leca lightweight aggregate

Efforts to reduce the weight of concrete have led to extensive research on lightweight concrete. Reducing concrete weight can decrease the overall structure weight, thereby reducing the applied forces. This study investigates the effects of two lightweight aggregates, Leca and Scoria, on the properties of self-compacting concrete in both fresh and hardened phases, as well as its durability in sulfuric acid environments. Fresh concrete tests included slump flow, T50 slump, L-box, U-box, J-ring, and specific weight, while hardened samples were evaluated for compressive strength in both normal and acidic conditions, along with weight loss in acidic environments. Results indicated that three key factors influencing concrete performance are specific weight, appearance, and water absorption percentage of the aggregates. Scoria lightweight concrete demonstrated approximately 60% greater strength compared to Leca when using equal volumes of both aggregates. In acidic environments, the most significant reduction in compressive strength for Leca occurred between 1 and 7 days, approximately 27%, while for Scoria, this reduction was observed between 7 and 28 days at about 25%. This highlights that the acidic environment has a greater impact on the strength reduction of Leca in the early days and on Scoria in the later stages. Furthermore, the highest weight loss for both concrete types in acidic conditions was noted between 1 and 14 days, reaching approximately 93%, while only a 7% weight reduction occurred between 14 and 28 days. Notably, compared to their initial weight, the samples exhibited a minimal weight loss of about 1% to 2%.

The fire phenomenon can cause the loss of structural materials resistance which may end to damage or even structural total collapse. Physical and chemical changes in concrete due to firing also make serious structural defects in concrete structures. Therefore, prevention of reduction of concrete resistance is attended in this research. The primary idea is based on decreasing concrete thermal conductivity to increase chemical and physical resistance. Because of low density and porosity light weight aggregate concrete has low thermal conductivity which can postpone the resistant loss due to high temperature. A set of tests performed to achieve an optimum light weight aggregate concrete mix design in room normal temperature by changing the amount of sensitive mix components and controlling compressive strength and density. In next step some effective additives were implemented to make the optimum mix design against high temperature. For this purpose, 9 different mix designs obtained from the Taguchi method were prepared. For each mix design, 9 test specimens were made. At each, ambient temperature, 400 ͦC and 800 ͦC, three samples of each design are tested. The experiments conducted in this research include testing of compressive strength, ultrasonic pulse, and weight loss and heat effect on the appearance of lightweight concrete. It was seen that the effect of temperature above 400 ͦC is more significant on concrete compressive strength and in temperatures below 400 ͦC density loss is more considerable. The results of tests indicate that reducing the water to cement ratio and using super plasticizer has a desirable effect on the physical and mechanical properties of lightweight concrete at higher temperatures. However, test results showed that the presence of silica fume up to 15 percent of weight of cement can’t improve the strength of lightweight concrete neither in ambient nor in elevated temperature. Optimum mix design lost about 49 percent of compressive strength in 800 ͦC. Also it was observed that loss of density and compressive strength due to elevated temperature are in direct relation.

In this research, the punching shear strength of flat plate lightweight self-consolidating concrete and lightweight concrete slabs is studied. The experimental work consisted of 9 rectangular slab specimens with either 100 or 150 mm depth, 1000 mm length and 1000 mm width. The type of concrete, Strength of concrete and reinforcement varied in different tests. The slab dimensions and the area of reinforcing bars in slabs have been carefully designed so that the slabs failed due to punching shear. In a test, load and displacement were measured using a data acquisition system. Using the results, the behavior of slabs, cracking pattern and the slab stiffness were studied. The experimental results have been compared with the provisions of different codes. The comparison shows that the BS-8110 code estimates the punching shear of lightweight slabs most accurately. The slabs made by leca lightweight aggregates can be used in structures providing that they have a good mix concrete design.