Portland Cement Research Articles

تطوير معامل المرونة الفعال للخرسانة الصديقة للبيئة القائمة على مسحوق الزجاج

This study aims to develop an effective modulus of elasticity for eco-concrete using glass powder. Various theoretical models, including VOIGT and REUSS-VOIGT, are compared with experimental results. The REUSS-VOIGT model proved most accurate, particularly for cement replacement (5%-20%) and fine aggregate replacement (up to 25%). The REUSS-VOIGT model closely matches experimental results, especially after 56 days. To achieving sustainable development in the production of Portland cement by conserving natural resources and rationalizing their consumption for future generations. Keywords: Homogenization, Effective Modulus of Elasticity, Eco-concrete, Glass Powder, REUSS/VOIGT Model.

Alkali-fusion as an effective method for activating low-reactivity silicate wastes: A comparative study

Silicate wastes are used as supplementary cementitious materials (SCM) in Portland cement production, and as precursors to produce alkali-activated materials such as geopolymers to lower the environmental impact of construction. The high crystallinity of some of these wastes lowers their reactivity and hence the production of cementing hydrates. This paper includes a comparative analysis of the efficiency of alkali-fusion to activate three distinct types of silicate waste sourced from diverse sectors. The paper underscores the robustness of this method and its applicability in a wide composition range. It provides a solid foundation for the application of alkali-fusion across a wide spectrum of industrial waste types. Fly ash (FA), crop bottom ash (CBA) and aluminium processing sludge (APS); were fused with NaOH at 600 °C. XRD and FTIR analyses revealed that alkali-fusion disrupts highly cross-linked Si-O-Si structures transforming them into more reactive phases (sodium aluminosilicate and sodium silicates). Alkali-fusion is efficient even at low NaOH dosage(15 %). 15 % NaOH-fusion increased the mechanical activity index of FA, CBA and APS by 108.19 %, 494.61 % and 27.96 % respectively. The mineral composition of the wastes changed at 50 % alkali content: quartz was largely digested, and sodium silicate emerged as the dominant phase. After alkali-fusion, dense and compact matrices with rich hydrates were found evidencing the enhancement of the pozzolanic reaction. Alkali-fusion at relatively low temperature (600 °C) is successful in activating low-reactivity silicate waste, transforming the waste into valuable SCMs.

Experimental study on the effect of mixing parameters on the rheological behaviour and micro-flocculation structure of ultrafine Portland cement slurry

The penetration diffusion of ultrafine Portland cement (UPC) slurry is closely related to its rheological behaviour and micro-flocculation structure. To date, there has been a need for more research investigating the impact of mixing parameters on the macro-micro hydrodynamic behaviour of UPC slurries. In this study, a series of macroscopic rheomechanical characterisation tests and microscopic in-situ tests of the flocculation structure of UPC slurries under various mixing parameters were conducted systematically by using a rotational rheometer and a focused beam reflectance measurement (FBRM) system. The effects of mixing speeds and times on the macroscopic shear stress-shear rate curves, rheological patterns, rheomechanical parameters, and the distribution of micro-flocculated particles of UPC slurries were investigated. The results indicate that the macroscopic rheomechanical parameters and microscopic flocculation coefficient of UPC slurry exhibit a decrease with increased slurry mixing speed. However, a “decrease and then increase” trend is observed with increased slurry mixing time. The smaller the powder size of cement and the lower the water-cement ratio of the slurry, the more sensitive the rheomechanical properties of the slurry are to the influence of the mixing parameters. A positive correlation exists between the macroscopic rheomechanical properties of UPC slurry and its microscopic flocculation coefficient. Increasing the slurry mixing speed or prolonging the early mixing time can destroy the microscopic flocculation particles of UPC slurry, a reduction in the flocculation coefficient of the slurry, and an improvement in the macroscopic fluidity properties. The research findings provide a foundation for improving the effectiveness of UPC grouting in the engineering field.

INFLUENCE OF MECHANICAL ACTIVATION ON THE PROPERTIES OF CEMENT-WATER COMPOSITIONS WITH THE ADDITION OF GROUND LIMESTONE

The paper considers the issue related to determining the effect of mechanical activation of a mineral binder on the properties of both hardening and hardened cement-water compositions. The mechanical activation of cement in combination with the consumption of ground limestone, the amount of which was adjusted in the range from 0 to 40 % of the cement mass, is relevant for this study. The effect of mechanical chemical activation of Portland cement only and Portland cement with the addition of 20 and 40 % ground limestone on changing the water-solid ratio of equiviscous compositions was studied. It was shown that mechanical and chemical activation of a cement-water composition has a positive effect on reducing the W/S ratio of equiviscous compositions from 0.42 (no activation) to 0.38 (activation period 180 sec). The obtained experimental results indicate the presence of an induction period of heating of the cement paste both on Portland cement not subject to mechanical activation (this period is approximately 6 hours from the moment of interaction of cement with water) and on Portland cement subject to mechanical activation. In this case, the induction period was no more than 2 hours. Joint mechanical activation of an aqueous mixture of Portland cement and ground limestone ensures acceleration of the hydration processes of the binder, which is confirmed by the intensification of the exothermic heating of the filled cement-mixing compositions. The positive role of mechanical activation is also reflected in the acceleration of the thickening rate of the compositions, which was recorded by the kinetics of the decrease in the diameter of their spread over time. The positive role of mechanical activation in reducing the effective viscosity of cement-containing compositions is confirmed, which ensures a decrease in their water-solid ratio by an average of ‒ 8 ... 10 %. A positive effect of mechanochemical activation of Portland cement with the addition of ground limestone on the strength of cement stone at the age of 3 days has been revealed. Experimental studies indicate that only due to mechanical activation the strength of samples made of cement stone with the addition of ground limestone can be increased by almost 25...30 %.

Simultaneously Enhancing the Dynamic Damping and Static Strength Capabilities of Structures: A Case Study Conducted on Fly Ash-based Geopolymer Concrete Specimens using Modal, Mechanical and Microstructural Investigations

Enhancing both the dynamic damping and static strength of ordinary Portland cement (OPC) concrete simultaneously is a significant challenge. Geopolymer concrete (GPC), particularly fly ash-based GPC, offers a promising alternative. This study explores the relationship between damping and strength in heat-cured, low-calcium fly ash-based GPC using sodium silicate (SS) and sodium hydroxide (SH) activators. The findings reveal that SS activators demonstrate stronger positive correlations between damping and strength compared to SH activators. Microstructural analysis indicated that increasing SS dosage from 55 kg/m³ to 98 kg/m³ resulted in a 17% increase in dynamic damping ratios and a 39% increase in static compressive strength. These results highlight the potential of GPC to surpass OPC concrete in applications requiring both enhanced damping and strength, offering a dual benefit not typically achievable with OPC. The study contributes to a deeper understanding of GPC's capabilities, paving the way for its broader adoption in construction projects.

Improving The Geotechnical Properties of Cohesive Soils Using Portland Cement and Some Composite Polymers in A Selected Location in The City of Tanumah / Basrah Governorate – Southern Iraq

Background: The purpose of this research is to ascertain how adding Portland cement and composite polymers, as well as the ideal ratios between them, will affect cohesive soils' geotechnical characteristics. Materials and Methods: A composite polymer was created by combining three polymers—isocyanide, unsaturated polyester, polyvinyl acetate, and thinner—as well as a solvent. Portland cement was added to the soil at a rate of 5% of the sample weight. Different percentages of the weight of the cement supplied to the sample—5, 10, 15, 20, and 25%—were utilized as the composite polymer. Several geotechnical tests were carried out, including compaction, unconfined compressive strength, California bearing ratio, absorption, and Atterberg's limits, to ascertain the ideal amount of polymer for the aim of improvement. Results: The findings show that adding cement at a rate of 5% by weight of the sample and a polymeric mixture at a rate of 15% by weight of cement can improve the cohesive soil's engineering properties. It was found that the maximum dry density, unconfined compressive strength, and California bearing ratio had increased while the values of the optimal moisture content, absorption rate, liquid limit values, and plasticity index had decreased. Conclusion: The composite polymer used in soil improvement not only improves the geotechnical properties and resistance of the soil, but it also efficiently enhances and activates the effectiveness of cement. When 15% of the sample's weight of cement was composed of composite polymers, the soil's engineering attributes increased the most.

An Experimental Investigation on Nano-Enhanced Tertiary Blended Concrete Incorporating Industrial Wastes

Concrete is a crucial material in the construction industry; however, its production process releases carbon dioxide into the atmosphere. Undoubtedly, the building sector's increasing global interest unveils a challenge to its ability to withstand cement alternatives and manage the resulting outflows. Fly ash, GGBS (ground granulated blast furnace slag), Zeolite, rice husk, silica fume, metakaolin, and various industry by-products can typically replace cement. This research study aims to replace cement with multiple cementitious materials, individually and in combination, to evaluate the strength characteristics of blended concrete. The replacement percentages ranged from 0 to 30% for each substitute material, such as fly ash, GGBS, and Zeolite, and strength tests were done to assess the performance of the modified concrete after 7 and 28 days of water curing. Ordinary Portland Cement (OPC) is used to create M30 and M50 grades of concrete. Similarly, cement was replaced with fly ash, GGBS, and Zeolite in amounts ranging from 10 to 30% for M30 and M50 grades, and their strength was evaluated after 7 and 28 days of curing. The most efficient percentage of substitution for both the concrete grades is determined, and the corresponding replacement ratio is used to produce the blended concrete, which incorporates cement, fly ash, GGBS, and Zeolite. The overall findings reveal that the composite concrete, comprising four binding materials, demonstrated superior strength for the concrete grade compared to alternative substitutes. The optimal mixture ratios for M30 concrete after 28 days consist of 20% fly ash, 20% GGBS, and 10% zeolite. Moreover, different ratios of Zeolite-10%, Fly-Ash-30%, and GGBS-20% were used to produce M50 concrete.

Studies on Alkaline Activator, Manufacturing Methods and Mechanical Properties of Geopolymer Concrete - A Review

Continuous production of cement products, a new environmentally responsible geopolymer material, can reduce CO2 emissions from increased cement production. Compared to ordinary Portland cement (O.P.C.) geopolymer concrete, it has better mechanical strength and corrosion and fire resistance. Most industrial solid wastes and bottom ash from waste incineration are disposed of unevenly, which consumes land resources and negatively affects the ecosystem. The best alternative resource for the synthesis of geopolymer composites is recycling. Metals, pesticides, and other radioactive pollutants are successfully absorbed by geopolymer composites, which is very favorable for the ultimate development of civilization. Therefore, this review has examined essential material parameters, including new properties, compressive strength, flexural strength, elastic Modulus, compressive strength, and split-tensile strength applications. According to the previous experimental results, G.P.C. offered better fresh properties than conventional composites. This review revealed the geopolymerization process, the types of alkaline/alkali activators, synthesis techniques, sources of natural raw materials, and applications of geopolymer concrete. The present work discussed the conceptual framework for the sustainable production of geopolymer materials by evaluating the drawbacks, applications, and restrictions of geopolymer materials and their potential development.

Multifunctional characterization of cement-Sargassum composites for application as bioconstruction materials

Utilizing solid waste biomass developing of construction materials presents an environmental mitigation opportunity by gradually replacing conventional materials that generate diverse ecological impacts. This approach aligns with circular economy and green chemistry principles, promoting the creation of sustainable materials. This research analyzes the use of brown algae from the Sargassum genus for bioconstruction applications through its mix with Portland cement. The mass influx of pelagic Sargassum species onto Caribbean beaches since 2011 has significantly impacted the environment, economy, and human health. The valorization of Sargassum is crucial for effective management and impact reduction. The study encompasses four key stages: (a) collection and processing of the algae, (b) development of a construction material composed of Portland cement and Sargassum at concentrations of 5 wt.% and 7.5 wt.%, (c) multifunctional characterization of the composite material, encompassing physical chemistry and thermal, optical and mechanical properties, and (d) an economic-environmental evaluation of using the construction material for housing in the Mexican Caribbean to enhance thermal insulation and reduce electric energy consumption associated with air conditioning. Test specimens of the composite material reveal compressive strength ranging between 78 and 347 kg/cm2, solar spectrum absorbance between 54% and 70%, and thermal conductivity between 0.65 and 1 W/mK. The economic-environmental analysis indicates that employing the construction material in 5% of households in the state of Quintana Roo, Mexico, could lead to annual reductions in energy consumption of approximately 67 GWh, with savings exceeding US$33,000, and environmental yearly mitigation equivalent to 4.1 TnNOx, 5.2 TnCH4, and 33,262 TnCO2. These results suggest promising prospects for incorporating Sargassum into construction materials, offering potential environmental and economic benefits. The composite material demonstrates optical, thermal, and mechanical functionality.

Stabilization of lateritic soil with Portland cement and crushed granite for pavement base courses

The aim of this work is to propose reconstituted materials, by cement-based improvement of lateritic gravels and joint cement improvement and lithostabilization, that are technically suitable for use in base courses. The study focused on two (02) different lateritic gravels, LG1 with a fine content of 24% and LG2 with a fine content of 15%. For lithostabilization, 0/25 granite crushed stone was used and the cement used was CEM II/B-LL 42.5. For cement improvement, three (03) cement contents (1%; 1.5% and 2%) were studied, and for joint stabilization, the granite crushed content was set at 10%, with only the cement content varying by 1%, 1.5% and 2%. The mixes were obtained by adding the cement mass calculated from the total gravel mass collected and the cement rate studied to the raw gravel or to a mixture of 90% gravel and 10% granite crushed stone. The results of physical-mechanical tests such as the Atterberg limits, Modified Proctor and California bearing index of stabilized materials were analyzed in comparison with the initial values of raw materials without stabilization. The results show that cement increases the plasticity index but improves the bearing capacity of lateritic gravels better than joint stabilization. However, joint stabilization does improve gravel bearing capacity compared with untreated raw gravel. For use as a base course in accordance with CEBTP specifications [3], in addition to the 10% granite crushed content, LG1 must be upgraded to at least 1.5% cement and LG2 to 1%.

Impact of delayed compaction on the geoengineering properties of stabilised pond ash

ABSTRACT The impact of delayed compaction on the geoengineering properties of pond ash (PA) treated with geopolymer, Portland cement, and hydrated lime is presented in this paper. The gradation, compacted dry density (CDD), unconfined compressive strength (UCS), California bearing ratio (CBR), hydraulic conductivity, and compressibility index of PA treated with 3%, 9%, and 15% additive contents were evaluated at 0, 3, 6, 12, 24, 48, and 72 h delay periods. The mineralogical and morphological changes in the stabilised material were assessed using X-ray diffraction and scanning electron microscope analysis. The results show an enhancement in the particle size of PA with delay time due to the development of cementitious products and agglomeration of particles. Delay in compaction causes a reduction in dry density and strength properties, whereas hydraulic conductivity and compressibility index increase with delay time. The formation of cementitious products and agglomeration during delay periods leads to improper compaction and deteriorates the mechanical performance. The formations of both sodium-based geopolymer compounds and calcium-based hydration products contribute to the superior geoengineering properties of geopolymer-stabilised PA compared to cement and lime-stabilised PA, which have Ca-based hydration products alone. The developed mathematical models predict the engineering properties of stabilised PA with higher R-square values (>0.90). Based on this study, it is concluded that the geopolymer is more effective as a stabiliser than lime and cement.

New Methodology for Evaluating Strength Degradation from Temperature Increase in Concrete Hydration under Adiabatic Conditions

Cement-based construction materials, commonly known as “cement concrete”, result from the hydration reaction of cement, which releases heat. Numerous studies have examined the heat of cement hydration and other thermal properties of these materials. However, a significant gap in the literature is the assessment of the impact of the hydration temperature on the material’s strength, particularly compressive strength. This work presents an experimental methodology that consistently estimates the temperature evolution of a mixture used to manufacture concrete or mortar during the first hours of Portland cement hydration. The methodology aims to ensure results that correspond to an infinite medium (adiabatic conditions), where there are no heat losses to the surroundings. Results obtained under adiabatic conditions (simulating an infinite medium) indicate that a ready-made mortar (Portland cement: sand: water; 1:2.5:0.5) can reach temperatures of approximately 100 °C after 48 h of hydration. Under these conditions, compressive strength decreases by up to 20%.

Comparative Study of Mechanical Properties of Self Compacting Concrete Using Binary Pozzolanic Materials

Abstract: The study examined the viability of using waste supplementary cementing materials (SCMs), such as fly ash (FA) and silica fume (SF), as partial replacement of Ordinary Portland cement. The way SCC's fresh properties and hardened were impacted by FA and SF. The study examined the fresh characteristics and hardened characteristics of various distinct SCC mixes using SCC with partial replacement of Ordinary Portland Cement with FA (class F) and SF. First, the cement was replaced by percentages in the mixes 0%, 10%, 15%, 20%, 25%, and 30% by FA and constant replacement of 10% by SF. Then cement was replaced by percentages in the mix with 25% FA constant and 4%, 6%, 8%, 10%, and 12% by SF. For every combination, the water/binder (w/b) ratio was set at 0.43. The EFNARC (Specification and Guidelines for Self-Compacting Concrete) standards were met by the slump flow, T50, and viscosity of the SCC. After 28 days of curing, the blend consisting of 65% PC, 25% FA, and 10% SF had a maximum compressive strength of 41.22 MPa which is 12.07% greater than the compressive strength of the control specimen which is 36.78 MPa. The Split Tensile Strength of the same blend is 4.37% is greater than the control specimen. Non-destructive tests were also performed after 28 days of curing and the regression equations give the excellent relationship between Rebound Number, Ultrasonic Pulse Velocity, and Compressive Strength. This is due to the formation of the proper matrix as the particle size of SF and FA is less than that of cement and the free lime of cement reacts with FA and SF to form C-S-H gel which provides strength.

Incorporation of Nanoalumina in Potassium Feldspar-based Phosphoric Acid Activated Geopolymer Composites: A Sustainable Approach

This study investigates the potential of potassium feldspar-phosphate-based geopolymer concrete as a sustainable replacement to traditional concrete, addressing the environmental concerns associated with CO2 emissions during cement production. While geopolymer concrete offers a promising path towards sustainability, its performance often falls short of Portland cement concrete. This study investigates the use of nanoalumina in improving the performance of geopolymer concrete. A ternary mix was formulated with potassium feldspar powder, metakaolin and rice husk ash, incorporating varying percentages of nanoalumina geopolymer concrete mixes. The mechanical characteristics of the resulting geopolymer composites were assessed through compressive and split tensile strength tests. The findings revealed that a 4% nanoalumina dosage (GC-N4) yielded the most significant improvement in strength and durability. The GC-N4 mix performed superior in all metrics, demonstrating the highest compressive (41.82 MPa) and split tensile (3.7 Mpa) strengths. Reduction in water absorption and durability aspects were also optimum in GC-N4. These results highlight the potential of incorporating nanoalumina into a ternary mix of potassium feldspar powder, metakaolin and rice husk ash to significantly enhance the overall performance of geopolymer concrete, promoting its wider adoption as a sustainable construction material.

РОЛЬ САСО3 У ФОРМУВАННІ МІЦНІСНИХ І ДЕКОРАТИВНИХ ВЛАСТИВОСТЕЙ ПОРОШКОВОГО ЛУЖНО-АКТИВОВАНОГО ШЛАКОПОРТЛАНДЦЕМЕНТНОГО БЕТОНУ

The article discusses approaches to the formation of compositions of alkali-activated decorative Portland slag cements containing Portland cement type CEM1 5...45% with high performance and decorative properties. The optimization of the compositions of decorative alkali-activated Portland slag cements was carried out using statistical methods for designing experiments. Finely dispersed TiO2 and CaCO3 additives with a whiteness of 90% were used as bleaching components. The alkaline component is sodium metasilicate in the form of a non-hygroscopic powder. The research carried out made it possible to obtain decorative Portland slag cements with a whiteness of 45...77%, which allows them to be used to produce colored cements with a wide range of colors from white to black. It has been established that alkali-active decorative Portland slag cements have an activity of 37...59 MPa at the age of 28 days. All compositions have good hardening dynamics and, based on the strength at the age of 2 days  22...36.6 MPa, they can be classified as fast-hardening. Based on them, it is possible to produce dry construction mixtures. All mortar compositions based on alkali-active decorative Portland slag cements demonstrate fairly high frost resistance  F200. This allows them to be used for the manufacture of products and solutions both for indoor use and when exposed to atmospheric influences without loss of design characteristics and decorative appeal. The inherent shrinkage strains of decorative alkali-activated Portland slag cements are 0.51...0.61 mm/m, which eliminates cracking and premature destruction of products. The use of the CaCO3 additive is especially effective for controlling the shrinkage deformations. Thus, the CaCO3 additive performs the functions of not only a decorative component, but also a structure-forming component. Concrete and mortar mixtures can be used to produce decorative products using the traditional method, extrusion, 3D printing on construction printers, etc. And not too long setting times and a rapid increase in strength make it possible to produce products without thermal treatment or with minimal consumption of thermal energy.

Assessing the Durability, Mechanical, and Microstructural Properties of Nanosilica-enhanced Coconut Shell Concrete: A Sustainable Approach

This study explores the properties of concrete as a sustainable substitute for cement through the use of nanosilica in an eco-friendly aggregate system. Daily life generates a larger amount of coconut shell waste from the tropical zone. In India, the yearly deposition of coconut shell is about 80,000 tonnes, which is 6.7% of total agricultural waste. Crushing gravel production emits CO2, which is an environmental concern. Simultaneously, to diminish waste disposal of coconut shell can be effectively utilised as coarse aggregate in lightweight concrete. The conventional concrete (CC) was fully replaced by coconut shell coarse aggregate and crushed gravel sand (Msand) as fine aggregate in plain Portland cement. Nanosilica replaces cement in the conventional blend at 0%, 1%, 2%, 3%, and 4%. This study describes the concrete's hardened properties, such as compressive strength, splitting tensile strength, and flexural strength. Among all the mechanical performances, the N2 blend is significant. The N2 mix exhibits a trend that aligns with the correlation between compressive strength and splitting tensile strength. The transport durability performance related to capillary wick action of the optimum blend (N2 mix) has 0.018 mm/min0.5. The pore filler mechanism and pozzolanicity of 2% NS is more synergic than other combinations. The N2 mix in H2SO4 environment has less mass and strength loss. The N2 blend's morphology is robust relative to the CC mix because of the secondary C-S-H gel and homogeneous, smooth hydrated grain. As a result, the report concludes that using coconut shell as an aggregate in concrete can reduce waste disposal in landfills, while using nanosilica in place of cement can reduce CO2 emissions.

Development of Risk-Based Methodologies for Highway Pavement Construction Inspection

Construction inspection plays a critical role in Portland cement concrete pavement (PCCP) and hot mix asphalt (HMA) pavement projects. To ensure the quality of pavement projects, state departments of transportation (DOTs) in the U.S. typically conduct construction material tests and inspect workmanship processes using quality assurance (QA) programs. Given today’s reality of reduced QA inspection resources such as funding, staff ability, and availability, several state DOTs have used a risk-based inspection (RBI) approach to optimize their QA processes. A thorough review of existing literature revealed limited studies examining RBI methodologies in highway pavement construction projects. The aim of this study is to investigate the use of RBI for pavement construction projects. It employed a triangulation research methodology, including an extensive literature review, a survey questionnaire of 50 state DOTs, focus groups, and a vetting workshop. A list of 16 core items in field inspection for both PCCP and HMA pavement projects was developed and verified. A generic risk rating of these critical inspection activities was determined. Additionally, inspection frequency, documentation effort, and inspector experience associated with these critical inspection activities identified through focus groups and the vetting workshop served as a reference point when conducting RBI for PCCP and HMA pavement projects. This study contributes to the body of knowledge and the highway construction industry by identifying and prioritizing 16 core inspection items for PCCP and HMA pavement construction. Construction project managers and inspectors may benefit from this study by analyzing the risks of core inspection items and implementing appropriate risk mitigation plans.

Evaluation of Cretaceous-Tertiary Limestones and Clay for Portland Cement in Erbil, Kurdistan Region of Iraq

Due to the high demand for construction in the Kurdistan Region of Iraq, it is economically natural resources used to minimize importing from other countries, and to increase working hands. Since, limestone is one of the basic raw materials in the cement industry, for this purpose, in the Harir anticline limestone of the Shiranish Formation was mixed with clay of Fatha Formation, in the Shakrok anticline limestone of the Shiranish Formation mixed with clay of Injana Formation, and in the Binabawi anticline limestone of the Shiranish Formation in mixed with clay of the Mukdadiya Formation, dependent on their suitable nearby site locations for factories from each other. The chemical analysis observed by XRF for specifying the major oxides content of CaO, MgO, SiO2, Al2O3, and Fe2O3. three theoretical mixtures of the cement raw materials showed that they have lower liquid content and higher minimum burning temperature in the burning zone, this problem was solved by adding 0.5% iron ore. The Scanning Electron Microscope and Energy-Dispersive by X-Ray spectroscopy carried out for better observation of clinker phase formation showed that the major phases are alite and belite, which indicates suitable burning conditions. Presence of free lime after burning as shown in SEM is due to high CaO content in the limestone raw material.

A Study of the Influence of Thermoactivated Natural Zeolite on the Hydration of White Cement Mortars.

One trend in the development of building materials is the partial or complete replacement of traditional materials that have a high carbon footprint with eco-friendly ecological raw materials and ingredients. In the present work, the influence of replacing cement with 10 wt% thermally activated natural zeolite on the structural and physical-mechanical characteristics of cured mortars based on white Portland cement and river sand was investigated. The phase compositions were determined by wavelength dispersive X-ray fluorescence (WD-XRF) analysis, X-ray powder diffraction (PXRD), diffuse reflectance infrared Fourier transformed spectroscopy (DRIFTS), and scanning electron microscopy (SEM), as well as thermogravimetric analysis simultaneously with differential scanning calorimetry (TG/DTG-DSC). The results show that the incorporation of zeolite increases the amount of pores accessible with mercury intrusion porosimetry by about 40%, but the measured strengths are also higher by over 13%. When these samples were aged in an aqueous environment from day 28 to day 120, the amount of pores decreased by about 10% and the compressive strength increased by nearly 15%, respectively. The microstructural analysis carried out proves that these results are due to hydration with a low content of crystal water and the realization of pozzolanic reactions that last over time. Replacing some of the white cement with thermally activated natural zeolite results in the formation of a greater variety of crystals, including new crystalline CSH and CSAH phases that allow better intergrowth and interlocking. The results of the investigations allow us to present a plausible reaction mechanism of pozzolanic reactions and of the formation of new crystal hydrate phases. This gives grounds to claim that the replacement of part of the cement with zeolite improves the corrosion resistance of the investigated building solutions against aggressive weathering.

Physical and mechanical properties of special cementitious materials modified by nano-particles

Compared to ordinary Portland cement (OPC), sulphoaluminate/ferroaluminate cement (SAC/FAC) and aluminate cement (CAC) are the most promising repair materials due to their excellent early strengths, but the later strengths of SAC/FAC develop slowly, and the later strengths of CAC are obviously declined. This paper studied the effects of nano-SiO2 and nano-ZnO on the physical properties, mechanical properties and early hydration processes of three special cement-based materials and compared them with OPC-based materials. The strength development and early hydration mechanism were revealed by hydration heat, scanning electron microscopy and X-ray diffraction. The test results showed that with the increasing content of nano-SiO2, the setting time of the four cement pastes was gradually shortened, the fluidity of four fresh mortars was gradually reduced, and their compressive and flexural strengths at all ages were improved to different degrees. Nano-ZnO significantly prolonged the setting time of OPC paste and increased the fluidity of OPC mortar, which had a negative effect on its early compressive and flexural strengths, but enhanced its late strengths. After the addition of 1 % nano-ZnO, the initial and final setting time of OPC were about 12 times and 13.4 times that of ordinary OPC paste, respectively. The effect of incorporating nano-ZnO on the physico-mechanical properties of three special cements was similar to that of nano-SiO2. The strength loss of CAC mortar with two kinds of nanoparticles was greatly reduced. The incorporation of nano-SiO2 and nano-ZnO could promote the hydration process of three special cements, resulting in the denser microstructure and higher crystallinity of hydration products.