Substitution Of Ordinary Portland Cement Research Articles

Calcined Marl and Condensed Silica Fume as Partial Replacement for Ordinary Portland Cement

The main objective of this investigation is to replace calcined marl (0, 10, 20%) and condensed silica fume (SF, 0, 7, 10%) partially for ordinary Portland cement (OPC). Marl, a calcium-based supplementary cementitious material (SCM) calcines at a considerably lower temperature (750 °C) than OPC (up to 1480 °C). The calcined marl contributes in prolonged pozzolanic reactions and represents characteristics of latent cement chemistry. To approach the major conclusions, 27 mixes were designed based on the three ratios of water to the total binders (W/B) of 0.38, 0.42 and 0.45. The calcined marl and SF proportioned in mixes with “0, 10 and 20%” and “0, 7 and 10%”, respectively. After the ages of 7, 28 and 90 days all mixes improved, mechanically. In particular, the hardened concretes containing 10 and 20% of calcined marl show stronger reaction for substitution of OPC. In the lower limit of W/B ratio (0.38) mixes with 20% calcined marl exhibit a remarkable increase of some 2.4-fold strengths from 7 to 90 days. Also, the results obtained by tensile strength and modulus of rupture for concrete mixes containing 10 and 20% calcined marl highlight the mechanical progress of hardened concrete after 28 days. Collectively, both SCMs replaced OPC in a considerable amount (up to 30%). However, long-term enhancement in mechanical strength and durability indices are typically supported by calcined marl.

A comprehensive investigation into the effect of temperature variation on the mechanical properties of sustainable concrete

Minimizing the production energy and resources consumption are the key principle for engineering sustainability. In the case of concrete structures, this concept can be achieved by the use of materials in the most efficient way considering in the mix design the optimal mechanical and durability properties. The substitution of ordinary Portland cement for other supplementary cementitious materials is assessing the possibility of enhancing the sustainability and decreasing the environmental impact of concrete. Mass concrete is rich in cementitious materials which results in high temperature within the concrete, hence several hazards such as cracking or temperature differences between the interior and the surface of concrete could be prevented. An experimental study evaluated on several one cubic meter sized concrete elements in which during the primary phase of hydration, the temperature variation is recorded in several location offsets with respect to time. Thermal variations results are analyzed in accordance with the cement type, CO 2 emission production of cement, compressive strength, water tightness, drying shrinkage and rapid chloride migration coefficient. The results indicate that slag cement CEM III/B 32.5, that incorporates highest amount of slag, ensured improved mechanical, thermal and durability properties in comparison with ordinary Portland cement CEM I 32.5.

Study on the addition effect of metakaolin and mechanically activated kaolin on cement strength and microstructure under different curing conditions

The effects of thermally (MK) or mechanically activated kaolin (AK) on the compressive strength of mortars and microstructure of pastes were investigated. Mortar mixtures, in which 10%, 20% and 30% of ordinary Portland cement (OPC) was replaced by either MK or AK, were prepared (w/b of 0.5) and ordinary (age 2, 28 or 90days) and autoclave cured. Hydration products were determined by X-ray diffraction (XRD) and differential thermal analysis/thermal gravimetry (DTA/TG) analysis, while microstructure was investigated by mercury intrusion porosimetry (MIP).MK substitution increases the compressive strength of ordinary-cured mortars, as a result of the higher content of reactive silica that caused more pronounced pozzolanic reaction, as well as by effective refinement of their pore structure. Positive effects on the compressive strength could be achieved up to 30% substitution of OPC by MK. The OPC substitution by AK resulted in lower strengths of ordinary-cured mortars, compared to both MK mortars and reference. Higher specific surface area and finer particles of AK were insufficient to compensate, through filler effect, lower pozzolanic reaction and additional negative influence of the kaolinite presence. The highest compressive strength was obtained for mortar with 10% of AK (relative strength of 94%).In comparison to the reference, autoclaved MK and AK mortars, exhibited lower compressive strength, as a consequence of increasing the hydrogarnet formation, instead of tobermorite. The highest strength was achieved for mortar with 10% of AK.

Utilization of high-volume treated palm oil fuel ash to produce sustainable self-compacting concrete

Palm oil fuel ash is a supplementary cementitious material (SCM) generated from the combustion of palm oil fibers and shells in palm oil mills to produce electricity, and One approach to reduce the carbon dioxide emissions and increase the sustainability of concrete by substitute a significant amount of ordinary Portland cement (OPC) with it. This study conducted laboratory investigations to evaluate the use of high-volume treated palm oil fuel ash (T-POFA) in producing economical and eco-friendly self-compacting concrete (SCC). The concrete mixtures were prepared with 0%, 50%, 60% and 70% replacement (by mass) of OPC with T-POFA at a constant water/binder ratio of 0.35. Self-compactability testing methods were also employed to evaluate the fresh properties of SCC. Compressive strength and drying shrinkage tests were performed and investigated for up to 6 months and 1 year, respectively. An acid attack resistance test was also conducted on the concrete specimens. Results show that the substitution of OPC with high-volume T-POFA can improve the fresh properties of concrete. At an early age, SCCs containing 50%–70% T-POFA have lower compressive strength than the control SCC mix containing 100% OPC. However, the concrete specimens attained a compressive strength equivalent to that of the control at an age of 28 days and an even higher compressive strength at later ages. The specimens containing high-volume T-POFA have lower drying shrinkage and exhibited better performance against aggressive chemical attack. Cost analysis and carbon dioxide (CO2) emission calculation showed that the T-POFA concrete specimens have 8%–12% lower cost and up to 45% lower CO2 emission than the control SCC mix. The results suggest that T-POFA can be utilized as a cement replacement up to 70% in SCC to produce low-cost and sustainable concrete.

Microstructure of cement paste with natural pozzolanic volcanic ash and Portland cement at different stages of curing

The use of volcanic ash as a partial substitute to Portland cement can be a viable alternative for producing sustainable and durable cementitious materials. This study investigates the effect of early and late age curing of hardened cement pastes made with volcanic ash and Ordinary Portland Cement (OPC). Pore and microstructure studies were performed on hardened cement pastes prepared with 10% incremental substitution of volcanic ash up to 50% substitution of OPC. Densification in hardened cement pastes was attributed to formation of Calcium Silicate Hydrate (C-S-H) and Calcium-Alumino-Silicate-Hydrate (C-A-S-H) gels, while the development of Magnesium-Silicate-Hydrates (M-S-H) led to decalcification of C-S-H and C-A-S-H gels which resulted in an increase in porosity of the cementitious matrix. A combination of bulk and surface characterization techniques was used to facilitate effective usage of volcanic ash as a potential substitute for Portland cement that provides a sustainable construction material, and environmentally friendly solution to volcanic ash disposal.

Fly ash/paper sludge as constituents of cements: hydration phases

Ternary cements prepared with equal amounts of thermally activated paper sludge and fly ash in proportions of 35% and 50%, in substitution of ordinary Portland cement, are mixed to study their phase stability. The underlying intention is to increase the proportional substitution of waste products in these types of cement, thereby consigning less waste to landfill sites. The hydration phases of the cement specimens were analysed using thermogravimetric/derivative thermogravimetric (TG/DTG) analysis, X-ray diffraction, scanning electron microscopy/energy-dispersive X-ray (SEM/EDX) spectroscopy. The phases identified in the cement blends include Portlandite, monocarboaluminate compound C4AC̅H12, and layered double hydroxides–type compounds (LDH), as well as ettringite and calcium silicate hydrate gels. Increased formation of both tetracalcium aluminate carbonate 12 hydrate (C4ACH12) and LDH-type compounds and reductions in ettringite and portlandite were observed when the proportional substitution of cement by waste products rose from 35% to 50%. A characteristic compound of pozzolanic reactions, bicalcium silicate (C2ASH8), was not observed, suggesting that it is inhibited in these types of substitutions.

GLOBAL WARMING AND CONSTRUCTION ASPECTS

The manufacture of cements with several main constituents is of particular importance with regard to reducing climatically relevant CO2 emissions in the cement industry. This ecological aspect is not the only argument in favor of Portland composite cements. They are also viable alternatives to Portland cement from the technical point of view. Substitution of ordinary Portland cement (CEM I) by Portland composite cements (CEM II) and (CEM III), which clearly possess different chemical and mineralogical compositions, results in changes of their reaction behavior with additives like superplasticizers. A common admixture to CEM I in that sense is limestone (industrial CaCO3). Its interaction with polycarboxylates is ignored and its inertness is taken for granted. This study provides a systematic approach in order to better understand the interaction of these polymeric superplasticizers with CaCO3 by adsorption and zeta potential measurements. The results give some fundamental understanding in how far the cement industry can reduce the production of cement clinker by replacing it with limestone as admixture and consequently the CO2-emission is reduced, which is of high political and environmental interest.

Hydration characteristics and compressive strength of hardened cement pastes containing nano-metakaolin

In this study the effect of inclusion of nano-metakaolin (NMK) to ordinary Portland cement (OPC) on the hydration characteristics and microstructure of hardened OPC–NMK pastes was studied. The OPC–NMK blends were prepared by the partial substitution of OPC by NMK (4, 6, 10 and 15 weight %). The fresh pastes were made using an initial water/solid (W/S) ratio of 0.27 by weight and then hydrated for various time intervals. At the end of each hydration time, the hardened blended cement pastes were tested for compressive strength, free lime content, combined water content, X-ray diffraction (XRD) analysis, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The compressive strength results revealed that the inclusion of nano-metakaolin into OPC improved the mechanical properties of NMK–OPC pastes during almost all ages of hydration, especially with the paste containing 10 wt% NMK. The compressive strength values obtained for OPC paste blended with 4% silica fume (SF) and 6% NMK are comparable to those of the neat OPC paste. The DSC thermograms and XRD diffractograms obtained for some selected hardened pastes indicated the formation of amorphous calcium silicate hydrates, calcium sulfoaluminate hydrates, calcium aluminate hydrate and calcium hydroxide. SEM micrographs showed the formation of a dense microstructure for the hardened OPC–NMK and OPC–NMK-SF pastes as compared to the neat OPC paste after 90days of hydration.

Hydration and mechanical properties of cement/sludge/anhydrite gypsum system

Setting and hardening of fresh blends of ordinary Portland cement (OPC), fired drinking water treatment sludge (DWTS) and calcined anhydrite gypsum were investigated. Sludge or Portland cement was substituted with 5 wt%, 10 wt% or 15 wt% of anhydrite gypsum. These systems lead to the preparation of supersulfated cement. These blends were shown to possess both the advantages of gypsum (early hardening, high early strength and enhanced workability) and Portland cement (improved durability in moist conditions). The initial and final setting time, bulk density and compressive strength of cement pastes were measured. Differential scanning calorimetry, X-ray diffraction and Fourier transform infrared spectroscopy techniques were used to investigate the hydration products. Substitution of DWTS with 15% anhydrite accelerates the final setting time and increases the bulk density as well as the compressive strength. Substitution of OPC with 5% anhydrite gives the same results but extends the final setting time. It can be concluded that supersulfated cement can be prepared from samples with 10–15 wt% anhydrite substituted DWTS or from the sample with 5 wt% anhydrite substituted OPC.

Physico-mechanical properties of composite cement pastes containing silica fume and fly ash

This works aims to study the effect of partial substitution of ordinary Portland cement (OPC) by silica fume (SF) and fly ash (FA) on the physico-mechanical properties of the hardened OPC–FA–SF composite cement pastes. The OPC was partially replaced by 20% and 30% fly ash along with 5% and 10% silica fume. The phase composition of the hydration products was investigated using XRD and DTA techniques. It was found that, the increase of FA content in OPC–FA–SF composite cement decreases the water consistency values and increases the setting times. On the other hand, the increase of SF content leads to increase the water of consistency and decrease the setting times. The partial substitution of OPC by FA and SF leads to higher porosity values with a consequent decrease in the compressive strength values especially during the early ages of hydration. At the later ages of hydration, however, the OPC–FA–SF cement pastes possess total porosity and compressive strength values close to those of the neat OPC paste. The lower of free lime contents were obtained for OPC–FA–SF composite cement pastes with the formation of further additional amounts of CSH as a result of the pozzolanic reaction. The results showed also that, the physico-mechanical properties of composite cement paste [OPC (65%)–FA (30%)–SF (5%)] were improved at later ages.

PHYSICO-CHEMICAL AND MECHANICAL PROPERTIES OF BLENDED CEMENT PASTES CONTAINING RICE HUSK ASH AND METAKAOLIN

This work aims to study the effect of partial substitution of ordinary Portland cement (OPC) by rice husk ash (RHA) andmetakaolin (MK) on the physico-chemical and mechanical properties of the hardened OPC-RHA-MK blended cement pastes. OPC was partially replaced by different ratios of MK (10, 15 and 20%) and a constant ratio of RHA (5%) and the resulted cement blends were hydrated in the paste form by using the water/cement ratios required for the standard water of consistency; the pastes thus obtained, were hydrated for 1, 3, 7, 28, and 90 days. At the end of hydration period, the cement pastes were tested for compressive strength, total porosity and hydration kinetic via determination of free lime contents.The phase composition of the formed hydration products was investigated using X-ray diffraction (XRD) and differential thermal analysis (DTA) techniques. It was found that, the substitution of ordinary Portland cement (OPC) by rice husk ash (5% RHA) enhances the physico-chemical and mechanical properties of the hardened blended cement pastes as compared with the neat OPC. The results of compressive strength indicated slightly higher values for the pastes made of OPC–RHA-MK blends containing 5% RHA blended with 10, 15 % MK. However, the blended cement paste derived from OPC-RHA-MK blend containing 5% RHA blended with 20% MK, for economic reasons, was taken as the most suitable mix containing both RHA and MK. The partial substitution of OPC by RHA and MK leads to higher porosity values with a consequent decrease in the compressive strength values especially during the early ages of hydration. It was found that, the increase of MK content in OPC-RHA-MK blended cement pastes resulted in an increase in water consistency and setting times. Lower values of free lime contents were obtained for OPC-RHA-MK blended cement pastes, with the formation of further additional amounts of CSH, as a result of the pozzolanic reaction.

Use of Bentonite and Organobentonite as Alternatives of Partial Substitution of Cement in Concrete Manufacturing

In order to study the capacities of a new occurrence of Brazilian clay samples as partial replacements of cement, a bentonite sample was selected for utilization in the natural and modified forms for present study. The natural bentonite (BBT) was modified by anchorament of 3-aminopropyltrietoxisilane (BBTAPS) and 3,2-aminoethylaminopropyltrimetoxisilane (BBTAEAPS) in the surface of component minerals of bentonite sample. The original and organo-bentonite samples were characterized by elemental analysis, scanning electron microscopic and textural analyses. The values of micropore area were varying from 7.2 m2 g−1 for the BBT to 12.3 m2 g−1 for the BBTAEAPS. The bentonite samples were characterized by the main variable proportion of bentonite in the natural and intercalated forms (2, 5, 10, 15, 20, 25, 30, and 35 % by weight of cement) in the replacement mode whiles the amount of cementations material. The workability, density of fresh concrete, and absorption of water decreased as the substitution of ordinary Portland cement by perceptual of natural and modified bentonite increased. The results reveal that workability decreased with decrease of the amount of natural bentonite in the concrete, same behavior is observed for bentonite functionalized, varying from 49 to 28 mm. The energetic influence of the interaction of calcium nitrate in the structure of blends was determined through the calorimetric titration procedure.

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.

Utilization of Pakistani bentonite as partial replacement of cement in concrete

This research is aimed at evaluating Jehangira bentonite, deposited at 33°59′56″ latitude and 72°12′47″ longitude in the survey of Pakistan topographic sheet 43C/1, as partial replacement of cement. The main variable is the proportion of bentonite (3%, 6%, 9%, 12%, 15%, 18% and 21% by weight of cement) in replacement mode while the amount of cementitious material, water to cementitious material ratio, fine and coarse aggregate content were kept constant. Test results substantiate the feasibility to develop low cost concrete using bentonite. It will reduce energy consumption and greenhouse gases related to cement production as well as improve the durability of the system.The scanning electron micrographs indicated that bentonite particles are flaky and elongated. The average size of particle ranged in between 4 and 5μm. All the mixes satisfied the requirement of strength activity indices as laid down by ASTM C618. The workability, fresh concrete density and water absorption decreased as the ordinary Portland cement substitution by bentonite increased. The comparative compressive strength analysis indicated that at 3days of testing, the mixes containing bentonite showed lower strength than control mix while at 56days of testing, the bentonite mixes showed higher strength than the control mix. Mixes containing bentonite performed better than control mix against acid attack. The aggressiveness of sulfuric acid on concrete was more pronounced than hydrochloric acid.

Artificial pozzolanic cement pastes containing burnt clay with and without silica fume

Pozzolanic cement blends were prepared by the partial substitution of ordinary Portland cement (OPC) with different percentages of burnt clay (BC), Libyan clay fired at 700 °C, of 10, 20, and 30%. The pastes were made using an initial water/solid ratio of 0.30 by mass of each cement blend and hydrated for 1, 3, 7, 28, and 90 days. The pozzolanic OPC–BC blend containing 30% BC was also admixed with 2.5 and 5% silica fume (SF) to improve the physicomechanical characteristics. The hardened pozzolanic cement pastes were subjected to compressive strength and hydration kinetics tests. The results of compressive strength indicated slightly higher values for the paste made of OPC–BC blend containing 10% BC The results of DSC and XRD studies indicated the formation and later the stabilization of calcium silicates hydrates (CSH) and calcium aluminosilicate hydrates (C3ASH4 and C2ASH8) as the main hydration products in addition to free calcium hydroxide (CH). Scanning electron microscopic (SEM) examination revealed that the pozzolanic cement pastes made of OPC–BC mixes possesses a denser structure than that of the neat OPC paste. Furthermore, the addition of SF resulted in a further densification of the microstructure of the hardened OPC–BC–SF pastes; this was reflected on the observed improvement in the compressive strength values at all ages of hydration.

Influence of Metakaolin on Resistivity of Cement Mortar to Magnesium Chloride Solution

An experimental study for the resistance of mortar paste specimens incorporating 0, 5, 10, 15, 20, 25, and 30% metakaolin (Mk, produced by firing kaolin at 820°C for 2 h) to the magnesium chloride solution was reported. Results confirmed that mortar specimens with a high replacement level of metakaolin showed higher resistance to magnesium solution. The reduction of calcium hydroxide and the increase of secondary calcium silicate hydrate (CSH) in the cement matrix results from the pozzolanic reaction of Mk. The compressive strength values of the blended ordinary portland cement (OPC) mortars specimens improved relative to those containing no Mk, up to 25% by weight OPC substitution, and then decreased up to 30% by weight Mk. Scanning electron microscope microstructures indicate a good improvement for the matrix structure of the blended cement mortars, in which a denser structure was observed.

A study towards “greener” construction

The manufacture of cements with several main constituents is of particular importance with regard to reducing climatically relevant CO2 emissions in the cement industry. This ecological aspect is not the only argument in favor of Portland composite cements; they are also viable alternatives to Portland cement from the technical point of view. Substitution of ordinary Portland cement (CEM I) by Portland composite cements (CEM II) and (CEM III), which clearly possess different chemical and mineralogical compositions, results in changes of their reaction behavior with additives like superplasticizers. A common admixture to CEM I in that sense is limestone (industrial CaCO3); its interaction with polycarboxylates is ignored and its inertness is taken for granted. This study provides a systematic approach in order to better understand the interaction of these polymeric superplasticizers with CaCO3 by adsorption and zeta potential measurements. The results give some fundamental understanding in how far the cement industry can reduce the production of cement clinker by replacing it with limestone as admixture and consequently the CO2 emission is reduced, which is of high political and environmental interest.

Durability of gamma irradiated polymer-impregnated blended cement pastes

This study is focusing on durability of the neat blended cement paste as well as those of the polymer-impregnated paste towards seawater and various concentrations of magnesium sulfate solutions up to 6 months of curing. The neat blended cement paste was prepared by a partial substitution of ordinary Portland cement with 5% of active rice husk ash (RHA). These samples were cured under tap water for 7 days. A similar paste was impregnated with unsaturated polyester resin (UPE) followed by gamma rays ranging from 10 to 50 kGy. The obtained data indicated that the polymer-impregnated specimens higher values of compressive strength than those of the neat blended cement paste. In addition, the polymer-impregnated blended cement specimens irradiated at a dose of 30 kGy and neat blended cement specimens were immersed in seawater and different concentrations of magnesium sulfate solutions namely, 1%, 3% and 5% up to 6 months. The results showed that the polymer-impregnated blended cement (OPC–RHA–UPE) paste irradiated at a dose of 30 kGy has a good resistance towards sulfate and seawater attack as compared to the neat blended cement (OPC–RHA) paste. These results were confirmed by scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) studies.

Efecto de la adición mineral cal- zeolita sobre la resistencia a la compresión y la durabilidad de un hormigón

The international construction practice reports a remarkable use and development of high performance concretes, with excellent results in the durability properties, associated with a very dense cement matrix, defined from the use of high volumes of very fine minerals additions, such as, fly ash, silica fume, metakaolin and other fine powders. For the developing countries, among others Cuba, the use of these pozzolanic additions are relatively expensive, given for the high import prices of these pozzolanic materials, thus, the utility of using the national available pozzolanic sources with proven reactivity, as a partial substitute of the Ordinary Portland Cement (OPC) contents in the concrete mixtures without its properties are affected. The present paper shows the results of the study on the influence of substitution level of Ordinary Portland Cement contents by lime – pozzolan binder in combination with chemical admixture, in the behavior of the compression strength and the durability properties of a concrete. Several levels of OPC substitution are evaluated, using zeolite as pozzolan. The results obtained prove the possibility to carry out the partial replacement of high volumes of OPC by lime – zeolite binder, without affecting the values of compression strength required and their behavior before action of the chloride ion penetration and the carbonation.

Pakistani bentonite in mortars and concrete as low cost construction material

A Pakistani bentonite, in “as is” (21 °C) and “heated” (150 °C, 250 °C, 500 °C, 750 °C and 950 °C) conditions, was incorporated in mortar cubes, concrete cylinders and concrete beams as a partial substitute for Ordinary Portland cement (OPC) and studied in detail. Results showed that OPC mortars and concrete containing 20% “as is” and 25% “heated to 150 °C” bentonite could be used as low-cost construction materials. They will also reduce energy consumption, preserve natural resources and solve environmental problems related to cement production as well as augment the durability and life cycle of the concrete structures. The X-ray diffraction patterns showed that bentonite possessed both crystalline and amorphous phases. The strength activity indices (SAI) after 7 and 28 days were higher than 75% for “as is” and “heated” bentonite, except for the 950 °C samples, which was below the ASTM C618 specified limit of 75%. The maximum SAI was shown by “150 °C heated” bentonite. The compressive strength data also showed similar results for OPC mortar cubes and concrete cylinders containing “150 °C heated” bentonite. When compared with the control mixture, the compressive strength values were the same as for mortar containing 25% bentonite as replacement of OPC. However, these values decreased in concrete initially and started to gain strength remarkably after 28 days. Resistance to sulphate attack and water absorption tests on mortar cubes soaked in 2% magnesium sulphate and 5% sodium sulphate solutions demonstrated consistent improvement as the bentonite content in them was increased. The modulus of rupture of all concrete beams decreased as the OPC substitution level by bentonite increased from 20% to 40%. Bond strength of OPC mortar containing 20% “as is” and 25% “heated to 150 °C” bentonite in brick prisms was almost the same as that of control mixture.