Mortars Porosity

Thermal Conductivity Test. Thermal conductivity measurements were carried out on mortars containing PU waste particles by using the guarded hot plate method, according to UNI 7745. Results obtained, reported in Table 4, showed that mortars containing 10% and 30% PU waste particles are characterized by thermal conductivity values 12% and 20% lower that reference mortar respectively. On the other hand, when limestone powder was added to the mixture, due to a lower mortar porosity, thermal conductivity was similar to that of the reference mixture. 

With respect to the mortar porosity and related properties, low amounts of aggregate result in significantly increased values, while the admixture of lime to the cement increases the porosity further. 

Cathodic protection can be used to protect steel in concrete (see Chapter 19). There is no fear of damage by H2 evolution due to porosity of the mortar. Local corrosion attack can be observed under extreme conditions due to porosity (water/ cement ratio = 1) and polarization (f/jq = -0.98 V) with portland cement but not with blast furnace cement, corresponding to field IV in Fig. 2-2 [53]. However, such conditions do not occur in practice. 

Current research related to biological additives is focused particularly on their influence on the properties of mortars, namely on porosity, tensile strength, compressive strength, drying shrinkage, etc. [23, 24, 26], The identification of proteinaceous additives used in historical buildings has been marginal for many years and no reliable methods are properly described in the literature. 

The reduction in porosity, decreased water content, and air entrainment that results when latexes are used in mortar and concrete mixes make them much more resistant to freezing and thawing conditions than conventional mortar and concrete. Figure 6.17 presents the freeze-thaw durability in water (-18 to 4°C) of combined water-and dry-cured SBR-, PAE- and EVA-modified mortars [98], The frost resistance of mortars made with these latexes is markedly improved even at polymer-cement ratios of 5%. However, an increase in the polymer-cement ratio does not necessarily produce further improvement in freeze-thaw resistance. EMM and EMC, when exposed to outdoor conditions involving freeze-thaw, UV radiation and carbonation show better weatherability when compared with conventional mortar and concrete. 

Recycled ABS can used as an additive that increases the compressive modulus of cement mortars. Unfortunately, ABS increases the porosity in the mortar. This effects a decreased adhesion strength to steel. However, by treating the ABS with maleic anhydride, a substantial increase in adhesive strength is obtained (128). 

Figure 2 shows a set of results for a catalyst powder (Super-D), manufactured by Crosfields Chemicals, Warrington, made from pellets by grinding with a pestle and mortar. Figure 2 portrays the extent of penetration of the pore volume as the pressure of mercury is increased. Also shown in the same figure are the results for pellets fractured into halfsize and quarter-size fragments. These results for powder, fractured pellets and whole pellets are to be used as a measurement framework for distinguishing the basic pore structure/pore size distribution of the interior porosity of the micro-porous particles and the intra-pellet pore spaces of the full pellet. 

A comparison of different methods to characterise the porosity of Egyptian mortars presented. The results obtained using adsorption manometry, mercury porosimetry and thermoporometry are complementary and overlap in certain regions of pore size. 

Some of the tar sands were extracted exhaustively with benzene-ethanol (3 1.) in a Soxhlet extractor to yield organic materials, and only those materials so obtained will be subsequently referred to as bitumens. This process does not remove all organic materials from some tar sands, and so another method of extraction was used. In the alternate procedure, tar sands first were pulverized in a mortar and pestle. Tnen the sample was transferred to Erlenmeyer fiasks and treated with successive volumes of n-heptane until less than 25 mg of material was dissolved. Each volume of heptane solution was filtered on a sintered glass funnel (coarse porosity), and the heptane then was removed. After heptane was observed to dissolve little material, the solvent was changed to benzene and after this to a mixture of benzene-methanol (1 1). Finally, the sands were extracted with several portions of warm pyridine. 

Fireclay refractories are divided into several groups according to their properties and quality. The main criteria are refractoriness, AI2O3 content, porosity and strength. The complex of properties then determines the field of application. In addition to shaped ware, granular fireclay mixes are also manufactured for the preparation of mortars in furnace construction, for repairs or for monolithic linings. 

Keywords asbestos-free mortar, autoclave curing, extrude, flexural strength, FRP powder, porosity, water curing... 

Jambor has, apparently, been able to relate the changes observed in the physical and mechanical properties of the specimens to changes in the bound SO3 content. These data, however, were not given in the paper. The data presented relate bound SO3 content to sulfate concentration, C3A content, and time of testing. It is these data upon which the damage function was based. As Jambor points out, the damage function is limited in that it does not take into account temperature effects, influence of the cement content in the mortars and concrete, total porosity of the composite material, as well as the Influence of the cross-section size of the structure. It does, however, serve to give a first approximation. 

Repeated dissolution and recrystallization of these salts leads to the mechanical disruption of the masonry structure. Since the salts will concentrate in the more porous material, either the brick or the mortar will be more seriously affected, depending on their relative porosity. 

The nature of mortar has changed considerably over time. The primitive clay based mortars gave way to the lime-sand formulation of the Romans with additions of plaster, crushed brick, and/or volcanic earth (pozzolan). The rediscovery of natural cements occurred in the eighteenth century and finally Portland cement was developed. Mortars in use changed accordingly to include the new products. In each case the type, size and amount of charge added in the mix has a large influence on properties such as the bulk density and porosity of the final product. 

The porosity of the bricks has an important function during the setting of the mortar between them. If the brick is fairly porous. 

In some of the precipitation processes, Et20-CF3S03H may be coprecipitated but may be removed readily by boiling the solid in chloroform for —0.5 hr after any solid lumps have been broken up using a mortar and pestle. ( Caution. Chloroform is toxic and a carcinogen this procedure must be performed in a well-ventilated fume hood.) The powder is collected on a medium-porosity frit and air-dried. 

Crete surface to the bulk of the concrete. Permeability is high (Figure 1.6) and transport processes like, e. g., capillary suction of (chloride-containing) water can take place rapidly. With decreasing porosity the capillary pore system loses its connectivity, thus transport processes are controlled by the small gel pores. As a result, water and chlorides will penetrate only a short distance into concrete. This influence of structure (geometry) on transport properties can be described with the percolation theory [8] below a critical porosity, p, the percolation threshold, the capillary pore system is not interconnected (only finite clusters are present) above p the capillary pore system is continuous (infinite clusters). The percolation theory has been used to design numerical experiments and apphed to transport processes in cement paste and mortars [9]. 

Avery useful aspectof latex-modified mortars and concretes is their improved adhesion or bond strength to various substrates compared to conventional mortar and concrete. The development of adhesion is attributed to the high adhesion of polymers. The adhesion is usually affected by polymer-cement ratio and the properties of substrates used. The data on adhesion often show considerable scatter, and may vary depending on the testing methods, service conditions or porosity of substrates. 

The pore structures of latex-modified mortar and concrete are influenced by the t)q)e of polymers in the latexes used and the polymer-cement ratio. Examples of their pore size distribution are illustrated in Fig. 4.60.1 Generally, the porosity or pore volume of the latex-modified mortar and concrete reduces in the large radii of 0.2 fim or more, and increases greatly in the smaller radii of 75 nm or less compared to unmodified mortar and concrete. The total porosity or pore volume tends to decrease with an increase in the polymer-cement ratio. This contributes to improvements in the impermeability and durability of the latex-modified mortar and concrete. 

The absorption characteristics indirectly represent the porosity through an understanding of the permeable pore volume and its connectivity. In order to investigate the effect of nano-Si02 particles on cement mortar permeability, a water absorption test was carried out on various mixtures A-1 (plain cement mortar), A-5 (cement mortar with 7% nano-SiO ), A-7 (cement mortar with 20% RHA replacement) A9 (cement mortar with 20% RHA replacement and 3% nano-SiO ). The final absorption of these mixtures are shown in Table 5.4. It can be seen that mixture A-5 (cement mortar with 7% nano-SiO ) showed the lowest absorption of all the mixtures which shows that nano-SiO is more effective in reducing the permeability than RHA. Integrating nano-SiO into RHA mortar reduced the water absorption from 5.42% to 4.45%. Results showed that the presence of nano-SiO particles in cement mortar could decrease the water absorption and the likely permeability of cement mortar. This impermeability increase can be attributed to two concomitant phenomena ... 

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