نوع مقاله : مقاله پژوهشی
1 گروه ساختمان- دانشکده معماری و شهرسازی دانشگاه شهید بهشتی تهران
2 دانشگاه شهید بهشتی
3 استاد مدعو دانشکده معماری و شهرسازی، دانشگاه شهید بهشتی، تهران
4 استادیار دانشکده معماری دانشگاه شهید بهشتی
عنوان مقاله [English]
Nowadays, it is a common idea to use decorative concrete panels as an alternative to natural stone. Graphic concrete is one of the different types of decorative concrete using the exposed-aggregate method. Considering that there has been no research for graphic concrete production in Iran so far, the aim of this research is to localize and simplify the method for the first time. For this purpose, concrete samples with 435 kg/m3 and 500 kg /m3 Portland cement and water to cement ratio of 0.40 and 0.45 have been produced using natural sand as aggregate. Also, superplasticizer with dosage of 0.35 % and air-entraining admixture with dosage of 0.02% have been used. Concrete specimens were tested in terms of visual criteria, compressive strengths and water absorption in 28 days in accordance with the requirements of Iran National Standard 12038. The results showed that samples with the water to cement ratio of 0.40, which were produced without using of superplasticizer and air-entraining admixture, due to low workability of the mixture, are not in good condition in terms of compressibility. Also low workability, in addition to disrupting the designs printed on the membrane, causes many holes on the concrete surface after leaving the mold, which is visually rejected. Despite the positive effects of air entraining admixture on workability, plastic viscosity and visual criteria, this type of admixture reduces the compressive strength by 30 to 35% and increases water absorption, which is not recommended. Finally, mixture design with 500 kg/m3 cement, water to cement ratios of 0.40 and 0.45, which were produced using superplasticizer with 28-day compressive strength of 54.6 and 52.5 MPa and water absorption of 3.25% and 3.50% while meeting all requirements are suitable for production of graphic concrete decorative panels.