Blended Portland Cement Research Articles

Assessing of water absorption on concrete composites containing fly ash up to 30 % in regards to structures completely immersed in water

The studies were carried out to find a relation between important physical property and the main mechanical parameter of concretes containing fly ash (FA) in order to develop indications for the production of durable composites with the addition of this waste. The tests included low volume fly ash concrete (LVFAC). The cements used in the studies were following: ordinary Portland cement (OPC), (FA-00) and two blended Portland cements containing FA in the amount of: 20 %, (FA-20) and 30 % (FA-30). Measurements of water adsorption (wa) by immersion and compressive strength (fcm) of analysed composites have been performed. The microstructure of all three materials was also assessed. Due to the fact that, the methodology of the wa tests was to reflect the conditions prevailing in the case of concrete- and reinforced concrete structures operating below the water table these tests were very significant from both a scientific and engineering point of view. Test results indicated that LVFAC mixes developed 28-day fcm between 45.10 for FA-30–48.96 MPa for FA-20 with a value of 47.51 MPa for the reference concrete. Neverless wa of LVFAC mixes decreased with the increase in FA content. The average values of wa was 4.6 % for FA-30 % and 5.3 % for FA-20, respectively, while for concrete without FA it was 5.0 %. Thus, it was found that wa by immersion was inversely proportional to the fcm. Based on the microstructural studies it was found that this behavior is attributed to reduced pore diameters and densification of cement matrix microstructure in FA-30 concrete. On the other hand concrete of series FA-20 showed a loose and porous microstructure, and wa in this composite increased accordingly.

Improving the sustainability of oil well cementing operations: blending Portland cement with pozzolana

Improving the sustainability of oil well cementing operations: blending Portland cement with pozzolana

Utilization of phosphorus slag as fly ash replacement in low-heat Portland cement blends: Comparative study of hydration behaviors, physical properties, and life-cycle assessment

This paper presents the benefits of utilizing phosphorus slag (PS) to replace fly ash (FA) in low-heat Portland cement (LHPC) blends. After the first three days, PS exhibits worse mechanical properties and lower hydration heat compared to FA, presumably owing to its retarding effect. Meanwhile, the mechanical properties of PS are approached that of FA at 180 days. Based on the Krstulovic-Dabic (K-D) model, the Qmax values of LHPC, L75F25 (where the letters stand for the material and the numerals indicate the composition percentage), L65F35, L75P25, L65P35, and L50F25P25 are: 370.4 J/g, 312.5 J/g, 323.6 J/g, 333.3 J/g, 322.6 J/g, and 238.1 J/g, respectively. The effects of pozzolanic reaction and pore structure refinement of PS are more pronounced than that of FA, resulting in the Qmax of PS being relatively higher compared to FA. The number of gel capillaries (d < 10 nm) in L75P25 is 12% higher compared to L75F25 at 90 days. The pozzolanic reaction in FA is mainly occurred within 3 days to 28 days. However, in PS the corresponding period is from 28 days to 90 days. Furthermore, the synergistic impact between FA and PS in LHPC ternary blends is further decreased the drying shrinkage and cumulative heat, increases the H/LHPC content, and refines the pore structure. L75P25 has the lowest strength-normalized cost, which is 0.069 $/t/MPa ∼ 0.100 $/t/MPa less compared to L75F25. LHPC-FA-PS ternary blends has pronounced advantages on the strength-normalized energy consumption and carbon footprint. The strength-normalized carbon footprint and energy consumption of L50F25P25 are 1.89 kg/t/MPa and 5.57 MJ/t/MPa lower compared to L75F25, respectively.

Use of finely ground basalt as a mineral admixture in blended Portland cement production

Basalt powder is an active mineral admixture used commonly in the production of mixed Portland cement in Vietnam. Addition of basalt powder may improve many important properties of cement and cement concrete: increasing compressive and flexural strength at late age, increasing sulphate sulfate resistance, increasing freeze-thaw resistance, reducing water absorption, and reducing heat of hydration. However, the use of basalt powder with the same fineness as cement currently has the disadvantage of reducing the compressive strength of cement from the initial stage up to 90 days or 180 days. The magnitude of the decrease was greater at earlier ages than at later ages. This disadvantage of basalt power limits its amount that can be added in blended Portland cement production. In theory, increasing the fineness can increase the activity of basalt powder. Therefore, the objective of this study was to evaluate the possibility of using finely ground basalt powder as a mineral admixture in the production of blended Portland cement, by determining the influence of basalt powder of different fineness (Blaine 3600 cm2/g, 4800 cm2/g and 6000 cm2/g) on some properties of Portland cement. The investigated properties of cement included water of consistency, setting time, compressive strength at 1, 3, 7, and 28 days, and soundness. The results show that, increasing the fineness of basalt increased slightly the water demand and setting time of cement. Increasing the fineness of basalt powder increased significantly the strength of cement at early ages and increased less significantly at late ages. Therefore, the use of finely ground basalt can minimize the disadvantage of basalt powder, then allow to increase its content that can be added in the production of blended Portland cement.

Experimental study on some mechanical and physical properties of cement-stabilized rammed earth

Rammed earth is a “green” material that has received a lot of attention in recent times. This paper presents some mechanical and physical properties of cement-stabilized rammed earth, including compressive strength, elastic modulus, and density. The rammed earth was stabilized by blending Portland cement PCB40 with a content in the range of 4-10% (by the weight of the soil). The experimental results show that the mechanical properties of the rammed earth increased significantly with increasing cement content. With the cement content used from 4-10%, equivalent to about 64-171 kg/m3 of the soil, the compressive strength of the rammed earth was varied in the range of 1-2 MPa, the elastic modulus was varied in the range of 182-427 Mpa and the density was varied in the range of 1720-1942 kg/m3. These specifications are suitable for using this material as a building wall structure. The correlation between compressive strength with density and elastic modulus was found through the obtained experimental regression equations.

Effects of ultrafine limestone powder on some properties of Portland cement

Limestone is usually ground with clinker, gypsum and mineral additives to produce blended Portland cement (2,3,4,7). In this case, the main size of limestone is 2030 m, limestone plays a role as filler. However, using ultrafine limestone powder (with the main size is about 23 m) creates many different properties, it becomes a mineral additive to increase the quality of cement. This paper presented some results about the effect of ultrafine limestone powder from Yenbai with a reasonable amount on some properties of Butson portland cement. When we used ultrafine limestone powder with a reasonable amount, the early strength of cement increases 20%; simultaneously, the bleeding of cement decreases.

Novel agricultural waste based hardening accelerator for early strength development of fly ash-based concrete

Rapid urbanization is leading to a rise in demand for precast elements to reduce the time and cost of construction. However, precast elements consume the time to remove formwork during production depends on the early strength development of fresh concrete. On the other hand, thermal power plants produce a significant amount of fly ash, which also cause environmental issues. One solution to this problem is to use fly ash in cement and concrete to enhance their pozzolanic properties and address environmental concerns. However, using fly ash can delay the early strength development of concrete resulting deacceleration in the production cycle of precast elements. To speed up the process, some may opt for chemical-based hardening accelerator and high temperature curing. However, this may negatively impact the hydration kinetics of the concrete, pose environmental risks, and compromise the reinforced concrete’s durability.To overcome such limitations, impurity free C-S-H seed based hardening accelerator was synthesized from agricultural waste product namely, bagasse ash using novel chemical synthesis process which could effectively accelerates the early strength development of concrete without altering the conventional hydration process. The proposed synthesis process provides a platform for the reaction between the target calcium and silicate ions simultaneously eliminating the harmful elements (like chloride etc.) responsible for degradation of health of reinforced concrete structure.In order to study the effectiveness of a synthesized C-S-H seed, a blended ordinary Portland cement (OPC) was prepared by replacing 10%, 15%, and 20% of the cement weight with fly ash. Various amounts of the C-S-H seed were then added to the blend. Presence of developed C-S-H seed effectively reduced the setting time and eliminated the induction period during hydration of fly ash blended cement. Presence of additional seeds effectively reduces the critical free energy of nucleation which in turn accelerates the precipitation of hydration product responsible for the early strength development of fly ash-based concrete. Based on the setting time and heat of hydration analysis, it has been observed that the presence of C-S-H seed has the potential to accelerate the early strength gain process of fly ash-based concrete.

Ductility response of RC beams composed of limestone calcined clay cement (LC3) and polypropylene (PP) fibre

Ordinary Portland Cement (OPC) is distinguished by considerable pollutant emissions and excessive energy and resource consumption. The development of low-clinker blended Portland cement with mineral additives is the most practical and recognisable method of resolving these issues in the cement industry. The traditional OPC consists of 95% clinker. Supplementary Cementitious Materials (SCMs) enhance the OPC by lowering clinker production. To reduce CO2 emissions, an innovative low-carbon cement called Limestone Calcined Clay Cement (LC3) replaces clinker with additional cementitious ingredients (SCMs). Clinker (50): calcined clay, limestone, and gypsum are the primary sources of LC3 cement. Adding Polypropylene (PP) Fibre endorses ductility and reduces the shrinkage cracks. PP Fibre generates a three-dimensional random distribution network structure when mixed with concrete, significantly preventing the creation and growth of micro cracks. PP Fibre can keep water and other potentially hazardous ions out of concrete. The beam specimens were incorporated with a 1.5% volume fraction of PP Fibre randomly distributed through the section. This study focused on LC3 and PP Fibre on the ductility response of RC beams. RC beams tested for the study consisted of Reference RC Beam, Reference RC beam with 1.5% PP Fibre, RC Beam with LC3 cement, and RC Beam with LC3 cement & 1.5% PP Fibre. The size of RC beams is 100 × 150 × 1000 mm, and they underwent four-point bending testing until failure, and the maximum load were recorded. First crack load and first deflection, yield load and yield deflection, ultimate load and ultimate deflection, as well as ductility and failure mechanisms, are all studied parameters. The findings revealed that LC3 and Portland Pozzolana Cement have almost identical compressive strengths (PPC). The addition of 1.5% PP exhibited better performance appreciably. RC beam with 1.5% PP Fibre shows an ultimate strength of 8.0% compared to the Reference RC Beam.

Influence of internal curing on compressive strength and drying shrinkage of super-sulfated cement mortar

The current study aims at assessing the effect of using cold-bonded fly ash based artificial lightweight aggregate (ALWA) as an internal curing (IC) agent on the compressive strength and drying shrinkage of a typical super-sulfated cement (SSC) produced with a mixture of 85% slag, 10% gypsum, and minor amount of 5% blended Portland cement (PCB). The ALWA was used as partial replacement of fine aggregate (FA) at values of 25, 50, 75, and 100 vol.%. Experimental results showed that the ALWA partially replacing FA in range of 25–100 vol.% significantly decreased both the unit weight and dried density of the fresh and hardened IC-SSC mortars at average values of 13.9% and 20.0%, when compared with the reference SSC mortar, respectively. The ALWA increment continuously reduced the compressive strengths of the hardened IC-SSC mortars. But, at 28 days of curing, the hardened IC-SSC mortar containing the ALWA amount partially replacing FA up to 50 vol.% showed compressive strength reaching 89.3%, and comparable or slightly lower drying shrinkage in comparison with the reference SSC mortar without the IC agent.

Volume Deformation and Hydration Behavior of Ordinary Portland Cement/Calcium Sulfoaluminate Cement Blends.

Blends of ordinary Portland cement (OPC) and calcium sulfoaluminate (CSA) cement can be used to adjust the properties of cement for specific applications. In this study, CSA cement was used as a shrinkage-compensating admixture to improve the hydration behavior and performance (compressive strength and drying shrinkage) of OPC; the expansion behavior of the blended cement mortar was evaluate based on the saturation index of ettringite. The experimental results showed that incorporating CSA cement resulted in a delayed effect on the hydration of C3S, shortened the induction periods of the blended cement and decreased the setting time. The CSA cement also improved the early compressive strength and drying shrinkage of the OPC due to its compact microstructure. The drying shrinkage of the OPC mortar decreased by 27.8% when 6% CSA cement was used, but the formation of microcracks due to expansion could negatively impact its late compressive strength development and associated pore structures of the blends when the replacement content of CSA cement exceeded 6 wt.%. The results relevant to the expansion behavior of the CSA cements could induce crystallization stress, enhancing its resistance against shrinkage cracking.

Utilization of artificial lightweight aggregate and unground rice husk ash as internal curing agents to modify performance of super-sulfated cement mortar

This study attempts to utilize cold-bonded fly ash based artificial lightweight aggregate (ALWA) and retrieved unground rice husk ash (URHA) as internal curing (IC) agents for improving performance of typical super-sulfaed cement (SSC) mortar fabricated with ternary mixture of 85% slag, 10% gypsum, and only 5% blended Portland cement (PCB). The ALWA partially replacing fine aggregate (FA) at four values of 25, 50, 75, and 100 vol.% was used. For evaluating impact of using hybrid addition of IC agents on performances of SSC mortars, the ALWA amount after being optimized was partially replaced by URHA at four levels of 25, 50, 75, and 100 vol.%. Experimental results showed that, ALWA partially replacing FA up to 50 vol.% led to the SSC mortars with remarkably increased workability and uncompromised impacts on the strengths and durability. Addition of URHA partially replacing ALWA significantly improved the fresh properties and flexural strength but it negatively impacted the durability performances of the resultant SSC mortars in terms of increased water absorption, decreased UPV, and increased drying shrinkage.

Hydration and microstructure of ternary high-ferrite Portland cement blends incorporating a large amount of limestone powder and fly ash

This paper studied the mechanical properties, hydration process, and microstructure of ternary high-ferrite Portland cement (HFC) blends with replacement at levels up to 50 % with limestone powder (LP) and fly ash (FA). Two mechanisms, synergy and negative effects between LP and FA are observed in ternary HFC-LP-FA blends. The synergistic effects between LP and FA in ternary HFC blends mainly exhibit improving flexural strengths, improving compressive strengths before 28 days, decreasing drying shrinkage and cumulative heat, accelerating the crystal nucleation and growth process (NG), stabilizing the ettringite (AFt) phase, prolonging polymerization of alumino-silicate chains, and refining the pore size distribution, etc. However, the synergistic effect between LP and FA in ternary HFC blends cannot compensate for the dilution effect caused by a large amount of LP and FA replacement. The adverse effects between LP and FA in ternary HFC blends are emerged and mainly exhibited decreasing in compressive strengths after 28 days and increasing total porosity percentages. LP plays a predominant role at an early age (before 28 days) in HFC blends and increases the cumulative heat; Specifically the cumulative heat of LP25 (25 indicates percentage replacement of HFC) before 10 h is 2.2 J/g higher compared to HFC. In addition, a rapid increase of bound water is emerged from 3 days to 28 days, for instance the bound water content in LP25 increases by 55.9 % from 3 days to 28 days. It is attributed to the nucleation effect of LP providing more nucleation sites and accelerating NG process. LP in HFC blends leads to the formation of monocarbonate and AFt phase trends to stabilization. FA plays a predominant role at the later hydration age (from 28 days to 90 days) in HFC blends attributing its pozzolanic reaction. Furthermore, the synergistic effects between FA and LP in ternary HFC blends are mainly occurred at a later age.

Utilization of silica-enriched filter cake industry by-products as partial ordinary portland cement replacement

In recent years, industrial byproducts have been converted into useful and valuable commercial items. Reusing these byproducts plays a crucial role to ensure the circular economy and thereby safeguard the environmental impacts. In Ethiopia, the Aluminate Sulphate chemical factory disposes of filter-cake waste materials in landfills that have high silica content. The factory is using pure kaolin and other raw materials for the production of Aluminum Sulphate and Sulphuric Acid by burning at high temperatures. By-products materials were collected from the factory and then calcined (post-treated) at 600 °C for 2h in a muffle furnace. From Atomic Absorption Spectrometry measurement result, it is confirmed that the post-treated (at 600 °C/2h) silica-enriched filter-cake waste materials have a similar composition to Metakaolin (MK). Post-treated filter cake (named MK) became more amorphous having high reactive silica with very low impurities as it was calcined and quenched rapidly. In this study, the properties of blended Ordinary Portland Cement (OPC)-mortar samples were investigated with the addition of heat-treated filter cake waste materials (0%–20%) as a partial OPC replacement. X-ray diffraction, Fourier Transform-Infrared Spectroscopy, Differential Thermal Analysis, Scanning Electron Microscope, and Atomic Absorption Spectrometry were used to investigate the properties of mortar samples that contain post-treated filter-cake (MK) materials and OPC-cement. The flexural and compressive strengths of 10% MK + 90% OPC-mortar samples were enhanced at early curing ages, 7 & 28 days. Moreover, the flexural and compressive strengths of OPC mortars with 15% MK have been improved at 28 days of curing age. However, 20% MK + 80% OPC blended mortars have not shown any improvement in mechanical properties. Setting time, soundness, water absorption, and apparent porosity of cement pastes with the addition of post-treated filter cake (MK) are also analyzed.

One-part pastes and mortars of CaO-Na2CO3 activated blast furnace slag: Microstructural evolution, cost and CO2 emissions

The mechanical properties and a thorough characterization of the reaction products were studied in one-part blast furnace slag (BFS) binders activated with 4, 6 and 8 % of a blend of CaO-Na2CO3 (with molar ratios of 1:1) in relation to the BFS. Pastes and mortars were cured for 24 h at 20 °C or 60 °C; with subsequent exposure at 20 °C up to 90 days. The compressive strength indicated that curing at 20 °C was beneficial for the advancement of the reactions; binders with 8 % CaO-Na2CO3 developed 45 MPa after 90 days, while the other regime reached 35 MPa. Mortars with aggregate:binder proportions of 2:1 and 3:1 developed 24 MPa and 21 MPa at 28 days, respectively. XRD, thermal analysis, SEM, FT-IR and 29Si and 27Al NMR evidenced the consolidation of microstructures with low porosity, formed by C-(A-)S-H-type gel, hydrotalcite phases and calcite; the later occurred by reaction of Ca2+ and CO32− ions supplied by the alkaline activator. The assessed binders are environmentally friendly and cost effective compared to a blended Portland cement (BPC) paste and mortar.

Limestone and class C fly ash blends activated with binary alkalis of Na2CO3–NaOH and MgO–NaOH: Reaction products and environmental impact

Alternative alkaline cements made with composite precursors of limestone (LS) powder and class-C fly ash, activated with commercial powdered sodium silicate or alternative activators of blends of Na2CO3–NaOH and MgO–NaOH were investigated. The limestone-fly ash ratios were of 75–25, 50-50 and 25–75 and the alkaline activators were added at 6, 8 and 10 wt % relative to the total mass of precursors. As the limestone-fly ash ratio decreased, the compressive strength increased, and dosages of activators at 8 and 10% favored high strength gains. The use of Na2CO3–NaOH and MgO–NaOH was more effective than the solid sodium silicate. The curing temperature also influenced the strength; samples cured at 40 °C reached 32 MPa at 28-day with an LS-fly ash ratio of 50-50 and 10% Na2CO3–NaOH, while those activated with 10% MgO–NaOH reached 34 MPa. Thermal analysis (TGA/DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) indicated the formation of C,N-(A)-S-H, M-S-H gel, hydrotalcite, and carbonated phases of gaylussite and pirssonite. By using 50 wt% LS a reduction of 80% CO2 emissions can be achieved compared to a Blended Portland cement paste of similar strength, as also proven by two prepared mortars that developed 28-days strengths of 17–19 MPa.

New Method for the Solidification of High-Concentration Radioactive Borate Solution by Cement-Based Materials

Cement is widely used for the solidification of low- and intermediate-level radioactive waste materials. Radioactive borate solution with a high concentration of boron is one of the main radioactive wastes produced in nuclear stations. It is difficult to solidify this solution by using cement because borate has a great inhibitory effect on the cement hydration process. In this study, the hydration kinetics, strength, durability, phase assemblage, and transportation and transformation of the silicon of the paste that blended Portland cement with 5 M borate solution were investigated. After the addition of sodium hydroxide and sodium metasilicate to the paste, the cement hydration process was restarted, and the 28-days strength of samples met the requirements of the Chinese standard. The mechanism of overcoming the retardation of cement hydration by the borate solution was attributed to the formation of calcium metaborate, ettringite, portlandite, and calcium silicate hydrate with the restarting of cement hydration, without the formation of ulexite.

Printability, Thermal and Compressive Strength Properties of Cementitious Materials: A Comparative Study with Silica Fume and Limestone

Over the past decade, 3D printing in the construction industry has received worldwide attention and developed rapidly. The research and development of cement and concrete products has also become quite well-established over the years, while other sustainable materials receive considerably lower attention in comparison. This study aims to investigate the influence of the two most commonly used sustainable cementitious materials i.e., silica fume and limestone powder, on printability, thermal and mechanical properties of fly ash-Portland cement blends. Ternary blends containing Portland cement, fly ash and silica fume or limestone powder are prepared, whereas phase change material (PCM) is introduced to improve the thermal behavior. Based on the rheological properties and concurrent 3D concrete printing, improved buildability of the modified mixtures is linked to their static yield stress. Anisotropic mechanical properties are observed for 3D printed specimens, while cast specimens exhibit a maximum 41% higher compressive strength due to better material compaction. It is clear from the results that addition of silica fume and limestone powder ranged from 5% to 10%, reducing the anisotropic mechanical properties (maximum 71% and 68% reduction in anisotropic factor, respectively) in the printed specimens. The PCM addition ranged from 5% to 10% and improved thermal performance of the mixtures, as measured by a decrease in thermal conductivity (9% and 13%) and an increase in volumetric heat capacity (9% and 10%), respectively. However, the PCM-containing mixtures show around 29% reduction in compressive strength, compared to the control specimen, which necessitates new material design considering matrix strengthening methods.

Evaluation on comprehensive properties and bonding performance of practical slag-fly ash blending based alkali-activated material

Alkali-activated materials have been considered as the potential alternative repair materials to persuade concept of sustainability due to low energy consumption. Ecological benefits increased on their applications have been associated with utilization of more environmental-friendly chemical activator. The current study dealt with engineering and drying shrinkage performances of an alkali-activated blending of slag and low calcium Class F fly ash (FFA) paste (AASF) with sodium hydroxide (NaOH) and also its’ bonding performance with blended Portland cement (PCB). Effects of Na 2 O concentration varied at four values of 3, 4, 6, and 8 mass.% of total solid fraction and FFA addition partially replacing slag at three values of 10, 30, and 50 mass.% on engineering performances of the AASF pastes were initially evaluated. After optimizing analysis, selected AASF mixtures were used for assessing their bonding performances with the PCB paste at equivalent 7-day compressive strength grade. Experimental results showed that the concentration of Na 2 O in range of 4–6 mass.% of total solid was considered as the optimum value to produce the practical AASF pastes with the best 28-day compressive strengths. But, the increase in Na 2 O concentration in the optimized range negatively impacted drying shrinkage and bonding performance of the resultant AASF, which was in opposite to the effect of FFA addition partially replacing slag in range of 10–30 mass.%. • Comprehensive engineering properties and bonding performance of slag-fly ash blending based AAM based repair material were evaluated. • Concentration of Na 2 O negatively impacted drying shrinkage and bonding performance of AAM. • Fly ash addition significantly improved drying shrinkage and bonding performance of AAM.

Evaluation of Corrosion Resistance of Steel Reinforced Concrete Containing Ordinary Portland Cement Blended with Wheat Ash and Blast Furnace Slags as Mineral Admixture Under Simulated Marine Condition

Evaluation of Corrosion Resistance of Steel Reinforced Concrete Containing Ordinary Portland Cement Blended with Wheat Ash and Blast Furnace Slags as Mineral Admixture Under Simulated Marine Condition

Influence of calcined medium grade clay on the properties of Portland cement pastes

ABSTRACT In the recent decades, the composition of Portland cements has undergone significant changes related to an increase in the range and content of supplementary cementitious materials following development of composite and multicomposite cements. The development of these binders that meet the requirements of sustainability requires the expansion and adaptation of the mineral resource base of cement industry to the production of low-emission binders with a gradual decrease of resource and energy intensities. Efforts to find the widespread sources of pozzolans providing high reactivity and physical–chemical stability have led to intensive studies on thermally treated clays of various chemical–mineralogical composition and their industrial adoption. Due to scarcity and high cost of kaolin clays, great attention is given to medium- and low-grade clays. This article reports on a study to evaluate the effect of calcined clay with 52% of clay minerals on the properties of fresh and hardened pastes, in particular on the resistance to sodium sulfate and nitric acid attacks. The reaction products assemblage of the blended Portland cement pastes was investigated by XRD and thermal analyses. The hardened Portland cement pastes incorporated with thermally treated clay demonstrated better durability performance compared to reference ones.