Papers by Keyword: Cement

Abstract: Supplementary cementitious materials are additives that are used to improve the qualities of Portland cement while also reducing its environmental impact. The production of such blended cements relies on the regional availability of additional components. Despite the prevalence of volcanic tuffs in the Eastern Desert and South Sinai encountered in Egypt, there is a scarcity of knowledge regarding experimental research on cement manufacture. The main objective of this study is to analyze the geochemical and experimental characteristics of several volcanic tuffaceous rocks exploited as natural additional cementitious materials and their impact on the characteristics of the resulting blended cement. The partially replacement can play an important role in reducing the local environmental impacts (CO₂ emissions). Various volcanic rock specimens have been collected from the Sinai (Wadi Kid) and the Eastern Desert (Gabal Umm Zarabit, Wadi Umm Khariga, Gabal Igla El-Iswid, and Abu Wassat), Egypt. The samples under study were examined for their mineralogy, petrography, and chemical composition in order to identify their specifications. In addition, a total of fifteen blended cement samples were produced by partially replacing clinker with the investigated samples. The substitution ratios used were 10%, 20%, and 25% by mass. A control mix was also designed, consisting of ordinary Portland cement without any other substances. An assessment has been conducted on the effects of partially replacing clinker with volcanic rocks on the characteristics of the resulting blended cement. The physico-mechanical parameters, including Blaine, setting time, flexural strength, and compressive strength, of the hardened blended mortars were measured at specific times (7 and 28 days). The study demonstrated that the strength of the studied blended cement mixes decreased as the fraction of the examined volcanic rocks to clinker ratio increased throughout the early stages. The highest compressive strength among the mixtures evaluated was achieved when using a 10% ratio of volcanic rocks as clinker replacement.

Abstract: An experimental study was carried out to evaluate the feasibility of using concrete compositions containing waste wood for structural and non-structural building applications. First, the inert and wood aggregates used in the composite design were characterized. Five compositions containing a reference, 50% and 100% of wood particles were then produced and characterized in terms of physical and mechanical performance (e.g., apparent density, abrasion, compressive strength, and flexural strength). The selected specimens were used for additional experimental tests. These included water absorption and thermal tests. Increasing wood waste content considerably lower compressive and flexural strengths while improving the thermal insulation quality of wood waste-cement composite. The durability assessment of selected compositions further showed that the abrasion resistance of manufactured specimen decreased by adding wood waste in the cement matrix while there was an increase of the capillarity absorption coefficients. It appears that the incorporation of waste wood particles into mortars decrease their thermal conductivities to 0.3 W/mK. The use of wood waste treated by a lime solution improves the studied properties.

Abstract: Portland cement has been replaced with 50% ground, granulated blastfurnace slag (ggbs) of two types. The influence of 2 and 4% calcium nitrate accelerator on early hydration of such binders was investigated by isothermal calorimetry as well as X-ray diffraction and thermogravimetry. The strength development of mortar based on these binder blends has been followed up to 28 days and the influence of calcium nitrate discussed. One ggbs lower in SiO₂, A_l2O₃ and MgO yielded somewhat lower strength (about 90%) than the other. Addition of calcium nitrate led to lower strength at 1 day, but higher strength from 3 days on-wards. The blends with the two ggbs achieved similar strength at 7 and 28 days when blended with 4% calcium nitrate. Calcium nitrate led to more ettringite formation and AF_m phases (probably nitrate version) at 1-day sealed curing. However, the calcium hydroxide content was reduced. Potential explanations for calcium hydroxide reduction are discussed.

Abstract: Cement dust is principal industrial waste that exhibits detrimental effects on soil properties especially the nitrogen content of the soil. This study investigated the total Nitrogen and Nitrate value of the soil and dust collected in thirteen (13) different locations around Ewekoro Limestone Quarry and Cement Production. The results showed that the total nitrogen value ranges between 0.093ppm and 0.037ppm while the nitrate value ranged from 145.25ppm - 66.50ppm in the soil samples. Also, the total nitrogen in the dust particulate samples was from 0.950-0.100ppm while the nitrate value ranged from 63.00ppm-28.00pm. The value of total nitrogen value and nitrate around Ewekoro Quarry is relatively lower than the value obtained at Ososun, the control location which is about 10km away from Quarry. Duncann Multiple range tests revealed that soil samples collected from Alaguntan, Ajegunle, Arigbajo, Papa Lanto, Rail km 53, Waasinmi Alaafia, Apomu, Isofin Orile, Quarry, were significantly different in total nitrogen from the control sample (Ososun). In contrast, soil samples collected from Ayepe, Lapeleke, and Agbesi do not differ significantly in total Nitrogen from the soil sample. Also, the result of the correlation matrix indicated that there is a significant positive correlation between total nitrogen, conductivity, and depth at (<0.05), while there is a negative correlation but non-significant relationship between soil depth, pH, clay content, and total nitrogen. It is possible that the reduced level of nitrogen around the quarry location compared with the control site must have been due to the effect of cement duct particulates.

Abstract: Geopolymeric mortars made from a mixture of waste from the Peruvian informal mining industry, sodium hydroxide activating solution, and fine sand were studied, comparing them physically and mechanically with conventional Portland cement mortars. Both conventional and geopolymeric mortars were prepared in parallel and then subjected to uniaxial compression tests at various temperatures (ambient, 200 °C and 500 °C). The mechanical results found revealed maximum average resistance values of 63, 84 and 79 MPa for conventional mortars, and 12, 32 and 36 MPa for geopolymeric mortars, when they were tested at room temperature, 200 °C and 500 °C, respectively. The best mechanical results in geopolymeric mortars were found when considering a binder: fine sand ratio of 1:2, molarity of the hardening solution of 12 M and a hardening solution: binder ratio of 0.6. It was possible to demonstrate a good agreement between the distribution of particle sizes observed microstructurally and those found by granulometry studies by laser light diffraction.

Abstract: Direct reuse of precast concrete elements is possible if disassembly is considered in the design phase. An unusual way of designing for disassembly is to use “wet” joints as usual but to optimise the mortar to be less strong and, therefore, easier to remove at the end of the life of the building. A method is presented to test mortars with lime content to determine the shear capacity in the connection between mortar and concrete. Tests are performed with and without an applied normal force and with and without steel bars through the interface. The results show that applying a lime content to the mortar reduces the compressive strength, shear strength and flexural strength. Using steel bars in the connections increases the ductility from less than 1 mm to several mm at the point of failure. The results can be used in future checks of mortar joints in buildings, where it is required to have a minimum strength during the service life and a maximum strength when dismantling. The future mortar requirements will depend on the disassembly method.

Abstract: In this article in order to verify the probability of the formation of the compound CaBaAl₄O₈, a thermodynamic analysis of the following possible solid-phase reactions of its formation was carried out: formation of CaBaAl₄O₈ from the initial components - calcium carbon dioxide, barium carbon dioxide and aluminum oxide; the probability of formation of dual compounds CaAl₂O₄ and BaAl₂O₄ from the same raw materials (since the compound CaBaAl₄O₈ is located on the BaAl₂O₄-CaAl₂O₄ conjugate) and the possibility of formation of the compound CaBaAl₄O₈ from binary compounds CaAl₂O₄ and BaAl₂O₄. As a result of our experimental studies, the existence of ternary compounds Вa₃CaAl₂O₇ and ВaCa₂Al₈O₁₅ was confirmed, and it was found that the Вa₃CaAl₂O₇ compound exists in the system at least up to a temperature of 1400 °C. Thus, our studies have determined an increase in the temperature limits of its existence, in contrast to the data of previous researchers, who indicated 1250 °C as the upper temperature of existence of Вa₃CaAl₂O₇.

Abstract: The construction industry is really concerned with producing better and durable building materials. Hence, the high cost of conventional building materials have resulted into use of locally available materials. This study assess the effect of varying cement content on engineering properties of fired lateritic bricks. The lateritic soil samples were stabilized with cement at 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7 and 7.5%, cast in moulds and later fired for 8 hours at a 1000°C. Index properties (natural moisture content, specific gravity, particle size distribution and atterberg limit tests) were determined on the natural lateritic soil. While compressive strength, water absorption, abrasion and impact value test were determined on the cement fired bricks. The lateritic soil in its natural form were classified as A-6 and clay of high compressibility in accordance to ASTM D-3282. The results of the index properties are within acceptable limits for lateritic soil. The effect of varying cement content on the mechanical properties showed that the compressive strength of the bricks increases from 4.0 N/mm² at control (un-stabilized brick) to 7.3 N/mm² at 5% soil stabilization with cement. However, significant reductions in value was witnessed in the water absorption, abrasion and impact value results between the un-stabilized brick (control) and 5% cement fired bricks. The study concluded that fired bricks stabilized with 5% cement was found to be the best and most suitable for load and non-load bearing walls.

Abstract: 3D concrete printing is an innovative construction process based on fully autonomous material deposition. One of the challenges of implementing this technology is the development of printable concrete formulations, as this material must exhibit particular fresh-state properties. Among these, buildability is one of the most important. This property describes the material's ability to support weight at very early ages, allowing a layer-by-layer construction. Therefore, this paper aims to evaluate two approaches for improving concrete buildability: the optimization of the superplasticizer dosage and the external application of quick-setting admixture. The results showed that reducing superplasticizer content improved buildability by increasing the static yield strength. However, this approach has a collateral disadvantage as concretes presented problems during extrusion. On the other hand, the results of cylinder stability and Vicat tests indicate that the external application of quick-setting admixture leads to concretes with improved buildability without affecting the initial workability and a faster hardening process. According to these results, the latter approach can potentially be applied in small and large-scale 3D printing.

Abstract: The use of industrial waste materials as a substitute for cement in the manufacture of mortar is an alternative approach to reduce carbon dioxide emissions in building construction. In this study, processed waste tea ash (PWTA) obtained from the extraction tea plant was used to partially replace 0-40% cement in the manufacture of mortar. The effects of PWTA on the basic engineering properties of mortar are evaluated and compared to mortar without PWTA. Test results showed that workability and density of mortar decreased with increases in the PWTA content. Furthermore, no decline in compressive strength of concrete was observed up to 20% replacement of cement with PWTA at 7, 28 and 90 days and beyond that, the compressive strength decreased. Results obtained from this study indicate that PWTA can be used as partial replacement of cement up to 20% with comparable strength with normal mortar. This approach helps to minimize the usage of cement in mortar production and can reduce the negative impact of PWTA on the environment.