Properties Of Cement Concrete Research Articles

Comprehensive dielectric model of cement concrete including frequency and temperature

The dielectric properties of cement concrete are not only related to the dielectric properties and volume ratio of each component, but also related to frequency and temperature. In order to analyse these influencing factors, a dielectric constant test was done in the laboratory. Experimental results show that the dielectric constants decrease linearly with increase of temperature and decreases exponentially with the increase of frequency. Based on the experimental rules, a new dielectric model including frequency and temperature is established and verified by experiments. The verification results show that the calculation accuracy of the comprehensive dielectric model after considering the influence of frequency and temperature is improved by 25.5%, which meets the requirements of engineering detection accuracy. The model is applied to engineering practice, and the calculation methods of pavement structural layer thickness and moisture content are developed. The results show that the comprehensive dielectric model established in this paper has smaller error and higher accuracy. Using this dielectric model, the data conversion between different frequency and temperature can be achieved. The research results of this paper can provide a reference and basis for the quality evaluation of concrete structures.

Durability and mechanical properties of cement concrete comprising pozzolanic materials with alkali-activated binder: A comprehensive review

The disintegration of concrete structures made of ordinary Portland cement (OPC) is a worrying topic of increasing significance. The trend for reusing waste products or industrial by-products to reduce the amount of OPC in concrete constructions has become an important task for industries and research institutions. Although OPC is an essential ingredient for concrete and is immensely popular, it greatly ‎contributes to the release of a massive quantity of CO2 into the atmosphere. To decrease the ‎increasing CO2 emission, scholars and researchers in the construction industry and ‎academic institutions have exerted efforts to adopt alternative sustainable binders using ‎pozzolanic materials, such as metakaolin, fly ash, slag, rice husk ash, and ‎palm oil fuel ash, combined with alkali-activator (AA). Many researchers have ‎stated that AA alumina-silicate (Al2SiO2) materials can produce convincing mechanical ‎and durability properties, such as compressive strength, splitting tensile strength, and ‎modulus of elasticity, in cement concrete at an early age with low CO2 emission and ‎energy consumption. Most researchers have reported that concrete containing pozzolanic materials and alkali-activated binder (AAB) has better durability than conventional concrete, while others call for further studies. According ‎to previous studies, this research assesses the present studies on the mechanical and ‎durability properties of cement concrete produced from the AAB related to the ‎pozzolanic materials. Furthermore, few possible studies have been recommended in the ‎future‎.

Improvement of CO2-Cured Sludge Ceramsite on the Mechanical Performances and Corrosion Resistance of Cement Concrete.

The application of CO2 curing on sludge ceramsite may improve its mechanical properties, and then increase the corresponding corrosion resistance. In this study, the influence of CO2-cured sludge ceramsite on the strength and long-term properties of cement concrete is investigated. CO2 curing time ranges from 0 h to 2 d. The cylinder compressive strength and water absorption rate of CO2-cured sludge ceramsite are first determined. Additionally, the flexural and compressive strengths, the chloride permeability and the freeze—thaw damage, as well as the corresponding thermal conductivity of cement concrete, are tested. Furthermore, the corrosion resistance of reinforcement inner-sludge-ceramsite cement concrete is measured. Finally, the scanning electron microscope photos of sludge ceramsite are obtained. Results show that the cylinder compressive strength of CO2-cured sludge ceramsite is 15.1, ~34.2% higher than that of sludge ceramsite. Meanwhile, the water absorption rate of CO2-cured sludge ceramsite is 39.6, ~82.4% higher than that of sludge ceramsite. The compressive strength and the flexural strength of cement concrete with CO2-cured sludge ceramsite are 11.4 and 18.7, ~21.6% and ~31.5% higher than the cement concrete with sludge ceramsite, respectively. The resistance of NaCl freeze—thaw cycles, determined by comparing the mass loss rate and the loss rates of mechanical strengths, is effectively improved by CO2 curing, while the thermal conductivity of cement concrete is decreased by CO2 curing. The corrosion resistance of inner reinforcement is improved by the application of CO2 curing on sludge ceramsite.

Controlled impacts for structure formation and properties of cement concretes

Objective. The paper considers controlled effects on changes in the properties of components and the control effect of technological methods and techniques for obtaining composite building materials with a set of specified properties.Method. Methods of mechano-physical, physicochemical, nanotechnological influence were applied.Result. The system-structural approaches are systematized and generalized by control actions at the stage of structure formation, technological stages, formation of the optimal structure and properties of cement concrete. The physicochemical principles and mechanisms of structure formation are given, based on establishing the role of controlling the mechano-physical, physico-chemical, nanotechnological methods of influencing the cement-water system. The possibility of controlling structural transformations in binder systems, including through the use of technological influences, has been revealed.Conclusion. The implementation of the impacts on the components of cement concretes will ensure the targeted design of the structures of modern building materials.

ASSESSMENT OF PHYSICAL AND MECHANICAL PROPERTIESOF ROAD CEMENT CONCRETE PREPARED ON MAGNETIC WATER

Statement of the problem. In recent years, in all civilized and highly developed countries, there has been a growing demand for the construction of roads and highways with rigid pavements that provide a satisfactory susceptibility to increasing dynamic loads from vehicles. For road cement concrete, the issue of effective and simplified application of the operation of magnetizing cement mixing water by using microwave radiation units remains relevant and urgent. In this case, it is necessary, first of all, to assess the variability of the strength properties of cement concrete and the mobility of the cement concrete mix on magnetized water. Results. The indicators of the strength of road cement concrete and the mobility of the cement concrete mixture when using in the process of its manufacture magnetized water through the useof a microwave radiation installation have been investigated. The studied factors were the powerof electromagnetic radiation and the time of its exposure during the magnetization of water. The application of the theory of mathematical planning of the experiment made it possible to obtain the corresponding regularities in the form of regression equations.Conclusions. The use of magnetized water in the production of cement concrete mixture has shown a positive effect in terms of ensuring increased strength of road cement concrete. At the same time, a decrease in its mobility requires a revision of the technological modes of laying and subsequent compaction.

Influence of Ceramsite with Assembly Unit of Sludge and Excavated Soil on the Properties of Cement Concrete.

The application of sludge in the manufacture of ceramic material provides an outlet for waste disposal. In this study, we aimed to produce a new lightweight aggregate applications in concrete. The influence of burning temperature on the ignition loss rate, cylinder compressive strength, and the water absorption rate of ceramsite mixed with sludge and excavated soil was investigated. The slump flow, apparent density, and mechanical strength (flexural and compressive strengths) of cement concrete with ceramsite were determined. Moreover, the chloride ion permeability coefficient and the thermal conductivity were tested. Finally, scanning electron microscopy, X-ray diffraction, and thermal analysis were applied to analyze the mechanisms of the properties of ceramsite. Results show that the ignition loss rate and the burning temperature are in a quadratic relationship. The cylinder compressive strength shows a positive quadratic relationship with the burning temperature. However, the water absorption rate negatively correlates with the burning temperature. The addition of sludge can increase the ignition loss rate and cylinder compressive strength of ceramsite. Meanwhile, the effect of sludge on the water absorption rate is the opposite. Ceramsite decreases the slump flow and the apparent density of cement concrete. Cement concrete with 10% ceramsite shows the highest mechanical strength and the lowest chloride ion migration coefficient. Correction of the chloride ion migration coefficient and the content of ceramsite was performed as an exponential equation. Ceramsite exerts a negative effect on the thermal conductivity of cement concrete. Concrete with sludge ceramsite shows higher slump flow, apparent density, mechanical strength, and resistance to chloride ion penetration and thermal conductivity than concrete sludge with clay ceramsite. The mullite content of sludge ceramsite is higher than that of clay ceramsite. Additionally, sludge ceramsite exhibits a denser structure than that of clay ceramsite.

The Performance of Concrete Made with Secondary Products-Recycled Coarse Aggregates, Recycled Cement Mortar, and Fly Ash-Slag Mix.

The properties of cement concrete using waste materials—namely, recycled cement mortar, fly ash–slag, and recycled concrete aggregate—are presented. A treatment process for waste materials is proposed. Two research experiments were conducted. In the first, concretes were made with fly ash–slag mix (FAS) and recycled cement mortar (RCM) as additions. The most favorable content of the concrete additive in the form of RCM and FAS was determined experimentally, and their influence on the physical and mechanical properties of concrete was established. For this purpose, 10 test series were carried out according to the experimental plan. In the second study, concretes containing FAS–RCM and recycled concrete aggregate (RCA) as a 30% replacement of natural aggregate (NA) were prepared. The compressive strength, frost resistance, water absorption, volume density, thermal conductivity, and microstructure were researched. The test results show that the addition of FAS–RCM and RCA can produce composites with better physical and mechanical properties compared with concrete made only of natural raw materials and cement. The detailed results show that FAS–RCM can be a valuable substitute for cement and RCA as a replacement for natural aggregates. Compared with traditional cement concretes, concretes made of FAS, RCM, and RCA are characterized by a higher compressive strength: 7% higher in the case of 30% replacement of NA by RCA with the additional use of the innovative FAS–RCM additive as 30% of the cement mass.

Geopolymer concrete with metakaolin for sustainability: a comprehensive review on raw material's properties, synthesis, performance, and potential application.

In the last three decades, the gigantic demand for sustainable and environmentally friendly concrete with reduced environmental footprints has resulted in the development of low carbon concretes such as geopolymer concrete. Metakaolin which is commonly used as an admixture or partial replacement of cement owing to its most effective pozzolanic properties, which improve the microstructure and strengthen the mechanical and durability properties of cement concrete, has been investigated as a precursor in geopolymer concrete. Several studies have been conducted to comprehend the effect of metakaolin as an additive in geopolymer mortar and concrete prepared with various aluminosilicate sources as precursors such as fly ash and rice husk ash to enhance geopolymerization, densify microstructure, and elevate durability. The present paper recapitulates these investigations primarily concentrating on the various properties of metakaolin-based concrete. The effect of various factors such as alkali content, solids/liquids ratio, alkali reactant ratio, molar ratio, water content, and curing regime has been compiled. Most of them revealed that metakaolin is used as a precursor and yields better geopolymer products. XRD studies reported the peaks demonstrating the development of enhancement in hydration products in comparison to other precursors. Examination of SEM graphs reveals that the addition of a smaller quantity of silica-rich materials densifies the microstructure of geopolymers and produces higher mechanical strength. Durability studies reveal that metakaolin geopolymers possess better water resistance, thermal resistance, and anti-corrosion properties. The possible applications of metakaolin-based geopolymeric materials are also pointed out. The comprehensive knowledge presented here is expected to support the prospective researchers to decide their future course of the research area. Graphical abstract.

An investigation on fresh state properties of cement paste and concrete with GGBS and waste paper sludge ash

The utilization of supplementary binding material is well accepted because of the many potential enhancements within the concrete composite and the overall construction economy. This paper mainly emphasizes on fresh state properties of cement concrete with grounds granulated blast furnace slag (GGBS) and waste paper sludge ash (WPSA), as concrete behavior is complex-heterogeneous with time-dependent properties. Again fresh state properties of concrete are very important as resulting hardening properties are based on fresh properties of concrete. The analysis aimed to develop an associate economic binder from waste products that might have applications within the production of concrete. As GGBS contains about 30% SiO2 and 58% CaO and, respectively 28% and 30% for WPSA, which is near to cement and can produce binder material. This paper investigates fresh state properties of concrete made with different proportions of waste paper sludge ash (WPSA) and grounds granulated blast-furnace slag (GGBS) as cement replacement, such as standard consistency, initial and final setting time, soundness test, and slump cone test has carried out. For that Cement is replaced with partial replacement of GGBS and waste paper sludge ash in the proportion of cement: WPSA:GGBS ratios 50:5:45, 50:10:40, 50:15:35, 50:20:30, 50:25:25 are made and their effect on properties have been checked. Also, the XRD and SEM analysis of materials has been administrated during this paper. From the test, it has been observed that for only GGBS as cement replacement, the water quantity require is less and there is segregation of water, while it is not happening in the case of combined WPSA and GGBS as cement replacement. Water quantity require for only WPSA as cement replacement is large as compared to GGBS used as cement replacement, as WPSA is porous, can overcome with the combined use of WPSA and GGBS along with one of the good superplasticizers like polyether-polycarboxylates (PCE).

Effect of nanosilica on drying shrinkage and creep properties of cement concrete

The microstructure and time dependent properties of nanosilica (nS) added high performance concrete (nS-HPC) were investigated, and a comparison of these properties with those of microsilica (mS) added high performance (mS-HPC) concrete and a reference concrete (RefCon) are presented. 3% colloidal nS and 7.5% powder mS were used to make nS-HPC and mS-HPC, respectively. The scanning electron microscopic image of the 90 days’ nS-HPC revealed that the quantity of Ca(OH)2 present was almost negligible and the concrete attained a finer and compact microstructure with finer C-S-H as compared to that of other two concretes. The creep and drying shrinkage of the nS-HPC were found to be higher than those of RefCon and mS-HPC. However, the observed drying shrinkage of all the concrete mixes was found to be conforming with the estimates made from Indian Road Congress (IRC):112-2011 model, while on the other hand, the creep coefficients of mS-HPC and nS-HPC was found to be higher than the corresponding estimated creep coefficients, and the same were found to be higher by 13.3% and 18.2%, respectively, at 100 days. The increase in drying shrinkage and creep of both the high-performance concretes (HPC) than that of RefCon may be attributed to higher amounts of gel water present in the finer C-S-H produced due to pozzolanic action. The results from the study indicates suitability of nS-HPC for construction of bridge structures. Copyright © 2017 VBRI Press.

Experimental Study on Engineering Properties of Cement Concrete Reinforced with Nylon and Jute Fibers

The use of synthetic fiber and natural fiber for concrete production has been continuously investigated. Most of the materials have become popular for their higher flexibility, durability, and strength. However, the current study explores the engineering properties of cement concrete reinforced with nylon and jute fibers together. Varying proportions and lengths of nylon and jute fibers were utilized in the concrete mixture. Hence, the combined effects of nylon and jute fibers on workability, density, water absorption, compressive, tensile, flexural strength, and drying shrinkage of concrete were investigated. Results showed that concrete with 1% of nylon and jute fibers together by the volume fraction showed a maximum enhancement of the compressive strength, split tensile strength, and flexural strength by 11.71%, 14.10%, and 11.04%, respectively, compared to the control mix of concrete at 90 days. However, the water absorption of concrete increased with increasing nylon and jute fiber contents. The drying shrinkage of concrete decreased with the addition of nylon and jute fibers together after 90 days. Thus, the sparing application of both nylon and jute fiber as discussed in this study can be adopted for concrete production.

RELIABILITY CRITERION FOR CALCULATION OF THE OPTIMUM DRIVING SPEED ON ROAD IN WINTER

The problem of eliminating winter slips on paved roads is a topical issue today. The paper analyzes the results of tests using traditional (chloride) and non-traditional chemical reagents and their influence on the strength properties of cement concrete. In general, the formation of slipperiness on the surface of cement concrete pavements does not differ from asphalt concrete, because cement concrete can have a high moisture capacity. The pores of cement concrete readily allow moisture to penetrate, and with decreasing air temperature significant ice formation can occur in the pavement. This kind of slipperiness is very dangerous. In appearance they look like a dry coating, in fact, they penetrate deeply into the body of the coatings. Not every chemical reagent can act positively to reduce moisture. And also this process in climatic zones with a sharply continental climate especially exacerbates the likelihood of peeling of cement stone, followed by crumbling of concrete (peeling) and loss of strength due to the low stability of this material

Effect of polycarboxylate ether-based superplasticizer dosage on fresh and hardened properties of cement concrete

Ready-mix concrete nowadays is available almost everywhere in the country. RMC plants are indispensably using high-range water-reducing admixtures namely, sulfonate naphthalene formaldehyde condensate, and Polyether polycarboxylate, for making standard cement concrete. These admixtures are used to economize the cost of concrete by reducing the quantity of water. Commonly used high range water reducer admixture, the polycarboxylate ether-based (PCE) superplasticizer has been used to investigate its influence on workability and strength of concrete by measuring slump and ultrasonic pulse velocity as well as crushing strength. The cement of grade 43 has been used in this work. This superplasticizer was added to the mix to make concrete of grade M60 by weight of cement with 0.15%, 0.25%, 0.35%, 0.45%, and 0.55% without altering the w/c ratio. Experimental results reveal that the restricted dosage of the superplasticizer provided in Plain and reinforced concrete code of practice in Indian standard, IS456:2000, restricts to 1% is on the higher side. The slump, ultrasonic pulse velocity, and crushing strength of M60 grade standard concrete with water to binder ratio of 0.40 gives the optimum dose 0.45% by weight of cement, which is quite less than the restricted quantity of dosage.

Influence of anti-ice chemicals on reduction of strength properties of cement concrete

In this article were analyzed the problems of liquidation winter slipperiness on the roads with hard surface using chemical reagents. The article analyzes the results of tests using traditional (chloride) and non-traditional chemical reagents and their influence on the strength properties of cement concrete.

Prediction and optimization of the fresh and hardened properties of concrete containing rice husk ash and glass fiber using response surface methodology

Substantial efforts are being adopted worldwide for the proper utilization of waste materials and by-products as supplementary materials to produce sustainable concrete. Rice Husk Ash (RHA) and Glass Fiber (GF) are such materials that can contribute to improve the properties of cement concrete. This study aims at predicting and optimizing the fresh and hardened properties of concrete blended with RHA as cement replacement and GF as an additional reinforcing element using Response Surface Methodology (RSM). Volumetric percentages of RHA and GF were considered as two independent variables to develop probabilistic models for slump, fresh and dry density, compressive and splitting tensile strength as desired responses. The experiments were implemented using Central Composite Design (CCD) and a good correlation was perceived between the experimental and predicted values of responses. The effect of variables on the desired properties was investigated through Analysis of Variance (ANOVA) at 95 % confidence level. The results of lack of fit test and high values of coefficient of determination (R2) ranging from 0.9359 to 0.9975 indicate the adequacy of the probabilistic model to predict the responses of blended concrete. Finally, to validate the calculated models, experiments were performed with optimized proportions of RHA (16.05%) and GF (0.08%) and desired values of slump, fresh density, dry density, 28-day compressive strength and 28-day splitting tensile strength was obtained as 41.91 mm, 2469 kg/m3, 2402 kg/m3, 28 MPa, and 3.77 MPa, respectively. All the experimental values of the desired five responses were closely matched to the optimized values indicating the efficiency of RSM to evaluate the properties of blended concrete.

Some Properties of Cement Mortar Incorporating Micro and Nano-Metakaolin Materials

There are many reasons neededfor continuous evolution in concrete technology; one of them concern on the greenhouse gas emission and depletion of natural resource as a results of high production of Portland cement. Many solutions are used to solve these problems; one of them is using cement replacement materials in concrete like metakaolin (in micro or Nano scale) which offered positive effect on the properties of cement concrete. Therefore, the main aim of this study is to evaluate and compare the effects of metakaolin (MK) and Nano-metakaolin (NMK) on some physical and mechanical properties of cement mortar. For this purpose, mortar mixes are prepared by substituting cement (by weight) with (10%) metakaolin or (1, 3, 5, and 7%) Nano - metakaolin. The amount of binder for mortar mixtures is 700 kg/m with a constant water / binder ratio of 0.33. Workability, apparent density, water absorption, compressive strength, and flexural strength of all mortar mixes are determined and compared with reference mix without any mineral admixture (0% MK or NMK). The results indicated that the performance of mortar mixes can be enhanced by metakaoline replacement. Furthermore, Nano-metakaolin has significantly positive impacts on the properties of mortar mixes which have found to be improved with increasing the Nano-metakaolin replacement, due to better pore refinement, micro filling action, and higher pozzolanic reaction. The optimum Nano-metakaolin substitution ratio (7%) causes increase in compressive and flexural strength reach to (82.6% and 59.5%), respectively compared with the reference mix, at age of 28 days.

ОБОСНОВАНИЕ ПРИМЕНЕНИЯ ПРОТИВОГОЛОЛЕДНЫХ ХИМИЧЕСКИХ РЕАГЕНТОВ НА АВТОМОБИЛЬНЫХ ДОРОГАХ С ЦЕМЕНТОБЕТОННЫМ ПОКРЫТИЕМ

In this paper, we consider the problem associated with the fight against slipperiness on roads with a hard type of road surface. It is known that on cement-concrete surfaces, the length of the braking distance is up to 10 times longer than on a snow roll formed on asphalt-concrete surfaces. This phenomenon is especially dangerous in winter, as a sharp increase in humidity (as a result of warming) significantly reduces the strength properties of cement concrete. Chloride de-icers are highly hygroscopic. Being in the pores of cement concrete, chemical solutions begin to absorb moisture from the atmosphere. In asphalt concrete, such phenomena are practically absent. Moisture, which is located in the pores of cement concrete, on its surface occurs "staining" and peeling. In the article, the authors pay special attention to the climatic conditions of Kazakhstan. The average air temperature of the coldest month on average in the Akmola region is 25-27oC, in the Eastern region-31-36oc, in the North– -26-29 OS, and in the South-3-10 OS. Annual precipitation amounts to 260-300, 340-370, 300-340 and about 150 mm, respectively. the duration of the cold period in the year varies between 6-7, 6-7, 5-6 and 3-4 months. It is climate factors that make it difficult to use chemical reagents as anti-icing materials on roads with a cement-concrete surface. This article discusses the theoretical basis for the destruction of the crystal structure of snow and ice formations from the influence of chemical reagents. They established a natural dependence of the freezing force of snow and ice formations on the impact of various types of salt solutions. Also, laboratory studies have established the effect of the concentration of salt solutions on the loss of strength of cement concrete over time.

浇筑温度和养护凝固方式对水泥混凝土性能的影响

浇筑温度和养护凝固方式对水泥混凝土性能的影响

Investigating Mechanical Properties of Sustainable Concrete Admixing Wollastonite Micro Fibre and Granite Block Cutting Waste

Due to rapid urbanization around the world, production of cement concrete has increased several times, in turn, affect the ecosystem by the depletion of natural resources and emission of greenhouse gases. In this study, a sustainable approach has been made by partially admixing ordinary Portland cement with wollastonite micro fiber and natural fine aggregate with granite block cutting waste. The mechanical characteristics of concrete samples such as compressive strength, flexural strength, density and split tensile strength were conducted to evaluate the influence of wollastonite micro fiber and granite block cutting waste on different mixes. Different concrete mixes were casted by partially substituting ordinary portland cement with constant 10% wollastonite micro fiber and fine aggregate with granite block cutting waste at different substitution level of (0%, 10%, 20%, 30%,40% and 50%) by weight. The partial substitution of wollastonite micro fiber and granite block cutting waste enhanced the mechanical properties of cement concrete.

Sustainable roadway construction: Economic and social impacts of roadways in the context of Ethiopia

Sustainable roadway construction can be defined as the optimal use of resources during the roadway life-cycle reducing the economic and social impacts. Two means of improving the sustainability of roadways are the appropriate selection of pavement types to minimize the life cycle cost of pavement and to reduce the social impacts. Thus, this work is aimed at analyzing the economic and social impacts of the Jointed Concrete Pavement in comparison to the Hot Mix Asphalt pavement from the perspective of life cycle cost analysis. To achieve the aim of the research the following tasks had been performed; Comprehend the backgrounds of life cycle assessment and life cycle cost analysis via literature review and data collection; Verify types of pavement; Analyze and Quantify structural components of pavement; Estimate agency and social costs; Perform life cycle cost analysis for each type of pavement, and finally Interpret the outputs. Results show that the life-cycle costs of the Jointed Concrete Pavement have about 90% cost advantage over the Hot Mix Asphalt pavement. This is the result of the unique properties of cement concrete which give its durability and hence lower maintenance, social cost, and longer design life. Finally, this research is expected to bring a paradigm shift and to strengthen the life cycle costs that are being considered in the overall cost of the pavement structure rather than just looking at the initial investment cost during the economic feasibility study of road projects under Ethiopian Roads Authority custody.