1. Introduction

2. Materials and methods

3. Results and discussion

4. Conclusions

Abstract

This study aims at investigating the possibility of using smectite clay waste, generated during the oil bleaching process as an additive for Portland cement. The smectite clay waste consists of montmorillonite, quartz, anorthite, calcium sulfate, and amorphous phase. For the regeneration of this waste, the extraction with hexane and thermal method were chosen. The results showed that the extraction of smectite clay waste with hexane significantly increased the pozzolanic activity of this waste; however, the extracted additive prolonged the induction period of Portland cement hydration, slowing down initial cement hydration, and reduced the compressive strength of Portland cement samples.

The thermal activation method achieves the best results by calcining smectite clay waste at 600 °C. The calcined additive indicated the strong pozzolanic activity. However, this phenomenon is associated with the formation of the amorphous phase by activating the smectite clay with the sulfuric acid rather than the degradation of the clay minerals during the combustion. The calcined smectite clay waste (CSCW) accelerates the hydration of calcium silicates in the second period of the exothermic reaction. The results of the investigation showed that in samples with the CSCW additive proceed the intense pozzolanic reaction, which can be clearly identified after 28 days of hydration. Up to 15 wt% of the Portland cement can be replaced by the smectite clay waste additive calcined at 600 °C without reducing the compressive strength of Portland cement samples.

Introduction

Nowadays one of the most current issues is the environmental pollution caused by industrial waste, which is being produced by large-scale production in various industries. Only a small part of the industrial waste is recycled and its application in other industries is highly important. Various studies have shown [1-5] that some industrial waste can be used by replacing a part of the clinker in cements or a part of the cement in concrete. In this case, when the waste is used as an additive for 32 binding materials, not only the pollution issue is solved but also the cost of Portland cement or concrete is decreased.

Oil bleaching is one of the processes applied in oil industry during which the impurities that add colour to the oil are removed and oil is purified from carotenoids, peroxides, chlorophyll, etc. Oils are bleached using a powdered, surfactant materials, which are called bleaching earths. Bleaching earths can composed of up to different types of clay minerals, such as smectite, bentonite, attapulgite and sepiolite. The bleaching process is carried out under vacuum, with temperature in the range of 80-120 °C and contact time ranging from 20-40 min. The dosage of bleaching earth usual is 0.5-2 % by weight. After bleaching, the mix of clay and oil are separated by the vacuum filtration into two phases: oil and clay waste. As a consequence, the oily clay becomes hardly recycled waste. Market demand for activated bleaching earth was predicted to rise to ~9M/year tones until 2022, therefore, the amount of waste produced through the edible oil bleaching process, is considerable [6].

To reduce environmental pollution induced by the production of Portland cement and sequestrate greenhouse gas, a novel approach was developed to manufacture nano-calcium carbonate (nano-CaCO3) suspension by upcycling carbon dioxide. The influence of this nano-CaCO3 suspension on basic performances of Portland cement paste was experimentally evaluated and related mechanisms were demonstrated by isothermal heat conduction calorimeter (TAM Air), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetry-differential thermal analysis (TG-DTA), mercury intrusion porosimeter (MIP), scanning electron microscope (SEM) and transmission electron microscope (TEM) measurements. Experimental results showed that the manufactured CaCO3 presented spherical and cubic shapes with size of 20 to 50 nm. This CO2 upcycling method can improve compressive strength of cement paste by 5.8~9.9% at ages of 3 to 56 days and significantly reduce the initial and final setting times. The introduction of CO2 in form of nano-CaCO3 accelerated the early age hydration of Portland cement and refined the pore structure. Around 0.4~2.4 kg of CO2 can be recycled by every ton of Portland cement while the usage efficiency 22 of cement was evidently improved. Therefore, both capture and solidification of carbon dioxide and 23 carbon footprint reduction of cement industry can be simultaneously achieved by this technology.

Introduction

It is well known that Portland cements (PC) is one of the most widely used materials for construction of buildings and other infrastructures (Biernacki et al., 2017˗Schneider et al., 2011; Shi et 29 al., 2011). The reported worldwide production of Portland cements reached as high as 4.6 billion tons in 2016, of which more than 60% was contributed by China (CEMBUREAU, 2016). The PC production is a typical CO2 release and energy consumption process, being responsible for nearly 9% of anthropogenic CO2 emission and accounts for approximately 3% of the global energy use (Shi et al., 2011). Generally speaking, around one ton of CO2 is discharged by the production of every ton PC (Hemalatha and Ramaswamy, 2017) and such CO2 emission is attributable to two aspects. On the one hand, CO2 is a by-product from the calcination of limestone to create reactive calcium silicates (Shi et al., 2011; Vance et al., 2015); on the other hand, the combustion of fossil fuel required for clinkering raw materials (clay and limestone) at 1450 ć also releases a great deal of CO2 (Vance et al., 2015). Therefore, the carbon impact of Portland cement industry has attracted increasing attentions and many efforts have been carried out to address a lower-carbon or greener production of cements (Bourtsalas et al., 2018; Benhelal et al., 2018; Carvalho et al., 2017). The cement concrete industry worked with the International Energy Agency to outline the ambitious effort to decrease industrial emissions to 50% below levels of 2006 till 2050 (Monkman and Macdonald, 2017). It is in accordance with the “blue map scenario” (International Energy Agency, 2008). There are four suggested approaches for achieving this target (Monkman and Macdonald, 2017): to improve the energy efficiency of cement kilns, to increase the usage of low-carbon supplementary 46 cementitious materials (SCMs) to replace clinker, to utilize alternative raw materials and/or fuels for manufacture of Portland clinker and to capture or sequestrate CO2.

The waste problem is a problem faced throughout the world. This research aims to save the environment with on the utilization of recycling waste materials that do not contribute much in people’s lives over the years. Organic cement is an alternative cement besides portland cement made from organic waste recyled and substitution of mediteran soil. The research is oriented to chemical compounds, compressive strength, and tensile strength testings of concrete by using organic and portland cements. Age of concrete in the research are 3, 4, 14, 21, and 28 days old. Result for compressive test of cylinder concrete with organic cement, it obtained 6.10 MPa while the cylincer concrete with portland cement, it obtained 20.22 MPa. For tensile strength test of cylinder concrete with organic cement on 28-days-old concrete reached 1.09 MPa and those with portland cement reached 2.01 MPa. From the physical test result, it obtained the density of organic cement is 3.01 gr / ml, while for the density of portland cement is 3.16 gr / ml. From the analysis of organic cement chemical compounds through laboratory testing methods result, it found indications that resemble portland cement chemical compounds that are CaO;65,36%, SiO₂; 18,84%, Al₂O₃; 6,33%, Fe₂O₃; 2,29%, SO₃ ; 3,64%, MgO; 1,35%, C₃S; 66,72%, C₂S; 3,98%, C₃A; 12,9%, and C4Af; 6,97%.

Introduction

Currently, the waste problem is a problem faced throughout the world. Gradually, the high volume of waste has a negative impact on the environment. Handling of waste management is necessary because of the huge negative impact that can be generated. The waste problem seems not a simple matter, as long as there is human life then the problem will always arise. Urban waste management in Indonesia is a real problem as population growth has an impact on increasing the amount of waste and the occurrence of aesthetic degradation problems around landfills that have potential to cause social conflict with surrounding communities. [1]. Along with economic growth, per capita garbage production will continue to increase so it can be predicted in 2030 will reach 1,2 kg / capita / day for urban areas and 0,55 kg / person / day for rural areas. In Indonesia, organic waste is a major component of waste. The proportion of organic waste is between 34-70% which is 20-30% higher than most countries in Europe [2]. The high growth of waste volume coincides with high population growth rate. Therefore, the current waste problem can be said to be a world problem. In addition, with good handling and good waste management, environmental savings have been made.Handling of organic waste through the combustion process with the furnace at 700° C to ashes will contain elements of 69.7% CaCo3, 12.1% KCl; 3% SiO2, 8.1% Fe and 3% Al2, while shellfish ash contains 100% CaCo3 [3]. Therefore, in dealing with it, it is deemed necessary to find the best solution to resolve current waste problems. This research aims to save the environment with emphasis on the utilization-oriented form of recycling waste materials that do not contribute much in people’s lives over the years.This research is a renewable research to obtain alternative building materials, especially alternative cement in addition to portland cement which has been used in public life. The increase in cement growth is still influenced by the high level of private sector development and the high demand for housing for the community [4]. The increasing demand for housing and infrastructure automatically demands the need for building materials that are also increasing.The need for building materials must be overcome with the use and discovery of building materials that can provide an alternative [5]. Organic cement is the newest alternative cement in addition to portland cement made through organic waste recycling systems and by substitution of mediteran soil [6]. The development of the use of alternative sources for the manufacture of cement has also been developed by Japan which has been producing eco-cement made from city ash waste through combustion in lieu of some of the main raw materials containing 50% of cement raw materials such as sewage sludge [7]. To create Eco-Cement CSA Clinker,the appropriate starting raw material needs to be burned at a maximum temperature of 1200-1300 ° C. Reuse of waste materials in the form of phosphogypsum will reduce the temperature and time of the combustion process. Large scale eco-cement making can be done in conventional furnace used for portland cement and produce chemical cement mineralization of C = CaO, A = Al2O3, S = SiO2, s = SO3, F = Fe2O3, M = MgO, Ye’elimite 4CaO, 3Al2O3, SO3 and C4A3s [8]. Mediteran soil is a soil formed from weathering of sedimentary rock and limestone. This type of soil contains a considerable amount of carbonate and other compounds of iron, water, aluminum, and some other organic materials [9].

This study reports on the effect of dry ice on the hydration and hardening behavior of Portland cement. Dry ice was directly added to fresh Portland cement paste, with its dosage fixed at 0 wt%, 0.3 wt%, 0.6 wt %, 0.9 wt%, 1.2 wt% and 1.5 wt%. Results showed that dry ice had little effect on the standard consistency and setting time of cement paste when its dosage was less than 0.9 wt%, but otherwise the standard consistency as well as the setting time was increased. The compressive strength of the paste at 7 days increased slightly when the dosage of dry ice was less than 0.9 wt%, but the compressive strength was reduced with the addition of 0.9 wt% to 1.5 wt% dry ice. For the compressive strength at 28 days, the cement paste with 0.6 wt% dry ice showed the greatest value, being increased by 30.9% compared to the control cement paste, and the compressive strength of the samples with dry ice was all higher than that of the control. In addition, hydration heat, XRD, DTA-TG and SEM results showed that the incorporation of dry ice retarded the early hydration of Portland cement, improved its later hydration, and optimized the hardened structure of the cement paste. These results can provide a reference for the future application of dry ice in Portland cement-based materials.

Introduction

In order to reduce environment impact of CO2, a number of measures have been taken, such as reducing CO2 emission [1,2] and sequestrating CO2 by using cementitious materials [3]. However, the construction industry annually consumes 4.3 billion tons of ordinary Portland cement (OPC) for making concrete, resulting in a great amount of CO2 emission that accounts for around 7% of global CO2 emissions. To reduce carbon footprint of cement industry, a number of studies focused on developing low-carbon cement [4–7]. In addition, other relevant research has been performed, which included CO2 curing [8–13], CO2 strengthening recycled aggregates [14–19], as well as the transformation of carbon dioxide to carbonate as chemical additives [20–22]. X.Y. Pan [11]studied the strength and permeability of CO2 surface treatment on oneday age of cement mortar. After 24 h of CO2 treatment, the results showed that the compressive strength was increased slightly, the impermeability of cementing material was improved, while water absorption was reduced by 15–30%. KOU [23] studied the effect of carbonization on recycled aggregates, and their results showed that CO2 curing increased the physical properties of recycled aggregates: the longer the curing time, the better the degree of carbonation and the higher the quality of aggregate. W. Kunther [24] investigated the effect of bicarbonate ions on the deterioration of mortar bars in sulphate solutions and found that the presence of bicarbonate ions significantly reduced mortar swelling. J.G. Jang [25] studied the effect of sodium bicarbonate on the performance of cement slurry, and they found that the addition of NaHCO3 caused the internal carbonation of cement slurry, resulting in the consumption of Ca(OH)2. Besides, the compressive strength was increased with the addition of 5% NaHCO3; however, the strength degraded for higher concentrations. Rodger [26] found that Li2CO3 accelerated the early hydration rate of sulphoaluminate cement. Other studies [27–29] found that lithium carbonate significantly shortened the setting time of sulphoaluminate cement, and improved its early compressive strength and flexural strength. Although there have been a number of studies on the influence of CO2 curing or carbonate salts on hydration and hardening of Portland cement, little research has been carried out on how dry ice, as an alternative form of CO2, affects the process of Portland cement hydration. This study investigates the effect of dry ice on the hydration kinetics, compressive strength, chemical compositions, and microstructure of Portland cement paste.

In recent decades, the new progress in the preparation and application of cement concrete materials has benefited from the development and effective application of chemical admixtures. At present, the chemical admixture has become a cement-based material, which is an important regulatory component or modification method. Addition of a small amount of admixture, especially organic admixture, can effectively adjust the performance of cement-based materials, such as improving work performance or rheology, speeding up or delaying the hydration rate and coagulation time, and improving the physical and mechanical properties and durability of materials [1–5]. 0e performance of the admixture has an important relationship with the functional groups in its molecule. At present, the functional groups or functional groups contained in the organic admixtures used in the concrete materials mainly include hydroxyl groups, carboxyl groups, amino groups, and sulfonic acid groups [6–9]. In addition, it should be noted that the ester groups and phosphonate groups are also important functional groups. On the one hand, the ester-based organics can be used as antifoaming agents. On the other hand, many studies have reported that the esterification modification method is an important means for improving or modifying the performance of hydroxyl- or carboxyl-containing admixtures [1, 10]. In view of the low grinding ability of triethanolamine in cement fine-grinding stage and the disadvantage on the late strength growth of cement, it is studied that the triethanolamine modified by carboxylic acid has a better effect on the grinding and dispersing, and the strength of cement at early and late stage has a significant growth [1, 11, 12]. 0e molecular structure and dosages of the admixtures play an important role in the hydration of cement, such as shorting the hydration time, reducing the hydration heat, and improving the mechanical strength [13–16]. However, it is not clear at present that the increase in the performance of the admixture is caused by changes in the molecular structure or by the action of the newly introduced ester functional groups after modification. Also, there is no research at this point. In order to explore whether the ester groups have an important effect on the hydration and hardening of cement, five common organic compounds, ethyl acetate, dimethyl oxalate, glyceryl triacetate, trimethyl phosphate, and triethanolamine borate, were selected for comparative experiments in this study. 0e effects of five kinds of organic compounds on hydration heat, hydration degree, setting time, mechanical properties, microstructure, and pore structure of hardened slurry were studied in this study.

The quality of Portland cement significantly influences the performance of concrete [1–3]. Existing standards do not specify the shelf life of Portland cement. However, invalidation of Portland cement is likely to occur due to the influence of environmental conditions. While the compressive strength of Portland cement is 5 MPa lower than the standard compressive strength, mechanical performance of cement will not be up to standard [4]. As a result, the compressive strength of concrete by using invalidated cement cannot be guaranteed, and quality-related safety accidents could frequently occur [5–7]. Therefore, invalidation characterization of Portland cement is necessary. In the research on the invalidation characterization of Portland cement, visual observation and strength test methods have been mainly used. The visual observation method is used to detect severe caking on cement surface according to a phenomenological empirical experience. Chen [8] classified agglomeration during cement storage classified into three categories: warehouse caking, pile caking and bag caking. Furthermore, they provided suggestions for preventing agglomeration of Portland cement by controlling the content of C3A in the clinker. However, no quantitative parameters of the corresponding relationship between the content of C3A and invalidation of Portland cement were presented. The compressive strength test method is used to determine cement invalidation by testing the compressive strength of 28-day cement mortar specimens and examining whether the strength of the cement meets the specifications. However, this method exhibits strong hysteresis. Zou [9] utilised energy-dispersive spectrometry (EDS) to determine the types and contents of elements in mineral constituents in montmorillonite powder to determine which varieties of montmorillonite drugs fail. He [10] utilised scanning electron microscopy (SEM), EDS and X-ray diffraction to analyse and characterize the corrosion invalidation products on the steel structures of a substation. The results showed that the corrosion invalidation of steel structures was caused by the electrochemical corrosion of carbon steel in humid atmosphere. Inspired by the above two research in different fields and so on, we think that the microscopic detection is very useful for the quantitative invalidation characterization of Portland Cement. Therefore, a quick and accurate method of quantitative invalidation characterization of Portland cement was proposed in this study by using microscopic analysis methods, such as BSE and EDS, to investigate the microstructure’s morphological change and the invalidation essence of Portland cement.

Cement industry is faced with serious environmental problems. The production of Portland cement (PC) in the cement industry not only consumes raw materials and large amounts of energy, but also as one of the primary industrial producers of carbon dioxide, contributes to the greenhouse effect and causes acid rain. Actually, this industry generates greenhouse gases (GHGs) both directly through the emission of CO2 when clinker is produced and also through the consumption of energy [1-4]. On the other hand, the severity of environmental regulations is enhanced progressively and has forced the industries to put in a great effort to reduce their pollutants [4]. One of the interesting approaches for reducing environmental problems and also gaining technological and economic advantages is the increasing usage of industrial byproducts and wastes [1-6]. Among the industrial wastes, only slags have latent cementing property and have been converted to an important research area [5, 7, 8]. In fact, the production of slag cements and slag-blended Portland cements results in resource conservation, reducing energy consumption and minimizing emission of GHGs, especially CO2 [2]. Blast furnace slag (BFS) as one of the industrial solid wastes is formed in a molten state simultaneously with iron in a blast furnace. The chemical composition of the slag is originated from silicate and oxide components of the raw materials used in the smelter feed [9]. The slag exhibits primarily latent hydraulic activity, but may show some pozzolanic character as well. Nevertheless, BFS adversely affects the early-age strength of PC when used at high replacement levels [10] and as a supplementary cementing material, it is necessary to tailor its reactivity by auxiliary activation techniques [10-12] such as thermal, chemical, and mechanical as the most common activation techniques [11, 12]. Thermal activation or curing at elevated temperatures can improve strength development [12], but at the same time may decrease the ultimate strength [13]. Mechanical activation results from compound effects of particle fracture and other bulk and surface physicochemical changes [14, 15], dislocations and other defects induced by the milling [14, 16]. Mechanical activation of solid dispersed materials leads to accumulation of mechanical energy that is used for enhancement of the specific surface energy of a dispersed material [17, 18]. In mechanical activation, physicochemical properties of solid materials are varied during grinding process [16, 17]. Chemical activation refers to the use of some chemicals to impart cementing properties and/or to activate latent hydraulic properties [11, 18]. There are two types of alkali-activation, including (1) activation with strong alkaline activators that are suitable both for imparting cementing properties to aluminosilicate materials exhibiting no cementing properties and activating industrial slags with latent hydraulic properties, and (2) activation with mild alkaline activators that are applicable only for industrial slags exhibiting some cementing properties [19, 20].

One of the major priorities in cement industry is to find materials that may be used as a clinker replacement and which could help in reducing energy consumption and CO2 emissions during cement production [1]. Special attention is paid to the replacement of a part of ordinary Portland cement with various industrial mineral wastes [2,3]. The fine additives used in cement systems are classified into reactive and inert substances [4]. Reactive additives can chemically react with Portland cement hydrates (as a pozzolanic reaction), while inert additives in normal processing conditions fill up the void spaces remaining between the coarser particles and contribute to the increase of the compressive strength without any chemical reaction [4,5]. The addition of pozzolans to Portland cement increases its mechanical strength and durability compared with the blank paste because of the interface reinforcement [6], whereas the microfiller effect depends mainly on the shape and size of the particles, particle size distribution, and specific surface area [7]. Research of economic binders through the use of industrial byproducts (blast furnace slag, silica fume, fly-ashes, rice husk ashes, and other materials) is a major concern in reducing the deficit recorded during the manufacture of Portland cement [8]. A new source of an additive for Portland cement could be found in a waste product from mineral wool industries. The term “mineral wool” is a general name for fibre materials that are formed by spinning or drawing molten minerals. The chemical composition of these minerals mainly consists of SiO2, Al2O3, CaO, and MgO, whereas other oxides are considered as impurities [9]. During the mineral wool production process, the waste materials such as fibre waste and cupola dust form. On the one hand, mineral wool fibre waste can be recycled and returned to the production line, but cupola dust is usually sent to the waste dump. On the other hand, rock wool fibre waste can be used as a suitable substitute for coarse and fine aggregates, saving on the cost of natural aggregates and minimising the environmental impact of solid waste disposal [10]. Some researchers [10] also note that the composition of rock wool fibre waste is similar to other pozzolana materials such as fly ash, ground granulated blast-furnace slag (GGBS), and silica fume. The reactive additives cause a compaction of the matrix and interface transition zone because the particles of pozzolanic materials fill the void space between the larger grains, which is otherwise occupied by water, and, with time, they react chemically to produce additional hydrates [11,12]. It has been found that rock wool wastes can act as either a cementitious material or an inert filler in cement-based composites, depending on the particle size. The dense structure of cementbased composite, achieved by the filling effect of pozzolanic product, improves the compressive strength, splitting tensile strength, abrasion resistance, absorption, resistance to potential alkali reactivity, and resistivity [5,10]. In addition, it was pointed out [13] that 10e40 wt% of mineral wool fibre waste additive reduced porosity and changed the microstructure of the cement-based composites. These effects impair chloride ion and other ion penetration/mobility. However, there has been little discussion on the use of other mineral wool production process wastes such as cupola dust. This waste is accumulated in the filters for air coming out of the cupola and comprised of raw materials, additives, and melted particles mixture. Thus, cupola dust is very dispersive, with strong sorption properties [14,15]. It was reported [16] that the cupola dust additive, through its grading and chemical composition, reduces significantly the cement paste spreadability. Moreover, it was found that this additive had an influence on the hydration process of Portland cement and increased the early strength of hardened cement paste [16]. The aim of this work was to determine the possibility of using dust collected in filters, during the production of mineral wool, as an additive for the Portland cement.

مقاله سال 2016

افزودن ضایعات فولاد به شکل سرباره ها یا گرد به سیمان، برای محیط زیست مفید است،زیرا ضایعات میتوانند به این طریق از حرکت بایستند و به این ترتیب، آلودگی آبها، کاهش می یابد. در این مقاله، نمونه های سیمان پرتلند مبتی بر خمیر و ملات با wt% 70.0 گرد فولاد مورد بررسی قرار گرفت. از آنجاییکه معلوم است، برای یک تن سیمان پرتلند ساخته شده ، 900 کیلوگرم CO2، به محیط منتشر میشود، افزودن ضایعات فولاد به سیمان، بسیار مفید است. به علاوه، چون گرد فولاد، میزان سیمان لازم در بتن را کاهش میدهد، آن هزینه ی نهایی بتن را به طور عمده ای کاهش میدهد. به علاوه، فراوری تولید، کاملا در دمای اتاق اجرا شد؛ لذا، اثر منفی سیمان در محیط، کاهش می یابد.

میکروسکوپی الکترون پویشی و توصیف پراش پرتوی ایکس، برای بررسی میکروساختار نمونه ها اجرا شد. به علاوه، تراکم، فشردگی و تستهای جدول جریان، روی همه ی نمونه ها انجام شد. تستهای وابسته به گرما- ثقل سنجی برای تحلیل پایداری گرمایی ضایعات انجام شد. اثر قطعات خطرناک احتمالی این ضایعات در آب، از طریق تستهای قابلیت شسته شدن تحلیل شد. برای کل نمونه ها، تاب فشردگی در طیف 73 تا Mpa 2.5 بودند. پایین ترین مقدار تاب فشردگی متناظر با wt% 70 ضایعات بود. نتایج راه حل استفاده از این ضایعات را به عنوان افزونه یا هم آمیزه در سیمان و بتن نشان میدهد و به این صورت به عنوان روشی برای کاهش خمیر سیمان در ساختمانها و زیرساخت ها محسوب میشود.