STUDY OF BENTONITE USAGE IN ENVIRONMENTALLY FRIENDLY CONCRETE

Production of cement generates a huge amount of carbon dioxide emissions into the environment, utilization of pozzolanic materials in concrete is a better solution for this environmental problem. Several studies are conducted for using of pozzolanic materials such as fly ash, ground granular blast furnace slag, and silica fume as a pozzolanic material in concrete. A few studies were available on using bentonite in concrete. Bentonite is mainly clay contains rich amount of  silicain which obeys the pozzolanic properties. The objective of present study is to find out the effectiveness of using bentonite and waste rubber crumb in the design mix of concrete. An experimental investigation is performed on concrete mixtures to study the effect of using bentonite as a partial replacement of cement and conducting an environmentally friendly concrete using crumb rubber in the concrete mixtures as a partial replacement of fine aggregates. Cement is partially replaced by volume (2%, 5%, 10%, 15%, 20%) with Bentonite and fine aggregate is partially replaced (5%, 20%, 25%, 30%, 40%) with crumb rubber. Slump tests were conducted to evaluate the workability of fresh concrete. Compressive strength of cubes at 7days and 28 days, splitting strength and abrasion strength at 28 days are studied and compared with conventional concrete. A part of research work addresses the effect of using bentonite and waste rubber crumb on durability of concrete. For this purpose, specimens were submerged in solution containing 50 g/l of NaOH and H₂SO₄. Based on the test results, the ideal percentage of mix which shows maximum compressive strength is identified. The results showed that the compressive strength of the concrete was generally increases when bentonite replaced a part of the cement and decreases with the replacement of fine aggregates by the waste crumb rubber. Although the using of bentonite and crumb rubber decreases the compressive strength. The optimal mixture from the laboratory experimental investigation is 5% reduction of cement content and 20% of fine aggregates replacement that exhibited a compressive strength of 30 MPa at 28 days. The test results substantiate the feasibility to develop environmentally friendly concrete using bentonite and crumb rubber in the concrete mixtures.
 
فى هذا البحث ،تم دراسة استخدام البنتونیت کبدیل جزئی للأسمنت ومخلفات المطاط کبدیل جزئى للرکام الناعم فى الخرسانة الصدیقة للبیئة، تم مقارنة نتائج إختبارات قابلیة التشغیل ومقاومة الضغط و مقاومة الشد الغیر مباشر (الانفلاق) ومقاومة البرى والإستدامة بالخرسانة التقلیدیة.أوصت الدراسة بإمکانیة إستخدام البنتونیت حتى 5% کبدیل للأسمنت وإستخدام مخلفات المطاط حتى 20% کبدیل للرکام الناعم فى الخلطات الخرسانیة.