火灾条件下轻质泡沫混凝土抗压强度衰减规律研究

Study on the compressive strength attenuation regularity of light-foam concrete under fire condition

为了研究轻质泡沫混凝土在火灾条件下的抗压强度衰减规律,利用实验室自制的复合发泡剂制作低密度泡沫混凝土标准试块,养护28 d后进行煅烧试验,测定其抗压强度值,并计算强度损失率。结果表明,即使泡沫混凝土具有不燃特性,其抗压强度仍然会在高温条件下呈现一定的衰减规律:在模拟火灾条件下,随着泡沫混凝土干体积密度的增加,其抗压强度损失率不断减小;密度为200 kg/m3、300kg/m3和400 kg/m3的泡沫混凝土试块,在800℃高温下煅烧20 min,其强度损失率分别为67.8%、53.2%和47.3%;300 kg/m3泡沫混凝土试块在不同温度下煅烧,强度损失不同,温度越高,损失越大,在300℃下,其强度损失仅为37.2%;煅烧时间对不同密度泡沫混凝土的抗压强度损失率有一定影响,并且规律相似,随时间的延长,损失率趋于平稳;密度为400 kg/m3的泡沫混凝土在800℃火焰下煅烧30 min后,强度保留约50%;增强剂的使用对火灾条件下泡沫混凝土抗压强度的损失有一定影响,增强剂取代水泥的比例增大,其火灾条件下的强度损失率减小。选用水化生成的结构在火灾或高温条件下保持不变的胶凝材料制作泡沫混凝土,对建筑防火具有积极意义。

This paper is dedicated to our experimental results on the compressive strength attenuation regularity of light-foam concrete un- der the fire condition. The experiments have been done with the low- density foam concrete made by using our self-made composite foam a- gent. Our experiments were done in the following way： after 28 days in preservation, the calcinations tests were arranged to be done with the said concrete, first of all, to determinate the compressive strength, and then to work out the strength-losing rate. The results of our experiments show that, even with no combustion features, com- pressive strength of the foamed concrete under high temperatures is still in certain attenuation： in simulated fire condition, with the in- crease of dry density, losing rate of the foam concrete under the fire condition the compressive strength tends to decrease. Statistically speaking, its strength loss rate of the foam concrete block with its density of 200 kg,/m3, 300 kg/m3 and 400 kg,/m3, at 800 ℃ calci- nations in 20 min, should be found equal to 67.8 % , 53.2 % and 47.3 %. In addition, the strength loss for the foam concrete block calcinated in different temperatures with the density of 300 kg/m3, can be different. That is, the higher the temperatures, the greater the loss would be. At 300 ℃ , its strength loss is only 37.2%, however,at 800 ℃, its strength loss turns to be 53.2%. With the increase of calcinations＇ time, the strength loss rate of different densities of the foam concrete tends to show an ascending trend, though the rising rate tends to decrease. Different densities of foam concrete compres- sive strength loss rate have a certain influence with a rule being simi- lar, When the calcinatipg time lasts longer, the loss rate would get smooth. For the foam concrete with its density of 400 kg/m3, when calcinated after 30 minutes, it remains possible to keep its intensity at 50%. When ordinary Portlant cement was reinforced with the strengthening agent for partial replacement, the strength loss of the foamed concrete is likely to be affected. The greater the strengthening agent prooutletion, the longer the compressive strength increases whereas the strength loss rate decreases under the fire condition. Therefore, it is of positive significance to produce foam concrete that can keep the same hydration generated structure in the fire or under high temperature by using the cement material for building fire protec-