كليدواژه :
تثبيت , سيمان , زئوليت , مقاومت فشاري تك محوري , چند جمله اي
چكيده فارسي :
ماسه هاي سيماني به عنوان يكي از موضوعات اقتصادي و زيست محيطي در تثبيت خاك شناخته مي شوند. در برخي موارد تركيبي از سيمان و ماسه با ساير مواد از جمله فيبر، شيشه، نانو ذرات و يا زئوليت مي تواند به طور موثر در تثبيت خاك در جاده سازي استفاده شود. در اين بررسي زئوليت به عنوان يكي از مواد افزودني به سيمان و اثرات آن بر مقاومت فشاري تك محوري مورد ارزيابي قرارگرفته است. در اين راستا از زئوليت نوع معدني كلينوپيلوليت، سيمان تيپ II نكا و ماسه بابلسر به عنوان خاك پايه استفاده شد. تعداد 144 آزمايش مقاومت فشاري تك محوري بر روي طرح اختلاط 24 حالت سيمان و زئوليت شامل درصد سيمان هاي مختلف 2، 4، 6 و 8 درصد وزن خشك كل نمونه و درصد هاي جايگزيني 0، 10، 30، 50، 70 و 90 زئوليت نسبت به سيمان با تراكم نسبي هاي 50، 70 و 85 درصد در مدت عمل آوري 7 و 28 روز انجام شد. نتايج نشان مي دهد كه با جايگزيني 30% زئوليت به جاي سيمان نسبت به نمونه هاي بدون زئوليت، مقاومت فشاري تك محوري، به ميزان 20 تا 78 درصد افزايش مي يابد. همچنين در اين فرآيند كرنش گسيختگي نمونه ها نيز زياد مي شود. نرخ افزايش مقاومت فشاري تك محوري براي نمونه هاي با درصد سيمان هاي بالاتر و تراكم كمتر، بيشتر است. همچنين نتايج حاكي از ارتباط تواني مقاومت فشاري تك محوري با پارامترهاي وزني سيمان، زئوليت و تخلخل (چند جمله اي از وزن هاي سيمان و زئوليت/تخلخل) مي باشد.
چكيده لاتين :
Soil stabilization with cement has for many years been a ground improvement technique for some engineering applications such as construction of stabilized bases under pavements, canal lining and engineered fills. This reliable and simple soil improvement technique can provide great advantages including increasing shear strength parameters and avoiding the use of borrow materials from elsewhere. The compressive strength of artificially cemented soils has been studied by many researchers. On the other hand, using additive fiber, glass, fly ash, silica fume and nano particle in cement stabilization industry has several advantages. There are few studies about the effect of natural zeolite as an additive material on the cemented sand. Natural zeolite, an extender, has been investigated for use as cement and concrete improver by some researchers. In this study, the use of a natural zeolite additive, as a potential improver of cemented sand is investigated. Natural zeolite contains large quantities of reactive SiO2 and Al2O3. Similar to other pozzolanic materials, zeolite substitution can improve the strength of cement by pozzolanic reaction with Ca(OH)2, can prevent undesirable expansion due to alkali- aggregate reaction, reduce the porosity of the blended cement paste and improve the interfacial microstructure properties between the blended cement paste. It has been observed that pozzolanic activity of natural zeolite is higher than that of fly ash but lower than that of silica fume. It was concluded that the clinoptilolite blend decreases the specific gravity of cements. There are several investigations about the relationship between unconfined compressive strength (qu) and voids/cement ratio of cemented sand. However, existing equations based on voids/cement ratio cannot estimate qu values of zeolite cemented sand mixtures properly. In this research, a series of laboratory tests have been performed to investigate the mechanical characteristics of zeolite cemented sand. The effect of zeolite, cement and porosity on behavior is evaluated in term of qu. Therefore, cilinopiolite kind of zeolite, Neka cement type II and Babolsar sand are used in this study. A total number of 144 unconfined compression tests were carried out on 24 combination type of cement and zeolite include different cement percentages 2, 4, 6 and 8 percent of total dry weight of samples and replacement percent’s of 0, 10, 30, 50, 70 and 90 zeolite with cement based on 50,70 and 85% relative densities in7 and 28 days curing times. Results show qu and failure properties improvements of cement sand specimens when cement replaced by zeolite at optimum proportions of 30% after 28 days due to pozzolanic reaction. For 28 day curing time, by replacement percentage of 30 zeolite material by cement, the unconfined strength increased 20 to80% in comparison with cemented samples by increasing shear strain. For higher cement content and less compacted blends, these improvement rates are more. The addition of zeolite to the cement sand mixture can makes increase strain at failure, and reduce brittle behavior. At the end, a power function fits presented to relate qu and zeolite-cement-soil parameters (porosity (n) and voids/ polynomial model of cement and zeolite voids).
