Chapter 2 Air Hardening Inorganic Binding Materials
§2.3 Lime Chapter 2 Preparation of lime (quick lime) Slaking and hardening of lime Technical properties of gypsum Applications
Preparation of lime quick lime Preparation of lime : lime stone was heated and decompounded into quick lime. CaCO3 CaO 1000～1100℃ CO2＋ MgCO3 MgO quick lime
Preparation of lime According to MgO content, there are two types of quick lime: Calcium quick lime and high-magnesium quick lime. MgO≤5％ Calcium quick lime MgO≥5％ High-magnesium quick lime
Preparation of lime According to temperature and time of the preparation , there are 2 types of quick lime: over-burnt lime and under-burnt lime. tem\time↑→ over-burnt lime：clay melts, fills or enwraps the surface of lime →high solidity→lime slakes slowly tem\time↓→ under-burnt lime：CaCO3 does not decompose enough and the productivity is low
Slaking and hardening of lime Slaking of quick lime： 1 Quick lime reaction with water gives slaked lime Slaked lime Slaking method: It will take more than two weeks to use the quick lime in the water.
Slaking and hardening of lime Slaking of quick lime： 1 The characteristics of the reaction is that: ①the large exothermic amount and the quick exothermic speed ②volume increase ：1～2.5 times
Slaking and hardening of lime 2 The process of hardening includes : crystallization and carbonization. Ca(OH)2 crystal is formed in crystallization, whose characteristics is quick reaction inside. CaCO3 is formed in carbonization, when Ca(OH)2 absorbs CO2 in the air, whose characteristics is slow reaction and crystal from outside to inside.
Hardening of lime 2 The process of hardening Crystallization Carbonization Ca(OH)2 crystal birth Main changes Characteristics Reacting quickly inside Crystal from outside to inside making CaCO3
Technical properties of gypsum 1 Technical standard： Building quick lime （JC/T479-92） (1)Technical standard The content of CaO+MgO、the content of CO2、 the content of unhydrated grain and the content of paste. (2) Classification Calcium quick lime and high-magnesium quick lime. (3) Grades Top-rate materials, first-rate materials, qualified-rate materials.
Technical properties of gypsum b. Building ground lime（JC/T480-92）: Technical standard The content of CaO+MgO and CO2 (2) Classifications Calcium ground lime and high-magnesium ground lime (3) Grades Top-rate materials, first-rate materials, qualified-rate materials
Technical properties of gypsum c. Building ground slaked lime （JC/T481-92）: (1)Technical standard The content of CaO+MgO、free water、soundness and fineness (2) Classifications Calcium ground slaked lime, high-magnesium ground slaked lime and dolomite ground slaked lime. (3) Grades Top-rate, First-rate, Qualified-rate
Technical properties of gypsum 2 Properties: Quick setting and hardening, low strength Good plasticity of paste（rich water retentivity） c. Large shrinkage of volume d. Poor water resistance
Applications Ground quick lime, Ground slaked lime, Lime paste Improve the utilization ratio of lime Silicate products： Example： lime-sand brick, Carbonated lime board Making cement without clinker Ground quick lime + active blended materials + gypsum Ground quick lime +sand +water
Chapter 2 THE END