration product becomes more thermodynamically stable than calcite, the damage caused by rapid carbonation will certainly be minimized. For this purpose, portland cement system was modified by monocalcium, dicalcium and tricalcium phosphates to produce hydroxyapatite in portland cement paste. According to the experimental results, addition of calcium phosphate produced hydroxyapatite. Among three different calcium phosphates, monocalcium phosphate showed the most significant impact on hydration. It caused faster stiffening and delayed calcium silicate hydration. Although cement pastes modified by calcium phosphates showed less compressive strength than plain cement paste, they showed an excellent durability after exposure to supercritical CO2. It is clear from the results that the potential applicability of calcium phosphate modification in portland cement for geologic sequestration of CO2 was successfully proven.

Comparable bone penetration between antibiotic-loaded and plain bone cement in total knee arthroplasty.

One of the main concerns around the use of antibiotic-loaded bone cement (ALBC) is the potential reduction in the mechanical properties of the cement when antibiotics are admixed. The purpose of this study was to determine whether there is a difference between plain cement and ALBC in terms of radiological intrusion into the bone in total knee arthroplasties (TKAs). Prospective randomized study of 80 consecutive patients who underwent TKA. Depending on the cement used, patients were divided into two groups by a computer-generated randomization programme: the cement without antibiotic (Group 1) or the ALBC (Group 2). Cement intrusion was measured in postoperative radiographs in eight different regions in the tibial component and six regions in the femoral component. The average cement intrusion was similar in both groups (p = nonsignificance [n.s.]). Group 1 (plain cement) had an average cement intrusion in the femur of 1.4 mm (±0.4) and 2.4 mm (±0.4) in the tibia. In Group 2 (ALBC), the average cement intrusion in the femur came to 1.6 (±0.5) and 2.4 mm (±0.5) in the tibia. In 80% of the patients, the cement intrusion in the tibia averaged a minimum of 2 mm, being similar in both groups (p = n.s.). There are no differences in bone intrusion when comparing plain cement to ALBC. Therefore, the use of ALBC in primary TKA may be indicated, achieving optimal bone penetration. Level I.

Antibiotic-loaded bone cement is associated with a reduction of the risk of revision of total knee arthroplasty: Analysis of the Catalan Arthroplasty Register.

The purpose of this study was to analyse the impact on peri-prosthetic joint infection (PJI) rate and prosthetic survival using antibiotic-loaded bone cement (ALBC) versus plain cement during total knee arthroplasty (TKA). A retrospective cohort study was conducted. The main data source was the Catalan Arthroplasty Register (RACat). TKAs with surgery date between 1 January 2011 and 31 December 2020 were analysed and followed up until 31 December 2023. The main variable of interest was the type of cement (ALBC vs. plain cement), and several endpoints (septic revision, aseptic revision, and all-cause revision) were considered. The analysed outcomes were revision rates, survival rates and risk factors' hazard ratios (HR). A total of 22,781 TKAs were analysed, 13,125 (57.6%) of them with plain cement and 9656 (42.4%) with ALBC. The septic revision rate was lower in the ALBC group after 3 months of follow-up (0.52% vs. 0.78%, p value = 0.04). Prosthetic survival with respect to the aseptic revision endpoint was also higher for the ALBC group during the whole follow-up period (~158 months). Regarding risk factors for infection, ALBC showed a protective effect, HR: 0.53 (0.44, 0.63), while sex (being male) and the analysed comorbidities increased the risk. ALBC is associated with a reduction in both the septic revision and the aseptic revision rate after TKA, and thus with higher prosthetic survival. Level III, Therapeutic, retrospective.

Dispersion effect of nano-structure pyrolytic carbon on mechanical, electrical, and microstructural characteristics of cement mortar composite

ABSTRACT In material science, converting waste into nanomaterials by green technologies highlights the interest in producing sustainable carbon nanomaterial (SCN). This study first-ever utilized tyre-char as a Nano-Structure Pyrolytic Carbon (NSPC) to develop electrically conductive composites. Unlike other carbon nanomaterials, the efficiency of NSPC particle as an SCN in developing electrically conductive composites was investigated in terms of dispersion, mechanical, water absorption, electrical resistivity, and microstructure. The results of sedimentation and zeta potential (−19 mV) showed the excellent dispersion of NSPC particle in water with the combined effect of superplasticizer and ultrasonication. The compressive (40.37%) and flexural strength (10.76%) than that of plain cement mortar composite (CMC) is achieved with 2 wt.% and 1.5 wt.% of NSPC particle, respectively. The water absorption rate and volume of permeable voids were reduced, exhibiting less agglomerations. The percolation zone of AC and DC resistivity of NSPC composite ranges between 1 and 2 wt.%, and the established percolation threshold is at 2 wt.%. XRD analysis showed C-S-H formation consistently increased with curing age, and HR-SEM with EDAX analysis exhibits the dense microstructure and well-distributed NSPC particle at the nanoscale. These experimental outcomes significantly enhanced the reliability and provided a framework for tailoring NSPC particle as SCN for developing electrically conductive composite.

Rheology of binary cement paste system blended with silica fume and alccofine

&lt;p&gt;The flow properties of the binary cement paste system added with supplementary cementitious materials, effect of polycarboxylate based superplasticizer dosage and their influence on the yield stress and the plastic viscosity were studied. The cementitious materials under the study are silica fume and alccofine. Both the plain cement and the binary cement paste system were considered and tested. A comparative study between the plain cement paste without any additions, silica fume blended cement paste and alccofine blended cement paste was performed. The addition of cementitious materials varies in the range 10%, 20% and 30% and the superplasticizer dosage varies in the range 0.5%, 1.0%, 1.5%, 2%, 2.5% and 3% in the mini-slump flow test and the saturation point was determined to be 2% in both the cases of silica fume and alccofine. The setting time and compressive strength testing on the cement paste considered the superplasticizer dosage up to saturation point. The flow characteristics are broadly the same among the binary paste systems. The setting time results indicated the increase in setting time with increase in cementitious additions and with increase in superplasticizer dosage. The higher percentage substitution of cement with silica fume and alccofine resulted in decrease in compressive strength due to the simultaneous acceleratory and retarding effects of cementitious additions and the superplasticizer. The results of the rheological measurements revealed that silica fume possess greater elasticity than that of the alccofine which possess greater yield stress and plastic viscosity.&lt;/p&gt;

Chemical and physical effects of the addition of thermochromic VO2 particles to cement

This work aims to deepen the knowledge of systems formed by cement and thermochromic vanadium dioxide particles. Cement paste specimens with 9 % addition of monoclinic VO2 particles show a significant delay of the hydration at early ages with respect to plain cement specimens, seemingly due to the partial inhibition of hydrates precipitation during the first 24 h of reaction. Upon further hydration, a re-activation of the hydration reactions gives rise to a higher mechanical strength and a more refined pore structure in the paste with VO2 addition at 28 days, attributed to the enhanced formation of C–S–H. The stability of the VO2 particles within the matrix is confirmed along the hydration process and provides the cement paste with the associated thermochromic behavior that is demonstrated by a change in the reflection in the near infrared wavelength range upon cooling from 70 °C. The results confirm the viability of producing VO2-based thermochromic cementitious materials for building envelopes. The next steps in their development should target the enhancement of the solar reflectance modulation in order to produce a significant impact in the energy efficiency of buildings and the urban overheating effect.