Experimental study on mix proportions of similar materials to reef limestone

Reef limestone is different from conventional terrestrial rocks and is characterized by high porosity, low density, and low strength. To study similar materials applicable to model tests of reef limestone, reef limestone was classified into four types, i.e. weakly-cemented and dense (WD), strongly-cemented and dense (SD), weakly-cemented and loose (WL), and strongly-cemented and loose (SL) according to measured data. Sixteen test schemes were designed for mix proportions to prepare similar materials by using an orthogonal scheme. Therein, the foaming agent, powdered talc, sea sand, cement, gypsum powder, and air-entraining agent were used as base materials, and the cement/gypsum ratio, foaming agent/water ratio, and talc/water ratio were taken as controlling factors for the density, porosity, and uniaxial compressive strength (UCS). The physico-mechanical parameters of the similar materials were evaluated using range analysis. Results show that the foaming agent/water ratio exerts a strong controlling effect on the porosity and UCS and a certain controlling effect on the density; the cement/gypsum ratio and the talc/water ratio both have certain controlling effects on the density and UCS while do not exert obvious controlling effects on the porosity. On this basis, the mix proportions were optimized and the optimal mix proportions that separately meet similarity requirements of the above four types of reef limestone were obtained. That is, the ratios of the cement/gypsum ratio, foaming agent/water ratio, and talc/water ratio are separately 2.5:0.03:0.1, 2:0.02:0.15, 3.5:0.04:0.15, and 3:0.01:0.2.