Papers by Keyword: Mineral Admixture

Abstract: In certain scenario, seawater maybe the only mixing and curing water available. Normally, concrete mixing requires freshwater, a resource which is expected to vastly deplete as a result of global water scarcity. Seawater which covers more than 70 percent of earth surface has potential to replace the freshwater in concrete. Hence, it is necessary to optimize conditions for its application in concrete, because freshwater reserves are either limited or its transport is costly. Further, the effect of various replacement ratios of fly ash needs further studies to determine applicability on concrete with seawater mixing in particular. Thus, this study aims to examine by which seawater can be employed as mixing water for making concrete, especially for plain concrete. The main objective of this study is to investigate the effect of seawater as mixing and fly ash as supplementary binder at 10%, 20% and 30% for Portland Composite Cement replacement on compressive strength, respectively. The water-to-binder ratio was varied at 40%, 50% and 60%. The specimens were cured (continuous immersion) in freshwater and seawater for 91-days. The results indicated that seawater can be used as mixing and curing water. Compressive strength of concrete increase when using seawater as mixing water and freshwater as curing water especially for w/b of 40%. Also, significant strength development up to 91-days was shown by fly ash concrete when using seawater as curing water and freshwater as mixing water . Effectiveness of seawater curing on strength development of fly ash concrete with w/b of 40% is larger in concrete with freshwater mixing than seawater mixing. The results obtained in this study provide an information in development for applicability seawater in concrete.

Abstract: To explore the effect of mechanical activation on the particle size distribution of the composite admixture a self-designed test jet mill is used. We have studied the effects of different specific surface areas of composite admixtures on the workability, mechanical properties and durability of concrete and combined X-ray diffraction (XRD) with scanning electron microscopy (SEM) to analyze the mechanism of concrete performance improvement. Results showed that, mechanical activation can significantly increase the content of particles below 3 um; appropriate increase in the specific surface area of composite admixture is conducive to improving the performance of concrete; As the specific surface area increases, the hydration activity of the composite admixture increases first and then tends to be stable; during the hydration process, more thin-plate Ca(OH)₂ is converted into needle-shaped AFt, which improves the cement-based material and thereby improving the macro mechanical properties and durability.

Abstract: 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.

Abstract: Interlocking Concrete Block Pavement (ICBP) poses as the most suitable alternative to traditional pavement construction techniques. This is because of the increased advantages in countries wherein durability, and operational or environmental constraints limit the efficiency of the conventional process. The construction industry everywhere faces problems and significant challenges including manpower, quality of productivity, preservation of the environment, mass transportation, water management, raw materials, durability and design life of construction products, chemical resistance, etc. The increased expense on the raw materials for construction is the primary focus of the study. The study aims to search for suitable alternatives that would allow sustainable development. The study emphasizes on the rising costs of construction materials and the necessity to work towards sustainability, alternative construction techniques and materials. Indigenous production of interlocks with mineral admixtures raises the potential applicability of the interlock pavers. To enhance the strength property and keeping sustainability in point of view, fly ash is used as a mineral admixture and partially replaced with cement in various proportions like 0%, 5%, 10%, 15%, 20%, 25%, 30% and 35%. Fourty eight interlock concrete paver blocks were cast and compressive strength for all specimens was calculated and later compared. A notable rise in the strength of the interlock pavers was observed at 15% and 20% replacement levels with fly ash. The optimum level for replacement was determined as 20% of the fly ash.

Abstract: The effect of mineral admixtures on compressive and tensile strength of concrete was studied in the article. The concrete mixtures were modified by quart, quartz-feldspar and basalt powder in amount 10, 20 and 30 % by weight of cement. The mix with no mineral admixture was prepared as a control sample. The results obtained show that selected mineral admixtures lower concrete strength but the degree of strength reduction depends on the used mineral admixture and its concentration.

Abstract: Deterioration of concrete caused by sulfuric acid attacks in sewage and waste water treatment plants has been investigated. To evaluate this type of deterioration, concrete specimens immersed in sulfuric acid solutions are usually examined, and the mass loss and erosion depth of the specimens can be used as physical indicators of the degree of the deterioration, while the sulfate ion penetration can be used as a chemical indicator. Although an actual deterioration is progressing with time, most of previous experimental studies were carried out for a comparatively short time. There is a possibility, therefore, that the deterioration in practice has not been estimated completely yet based on the above indicators. The present study aims at investigating the changes in pore structures and chemical compositions of concrete specimens to evaluate long-term deterioration experimentally. Concrete specimens in which a part of cement was replaced with blast furnace slag, fly ash and silica fume were immersed in sulfuric acid solutions at 0.09 mol/L and 0.006 mol/L for around 1500 days. Pore structures in concrete were investigated to understand the relationship between the erosion depth and the internal space available for expansion due to gypsum production. In addition, chemical compositions of mortar in concrete were analyzed to know the effects of mineral admixture on the resistance to the deterioration.

Abstract: High-performance concrete was prepared by using ceramic waste as coarse aggregate. The influences of several factors, such as the contents of ceramic coarse aggregates, fly ashes and silica fumes, on the properties of concrete material were investigated. The results show that the compressive strength of semi-porcelain coarse aggregate concrete are slightly lower than that of natural concrete, and the splitting tensile strength and the ratio of compressive strength and splitting tensile strength is similar to the ones of natural concrete. After fly ash and silica fume mixed, the compressive strength, the splitting tensile strength and the resistance to water penetration of concrete with semi-porcelain coarse aggregate increase significantly with the increase of silica fume content which meet the requirements of high-performance concrete. Concrete with orcelain coarse aggregate is only suitable for low strength concrete.

Abstract: According to the detection method of "Polycarboxylates high performance water reducing admixture"(JG/T223-2007), the different concrete mix ratio with different binder systems were designed to test the air-entraining content and compressive strength ratio for 3days of the HSP-V and PCA-II polycarboxylate superplasticizer. The results show that the mineral admixtures can reduce the air-entraining content of the HSP-V and PCA-II polycarboxylate superplasticizer, and lead to the compressive strength ratio for 3 days improved. Therefore mineral admixture on polycarboxylate superplasticizer should be fully considered, in order to adapt to the needs of the practical engineering.

Abstract: The paper studies the influences of mineral mixtures on the performance of self-leveling mortar through orthogonal experiments. Morphology by Scanning electron microscopy was used to examine the morphology of mortar. The experiments studied the law of strength as well as the influence by three kinds of additives (fly ash, slag and gypsum). Orthogonal experimental results show that, when the content of Fly ash, gypsum, slag were 5%, 2%, 5%, respectively they work best, and for fluidity results show that the best results were when they take up 7.5%, 2% and 10%, respectively.

Abstract: A linear polarization method was applied to measure corrosion rate of reinforced steel in concrete. The relationship between corrosion rate and mineral admixtures was discussed. The results show that changes of mineral admixtures material will affect the corrosion rate of reinforcing steel in concrete, of which slag is the most obvious.