Special Cement Research Articles

Cement Composites Biodeterioration by Acidithiobacillus Thiooxidans

The focus of this work was to study the biodeterioration of special cement composites by sulfur-oxidizing bacteria Acidithiobacillus thiooxidans. The laboratory prepared cement composites that contained the selected additives - silica fume (a secondary raw material) and zeolite (a natural raw material), as partial replacements for the binder. The tests were carried out in laboratory conditions. During the experiments, changes to the pH values and the Ca and Si concentrations were observed in the liquid phases. Based on the achieved results, it can be concluded that concrete composites with partial replacement of the binder by silica fume and zeolite have a higher resistance to biogenic sulfuric acid.

Experimental study on pore structures and mechanical properties of ferroaluminate cement under sulfate attack

Ferroaluminate cement (FAC) emerges as a special cement with outstanding durability, offering promising applications. However, the resistance to sulfate attack of FAC remains inadequately understood. In this paper, the impact of sulfate attack on the pore structure of FAC concrete is explored through nuclear magnetic resonance (NMR) tests from a microscopic perspective. Meanwhile, the macroscopic mechanical characteristics of concrete attacked by sulfate are investigated under different loading conditions, including splitting tensile and conventional triaxial compression. NMR test analysis shows that as the degree of erosion increases, the number of mesopores and macropores in FAC concrete decreases while the number of micropores increases. The changes in pore structure distribution alter the mechanical response of specimens. The discussion of strength characteristics, deformation behavior, and energy parameters in conventional triaxial tests reveals that FAC concrete attacked by sulfate exhibits superior mechanical properties under confining pressure. Uniaxial strength results indicate that sulfate attack has less impact on specimens under tensile stress state than under compression. Based on the experimental findings, this paper introduces a sulfate attack impact factor to capture the uniaxial strength changes. Further, a multiaxial strength criterion is developed to describe the strength properties of sulfate-attacked concrete under triaxial stress conditions.

Physical and mechanical properties of special cementitious materials modified by nano-particles

Compared to ordinary Portland cement (OPC), sulphoaluminate/ferroaluminate cement (SAC/FAC) and aluminate cement (CAC) are the most promising repair materials due to their excellent early strengths, but the later strengths of SAC/FAC develop slowly, and the later strengths of CAC are obviously declined. This paper studied the effects of nano-SiO2 and nano-ZnO on the physical properties, mechanical properties and early hydration processes of three special cement-based materials and compared them with OPC-based materials. The strength development and early hydration mechanism were revealed by hydration heat, scanning electron microscopy and X-ray diffraction. The test results showed that with the increasing content of nano-SiO2, the setting time of the four cement pastes was gradually shortened, the fluidity of four fresh mortars was gradually reduced, and their compressive and flexural strengths at all ages were improved to different degrees. Nano-ZnO significantly prolonged the setting time of OPC paste and increased the fluidity of OPC mortar, which had a negative effect on its early compressive and flexural strengths, but enhanced its late strengths. After the addition of 1 % nano-ZnO, the initial and final setting time of OPC were about 12 times and 13.4 times that of ordinary OPC paste, respectively. The effect of incorporating nano-ZnO on the physico-mechanical properties of three special cements was similar to that of nano-SiO2. The strength loss of CAC mortar with two kinds of nanoparticles was greatly reduced. The incorporation of nano-SiO2 and nano-ZnO could promote the hydration process of three special cements, resulting in the denser microstructure and higher crystallinity of hydration products.

Determination of Thermal Properties of Autoclaved Aerated Concrete Wall Sections Constructed with Distinct Mortars by the Experimental and Theoretical Data

This study investigated the thermal properties of autoclaved aerated concrete(AAC) wall sections constructed with distinct mortars. Within the scope of the study, four distinct wall sections of 25x25x5cm dimensions were created using AAC special adhesive mortar, cement mortar, lime mortar and cement-lime mortar. The thermal conductivity(λEXP) that was determined by the heat flow meter(HFM) method and bulk density(ρEXP) of each wall section was determined in the laboratory. Specific heat values(cEXP) of mortars and aerated concrete material were determined experimentally in the study. The thermal diffusivity value(αEXP), thermal effusivity value(eEXP) and volumetric heat capacity(VHCEXP) of each wall sample were calculated using the experimental data obtained in the laboratory. In addition, αTEO, eTEO and VHCTEO of each wall sample were calculated theoretically using the thermal conductivity, bulk density and specific heat value given in the literature and standards for the same wall sections. In the study, experimental data was compared to the theoretical data. As a result, the thermal properties of walls constructed with distinct mortars and thermal differences formed in the walls due to the effect of these mortars could be determined with experimental data. However, it was observed that theoretical data were insufficient to detect these thermal differences.

Cementitious material development for additive fabrication

For the 3D STAR project and 3D printing purposes, a special fine-grained cement mixture from locally available raw materials was developed. The reason for the development of the custom mixture was the possibility of arbitrary optimization of the developed mixture at any stage of the project and for any type of application. Mix design, printing head and the entire system from mixing to extrusion was the subject of research and development for this project. It was therefore necessary to address both issues in parallel and to respond in both sectors to the realities arising from the partial results of the different groups involved in the development.

Occurrence Mechanism of the Abnormal Gelation Phenomenon of High Temperature Cementing Slurry Induced by a Polycarboxylic Retarder.

The class G oil well cement is a type of special cement that can be subjected to a high temperature formation environment. It was found that the class G cement tail slurry with a low polycarboxylic retarder dosage (usually ≤1% by weight of cement) was more prone to cause the abnormal gelation phenomenon (AGP) than the lead slurry with a high retarder dosage at a high temperature (usually when T ≥ 120 °C). This study aimed at the occurrence mechanism of this unfavorable phenomenon that seriously endangers the cementing security. Results showed that the abnormal gelatinous region underwent premature hydration; namely, the calcium hydroxide and calcium silicate hydrate (C-S-H) content were all higher than the nongelatinous region, while the copolymer content was the opposite. Correspondingly, the theory of "premature hydration and crystal nucleation" was proposed to explain the abnormal gelation mechanism of a cementing tail slurry with an insufficient retarder dosage. Furthermore, a novel functionalized copolymer retarder "PAIANS" was synthesized to alleviate the AGP.

Exploring the mechanism of micro-nano bubble water in enhancing the mechanical properties of sulfoaluminate cement-based materials

Sulfoaluminate cement (SAC) is a special cement that has attracted significant research attention due to its low-carbon properties. This article presents an insight into the improvement effect of micro-nano bubble water (MNBW) on the hydration and mechanical properties of SAC-based materials. SAC paste samples mixed with MNBW and tap water, respectively. These specimens were subjected to various tests and analyses, including isothermal calorimetry, ICP, XRD, TG, SEM, MIP, and mechanical property evaluations. The results demonstrated that MNBW accelerated the dissolution and hydration of SAC, improved the rheological properties of SAC paste, optimized the pore-size distribution and reduced the total porosity in the harden matrix. Compared with the tap water group, the MNBW group’s compressive strength increased by 23.8% (1 day) and 14.4% (28 days). Similarly, the flexural strength increased by 16.6% (1 day) and 10.7% (28 days). This study revealed the mechanism of MNBW accelerating the hydration of SAC and improving its mechanical properties, offering a new perspective for the research in SAC modification and practical application.

Investigation of Bauxites of Various Deposits as Raw Materials for Special Alumina Cements

AbstractThe study deals with the bauxites of deposits of Turkey, Guinea and Guyana, which are used in alumina production, as raw materials for special alumina cements. The chemical and mineralogical compositions of bauxites of various deposits have been determined and bauxites quality relative to alumina cements obtaining has been analyzed. It is ascertained that: Turkish bauxite contains more than 9 wt. % SiO2; Guinean bauxite (deposit Kindia) has a reduced content of Al2O3 (below 45 wt. %); and Guyanese bauxite (deposit Aroaima) complies with requirements for alumina cement completely. Cements of different purity, based on the bauxites being studied, have been obtained and the possibility of using the low‐grade bauxites as raw materials for special alumina cements has been proved. Medium‐purity cements with high content of Al2O3 can be used for heat‐resistant concretes, and low‐purity cements with high content of Fe2O3 can be applied for a new kind of functional materials – sacrificial binders in passive safety systems (core‐catchers) of nuclear power plants.

Effects of early vibration and resistant strategies on bond performances between high-strength concrete and rebar

The local bond performances between rebar and high-strength concrete (HSC) exposed to early vibration were experimentally investigated in this study. In addition, three vibration-resistant strategies, including additions of special rapid-hardening cement(calcium sulphoaluminate cement, CSA), shrinkage compensation admixture (expansion agent, EA), and toughening metallic fibers (steel fiber), were verified through penetration resistance, compressive, and central pull-out tests, respectively. Finally, two-way ANOVA tests were conducted to understand the significance of each strategy from a statistical perspective. The results demonstrated that early disturbances compromise bond performances by weakening chemical adherence and mechanical interlocking effects, which considerably degrade bond strength and stiffness. The presence of EA delayed the setting and hydration of concrete and prolonged vibration-sensitive duration. However, the later expansive hydrate products effectively strengthen the bond performances and compensate for early-stage vibration-induced damage. In comparison, the synergetic effects between CSA and Portland markedly enhance the hydration reactivity of blends at early stages, which can achieve threshold maturity and vibration resistance within hours. However, excessive CSA (10%) severely compromises the construction time of mixtures and amplifies the cracking potentials of HSC under the constraints of steel bars. The synergetic effects of steel fibers and aggregates formed disordered networks to enhance the vibration resistance and rigid skeletons for bridging cracks of HSC. The two-way ANOVA results indicate that EA significantly improves the mechanical performances of HSC, followed by steel fibers. The additions of expansive agents and steel fibers are highly recommended in engineering with vibration scenarios. In contrast, the dosages of CSA (or similar early-strength agents) should be carefully controlled unless with a robust shrinkage compensation strategy.

Effect of Special Cement CPA on the Characteristic Properties of Cementitious Materials Based Waste Glass Powder: Poozolanic Activity and Heat Treatment

Abstract The main purpose of this study is to evaluate the effect of curing method on the compressive strength of waste glass powder as a supplementary cementitious material. This work presents an experimental study on the physico-mechanical characterization of waste glass powder (GP) as partial replacement of special cement (Algerian cement without additions CPA) based high performance cementitious material, varying the percentage of GP by 10%, 20% and 30% (by weight of cement), the curing methods: water curing at 20± 2 °C and heat curing by under accelerated drying in an oven at 100 °C (stoving). Half of the mortar samples 40x40x160 mm were treated with stoving just after demolding then kept in the open air, the other half was kept in fresh water in order to evaluate their sustainability and index of Poozolanic Activity (I) at different ages: 7, 28, 90 and 365 days. The compressive strength results showed that there is an increase in compressive strength with the increase in age of the two curing methods but the strength of all mixtures which have been stoved is inferior to those of the same mixtures preserved in fresh water at different ages. The best rate of replacement of the cement by GP is 20% following the results obtained for the compressive strength and Poozolanic Activity Index I.

STRUCTURE AND PROPERTIES OF THE ETRINGITE PHASE

Problem statement. Aluminate and sulfoaluminate cements are not produced in Ukraine, despite a rather significant need for binders of this class. The use of imported raw materials is limited by the high cost and certain disadvantages occurring during exploitation including rapid hardening, significant heat generation, which is associated with instability of some sulfoaluminates. At the same time, it is possible to highlight the following problems in the direction of expanding possibilities of using special cements of this type: stabilization over time and operating conditions of the hydrosulfate phase based on alumina cement, as well as modification of the compositions of mineral binders based on calcium sulfate dihydrate (CaSO4·2H2O) and development of binders of this class based on secondary production products. The main factor is that during hydration of sulfoaluminates and aluminates in the presence of gypsum (CaSO4·2H2O), a hydrosulfoaluminate phase is formed, which makes it possible to obtain a hardened cement paste structure with special properties. Then monocalcium hydrosulfoaluminate turns into hydrosulfoaluminate of the low-sulfate form С3А·СaSO4·12H2O with the release of gibbsite Al2O3·3H2O. Also, ettringite С3А·СaSO4·nH2O and 2(С2S)·nH2O is formed and hydrated calcium silicate CSH(B) can be formed. When gypsum is added to cement, ettringite is formed in this system. Etringite is one of the components. It is not formed initially, but through intermediate structures. During hydration reactions, ettringite is rearranged, neoplasms are formed, which can lead to gypsum corrosion. Etringite loses its stability. Herewith, the problem of primary and secondary ettringite arises. Primary ettringite creates conditions for strength. Secondary ettringite is formed already in the hardened system and leads to internal stresses. Formation of secondary ettringite can have both positive and negative consequences. The purpose of the atrticle is to investigate structure and properties of the ettringite phase. Conclusions. The hydration process depends on the Gibbs surface energy. Change in surface energy depends on the CaO/Al2O3 ratio. It was established that the surface energy increases with an increase in the CaO/Al2O3 ratio. The paper has studied influence caused by the ettringite phase on the main characteristics of alumina cement and gypsum in a modified gypsum binder. Studies have been conducted on formation of the maximum amount of ettringite phase. We have calculated the maximum amount of the ratio of alumina cement and gypsum to obtain the maximum amount of mineral – 70 % alumina cement and 30 % gypsum. The highest effect is achieved during the simultaneous use of С6АṤ3Н32 and АН3, which occurs during hydration of С4А3Ṥ. Taking into account the above, it is advisable to obtain clinker containing calcium sulfoaluminate and cements based on it.

Research and Development of Anti-High-Pressure Sealing Material and Its Bonding Performance

To solve the problem of the field application of downhole hydraulic fracturing technology due to the difficulty in sealing holes, this study analyzes the influence of special cement, expansion agents, stabilizers, and fiber material on basic properties, such as the setting time, fluidity, and compressive strength of high-pressure sealing materials through systematic tests based on a summary of conventional sealing materials. It was determined that with 20–30% special cement and 4% expansion agent added, and a fiber material length of 8 mm and volume of 1%, the high-pressure sealing material had high fluidity and a large expansion rate, demonstrating early strength. The bond performance of the high-pressure sealing material was tested through the variable-angle shear test. The relationship between the fractal dimension of the coal-rock mass around the borehole and the bond performance of the high-pressure sealing material was also explored.

The implementation of an easy-to-apply NMR cryoporometric instrument for porous materials

Time-domain NMR has been extensively utilised to study various characteristics of fluid-saturated porous,materials for instance their mobility, dynamics, stiffness, viscosity and rigidity features, particularly for solid hydrocarbons, rubbers and other polymers. As a unique time-domain technique available for over 30 years, NMR cryoporometry (NMRC) may be used to obtain pore-size distributions of the measured samples. To accurately control the sample temperature, a Peltier thermo-electrically cooled variable temperature probe has been developed and integrated with a highly compact precision NMR time-domain relaxation spectrometer, therefore providing the community with a high-performance instrument for NMR Cryoporometry. To extend the application of aforementioned high-performance NMRC instrument into more senarios, we designed a series of light-weight, compact and integral models with optional NMR frequencies from 12 MHz up to 23 MHz. The measured sample temperature can be precisely controlled from about −60 °C to +80 °C, with an excellent temperature resolution of 10 mK or better near the probe liquid bulk melting point. Therefore, it offers a fairly wide NMRC pore-size distribution ranging from about 1 nm to 2 μm by using water as the probe liquid in the pores, significantly wider than is possible when applying generic NMR Spectrometers for NMRC. A preliminary example of NMR Cryoporometric measurements on two special cement samples is shown in the paper in which the measured pore scales as well as their repeatability are demonstrated. Furthermore, various nano-materials, such as MOF, zeolite and shale kerogen would be potential materials to study by using these new available NMRC instrument models. We aim to offer this technique as a quantitative and easy-to-apply unitary benck-top tool for an even wider range of porous material.

The Effect of Biological Corrosion on the Hydration Processes of Synthetic Tricalcium Aluminate (C3A)

This paper presents a study related to the biological degradation of a tricalcium aluminate (C3A) phase treated with reactive media from the agricultural industry. During one month of setting and hardening, synthetic C3A was subjected to corrosion in corn silage, pig slurry and chicken manure. The hardening process of the C3A phase in water was used as a reference sample. The phase composition and microstructure of the hydrating tricalcium aluminate slurries were characterised by X-ray diffraction (XRD), thermal analysis (DTA/TG/DTG/EGA), scanning microscopy (SEM, EDS) and infrared spectroscopy (FT-IR). In the samples studied, it was observed that the qualitative and quantitative phase composition of the synthetic tricalcium aluminate preparations changed depending on the corrosion exposure conditions. The main crystalline phases formed by the hydration of the examined samples in water as well as in corrosive media were the catoite (Ca3Al2(OH)12) and hydrocalumite (Ca2Al(OH)7·3H2O) phases. Detailed analysis showed the occurrence of secondary crystallisation in hydrating samples and the phases were mainly calcium carbonates (CaCO3) with different crystallite sizes. In the phase composition of the C3A pastes, varying amounts of aluminium hydroxides (Al(OH)3) were also present. The crystalline phases formed as a result of secondary crystallisation represented biological corrosion products, probably resulting from the reaction of hydrates with secondary products resulting from the metabolic processes of anaerobic bacterial respiration (from living matter) associated with the presence of bacteria in the reaction medium. The results obtained contribute towards the development of fast-acting and bio-corrosion-resistant special cements for use in bioenergetics.

The Usage of Crystalline Additive on Concrete Performance

Indonesia as a maritime country has a number of structures in coastal areas that are made from concrete. Sulfate attack is one of the common deteriorations that could occur due to the exposure of saltwater to the concrete. Unfortunately, the Type II and Type V cements, which are the special cements that are resistant to sulfate, are rarely used due to their high prices. The objectives of this research are to compare the performance of concrete mixture that was prepared by using the standard cement mixed with crystalline material and the concrete mixture that was prepared by using two different brands of Type V cement. There were five concrete mixture variations tested for their compressive strength and permeability. To assess the permeability of the concrete, the specimens were placed under pressured water for 72 hours and the water penetration depth was measured. From the research results, it was found that the usage of crystalline additive (CA) made the compressive strength increased at a faster rate and the concrete mixture that contained Type I cement and 0.7% of crystalline material had the highest compressive strength value. In terms of the permeability of the concrete, it can be seen that the specimens that were mixed with CA were more effective in stopping the water to penetrate the specimens than the specimens prepared with either of Type V cement.

Degradation of oil well cement with sodium chloride content exposed to supercritical carbon dioxide conditions: Temperature and pressure effects

Understanding the effects of temperature and pressure on the supercritical CO2 degradation of wellbore cement with NaCl content is essential for cementing oil wells in Brazil's deepwater pre-salt basin. The behavior of the cement paste used in cementing oil wells in this environment is very complex, with significant amounts of CO2 and a thick salt layer that requires a high demand on special wellbore cement capable of adequately sealing and assuring stability to the oil wells. For these reasons, the objective of this study was to investigate the effect of NaCl in cement on oil wells exposed to supercritical CO2 simulating pre-salt reservoir conditions. Cement slurry samples were prepared using Class G Portland cement (API 10 A), NaCl, water-to-cement (w/c) ratio of 0.46, and deionized water with (0 and 10% NaCl content). Supercritical CO2 experimental runs were carried out under different conditions for 7 h. Before and after exposure to CO2, the material was characterized by multiple analytical techniques. The results indicate that salt under temperature and pressure and the scCO2 environment accelerates the carbonation process by decomposing the hydrated product, increasing the CaCO3 content. In this scenario, investigations of the effect of adding NaCl to cement pastes are limited.

Editorial for Special Issue Cement and Construction Materials

Cement-based materials have always been the main choice for the construction of civil engineering infrastructures [...]

Optimizing the compositions of refractory cements produced using the waste of chemical industry

The article presents the results of optimization of the quantitative compositions of cobalt-containing calcium-aluminate and barium-aluminate special cements prepared from chemical industry wastes. Based on the obtained experimental data, the coefficients of the polynomial were computed which express the dependence of the ultimate compression strength and the melting temperature on the quantitative ratio of the CaAl2O4, CaAl4O7, and CoAl2O4 phases for calcium-aluminate cement and the quantitative ratio of the ВaAl2O4, ВaAl12O19, CoAl2O4 phases for barium-aluminate cement. The "composition–property" diagrams and the projections of the lines of the same level were plotted for the ultimate compressive strength and the melting temperature of the obtained cements. The following promising areas were selected for the CaO–CoO–Al2O3 system (wt.%): 25–55 CaAl2O4, 15–35 CaAl4O7, and 25–45 CoAl2O4; and for the ВaO–CoO–Al2O3 system (wt.%): 60–20 ВaAl2O4, 10–20 ВaAl12O19, 30–60 CoAl2O4. The main physical-mechanical properties of the developed cements of optimal composition are the following: the fineness of grinding is characterized by the total passage through the sieve No 006; for calcium cements: water-cement ratio of 0.2, the setting time: the initial set of 1 h 10 min, and the final set of 5 h 40 min; the ultimate compression strength after hardening of 28 days of 63 MPa; the for barium cements: water-cement ratio of 0.16; the setting time: the initial set of 1 h 50 min, and the final set of 5 h 00 min; the ultimate compression strength after hardening of 28 days of 66 MPa; and the calculated mass absorption coefficient =175 cm2/g. The refractoriness is 16300C and 17500C for calcium cement and barium cement, respectively.

On the operation of cement stone in well and modern strategy of selection of backfill materials

A long way of development of cementing technology providing the advancement of backfill materials, the methods of preparation, chemical treatment and transportation of plugging material into the borehole annulus of the well did not solve all the problems of the quality isolation of formations. There are neither justified physical criteria nor accurate methods of estimation of supporting quality, as it is quite troublesome to set well conditions while conducting experimental works towards specifying the large number of the factors simultaneously affecting the longevity of well support. In this regard, there is no generally accepted method of testing backfill materials and the issue of necessary sustainability of stone from various bakfill materials designed for cementing of columns and setting cement bridges is not solved as well. Leading drilling service companies (Schlumberger, Halliburton etc.) of the world do not use special cement types and instead, prepare their own mixture for each cementing process on the basis of cement of selected for these oil-gas fields. As a result of mixing various types of weighting agents and other additives with base cement, a backfill system necessary for specified well is obtained. These systems are produced on specially equipped facilities in the world. The researches carried out justify that it is possible to obtain high quality simplified and weighted cement slurries on the basis of domestic raw materials with state-of-the-art technologies and equipment.

Analiza kamienia cementowego w otworze wiertniczym oraz nowoczesna strategia doboru systemów cementacyjnych

The long road of development of cementing technology, which ensured the development of cement compositions, methods of preparation, chemical treatment and transportation of binder material into the annular space of the well, did not solve all the problems of high-quality isolation of the layers. A reasonable physical criterion and exact methods for assessing the quality of fastening have not been found either as it is very difficult to reproduce downhole conditions during experimental work in order to establish a large number of simultaneously acting factors on the durability of the borehole lining. In this regard, there is no generally accepted method for testing cementing materials in the world and the issue of the necessary strength of stone from various cementing materials intended for cementing columns and installing cement bridges has not been resolved. The world's leading drilling service companies (Schlumberger, Halliburton, etc.) do not use special cements such as UCG, OCG, etc., but prepare their mixture specifically for each cementing process, based on one base cement selected for these oil and gas fields. Various types of weighting agents, lighteners and other mixing additives with the base cement provide the well-specific grouting system. All over the world, these systems are being prepared at specially equipped bases. The conducted studies give grounds to assert that high-quality normal, lightweight and weighted cement mortars can be obtained on the basis of local raw materials, provided that modern technology and equipment are available.