Matured slags

WASTOXHAS has been applied to bottom ash from municipal solid waste incineration (MSWI) and matured slags from the second smelting of lead (Ferrari and Ferard, 1999 Ferrari, 2000), ... 

Fig. 9.6 compares curves obtained on first intrusion for pastes of Portland and composite cements. At early ages, pfa or slag cement pastes are more porous than comparable Portland cement pastes because of the relatively slow reactions of the mineral additions, but the pore size distribution curves indicated by MIP are essentially similar in shape. For mature pastes, the apparent distributions for the composite cements indicate that there is a greater proportion of fine porosity. For the pfa cement paste, the mercury porosity obtained at maximum pressure are greater than that of the Portland cement paste. Day and Marsh (D32) agreed with Feldman that discontinuity... 

Calculations based on reaction stoichiometry and densities of phases support the conclusions from experimental observations that mature pastes of composite cements are more porous than comparable pastes of Portland cements. This is indicated by the results in Table 7.3, 9.4 and 9.6. Similar calculations for 180-day-old pastes of w/s 0.45 indicate free water porosities of about 24% for a typical Portland cement, 35% for a cement with 40% slag, 35% for one with 40% pfa and 32% for one with 30% microsilica. The calculated values are in all cases somewhat higher than observed mercury porosities (F34,F41). 

The resistivity of concrete is an important parameter used to describe, for example, the degree of water saturation, the resistance to chloride penetration or the corrosion rate. The resistivity of concrete may have values from a few tens to many thousands of n m (Table 2.3) as a function of the water content in the concrete (relative humidity), the type of cement used (Portland or blended cements), the iv/c, the presence of chloride ions or whether the concrete is carbonated or not At early ages, the resistivity of concrete is low and considerable increases occur due to hydration of the cement AU of these factors can be rationalised on the basis of ion migration in the porous and tortuous concrete microstructure a high relative humidity increases the amount of water-filled pores (decrease of resistivity), the iv/c ratio and type of cement determine the pore volume and pore-size distribution (less but more coarse pores with pure Portland cement more but finer pores and less interconnectivity of pores with blast furnace slag or fly ash) chloride ions increase the conductivity of the pore solution and carbonation decreases it. An increased resistivity is accompanied by a reduced corrosion rate [38]. Table 2.4 shows resistivities determined for mature concrete in various chmates [39-41]. 

---