Mechanical Properties and Dynamic Response of Lightweight Reinforced Concrete Beam


The study is conducted to perform two goals: The first geal is to produce alightweight concrete using major components which are locally available withsome standard admixtures.Many mixtures are prepared using many ratios ofsuperplasticizer (SP) and silica fume (SF) admixtures to yield a lightweightaggregate concrete, the effects of using different ratios of these admixtures on unitweight, compressive strength and flexural strength are studied individually andaccumulatively. The secondis to study the dynamic specifications of normal andlightweight reinforced concrete beams.The results showed that the increasing in dosage of superplasticizer (SP) for(LWAC) increases the density of (LWAC), and the increasing in dosage of silicafume (SF) decreases the density of (LWAC). The experimental impact tests forR.C. beams shows that the lightweight R.C. beams have a better response underimpact loading with respect to the maximum dynamic deflection (2.955mm fornormal weight beam and 1.58mm for lightweight beam). Also,Impact forcetransferred to supports reactions of lightweight beams is smaller within 45% thanthe impact force transferred to reaction of normal weight concrete under the sameimpact load, and the time to reach 90% damping equal to 1.223 sec and 1.6 sec forlightweight and normalweight R.C. beams respectively. Also, the reinforcedconcrete beams are tested under repeated impact load up to failure. The testsshowed that the no. of blows to cause first crack for lightweight concrete beamsmore than twice of this for normalweight concrete beams.