جستجوی مقالات مرتبط با کلیدواژه « زئولیت طبیعی » در نشریات گروه « عمران »

In the past few decades, warm mix asphalt (WMA) has been used as advanced technology alternative to hot mix asphalt (HMA) due to the relatively low temperatures required heating the asphalt in the production and application process, reducing environmental damage while providing benefits. Asphalt maintains the hot mix, it is noticeable. However, low manufacturing and processing temperatures may result in asphalt deterioration from moisture. The aim of this study was to evaluate the characteristics of asphalt containing natural zeolite and compare it with synthetic zeolite and WMA organic and chemical additives against deterioration against moisture. Resistance properties of samples against moisture sensitivity using tests.

The present investigation is studied the effect of the replacement of different percentages of natural zeolite (Ze) pozzolan powder on the mechanical properties of recycled concrete made from coarse masonry recycled aggregates. In made concretes, natural aggregates were replaced with recycled coarse masonry aggregates at 25%, 50% and 100% levels. For improve the mechanical properties, natural zeolite was replaced by cement at 10%, 20% and 30% levels. In total, 195 standard cubic and cylindrical concrete samples in the 16 mixing designs were made and compressive strength tests at 7, 28 and 91 days, splitting tensile strength, modulus of elasticity and ultrasonic pulse velocity at 28 days of age were evaluated. the results showed that, at replacement levels of 20% natural zeolite with cement was had the greatest improvement in the mechanical properties of natural concrete but in combination with recycled aggregates, the replacement of 10% natural zeolite by cement was improved the mechanical properties of recycled concrete. also the results showed that, 10% of natural zeolite, using up to 50% of coarse masonry recycled aggregates, Improvement some mechanical properties of recycled concrete was showed relative to conventional concrete without pozzolan, but replace 100% coarse natural aggregates with recycled masonry, mechanical properties of recycled concrete have significantly decreased compared to natural concrete without pozzolan.

The main objective of this study was to assess engineering properties of self-compacting concrete (SCC) incorporating magnetic water and various percentages of natural zeolite. The fresh properties of SCC were investigated by means of slump flow, T50, V-funnel, L-box and visual stability index (VSI). At hardened state, mechanical properties and durability characteristics of concrete were evaluated by means of compressive and tensile strength tests, modulus of elasticity test and water absorption test at different ages under both wet and dry curing conditions. The results of fresh concrete indicated that magnetic water and natural zeolite in SCC can improve the rheological properties and stability of SCC where the magnetic water is able to increase the slump flow up to 3% and decrease plastic viscosity of concrete mixture up to 6% without aggregates segregation. In addition, the presence of magnetic water and natural zeolite improves mechanical properties and durability of SCC. According to this, compressive and tensile strengths and modulus of elasticity of SCC containing magnetic water and 20% natural zeolite were increased up to 42, 12 and 33 %, respectively, at the age of 90 days. In the same concrete mixture, the value of water absorption was decreased up to 48%.

Today, restrictions on access to natural aggregate resources in concrete production have become one of the problems in many countries. Concrete, as one of the most widely used human products, is a factor in consuming a large amount of aggregate. To meet this need, today many developed countries use different types of recycled aggregates as a suitable alternative to natural aggregates. The present study investigates the effect of complete replacement of recycled concrete coils instead of coarse natural aggregates in concrete. In order to improve the quality of recycled concrete, the pozzolans like as micro-silica, natural zeolite and fly ash were used in different percentages. In order to determine and compare the mechanical properties of concrete, 11 mixing designs were made and compressive strength tests at 7, 28 and 91 days, indirect tensile strength (SPT), modulus of elasticity and ultrasound velocity tests at 28 days of age were performed. The results showed that micro-silica, especially at the 10% replacement level, has a dramatic effect on the improvement of the compressive strength of fully recycled concrete compared to other pozzolans. The results of the application of natural zeolite in fully recycled concrete showed that this pozzolan, especially in the 10% substitution, act as a cementitious reducing agent and play a lesser role in improving the mechanical properties of recycled concrete compared to recycled concrete without pozzolan. On the other hand, pozzolanic materials, in a way that improves the compressive strength of recycled concrete, are not able to improve the tensile strength and the modulus of elasticity of the recycled concrete compared to conventional concrete.

The present study studies the effect of the replacement of different levels of recycled concrete aggregates on the mechanical behavior of recycled concrete. In made concretes, natural aggregates have been replaced at three levels of 25%, 50% and 100% with recycled concrete coarse aggregates. In order to enhance the mechanical performance of these concrete, each of the pozzolans including micro-silica, fly ash and natural zeolite has been replaced with cement at three different levels. A total of 360 cube and cylindrical concrete specimens were made in the form of 40 mixing designs, and tests of compressive strength, tensile strength, static modulus of elasticity and ultrasonic pulse velocity at 28 days of age were performed. The results showed that, without the use of pozzolanic materials, up to 25% replacement of recycled coarse aggregate, there was no significant change in the mechanical performance of this concrete, while the higher replacement rates resulted in a significant drop in the mechanical performance of this concrete. The use of micro-silica, especially at the replacement level of 10%, has led to a very good performance of recycled concrete even in the case of full replacement of recycled coarse aggregates. Other pozzolanic materials used were also relatively less and in lesser intervals of recyclable materials to improve their mechanical properties.

The present study was conducted to compare the effect of natural zeolite (Z) and silica fume (SF) pozzolans on the mechanical properties of recycled aggregates concrete (RAC’s). The RCA’s made with using different levels of recycled coarse aggregates instead of natural coarse aggregates. To improve quality of RCA’s, the introduced pozzolans were replaced with different levels of ordinary Portland cement (OPC). To determine and compare the mechanical properties of concretes, 24 mix designs were made and different tests done as compressive strength at the ages 7, 28 and 91 days, and the tests as splite cylinder tests (SPT), modulus of elasticity and ultra-pulse velocity (UPV) at the age of 28- day. The obtained results generally showed that in duration of 28 days, the usage of silica fume could results in about 40 MPa compressive strength for RCA’s with 100% of recycled coarse aggregates; meanwhile using natural zeolite was not able to give target strength of design. Using 10% of silica fume instead of OPC in RCA’s specially RCA’s having 25% of recycled aggregates caused in the mechanical properties of RCA’s be rarely like those natural aggregate concretes. Although, using 10% of zeolite in concrete could improve some mechanical properties, but the concretes containing silica fume gave superior mechanical properties than those of zeolite.

Recently, the electrochemical impedance spectrometry (EIS) has been found as a key method in the field of materials science and electrochemistry for determination of electrical behavior of concrete and especially the interfacial zone of steel-concrete layer. In this paper, EIS of reinforced concretes made with binary and ternary combination of zeolite and copper slag as supplementary cementitious material were examined in an experimental research. Moreover, equivalent electrical circuits fitted for evaluation of steel/concrete interface of such concretes. The results showed that zeolite and copper slag enhanced the durability properties of concrete including the water and chloride permeability indexes. Also, with aid of electrical models and determining the polarization resistance with stern- geary equation, it was found that these martials increased the polarization resistance leading to the decrease of corrosion rate up to 65%.