بررسي اثرات پخت تكميلي بر مشخصات مكانيكي بتن هاي پليمر- سيمان

The effects of post-curing on the mechanical properties of Polymer Cmement Concrete

امروزه استفاده از مصالح پليمري در صنعت ساختمان رشد روز افزوني داشته است. بر اين اساس از مصالح پليمري در ساخت بتن، جهت اصلاح مشخصات آن استفاده مي‌شود. سه نوع اصلي مصالح مركب بتن پليمري شامل پليمر تزريقي، پليمري و بتن پليمر– سيمان در صنعت ساختمان شناخته شده مي‌باشد. استفاده از انواع پليمرها و نحوه ساخت نمونه جديد، مي‌تواند مشخصات مكانيكي متفاوتي در رفتار بتن را باعث گردد. در اين تحقيق اثرات مربوط به تغييرات ميزان درصد وزني رزين پلي استر در ساخت بتن و اثرات پخت تكميلي بعد از ساخت در بتنهاي پليمر سيمان بررسي مي شود. بر اين اساس نمونه هاي استوانه اي بتن با سيمان پرتلند بدون پليمر، نمونه هايي كه ده، بيست و سي درصد وزني سيمان، پليمر در ساخت آن جايگزين شده، مورد ارزيابي قرار مي‌گيرند. همچنين اثرات مربوط به پخت تكميلي در ساخت نمونه‌هاي بتن‌هاي پليمر – سيمان (PPCC) مورد ارزيابي قرار مي‌گيرد. بر اساس نتايج به دست آمده اثرات استفاده از پليمر در ساخت بتن بر مشخصات مكانيكي از جمله مقاومت فشاري و مقاومت كششي و همچنين اثرات پخت تكميلي بر ساخت اين نمونه‌ها قابل توجه مي‌باشد.

It is well known that general concrete alone lacks excellent mechanical properties especially in tension, hence there is need for modification by polymers. Research on polymer concrete began in the 1950s and it has been actively used since the 1970s. The use of Polymer cement concrete is in rapid increase as it possesses improved qualities over conventional concrete. Adequate design of polymer concrete members requires appropriate understanding of its mechanical behavior.There are three kind of polymer concrete: A) polymer concrete (PC): this kind of polymer concrete is formed by polymerization a mixture of a monomer of a thermoset polymer and aggregate, B) latexmodified concrete (LMC):  this kind of polymer concrete is named polymer Portland cement concrete. In this way Conventional concrete is replaced with part of mixing water with latex and C) polymerimpregnated concrete (PIC): it is produced by impregnating or infiltrating a hardened concrete with a monomer then polymerization is done. There are many polymers that used in polymer concrete same as polyester, epoxy, styrene monomer and methyl methacrylate (MMA). Polyester concretes are viscoelastic and will fail under a sustained compressive loading at stress levels greater than 50 percent of the ultimate strength. Sustained loadings at a stress level of 25 percent did not reduce ultimate strength capacity for a loading period of 1000 hr. The main purpose of this paper is to investigate the effect of post curing effects on the mechanical properties of polymer cement concrete. Polyester was introduced to the mix as cement replacement by weight. A suitable concrete mix was designed and produced, using three different ratios of Polyester as cement replacement varying between conventional concrete for 0% Polyester to 30% Polyester. Two types of sles were cast, compacted and then cured for 28 days. The polymer concrete sles include two types, one has post cured and the other was without post curing. The cylinder specimens were tested in compression and split tension to determine the compressive and the tensile strength. The variation of compressive strength, tensile strength were determined and assessed for sles especially for sles with and without post curing. Based on the experimental program post curing has Significant effects compressive and tensile strength of concrete sles. The effect of weight percentage of polyester resin and post curing condition were investigated in relation to the mechanical properties of polymer concrete. The results indicate that an increase of polyester content in polymer concrete enhances the mechanical properties same as the tensile and compressive strength of the composite. Also, post curing increases mechanical properties, especially in the lower weight percent polyester. It seems that post curing causes increased degree of crosslinking in resin and increased the effect of polyester in the composite in lower percentage. It can be seen that post curing increased the mechanical strength for lower weight percentage of polyester more than the higher ones. In other words, lower weight percentage of polyester is more effective than the higher. This result comes from the effect of crosslinked density of polyester in polymer concrete composite because crosslinked density is very low when the weight percentage of polyester is low. Post curing can increase the crosslink density of polyester therefore increasing the mechanical properties of polymer concrete.