Types Of Admixtures Research Articles

Validation of sequential pressure method for evaluation of the content of microvoids in air entrained concrete

The suitability of the sequential air pressure method (SAM) to evaluate the quality of air entrainment in concrete mix to support prediction of durability of hardened concrete was studied. The experiments included both laboratory-produced mixes and on-site trials on mixes delivered for highway pavement construction. The fresh air content and the air void distribution was tested using the SAM apparatus. The air content and the air void characteristics in hardened concrete was tested using the microscopic analysis on polished sections. Standard fresh mix properties were also tested and the compressive strength and salt-scaling resistance of concrete was determined. Effects of type and proportion of admixtures, type of crushed aggregate, timing of SAM measurements and the method of mix consolidation were analyzed. The relationship between the SAM number and the air void characteristics in hardened concrete was critically evaluated. The relationship between SAM number and the content of microvoids (A300) is found for the laboratory mixes and confirmed with few field test results. The criterion of SAM number ≤ 0.4 is proposed for the target microvoids content A300 ≥ 1.5% and the enhanced salt scaling resistance of concrete.

Study of the Admixtures Effect on Concrete Creep Using Bayesian Linear Regression

AbstractAdmixtures are commonly used nowadays in the mix composition of concrete. These additions affect concrete properties and performance especially creep deformations. This paper shows the effect of admixtures on creep of concrete. In fact, creep deformations have prejudicial consequences on concrete behaviour; an incorrect or inaccurate prediction leads to undesirable consequences in structures. Therefore, an accurate estimation of these deformations is mandatory. Moreover, design codes do not consider admixtures’ effect while predicting creep deformations, thus it is necessary to develop models that predict accurately creep deformations and consider the effect of admixtures. Using a large experimental database coming from international laboratories and research centres, this study aims to update the Eurocode 2 creep model by considering the type and percentage of admixtures using Bayesian Linear Regression method. The effect of two types of admixtures is presented in this paper; the water reducer and silica fume.

Frost Resistance of Concrete from Innovative Air-Entraining Cements

The results of concrete tests on cements with mineral additives indicate that, despite better tightness and higher strength, there are problems with frost resistance of non-aerated concretes, even under conditions of moderate exposure to frost. In order to minimize problems with obtaining frost-resistant concrete, an attempt was made to create air-entraining cement. In this paper are presented frost resistance of concrete with air-entraining cement. The researches were carried for concretes made of multicomponent Portland, metallurgical and multi-component cements additionally differentiated by the type of air-entraining admixture (synthetic and natural) and the method of cement preparation (cement mixed together, common ground cement). There were tested internal frost resistance of concrete and a salt frost scaling of concrete.

Efficiency Assessment of Accelerating Admixtures and Cement Kiln Dust with Cooperation with Different Phase Composition Slag Blended Cements

Concrete technology involves nowadays several types of chemical admixtures. One of them is set and hardening accelerating admixtures. Main benefits of their usage are enhancement of early compressive strength and shortening of initial setting time. Unfortunately, they may cause decrease of long-term compressive strength and adversely influence durability properties of concrete. Slag blended cements with 30% and 60% of slag content were used. Ground granulated blast furnace slag (GGBFS) that is main non-clinker constituent of those cements is beneficially changing its properties. It favourably affecting long-term compressive strength, consistency and durability properties of concrete. Main drawback of slag blended cements are decrease of early compressive strength and extension of initial setting time. Both accelerating admixtures and ground granulated blast furnace slag have advantages and disadvantages that may be at least partially balanced. Slag blended cements were composed in laboratory conditions of three Portland clinkers, differing in phase composition, anhydrite as set regulating constituent and ground granulated blast furnace slag in amount of 30% and 60% of Portland clinker mass. Cements was modified with accelerating admixtures with crystal seeds and calcium nitrate as active agent and cement kiln dust in amount of 10% of the cements mass. During previous research crystal seeds and calcium nitrate were examined with CEM I, CEM II/B-S and CEM III/A, B, manufactured by one of polish cement plants. Calcium nitrate acts mainly on dicalcium and tricalcium silicate (C2S and C3S). Crystal seeds are acting physically on all cements phases by means of acceleration of C-S-H phase formation by faster crystallisation. Their performance may be similar independently on cement phase composition. Aim of this paper is to describe effectiveness of those admixtures in cooperation with CEM II/B and CEM III/A, differing in phase composition. Additionally, cements were modified with Cement Kiln Dust (CKD) and their properties were tested. Such dusts may accelerate setting and hardening of cement because of chloride and carbonate content, which are constituents of accelerating admixtures. In addition, their form of very fine powder may allow them to act similarly to crystal seeds. Initial setting time, consistency and compressive strength of mortars were examined. Tests were conducted in temperature of 20°C. Compressive strength was tested after 12, 24, 48 hours and 7, 28 and 90 days of curing in temperature 20°C in water. In most works those properties are considered separately. In order to determine efficiency of substances mentioned above the multiple-criteria decision analysis (MCDA) was made for every kind of cement. This kind of analysis allows to take examined properties as set of properties and give information about the behaviour of admixture and cement cooperation in more general terms. Criteria were defined on the basis of conducted tests and their weights were evaluated with pair analysis method. Admixture with crystal seeds was most efficient one, while Cement Kiln Dust was the least efficient.

Behaviour of a New Concrete Composition with Jaggery as Admixture

Quality of concrete is influenced by the proportion of ingredients and method of preparation in concrete production. A unique word which is used on concrete is inevitable in human life due to its properties and applications. From the ancient days lime and jiggery are used as binding materials. This review paper expressed the significance of jaggery on strength behavior of a new concrete composition. Experimentation carried out for determining strength properties of a new concrete for M20 grade nominal concrete using jaggery as admixture. Based on previous study, jaggery is an unrefined sugar product and it is easily available market; the main function of jaggery is to increase the initial setting time of concrete and it also influencing the properties of concrete. Preferably this type of admixture is used in different construction sites like deep foundations, piers and long piles. Four different percentages of admixture was chosen into the experimentation at 0, 0.25, 0.50 and 0.75% by weight of cement, finally it is accomplished that the workability of concrete is being superior with jiggery as admixture but flexural strength and shear strength of this new concrete decreased as compared with convectional M20 concrete.

Effect of the pyrolysis duration and the addition of zeolite powder on the leaching toxicity of copper and cadmium in biochar produced from four different aquatic plants

The study aimed to determine the biochar yield of four aquatic plants, the leaching toxicity of copper (Cu) and cadmium (Cd) in the biochar, and the stabilization characteristics of the biochar produced under different pyrolysis conditions (at 350 °C for 1, 2, and 3 h and absence/presence of zeolite powder). The results showed that different plant species required a different pyrolysis duration and the presence or absence of zeolite powder. The stabilization of Cu and Cd was significantly affected by the pyrolysis duration and the external materials for different plant species and different types of admixtures. Pyrolysis temperatures over 350 °C for 1 h without zeolite powder generated stable Cu and Cd in goldfish algae (Ceratophyllum demersum L.), foxtail algae (Myriophyllum verticillatum L.), and penny grass (Hydrocotyle vulgaris). Pyrolysis temperatures over 350 °C for 1 h with zeolite powder made Cu and Cd stable in water celery (Oenanthe javanica (Bl.) DC). The addition of zeolite powder during pyrolysis was possible due to the weight reduction efficiency in plants with Cu and Cd. Furthermore, the surface of the biochar with the zeolite powder showed honeycombs and a spongy porous structure. The duration of the pyrolysis had little effect on the honeycomb pore structure.

THE EFFECT OF ADDITION SILICA FUME, SUPERPLASTICIZER, AND BONDING TO REACHING HIGH QUALITY LIGHTWEIGHT CONCRETE

In this research, a lightweight concrete mixture was made with foam and made use of the remaining broken rock from the Crusher Machine process, which was washed ashes. Other added ingredients used in the mixture are Silica Fume, Superplasticizer (Admixture Type F) and Bonding. This reseach uses a mix design from Circular Letter Number: 44 / SE / M / 2015 Concerning Design Guidelines for Mixing Light Material with Foam Mortar for Road Construction, Ministry of PUPR. Trial mix variations carried out are in proportion (SF 5%; BO 0.5%), (SF 10%; BO 0.5%), (SF 5%; BO 1%), (SF 10%; BO 1% ), as well as foam agents with variations 1:20 and 1:40. The treatment process (curing) of the test object is immersed in a water bath, and the testing of the compressive strength of the test object is carried out at the age of 7 days, 14 days and 28 days. By using stone ash, lightweight concrete was obtained with an average specific gravity of 1722 kg / m3 to 1884 kg / m3. From the research results obtained the highest average compressive strength with the percentage of material that is in the variation of the SF 10% ; BO 0.5% and ratio foam (1) : water (40) only for K 190.6 kg/cm2 or FC 15.82 MPa. In each specimen the value of quality efficiency with the most optimum weight variation at SF 10% ; BO 0.5% with a coefficient value of 10.03%.

Fatigue performance of PVA fibre reinforced cementitious composite overlays

ABSTRACT Pavement maintenance and rehabilitation is as much important as the construction work itself. In this scope, applying the correct and efficient repair method is highly critical for economic and technical reasons. Depending on the damage level, many alternative repair methods exist. Using an overlay is one common method, where a new layer can be directly applied over or replace the top part of an existing pavement. This overlay can be made from asphalt or concrete as well. With the advances in the concrete technology, the long service life of concrete pavements compared to asphalt let this overlay gains importance recently. Yet, the rigid nature of concrete requires a high thickness for an overlay. In this work, Engineered Cementitious Composite (ECC) type of concrete was suggested to be used as an overlay considering its ability, with a less thickness, to reduce the reflection of the cracks from the old pavement. To testify this property, the performance of two ECC mixtures as a concrete pavement overlay was investigated under fatigue loading. Using Weibull distribution, the failure probability of these mixtures was determined, and it was shown that the mineral admixture type utilized significantly affects the fatigue performance of ECC.

Rehology and Durability of Cement Mortar by using Viscosity Modifying Admixtures

Cement mortar utilizing natural admixtures is the need of great importance for a wide scope of utilizations in the development of building structures. It is a built material for explicitapplications having superior properties like better strength, durability, and constructability. In the present consideration, create a characteristic admixture based cement mortar, admixtures like drumstick, and Ranawara resins were utilized along with normal ingredients. The nature of the natural admixture was to modify the viscosity nature of mortar. The use of natural admixtures in cement mortar enhances its properties regarding workability, strength, durability, and the economy. The extent of this paper was to investigate the effect of mineral admixtures such as Durmstick and Ranawara gums towards the execution of slab panels. Experimental results gave the effective strength on cement mortar due to the property of rheology in natural gums. This work progressively tried distinctive kinds of admixtures by casting cubes and testing them. The tests, such as sorptivity, acid test and water absorption for durability property was studied. Subsequently, the optimum result for different types of admixtures was taken to cast cement mortar slab panel along with the optimum result of admixture. Finally, the behavior of the slab panel was studied and a narrative was presented on various parameters of strength.

Enhanced autogenous healing of ground granulated blast furnace slag blended cements and mortars

In this study, the autogenous healing characteristics of cementitious materials with ground granulated blast furnace slag (GGBFS) and crystalline admixtures were investigated. The main variables were the replacement of cement by GGBFS (15–50%) and crystalline admixture types (anhydrite, Na2SO4, and Na2CO3). Isothermal calorimetry analysis was performed to evaluate the potential for crack self-healing. The water flow test was used to evaluate the autogenous healing performance after inducing cracks in 7-day aged specimens. The autogenous healing products were analyzed through scanning electron microscopy (SEM). Cumulative heat was the highest when the GGBFS replacement percentage was 15% and the crystalline admixtures were used simultaneously, and it decreased when the replacement percentage of GGBFS increased. The results of the water flow test showed that crack self-healing performance was enhanced as the replacement ratio of GGBFS was increased up to 30%. The crack self-healing performance was the highest when anhydrite and Na2SO4 were used at the same time. SEM analysis showed that the types of self-healing products affected the crack self-healing performance.

Brick and Glass Waste Valorisation in the Manufacture of Aerated Autoclaved Concrete

Autoclaved aerated concrete (AAC) is a light building material with high porosity, used to improve thermal and sound insulation of the buildings. AAC have a much better thermal efficiency than traditional masonry materials (bricks) or reinforced concrete elements; its use reduces the energy consumption (up to 7%) and consequently the carbon footprint of construction sector. The main constituents of autoclaved aerated concretes are portland cement, siliceous material (aggregate), water and different types of admixtures and additives (lime, foaming agent etc.). The aim of the research presented in this paper is to reduce the environmental impact of the technological process of ACC manufacturing; in this respect, one of the main components of AAC i.e. sand (natural raw material) was substituted with two types of inorganic waste i.e. glass (cullet) and waste brick; the sand substitution rate was comprised between 12.5-100% wt. The results indicate that both glass and brick waste can be incorporated into the autoclaved aerated concrete (AAC) structure without major modifications of apparent density (maximum 10% increase in correlation with substitution amount). For similar values of the apparent density, the AACs prepared with glass waste have higher values of compressive strength and thermal conductivity as compared with AAC with brick waste.

Effects of chemical and mineral admixtures on the foam indexes of cement-based materials

Air in cement-based materials is one of the important parameters affecting its properties in fresh and hardened states. Various types of chemical and mineral admixtures have been combined and used in cement-based materials. This makes the formation and stability of air bubble in fresh cement-based materials very complicated, and the control of air void in cement-based materials difficult. In this paper, air-related issues of cement-based materials were evaluated by foam indexes and surface tension test. The effects of mineral admixtures, including slag, fly ash and silica fume, and chemical admixtures, including superplasticizers, viscosity-modified admixtures and air-entraining admixtures on the foam indexes were studied. Results showed that surface tension is one of the factors affecting foam ability and foam stability, but not decisive one. Foam ability and foam stability of cement-based materials depend on many factors, such as types of chemical admixtures, compatibility of chemical admixtures, fineness and its chemical compositions of mineral admixtures.

Effect of Utilization of Different Type of Mineral Admixture On Fresh And Hardened Properties of Cementitious Systems

In this study, the effect of mineral admixture utilization on fresh and some hardened state properties of cement paste and mortar mixtures were investigated. For this purpose, in addition to the control mixture containing no mineral admixture, three more series of mixtures were prepared. In the first and second mixtures 30% and 10 w.t% of cement was replaced with silica fume and fly ash respectively. In the third series, cement was replaced with both of silica fume and fly ash by 30% and 10%, respectively. According to test results, fresh state properties of paste mixtures were affected by mineral admixture use positively in general. However, a reverse result was observed for the fresh state properties of mortar mixtures. Compressive strength values of the mixtures including fly ash as well as the ones including silica fume and fly ash was found to be less than that of control mixture. Nevertheless, the difference between those values reduced at the end of 90 days. Mixture including silica fume showed the highest strength value from the beginning. 90-day water absorption values of the mortar mixtures were observed to be less compared to that of control mixtures with the use of mineral admixture. The mixture having ternary binder system (including cement, silica fume and fly ash) showed better performance in terms of hardened properties. The water absorption capacity value of mentioned mixture was observed as 42% less than that of control mixture.

Identifying the Reference Time for Determining the Compressive Strength of Concrete Containing Different Types of Cements

Abstract The compressive strength of the concrete measured at 28 days is the criterion for assessing the concrete class, and these values will be acceptable precise indications for other physical and mechanical characteristics of the concrete. In addition to the factors the compressive strength of concrete varies on (such as: the characteristics and proportion of constituents, the placement conditions and subsequent treatment and testing conditions), the concrete class should also depend on the type of cement contained and the concrete strength evolution over time. Due to the fact that concretes with composite cements have a slower evolution of compressive strength and a significant strength increase after 28 days, concretes with different types of cements and mineral admixtures were tested for compression after 28 days in order to determine the reference time for such tests – and thus the concrete’s class.

Effect of retarding superplasticizers on the properties of cement paste, mortar and concrete

Chemical admixtures are becoming increasingly popular as these could improve several properties of concrete, both in plastic and hardened condition. However, improper use of admixture may lead to the inferior performance of produced concrete. Effects of admixtures dosage on the properties of cement paste, mortar and concrete were studied in this research. The most recently developed polycarboxylic ether (PCE)-based admixtures from different manufacturers were used. The trial dosages were fixed considering their properties and suppliers’ specifications. Firstly, the effect of retarding on cement setting times was evaluated using cement paste and then flow test was carried out on cement mortars to examine change in workability, i.e., superplasticizing effect with this. Compressive and tensile strength test on mortar cube and briquette samples was conducted to evaluate variation in strength with different dosage of admixture while keeping other materials’ proportions same. Finally, the dosage effect on workability (slump retention) of fresh concrete was studied for every 15-min interval up to 1.5 h. Effect of slump retention using admixture on compressive strength was also evaluated. Experimental results show that a small variation in admixture dosage changes these properties significantly. It was concluded that properties of cement paste, mortar and concrete could be improved with an optimum dosage for each particular type of admixture; however, higher or lower dosage than this may put adverse effect. Within the usable time, there might be other chemical effects that enhance/decrease the concrete performance while keeping all other quantity and parameters the same for all these concrete mixes.

Effect of Different Micro Metal Powders on the Electrical Resistivity of Cementitious Composites

The electrical resistivity is an essential parameter describing materials’ capacity to convey electric current. Normal cementitious materials display high estimation of the electrical resistivity because of their insulating nature. However, the high electrical resistivity of concrete can be reduced by a sufficient amount of electrically conductive admixture. Such an improvement is advantageous in self-sensing or self-heating concrete design. In this study, the effects of metal additives on the electrical resistivity of hardening cement paste were investigated. In the experiments, two different types of metal admixtures; copper powder and iron powder were used. Hybrid composition of copper and iron were also considered for comparisons of the electrical resistivity. A water to binder ratio of 0.35 was used. The metal powders were used in the mixtures by replacing the cement in ratio of 0%, 5%, 10%, 15% and 20% by weight. The total binder content (cement and metal additives) was always the same in the experiments. The measurements were carried out at room temperature by using two-electrode- AC method. The test results indicate that the metal cement composites with 20% of cement weight improved the lower electrical resistivity of the cement paste than plain cement paste. In addition, composites with copper powders had less electrical resistivity than those with iron powders. The reduction of electrical resistivity with an increase of metal content was steady for when of using hybrid composites better than when using metal powders alone. The Different frequency options 1 kHz, 10 kHz and 100 kHz were used to investigate the effect of impedance-frequency and phase angle-frequency of a sample test using the LCR meter. The highest current frequency available on the LCR meter, 100 kHz, was chosen to be used as the applied current frequency in all of the experiments which exhibit much lower phase angle values that can cancel the effect of change in electrical resistivity measurements.

Relationship Between Air-Content in Fresh Cement Paste, Mortar, Mix and Hardened Concrete Acc. to PN-EN 480-1 with Air-Entraining CEM II/B-V

Research results of the relationships between air-volume in air-entrained cement paste, mortar and concrete, all designed according to PN-EN 480-1 guidelines are presented in the paper. The cement paste, mortar and concrete, with w/c=0,5 ratio, were prepared using innovative air-entraining cement CEM II/B-V. The air-entraining cement CEM II/B-V was produced using two methods: mixed together with natural or synthetic aerated admixture. The air volume test of the volumetric method was carried out in case of fresh cement paste, mortar and concrete mix. Fresh concretes were evaluated in terms of stability of air entrainment and consistency for 5, 20 and 40 min. The porosity structure parameters, like summarized air-content, specific surface of air voids, air-voids spacing factor and micropores content of hardened concrete, were estimated using computer tomography with a resolution of 2-5 μm. The aim of the research was to determine the dependence between air-content of cement paste, mortar and concrete on the measurement of air-entrainment of cement paste or mortar with the same w/c ratio and type of cement, all designed according to PN-EN 480-1 guidelines. Test results proved that there is a good correlation between the measured air-content of the cement paste, mortar and concrete. Therefore, it is possible to predict the aeration of concrete on the air-entrainment of the mortar. Moreover, the porosity parameters research results indicated, that the air-entrainment of concrete is very stable. Research results indicated that the porosity of hardened concrete meets the European standards for frost-resistant concrete. Research results of the influence of air- entraining admixture type have proved, that a greater amount of micro pores in concrete is the effect of a synthetic air-entraining admixture. In concrete with synthetic entraining admixtures the air pores have smaller diameters than in concrete with natural air-entraining admixture, which are being transferred into their specific surface. The synthetic admixture is more recommended than the natural one also because of the value of the air-voids spacing factor of concrete.

MICROSTRUCTURAL ANALYSIS OF FORCEMEATS OF READY-TO-COOK CHOPPED MEAT WITH FUNCTIONAL INGREDIENTS

Meat products, at different technological stages and as finished articles, retain their morphological features. Microstructure analysis of the raw material, ready-to-cook products, or finished articles allows determining the presence of certain types of tissues, organs, spices – and low-value admixtures the recipe does not provide for, as well as reused raw materials. Microstructural studies of ready-to-cook chopped meat products allows identifying their components, establishing different properties of various tissue and cellular structures, and controlling the articles manufactured. Minced beef as the object of research was modified, with 5 %, 10 %, 15 % of the meat part replaced with lupin flour and 0.5% of elecampane root powder added as aromatic raw material. For microscopic examination, samples of the forcemeats developed were put marks on and fixed in a 10 % neutral formalin solution. The sections, as thick as 0.5–1 cm, were cut on a sledge microtome. They were stained with haematoxylin and eosin, and the PAS reaction. Light microscopy and microphotography of the tissue specimens were performed with a microscope Leica DM 2500 and a camera Leica DFC 450C with the software Leica aplitation suite 4.4. The micrographic investigation of the forcemeats revealed polygonal and round muscle fibres (their dark nuclei were clearly seen under the sarcolemma), concentrations of adipose tissue histologically characterized by a reticulate structure. In the microphotographs, lupin flour looks like groups of round light purple cytoplasm with dark purple nuclei in the centre of polygonal cells; bread looks like loose brown fibres; wavy violet fibres represent onions; and single dark brown spots marked elecampane. It has been shown that histological studies, with the PAS reaction used, are helpful in determining the meat and plant content in the ready-to-cook meat developed, and that haematoxylin and eosin can help determine the functional ingredients content.

The effectiveness of different superplasticizers in ambient cured one-part alkali activated pastes

This paper investigates the effect of using different admixtures on the one-part ambient-cured alkali activated pastes. Na2SiO3-Anhydrous powder was used as solid activator along with three superplasticizers including naphthalene, melamine and polycarboxylate with different water/precursor ratios. The flowability, setting time and compressive strength development were evaluated for all AAMs mixes. ATR-FTIR test was used to check the admixtures stability in high alkali media.All types of admixtures significantly improved the flowability of the Na2SiO3-anhydrous one-part AAMs and marginally affected the compressive strength. The results showed that polycarboxylate was effective for high water/precursor (≥0.36) while naphthalene performed better in case of low water/precursor (≤0.36) for Na2SiO3-anhydrous one-part AAMs. However, lowering the water/precursor ratio in the Na2SiO3-anhydrous one-part AAMs using superplasticizers showed no improvement or modest improvement in the compressive strength. The ATR-FTIR results revealed the relatively high stability of admixtures in Na2SiO3 alkali medium of one-part AAMs (for w/b = 0.4).

READY MIXED CONCRETE CONSTITUENT MATERIALS; PLASTICIZING CHEMICAL ADMIXTURES AND EFFECTS ON FRESH AND HARDENED PROPERTIES

The effects of plasticizing admixtures on the properties of fresh and hardened ready mixed concrete were studied. Eight different concrete mixtures were designed by two different polycarboxylate based plasticizing admixtures, CEM III/42,5 N type Portland cement, ground granulated blast furnace slag, natural sand, crushed limestone, and water. Flow ability of the freshly mixed concretes were measured and the compressive strength tests were carried out on 150 mm cubic specimens at the ages of 7 and 28 days. It was observed that flow values increased when the amount of admixture used in the mixtures increased. The composition of the admixture affected the flow values of the mixtures significantly. Compressive strength test results revealed that the increase in amount of slag in the amount of total binding material resulted in lower 7-days strength values. Type of chemical admixtures significantly influenced the 7-days strength values. This was attributed to the different secondary effects of different plasticizing chemical admixtures. Type of chemical admixture influenced both 7-days strength and 28-days strength even the mixtures had equal amounts of ingredients and also equal water/binder ratios. This result showed that plasticizing chemical admixtures can affect both early and later age strengths of ready mixed concrete even for equal water/binder ratios.