Portland Cement CEM Research Articles

Fly Ash from Thermal Conversion of Sludge as a Cement Substitute in Concrete Manufacturing

Striving for reduction of production costs and constraints on natural resources cause the use of waste materials as substitutes of traditional raw materials to become increasingly important. Dynamic development of sewerage systems and sewage treatment plants observed over the recent years leads to increase of mass of the produced sewage sludge. According to the Waste Law, the municipal sewage sludge can be used if it is properly stabilized, e.g., through thermal processing. This process results in significant quantities of fly ash which must be properly utilized. The paper presents results of investigations of influence of partial replacement of cement by the fly ash from sewage sludge on concrete parameters. It was designed as a C20/25 class concrete mix, based on the Portland cement CEM I 42.5R with various ash content. Physical and chemical properties of the ash as well as frost resistance and the compressive strength of the concrete after 28, 56 and 365 days of curing were investigated. The obtained results of investigations confirm the possibility of application of fly ash wastes as a cement substitute in the concrete manufacturing. If a predefined quantity of cement is replaced by the fly ash, then one can obtain cement composite with good strength parameters.

Formwork Pressure of a Heavyweight Self-Compacting Concrete Mix.

High-fluidity and self-compacting concrete (SCC) mixes were developed using special aggregates for radiation-shielding concrete. The special aggregates comprised heavyweight and hydrous aggregates (crushed magnetite, crushed serpentine, and their mixtures), which were selected to provide an enhanced attenuation of gamma and neutron radiation, respectively. For the mixed concrete design with a bulk density of up to 3570 kg/m3, two cement types were used: Portland cement CEM I and slag cement CEM III/A. The basic properties of the fresh self-compacting concrete were evaluated and the lateral formwork pressure exerted by the freshly mixed self-compacting concrete was measured and analyzed. An original test setup was developed for the determination of the lateral pressure on the square column formwork with pressure measurements carried out using six strain gauge pressure transducers, which was adequate for heavyweight concrete mixture testing. Self-compacting concrete mixtures containing a magnetite aggregate or blends of serpentine and magnetite aggregates with a slump flow of at least 550 mm were developed. The lateral pressure on the formwork was directly proportional to the density of the self-compacting heavyweight concrete mixes. The maximum values of the lateral pressure recorded in the test at a casting speed of 1.5 m/h did not exceed 27 kPa and 55% of hydrostatic pressure. Concrete mixtures with basalt, magnetite, and magnetite/serpentine blended aggregates were found to develop sufficient shear strength for proper stability during casting.

INFLUENCE OF METAKAOLIN ON PROPERTIES OF CONCRETE MODIFIED WITH POLYCARBOXYLATE ADMIXTURE FOR RIGID PAVEMENT REPAIR

Abstract. The effect of partial cement replacement with high-activity metakaolin on the strength, frost resistance, shrinkage and abrasion resistance of concrete modified with polycarboxylate admixture MasterGlenium SKY 608. Portland cement CEM II/A-S 42.5 (ПЦ II/А-Ш-500) with partial metakaolin replacement 15 kg (3.75 %) and 30 kg (7.5 %) was used for concrete preparation. The amount of superplasticizer in all studied compositions was 1.2% of cement weight. Slump of concrete mixtures was 6…7 cm. It was found that with increasing amount of metakaolin W/C ratio of mixtures increased slightly. The early compressive and flexural strength (at the age of 2 days) of the composition without metakaolin was higher than similar indicators with partial cement replacement with the active mineral admixture. It is worth noting the positive effect of increasing the metakaolin amount on early strength, because the composition with 30 kg metakaolin had strengths higher at 2 days of in difference to the composition with 15 kg metakaolin. It is necessary to note high frost resistance of all obtained concretes. Its grade of frost resistance reached F200 (evaluated according to the method for road concrete), which is equivalent to the grade F600 for structural concrete. Abrasion resistance was in the low range (0.30-0.31 g/cm2), total shrinkage does not exceed 0.28 mm/m, which in combination with high frost resistance has a positive effect on the durability of concrete mixtures for rigid pavements repair.

The Effect of the Composition of a Concrete Mixture on Its Volume Changes.

The presented research aims to clarify the specific effect of the individual components of concrete with Portland cement CEM I 42.5 R on the volume changes of concrete. The effect of the filler component was evaluated from the point of view of the composition and type of aggregate (crushed versus mined) and from the point of view of the mineralogical composition of the aggregate. Concrete formulas with a maximum aggregate grain size of 16 and 22 mm were assessed. The effect of the binder component on the shrinkage of the concrete was monitored on the concrete mixtures produced using the same aggregate and maintaining the same strength class of concrete, C 45/55. The effect of the addition of finely ground limestone, finely ground granulated blast furnace slag and coal high-temperature fly ash was monitored. It was found that the maximum aggregate grain and the type of grading curve do not have a significant effect on the volume changes of concrete. Concretes with mined aggregates showed lower shrinkage than concretes with crushed aggregates. The most significant is the effect of the type of aggregate on the volume changes in the first 24 h. Mineral additives have a positive effect on the elimination of the volume changes of concrete, while the addition of high-temperature fly ash proved to be the most suitable.

Design of slag cement, activated by Na (K) salts of strong acids, for concrete reinforced with steel fittings

This paper proposes a technique to prevent the corrosion of steel reinforcement in concrete based on slag cement (SC) activated by Na(K) salts of strong acids (SSA) in the composition of by-pass cement kiln dust (BP). The technique implies using additional modifiers in the form of the Portland cement CEM I 42,5 R and the calcium-aluminate admixture (CAA) С3А∙6H2O.It is shown that adding the Portland cement contributes to enhancing the intensifying influence of BP on the SC hydration, accompanied by an increase in the strength of artificial stone. This effect is predetermined by the formation of hydrosilicates in hydration products with an increased crystallization degree in the form of CSH(I) and C2SH(A).Modifying SC with CAA ensures the intensive formation of low-soluble AFm phases in the composition of hydration products, aimed at reliable binding the SSA anions (Cl-, SO42-) that are aggressive to steel reinforcement.The study result has established the possibility to produce SC, activated by SSA, when using BP, the Portland cement, and CAA. Mathematical methods to plan the experiment were applied to produce an SC composition of "granulated blast furnace slag – BP – Portland cement – CAA", characterized by a strength class of 42.5 and a molar ratio of Cl-/OH- in a porous solution not exceeding 0.6. The resulting properties predetermine the feasibility of using SC in steel-reinforced concrete.The relevance of this work is due to the modern trends in the development of the construction industry. The introduction of cement that contains mineral additives, in particular granulated blast furnace slag, contributes to improving the environment by reducing СО2 emission. The use of such cement as a base of steel-reinforced concrete ensures the increase in their functionality and durability

Możliwość zastosowania mieszaniny popiołu lotnego krzemionkowego i wapiennego do produkcji cementu portlandzkiego wieloskładnikowego CEM II/B-M (V-W) 52,5

The paper analyses the properties of Portland-composite cement CEM II/B-M (V-W) prepared by addition of mixture of siliceous and calcareous fly ashes – in percentage proportion of 20:0, 10:10, 20:10 or 15:15 – to Portland cement CEM I 42.5R. Blaine’s surface area of cements equalled 4000±100 cm2/g. Hydration heat, standard consistency, initial setting time, soundness and compressive strength were analysed in the paper. Partial replacement of siliceous fly ash with calcareous fly ash in cement gives a Portland-composite cement CEM II/B-M (V-W) of strength class 52.5N or even 52.5R, if the percentage proportion of siliceous to calcareous fly ash is 20:10.

Temperature Influence on Ordinary Concrete Modified with Fly Ashes from Thermally Conversed Municipal Sewage Sludge Strength Parameters.

Concrete is the most commonly used structural material, without which modern construction could not function. It is a material with a high potential to adapt to specific operating conditions. The use of this potential is made by its material modification. The aim of the performed investigations was the assessment of rational application possibilities of fly ashes from thermally conversed municipal sewage sludge as an alternative concrete admixture. A concrete mix was designed, based on the Portland cement CEM I 42.5R and containing various quantity of ash, amounting to 0–25% of cement mass. The samples were conditioned and heated in a furnace at the temperature of 300 °C, 500 °C, and 700 °C. Physical and chemical properties of the ashes as well as utility properties of the concrete, i.e., density, compressive strength after 28, 56, and 90 days of maturation, frost resistance, and compressive strength in high temperature were determined. The tests were performed at cubic samples with 10 cm edge. The replacement of a determined cement quantity by the fly ashes enables obtaining a concrete composite having good strength parameters. The concrete modified by the fly ashes constituting 20% of the cement mass achieved its average compressive strength after 28 days of maturation equal to 50.12 MPa, after 56 days 50.61 MPa and after 90 days 50.80 MPa. The temperature growth weakens the composite structure. The obtained results confirm the possibility of waste recycling in the form of fly ashes as a cement substitute in concrete manufacturing.

Interactive Relationship between Cementitious Materials and Acid Mine Drainage: Their Effects on Chromium Cr(VI) Removal

Elevated hexavalent chromium (Cr(VI)) levels in pervious concrete may undermine its successful application in water treatment. Portland cement CEM I 52.5R (CEM I), coal fly ash (FA), natural zeolite and ground granulated blast-furnace slag (GGBS) were evaluated as adsorbents for removal of Cr(VI) from acid mine drainage (AMD). Adsorption experiments were conducted at dosages of 6, 10, 30 and 60 g of adsorbent in 200 mL of AMD, while the mixing contact time was varied from 15 to 300 min. It was found that the use of CEM1 and FA adsorbents strongly increased the Cr(VI) concentration in AMD. Conversely, zeolite and GGBS removed up to 76% and 100% of Cr(VI) from AMD, respectively, upon their use at dosages of at least 10 g of the adsorbent. Freundlich isotherm was found better fitted with a high correlation coefficient (R2 = 0.998 for zeolite and 0.973 for GGBS) than to the Langmuir model (R2 = 0.965 for zeolite and 0.955 for GGBS). Adsorption and ion exchange seem to be active mechanisms for the Cr(VI) removal. These results suggest that zeolite and GGBS can be considered as partial cement replacement materials for effective reduction or removal of Cr(VI) from the treated water.

Reuse of Heat Resistant Glass Cullet in Cement Composites Subjected to Thermal Load.

The article describes the possibility of using waste glass cullet as an alternative aggregate for the production of cement composites. Three concrete mixes based on Portland cement CEM I 42.5 R with different contents of recyclate were designed. Borosilicate glass cullet was introduced into the batch by reducing the content of natural aggregate by 0%, 2.5% and 7.5%. Apparent density, water absorption and compressive strength at elevated temperature were measured. The temperature distribution, in cubic samples, was followed by thermocouples. The elements were heated in a special furnace at the temperatures of 200 °C, 400 °C, 600 °C and 800 °C. The composite topography and phase composition were observed using X-ray energy scattering electron microscopy. The results show that the appropriate modification of the cement composite with 2.5% heat-resistant glass cullet improves both the thermal and mechanical properties. Compressive strength reaches an average value of 48.6 MPa after 28 days. The increase in temperature weakens the structure of the composite. It was found that the obtained cement composite has good physico–chemical properties. The research results are presented in the article.

Impact of maturation conditions for concrete on its compressive strength

This paper aims to present the results of compressive strength tests of concrete specimens, prepared according to two recipes, after 2, 7 and 28 days of maturing in four different environments. The concrete specimens had the same w/c ratio, the same amount of aggregate of particular fractions, the addition of a superplasticizer, but they differed in the cement type. In one recipe, the Portland cement CEM I 32.5R was used, in the other – pozzolanic ash cement CEM IV/B(V) 32.5R-LH/NA. Concrete specimens with dimensions of 100 x 100 x 100 mm made according to both recipes were placed in individual ripening environments: in cuvettes with water, soaked and wrapped with construction foil, left in room conditions in the laboratory, placed outside the laboratory and being exposed to the atmospheric conditions. The obtained compressive strength results confirmed that the best way of curing concrete is the wet cure (in cuvettes with water). It has been proven that the choice of proper curing method is key in terms of compressive strength.

In vitro and in situ tests to evaluate the bacterial colonization of cementitious materials in the marine environment

Civil engineers have a responsibility to take measures to protect marine biodiversity by selecting more bioreceptive construction materials in the design of marine infrastructure, for better biodiversity conservation. In this study, it was shown that pre-carbonation of cementitious materials accelerates their bacterial colorization by lowering the pH of their surface. It has been shown both in the laboratory and in-situ tests that the bacterial colonization of cementitious materials is influenced by the pH and the type of cement. By comparing the bacterial colonization of Portland cement mortars, CEM I, and slag cement, CEM III, mortars, it was found that the CEM III mortars are more bioreceptive than the CEM I mortars. This study presented and verified a novel experimental laboratory approach which can be used to evaluate the bacterial colonization (bioreceptivity) of cementitious materials in marine environment. The approach could be taken up in future recommendations to enable engineers to eco-design more eco-friendly marine infrastructure and develop green-engineering projects.

Air Permeability of Air-Entrained Hybrid Concrete Containing CSA Cement

This paper presents the results of research on series of concrete prepared with Portland cement CEM I 42.5R, with partial replacement of this cement with calcium sulfoaluminate cement. In part of the series, an air-entraining admixture was used. It was assumed that the mixture must remain workable for at least 45 min and to ensure that citric acid as the setting retarder was used. Compressive strength tests after 2, 7, 28, 56 and 90 days, tensile splitting strength test and sorptivity test after 28 days were performed. After 56 and 90 days, the moisture content of the specimens was determined, and Torrent air permeability was tested. Freeze-thaw scaling resistance was also investigated. It was found that the addition of 15% and 30% calcium sulfoaluminate cement results in a significant reduction in the relative humidity of the concrete, after storage under air-dry conditions and an increase in air permeability. The series with 30% calcium sulfoaluminate cement in the binder, regardless of aeration, showed significantly lower resistance to cyclic freezing in the presence of salt. A clear correlation between sorptivity, air permeability and surface scaling was not found. On the basis of a multi-criteria evaluation of the tested concrete and performed Performance Index calculations, the best parameters were achieved by concrete series C30-4.5.

A Review on Raw Materials and Curing Methods Applied in Production of Ultra High Performance Concrete

Ultra high performance concrete (UHPC) refers to cement based materials exhibiting high compressive strength, tensile strength and excellent durability. This paper reviews the raw materials and curing methods currently applied in UHPC manufacturing process. Raw materials, preparation techniques and curing methods have significant influence on properties of UHPC. The use of very high cement content, high strength cement and silica fume may improve the strength and compactness but increase the production cost. The use of high temperature curing leads to denser microstructure and better performance than room temperature curing and water curing do, but obviously limits its application of UHPC. Thus, preparation of UHPC using widely and locally available raw materials such as ordinary Portland cement CEM Type 1 42.5N and common technology such as room temperature curing are trends in production of UHPC.

Mechanisms Accompanying Chromium Release from Concrete.

The use of mineral additives from the power and metallurgy industries in the production of building materials still raises questions about the ecological safety of such materials. These questions are particularly associated with the release of heavy metals. The article presents research related to the leaching of chromium from concretes made of Portland cement CEM I and slag cement CEM III/B (containing 75% of granulated blast furnace slag). Concrete was evaluated for leaching mechanisms that may appear during tank test over the long term (64 days). It has been presented that the dominating process associated with the leaching of chromium from both types of concrete is surface wash-off. Between the 9th and 64th day of the test, leaching of Portland cement concrete can be diffusion controlled. It has been proven that the participation of slag in the composition of concrete does not affect the level of leaching of chromium into the environment from concrete.

Suitability of Palm Frond Waste Ash as a Supplementary Cementitious Material

There has been a growing interest in using agricultural waste in concrete construction lately, because of environmental friendliness, resource conservation and economic considerations. Laboratory experiments were conducted to examine the possibility of using palm frond waste ash, as an additive in cement-based composites. The parameters investigated included the effect of palm frond waste ash at 10%, 20%, and 30% admixing levels by weight of cement, on normal consistency and setting times of cement paste, flow, compressive and flexural strength of mortar at 7, 28, 56, and 90 days, and chloride ion permeability of mortar at 28 and 90 days. Similar experiments were also performed on commercially available mineral admixture such as F type fly ash for comparison purposes. Palm frond waste ash additions to portland cement (PC) mortars somewhat increased the water required for normal consistency, prolonged the setting times, marginally lowered the workability, and improved considerably the compressive strength and chloride ion permeability at 28 and 90 days compared to control mixes without ash. Test results indicated that, up to 30% of palm frond waste ash can be added to PC cement mortar without compromising the strength and durability properties and compare fairly well with similar test results reported on a commercial admixture for concrete such as F type fly ash.

Ladle Slag as an Admixture in Cement Composites

The research was dealing use of ladle slag and its impact on the physical and mechanical parameters of hardened cement composites. The goal was to find a suitable percentage share of ladle slag used as an admixture. The results of compressive strength tests show the possibility of replacement of a significant amount of cements with a specific secondary product. A decrease in compressive strength of about 8% after 28 days has to be taken into account when using Portland cement CEM I 42.5R and a 10% replacement with ladle slag.

The Properties of Concrete Based on Steel Slag as a By-Product of Metallurgical Production

This article presents the results of research on the use of unstable steel slag with a fraction of 0/8 mm as a 100% substitute for natural aggregate in concrete production. Two types of cements were used for the production of concrete: Portland cement CEM I 42.5N and hybrid cement H-CEMENT. Both of these cements were produced by the company Považská cementárna, a.s., Ladce. The main objective of this study was to assess the suitable type of binder to be combined with unstable steel slag in the production of concrete composite. The prepared concrete was used to test the properties of a fresh concrete mix, i.e. its consistency and bulk density. Hardened concrete was used to test the strength and deformation properties, including cube strength after 3, 7, 14, 21, 28 and 90 days, as well as prism strength after 28 days. The static modulus of elasticity was determined using prisms after 28 days of age of the test specimens. Our attention was also focused on determining the class of leachability of the concretes based on steel slag with CEM I 42.5N and H-CEMENT. The durability of concrete prepared on the basis of steel slag was tested in an environment with increased temperature and pressure. The results of the strength characteristics tests show a difference between the 28-day average cube strength of concrete using CEM I 42.5N and H-CEMENT (34.6 MPa and 29.1 MPa), while after 90 days, the average cube strength value stabilized at about 38 MPa. The average values ​​of the static modulus of elasticity when using CEM I 42.5N and H-CEMENT are almost identical, achieving values ​​of 32.5 GPa and 32.8 GPa, respectively. Concrete based on steel slag with CEM I 42.5N and H-CEMENT can be included in leachability class IIb. The results of the durability test of concrete based on steel slag in an environment with increased temperature and pressure confirmed the use of H-CEMENT hybrid cement from the company Považská cementáren, a.s., Ladce, as a suitable binder. .

Optimization of cementitious composite for heavyweight concrete preparation using conduction calorimetry

The present work investigates the hydration heat of different cement composites by means of conduction calorimetry to optimize the composition of binder in the design of heavyweight concrete as biological shielding. For this purpose, Portland cement CEM I 42.5 R was replaced by a different portion of supplementary cementitious materials (blast furnace slag, metakaolin, silica fume/limestone) at 75%, 65%, 60%, 55%, and 50% levels to obtain low hydration heat lower than 250 j g−1. All ingredients were analyzed by energy dispersive X-ray fluorescence (EDXRF) and nuclear activation analysis (NAA) to assess the content of major elements and isotopes. A mixture of two high-density aggregates (barite and magnetite) was used to prepare three heavyweights concretes with compressive strength exceeding 45 MPa and bulk density ranging between 3400 and 3500 kg m−3. After a short period of volume expansion (up to 4 h), a slight shrinkage (max. 0.3°/°°) has been observed. Also, thermophysical properties (thermal conductivity, volumetric specific heat, thermal diffusivity) and other properties were determined. The results showed that aggregate content and not binder is the main factor influencing the engineering properties of heavyweight concretes.

Admixture tuning for high‐performance concrete for the production of novel precast pre‐stressed long‐span girders for highway overpasses

AbstractThe improvements observed in concrete technology in the last decades, namely the production of Portland cement CEM I 52.5 R, the development of third generation super‐plasticizers, and the commercialization of additions with high pozzolanic properties, turned possible the development of new concrete products using high performance concrete (HPC). Nevertheless, their implementation in the production process of the conservative precast concrete industry is not yet a reality. In this paper, the development and characterization of a HPC exhibiting high workability in the fresh state and high compressive strength in hardened state is presented. This HPC aims at producing, on a competitive basis, precast pre‐stressed long‐span girders for highway overpasses. For this reason, the main goal was to maximize the abovementioned properties but using the constituents available at the concrete precast company supporting the research. A set of different commercial admixtures was gathered and their influence on both compressive strength and workability of concrete was experimentally investigated. Results show that the compatibility between the admixture and the cementitious material is of paramount importance. By selecting the best type of the considered super‐plasticizers and by optimizing its dosage, it was possible to increase the workability from class S1 to S5 and, simultaneously, increase the compressive strength in circa 50%, up to 120 MPa, at 28 days of age.

Effect of the amount of river sediment on the basic properties of cement mortars

According to current legal regulations, bottom sediment in watercourses containing heavy metals are considered dangerous to the environment and should be properly managed after extraction. Due to the well-known excellent ability of the products of cement hydration to immobilize heavy metals, the possibility of utilizing this type of waste products in cement composites was preliminary tested. For this purpose, basic research was carried out on the technological and mechanical characteristics of binders containing sediment from one of the rivers located in Lesser Poland. Standard mortars made of Portland cement CEM I and river sediment dried at 105°C were used for the tests. This supplement replaced cement in the amount of 10%, 20%, 30% and 40% by weight. The technological properties such as: water demand, setting time, consistency and mechanical properties were verified. Compressive and tensile strength at bending of hardened mortars were tested at different curing periods, i.e. after 14, 28 and 90 days. The obtained test results confirm that the fraction of river sediment in the binder in the amount of 10% generally does not adversely affect the properties of mortars, however, its greater amount is reflected in changes in the technological features and in a clear reduction of mechanical properties of the tested mortars.