OPC Cement Research Articles

Approaches to achieve fluidity retention in low-carbon calcined clay blended cements

High meta kaolin content (e.g. 50 wt%) present in a calcined clay blended into a composite cement is positive with respect to early strength development, but significantly decreases the dispersing effectiveness of PCE superplasticizers. Moreover, it has been observed that for such cements, slump retention is much more difficult to achieve than in OPC or other composite cements. In this study, several approaches to achieve extended workability times in mortars prepared from composite cements holding 20–40 wt % of a calcined clay were investigated. First, it was found that the slump retaining performance of a common industrial ready-mix type HPEG PCE rapidly decreased when the portion of calcined clay was increased in the blended cement. Furthermore, a combination of the ready-mix HPEG PCE and a retarder (sodium gluconate) which is commonly applied in ready-mix concrete also could not much improve fluidity retention, thus highlighting the difficulty of slump retention for such cements. To solve this problem, a new admixture formulation is introduced based on a combination of a precast type HPEG PCE and a novel PCE-LDH nanocomposite. This approach to improve slump retention was tested on composite cements holding 20–40 wt % of a calcined clay high in meta kaolin content. Mortar tests revealed that the high water-reducing (precast) type HPEG PCE and the PCE-LDH nanocomposite work synergistically and can achieve a significant improvement in fluidity retention of such calcined clay blended cements. A mechanistic investigation revealed that the PCE which was intercalated in between the [Ca2Al(OH)6]+ main layers of the PCE-LDH nanocomposite is released gradually from the mixed metal hydroxide via anionic exchange with sulfate anions present in the pore solution. This way, an extended workability time was achieved in the mortar.

Thermal conductivity and shrinkage properties of slag-based cement concretes

The thermal conductivity, specific heat, and total drying shrinkage test of slag blended OPC cement is conducted by using a Hotdisk-2500S thermal conductivity, and non-contact shrinkage deformation measurement apparatus based on ISO 22007-2 and GB/T50082-2009 test standards, respectively. The influence of replacement rates of slag cement (0, 30, 50, and 70%) and high-temperature exposure (21, 200, 400, 600, and 800 °C) on the thermal properties of concrete is analysed. The results show that for all three concretes, the thermal conductivity initially decreases with increasing temperature up to 400 °C, then after it remains almost constant between 400 and 600 °C, and gradually begins to decrease again up to 800 °C. Furthermore, thermal diffusivity of concrete group G-70, shows 21.4, 21.6, and 37.6% increment in 21, 200, and 600 °C temperature exposure respectively compared to concrete group G-0. Though, as the exposure temperature keeps rise to 800 °C, its value starts to decrease. Furthermore, the results indicated that high volume slag cement content in the concrete mix lessen the drying shrinkage of the concrete at later age. Test data is used as a function of temperature and slag replacement to establish high temperature relations for thermal properties. The proposed thermal property relationships can be used as input data for validation in computer programs and to evaluate the response of OPC and slag blended Portland cement concrete structures subjected to fire.

Strength analysis of soil blocks admixed with sugarcane bagasse ash.

This paper is mainly focusing on the stabilization of soil using sugarcane baggase ash (SBA) as a soil stabilizer. The locally available soil samples were collected and their properties were determined. Based on the laboratory test results the soil was classified as fine-grained soil. Soil stabilized blocks of dimensions 15cm x 15cm x 15cm were prepared with the following soil, cement and SBA combinations 100% soil, 80% soil + 20% cement, 80% soil +10% cement +10% SBA, 80% soil + 8% cement+ 12% SBA and 80% soil + 6% cement +14% SBA. Plain OPC cement of 43 grade and SBA from sugar factory Goa was used for the soil blocks. The blocks were moist cured for a period of 28 days. The soil stabilized blocks were then tested for their compressive strength under the universal testing machine according to BIS specifications. The effects of the SBA on the strength of the soil blocks were studied and it could be concluded that SBA can be used as a partial replacement of cement.
 Key words: sugarcane bagasse ash, compressive Strength, soil stabilized block, cement.

Sulfate and Chloride Resistance Properties of Portland Cement Blends

About 53% area of Bangladesh is alluvial deposited and affected by sulfate, salinity and chloride in water and soil. Existing sulfate and chloride can severely damage the building in coastal regions. In this paper durability of cement is evaluated on the basis of strength of mortar cube, concrete cylinder test. Besides the sulfate resistance is measured by change of length of the mortar bar specimens during exposure to sulfate solution and the attacking chloride properties by Rapid chloride ion penetration test using OPC, PCC, 20% FA, 30% FA and 40% FA. The strength was observed in cube sample about 40.65, 37.2MPa after 13 weeks in sulfate solution and linear expansion was obtained about 0.28% and 0.133% for OPC and PCC cement with reference to the water. The compressive strength of the cylindrical specimens was about 16.96, 18.34 MPa for OPC and PCC, respectively at the age of 28 days. The permeability of chloride ion of OPC sample was 22.8% higher than the PCC at this age.
 Journal of Engineering Science 12(1), 2021, 69-75

Effect of BaCO3 reactivity and mixing procedure on sulfate-resistant cement performance

The present study focuses on exploring the effects of reactivity and degree of dispersion of BaCO3 additions in the manufacture of sulfate-resistant OPC cements. A new electrochemical deposition method is attempted to effectively disperse BaCO3 particles (studying two different materials with particle size: D50 = 11.45 and 2.37 μm) on cement to enhance their reactivity and favour sulfate immobilisation in the form of BaSO4. The barium carbonate additions, particularly the finest, activate cement hydration to a greater extent. Electrodeposition is also observed to improve early age reactivity (2 d–7 d) in fine BaCO3. Cement paste bearing 15 wt % BaCO3 is more resistant to sulfate attack by a 5% (w/v) solution of Na2SO4 (180 d at 23 °C) than a commercial sulfate-resistant cement, although secondary ettringite and gypsum precipitated in all cases.

Influence of in-situ casting temperature and curing regime on the properties of blended cement concretes under hot climatic conditions

Casting temperature and curing method significantly affect the properties of concrete, especially the blended cement concretes. Consequently, it is imperative to study the influence of casting temperature and curing regime on the properties of concretes. This paper reports results of a study conducted to evaluate the properties of plain and blended cement concretes prepared using very fine fly ash (VFFA), fly ash (FA), silica fume (SF), ground granulated blast furnace slag (GGBFS) and natural pozzolan (NP) cast and cured under varying temperature and curing conditions. The concrete specimens were prepared under natural summer atmosphere at intital concrete temperature of 25, 32, 38 or 45 °C. The specimens were cured under laboratory conditions by water ponding and under hot weaterher conditions by covering with wet burlap or applying a curing compound. The effect of casting temperature and curing regime on the properties of the studied concretes was evaluated by measuring compressive and split tensile strength up to 180 days, pulse velocity up to 90 days and depth of water penetration after 28 days of curing. As expected, the properties of concrete specimens cured by water ponding were better than those cured by covering with wet burlap or applying a curing compound. The properties of blended cement concretes were better than those of plain cement concretes at later ages due to the pozzolanic reaction. It is postulated that the optimum casting temperature is 32 °C for OPC and SF cement concretes while it is 38 °C for VFFA, FA, GGBFS and NP cement concretes. This finding differs with the current international practice of limiting the casting temperature to 35 °C.

Assessment of POFA -Cementitious material as backfill barrier in DSRS borehole disposal: 226Ra confinement

Disused Sealed Radioactive Sources (DSRS) borehole disposal is an innovative concept recommended by international atomic energy agency (IAEA) to improve the safety and security of the management end point for these sources. A green application of Palm Oil Fuel Ash (POFA) as a supplementary material for cementitious backfill barrier in DSRS borehole disposal facility is proposed. Samples with up to 50% POFA replacement complied with the mechanical and hydraulic performance requirements for backfill barriers in retrievable radioactive waste disposal facilities. The structures of one year old OPC and optimum OPC-POFA cement backfills were evaluated using FESEM, XRD, EDXRF, BET, and TGA and their 226 Ra confinement performances were assessed. 30% POFA replacement improved the geochemical conditions by reducing competitive Ca2+ release into the disposal environment. It enhanced 226Ra confinement performance independently on the amount of water intrusion or releases below 2% of 1 Ci source. The improved performance is attributed to the higher fraction of active sites of OPC-POFA backfill compared to that of OPC backfill. 226Ra sorption onto C–S–H is irreversible, spontaneous, endothermic, and independent on the degree of the surface filling. The provided experimental data and theoretical analysis proved the feasibility of this green use of POFA in reducing the radiological hazard of 226Ra.

Pengaruh Penggunaan Fly Ash dari Berbagai Sumber terhadap Sifat Kimia dan Sifat Fisika pada Semen Tipe I (OPC)

The aim of this study is to utilize fly ash from various sources on chemical and physical properties of cement type I (OPC). Utilization of fly ash can improve the strengthness of the cement. It can reduce the waste of fly ash by utilization into cement process. The procedure has been carried out on cement type I (OPC) with the addition of fly ash additives from various sources with concentration variations such as 10% and 20%. Utilization of fly ash as additives substance in cement works to improve the quality of cement. The main parameter in determining the quality of cement is determined by the compressive strength. The results of the compressive strength test showed that the addition of fly ash with a concentration of 10% had a higher effect on the compressive strength than the addition of a concentration of 20%. 5 types fly ash from various sources, fly ash from PT Sinar Mas gives greater compressive strength at 28 days. the addition of fly ash additives to OPC cement mixture has chemical and physical properties which are not much different from properties of PCC cement.

Valorisation of organic waste: Use of olive kernels and pomace for cement manufacture

The olive oil industry generates huge amounts of solid olive mill waste (SOMW), which have a dangerous impact on the environment. The effect of replacing clinker with pomace and olive kernel on cement was investigated in this work to reduce waste. Its effect on mechanical strength, heat evolution, setting time and particle size was monitored with two replacement percentages, 10% and 30% by mass. The mechanical tests carried out on cement mortars containing 10% of these additives at 365 days resulted in a compressive strength of 51 MPa and 50 MPa for mortars based on olive pomace and olive kernel respectively, while the reference (OPC) obtained 51.35 MPa. After 120 min of grinding, cements with 30% additions developed a SSB higher than OPC 6969 and 7193 cm2/g for olive kernels and pomace respectively, and the residue on the 45 μm sieve reached 20.7% for OPC; however, negligible for the other cements, the DSC was used to measure the heat flow and the enthalpy of hydration. The results show that high values of Qmax, (868.76 J/g) and ΔH (8164.75 J/g), were obtained for OPC. Proportionality (Pp) modelling by Delphi 6 allowed to obtain the key parameter: Proportionality (Pp) modelling by Delphi 6 allowed to obtain the key parameter: enthalpy (with a Pp: 91.7% highest) as the OPC cement witch had the highest ΔH, it developed the best mechanical and rheological parameters. Therefore, ΔH is the key parameter. The results also showed that these agricultural wastes (pomace and olive kernel) can be successfully used for the manufacture of cement and can lead to stiffer mortars than OPC.

The analysis of tensile strength and elasticity in slag concrete with curing variations at 90 days age

Cement is a concrete constituent material that has a great influence on concrete quality, both normal and high-quality concrete. High quality concrete in SNI 03-6468-2000 is defined as concrete which has compressive strength characteristics above 41.4 MPa. During the process, cement produces gas emissions obtained from combustion, calcination of limestone, and the use of electrical energy. The purpose of using cement in the preparation of concrete itself is as a binder between aggregates. Nowadays, commonly used cement (OPC cement) can be replaced with slag cement. Slag cement is the result of the addition of Granulated Blast Furnace Slag into the final grinding of cement which is a waste product from the steel ore smelting process. This research is comparing the magnitude of the tensile strength and the modulus of elasticity of the samples with 100% OPC cement and those with 100% slag cement. The samples used were cylinders with 15 cm diameter and 30 cm height. The tests were carried out when the concrete reaches 90 days age. The curing of the samples was carried out with four variations which is by submerging those in tap water, Kuala Tanjung sea water, Sulphuric Acid water, and compound curing. The results of this test were obtained if the slag cement-used concrete is able to have a tensile strength that is almost the same as OPC cement-used concrete which is 4.341 MPa for normal concrete and 4.293 MPa for slag concrete and its modulus of elasticity of 46103.67 MPa for normal concrete and 46892.82 MPa for slag concrete.

Electrochemical and physico-mechanical characterizations of fly ash-composite cement

In this paper, the corrosion of C-steel in OPC-fly ash-composite cement pastes (OPC-FA-CCP) was examined with different fly ash (FA) contents (0, 10, 25 and 50 mass%) and immersion times in the absence and presence of spinach extract as a green-corrosion inhibitor. The effect of replacing FA in cement composition on its physical, chemical, mechanical and microstructure properties using a variety of techniques has been also studied. The results indicated a significant increase in compression strength (CS) and gel/space ratio (X) upto 90 days in the case of OPC-FA-CCP containing 10 mass% FA. At higher FA replacement levels (≈25–50 mass%), the CS and X values decreased. SEM confirmed the presence of a surface layer of amorphous-ill-crystalline C-S-H as a gel product on the FA grains, with prolonged time showing dense crystalline hydrated fibril-C-S-H products. The C-steel immersed in the pure OPC cement (FA0S) has the highest corrosion potential (Ecorr = −461 mV) vs. SCE. With the increase of the FA content the Ecorr shifts to a more negative value with an indication of the decrease in the corrosion resistance of the rebar. During the first 6 h of immersion, the increased thickness of the passive film leads to a remarkable decrease in the corrosion rate. As the dipping time increases, the current corrosion density in all tested OPC-FA-CCP mixtures is unexpectedly reduced. A significant improvement in corrosion resistance of rebar was achieved in the presence of spinach extract. All the corrosion parameters were also calculated.

Investigation on binder and concrete with fine grinded fly ash and silica fume as pozzolanic combined replacement

This paper presents the persuade of Fine Grinded Fly Ash (FGFA) and Silica Fume (SF) as a modified pozzolanic replacement to the binder. The OPC cement was combined replaced with FGFA in 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35% and 40% and Silica Fume in 5% to weight of cement. The consistency of water is tested based on the values Cement, FGFA and SF combined pastes are manufactured and tested for its initial setting time and final setting time of modified binder. And also the slump cone and flow Table test for fresh concrete and hardened high-performance Concrete compressive, split tensile and flexural strengths have been conducted. The results show that the properties of modified binder and both fresh and hardened high-performance concrete highly influenced by the percentage of FGFA and SF replacement. This study shows that the influence of the combination of FGFA and SF and the higher strength gains was observed at the initial and later ages of both modified mortar and high-performance Concrete and compared with Control Specimen (CS).

THE INFLUENCE OF BASALT MINERALS AS CEMENT SUBSTITUTION MATERIALS IN MORTAR

This study was conducted to determine the effect of the concentration of basalt as a cement substitution material in mortar. Basalt was analysed by XRD and XRF. From the XRD results, the diffractogram shows the dominant phases, such as anorthite, augite, forsterite, and quartz or silicon oxide. SiO2, Al2O3, Fe2O3 are the main components in basalt, as can be seen from the XRF. With the concentration at 5% of the basalt before the calcination, the optimum compressive strength of the OPC and PCC cement mortar was obtained. The highest compressive strength of the OPC cement mortar was 24.97MPa with a porosity of 2.4% and absorption of 1.29 %. Furthermore, the highest compressive strength of the PCC cement mortar was 22.55MPa with a porosity of 4.8% and absorption of 2.52 %. This result indicates that the substitution of composite cement with a basalt with a concentration of 5% can increase the compressive strength of the mortar.

Optimized Structural Performance of Paver Blocks of Bajri Concrete: NRM Partly Substituting Cement

The discarded object dart during alumina extraction from bauxite ores in Bayers process is Red Mud. The solid/ liquid insoluble by-product dumped in exposed red mud ponds which are radioactive, highly alkaline and environmental contaminant to soil, surface water and ground water and possess disposal threats. Recent trend in increased urbanization and modernization has plenty of use of exterior flooring by concrete pavers block depending upon traffic load and volume. Present work is to know whether this red mud can be reused as a sustainable construction material to replace cement. The XRF spectroscopic advantage is taken to determine the composition identities between red mud and OPC cement. The study reveals the optimized percentage of red mud blend with cement after neutralization normalization. It cannot be disposed of easily. Attempt has been made to use bajri as the coarse aggregate instead of 12mm chips. The crusher by-product is having less use as construction materials. So the spare of cement by compensating with red mud and use of bajri shall be cost effective, environmentally sustainable and convenient disposal of the harmful waste. The mechanical characteristics like compressive, flexural, and split tensile strength etc., at 0%, 10%, 20%, 30% and 40% replacement of cement by red mud is found by using compressive testing machine (CTM) and universal testing machine (UTM) adhering to IS : 15658 (2006) and amended in 2011. The 20% OPC cement substitution by red mud is found to be adequate and will maintain sustainability.

Evaluation of Physical and Chemical Properties of OPC and PPC Cement

Cement is a one of the largest industrial product that is manufactured in more than 120 countries. Increasing costs of cement have recorded a continuous growth in its usage in the Indian construction industry. India is marching forwarding cement Production. Cement was first invented by the Egyptians. India started the same in 1904 in Tamil Nadu in Ariyalur. OPC and PPC are the two most widely used cement types in India. There are significant differences in mortar strength, fineness, consistency, soundness, chemical composition and setting time of same type of cement collected from different cement suppliers. Experiments were conducted on 9 brands of OPC and 6 brands of PPC samples collected from local market in Solapur, Maharashtra, India. In this study, the amounts of main chemical constituents such as Silicon oxide (SiO2), Aluminum oxide (Al2O3), Iron Oxide (Fe2O3), Magnesium Oxide (MgO), Sulphur Trioxide (SO3), Calcium Oxide (CaO), and Loss on Ignition (LOI) were determined and compared. All the results pbtained during this study were presented in order to provide qualitative and quantitative differentiation between cement sample. These results were compared with limits specified in the BIS. The possible reasons for variation in chemical composition and their effect on properties of cement have been discussed.

Characteristics of Hydration and Correlation on Cement-Based Thermal Insulation Material

Cement-based thermal insulation material was manufactured using OPC, lime, anhydrite, and CSA cement in this study. The morphology and physical properties of the material were analyzed using XRD. All samples had ettringite, Ca(OH)2, and CaCO3 crystals. The XRD peak intensity of the ettringite and Ca(OH)2 slightly increased with an increase in curing time from 3 to 7 days. The compressive strength values at 28 days of specimens 1-8 were in the range of 0.25-0.32 MPa, and the compressive strength values of specimens 3-8 were > 0.3 MPa. The coefficients of correlation between compressive strength and apparent gravity at 7 days and those between compressive strength and ettringite/Ca(OH)2 XRD peak intensity at 28 days were above 0.8. That is, the compressive strength exhibited an influence on apparent gravity at 7 days and on hydrate at 28 days. The thermal conductivity of all specimens was 0.041-0.045 W/mK, and the highest value of thermal conductivity was shown by specimen 5. The coefficient of correlation between apparent gravity and thermal conductivity was 0.84. It was concluded that control of raw materials and hydrates must be considered for manufacturing of insulation materials. The cement-based thermal insulation material in this study could be used in construction fields. Key words: Thermal insulation material, Ettringite, CSA, Compressive strength, Thermal conductivity

Flexural Rigidity in Concrete Beam by using the Crimped Steel Fibers with Rapid Hardening Admixtures

With the increase in the fast track construction industries, the emerging techniques are used for improvement in the concrete strength and its properties. This paper focused on the test results for various mixes of concrete made by replacing OPC cement content with slag and fly ash in varying proportions the use of rapid hardening admixture along with the presence of crimped steel fibers. The flexural strength, crack depth measurement by using the ultrasonic pulse velocity and Elastic modulus of concrete were conducted with different proportions of fly ash (0-15%) and slag (0-25%) being replaced in cement and 0-50% of the fine aggregate is replaced with stone dust. The experimental test results show the volume reduction in flexural members, crack depth measurement by UPV and modulus of elasticity of concrete by scant modulus method was used for various mixes.

Short and long-term behaviour of R.C. beams made with CSA binder

A worldwide increase of the use of Calcium Sulfoaluminate cement (CSA) is observed in the recent years, especially for application for which fast development of mechanical properties and volume stability are required. Moreover, the lower CO2 emission deriving by the CSA manufacturing process than Portland cement (OPC), allows to classify such type of cement as “green binder”. Limited information are still to date available in the scientific literature regarding the short and long-term behaviour of reinforced concrete elements made using pure CSA cement or blended with Portland. The aim of this work is to improve the knowledge about the use of CSA concrete for structural and non-structural application, providing information about the flexural behaviour of reinforced concrete structural beams made replacing different portions of CSA cement with OPC. Mechanical characterization at different ages of the concrete mixtures was performed as well as the monitoring of the volume change properties. Moreover, study of the influence of the environmental condition and service load on the flexural behaviour of the beams was performed. Concretes made with pure CSA or CSA blended with OPC have generally highlighted better mechanical properties than the reference mix made with OPC cements, including a reduction of the drying shrinkage deformations as the amount of CSA cement increases. However, despite the higher compressive strength obtained for the pure CSA and blended concrete mixtures, a comparable elastic modulus with that measured for the reference mixture was observed. The bending tests performed on the beam samples evidenced as the addition of CSA cement seems not influential for crack pattern in terms of crack width, while a better response was observed in case of pure CSA concrete. Moreover, a higher ductile behaviour was obtained for the beam made with a CSA cement amount equal to 30% of the total cement content, reasonably due to the relaxation concrete phenomena, as also confirmed by the long-term results regarding the same type of beams. In fact, such beam has highlighted the highest mid-span deflection at long-term compared with the other monitored beams. However, comparing the experimental results was observe an improvement of the flexural behaviour increasing the CSA amount. In particular the beam made replacing 50% of OPC with CSA binder that has highlighted the lowest percentage increase over time in terms of crack width and mid-span deflection.

Correlation between Concrete Compressive Strength and Rebound Number of River Bed and Crusher Run Coarse Aggregate in Pokhara Valley

Concrete is principally composed of the mixture of cement, fine and coarse aggregates, and water and widely used for every building structure and other infrastructure. Aggregate has important functions as concrete making materials for the hardness and strength of concrete. The objective of this research was co – relation of compressive strength of concrete with Rebound number of crusher and river bed coarse aggregate in respect to the M20 grade of concrete with nominal mix. For this research, sample were taken from Hemja Crusher (HC), Hemja River Bed (HR), Kotre Crusher (KC), Kotre River Bed (KR) and considering sand from single source and commercially available single brand OPC cement. Fifteen cubes (150 mm × 150 mm×150mm) were cast for each sampled sources and the Compressive strength and Rebound number was determined after 7 days, 14 days and 28 days of curing.
 In this research, statistical analysis was carried out to determine the best fit curve by using IBM SPSS. Finally the outcomes of this research indicated that the relationship between rebound number and compressive strength curve is liner.

The Effect of Flyash and Foaming Agent on Setting Time and Strength of OPC Cement- A Experimental Approach

The Effect of Flyash and Foaming Agent on Setting Time and Strength of OPC Cement- A Experimental Approach