Detailed Analysis of Factors Affecting the Intensity of Foam Concrete

The introduction of pores in foam concrete, on the one hand, gives it lightweight, sound insulation, thermal insulation, high fluidity, and other properties that ordinary concrete does not have. Still, from the perspective of structure and mechanics, it also introduces a large number of defects, which leads to hardened foam Significant reduction in concrete strength. Because the porosity in foam concrete is generally as high as 50-70%, and the pore diameter is mainly above 10um, the intensity of foam concrete is much lower than that of ordinary concrete. Like regular concrete, the strength of foam concrete is not a fixed value. Different types of cement materials, cement dosage, concrete mix ratio, water-cement ratio, foam dosage (that is, different volume mass), concrete superplasticizer, curing system, and the use of other additives affects the strength of foam concrete.

1. The influence of material mix ratio
During the construction process, foam concrete may be prepared by using cement alone, or by using a mixture other than cement (such as silica fume, slag, fly ash, etc.), or fine aggregate (sand). The influence of the mix ratio on the strength of foamed concrete is mainly divided into three types:
(1) The higher the strength grade and the more the cement used, the higher the intensity of the foam concrete. Therefore, when it is desired to prepare foamed concrete with higher concentration, it is necessary to choose high strength grade cement.
(2) The introduction of mixed materials will cause the early strength of foam concrete t o be significantly reduced, but the impact on the later intensity is not significant. If an appropriate intensity stimulant is added, the reduction in initial intensity can be reduced. Besides, if ultra-fine mixed materials are used, such as silica fume and ultra-fine ground slag powder, the strength does not decrease much, and sometimes even increases.
(3) When sand is used as fine aggregate, the intensity of foam concrete will decrease in principle to different degrees. Still, the addition of sand will be very beneficial to improve the volume stability and reduce the shrinkage of hardened foam concrete. In actual construction, it is often the case that the mixed material and sand are mixed at the same time. Therefore, there is a suitable range of the proportion of foam concrete, which needs to be determined based on experiments.
2. Influence of the water-cement ratio
If only the internal structural changes of the foam concrete are analyzed, the increase of the water-cement rate will inevitably lead to a decrease of the strength. However, a large number of tests have proved that when the water-cement rate is increased within a specific range, the resistance will not only decrease but will increase. However, under the condition of low water-cement ratio, taking appropriate measures can also ensure that the cement slurry has good fluidity, so as to obtain high strength foam concrete.

3. Influence of conservation conditions
The curing conditions have a significant impact on the strength and strength development of foam concrete. Foam concrete has relatively large molding water ash, so early curing should be strengthened to prevent the strength from reducing and cracking caused by excessive evaporation of water. When the curing temperature is increased, the hydration speed of the cement is accelerated, and the early development of foam concrete is rapid. The intensity has some adverse effects.
4. The impact of concrete additives
The admixtures involved in Foam concrete are concrete foaming agents, concrete superplasticizer, and stimulants for admixtures. The specific foaming agent has a more significant effect on foam concrete. It is necessary to choose a foaming agent that has small side effects on the system, high foaming ability, and high foam strength. The activator mainly targets the addition of the admixture, which will cause the early strength of foam concrete to decrease. Decrease the magnitude of the reduction, but it will also reduce the ultimate intensity; the concrete superplasticizer mainly allows the system to mix the foam and slurry evenly at a lower water-cement ratio.

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