Partial Replacement Of Portland Cement Research Articles

Suitability and Utilization of Neutralized Red Mud and Hydrated Lime as a Partial Replacement of Cement in Concrete

Abstract: The aim of present work is to check the suitability and utilization of neutralized red mud and hydrated lime as a partial replacement of Portland cement in concrete. To develop concrete mix design with industrial waste red mud and hydrated lime. the workability of the concrete, compressive strength, Split tensile strength of the concrete and flexural strength of the concrete is determined and comparative study is done.

Strength and Durability Parameters of Brick Aggregate Concrete Incorporating Rice Husk Ash as a Partial Replacement of Cement

This study assessed the strength and durability parameters of brick aggregate concrete (BAC) incorporating rice husk ash (RHA) as a partial replacement of cement. For this, concrete cylinders (100 mm × 200 mm) were made with 0% (control) to 25% RHA as a partial replacement of ordinary Portland cement (OPC) at a mix proportion of 1 : 1.5 : 3 and a water-to-binder (w/b) ratio of 0.50. Specimens were immersed separately in normal water, 3% sodium chloride (NaCl), 5% sodium sulfate (Na2SO4), 5% magnesium sulfate (MgSO4), 1% hydrochloric acid (HCl), and 1% sulfuric acid (H2SO4) solutions for several immersion periods. The slump test results indicated that the workability of BAC containing RHA (RBAC) decreased about 29.69%–75.02% compared to control (0% RHA). After 90 days, the BAC containing RHA (up to 15% replacement) was found approximately 2.28%–6.64% greater compressive strength than that of control concrete. In addition, water absorption and porosity of RBAC were around 17.59%–40.73% and 12.12%–35.68% lower than that of control concrete, respectively. Similarly, RBAC (up to 25% replacement) exhibited roughly 35.62%–54.79% higher resistance against chloride attack and 0.39%–4.56% better resistance against Na2SO4 attack (up to 15% replacement), however, it exhibited inferior resistance against MgSO4 attack compared to control. Meanwhile, BAC with 10% RHA showed about 5.35% and 1.00% superior performance than that of control concrete against HCl and H2SO4 attack, respectively. The relationships between the strength and durability parameters of RBAC also suggested that RHA contributes to improving the strength and durability parameters of BAC.

Shear Strength of Nano Silica High-Strength Reinforced Concrete Beams.

In this study, the shear strength of sixteen full-scale over-reinforced concrete beams with and without nano silica (NS), constructed from high-strength concrete (HSC), was investigated both experimentally and analytically. Nano silica was used as a partial replacement for Portland cement. According to the NS ratio, the tested beams were divided into four groups: 0%, 1%, 2%, and 3%. Shear span to effective depth (a/d) ratios of 1.5 and 2.5 were used in each group, and two different stirrups ratios (ρv) were employed as 0% and 0.38%. The shear strength provisions used by some international codes, such as the American Concrete Institute (ACI-2019), the Eurocode 2 (EC-2), and the Egyptian Code (ECP 207), were examined when applied to HSC beams with and without NS. The most important factors to consider were the effect of using NS on the shear span to effective depth (a/d) ratio and the shear strength of the beams with and without stirrups. The experimental results were validated using a nonlinear finite element analysis using the computer program ABAQUS. The experimental results showed that increasing the NS ratio reduced the number of cracks, and increased the cracks spacing, as well as reducing crack width. In specimens without stirrups, these effects were more obvious. A rise in the (a/d) ratio increased the number of cracks along the beam length, notably in the mid-span region. For specimens without stirrups and with an (a/d) of 1.5, raising NS from 0% to 1%, 2%, and 3% increased the ultimate load by 13%, 30%, and 39%, respectively, whereas for specimens with an (a/d) of 2.5, the ultimate load increased with approximately the same increase as that in beams with an (a/d) of 1.5 due to using NS. Additionally, the addition of NS to concrete boosted the contribution of the concrete to the shear strength, as shown by the results of beams without stirrups. For specimens with stirrups and an (a/d) of 1.5, raising NS from 0% to 1%, 2%, and 3% increased the ultimate load by 8%, 21%, and 30%, respectively. Additionally, for specimens with stirrups and an (a/d) of 2.5, the ultimate load increased with approximately the same increase as that in beams with stirrups and an (a/d) of 1.5 due to using NS. The test findings indicate that the shear strength calculated using the equations of the ACI 318-19 is more conservative than EC-2 and ECP 207 for NS concrete beams. The finite element program ABAQUS may be successfully used to predict the shear strength of NS concrete beams.

Sustainable Utilization of Waste Oyster Shell Powders with Different Fineness Levels in a Ternary Supplementary Cementitious Material System

As cement manufacturing accounts for 8% of global CO2 emissions, there is an urgent need to tackle the environmental impacts of cement production and address the decarbonization of construction materials. Adopting supplementary cementitious materials (SCMs), including fly ash, slag, silica fume, etc., can be used as a partial replacement for ordinary Portland cement (OPC) to reduce CO2 emissions related to the OPC industry, while providing benefits for waste valorization. This study aims to explore the sustainable utilization of a waste oyster shell powder (OSP)–lithium slag (LS)–ground granulated blast furnace slag (GGBFS) ternary SCM system in green concrete. The effect of OSP fineness on compressive strength, hydration products, pore structure, and transport properties in ternary SCM-based mortars was studied using a wide array of experimental techniques, including thermogravimetric analysis (TGA), scanning electron microscopy (SEM) analysis, Mercury intrusion porosimetry (MIP), the water absorption test and the rapid chloride penetration test (RCPT). The results revealed that the concrete with the ternary SCMs showed equivalent compressive strength compared to reference specimens. The water absorption and chloride ion charge of the RCPT in the concrete containing the ternary SCMs decreased by up to 30% and 81.4%, respectively. It was observed that the specimens incorporating the OSP with a mesh size of 3000 exhibited the highest compressive strength and the most refined microstructure.

The engineering properties and pozzolanic reaction kinetics of quaternary blended binder high strength mortars optimized by the Taguchi method

The Taguchi method has been applied for the experimental design of the mixture proportions of quaternary blended cement mortars on the basis of four factors. The design of experiment derived mixture proportions have been examined on four levels, comprising supplementary cementitious materials (SCMs) viz: ultra-fine treated palm oil fuel ash (u-TPOFA; at 4 levels of 30, 35, 40, and 45%), ground granulated blast furnace slag (GGBFS; at 4 levels of 12.5, 15, 17.5, and 20%), metakaolin (MK; at 4 levels of 7.5, 10, 12.5, and 15%) as partial replacement of ordinary Portland cement (OPC), and water to binder ratio (W/B; at 4 levels of 25, 26, 27, and 28%), in order to achieve an optimum mixture. The response factors employed were compressive strength (CS), porosity (P%), and water absorption (Abs%) at the ages of 3, 7, 14, and 28 days. By utilizing the L16 array as proposed by the Taguchi method, the specimens prepared were analyzed using 16 experiments. The results obtained showed that the response values of the optimized mixture using the Taguchi method were much better than the plain cement mortar mix and those proposed in the initial 16 series. The workability of the optimum mix increased by about 6% over the plain cement mortar mix. The relative CS results of the optimum mix was 116.92% at 28 days of curing. Likewise, the relative P% and Abs% results of the optimum mix exhibited notable reductions at 28 days of about 40.0% and 45%, respectively. Further analyses were carried out using thermogravimetric (TG) and x-ray diffraction (XRD) analyses to quantify the contribution of the SCMs and their chemical reaction which was reflected by the remaining amount of the unreacted portlandite in the mix. According to the results, the optimum quaternary blended binders mortar mix which utilized only 37.5% of cement by volume (i.e., a reduction from 882.22 to 330.83 kg/m3) portrayed improved physical properties, chemical reaction, enhanced workability, better CS, as well as lower P% and Abs% compared to the plain cement mortar.

A new approach to investigate the hydration process and the effect of algae powder on the strength properties of cement paste

ABSTRACT Sargassum muticum, a Japanese brown seaweed, has recently invaded various shorelines throughout the world, including the Atlantic coast of Morocco, where it has developed significant populations. We report on the use of these algae as a partial replacement of Portland cement in cement paste as part of a long-term plan to combat this invasive seaweed. With a fixed water to cement ratio (W/C = 0.45), algae powder is added at 5%, 10%, 15% and 20% from the cement content in producing cement pastes. The hydration process was assessed using impedance spectroscopy throughout the setting period from 10 min to 28 days. Compressive strength tests were performed at 7, 14 and 28 days. An equivalent circuit model has been proposed. The results showed that the various strength properties of the cement paste increased or decreased with addition of algae powder. The compressive strength tends to increase with the addition of algae powder. This study shows that 10% addition of algae powder to cement paste showed an increase in compressive strength and when the addition increased to 20% the properties started to decrease.

Engineering Properties of Mortar Containing Calcined Local Clay as a Supplementary Cementitious Material

The use of natural and artificial cementitious and pozzolanic materials is gaining importance and become an essential component in today's cement-based materials. Supplementary cementitious materials are recognized to provide an added value to concrete/mortar both for mechanical and durability performances as well as to their sustainability with reduced environmental impacts of the construction industry. Developing locally produced natural pozzolans is vital in the efforts towards enhancing the construction industry's sustainability. Locally extracted raw soil from Nizwa city (NZS) in Oman was ground, calcined, characterized, and used at 10%, 25%, 35%, and 50% as partial replacement of ordinary Portland cement (OPC) in mortar mix. The blend mortar was assessed with regard to compressive strength and durability properties. The obtained results indicate a slight reduction in the flow of the blended mixes. An insignificant effect of the NZS replacement on the hardened mortar's density was observed while slightly reduced strength at 1-day and 28-day for some replacement levels. Meanwhile, around a 1% reduction in the porosity and absorption. Blended cement mortar with NZS demonstrated adequate resistance to sulphuric acid and (sulphate + chloride) exposure with lower weight and strength losses compared to the control mortar.

Lime-activation of natural pozzolan for use as supplementary cementitious material in concrete

The present work was conducted to examine the beneficial effects of activating natural pozzolan (NP) using hydrated lime (HL) for its efficient utilization in concrete. Optimum dosages of NP and HL determined based on the performance of several trial mixtures to be used in concrete as a partial replacement of ordinary Portland cement (OPC). Three mixtures were finally considered for detailed evaluation of the performance of NP-HL concrete. Activation of NP by HL increased the early- and later-age strength and decreased the depth of water penetration, coefficient of chloride diffusion, depth of carbonation, strength loss due to salt weathering, and reinforcement corrosion. Although the loss of strength due to sulfate attack and shrinkage strain increased due to the inclusion of HL, these values were less than those measured in the concrete prepared using OPC alone. In summary, the results of this study indicate that natural pozzolan can be used as a supplementary cementitious material by activating it using hydrated lime.

Assessment for utilization of tobacco stem ash as a potential supplementary cementitious material in cement-based composites

Present study investigates the effectiveness of utilizing tobacco stem ash (TSA) as the partial replacement of Portland cement (PC) on the properties of cement pastes and mortars. Cement pastes and mortars were fabricated by replacing cement with TSA at four replacement levels i.e., 3.75, 7.5, 11.25, and 15 wt% relative to cement. Setting time, consistency, and hydration activity tests were performed on TSA-based cement pastes. Moreover, water absorption, porosity, compressive strength, ultrasonic pulse velocity (UPV), and electrical resistivity (ER) testing were performed on TSA-based mortars. The pozzolanic behavior of TSA was assessed via Frattini test and strength activity index. Analytical characterizations such as x-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), thermogravimetric (TG), scanning electron microscopy (SEM), and energy-dispersive x-ray (EDX) analyses were also performed. The results indicate lower water absorption and apparent porosity, leading to enhanced compressive strength, UPV, and ER values for TSA-based mortars. The analytical characterizations show that TSA promotes the hydration reaction and formation of a greater amount of cement hydrates. The strength activity index and Frattini test results showed that TSA possesses moderate pozzolanic activity at a higher replacement level. While, for low replacement levels of TSA in cement composites, the hydration reaction is governed by rapid precipitation of portlandite due to higher hydration activity.

Influence of natural zeolite on fresh properties, compressive strength, flexural strength, abrasion resistance, Cantabro-loss and microstructure of self-consolidating concrete

This study aimed to evaluate the effect of natural zeolite (NZ) on some fresh and hardened properties of self-consolidating concrete (SCC). For this purpose, eight mixtures containing 0, 5%, 10%, and 15% NZ as partial replacement of portland cement with two water to binder ratios (w/b) were studied. In order to evaluate the mechanical properties of concrete, compressive strength and four-point bending tests were performed at the ages of 7, 28, and 90 days. The abrasion resistance and Cantabro-loss tests were performed according to ASTM C779-A (procedure A-revolving discs) and ASTM C1747, respectively at the ages of 28 and 90 days. The results indicated that the HRWR demand of SCC mixtures increases with NZ content. However, the viscosity and stability of the mixtures were improved by NZ. Overall, the mechanical properties of SCC mixtures were improved by using NZ. The optimum rate of NZ was found to be 10%. Although the reduction of the w/b ratio had a more significant effect on improving the mechanical properties compared to using NZ, the reduction of the w/b ratio along with the partial replacement of cement with NZ enhanced this effect. In addition, regression analysis showed a strong correlation between the results of abrasion resistance and Cantabro-loss tests. The results of SEM analysis showed a significant reduction in the width, length and number of micro-cracks in the bulk binder paste and the ITZ of 10% NZ mixtures compared to the plain portland cement mixtures. High peak intensities of C-S-H gel and low intensities of ettringite were also observed by XRD analysis in the ITZ of NZ- containing concretes due to pozzolanic reaction.

Hydration Behaviour and Characteristics of Binary Blended Metakaolin Cement Pastes

Cement production consume large amount of energy to form clinker and carbon dioxide (CO2) emitted into the atmosphere causing global warming. To mitigate this challenge, the use of Metakaolin (MK) as supplementary cementitious material cannot be over emphasized. This study evaluated the use of Metakaolin (MK) on hydration development of MK--PC blended cements and strength of Mortars. The MK with a Blaine fineness of 7883 cm2/g was used to replace Portland Cement (PC) at a level of 0, 5, 10, 15, 20, 25 and 30 % by mass of PC at a constant w/b ratio of 0.50 to prepare blended cements. Hydration development of blended cement and compressive strength of Mortars were investigated using chemically bond water and free-lime contents and strength tests respectively. X – Ray diffraction (XRD) and scanning electron Microscopy (SEM) techniques were also utilised in the analysis of Pozzolanic reaction and hydration products. Test results indicates that Water of consistency, setting times for the mixes increased with increase in MK contents, influence of MK on the chemically bond water and free Lime contents of the blended cements were due to its filler and dilution effects and Pozzolanic reaction. The cumulative non-evaporable water and free-lime contents increased by partial replacement of PC with MK due to PC hydration and Pozzolanic reaction. The tested Mortar prepared with blended cements with 30 % PC replacement with MK shows a retardation of strength development with a low value at early ages (7 days) and increased in growth at later ages (28 days). The compressive strength of tested mortar for 90 days curing age for the blended mortar is 31 N/mm2 close to that of control Mortar (35 N/mm2). The results obtained from XRD and SEM analysis indicated increase in Calcium Hydroxide (CH) consumption and Calcium Silicate hydrate (C-S-H) formation in blended cement pastes with curing time. The PC replacement with MK induced changes in Microstructures of blended cement paste and chemical composition of hydration products. These results are potentials for modelling the behaviour of MK-PC blended cements.

Properties of Concrete with Recycled Aggregates Giving a Second Life to Municipal Solid Waste Incineration Bottom Ash Concrete

Economic and environmental factors call for increased resource productivity. Partial or full replacement of Portland cement by wastes and by-products, and natural aggregates by construction and demolition wastes, are two prominent routes of achieving circular economy in construction and related industries. Municipal solid waste incineration (MSWI) bottom ashes have been found to be suitable to be used as a supplementary cementitious material (SCM) after various treatments. This paper reports a brief literature review on optimum use of recycled aggregates in concrete and an experimental study using replacement of natural aggregate by demolished concrete having MSWI bottom ash as partial replacement of Portland cement, and compares its properties to that of completely natural aggregate concrete. Additional water was added as a compensation for the water absorption by the recycled aggregate during the first 30 min of water contact during concrete mixing. Also the fine fraction of crushed concrete (<250 µm) was removed to reduce the ill-effects of using recycled aggregate. The replacement of aggregates was limited to 23% by weight of natural aggregate. The results prove environmentally safe and comparable performance of concrete including recycled aggregate with bottom ash to that of natural aggregate concrete.

The impact of using rice husk ash as a replacement material in concrete: An experimental study

Rice husk ash (RHA) is a promising pozzolanic alternative material for partial replacement of ordinary Portland cement to increase the durability and strength of concrete and, at the same time, to decrease the corrosion effect caused by the harsh environment conditions. In this study, the impact of adding RHA in different ratios (0%, 7%, and 14%) as a replacement of ordinary Portland cement with different water–cement ratios (0.3, 0.5, and 0.7) and cured in water for different periods (10, 20, and 30 days) both on the durability and strength of the concrete and on its corrosion was investigated. The prepared specimens were tested by flexural, compressive, and tensile strength tests, slump test, and Rapid Chloride Ion Penetration test to determine the suitability of the partial replacement of ordinary Portland cement by RHA in concrete. The most important findings of this work, which is considered novel in this field, are that adding fine (instead of more extensive) RHA particles enhances the flexural, compressive, and tensile strength values and limits the chloride ion penetration with time. An adverse impact was found to increase the water–cement ratio, which is assigned to the effect of water on RHA and as a result on the porosity of the concrete.

Sustainable reuse of ceramic waste powder as a supplementary cementitious material in recycled aggregate concrete: Mechanical properties, durability and microstructure assessment

Waste concrete as one of construction and demolition wastes is generally collected for the production of recycled coarse aggregate (RCA) to alleviate environmental issues. However, the poor physical performances of RCA limit its application in concrete. Thanks to the rich silica-alumina contents and large reserves in China, the ceramic waste powder (CWP) is promising to be used as an effective supplementary cementitious material (SCM) in cement-based materials. This study reports the development of recycled aggregate concrete (RAC) using CWP as a partial replacement of Portland cement. The mechanical properties, sorptivity, rapid chloride ion penetrability, microstructure, ecological evaluations of RAC containing CWP are determined. The experimental results demonstrate that the eco-friendly RAC incorporated CWP has sufficiently high strength and its compressive strength at 56d is 36.01 MPa. In terms of penetrability behaviors, the rapid chloride penetrability and sorptivity of RAC decrease when the 60% RCA and the 10% CWP are utilized simultaneously. Furthermore, the incorporation of CWP significantly reduces the cost, thermal energy consumption and carbon dioxide emission of concrete. Based on the findings, the applications of CWP in generating a durable eco-friendly construction product are appealing as it not only provides an alternative approach to reuse the wastes, but also achieves superior performance.

Effect of the incorporation of PET fiber and ternary blended binder on the flexural and tensile behaviour of ultra-high performance green concrete

Ultra-High performance Fiber Reinforced Green Concrete is an advanced technology in concrete sustainability via the utilization of green alternative materials, with superior mechanical properties. The effects of adding recycled waste plastic bottles in the form Polyethylene Terephthalate (PET) fiber on the flexural and tensile behavior of Ultra-High Performance PET Fibre Reinforced Green Concrete (UHPPFRGC) containing different volumes of Ultra-fine palm oil fuel ash (UPOFA) and Silica Fume (SF) have been investigated. Up to fourteen concrete mixtures were designed with varying UPOFA and SF content as partial replacement of ordinary Portland cement (OPC) in volumes of (25%- 50%) UPOFA and (10%-20%) SF. PET fibres were added at a portion of 1% from the total mixture volume. The results showed that the addition of PET fibres modulates the stiff and brittle behaviour of Ultra High-Performance Green Concrete (UHPGC). The optimum values were registered with (U25-SF20-UHPPFRGC) mix containing 25%UPOFA, 20%SF and 1% PET fibres. A considerable increased in ductility index was achieved, with superior compressive strength, splitting tensile strength, flexural strength, flexural toughness and flexural stiffness of 153 MPa, 9.31 MPa, 30.1 MPa, 29.7 kN.mm and 18.225kN/mm, respectively. Thus, the utilization of ternary blended binders (OPC-UPOFA-SF) with recycled PET fibres could promote the production of UHPPFRGC possessing adequate flexural and tensile strength properties.

Assessment of local sewage sludge ash as a supplementary cementitious material - effects of incineration temperature and cooling rate of the ash

This paper reports on the possible use of sewage sludge ash as a pozzolanic supplementary cementitious material to Portland cement. Samples of sewage sludge were incinerated at 700°C, 800°C and 900°C and these were then cooled in the furnace (FISSA), in air (AISSA) or by quenching in water. The resulting ashes were ground to suitable fineness and used to prepare cement pastes and mortars in which the binder consisted of 30% ash and 70% Portland cement. The paste samples were used for microscopic and chemical assessment of the evolution of hydration products, while the mortars were used to assess the effects of the ashes on workability and compressive strength of laboratory-prepared samples using a water/binder ratio of 0.5. Fly ash was used as a reference pozzolanic material to assess the performance of sewage sludge ashes. Analysis of the sewage sludge ashes showed the presence of cementitious compounds and hydration products that suggest that this material can be used as a partial replacement of Portland cement. However, sewage sludge ash reduces the workability of the mortar. Compressive strength results indicate that the highest strength is obtained when the sewage sludge is incinerated at 900°C and then quenched in water.

Development of an environmental-friendly durable self-compacting concrete.

In this experimental study on self-compacting concrete (SCC), the Manufactured sand (M-sand) and Fly ash (FA) were utilised for partial replacement of Natural sand (N-sand) and Ordinary Portland Cement (OPC), respectively. N-sand was partially replaced by M-sand at various percentage levels, after the dose of FA in the mix was optimised. In terms of compressive strength, the optimum replacement level of OPC by FA was 20%, whilst for replacement of N-sand by M-sand it was 50%. Two types of mixes were prepared to compare the macro and micro level properties of SCC, i.e., SCC-I (100%OPC + 100%N-sand) and SCC-II (80%OPC + 20%FA + 50%N-sand + 50%M-sand). The characteristics of fresh concrete mixes were determined using Slump flow, T50 time, V-funnel, L-box, U-box, and J-ring tests. After 28days of curing in tap water, both types of specimens were exposed to a solution of ammonium sulphate [(NH4)2SO4] containing sulphate salt concentration of 2.0g/l for 360days to test their durability. Loss in compressive strength, weight change, sorptivity, and micro-structural changes (XRD, SEM, and EDS) all were evaluated for up to 360days. It was found that the use of FA and M-sand in concrete makes it more environmental-friendly and durable, as well as have better performance in a sulphate environment.

Assessment of pozzolanic material for manufacturing of Portland Pozzolana cement (PPC) by the comparison of Ordinary Portland cement (OPC)

In the present study physicochemical characterization of slate sample was carried out which was collected from slate mine in Lasbela District, Baluchistan. Slate was evaluated for its effectiveness as partial replacement of ordinary Portland cement (OPC) in the production of Portland Pozzolana cement (PPC). The grain size analysis of crushed slate sample using ball mill revealed that maximum fraction retained on 44 μm was about 72.8 %. Sum of the major oxides (SiO2 + Al2O3 + Fe2O3) is about 90.09 % that meet the requirement as per ASTM C 618 (minimum 70.0 %). Other oxides including SO3 (<0.05), CaO (4.04), MgO (1.66), K2O (0.10), Na2O (0.16), TiO2 (0.35), MnO (<0.02) and Cl (0.12) also meet the international standard of ASTM C 618 for PPC. OPC without and with using slate sample in a ratio of 5 % and 10 % with clinker was tested to measure compressive strength, physical tests and setting time. The results showed that after 5 % and 10 % replacement, insignificant effect was observed on the physical properties, setting time and compressive strength in 2-, 7- and 28-days curing. Hence, slate can be used as natural pozzolan for manufacturing PPC. It is cost effective for the production of cement as well as to sustain the resources of limestone for long time and reducing emission of CO2 in the environment. It can also be used in the sulfate rich environment, coastal areas especially for the construction of dams and bridges.

Assessment of properties of mortars modified with sugarcane bagasse ash processed by heating at different temperatures as cement replacement

Recently, sugarcane bagasse ash (SBA), generated in boilers after combustion of sugarcane bagasse for cogeneration has been basically accepted as a pozzolanic material. In this study, SBA, which was first sieved through the No. 100 sieve (SBA-s) before burning at 600 °C, 700 °C, 800 °C for 1 h as post-treatment (denoted as SBA-600, SBA-700, SBA-800) was sequentially used as a partial replacement for Portland cement (i.e. 5%, 10%, 15%, 20% by weight) in casting blended mortars. Performance in fresh and hardened states of these mixes were examined and compared to that of the cement mortar (cement: sand of 1:2.75 and water-to-cement ratio of 0.57). The results indicate that the SBA-systems required more mixing water than Portland cement; whereas, blended pastes with a part of re-burnt ash manifested an acceleration of setting time compared to that with SBA-s. In addition, mortars prepared with SBA-700 or SBA-800 at replacement rates of 5% and 10% for cement showed the lowest porosity, the best both of mechanical strength and durability (in terms of sulphate resistance, surface resistivity). SEM analysis verifies that a dense phase was observed for the matrix of blended mortars contained 5–10% SBA-700 or SBA-800.

Blended Basic Oxygen Furnace (BOF) Slag with Ground Granulated Blast Furnace Slag (GGBFS) as a Pozzolanic Material

As one of the by-products in the steel industry, granulated blast furnace slag (GBFS) is widely used as an aggregate or a pozzolanic material (a partial replacement for Portland cement) in the concrete mixture after the crushing or grinding process. However, using a basic oxygen furnace slag (BOFS) as a cementitious material is limited because of its inherent shortcomings such as low cementing property and undesirable expansion characteristics due to free lime. To overcome BOFS’s these properties, the BOFS was ground, blended with the ground granulated blast furnace slag (GGBFS), and used as a pozzolanic material in this research. A total of five mortar mixtures were developed, including ordinary Portland cement (OPC) as a control group, two binary mixtures, and two ternary blended mixtures with 50% cement replacements by GGBFS and BOFS by weight percentages. Properties of these mixtures were evaluated according to ASTM C 989 and C 311 standard specifications that include compressive strength, alkali-silica reaction (ASR), and sulfate resistance tests. Moreover, basic material characterization of GGBFS and BOFSs was investigated by X-ray diffraction (XRD), chemical composition analysis (XRF), and particle size distribution (PSD). The test result shows that the blended mixture with 15% BOFS and 35% GGBFS satisfied the strength activity index and good ASR and sulfate resistance.