Physically foamed concrete insulation block

The invention relates to a physically foamed concrete insulation block and belongs to the field of building materials. The physically foamed concrete insulation block comprises the following raw materials in percentages by weight: 35-90% of ordinary portland cement, 5-35% of fly ash, 2-10% of silica fume, 0.1-1% of calcium stearate, 0.1-0.8% of polycarboxylate water reducer, 1-8% of calcium nitrate and 0.2-0.5% of a cement foaming agent; the preparation method of the physically foamed concrete insulation block comprises the steps of mixing ordinary portland cement, fly ash, silica fume, a calcium stearate polycarboxylate water reducer and calcium nitrate, putting the mixture and water according to a weight ratio of the solid to water being 1: (0.4-0.6) into a stirrer, stirring to form suspension cement slurry; putting the cement foaming agent at a weight ratio of the solid to water being 1: (30-40) into a foaming device, processing into a foam of which the percentage by closed pore is 90-98% and the diameter is 0.2-2 mm; and uniformly mixing the cement slurry and the foam to form foamed concrete, pouring the foamed concrete into a mold by a delivery system, demolding after 12 hours, shading and curing by spraying water.