بررسی اثر استفاده از شورآبه زیرزمینی و زئولیت بر مقاومت فشاری بتن غیرمسلح (مطالعه موردی: اراضی خشک شمال و غرب استان گلستان)

به دلیل مجاورت به دریا، شرایط زمین شناسی و ویژگی های هیدروژئولوژی مناطق شمالی و غربی استان گلستان، آب زیرزمینی در این منطقه بسیار شور است. از سوی دیگر، به دلیل عدم دسترسی به آب سطحی با کیفیت مناسب در اغلب ماه های سال، انجام فعالیت های عمرانی و ساختمانی در این منطقه همواره با چالش هایی همراه است. بر این اساس، پژوهش حاضر با هدف بررسی 120 تیمار دربرگیرنده سه سطح کیفیت آب (شامل آب شهری، شورآبه زیرزمینی و ترکیب آب شهری و شورآبه زیرزمینی با نسبت برابر)، چهار سطح زئولیت (شامل کاربرد 0، 10، 20 و 30 درصد زئولیت به جای سیمان در طرح اختلاط)، دو سطح مصالح سیمانی (شامل 250 و 350 کیلوگرم بر مترمکعب) و پنج سن اندازه گیری مقاومت فشاری (3، 7، 21، 56 و 90 روز) در سه تکرار صورت گرفت. نظر به تنوع قابل ملاحظه تیمارهای آزمایش در این پژوهش و با توجه به عدم تجزیه و تحلیل های آماری در پژوهش های قبلی، نتایج پژوهش حاضر در قالب طرح کاملاً تصادفی به صورت آزمایش فاکتوریل تحت آزمون های تجزیه واریانس (anova) و مقایسه میانگین ها (lsd) قرار گرفت. نتایج نشان داد که امکان استفاده از شورآبه زیرزمینی و زئولیت در طرح اختلاط بتن به ویژه در عیار سیمان 350 کیلوگرم بر مترمکعب بدون آن که موجب کاهش معنی دار مقاومت فشاری بتن گردد، و حتی این ویژگی را در برخی شرایط به طور معنی داری افزایش دهد، وجود دارد. با این حال، با توجه به وجود برهمکنش سه گانه این عوامل که به معنای اثرات متفاوت نوع آب و درصد زئولیت در عیارهای مختلف سیمان است، انتخاب بهترین سطح کاربرد زئولیت و نوع آب با توجه به عیار سیمان مورد نظر باید بر اساس آزمون طرح اختلاط در کارگاه به دست آید.

The effect of briny groundwater and zeolite on compressive strength of plain concrete (case study: northern and eastern dry regions of Golestan province)

Global water scarcity and air pollution by greenhouse gases have amplified the need to use of unconventional water and environmental friendly materials in the concrete industry. Because of its proximity to the Caspian sea, the geological conditions and hydrogeological characteristics of the northern and western regions of Golestan province, groundwater in this area is very salty. On the other hand, due to lack of access to good quality surface water in most of the months, civil and construction activities in this area are always challenging. Accordingly, the present study was conducted to investigate 120 treatments (including three levels of water quality including tap water, briny grounwater and mixture of equal ratio of tap water and briny grounwater), four levels of zeolite (including 0, 10, 20 and 30 percent of zeolite application instead of cement in the concrete mix design), two levels of cement content (including 250 and 350 kg.m3) and five curing ages (including 3, 7, 21, 56 and 90 days) in three replications. Considering the considerable types of the experimental treatments in this study and in respect to the lack of statistical analysis in previous studies, the results of this study were analyzed based on a completely randomized design with factorial experiment using analysis of variance (ANOVA) and means comparison (LSD) tests. Averagely, use of briny groundwater resulted insignificant increase in the compressive strength of concrete specimens compared to tap water, while combined water significantly decreased this property, but this reduction was within permissible range 10 percent based on national and international standards. Also, replacement of 10, 20 and 30 percent of cement by zeolite compared to nonzeolite treatment significantly reduced the compressive strength of concrete specimens by 9.9, 9.5 and 23.1 percent, respectively, but the difference between replacement level 10 and 20 percent was not significant. However, Concurrent use of briny groundwater and zeolite up to 20% can be recommended without significantly reducing the compressive strength of concrete. In the cement content of 250 kg.m3, the difference between tap water and combined water treatments was not significant, but the use of briny groundwater resulted significance increase in compressive strength of concrete pieces by 22.8 and 21.8 percent compared to tap water and combined water, respectively. In contrast, in the cement content of 350 kg.m3, the highest compressive strength was obtained in samples made with tap water, briny groundwater and combined water, respectively, and the differences between them were statistically significant. The results showed that due to double and triple interaction of these three factors on compressive strength of cement pieces, which means different effects of water quality and application percent of zeolite on different content of cement, the choice of the best application level of zeolite and water type according to the cement content should be selected based on the mix design test in building site. However, using of briny grounwater and zeolite in the concrete mix design, especially in cement content of 350 kg.m3, without significantly reducing the compressive strength of concrete and even significantly increase of this property in some treatments, is recommended.