BASICS OF CONCRETE SCIENCE - CHAPTER 10 pptx

CHAPTER 10 CONCRETE ON THE BASIS OF NON-CLINKER BINDERS MORTARS AND DRY PACK MIXES L Dvorkin and O.Dvorkin Along with concrete on the basis of Portland cement and high-alumina cement there are used different concrete on the basis of other non-organic and organic binders in construction industry Mortars are composite heterogeneous materials which differ from concrete only by absence of coarse aggregate and poured as a rule on the basis with thin layer 10.1 Silicate concrete Unlike ordinary concrete, silicate concrete is produced on the basis of limesand binders of autoclave curing The same classification by structural features and purposes as for ordinary concrete is appropriate for silicate concrete Extension of silicate materials started from 1880 when V.Michaelis has suggested silicate brick Foundational idea of silicate materials obtaining is lime-sand composites hardening as a result of hydrosilicate synthesis at raised temperature and pressure of vapour 187 Fine powder lime-sand binder that has as a rule high activity (25-35% of active СаО+MgO) can be substituted by lime-slag or fly ash binder with lower activity by content of active calcium and magnesium oxides (10-15%) At that lime content reduces in the mix approximately in 2-3 times Silicate concrete strength varies within wide range: from 5-10 MPa for lightweight concrete to 80-100 MPa for high-strength heavyweight concrete Dense silicate concrete strength at anhydrous lime application can be determined approximately by formula:  Sg.s 1,6   R с = 4.05 (10.1) +  100 C / W −  + 18,   Where Sg.s is specific surface of sand, m2/kg; C/W is cement-water ratio When hydrated lime is used: С  R с = 16 l − 1 + 14,  W (10.2) Where Cl is lime-sand binder content, kg/m3; W – quantity of water, kg/m3 188 Content of active calcium oxide in silicate concrete mixture varies depending on required concrete strength taking into consideration fineness modulus of sand (Tab.10.1, Fig.10.1, 10.2) Table 10.1 Content of active СаО, % by mass of compacted silicate concrete mix Strength of concrete, Sand ultra fine fine medium coarse 15 6.5 6.2 5.8 25 7.5 7.2 6.5 30 8.5 7.5 40 10.5 9.5 8.5 MPa 189 Compressive strength, MPa Compressive strength, MPa 7.5 Content of active СаО in mass, % Fig 10.1 Effect of active СаО in the mixture on compressive strength of lime-sand specimens: – on the basis of quartz sand; – on the basis of feldspar sand 15.0 22.5 27.5 Content of sand, % Fig 10.2 Relationship between silicate concrete strength and sand content with specific surface: - 4500 cm2/g; - 2500 cm2/g; - 1500 cm2/g Content of active СаО in the mixture is 12.5% 190 10.2 Slag and fly-ash concrete Concrete on the basis of lime-slag and lime-ash binders, gypsum-slag, sulfate slag and slag non-clinker cements can be classified as such concrete Slag-alkaline concrete can be referred to a separate group Chemical activity of slag is defined by quality coefficient К, calculated according to following formulas: - at magnesium oxide (MgO) content up to 10% К= CaO + Al O + MgO , SiO + TiO (10.3) - at magnesium oxide (MgO) content more 10% К= CaO + Al O + 10 SiO + TiO + (MgO − 10 ) (10.4) 191 Ash is divided on high-calcium (СаО>20%) and low-calcium (СаО