دانلود رایگان مقاله خواص پایداری و مکانیکی بتن ترکیبی زئولیت طبیعی

ABSTRACT

This paper investigates the application of natural zeolite as a substitute of cement in concrete. It studies the mechanical and durability properties of concretes containing 10% of natural zeolite and superplasticizer, as well as 10% of natural zeolite, superplasticizer and an air-entraining agent in comparison to concretes without natural zeolite. The study shows that fresh concrete mixture containing zeolite due to its high surface area demands a higher dosage of superplasticizer to achieve the targeted slump flow. While concretes containing natural zeolite characterize a lower compressive strength until 90 days of hardening, the compressive strength exceeds the strength of the concretes without zeolite after 180 days. The results also reveal the considerable effectiveness of using a superplasticizer and an airentraining agent in zeolite incorporating concretes on water penetration, drying shrinkage and freeze–thaw resistance of concretes.

4. Conclusions

This paper considers the issues of development of effective concrete containing natural zeolites. The most important conclusions are as follows: 1. Proposed approaches allow implementing technologies of modified concretes with the required properties, obtained by the simultaneous introduction of an active mineral additive such as natural zeolite and chemical admixtures of plasticizing and air-entraining action in construction industry. 2. Investigations of mechanical properties of concretes show that the substitution of cement by zeolite resulted in some reduction of strength until 90 days of hardening, but after 180 days compressive strength of concretes containing zeolite exceeds the strength of concrete without zeolite. 3. Introduction of zeolite and chemical admixtures in concrete permits modifications of the phase composition of cement hydration products with the formation of an extra amount of calcium hydrosilicates, hydrogelenite and ettringite and also improves the pore structure of concrete.