Cementitious mortar

The fire performance of passive fire protection using a layer of vermiculite/perlite (VP) based cementitious mortar was also investigated in [23]. Such a layer with a thickness of 15 mm was apphed on the bottom surface of the GFRP profile as 

Similar to that introduced in Section 9.4.1, the GFRP profile with the VP mortar layer was loaded mechanically, first to a constant level of 8 kN, and was followed by thermal loading according to the ISO fire curve. 

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The test material was a cementitious mortar made of a Portland cement CEM142.5 and sand with maximum grain size of 4 mm. The blend ratio was 1 3 cement to sand by mass. The water/cement ratio was 0.44. Five 140 x 140 x 560 mortar prisms were produced. After demolding they were stored under water for 90 days. The mortar is characterized by a compressive strength of 61.9 N mm , a bending strength of 8.83 N mm and a bulk density of 2.37 g cm (determined according to DIN-EN 196-1 [8] at 28 days). 

ISO 5725 [7] relies on a statistical analysis of variance model with two variance components "laboratory" and "repetition". Hence, a homogeneous material is assumed. Only under this homogeneity condition the calculated precision values are true method characteristics. For a heterogeneous material, like the tested cementitious mortar, the precision values are contaminated by the variance component of the material. Therefore, the precision values represent both material and method characteristics. 

It is remarkable that the pressure/volume curves of all samples have similar shapes regardless of sample preparation methods. They can be called a fingerprint of the porous material tested here, i.e. of the cementitious mortar with this composition. 

The precision of the mercury porosimetry method on the material class cementitious mortar was investigated by an interlaboratory study of six different samples. The results are summarized in the following points. 

Standard deviations and uncertainty intervals indicate a good precision of mercury intrusion measurements on cementitious mortars. The reproduce standard deviations are 1.5 to 2 times higher than the repeat standard deviations because the precision values are contaminated by the variance component of the heterogeneous material. 

The precision values are both method and material characteristics. They are valid for the tested material class, i.e. a cementitious mortar with this composition. 

Anti-foam agents are almost always used in SBR latex modified cement compositions because they increase mix density by minimizing air-entrainment, thereby upgrading physical properties. Anti-foam agents may be added to the SBR latex by the manufacturer of the latex and additional amounts may be added by the formulator of the final cementitious mortar composition. The amount of anti-foam added may range from 0.1% anti-foam solids on latex solids up to 3.5%. 

This PVA latex leaves a dried film which is flexible without the addition of a plasticizer. The film has excellent water resistance, light stability, good aging characteristics and good film consolidation. This particular PVA latex may be used as a film forming binder in a water-based emulsion paint. Its particular characteristics of compatibility with cement have led to wide uses of this latex as an adhesive and an admixture for cementitious mortars and concrete. 

When considering a cementitious mortar mix for use in the manufacturing of an ultra-lightweight thin film product, the addition of a suitable polymer modifier can enhance both the fresh and hardened properties of such lightweight material. The addition of styrene butadiene rubber latex (SBR) latex yielded the best overall results in terms of workability, formability, mouldability, flowability, compressive and flexural strengths. The improvements offered by the addition of the acrylic polymer were less impressive and the use of an acrylic modifier is thus not recommended for use in ultra-lightweight thin film products. It is also confirmed that small adjustments to the water cement ratio alter the workability of such mixes and may be used to tweak mix designs to suit specific applications and uses. Thus with the addition of either a SBR latex or acrylic polymer and... 

Increase cover to reinforcement with additional cementitious mortar or concrete... 

In addition to the temperature decrease, the cementitious mortar protection also introduced a considerable reduction of deflection at the midspan. As shown in Figure 9.3, the deflection after 30 min of fire exposure was only 49% of that without fire protection, and was also 20% less than that protected with CS board. 

The development of the midspan defection of the GFRP profile with intumescent coating is shown in Figure 9.3 and compared to the ones with or without fire protections. The GFRP profiles incorporated with intumescent coating and cementitious mortar demonstrated similar time-dependent deformation responses and further showed very similar fire resistance times (76 min vs 74 min). However, the former... 

Areas less than 10 mm thick can be hand repaired by applying proprietary cementitious mortar with or without polymer modifier. Polymeric mortars can provide physical protection to concrete but do not provide an alkaline environment. The substrate must be kept sufficiently wet to minimize the loss of water during repairing. Proprietary bonding coats may be added to provide strong bonding to the substrate. They are formulated from epoxy polymer or polyester polymer and they can be used without a primer. 

To meet today s technical requirements, almost aU dry mix mortars require polymer modification. Many cementitious mortars contain cellulose ethers as an additive to improve water retention and workabihty. However, after setting and drying they wiU adhere poorly or not at all to most of the substrates used in modern construction technology such as polystyrene panels, fiber panels, wood panels, closed and non-absorbent substrates or old tiles. In addition, cementitious mortars are very hard, brittle and inflexible materials, whereas for many apphcations flexible and deformable cementitious materials are essentiaL As a consequence for almost all apphcations in modern construction, the modification of cementitious mortars with polymers is a must In dry mix mortars the mineral binder, cement, and the polymer binder, redispersible powder, are ideal partners. The combination of both in a dry mix mortar... 

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