بررسي اثر جايگزيني بخشي از مصالح سنگي با ماسه ريخته گري بر خواص مكانيكي و دوام ملات تعميري

تعمير و نگهداري سازه ها در طول عمر سازه امري اجتناب ناپذير مي باشد. بنابراين استفاده از يك ماده تعميري كه قابليت ارائه سرويس مجدد در زمان طولاني تري را داشته باشد، لازم مي‌باشد. امروزه توليد يك ماده تعميري كه پيوستگي كامل با المان آسيب ديده داشته باشد و بر اساس مصالح موجود در كشور داراي صرفه اقتصادي نيز باشد، ضروري است. از طرف ديگر افزايش ضايعات صنعتي، كمبود فضاي دفن زباله و افزايش هزينه‌هاي آن، بازيافت ضايعات صنعتي را به يك الزام تبديل نموده است. يكي از اين مواد زائد، ضايعات ماسه ريخته گري است كه حاوي رزين، پودر ذغال و بنتونيت مي باشد كه قابل حل در آب بوده و باعث انتشار مواد شيميايي خطرناك در محيط زيست مي‌گردد. در اين پژوهش نمونه‌هاي ملات و گروت با جايگزيني مقادير مختلف ضايعات ماسه ريخته گري با ماسه با هدف بررسي اثر جايگزيني بر خواص اين محصولات پايه سيماني، ساخته شده است. نتايج نشان مي‌دهد جايگزيني ضايعات ماسه ريخته گري كارايي ملات و گروت تا حدودي كاهش مي‌دهد. در رابطه با خواص سخت شده، جايگزيني 20% از اين ماده ضايعاتي باعث كمترين كاهش مقاومت فشاري ملات مي گردد اما جايگزين 10% از اين ماده باعث افزايش مقاومت فشاري گروت شده است. اثر اين مواد بر مقاومت خمشي نيز تقريباً همانند تغييرات مقاومت فشاري بوده است. با توجه به نتايج تحقيق حاضر آزمايش فراصوت كه بعنوان يك آزمايش كنترل كيفيت غيرمخرب براي مقاومت فشاري بتن بكار مي رود، قابليت تخمين مقاومت فشاري و خمشيِ ملات و گروت را ندارد.

Maintenance and repair of structures during the life of the structure is inevitable. Therefore, using a repair material that have the ability to re-service in a longer time is necessary. Today, produce a repair material that has a complete bond with the damaged element and makes it economical based on the available materials in the country is necessary.On the other hand increasing the quantities of waste materials ,scarcity of land-filling space and because of its ever increasing cost,recycling industrial waste materials has become an attractive proposition to disposal.One of these by-products is waste foundry sand. Waste foundry sand that contains resin, coal powder and bentonite which are solvable in the water and leads to environmental pollution. Therefore, industry owners are looking for a solution to the problem of organic waste due to pressure from environmental organizations.One of these solutions is dumping of construction waste in cement products such as concrete, mortar and grout. In this research, with the aim of reaching mortar and grout with good performance and durability, as well as up to 40 MPa compressive strength of 28 days, the initial mixture ratios were determined and the final mixture was determined by making laboratory samples and correction of ratios. 5 mixtures for mortar and 5 maixtures for grout. In the mixtures for all mortar and grout samples, the ratio of water to cement is fixed at 0.4 and the cement content of the mortar samples is 650 kg/m3. Natural sand mortar samples have been replaced with 10, 15, 20 and 25 percent waste foundry sand. The amount of cement for grout samples is 1100 kg / m3. In grout mixtures, 10, 15, 20, and 25 percent of sand have been replaced by waste foundry sand (WFS). The results indicate that replacing WFS reduces the workability of mortar and grout. The compressive strength of the mortar samples is reduced by replacing different amounts of WFS at the age of 7 and 28 days. Mortar with 20% replacement of WFS, is the optimum percentage of waste sand in the mortar. However, the compressive strength of the grout samples increases by replacing 10% casting sand. By increasing the replacement value by more than 10%, the compressive strength decreases. Based on various studies in concrete, ultrasonic velocity test (as a non-destructive test) is used to estimate the compressive strength, which has a linear correlation between ultrasonic wave velocity and compressive strength. But the results of this study showed that the non-destructive test of ultrasonic waves does not have the ability to estimate the compressive strength and the flexural strength of the mortar. This result was also observed in Grout samples. Therefore based on the results of this research the ultrasonic velocity test does not have the capability to estimate the compressive and flexural strength of mortar and grout. Despite the decrease in the mechanical properties of the mortar by replacing WFS, the water absorption of the mortar containing this material has decreased, which is up to 15%. But by increasing the replacement percentage by up to 25%, the volumetric absorption of the samples of the grout decreases.