بررسي اثر سيستم‌هاي عمل‌آوري در خواص مهندسي و دوام بتن‌هاي حاوي زيوليت

Effect of Curing Condition on Mechanical Properties and Durability of Concrete Containing Natural Zeolite

از آنجا كه شرايط محيطي براي بررسي يك ماده‌ي جديد حايز اهميت است. مطالعه‌ي اثر پوزولان زيوليت در شرايط مختلف عمل‌آوري براي آشنايي با خواص ناشناخته‌يي كه ممكن است در يك سيستم عمل‌آوري خاص نمود پيدا كند، در اين پژوهش مورد توجه قرار گرفته است. در اين نوشتار، اثر دو نوع سيستم عمل‌آوري شامل: 1. دايما اشباع در آب، 2. هفت روز نخست در آب و سپس در محيط آزمايشگاه با رطوبت و دماي متوسط در 12 طرح اختلاط با 4 نسبت آب به سيمان و 3%جايگزيني زيوليت مورد بررسي قرار گرفته است. اگرچه نتايج مورد انتظار آزمايش‌هاي بتن با كاهش نسبت آب به سيمان و يا افزايش سن در دو سيستم عمل‌آوري به طور محسوسي با يكديگر متفاوت است، ليكن افزودن زيوليت روند مشابهي در هر دو سيستم عمل‌آوري به دنبال داشته است.

Concrete is the most widely used construction material in the world today. However, the cement industry is intensively energy consuming, and the emission of CO2 during cement production has created enormous environmental concerns. Therefore, using pozzolanic materials as a partial replacement of cement could be a useful remedy. Usual pozzolans, such as fly ash, silica fume, high-reactivity metakaolin and slag, are rarely available and are relatively expensive in Iran, whereas natural zeolite is abundantly deposited and can easily be quarried and processed. Because of these advantages, it seems that zeolite can be a suitable alternative as a high performance and accessible pozzolan for use in the construction industry in Iran. On the other hand, when most people think of curing, they think only of maintaining moisture on the surface of the concrete. But, curing is more than that. It is giving the concrete what it needs to gain strength properly. Concrete strength depends on the growth of crystals within the matrix of the concrete. These crystals grow from a reaction between Portland cement and water, a reaction known as hydration. If there is not enough water, the crystals cannot grow and the concrete does not develop the strength it should. In this article, the effect of two curing systems was investigated: 1) saturated in water all the time, and 2) 7 days in water and after in the lab. So, concrete containing natural zeolite was built. The percentage of zeolite that replaced Portland cement in this research was 0%, 10%, and 15% by mass and the water/binder ratios were 0.35, 0.4, 0.45 and 0.5. Various experiments were carried out to determine the properties of concrete incorporating zeolite at these curing systems. Experimental tests included compressive strength, water absorption, and chloride diffusion at different ages. Generally, results showed that zeolite improved the mechanical and durability properties of concrete, especially in the second system of curing.