جستجوی مقالات مرتبط با کلیدواژه "portland cement" در نشریات گروه "شیمی"

In this research, natural pozzolanic materials were used in cement production to reduce the emission of CO2 and energy consumption. The rate of substitution of cement with natural pozzolan powder varied from 20% to 50% in 100 samples. Compressive strength tests were carried out on mortar specimens (4×4×16 cm3) after 2, 7, and 28 days. The obtained activity index was approximately 85% and volcanic ash was pozzolan. The compressive strength values changed from 122 to 318 kg/cm2 after 7 days and from 201 to 433 kg/cm2 after 28 days. However, the reduction of CO2 emission with 20% to 50% of additive amounted from 130.74 tons to 419.32 tons of CO2 per ton of clinker. By using 3 to 53% of additives, electricity consumption decreases from 1.89 to 33.39 kWh per ton of clinker. Moreover, this amount of additive can raise energy savings from 99160.8 to 1751841.8 kJ per ton of clinker.

Coastal area construction provides the biggest challenges in the country's development. Mechanical strength and durability are the two main challenges in coastal areas when compared to conventional construction. The proposed study explores the effect of recycled melamine powder and  poly (vinyl-co-ethylene) copolymer on workability, setting time, aggregate-to-cement adhesion, and the effect of moisture and saline water on concrete mechanical properties. Portland cement was sieved and dried sand, and aggregate was mixed in the ratio of 1:2:4 (cement: sand: aggregate) by weight. The three constituents were manually mixed with 40-45 wt. % tap water, based on cement content, until a homogenous mixture was visibly observed. Cylindrical samples with continuous tampering to avoid voids were cast in standard molds of 4”x 8” (100 x 200 mm) dimensions. The molds were covered and left for 24 hours for setting. Unmolded concrete samples were cured for 7 and 28 days in tap water. The concrete samples were dried and stored for further testing. The same concrete samples were prepared with an additional 1 wt. % and 3 wt. %, based on the cement content, of melamine and poly(vinyl-co-ethylene) copolymer. The samples were subjected to water slump height, water permeability, compressive strength and flexural tests, and carbonation tests. The results showed a 10 % and 16 % decrease in slump height for 1 % and 3 % loadings, respectively for both polymers when compared to controlled samples. Reinforced concrete showed less water penetration for both polymers due to their hydrophobic nature. Higher compressive and flexural strengths and low carbonation depth were obtained for reinforced concrete irrespective of the polymers used in this research.

Compressed Earth Bricks (CEBs) are the main constituents used in building materials like the pillar which holds the whole building. Scientists are struggling to produce stronger materials with the least cost and much more efficient strength. CEB products can very easily bear comparison with other materials such as the sand-cement block or the fired brick. Compressed Stabilized Earth Blocks (CSEBs) are environmentally friendly as these blocks are un-burnt and are economically cheap. These blocks required less labor with respect to fired bricks, so one can prepare them easily. To make CEB’s water resistant and durable 8%, 10%, and 12% cement as a stabilizer is added to the dry soil. The compressive strength measured was much better and increased with an increase in cement content i.e. 17.71MPa for 8% cement additive, 18.334MPa for 10%, and 21.229MPa for 12% as compared to commercially fired clay bricks which are up to 13MPa. The compressive strength increases with an increase in cement proportion. By studying the XRD analysis it was observed that Calcium Aluminum Silicate Hydrate (CASH) peak intensity increases by adding cement to the dry soil. However, crystallinity size decreases. The elemental composition shows that quartz and calcite are the major constituents of these samples which gives them better compressive strength. Hence unfired compressed earth bricks are environmentally friendly and cost-effective by using a very minute amount of cement i.e. 8% and its compressive strength is high as compared to fired clay brick.

Composite cement has several technical, environmental, and economic advantages. Thus, we investigated the properties of a new composite cement composed of four components, including ground granulated blast-furnace slag from Isfahan ‎Steel Co., pozzolan from Rafsanjan Mine, Portland cement from Sepahan Cement Co., and ‎limestone. The chemical and physical properties and activity of the above components ‎were determined. Eight composite cements were prepared and their physical and chemical ‎properties were characterized. After compressive strength test, measurement of flowability and setting time, a composite cement made of 20% slag, 10% pozzolan‎, and 2.5% limestone was selected for additional investigations. After 120 days of curing, SEM, XRD, and TGA testing on cement pastes made of the proposed blend, the control cement, ‎Portland-blast-furnace slag cement (30% slag), and Portland-pozzolan cement (30% pozzolan) were investigated. The blast-furnace slag improved ‎the long-term compressive strength of the composite cement, provided a greater flow to the mortar, ‎and displayed less permeability. In contrast, the pozzolan offered essential benefits, including proper initial strength, suitable setting time, and good grind-‎ability. The standard quality tests do not evaluate the durability of concrete containing a composite cement, while our study is based on the hydration reactions that occurred in the composite cement for four months. The XRD results indicated that the slag had few ‎crystals, whereas numerous crystals were observed in the pozzolan, potentially reducing the ‎compressive strength in the composite cement. The experimental results revealed that the slag and pozzolan positively affect the properties of composite cement and improve its capabilities.‎

This study aims to determine the major elements of Portland cement type I and II (CEMI and CEMII) in a cement factory in north Tunisia and which metal elements are introduced into the production process. We determine also the metal input rate and their distribution at the entrance and exit of the process. The major elements were analyzed and the trace elements (Arsenic, barium, lead, mercury, boron, strontium, Cadmium, Chromium, copper, manganese, nickel, and zinc) were identified. The concentrations of heavy metals in CEMI showed no significant difference p