Portland Cement In Mortars Research Articles

Compressive strength and regional supply implications of rice straw and rice hull ashes used as supplementary cementitious materials

Substituting Portland cement (PC) with supplementary cementitious materials (SCMs) is a key strategy for reducing greenhouse gas (GHG) emissions. Considering alternative SCMs requires a holistic understanding of changes to material performance, emissions reduction potential, and regional availability. Four rice hull ashes (RHAs) and one rice straw ash (RSA) were evaluated to replace PC in mortars (10% untreated ash and 30% blast furnace slag; 15% untreated ash; or 15% milled ash). The 28-day compressive strengths with 0.59 water-to-binder ratio for fly-RHAs (38.0–49.8 MPa) and RSA (37.7 - 44.1 MPa) did not vary significantly from the PC control (43.2 MPa) based on an ANOVA. Modeling rice biomass generation in six U.S. states shows RSA could triple the supply of rice-biomass ash, but in states with substantial PC demand, i.e., California and Texas, the potential GHG reduction may remain small (∼1–2%). RSA and RHA may hold promise in lowering concrete GHG emissions.

Improving mortar properties using traditional ceramic materials ground to precisely controlled sizes

The present work investigates the impact of particle size reduction of traditional ceramic materials as partial substitutes for Portland cement in mortars. Ceramic brick, ceramic tile, and stoneware were selected, with three particle sizes (D50 of 1, 5, and 15 μm) achieved through grinding operations adapted to each material grindability. The reactivity of ceramic powders was assessed via dissolution in saturated lime solution. Mortars were prepared with 10 % and 20 % cement mass replaced by ceramic powders ground to each fineness. The packing density of mortars was evaluated using the Compressible Packing Model. Compressive strength was measured at 1, 3, 7, and 28 days, and pore size distribution was analyzed by mercury intrusion porosimetry. Results indicated that ceramic tile required less grinding energy than brick and stoneware. High-energy grinding slightly altered the crystalline structure and increased amorphous content, enhancing reactivity with lime. Increased cement replacement with finer ceramic powders (D50 about 1 μm) improved strength, increased mesopores (50 nm), and reduced pore size threshold, attributed to filler and pozzolanic effects. A multiple linear regression model effectively described the influence of various variables on mortar strength with the interaction terms demonstrating the complexity of the interplay of the variables.

Utilization of Waste Brick Powder as a Partial Replacement of Portland Cement in Mortars

Partially substituting Portland cement (PC) with waste brick powder (WBP) is an effective method to reduce environmental pollution. In this paper, the effects of a WBP with low pozzolanic activity on the fresh and hardened properties of blended cement with 0–40% WBP or 50% of WBP+GGBFS (by mass) were studied. Sodium sulphate (SS) (1.5 and 2.5%, related to powder mass) was used to activate the blended cement with 40% WBP or 50% WBP+GGBFS at 20 °C. Results show that the performance of blended cement is decreased with the increase in WBP content since the WBP with low pozzolanic activity mainly contributes to the dilution effect. Binary cement with 10% WBP shows a similar carbonation depth and chloride migration coefficient to PC. Ternary cement with 10% WBP and 40% GGBFS exhibits a slightly lower strength at 90 days and a lower chloride migration coefficient than PC. The SS solution increases the compressive strength at 2 days and decreases the compressive strength at 28 and 90 days. Moreover, the SS solution results in a lower carbonation depth and chloride migration coefficient, except for ternary cement with 10% WBP and 40% GGBFS, which shows a higher carbonation depth at 42 and 68 days. This paper provides a reference for the application of WBP to produce green mortars.

Feasibility Study of Using Steel Slag to Replace Portland Cement in Mortars

Feasibility Study of Using Steel Slag to Replace Portland Cement in Mortars

Residual fly ash from pyrometallurgical processes as a partial replacement for Portland cement in mortars: a study of structural evolution and determination of compressive strength

Abstract Mortar mixtures were prepared by partial replacement of Portland cement with 0%, 10%, and 15% of residual fly ash to determine the structural evolution and compressive strength at 3, 7, 14, and 28 days. Portlandite, calcite, ettringite, iron oxide, silicon oxide, and sillimanite were identified in the standard mortar, and, additionally, magnetite was identified in the mortar with 10% and 15% fly ash. X-ray diffraction peaks corresponding to portlandite and ettringite increased in intensity with increasing curing time as a result of the consolidation of mineral species. The SEM analysis revealed that the standard mortar contained mainly portlandite and ettringite at 28 days, while the samples with 10% and 15% fly ash contained particles of fly ash coated with portlandite and ettringite, particles with a smooth surface, and particles of fly ash with signs of attack on their surfaces. The sc increased when the age of the mortar and the substitution of Portland cement by fly ash was increased from 3 to 28 days and from 0 to 15%, respectively.

Effects of incorporating silica glass powder as a supplementary cementitious material on selected properties of portland cement mortar

The use of waste glass powder as a partial replacement for cement is an emerging practice for sustainable cement-based construction. Several studies have demonstrated that finely ground-powdered glass could be an interesting supplementary cementitious material (SCM). However, the performance of such material is influenced by the chemical composition of glass and its pozzolanic reactivity. In this context, the goal of this study is to investigate the use of silica-glass powder (SGP), which is characterized by a high content of silica (>96%), as a partial replacement of Portland cement in mortar. In this research work, mortars containing 7.5%, 10, 12.5, 15 and 20% SGP in replacement of an amount of cement, with three different water-to-binder ratios of 0.55, 0.60 and 0.65 are studied. Selected properties have been investigated at both fresh and hardened stages, which include workability, air content, flexural and compressive strengths estimated by destructive and non-destructive methods, water absorption by capillarity, permeability to chlorides and chloride ions diffusion. The experimental results confirm that incorporating SGP improves the mechanical strength of the mortar, notably in the long-term, and can considerably enhance its durability properties, especially by a decrease in sorptivity of the mortar and by an increase of its resistance to chloride ions diffusion. Correlations between selected physical and mechanical properties and certain durability indices are also established and discussed in this study.

Composition of renders and plasters of award-winning buildings in Lisbon (Portugal): A contribution to the knowledge of binders used in the 20th Century

ABSTRACT This paper reports on the study of renders and plasters from 20th-century award-winning buildings in Lisbon (Portugal) with the Valmor Prize for Architecture. The mortars have been investigated through XRD, optical and electronic microscopy (SEM-EDS), thermal analysis (TGA/DTA), wet chemical analyses and AAS. The results reveal that the use of air lime lasted until the 1940s. It also highlights the beginning of using of Portland cement in mortars in the 1930s, mixed with air-lime, and the abandonment of mortar formulations solely based on air lime. This study highlights the use of finishing lime-gypsum-based mortars until the 1940s and different types of Portland cement from the 1940s onwards. Portland cement was the main binder for the analysed stone-imitating mortars from 1940s to 1970s. Finally, salt contamination was occasionally found in mortars, which generally reveal a good state of conservation.

Study of alternative materials for Portland cement replacement in civil construction

The proposal of this work is to study materials, which initially were classified as disposable, in building construction as new alternative materials. In this way, this research studied the partial replacement of Portland cement in mortars by the following pozzolans: sugar cane bagasse ash (SCBA), rice husk ash (RHA), metakaolin (MK) and silica fume (SA). Theses composites were compared with a control mixture, which no Portland cement replacement, in the following tests: compressive strength, consistency, water capillarity and water immersion.   The replacements percentages carried out were 5, 10, 15, 20, 25 and 30% for SCBA, RHA and metakaolin, and 5, 10 and 15% for silica fume by weight. The compressive strength test was performed at curing times of 3, 7, 28 and 90 days, whereas water capillarity and water immersion were carried out at 28 days. In the early ages, few mixtures showed resistance above the reference, but with 90 days, six mixtures passed the control. All mixtures with pozzolans presented less water absorption by immersion and capillarity. Sustainably, the use of SCBA, RHA, MK and SA is viable.

Hybrid geopolymer-cement coating mortar optimized based on metakaolin, fly ash, and granulated blast furnace slag

The use of wastes for new binders aims to reduce the environmental impact caused by the manufacture of Portland cement (PC) given the advance of urbanization. In this work, the main effects of the use of Geopolymer Cement (GC) in partial replacement to PC in mortars for coating were investigated. The GC was obtained from mixtures of industrial wastes, fly ash (FA), granulated blast furnace slag (GBFS), and metakaolin (MK), activated by a solution composed of alkaline sodium silicate (SS) and potassium hydroxide (KOH). The factors used for the experimental planning were the cement replacement content, T (10, 30, and 50%, by weight) and the aggregate-cement ratio, A/C (6.11, 6.90, and 7.69, by weight). Some properties were evaluated initially: consistency, compressive strength, durability (sulfate attack) and microstructural analysis (SEM, XRD, DSC, and TG). For optimized mixture and reference were tested: consistency, setting time, the heat of hydration, water retention, compressive strength, flexural tensile strength, tensile bond strength, dimensional variation, water absorption, voids content, elastic modulus, and thermal conductivity. The results are promising for the use of GC in mortars. The optimized mortar reached values of compressive strength and flexural tensile strength of 5.65 MPa and 1.73 MPa, respectively. The results showed the feasibility of using as eco-friendly mortar for internal and external coating, or as a mortar to repair degraded coatings. Hybrid mortars did not show good performance for attack by sulfates.

Strength and Corrosion Studies of Mortars Added with Pozzolan in Sulphate Ions Environment

The pozzolanic materials have the capacity to modify the performance of Portland cement (PC) mortars. When they are used as supplementary materials, the physical-chemical properties such as compressive-strength and resistance to aggressive environments (chloride, sulphate, acids) are improved. In this article, a study was carried out to evaluate the effects of the addition of two natural pozzolans: volcanic pumice and zeolite. Both used as substitutes for PC in mortars based on cement, considering mechanical strength and the aggressive effect of sulphate ions. Furthermore, the electrochemical behavior of the steel rebar embedded in these mortars was studied during 730 days of exposition to aggressive conditions. The results revealed that the development of the compressive strength of mortars with pozzolans added reached similar values to the reference mortar. It was possible to observe that the addition of the pozzolan suppresses the ettringite formation proportionally to the pozzolan content. The corrosion resistance of the steel improves with the addition of pozzolans after 730 days of exposition at sulphate environment. The results of this study revealed the feasibility to use natural pozzolan as an additive during the preparation of cement up to 25% without significant changes of the physical-chemical properties of the mortars.

Evaluation of mortar properties obtained through partial substitution of Portland cement by ashes of oil palm empty fruit bunch

Abstract Currently, palm oil is a leader in production and consumption among commercial edible oils, with a growing world production that exceeds 66 million tons per year. It is estimated that the generation of residues from the burning of palm oil empty fruit bunches as fuel in the boilers corresponds to 5% in mass of the total of oil extracted. This work evaluated the mechanical properties resulting from the use of the empty fruit bunch ashes as a partial substitute of Portland cement in mortars in different contents in 1:3 and 1:6 mixes. Mortars obtained with the use of ash presented greater deformability, implying greater workability. The results obtained pointed to potential use of the ash as filler in mortars without loss on compressive strength for contents up to 10% in the 1:3 mix and 5% in the 1:6 mix. It was observed an increase in the void index and the water absorption capacity, with a proportional reduction of the flexural strength.

Synthesis and Properties of Red Mud-Based Nanoferrite Clinker

Red mud, an industrial waste obtained from alumina plants, is usually discharged into marine or disposed into a landfill polluting the surrounding water, atmosphere, and soil. Thus, disposal of red mud is an environmental concern and it should be recycled in an effective way. Since red mud consists of iron- and aluminum-rich phases, it can potentially be processed into cementitious material and can be used for a construction purpose. This research investigated the synthesis of nanoferrite (NF) clinker by using red mud as a raw material through chemical combustion technology for potential use in cement-based composite. Before the synthesis of NF, red mud was characterized by using XRF, XRD, and SEM techniques. From characterization results, the stoichiometric ratio of raw materials was calculated and experimentally optimized. The sample was then tested at various temperatures (815, 900, 1000, and 1100°C) to find the optimum synthesis temperature. Finally, the hydraulic activity of NF was verified and the contribution to mechanical properties was determined by replacing cement with NF at various substitution levels (0, 5, 10, and 20 wt%). Test results showed that the optimum condition for the synthesis of NF was found when the ratio of CaCO3/red mud was 1.5 and the sintering temperature was 815°C. The synthesized NF had an average diameter of 300 nm, and the main composition was brownmillerite (C4AF) with distinct hydraulic reaction. When NF was used as a substitute of Portland cement in mortar, the flexural strength with a 5% replacement level improved by 15%. Therefore, it can be concluded that the synthesis of NF provides an alternative approach to recycle red mud and could significantly help in reducing environmental pollution.

Sericitic Phyllite as Addition in Portland Cement

Pozzolans are materials that when milled are able to react with the cement, forming compounds with binder properties. Seeking to reduce costs and improve Portland cement performance, the cement industry has used mineral additions such as pozzolans, partially replacing clinker in Portland cement. Sericitic Phyllite is a metamorphic rock, considered sterile by iron mining. It is extracted from the pit to enable the extraction of iron ore and is disposed in sterile piles, representing an environmental liability. The present work evaluated the possibility of the Sericitic Phyllite acquires pozzolanic properties from thermal treatment, to be used as mineral addition in the partial substitution of Portland cement in mortars. The material was processed by milling in its natural moisture of 8% using a high performance planetary mill, and calcination in an electric resistance furnace at different temperatures (350, 550 and 850oC) for thirty minutes each. It was characterized by laser granulometry, X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal and thermogravimetric analysis (DTA/TGA). After characterization, specimens were prepared with 25% substitution by weight of the Portland cement by the Sericitic Phyllite. The calcined material in 350, 550 and 850oC reached, respectively, 70%, 76% and 82% of the resistance of the control mortar. The results indicate the feasibility of using the Sericitic Phyllite as mineral addition in Portland cements as the mortars with the calcined material in all temperatures reached 32MPa.

The utilisation of feed and byproducts of mineral carbonation processes as pozzolanic cement replacements

Abstract Utilising the byproducts of mineral carbonation processes contributes to rendering the technology environmentally benign and enhances the economically viability of the process. In this work we synthesised, characterised and investigated the technical feasibility and environmental benefits of utilising feed and byproducts of mineral carbonation technology as Portland cement substitutes. These materials, with and without pre-treatment, were used to substitute 5, 10 and 20 wt% of Portland cement in mortars. Pozzolanic activity tests indicated that acid treated silica enriched residue (ATSER) displayed pozzolanic activity. At 5% cement replacement all materials showed compressive strengths comparable to the control. When 10 wt% of cement was replaced, only heat activated lizardite showed strength results similar to the control. The compressive strength of mortars containing other samples with 10 wt% or greater cement replacement showed that the extra water demand outweighed any pozzolanic contribution of mineral carbonation materials and resulted in a lowering of the compressive strength of these mortars compared to controls, in particular when in excess of 10 wt% of cement is replaced. An environmental analysis showed that in addition to significant CO2 emissions reduction, the economic and environmental costs of waste disposal were avoided when mineral carbonation byproducts substituted Portland cement.

Evaluation of compatibility of neutron-shielding boron aggregates with Portland cement in mortar

Enhanced neutron radiation shielding capacity of protective structures can be achieved using cement-based composites with boron-containing aggregates. Experimental tests were performed to evaluate the effect of boron aggregates (colemanite, ulexite, borax, boron carbide) and nanosilica on the setting time and hydration heat of cement in mortars using isothermal calorimetry. Boron leaching test from mineral aggregates were performed in water and saturated Ca(OH)2 solution. Cement setting retardation effects were found qualitatively correlated with boron leaching from mineral aggregates. A linear dependence of compressive strength of borated mortars and heat released after 72 h of cement hydration was found. A maximum content of boron compounds in mortar, allowing for a systematical control of setting time, was evaluated.

Effect of Calcination Temperature on the Pozzolanic Activity of Brazilian Sugar Cane Bagasse Ash (SCBA)

This study evaluated the feasibility of using sugar cane bagasse ash (SCBA), a by-product of the sugar cane ethanol industry, obtained under controlled calcination as a partial replacement for Portland cement in mortars. Materials with pozzolanic characteristics may be used to partially replace cement in mortars or concrete and are known to provide durability to the products. Initially, TG/DTA curves of the sugar cane bagasse were conducted to define suitable calcination temperatures (500oC, 600oC and 700oC), and tests were conducted to characterize the physical-chemical parameters of the SCBA and the pozzolanic activity according to NP EN 196-5. The results showed the technical feasibility of using the SCBA as a pozzolanic material in construction, which would provide an alternative to proper disposal for this waste while providing products with high technical performance.

Use of asbestos-free fiber-cement waste as a partial substitute of Portland cement in mortar

This work aims to study the possibility to use asbestos-free fiber-cement waste in substitution of ordinary Portland cement for the production of mortars. The fiber-cement particles were incorporated in mortars in partial replacement of cement, with mass substitution rates of 5 and 20 %. Cement hydration rate, workability, total shrinkage, porosity accessible to water and mechanical performances of mortars made with ground fiber-cement were measured and compared with the properties of control paste and mortar (free of fiber-cement). The results showed that the presence of fiber-cement extended by 5–10 % the dormant period of the binder hydration, when compared to that of Portland cement, depending on the substitution rate considered. Furthermore, at 28 days, the replacement of cement with 5 and 20 % of fiber-cement caused a reduction of 14–35 % in compressive strength, when compared to the reference mortar performances. This decrease was greater than that observed on mortars containing limestone filler with the same substitution rate of cement. However, the strengths obtained were acceptable for structural applications.

Rock wool wastes as a supplementary cementitious material replacement in cement-based composites

The use of rock wool waste, an industrial by-product, in cement-based composites has positive effects on the environment because it reduces the problems associated rock wool disposal. The experiments in this study tested cement-based composites using various rock wool waste contents (10, 20, 30 and 40% by weight of cement) as a partial replacement for Portland cement in mortars. The pozzolanic strength activity test, flow test, compressive strength test, dry shrinkage test, absorption test, initial surface absorption test and scanning electron microscope observations were conducted to evaluate the properties of cement-based composites. Test results demonstrate that the pozzolanic strength activity index for rock wool waste specimens is 103% after 91 days. The inclusion of rock wool waste in cement-based composites decreases its dry shrinkage and initial surface absorption, and increases its compressive strength. These improved properties are the result of the dense structure achieved by the filling effect and pozzolanic reactions of the rock wool waste. The addition of 30% and 10% rock wool wastes to cement is the optimal amount based on the results of compressive strength and initial surface absorption for a w/cm of 0.35 and 0.55, respectively. Therefore, it is feasible to utilize rock wool waste as a partial replacement of cement in cement-based composites.

Metakaolinite/TiO2 composite: Photoactive admixture for building materials based on Portland cement binder

Novel latent hydraulic and photoactive admixture metakaolinite/TiO2 was prepared, characterized and evaluated as a partial replacement for the Portland cement in mortars. The main component of this novel composite material is metakaolinite containing the anatase nanoparticles anchored on its surface. The values of the compression strength measured for the mortars containing metakaolinite/TiO2 composites reached higher values in comparison to the mortar without this admixture. Photodegradation activity of the mortars with given amount of the metakaolinite/TiO2 admixture against nitric oxide (NO) was tested using the modified ISO standard. The results showed that the conversion of NO increases with the increasing content of TiO2. The synergistic effect of the photodegradation activity and the latent hydraulicity in this material can be utilized in building industry to decrease concentration of selected air pollutants e.g. in areas affected by traffic pollution.

Sustainable Manufacturing Technology and Properties of Steel Slag Concrete

Early-age deterioration of concrete due to cracking and higher maintenance cost for poor durability cause serious troubles to concrete structures. Steel slag is a solid waste discharged in large quantities by the iron and steel industry. Steel slag includes a certain scale mineral such as C2S and C3S, and can be applied in cement and concrete as mineral admixtures. When mineral admixtures with steel slag powder and blast-furnace slag powder are mixed into concrete, the performance of concrete can be improved further. Mineral admixtures with steel slag powder as partial replacement for Portland cement in mortar is an effective means for enhancing abrasion resistance. Steel slag powder can be used to reduce cracking in concrete at early age, so that it will improve the durability of concrete structures.