Air Hardening Inorganic Air Hardening Inorganic Binding MaterialsBinding Materials

Chapter 2Chapter 2

Chapter 2

§2.3 Lime

Preparation of lime (quick lime)Slaking and hardening of limeTechnical properties of gypsumApplications

Preparation of lime

CaCO3 CaO 1000 ～ 1100℃ CO2 ＋MgCO3 MgO

Preparation of lime : lime stone was heated and decompounded into quick lime.

MgO≤5 ％ Calcium quick limeMgO≥5 ％ High-magnesium quick lime

According to MgO content, there are two types of quick lime:Calcium quick lime and high-magnesium quick lime.

Preparation of 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

According to temperature and time of the preparation , there are 2 types of quick lime: over-burnt lime and under-burnt lime.

Preparation of lime

Slaking and hardening of lime

1

Slaked lime

Quick lime reaction with water gives slaked lime

QOHCaOHCaO 22 )(

Slaking method: It will take more than two weeks to use the quick lime in the water.

The characteristics of the reaction is that:①the large exothermic amount and the quick exothermic speed②volume increase ： 1 ～ 2.5 times

1

Slaking and hardening of lime

2

OHNCaCOOnHCOOHCa23222

)1()(

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.

Slaking and hardening of lime

2

The process of hardeningCrystallization Carbonization

Ca(OH)2

crystal birthCa(OH)2

crystal birthMain changes

CharacteristicsReacting

quickly inside

Crystal from

outside to inside

making CaCO3

Technical properties of gypsum

1

a. Building quick lime （ JC/T479-92 ）(1)Technical standardThe content of CaO+MgO 、 the content of CO2 、the content of unhydrated grain and the content of paste.(2) ClassificationCalcium quick lime and high-magnesium quick lime. (3) GradesTop-rate materials, first-rate materials, qualified-rat

e materials.

b. Building ground lime （ JC/T480-92 ） :(1)Technical standardThe content of CaO+MgO and CO2

(2) ClassificationsCalcium ground lime and high-magnesium gro

und lime(3) GradesTop-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) ClassificationsCalcium ground slaked lime, high-magnesium ground slaked lime and dolomite ground slaked lime.

(3) GradesTop-rate, First-rate, Qualified-rate

Technical properties of gypsum

2

a.Quick setting and hardening, low strength

b.Good plasticity of paste （ rich water retentivity ）

c. Large shrinkage of volume d. Poor water resistance

Technical properties of gypsum

Ground quick lime, Ground slaked lime, Lime pasteImprove the utilization ratio of limeSilicate products ：Example ： lime-sand brick, Carbonated lime boardMaking cement without clinkerGround quick lime + active blended materials + gypsumGround quick lime +sand +water

Applications

Chapter 2