Search

In this study, the effect of using waste granodiorite powder (WGP) as a cement replacement material in percentages ranging from 1 to 9% on various physical and mechanical properties of ordinary concrete was investigated. The resistance of produced concretes with WGP to the high temperature effects on the 28 days compressive strength were studied as well. Granodiorite is one of the well-known igneous rocks that have been used in previous research as a replacement for coarse or fine aggregates due to the hardness of its grains. However, rare studies have investigated its powder as a partial cement replacement material. Results showed the ability of investigated WGP with high surface area to act as a supplementary cementitious material that contributed to enhance the results of mechanical and physical properties of concrete. At traditional room temperature, the optimal replacement percentage was 7%, where the 28 days compressive and tensile strengths were improved by 28.3% and 17.3%, respectively. The optimal replacement ratio varied between 7 and 9% in the case of high temperatures, according to exposure time and temperature degree. Statistical and sensitivity analysis was conducted on 66 available compressive strength value represents all variables before and after elevated temperature exposure. While the regression equation showed good R2 value of 85.3%, sensitivity analysis indicated that compressive strength value is most sensitive to temperature, followed by WGP ratio and exposure time, with importance values of 56, 26, and 18 %, respectively. Results showed also that the setting times and consistency was decreased with increasing the replacement ratio with WGP, while the workability was slightly improved up to 5% replacement ratio. Furthermore, microstructure analysis showed that WGP can help to densify the concrete matrix due to its small size and ability to fill the interstitial voids in the concrete matrix. [ABSTRACT FROM AUTHOR]

Currently, the main material used in various construction materials is concrete, which is a composite material containing cement, water, and aggregate. These ingredients are materials derived from sometimes limited natural resources. In addition, economic growth today uses a variety of materials and generates a lot of waste that directly affects the environment. This research compared concrete mixes using the wastes of concrete piles as aggregate and replacing 10, 20, or 30 % (v/v) of fine aggregates with plastic waste (PW) from the recycling process, called Recycled Aggregate Concrete or RAC. Sensors were installed on the concrete surface of samples to determine the early movement of concrete particles under compressive load. It was found that the RAC developed greater compressive strength compared to ordinary concrete using natural ingredients. Increasing the proportion of fine aggregate replacement with plastic waste in RAC decreased the maximum compressive strength and the rate of compressive strength development. In a similar manner, the repeated use of RAC as aggregate affected the compressive strength of the concrete and the rate of development. Increasing plastic replacement in the recycled concrete had a more substantial impact on recycled concrete strength than increasing the number of recycle times. PW replacement of 10 % of the fine aggregates is recommended. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a study on the possibility of replacing natural coarse aggregates with recycled aggregates in concrete in terms of strength, namely compressive strength and flexural strength. The concrete was designed to have a 25MPa compressive strength and an 8cm slump. The replacement rates of natural aggregates with recycled coarse aggregates were 0%, 10%, 15%, and 20%. The test samples were compressed to determine their strength value after 28 days of curing. The research results give a more complete assessment of the efficiency of the use of recycled raw aggregates instead of natural aggregates in concrete. The results indicate that using recycled aggregates is feasible due to the small decrease in concrete strength. The experiment shows that up to 20% replacement, the recorded reduction in the strength of concrete is lower than 15%. However, it is indispensable that the strength of concrete should be enhanced when recycled aggregates are used. According to previous works, fiber reinforcement may be an effective solution. Therefore, to further develop research using recycled aggregates, it is necessary to consider using different fibers to strengthen the concrete. The fiber content can be used in the range of 0-1% of the weight of concrete. [ABSTRACT FROM AUTHOR]

This paper presents the results of experimental studies which were carried out to investigate residual properties of heat-treated concrete mixes made with recycled aggregates by adding fly ash. Mixes made with natural aggregates were used as control mixes. Concrete cylinders made of both types of mixes were employed in the experimental programme. The cylinders were heat treated at temperature varying from 100°C to 1000°C in increments of 100°C and were tested in compression and tension to determine their respective residual strengths. The residual strengths of both types of mixes followed a similar pattern of reduction at higher temperature exposure. The residual compressive stress and elastic modulus became nearly 15% at 900°C and 700°C, respectively. A slightly higher mass loss was observed in RAC mixes due to the use of recycled aggregates which contained more free water and sustained larger thermal deformation on heating at high temperatures. [ABSTRACT FROM AUTHOR]

Calcium carbonate precipitation and crystallization induced by urease enzyme to solidify soil is known as biocement technology. The uses of waste and cheap materials can make this technology more cost-effective and practical for applications. In this study, calcium ions were obtained by dissolving waste concretes in acidic liquid. Sand columns were treated by enzyme-induced carbonate precipitation (EICP) with either concrete-extracted calcium or reagent calcium for comparison. Compressive strengths, calcium carbonate contents, and microscopic analysis on the treated sand were carried out. It was found that the compressive strength of the former could reach 833 kPa in the dry state and 204 kPa in the wet state after 5 times of EICP treatment, both of which were higher than that of the latter. The calcium carbonate contents could reach 2–3% after 3–5 times of treatment. Based on the scanning electron microscope (SEM) and X-ray diffractometer (XRD) analyses, the crystal type of calcium carbonate produced in sand was calcite. The comparative results showed that the treatment effect using concrete-extracted calcium was similar or better than that using reagent calcium.

Quarry aggregate reserves are depleting rapidly within Australia and the rest of the world due to an increasing demand for aggregates driven by expansion in construction. The annual production of premix concrete in Australia is approximately 30 million cubic meters, while 3–5% of concrete delivered to site remains unused and is disposed of in landfill or crushing plants. The production of coarse aggregates using this waste concrete is potentially a sustainable approach to reduce environmental and economic impact. A testing program has been conducted to investigate mechanical performance and permeation characteristics of concrete produced using a novel manufactured coarse aggregate recycled directly from fresh premix concrete. The recycled coarse aggregate (RCA) concrete satisfied the specified 28-day design strength of 25 MPa and 40 MPa at 28 days and a mean compressive strength of 60 MPa at 90 days. Aggregate grading was observed to determine strength development, while low water absorption, low drying shrinkage, and higher packing density indicate that the RCA concrete is a high-quality material with a dense pore structure. The rough fracture surface of the aggregate increased the bond between C-S-H gel matrix and RCA at the interfacial transition zone. Furthermore, a good correlation was observed between compressive strength and all other mechanical properties displayed by the quarried aggregate concrete. The application of design equations as stated in Australian standards were observed to provide a conservative design for RCA concrete structures based on the mechanical properties. [ABSTRACT FROM AUTHOR]

• A mix design method for SCRAC which targets slump-flow and strength is proposed. • The proposed method avoids tedious adjustments and laboratory re-testing. • Effectiveness of the proposed method was verified by the tests of 11 mix proportions. • The formula for predicting the cubic strength of SCRAC has generally good accuracy. • The proposed method can also be used to prepare SCRAC with RCA and punching residues. If waste concrete and excavated engineering soil can be recycled into self-compacting concrete, it could not only alleviate the shortage of natural resources but also realize the sustainable development of self-compacting concrete technology. Therefore, a novel method is proposed for designing self-compacting recycled aggregate concrete (SCRAC) mix. The method is developed by target slump-flow and target compressive strength, avoiding tedious adjustments and laboratory re-testing at the concrete level. The proposed method first determines the contents of natural and recycled coarse aggregate based on the target slump-flow and those of natural and recycled sand are then obtained. Then, the required effective water-cement ratio is calculated based on the target compressive strength. The required admixture content is determined based on the paste rheology. Eleven mixtures designed in this manner were cast and tested. The tested variables included the target slump-flow, target compressive strength, replacement ratio of recycled coarse aggregate (RCA) and recycled sand (RS) from the excavated engineering soil, and coarse aggregate size. The results showed that the proposed method was applicable to SCRAC with a 600–800 mm target slump-flow, 40–60 MPa target compressive strength, 0–100% RCA, 0 and 100% RS, and 5–10, 5–16, and 5–20 mm coarse aggregate sizes. Finally, SCRAC using the RCA and punching residues was successfully fabricated to further verify the feasibility of the proposed method. The proposed method provides design guidance for self-compacting concrete containing RCA and RS obtained from excavated engineering soil. [ABSTRACT FROM AUTHOR]

Katı atıkların yönetimi, günümüzde gelişmiş toplumların en büyük sorunlarından biri haline gelmiştir. Yeşil bina konseptiyle birlikte atik malzemelerin geri dönüştürülerek yeniden kullanılması önem kazanmıştır. Sürdürülebilir hayatta inşaat yıkıntı atıklarının çevreye verdiği zarar geri kazanılmış agreganın kullanılmasını zorunlu kılmaktadır. Bu çalışmada, yaşı 7 gün ve sınıfı C30 olan beton atıklarından elde edilen iri ve ince agreganın geri dönüşüm agregası olarak betonda kullanım olanakları araştırılmıştır. Kırma agrega 0-4 ve 4-22.4 boyutlarında iki grup olarak kullanılmıştır. Kırma agrega grupları % 0, 10, 20, 30, 40, 50 ve 100 oranların da ağırlıkça azaltılarak yerine geri dönüşüm agregası ikame edilmiştir. Beton örneklerinin 28 ve 90 günlük basınç dayanımları, 28 günlük elastisite modülleri belirlenmiştir. Elde edilen deney sonuçlarına göre; geri dönüşüm agregasının beton üretiminde kullanılabileceği ve sürdürülebilir beton üretimine ışık tutacağı görülmüştür.

Copyright of Journal of Polytechnic is the property of Journal of Polytechnic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Katı atıkların yönetimi, günümüzde gelişmiş toplumların en büyük sorunlarından biri haline gelmiştir. Yeşil bina konseptiyle birlikte atik malzemelerin geri dönüştürülerek yeniden kullanılması önem kazanmıştır. Sürdürülebilir hayatta inşaat yıkıntı atıklarının çevreye verdiği zarar geri kazanılmış agreganın kullanılmasını zorunlu kılmaktadır.Bu çalışmada, yaşı 7 gün ve sınıfı C30 olan beton atıklarından elde edilen iri ve ince agreganın geri dönüşüm agregası olarak betonda kullanım olanakları araştırılmıştır. Kırma agrega 0-4 ve 4-22.4 boyutlarında iki grup olarak kullanılmıştır. Kırma agrega grupları % 0, 10, 20, 30, 40, 50 ve 100 oranların da ağırlıkça azaltılarak yerine geri dönüşüm agregası ikame edilmiştir. Beton örneklerinin 28 ve 90 günlük basınç dayanımları, 28 günlük elastisite modülleri belirlenmiştir.Elde edilen deney sonuçlarına göre; geri dönüşüm agregasının beton üretiminde kullanılabileceği ve sürdürülebilir beton üretimine ışık tutacağı görülmüştür.Anahtar Kelimeler: Yeşil bina, Sürdürülebilir beton, Atık beton, Geri dönüşüm agregası, Basınç dayanımı

With the goal of achieving sustainable development, many studies have been performed on approaches to reducing environmental load and cutting construction-related waste and greenhouse gas emissions. For this reason, this study aims to reduce carbon emissions and preserve the fixed materials such as limestone by utilizing the presumably high value-added cementitious powder of waste concrete, which is not currently being recycled. First, the chemical properties of cementitious powder were analyzed to manufacture recycled carbonic cement by deriving the optimal mix proportion of the materials using the industrial byproduct (former slag) and limestone as a property adjustment. To make a clinkering evaluation, Free CaO measurement, an XRD analysis, a thermal analysis, a compressive strength test and a flowability analysis were performed. Through this series of analyses, overall properties were found to be at 80% those of OPC or better. In addition, when using the cementitious powder as a substitute for limestone, it was discovered that the carbon emissions were reduced by up to 46%. However, as the amount of fine aggregate that was not separated from the cementitious powder due to its similar grain size and shape increased, the plasticity and the reduction in carbon emissions were radically decreased. Moreover, when the fine aggregate was mixed in the proportion of more than 30%, it is believed to be hardly materialized. Therefore, an effective separation technology of cementitious powder from fine aggregate should be researched and developed in the future. [ABSTRACT FROM AUTHOR]

Copyright of Selcuk University Journal of Engineering, Science & Technology / Selçuk Üniversitesi Mühendislik, Bilim ve Teknoloji Dergisi is the property of Selcuk University, Engineering & Architecture Faculty and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)