Control OPC Research Articles

Influence of physico‐mechanical and electrical resistivity performance of high volume fly‐ash cementitious mortar with low carbon

AbstractA graphene oxide (GO) has the potential to improve the strength and hardness of cementitious matrix. The agglomeration of GO in an alkaline medium of cement matrix reduced the reinforcing efficiency. In this study, two types of control samples were fabricated named OPC‐C (OPC control) and HVFA‐C (OPC + 50% FA control) without the addition of GO and four HVFA cementitious mortar samples HVFA‐G1, HVFA‐G2, HVFA‐G3, and HVFA‐G4 were prepared with incorporation of GO 0.005%, 0.010%, 0.020% and 0.040%, respectively. The results revealed that the superplasticizer stabilized GO in cement mortar, significantly improves the compressive (27.12%) and split tensile strength (38.16%) in the HVFA‐G3 mix as compared to HVFA‐C at a curing age of 90 days. The maximum electrical resistivity attained in HVFA‐G4 (83%) mix as compared to OPC‐C at a curing age of 90 days. In addition, microstructural analysis of HVFA cementitious mortar was conducted using a Field Emission‐Scanning Electron Microscope (FE‐SEM), while the crystallization behavior of hydration products ware examined through Powdered X‐Ray Diffraction (PXRD). Furthermore, the chemical bonding between the hydration products was studied using Fourier Transform Infrared Spectroscopy (FT‐IR). Overall, it is concluded that the superplasticizer stabilized GO in HVFA cementitious mortar, helps to achieve better mechanical strength, electrical resistivity performance, and microstructural behavior.

Converting ladle slag into high-strength cementing material by flue gas carbonation at different temperatures

The aim of this study is to explore the feasibility of valorization of steelmaking ladle slag into a high-strength cementing material through a carbonation-activation step that uses flue-gas, so that a closed-loop recycling solution can be achieved. Flue-gas (20% CO2) carbonation was carried out at ambient (23°C) and elevated (55°C) temperatures. After 24 h of flue gas carbonation at 55°C, ladle slag compacts achieved an average compressive strength of 74.7 MPa with a CO2 uptake equivalent to 12.1 wt.%. In comparison, conducting carbonation at the ambient temperature recorded lower values for strength and CO2 uptake, and yielded a less refined and more porous microstructure. Nevertheless, carbonated compacts under both ambient and elevated temperatures achieved better strength performances at all testing ages than the hydrated OPC control reference specimens. The CO2 in flue gas precipitated as calcite in the paste matrix regardless of curing temperature; however, the elevated temperature of 55°C was found to additionally promote the precipitation of aragonite crystals. In an environmental impact assessment model that uses conventionally-cured OPC as the industry-standard baseline with global warming potential (GWP) of 1204.4 kg CO2-eq/m3, the alternative use of carbonation-activated ladle slag was found to greatly reduce the overall GWP to a range between 39.2 and 247.5 kg CO2-eq/m3, even when taking the increased curing temperature into consideration. This work presents a possible future scenario where high-strength cementing material could be produced by recycling locally sourced slag, stack-captured flue gas, and waste heat energy from steel plants.

Utilization of Waste Glasses as Supplementary Cementitious Materials

Wastes of Glass are recognized as pozzolanic material. This study aims to investigate utilization of local glass wastes in Sudan as supplementary cementitious materials. Two glass wastes specimens having different colors are procured from a local source namely Sudanese Emirati Glass and Metal Company (SEGMAL). Then thy are ground to micro sizes producing two types of glass powders, clear white glass powder (W-GP) and colored glass powder (C-GP). The two Specimens are characterized using tests specified in American Society for Testing and Materials ASTM C311. These tests include chemical properties using X-ray Fluorescence (XRF), Loss on Ignition (LOI), Insoluble Residue (IR), also physical properties such as fineness, specific gravity, water requirement, and strength activity index (SAI). This study shows that at 7 days W-GP and C-GP produced SAI of 84% and 87% at 7-days respectively. These values are more than the 75% of SAI’s requirements of ASTM C618. Both specimens have outperformed the control OPC mix at 28 days by producing SAI of 108.68% and 123.82% for GP-W and GP-C respectively.

Compressive strength development and durability properties of high volume slag and slag-fly ash blended concretes containing nano-CaCO3

This paper presents the effect of nano-CaCO3 (NC) on the compressive strengths and durability properties of high volume slag (HVS) and high volume slag-fly ash (HVS-FA) blended concretes. The study examined the improvement in early and later age compressive strengths and durability properties such as sorptivity, volume of permeable voids, rapid chloride penetration and drying shrinkage of HVS concrete containing 69% blast furnace slag (BFS) and HVS-FA concrete containing combined BFS and fly ash (FA) content of 69% due to the addition of 1% NC. Results show that the addition of 1% NC improved the compressive strengths of HVS and HVS-FA concretes significantly by 43% and 28%, respectively at 3 days compared to the control HVS and HVS-FA concretes without NC and exceeded the compressive strengths of control OPC concrete at later ages. It is also found that 1% NC inclusion reduced the water sorptivity of HVS and HVS-FA concretes reasonably after 28 days of curing and reduction is greater after 90 days of curing exhibited comparable water sorptivity to OPC concrete. Significant improvement is also observed in reducing the volume of permeable voids and controlling the drying shrinkage strain at early age as well as later ages of both HVS and HVS-FA concretes due to 1% NC inclusion. Outstanding resistance against chloride ion penetration is also observed in HVS and HVS-FA concretes due to addition of 1% NC to the very low level of chloride ion penetration according to ASTM standard. SEM and EDS analysis revealed a denser microstructure of paste and interfacial transition zone (ITZ) around aggregates.

Development of a cementless eco-binder as an alternative to traditional Portland cement in construction activities

In this research, the performance of a cementless eco-binder, a mixture of waste materials including slag, circulating fluidized bed combustion ash (CFA), and rice husk ash (RHA) was investigated, in which CFA acted as an activator. One hundred and twenty paste samples were prepared by using the RHA/(slag + RHA) ratios of 0, 15, 30, 45% while keeping a constant ratio of CFA/(slag + RHA) at 25%. The setting period, compressive strength, the ultrasonic pulse velocity (UPV), and drying shrinkage of paste samples were determined at the samples’ age of up to 91 days. In addition, the microstructures of all paste samples were also characterized by scanning electron microscopy (SEM). It was found that the use of cementless eco-binder significantly increased the setting times, lower compressive strength, drying shrinkage, and UPV values compared to the control OPC sample. The maximum 91-day-old compressive strength gained by the binary binder of slag and CFA (R00C25) was 90% of that of the control specimen. Incorporation of RHA with higher replacement levels up to 45% resulted in a significant decrease in compressive strength up to 50%. Moreover, the SEM analysis revealed that there was a large difference in the microstructures of the control and the cementless eco-binder samples, in which the main hydration products were C-S-H/C-A-S-H gels and ettringite (AFt) due to relatively high amount of SO3 and SiO2 in the CFA and RHA, respectively. Thus, it can be realized that the potential for the use of slag, CFA, and RHA as a sustainable cement-free binder is promising in the construction industry, especially for lower strength or no required early high strength structures.
 Keywords:
 cementless eco-binder; circulating fluidized bed combustion; rice husk ash; slag; microstructure; compressive strength; drying shrinkage; setting time; ultrasonic pulse velocity.

SUSTAINABILITY ASSESSMENT OF REINFORCED CONCRETE BEAM MIXES CONTAINING RECYCLED AGGREGATES AND INDUSTRIAL BY-PRODUCTS

ABSTRACTA vast amount of construction and demolition (C&D) wastes are generated in Western Australia (WA) of which a major portion goes to landfills. The diversion of C&D waste from landfills would be the single most significant opportunity for WA to improve its recovery performance. C&D waste materials have already been investigated for their appropriateness and use in pavement and concrete. This work is the continuation of the authors’ previous work involving further experimental tests to prove the structural suitability of a building’s structural member (i.e., beam) made of recycled aggregates and industrial by-products. The concrete mixes considered in this study are 100NA+100 OPC (Control), 100RA+100OPC, 50RA+50NA+90OPC+10SF and 50RA+50NA+60OPC+30FA+10SF. The Reinforced Concrete (RC) beam made of 50RA+50NA+60OPC+30FA+10SF concrete mix was found to be the only eco-efficient option. This option has reduced the level of environmental impacts in a cost-competitive manner. The use of this eco-efficient option could also provide new employment opportunities and significant improvements in terms of land and energy resources conservation and bio-diversity enhancement.

Potential of Orange Peel Ash as a Cement Replacement Material

The potential of Orange peel ash (OPA) as a cement replacement material was investigated with focus on the effect of OPA content on the physicomechnical properties such as consistency, setting times, soundness, compressive and flexural strengths of OPA-cement blend for cement replacement between 2.5-10% at 2.5% interval. The optimal calcination temperature and time of orange peel (OP) was achieved by calcining the OP at various temperature between (600 °C, 700 °C, 800 °C) and time (1 hr. and 2 hrs.) respectively. The chemical compositions of the various orange peel ashes were determined using X-ray fluorescence equipment and the optimal conditions was obtained at 600 °C and 2 hours. The consistency and setting time tests were conducted with a Vicat apparatus on the binary cement pastes in accordance to ASTM standards. Results indicated an increase in the water required for consistency as the OPA content was increased from 2.5-10 % which was attributed to the unburnt carbon content present in the ash. Similarly, a gradual increase in the cement replacement with OPA resulted in a prolonged setting time which was could be attributed to the diminution of the clinker content and the higher water requirement for normal consistence. The soundness of the OPA cement blend experienced an increase in free lime content as the OPA content rose from 2.5-10 %. Both compressive and flexural strengths were found to decrease as the OPA content was gradually increased whereas an increase in the strengths were observed as the curing days progressed. It was also observed that 5% cement replacement with OPA did not adversely affect the strength in comparison to the OPC control due to the pozzolanic reaction which resulted in the enhanced strengths especially at 28 days.

DURABILITY PROPERTIES OF TERNARY BLENDED FLOWABLE HIGH PERFORMANCE CONCRETE CONTAINING GROUND GRANULATED BLAST FURNACE SLAG AND PULVERIZED FUEL ASH

The use of ordinary Portland cement as the primary binder in concrete production resulted in the high carbon footprint of the concrete material which cause a great deal of environmental impacts over the years. The consumption of OPC is especially significant for high strength concrete, which require a very high cement content (more than 450 kg/m3). Hence, supplementary cementitious materials such as ground granulated blast furnace slag (GGBS) and pulverized fuel ash (PFA) were chosen as partial replacement materials of OPC for concrete production in the research due to their ease of availability from the steelmaking manufacturing sectors and coal-fired electricity power stations in the country. As the sustainability of concrete is also our main concern, the durability performance of flowable high performance concrete containing high volume of GGBS and PFA (50-80% replacement of OPC) has been studied in this research. Therefore, the durability properties of flowable high performance concrete had been assessed in term of air permeability, porosity, water absorption and capillary action. From the results of assessment, all ternary blended concrete mixes exhibited better durability performances than control OPC concrete at later ages due to formation of denser microstructure by pozzolanic reaction of GGBS and PFA. It is concluded that the mix proportion of flowable high performance concrete production with 60% replacement of OPC by GGBS and PFA has the optimum durability performances than OPC concrete.

Mechanical and Durability Properties of High Strength High Performance Concrete Incorporating Rice Husk Ash

Nowadays, more infrastructure projects require concrete to have a high durability in addition to high strength. High strength high performance concrete (HSHPC) was developed to solve those problems. The weaknesses of HSHPC are high cost of constituent material such as silica fume which is mostly used as supplementary cementitious material (SCM), high cement content at low w/b, low workability and the need of specific curing regime. This research utilized rice husk ash (RHA) as the local waste material as an alternative to silica fume (SF). Five mixes of OPC concrete, 10%, 15% and 20% partial cement replacement by RHA, and 10% partial cement replacement by SF were chosen. The water/cementitious ratio adopted was 0.25 and the total cementitious materials content was 550 kg/m3. The mixing method adopted was the two-step mixing method. In addition to the development of compressive strength, workability, modulus of elasticity and the residue of compressive strength of concrete experienced immerse in 5% solution of magnesium sulphate were also reported. The specimens were cured and tested at 1, 3, 7, 28 and 56 days. Results show that concrete incorporating rice husk ash as 10% partial cement replacement and crushed granite as coarse aggregate with maximum size of 19 mm can achieve compressive strength as high as 110 MPa at 28 days under water curing regime. The HSHPC incorporating 10% RHA showed better overall performance than the HSHPC containing 10% silica fume and the control OPC.

Use of Rice Husk Ash as Strength-Enhancing Additive in Lightweight Cementitious Composite Mortars

This paper investigates the properties of rice husk ash (RHA) produced by using a ferro-cement furnace. The effect of RHA percentage on lightweight composite mortar consistency, initial and final setting time, plastic and dry set density, flexural and compressive strength were investigated. Incorporation of RHA in lightweight mortar increased water demand. The effect of early (7 and 14 days) and long term curing ages (90 and 120 days) on the mechanical strength properties of lightweight composite mortars with RHA were also analysed. Mortar samples show strength reduction of 10.6% and 8.57% compared to the control mix at early curing ages of 7 and 14 days, respectively. RHA mortar gave excellent improvement in strength for 20% replacement (18.85% and 21.69% increment compared to the control mix at long term curing of 90 and 120 days), and up to 25% of cement by weight be valuably replaced with RHA without adversely affecting the strength. Increasing replacement ratio of RHA enhanced the strength of blended mortar compared to low utilization ratio of RHA and control OPC mixtures.

SkuBATCH - System for control of technological processes

The paper presents a SkuBATCh system for batch process control designed and implemented based on ISA-88 and ISA-95 standards. The multitier system is based on the .NET framework, using modern OPC UA protocol for communication. The system is used in the teaching laboratory and serves to teach students and to demonstrate the principles described in the standards.The paper describes both the way of implementation and potential use. It is a combination of modern technologies namely OPC UA and control by superior batch system. You can find the mapping of the procedural model to the PLC and the data flow. SkuBATCH is then tested on a virtual production model. This whole solution is then taught as an example of batch production.

Security Challenges in Control Network Protocols: A Survey

With the ongoing adoption of remotely communicating and interacting control systems harbored by critical infrastructures, the potential attack surface of such systems also increases drastically. Therefore, not only the need for standardized and manufacturer-agnostic control system communication protocols has grown, but also the requirement to protect those control systems' communication. There have already been numerous security analyses of different control system communication protocols; yet, these have not been combined with each other sufficiently, mainly due to three reasons: First, the life cycles of such protocols are usually much longer than those of other Internet and communication technologies, therefore legacy protocols are often not considered in current security analyses. Second, the usage of certain control system communication protocols is usually restricted to a particular infrastructure domain, which leads to an isolated view on them. Third, with the accelerating pace at which both control system communication protocols and threats against them develop, existing surveys are aging at an increased rate, making their re-investigation a necessity. In this paper, a comprehensive survey on the security of the most important control system communication protocols, namely Modbus, OPC UA, TASE.2, DNP3, IEC 60870-5-101, IEC 60870-5-104, and IEC 61850 is performed. To achieve comparability, a common test methodology based on attacks exploiting well-known control system protocol vulnerabilities is created for all protocols. In addition, the effectiveness of the related security standard IEC 62351 is analyzed by a pre- and post-IEC 62351 comparison.

Statistical analysis of time dependent variation of diffusion coefficient for various binary and ternary based concrete mixtures

The numerical modelling of chloride penetration into concrete requires sound description of input parameters. One of the crucial inputs is the diffusion coefficient of concrete. The concrete is heterogeneous material and its parameters depend on the level of maturity. Therefore, the objective of this work is to describe the time dependent variability of the diffusion coefficient of chlorides into concrete. Computation of the diffusion coefficient is based on the non-destructive testing of bulk electrical resistivity following ASTM C1760 standard and Nernst-Einstein relationship. The presented results show the variation of diffusion coefficient of control OPC mixture and 32 various binary and ternary concrete mixtures where the effect of prolonged aging is even more significant. Two possibilities of the time dependent diffusion coefficient probabilistic model based on coefficient variation (mean value and regression via linear approximation) are proposed. The quality of both approaches is evaluated using Root of Mean Squared Error approach. Overall, this study provides guidance to select proper statistical tool for the assessing the time dependent variation of diffusion coefficient.

Carbonation-Induced Mineralogical Changes in Coal Mining Waste Blended Cement Pastes and Their Influence on Mechanical and Microporosity Properties

The worldwide pursuit of new eco-efficient pozzolans is ongoing. Kaolinite-based waste is an eco-friendly source of recycled metakaolinite, a highly pozzolanic product. In this study, a blended cement paste containing 20% activated coal waste (ACW) was exposed to a 100% CO2 atmosphere at 65% RH for 7 days. The variations in its phase composition and strength were studied and compared to an OPC control. Both pastes were cured for 28 days prior to the carbonation test. Reaction kinetics were assessed using XRD, SEM/EDX, TG/DTG, FT-IR, Micro-Raman spectroscopy, pore solution pH and the cumulative carbonated fraction. The blended cement carbonated 68% faster than the control. While portlandite carbonation was the main reaction in both cements, decalcification was also observed (more intensely in the 20% ACW paste) in other hydraulic calcium phases (C-S-H gel, monocarboaluminate (C4AcH12), ettringite and tetracalcium aluminate (C4AH13). The end product of this reaction was calcium carbonate, mainly in the form of calcite, although traces of aragonite and amorphous carbonate were also detected. Compressive strength values rose with accelerated carbonation time and pore size reduction in both cement pastes.

Propuesta de un estimador de fallas usando fracciones coprimas

Los sistemas de detección, diagnóstico y aislamiento de fallas (FDDI), generan señales (residuos) que contienen detalles de la falla. La estimación de estado es un procedimiento común para la generación de residuos cuando se usa redundancia analítica. En este artículo, la hipótesis propuesta es usar la teoría de fracciones coprimas para generar un estimador de salida; este compite con algunos estimadores clásicos como Kalman, Luemberger, Lyapunov y Jordan, con ellos se analizan los tiempos de ejecución y tasas de precisión en la estimación usando el error medio cuadrático en presencia de fallas aditivas. Los resultados son validados sobre un sistema FDDI implementado sobre un tanque de homogenización en lazo cerrado usando el estándar para control de procesos OPC y simulando físicamente una falla en el sensor RTD de salida

Electrically driven chloride ion transport in blended binder concretes: Insights from experiments and numerical simulations

Chloride ion transport driven by electrical potential gradients is discussed in concretes wherein OPC is partially replaced by limestone or a combination of limestone and fly ash/metakaolin at replacement levels of 20% or 35% (volume-basis). The ternary formulations demonstrate non-steady state Cl− migration (NSSM) coefficients that are comparable to or lower than those of the control OPC concretes, with metakaolin blends showing markedly better performance. A pore structure factor extracted through electrical conductivity measurements before the NSSM test is correlated with Cl− penetration depths after the migration test. The transport of all ionic species (Cl−, OH−, Na+, K+) is modeled using an explicit finite element framework via the coupled Poisson–Nernst–Planck (PNP) equation with suitable consideration of: (a) concentration (depth)-dependent diffusion coefficients, (b) pore-structure factor, and (c) Cl− binding. With informed inputs of material properties, the simulations are able to reliably capture Cl− penetration behaviors in plain and blended binder formulations.

STRESS - STRAIN BEHAVIOUR OF SLAG CEMENT CONCRETE

The paper describes the results of test carried out on OPC concrete and slag cement concretes. Ten blended slag-cement concretes, made with typical slags from four countries (United Kingdom, Belgium, South Africa and Japan), are compared with a control OPC concrete. The slags replaced 30 to 70% of cement by mass. The bobbin shaped specimens were used in the direct tension test and 300x150 mm dia. cylindrical specimens were used in the axial and lateral strain tests. Poisson's ratio in compression was determined as the ratio of the lateral to axial strain at the ages of 14 and 84 days. Concretes at the age 84 days exhibits more linearity than at the age of 14 days and slag concrete becomes more brittle when stored in the dry environment. There was no difference between the Poisson's ratio of slag and OPC concretes.

Study on Automatic Active Power Control System of Wind Farms

Based on a "wind power remote monitoring system" project, this paper focus on the modeling and simulation of the wind power variant pitch control system, and also the wind generator active power control OPC CLIENT interface programming. Using the VC++ language and MFC, OPC CLIENT interface was designed for the start-stop control of fan and the active power control of wind farms, which enables the wind farm to accurate and rapid response of the wind power grid load instruction of automatic generation control (AGC). Further, based on the MATLAB/SIMULINK platform, we analyzed the variable pitch control system of the variable pitch wind turbine by modeling and simulation with the Denmark's VESTAS V80-2000 (2MV).

Characteristics of blended cements containing nano-silica

The aim of the present work is to evaluate the effect of nano-silica (NS) on physico-chemical, compressive and flexural strengths of OPC-granulated slag blended cement pastes and mortars. Different mixes were made with various amounts of NS, OPC and granulated blast-furnace slag (GBFS) and hydrated for 3, 7, 28 and 90days. The hydration behavior was followed by estimation of free lime (FL) and combined water content at different curing ages. The required water for standard consistency, setting times and compressive strength was also determined. The results obtained were confirmed by XRD, DTA, IR and SEM techniques. The required water for standard consistency and setting times increases with NS content due to the presence of 1% of superplasticizer. As the NS content increases the values of both FL and pH decrease. The compressive and flexural strengths of cement mortars containing NS are higher than those of control OPC–GBFS mix (M3). As the NS content increases above 4mass% NS, compressive and flexural strengths of OPC–GBFS–NS blends decrease but still more than those of the control samples (M3). The results of XRD, DSC, IR and SEM examinations are in good harmony with each other and with chemical analyses. The composite OPC–GBFS–NS cements containing 45mass% of GBFS and 3–4mass% of NS possess the highest improvement of mechanical properties, hydration kinetics and microstructure of hardened cement pastes and mortars.

Characterization on a cementitious material composed of red mud and coal industry byproducts

This research was to investigate the possibility of incorporating red mud and coal industry byproducts as the raw material for producing cementitious material. Systematic mechanical strength tests were conducted to evaluate the performance of this cementitious material. Results showed that the designed red mud–coal industry byproducts based cementitious material had higher strength in the middle to late curing age (47.5MPa in 180days and 48.7MPa in 360days) than the OPC control group. The series of durability tests indicated that the cementitious material met with the ASTM requirement. Moreover, the toxicity characteristic leaching tests demonstrated that this cementitious material had good stabilization/solidification ability to bind the heavy metal in the red mud as raw material. Microanalysis revealed that the amorphous gel was the dominant structure of the material at the middle to late curing age, which possibly played a significant role on the heavy metal binding properties through the polymerization during the hydration process of this cementitious material. In essence, this designed red mud–coal industry byproducts based cementitious material not only meet with the physical and mechanical requirements of the ASTM standards, but also meet with the EPA regulation on the environmental heavy metal leaching limitation. This proves the designed material can possibly be used as a clean technology to recycle the red mud from alumina industries and byproduct from coal industries.