Sulfate Resistance Of Cements Research Articles

Mechanical properties of hardened concrete in hot and dry climate

Concrete is the most popular material in construction industry. Recycling of waste and their application in the construction industry are the main purpose in the world economy. The concrete working in dry and hot climate are exposed to high temperatures in the summer. The temperature can increase up to 50 °C while the relative humidity drops to 10-15% and lower. Climatic conditions lead to decrease the performance properties (strength and modulus of elasticity). The basic tasks of region with dry and hot climate are improve resistance and efficiency of concrete. An extreme daily change in temperature, low humidity, soil salinity are the main cause of erosion of concrete. One of the way of optimizing of cracking resistance of the concrete is to increase the amount of cementitious components. The dependencies of experiment with similar climatic conditions based on sulfate resistant cement were conducted. The results of experiment show that the optimal content of materials in concrete included 530 kg of cement; 833 kg of quartz sand; 873 kg of coarse aggregate; 1.5 liters of plasticizer and 176 liters of water. The designed mixture had the following characteristics: the density 2414 kg/m3, the compressive strength in 28-day at the range of 47 MPa, water permeability - W4, with water cement ratio equal to 0.34.

Performance Testing of Hydraulic Cements: Measuring Sulfate Resistance

The sulfate resistance of cements used in the construction industry is traditionally assessed by measuring the expansion of a prism of 280 mm (11inch) length and 25 mm (1 inch) square cross section immersed in a sodium sulfate solution for at least one year. The duration of the experiment limits this test from being used as a performance-based determination of innovative mixtures of cementitious materials. In response to the need for a more rapid test protocol, the National Institute of Standards and Technology (NIST) has developed a new test method that measures the expansion of smaller bars (10 mm × 10 mm × 60 mm) made with neat cement paste. With these bars, similar expansion is achieved in less than 3 months, reducing the test duration by a factor of at least 4. This accelerated test method provides more rapid results consistent with the traditional test procedure, allowing for a shorter decision time and the screening of more materials.

X-ray CT monitoring of macro void development in mortars exposed to sulfate attack

This study reports the results of nondestructive monitoring of macro void developments in mortars manufactured with both ordinary Portland cement and sulfate resistant cement. Two types of curing were utilized; tap water curing and another curing environment that contains 5% Na2(SO4) solution. Being the primary objective of this study, macro void developments of the mortar specimens were monitored by X-ray Medical Computerized Tomography. Compressive strength tests and water absorption tests were conducted on specimens that were kept in both curing environments for a duration of 560 days. Data analyses yielded consistent results among the three tests used in this experimental study. Macro void ratios of mortars decreased at the beginning of experiments for a certain period; afterwards, macro void ratios increased. The objective of this study was accomplished as anticipated since X-CT image analysis was able to nondestructively monitor macro void development process in cement mortars.

Corrosion of cement pastes made of CEM I and CEM III/A caused by a saturated water solution of ammonium chloride after 4 and 25 days of aggressive immersion

One of the most common causes of the decay of concrete structures is contact with aggressive chemical compounds. Fluids containing chlorides and ammonium ions behave aggressively toward reinforced concrete in many environmental engineering structures. Therefore, the highest level of safety should be preserved in the case of industrial sewage treatment plant facilities, which also aim to protect the environment against pollutants.An accelerated test of the degradation of hydrated cement paste, as the most reactive component of concrete, was conducted. Sulfate resistant cement CEM I, slag cement CEM III/A and corrosive saturated ammonium chloride water solution were used. Investigation after 4 and 25 days of immersion found that portlandite dissolution triggered an increase in porosity. Thaumasite crystallized following ettringite dissolution. Another intermediate phase was Friedel’s salt. The final products of cement paste corrosion were found to be gypsum, calcite and vaterite. Porosity was higher in the case of CEM III/A. Chloride ion concentrations and porosity were not the highest in the surface areas, which were in the direct contact with an aggressive solution. Nitrogen crystalline phases were not found.

Development and Testing of Low-Energy-Intensive Technology of Receiving Sulphate-Resistant and Road Portlandcement

The article presents the obtaining results of clinkers of sulfate resistant and road cement during the production tests process. The usage of man-made wastes such as lead slag, coal mining waste as well as clay component and additives. X-ray, chemical analyzes of starting materials, clinkers and obtained cements were carried out. The regularities of charge compositions, saturation coefficient, modules, burning regimes on chemical and mineralogical composition and quality of clinkers and cements, improvement of rotary kiln operation, reduction of greenhouse gas emissions and fuel consumption are established. Various methods of analysis were used, calculations of raw mixtures composition were carried out according to the program "Shikhta" (designed to calculate the raw mix and the mineralogical composition of the clinker for the production of Portland cement. The program was developed in the V.G. Shukhov Belgorod State Technical University, Russia) and "Calculation of raw mixtures or CRM" (designed to calculate the raw mix of clinker. The program was developed in the M. Auezov South-Kazakhstan State University, Kazakhstan). The strength of factory and experimental cements was tested after 3, 7 and 28 days and after steaming.

Study on mechanism of chemical sulfate attack on reinforced concrete structures

This paper studies four different cementitious materials including ordinary Portland cement paste and cement fly ash in closed environment based on previous study on characteristics of carbon sulphosilicate formation in single sulfate solution. As test paste, cement limestone paste and sulfate-resistant cement paste were put in a mixed solution of sodium sulfate and magnesium sulfate, the results of which show that solution pH value changes with time and the products change with pH values. Finally, the attack mechanism of carbon and sulfite in the embedded concrete is analyzed based on results of the concrete failure test.

Leaching of Ca, Si, Fe and Al from concretes, based on sulphate resistant cement, due to bacterial attack - a correlation study

Investigation of biological corrosion of concrete requires that composition of material, surface and aggressive environment have to be taken into account. Sulphate resisting cement, as one of the resistivity improving factors, was used for preparation of concrete samples studied in this experiment. Dependences of leached-out quantities of selected ions regarding bacterial versus non-bacterial environments were investigated and evaluated using correlation analysis. Leaching trends of calcium, silicon and aluminium strongly depends on the aggressiveness of medium which are the samples exposed to. A weak correlation was found for the leaching trends of aluminium and iron in both bacterial and non-bacterial media.

Correlation Analysis between Different Types of Corrosion of Concrete Containing Sulfate Resisting Cement

Utilization of pozzolanic materials (fly ash, slag, zeolite, metakaolin, microsilica and more) in the manufacturing of cement and concrete has increased considerably over the last decades. Another option is to use concrete containing sulfate resisting cement. This could help minimize the harmful impacts on concrete exposed to an aggressive environment. The issue of the deteriorative impact of the three types of concrete corrosion (acidic, sulfate and leaching) investigated using correlation analysis is presented in the paper. Concentrations of silicon and calcium leached out from the concrete samples into the liquid phase and the measured pH values were used as input data for a mathematical approach to the study of sulfate resisting cement. The performance of sulfate resisting cement-based concrete was improved when exposed to sulfate attack, but not in the case of leaching corrosion caused by water.

Correlation Analysis between Different Types of Corrosion of Concrete Containing Sulfate Resisting Cement

Utilization of pozzolanic materials (fly ash, slag, zeolite, metakaolin, microsilica and more) in the manufacturing of cement and concrete has increased considerably over the last decades. Another option is to use concrete containing sulfate resisting cement. This could help minimize the harmful impacts on concrete exposed to an aggressive environment. The issue of the deteriorative impact of the three types of concrete corrosion (acidic, sulfate and leaching) investigated using correlation analysis is presented in the paper. Concentrations of silicon and calcium leached out from the concrete samples into the liquid phase and the measured pH values were used as input data for a mathematical approach to the study of sulfate resisting cement. The performance of sulfate resisting cement-based concrete was improved when exposed to sulfate attack, but not in the case of leaching corrosion caused by water.

Corrosion resistance of sulfated cements in carbonate and in carbonate-sulfate mediums

Corrosion resistance of sulfated cements in carbonate and in carbonate-sulfate mediums has been studied. The samples have been placed in carbonate and carbonate-sulfate mediums for investigation stability of sulfated cements. The same researches were done with sulfate resistant portland cement to compare stability of samples. High corrosive resistant of sulfated cements is conditioned by forming dense and strong cement stone. The obtaining of corrosion resistant cements is possible with usage of the ordinary portland cement clinker with inclusion to them sulfoferrite and sulfoalumoferrite clinkers. Sulfated cements have the higher corrosion stability in contrast to ordinary sulfate resistant cement.

Effect of internal sulfate attack on the properties of sulfate-resisting cement and alkali-activated slag

This work aims at studying the effect of internal sulfate attack on the properties of sulfate-resisting cement (SRC) and alkali-activated slag (AAS). Blast-furnace slag was activated by 3% sodium hydroxide (NaOH) and 3% sodium silicate (Na2SiO3) by weight of slag. Magnesium sulfate (MgSO4) solution with concentration of 0, 4, 12, and 20 wt.% was mixed with AAS and SRC at water to cement ratio (W/C) of .25. The results showed that the AAS setting times decrease with MgSO4%. As the MgSO4% increases up to 12%, the SRC setting times are elongated, and then shortened at 20%. The compressive strength of SRC decreases with the increase of MgSO4%. In contrast, the AAS compressive strength increases with MgSO4% up to 12%, then decreases at 20%. Drying shrinkage reduction and increment were observed when SRC and AAS were mixed with MgSO4. These results were confirmed by X-ray diffraction, Fourier transformer infrared spectroscopy, and thermogravimetric (TG/DTG) analyses. The results proved that, the AAS can be beneficially used in cement concrete containing high sulfate concentration with better performance than SRC.

Chloride interaction with concretes subjected to a permanent splitting tensile stress level of 65%

Penetration of chloride ions into concrete is a complex topic. These ions together with other dissolved chemical species can penetrate into cementitious materials by convection through capillary pores or cracks. Prolonged periods of drying followed by re-wetting can provoke a similar transport mechanism. Saturated cement based materials experience diffusion of water dissolved ions. Ions in the diffusing solution experience chemical interaction with a hydrated cement paste. Some ions are physically adsorbed, others react chemically and part remain free in the solution. This turns the transport into a reactive form of diffusion. The nano-pores which are part of the cement gel, act as sinks for the intruding aggressive chlorides. When concrete is subjected to splitting tensile stresses and a critical stress ratio is surpassed the presence of micro-cracks modifies the transport of chlorides within this material. It was noticed that the chloride content of concrete decreased in zones close to the surface specially where the main pattern of micro-cracks follows the loading plane. It was also observed a secondary micro-crack system which develops perpendicularly to the main splitting-crack system and is connected to it. It was found that this secondary system was also responsible of lowering the level of the chloride content in regions close to the surface even at unexpected distances located far away from the direct influence of the splitting plane. The presence of an inner peak of chloride was also observed, which represents the extent of the damaged or altered zone. This region will be called in this paper as the convection zone. It is believed that the form of the obtained chloride profiles are influenced by the type and amount of binder utilized. Thus, some similarities were found in all the studied concretes such as the formation of a convection zone. On the other hand the level of chloride content and the shape of the profile seem to vary depending on BFS replacement of OPC or when high sulfate resistant cement (HSR) is used as a single binder.

Electrochemical Evaluation of Reinforcement Concrete Exposed to Soil Type SP Contaminated with Sulphates

The present research evaluates the electrochemical behaviour of concrete exposed to SP soil type, sand from marine environment and contaminated with 1, 2 and 3 % de MgSO4, this experimental setup simulates what happens on the foundations of civil infrastructure as bridges, docks, highways, etc., when they are built on contaminated soils with this aggressive agent due to discharges of wastewater, marine waters or areas polluted by agrochemicals. The concrete used in making specimens of study was designed according to the ACI method 211.1, it was considered to design the concrete mixture a ratio w/c=0.65 (f´c=250 kg/cm2), two types of cement, ordinary portland cement (CPC 30R) and sulphate-resisting cement (CPC 30R RS), in the specimens were embedded as reinforcement bars of steel AISI 1018 and Galvanized steel. Ecorr was evaluated according to the standard ASTM C-876-09 and the corrosion kinetics Icorr it was monitored by the technique of Linear Polarization Resistance (LPR), according to standard ASTM G-59-97(2009). The results of Ecorr and Icorr correspond to 266 days of exposition in specimens to SP soil type contaminated with MgSO4 indicating with increasing concentration of aggressive agent to 3% it is considerably decreased the corrosion resistance of the concrete specimens produced with sulphate resisting cement and reinforced with galvanized steel.

Effect of SCMs on mechanical, chemical and microstructural properties of SRC in acidic medium

This paper studies the durability of the mortar base of sulphate-resistant cement (SRC) with supplementary cementitious materials (SCMs) as substitutes for SRC to reduce its cost and enhance its durability to acids. Three SCMs (granulated blast-furnace slag, natural tuff and natural pozzolan) are used with weight ratios of 5, 10, 15 and 20%. A compressive strength test, X-ray diffraction and weight loss test were carried out through the conducted experiments and the results were compared with values for reference with SRC. The different results show that the compressive strength decreases with increasing tuff and slag contents, while the weight loss decreases with increasing tuff content. Mortars with a pozzolan content of 10% give similar results to SRC.

Research on Produced Fluid Corrosion Resistance Oil Well Cement Paste System in Adjustment Well

To design oil well cement paste system and ensure well cementation quality of adjustment well in work area of tertiary oil recovery (EOR), the composition, microstructure and strength of cement paste matrix eroded by producing water were tested and studied by HTHP Curing Chamber, HTHP corrosion tester, X-ray diffraction, scanning electron microscope (SEM), universal testing compressor and some other laboratory equipment according to the condition that producing water contains sulfate (SO42-) and bicarbonate (HCO3-). The corrosion law and mechanism of oil well cement paste matrix were analyzed. The problem for designing corrosion resistance oil well cement paste system was investigated. The corrosion law and mechanism of oil well cement paste matrix by SO42- and HCO3- were raised. The corrosion resistant oil well cement paste system was designed, which was suitable to the adjustment well in area of EOR in Daqing. The results show that the compositions of cement paste matrix changed after corrosion by SO42- and HCO3- for a long term. The secondary gypsum, ettringite and calcite were produced, which changed the microstructures and declined the compressive strength of cement paste matrix. The change degree of compressive strength of cement paste matrix was affected by corrosion media concentration, corrosion time and other conditions. The higher concentration of corrosion media and the longer of corrosion time were, the greater decline of cement strength occurred. The formula of corrosion resistance oil well cement paste system was designed, for which the high sulfate resistant cement as architectural substrate and the PZW as admixtures were used to improve the strength and penetration resistance ability of cement.

Proposed mechanism for the formation of oxychloride crystals during sodium chloride application as a deicer salt in carbonated concrete

Even though freeze and thaw performance for uncarbonated concrete may be considered good, its resistance may be considerably affected by carbonation and the presence of deicing salts.Besides the general belief that the major single mechanism that contributes to frost-scaling damage is purely mechanical and due to stresses caused by the differences in thermal expansion coefficients between ice and the underlying concrete, there is also experimental evidence of scaling deterioration on concrete that has been exposed to chloride deicers at temperatures just above freezing without the influence of ice formation. This fact is suggestive of another deterioration mechanism occurring at low temperatures.Blast furnace slag (BFS) and ordinary Portland cement (OPC) concretes with different slag/binder ratio and a high sulfate resistant cement concrete (HSR) were wet cured during a short period, followed by additional exposure to accelerated and natural CO2 environments. It was found that carbonation predisposition depends on amount of BFS replacement and cement type. Vaterite and Calcite were the two types of carbonated minerals identified by XRD analysis. The carbonated face of concrete was exposed to freeze and thaw cycles under deicing sodium chloride salt solution. It was noticed that the deicing scaling resistance of carbonated concrete decreases, as the ratio between carbonates coming from CSH decomposition over the ones coming from available CH (carb. ratio CSH/CH) increases.The presence of a well packed net of oxychloride minerals of prismatic and platey shape and growing underneath a crust of cement paste were observed in polarized microscopy after the freezing cycle. The crystallization pressures caused by these minerals below the surface are believed to contribute to concrete scaling.The mechanism is started with the dissolution of calcium bearing minerals from the carbonated concrete paste at the low temperatures occurring during the freezing cycle. The available calcium hydroxide present in the pore solution combines with chloride ions to form temporary oxychloride crystals. The crystal growth caused by these salts causes paste disruption. During the thaw cycle oxychlorides dissolve releasing calcium hydroxide, thus potentially contributing to calcium leaching from concrete in every cycle and also maintaining calcium availability for subsequent oxychloride formation during the next cycle. CO2 equilibrium in the pore solution is crucial for mineral stability; therefore the reactions are temperature and pH dependent.

Sprayed Polymer Concrete for the Rehabilitation of Sewage Systems

Concrete sewage systems can be severely damaged when attacked by biogenic sulfide corrosion. While minor aggressive exposures can be accounted by using a high sulfate resistant cement, higher concentrations of acid (pH 3.5) require the sealing and protection of concrete surfaces. Throughout the decades, polymer concrete (PC) has been used in sewage systems due to its high acid resistance. However, it has been limited to newly constructed pipes and manholes as well as local repair. In cooperation with Massenberg GmbH, the Institute of Building Materials Research of RWTH Aachen University developed a new way of applying PC for the rehabilitation of damaged concrete surfaces of sewage systems; by dry spraying an epoxy mortar on concrete, layers with an average thickness of 20 mm on vertical and overhead surfaces were successfully produced. The dry sprayed PC was examined for its overall performance such as strength, adhesion, thermal expansion, and wear. A special focus has been put on the diffusion properties and the durability in an acidic environment. Based on these positive laboratory results, a first practical application in a waste water structure is currently underway.

Effect of Selected Alternative Fuels and Raw Materials on the Cement Clinker Quality

Abstract The article deals with the study of the effects of alternative fuels and raw materials on the cement clinker quality. The clinker quality was expressed by the content of two principal minerals alite C3S and belite C2S. The additions of alternative fuels ashes and raw materials, in principle, always increased the belite content and conversely reduced the amount of alite. The alternative fuels with high ash content were used such as the meat-bone meal, sewage sludge from sewage treatment plants and paper sludge and the used alternative raw materials were metallurgical slags - granulated blastfurnace slag, air cooled blastfurnace slag and demetallized steel slag, fluidized bed combustion fly ash and waste glass. Meat-bone meal, sewage sludge from sewage treatment plants and paper sludge were evaluated as moderately suitable alternative fuels which can be added in the amounts of 2.8 wt. % addition of meat-bone meals ash, 3.64 wt. % addition of sewage sludge ash and 3.8 wt. % addition of paper sludge ash to the cement raw mixture. Demetallised steel slag is suitable for production of special sulphate resistant cement clinker for CEM I –SR cement with addition up to 5 wt. %. Granulated blastfurnace slag is a suitable alternative raw material with addition 4 wt. %. Air cooled blastfurnace slag is a suitable alternative raw material with addition 4.2 wt. %. Waste glass is not very appropriate alternative raw material with addition only 1.16 wt. %. Fluidized bed combustion fly ash appears not to be equally appropriate alternative raw material for cement clinker burning with less potential utilization in the cement industry and with addition 3.41 wt. %, which forms undesired anhydrite CaSO4 in the cement clinker.

Simplified methodology to evaluate the external sulfate attack in concrete structures

The external sulfate attack is a degradation process that causes expansion and cracking in concrete structures. Due to the absence of simplified methodologies to predict the potential damage, codes specify that sulfate resistant cement should be used whenever the surrounding sulfate concentration surpasses a predefined limit. This may lead to penalizing measures as the size of the element or the mechanical properties of the concrete used are not considered. In the present work, an alternative approach is proposed. A simplified chemo-mechanical methodology is deducted to assess the potential damage in concrete elements exposed to sulfate rich environments. Equations to estimate the penetration of sulfates are derived from a numerical model taking into account sulfate consumption, acceleration of the penetration induced by cracking and decrease in diffusivity caused by pore filling. Failure modes associated to this phenomenon are analyzed and a set of equations to assess the risk of failure are deducted. Finally, a parametric study with different geometries of elements and surrounding sulfate contents is performed. The results show that the criterion included in codes might be modified depending on the characteristics of the structure.

One-Year Sulfate Attack on Various Types of Fine Grained Concrete

Concrete shows extensive degradation when exposed to the external sulfate attack, characterized by ingress of sulfate ions from surrounding medium. This process leads to gradual pH decrease, to expansion, cracking, spalling of concrete, and finally to the complete disintegration of the material. Sulfate attack becomes a major destructor in sewage collection systems where the concrete sewer pipes are exposed to sulfates from wastewater as well as from biogenic activity of bacteria. This paper is focused on the sulfate attack on fine grained concrete where the effect of 0.5% sulfuric acid, simulating biogenic sulfuric acid corrosion, 5% sodium sulfate solution and solution simulating sewage water on various types of concrete has been investigated. The concrete specimens were characterized after exposition to corroding media by their mechanical parameters, microstructure and in the case of H2SO4 as the most aggressive corroding solution, the mineralogical composition was also determined by XRD analysis. It was found that the exposition to Na2SO4 solution twofold improved flexural strengths of concrete mixes based on Portland and sulfate-resisting cements. Contrary, the exposition to H2SO4 solution significantly decreased compressive strengths of all types of concrete.