Comparative Study of Metakaolin and Zeolite Tuff Influence on Properties of High-Strength Concrete

Composite admixtures which include active pozzolanic components and high-range water reducers, allows to obtain high-strength, particularly dense and durable concrete to achieve a reduction in resources and energy consumption of manufacturing.Zeolite, containing a significant amount of active silica, can serve as one of the alternative substances to resources and energy consuming mineral admixtures like metakaolin and silica fume. The deposits of zeolites are developed in Transcarpathia (Ukraine), USA, Japan, New Zealand, Iceland and other countries. It is known that zeolite tuffs exhibit pozzolanic properties and are capable to substitution reactions with calcium hydroxide.However, the high dispersion of zeolite rocks leads to a significant increase in the water consumption of concrete. Simultaneous introduction of zeolite tuffs with superplasticizers, which significantly reduce the water content, creates the preconditions for their effective use in high-strength concrete.Along with dehydrated (calcined) zeolite, natural (non-calcined) zeolite expresses itself as an effective mineral admixture of concrete. When using non-calcined zeolite, the effect of increasing in compressive strength at the age of 3 and 7 days is close to the effect obtained when using dehydrated zeolite: 8-10% and 10- 12%, respectively, and 28 days the strength growth is 13-22%. The use of non-calcined zeolite has a significant economic feasibility, so it certainly deserves attention. There were compared the effect of zeolite to metakaolinThe results of the research indicate that the use of composite admixtures, consisted of calcined (non-calcined) zeolite tuff of high dispersity and superplasticizer of naphthalene formaldehyde type, allows to obtain concretes classes C50…C65.

Rheological Behavior of High-Performance Shotcrete Mixtures Containing Colloidal Silica and Silica Fume Using the Bingham Model

There have been numerous studies on shotcrete based on strength and durability. However, few studies have been conducted on rheological characteristics, which are very important parameters for evaluating the pumpability and shootability of shotcrete. In those studies, silica fume has been generally used as a mineral admixture to simultaneously enhance the strength, durability, pumpability, and shootability of shotcrete. Silica fume is well-known to significantly increase the viscosity of a mixture and to prevent material sliding at the receiving surface when used in shotcrete mixtures. However, the use of silica fume in shotcrete increases the possibility of plastic shrinkage cracking owing to its very high fineness, and further, silica fume increases the cost of manufacturing the shotcrete mixture because of its cost and handling. Colloidal silica is a new material in which nano-silica is dispersed in water, and it could solve the above-mentioned problems. The purpose of this research is to develop high-performance shotcrete with appropriate levels of strength and workability as well as use colloidal silica for normal structures without a tunnel structure. Thereafter, the workability of shotcrete with colloidal silica (2, 3, and 4%) was evaluated with a particle size of 10 nm and silica fume replacement (4 and 7%) of cement. In this study, an air-entraining agent for producing high-performance shotcrete was also used. The rheological properties of fresh shotcrete mixtures were estimated using an ICAR rheometer and the measured rheological parameters such as flow resistance and torque viscosity were correlated with the workability and shootability. More appropriate results will be focusing on the Bingham model properties such that the main focus here is to compare all data using the Bingham model and its performance. The pumpability, shootability, and build-up thickness characteristics were also evaluated for the performance of the shotcrete. This research mainly focuses on the Bingham model for absolute value because it creates an exact linear line in a graphical analysis, which provides more appropriate results for measuring the shotcrete performance rather than ICAR rheometer relative data.

Experimental Research on Mechanical and Permeability Properties of Nylon Fiber Reinforced Recycled Aggregate Concrete with Mineral Admixture

Plain concrete’s major two drawbacks are its low tensile strength and high carbon footprint. Joint adding of fibers and recycled/waste materials in concrete might assist to resolve these problems. In the present study, a novel technique is planned to improve the recycled aggregate concrete (RAC) mechanical behavior and durability performance by joint incorporation of silica fume (SF) and nylon fibers (NF). In this research paper, different properties of concrete samples are examined for example flexural strength, compressive strength, split tensile strength, penetration of chloride ions, acid resistance, and water absorption. It was noted that adding nylon fibers as individual components enhances the recycled aggregate concrete mechanical characteristics and resistance to acid exposure. The inclusion of nylon fibers improved the behavior of the recycled aggregate concrete; however, it also increased the chloride penetration and water absorption by only 18% and 8% respectively. Up to 26% of mechanical strength of concrete was improved when silica fume was added in comparison to reference concrete, silica fume also assisted in controlling the loss of durability because of adding recycled aggregate concrete and nylon fibers. Silica fume improved the bond between binder matrix and nylon fibers. The study revealed that the combination of 50% RCA, 0.5% nylon fibers and 20% silica fume are optimum for the joint incorporation into concrete that can assist in developing sustainable, durable, and ductile recycled aggregate fiber reinforced concrete.

Compressive Strength and Chloride Ion Permeability Test of Concrete Incorporating Fly Ash and GGBS with Diverse Water Binder Ratio

In this study conventional concrete of M40 grade developed with diverse water binder ratio and fixed optimum dosage of 30% mineral admixture fly ash and GGBS with weight of cement .Compression test has been conducted on cube samples and Rapid Chloride permeability test (RCPT) are conducted on cylindrical specimens to acknowledge durability parameter. Compression test results has been enhanced with replacement of supplementary cementitious materials and chloride ion permeability has been reduced with substitution of fly ash and GGBS .incremental of water binder ratio also reduce the permeability value however compression value increased

Effect of Admixtures on Concrete and Superplasticizers on Cementitious Material

Use of chemical and mineral admixtures have proved beneficial in improving quality, workability and have enhanced finish ability of concrete. They also help in maintaining the concrete during its important stages such as mixing, transporting, placing, curing and also in adverse weather conditions. Superplasticizers are super water reducers that allow 15-20% water reducion thereby increasing the workability without any change in the composition of mix.The reduction in water and cement reduces creep, shrinkage and heat of hydration. In this paper effect of different chemical and mineral admixture was studied along with sand to aggregate volume ratio ,cement content and water were analysed by preparing different concrete mixtures using water reducers and superplasticizers. A specimen of 200mm and 300mm was prepared and tested for compressive strength, split tensile strength and young's modulus. Slump test was also performed at 15 min interval. Also superplasticizers (TJ III , LIGNIN-SULPHONATE-based and NAPHTHALENE-SULPHONATE-based) were taken and their effect on the heat of hydration and induction period of cementitious material (portland cement) was studied. Keywords: admixture, workability, superplasticizer, water cement ratio, heat of hydration.

Chemical sulphate corrosion on cement composites in various model environments

Background: Cementitious composites, which are subject to increasing demands, are often exposed to various external attacks, such as aggressive groundwater and surface water, chemicals in the soil, gas penetration, or phenomena related to water freezing and melting. One of the most common reasons for the deterioration of cement composites is the corrosion process. Corrosion results in irreversible damage that occurs during the chemical reaction of the material with the components of the environment. Methods: The paper deals with experimental study of chemical sulphate corrosion of cement composites prepared from three types of cement: ordinary Portland cement; sulphate-resistant cement; and special hybrid cement, and industrial by-products and wastes: silica fume, zeolite and a special mineral admixture based on blast furnace granular slag as cement partial substitutes. Samples of cement composites were subjected to corrosion experiments in a sulphate environment, which took place in the laboratory under model conditions for 180 resp. 270 days. Results: The deterioration parameters: changes in the weight and thickness of the samples, surface and mineralogical changes, leachability of the basic components of the cement matrix as well as changes in the liquid phase proved the degradation process due to chemical sulphate corrosion, model solutions of H2SO4 with pH 3 and 4, and solution of MgSO4 with c (SO4 2 - ) = 3 and 10 g /L. Conclusion: By comparing the leachability of the alkali components from cement composites, it can be concluded that for the most aggressive model solution (H2SO4 with pH 3), both slagcontaining formulations are the most stable in terms of the total ratio of leached calcium and silicon. This finding is also supported by the results of water absorbency tests, which confirmed that despite the increase in absorbency after chemical corrosion, cement composites with slag content reach the lowest values.

Experimental Investigation on Strength and Behavior of PSC Fiber Reinforced Beams with GGBS

The Concrete is one of the most important products which are efficiently and effectively used in the field of construction. The usage of natural aggregates in the process of production of concrete was high which lead to huge deficiency of availability of the natural aggregates. At the same time production of cements leads to more environmental pollution. Therefore, the production of concrete was altered by vast usage of admixtures and replacements for natural aggregates. In this paper M60 grade concrete is prepared by using GGBS as a partial replacement of cement which is a good strength building mineral admixture, the steel fibers were also introduced in the concrete to improve the strength parameter and for ease of work with concrete and addition of AUROMIX – 400 which is provided by FOSROC chemicals Bengaluru as super plasticizers. The concrete specimens like Cubes and Cylinders were casted and allowed to curing over a nominal curing period of 7, 14 and 28 days to know the basic mechanical properties of the concrete with the above replacements and at the same time RCC beams were also casted and cured, then post tensioned to know the flexural details of this special concrete.

Alkali-Active Sand Slate Powder for Use as Mineral Admixture in Mass Hydraulic Concrete: Technical and Economic Analysis

This work has launched a comprehensive investigation on the macro performance and micro structure of mass concrete produced with alkali-active sand slate powder (ASSP) for use as the mineral admixture and a thorough analysis on its technical and economic effects is also conducted. Results indicated ternary blend with hybrid of 5–8 wt.% silica fume (SF) and 15–20 wt.% ASSP has the optimal compressive and flexural strength. ASSP particle participates in hydration, accelerates hydration of cement clinker within 8.5 hours, and reduces the autogenous strain of pastes by 164 × 10−6 in case of dosage less than 25% by mass. Improvement in the mechanical and deformation properties of concrete produced with the hybrid of SF and ASSP is attributed to better particles gradation, compactness enhancement, and transformation in products of hydration. On the whole, it provides another new approach for use of alkali-active rock after second processing as mineral admixture in hydraulic concrete in terms of good performance and economic effects.

Influence of Steel Slag-Superfine Blast Furnace Slag Composite Mineral Admixture on the Properties of Mortar and Concrete

A composite mineral admixture was prepared by steel slag and superfine blast furnace slag. The influence of superfine blast furnace slag content of the composite mixture on the mortar and concrete was investigated. The results show that the composite mineral admixture may decrease the strength of concrete at the early age but improve the strength development over time. Increasing the content of superfine blast furnace slag can reduce the degradation of the early strength. The reduction of the autogenous shrinkage and adiabatic temperature rise is significant when the composite mineral admixture is added. The reduction is more obvious when the water-to-solid ratio (w/s) is low. The results show that with steel slag and superfine blast furnace slag playing as complementary parts in the composite mineral admixture, it can be used as an effective substitute of cement.