Tensile mortars

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. 

Gopalaratnam. V.S. and Shah. S P (1987). Tensile failure of steel fiber-reinforced mortar. ASCF.. 1. Fng. Mech. 113, 635-652. 

Grinding KNO3 with a mortar and pestle gives the impression that the crystals are weak and easily broken, as is indeed the case. This weakness is due to crystal defects where the tensile strength of each crystal can be several orders of magnitude less than the theoretical value. 

Mellon Institute on the effect of adding sugar to sand-lime bricks. It was found that the addition of 6% sugar (this amounts to 13 lb. of sugar per 1000 bricks) increased the tensile strength by about 60%. To summarize, it seems that sucrose exerts a beneficial effect on mortar and on sand-lime brick but a detrimental effect on Portland cement. 

The presence of the cement hydrate/polymer comatrix in LMM and LMC confers superior properties, such as high tensile and flexural strengths, excellent adhesion, high waterproofhess, high abrasion resistance and good chemical resistance, when compared to ordinary cement mortar and concrete. The degree of these improvements however depends on polymer type, polymer-cement ratio, water-cement ratio, air content and curing conditions. Some of the properties affected by these factors are discussed below [87, 88, 93-95]. 

Hsu, T.T.C. and Slate, F.O. (1963) Tensile Bond Strength between Aggregate and Cement Paste or Mortar. ACI Journal, Proceedings 60,4, 465 -85. 

Acrylic emulsions (or acrylic latices) are characterised as high-solids polymers having a film-forming temperature at or below room temperature (Lavelle, 1986). They have excellent hydrolysis resistance compared with other resins and are well suited as modifiers for portland cement mortars. Studies have shown that certain acrylic latices impart excellent workability at lower water demand, thin section adhesion and toughness, improved flexural strength and tensile strength and outstanding adhesion (Lavelle, 1983). 

C-307 Tensile strength of chemical-resistant mortars, grouts and monolithic surfaces. 

The prestressing mortars must have enough swelling capacity to accommodate, without disbonding, the tensile stresses imposed during the second stage of cure. 

This tensile strength was measured using dog bone specimens with a 1 in.xl in. (25 mm><25 mm) crosssection. The results of Table 1 show that RPUMRPE mortar exhibits an excellent tensile strength of about 1700 psi (11.72 MPa) after 7 days when the ratio (RPU RPE) ranges from 1 2 to 1 2.5. It can be seen that recycled polyurethane improves the tensile strength of the recycled polyester. 

Typical properties of RPUMRPE mortar in comparison to the hybrid recycled polyester (HRPE) mortar and recycled polyester (RPE) are presented in Table 6. The HRPE is hybrid polymer of recycled polyester and polyurethane which comes from F2 hybrid resin part A made by Amoco. The RPE is recycled polyester made by Alpha corporation. The bond, tensile and compressive strength, modulus of elasticity and shrinkage of these three kinds of polymer mortar were measured at 4, 8, 12, and 24 hours respectively. 

According to the ASTM C-884-78, delamination of the polymer mortar layer from the concrete test block or the presence of horizontal cracks in the concrete near the interface shall constitute failure. It is obvious from these results that the RPUMRPE mortar passes the ASTM C-884-78. After thermal cycling, no delamination was found in the specimens. The failure in all specimens in the shear and pull out tests occurred within the portland cement concrete substrate. These results depended on the tensile strength of the concrete substrate. 

Fig. 5. Comparison of Tensile Strength of Three Resin Mortars...

Sandwich specimens were made with core plates of pulp sand mortar reinforced by glass fiber mesh and aluminum sheet as shown in Fig. 1. Thickness of the aluminum sheet was 15 micrometers. Tensile strength... 

Brick linings, like other masonry structures, have low flexural and tensile strength but high compressive strength. Brick linings, especially on vertical walls, must, therefore, be designed so that the bricks and mortar are always under a compressive load-... 

Some anti-foam materials are based on silicone resins, others are based on petroleum oils, and all of them are intended to depress the surface tension of the latex emulsion. The anti-foam agents delay the entrapment of air in mixes which is always a possibility vdien mixing liquids and solids, such as a mortar in a cement mixer. This results in a denser mortar which has better abrasion resistance, better resistance to water absorption, and higher compressive, tensile and bond strengths. 

The physical properties of these mortars show phenomenally high flexural and tensile strengths, with little or no loss in compressive strength. For all practical purposes, a level of 2% as an addition cate, produces results which are outstanding, without excessive cost. Cured mortar specimens have been e qiosed to continuous water immersion with no loss in properties. ... 

Polymer-modified mortars can be obtained by replacing part of the mixing water with a synthetic latex (e. g. styrene butadiene or acrylate) to the mix. Although the binder is still cementitious, and thus alkalinity is guaranteed, the latex may improve the workability, the waterproofness, the carbonation and chloride resistance, the tensile and flexural strength of the repair mortar [8]. It can also reduce the modulus of elasticity, increase the bond to the substrate, reduce the rate of drying out and thus the rate of shrinkage. 

Method of test for tensile strength of polymer-modified mortar ... 

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