Mechanical Properties Of Cement Mortar Research Articles

Modification of Polypropylene Fibers by Acrylic Acid and its Influence on the Mechanical Property of Cement Mortar

The surface of the PP fibers were modified by acrylic acid and grafted by suspension in water medium. The effect of modified PP fibers on mechanical properties of cement mortar was studied. The microstructure of fibers surface, the active functional groups of fibers and the profile of cracked samples were analyzed by SEM and IR. The results show that, crylic acid was grafted on surface of PP fibers after modification; the flexural strength of cement mortar reinforced by modified PP fibers improved markedly, compared with cement mortar reinforced by ordinary PP fibers.

Mechanical Properties and Microstructures of Cement Mortar Modified with Styrene-Butadiene Polymer Emulsion

In this paper, styrene-butadiene polymer emulsion SD622S was adopted to modify cement mortar; mechanical properties of cement mortars were studied and microstructures was analyzed by means of Scanning Electron Microscope (SEM) and Specific Surface Area & Pore Distribution Analyzer. The results show that in contrast to ordinary cement mortar, if water to cement ratio (W/C) is constant, compressive strength of modified cement mortar can decrease, while flexural strength and toughness, ratio of compressive strength to flexural strength, increase with the increase of polymer to cement ratio in mass (P/C) at 7 and 28 curing days. With the increase of P/C, net structure made from polymer and cement hydration products is developed and pore whose size is smaller than 200Å begins to increase, which indicates pore diameters in modified cement mortar change to be finer. So microstructures of modified cement mortar become denser and display higher toughness.

Hybrid modified rubber powder and its application in cement mortar

This research focused on using the waste rubber powder as a kind of regenerate resources to improve the mechanical properties of cement mortar. The two kinds of hybrid modified rubber powder TRP and ATRP were prepared by sol-gel method and then used in cement mortar. The structures and properties of them were studied. It is shown that the nano Si-O-Si network is generated in TRP and ATRP networks and the hydrophilic group is grafted on the surface of ATRP. The mechanical properties of rubber-treated mortar (RTM) were tested and the microstructures of them were also studied. Compared to the mortars with unmodified rubber powders (RP), NaOH treated rubber powder (SRP) and coupling agent treated rubber powder (CRP), the RTM with ATRP has the highest compressive strength and flexural strength. The stress-strain curves shown that the peak of stress of RTM with ATRP is increased and indicated the higher compression deformation and toughness. It is found that the interfacial adhesion between the ATRP and cement mortar is increased distinctly by SEM, which results in enhanced ductility and mechanical properties of RTM with ATRP.

Influence of the Oxidation Process of Carbon Material on the Mechanical Properties of Cement Mortars

The present research investigates how the addition of processed carbon materials affects the mechanical properties of cement mortars. Five types of oxidation treatments (air at 250°C, air at 410°C, ozone, H2O2, and HNO3) were applied to graphite powder, powdered carbon fiber, and short carbon fiber to assess the influence of the modification of the carbon material surface in the interaction between cement paste and carbon material. The best oxidation treatment in terms of mechanical strength improvement was oxidation by air at 410°C because this procedure yielded the highest amount of oxygen surface functional groups, thus producing a better interaction with cement paste. Ozone treatment has also been shown to produce a high level of improvement in mechanical properties, but in this case the properties are improved because of the rough surface of the carbon materials.

Influence of Nano-SiO2 Addition on Microstructure and Mechanical Properties of Cement Mortars for Ferrocement

Because of their unique physical and chemical properties, nanoparticles have been gaining increasing attention and have been used in many fields to fabricate new materials with novel functions. If nanoparticles are integrated with cement-based building materials, the new materials might possess some outstanding properties. Ferrocement is a type of thin-wall reinforced concrete commonly constructed of hydraulic cement mortar reinforced with closely spaced layers of continuous and relatively small-sized wire mesh. The low level of technical skill required to make ferrocement and the ready availability of its materials make ferrocement suitable for a wide variety of applications. This study investigates the mechanical properties (compressive and flexural strengths) and microstructural properties (as determined by scanning electron microscopy) of the interfacial transition zone between cement pastes and aggregates of mortars applicable for the casting of thin ferrocement elements combining with nanosilica. Study parameters include the ratio of nanosilica to cement in ordinary portland cement mortar mixtures (including 1%, 2%, and 3%) and the water-to-binder ratio (including 0.35 and 0.4). The results show that cement mortars containing nanoparticles have a reasonably higher strength and denser interfacial transition zone than do ordinary portland cement ferrocement mortars, while the flowability of mortars with and without nanoparticles is considered equal.

Predicting The Relationship Between The Modulus Of Rupture And Compressive Strength Of Cement Mortar

The present paper deals with studying the effect of sand/cement (s/c) ratio and water/cement (w/c) ratio on the mechanical properties of cement mortar and to predict a relationship between modulus of rupture and compressive strength for the cement mortar. In the present work seventy two sample of cubes and prisms were tested for compressive strength and modulus of rupture. All the tests were carried out in accordance to the ASTM specification C109 using twelve different mix proportions of cement/sand ratio and water/cement ratio. From the test results and based on regression analysis a best power relation between modulus of rupture and compressive strength are proposed.

Physical and mechanical properties of styrene–butadiene rubber emulsion modified cement mortars

Polymer-modified cement mortars were prepared by varying polymer/cement mass ratio (P/C) with a constant water/cement mass ratio of 0.4. The effect of styrene–butadiene rubber (SBR) emulsion on the physical and mechanical properties of cement mortars is studied. With P/C below 10%, the toughness of the modified mortars enhances with the increase of P/C. A relationship between the physical and mechanical properties of the modified cement mortars at P/C below 10% is found; that is, the compressive strength and flexural strength of the modified mortars are directly proportional to the apparent bulk density. But when P/C is above 10%, the mechanical properties are not highly dependent on the apparent bulk density, and the flexural and compressive strength of the mortars are not improved further with more polymer. Two curing methods [wet cure: 2, 6 or 27 days immersed in 20 °C water; mixed cure: 6 days immersed in 20 °C water followed by 21 days at 20 °C and 70% relative humidity (RH)] were also evaluated in this paper. The results have shown that the mixed cure is more beneficial to the improvement of the mortar properties. A possible mechanism for polymer modification and the relationship between the physical and mechanical properties is proposed based on SEM and IR analyses. The interpenetrating structure between the polymeric phase and cement hydrates forms at a P/C of 8%, and fully develops at a P/C of 10%. The properties of the polymer-modified mortars are influenced by the polymer film, cement hydrates and the combined structure between the organic and inorganic phases.

Some Engineering Properties of Limestone Concrete

In order to reduce energy consumption and CO2 emission and increase production, cement manufacturers are blending or intergrinding mineral additives such as slag, natural pozzolans, sand, and limestone. The reduced cost of limestone is mainly due to energy savings by substitution of a portion of the calcined clinker with a small amount of limestone and to the presence of limestone deposits near cement kilns, and hence, reduced transportation costs. This paper reports on a preliminary study underway on the performance of limestone cement mortar and concrete. The effect of different levels of limestone cement replacement (0% to 35%) on physical and mechanical properties of cement mortar is reported, as well as the effect of fineness of both clinker and limestone. From the test results, it was found that it is possible to manufacture cement with limestone addition with comparable or superior performance to that of ordinary Portland cement, provided that proper limestone quality is selected with optimum content and the optimum levels of fineness of both limestone and clinker are used. However, further research is needed to determine long-term performance, especially in marine and hot environments.

Some Engineering Properties of Limestone Concrete

Abstract In order to reduce energy consumption and CO2 emission and increase production, cement manufacturers are blending or intergrinding mineral additives such as slag, natural pozzolans, sand, and limestone. The reduced cost of limestone is mainly due to energy savings by substitution of a portion of the calcined clinker with a small amount of limestone and to the presence of limestone deposits near cement kilns, and hence, reduced transportation costs. This paper reports on a preliminary study underway on the performance of limestone cement mortar and concrete. The effect of different levels of limestone cement replacement (0% to 35%) on physical and mechanical properties of cement mortar is reported, as well as the effect of fineness of both clinker and limestone. From the test results, it was found that it is possible to manufacture cement with limestone addition with comparable or superior performance to that of ordinary Portland cement, provided that proper limestone quality is selected with optimum content and the optimum levels of fineness of both limestone and clinker are used. However, further research is needed to determine long-term performance, especially in marine and hot environments.

Mechanical behaviour of Portland cement mortars with incorporation of Al-containing salt slags

Recovery of a salt cake slag produced from aluminum scrap re-melted in rotary furnaces, at the lowest cost, while complying with all environmental laws is the main objective of this study.The characterisation of the slag residue involved determinations of the water leaching conditions, toxicological analysis, chemical analysis of the leaching waste, and mineralogical composition. A two-phase study was made to determine the effect of waste additions on mechanical properties of cement mortars, involving partial replacements of either sand or cement. SEM characterisation of fracture surfaces was also made. Partial substitution of cement, which is the most expensive component of the mortar, by salt slag has both environmental and economical advantages. However, only small amounts (up to 10 wt.%) can be replaced by washed slag without significant damage to mortar characteristics. Sand substitution by slag is less problematic and 30–50 wt.% replacement levels are easily achieved. However, the direct economical impact is less relevant. The incorporation of unwashed slag in impracticable, as a result of noxious gases released and significant volumetric expansion effects.

Microscopic and laser granulometric analyses of hydrating cement suspensions

The results from microscopic and laser granulometric analyses of hydrating cement suspensions, containing active mineral additives (silica fume, fly ash, and a mixture of both called Pozzolit) are presented. Conclusions are drawn about the specific hydration processes of the cements investigated, as well as the applicability of the laser granulometry method for the study of cement and its hydration products. The investigation is part of a program studying the combined effect of silica fume and fly ash on the hydration process and the physical and mechanical properties of cement mortars and concretes.

Effect of the “Pozzolit” active mineral admixture on the properties of cement mortars and concretes part 1: Physical and mechanical properties

The results from investigations on the physical and mechanical properties of cement mortars and concretes containing the active mineral Pozzolit admixture are presented in this paper. The basic components of this admixture are silica fume (SF) and low calcium content fly ash (FA). The compressive and flexural strength and modulus of elasticity of cement mortars and concretes containing Pozzolit have been determined as well as the water- and gas permeability. The results have been compared with corresponding parameters of cement mortars and concretes without mineral admixture or with only one component — either silica fume or fly ash. It has been established that the Pozzolit active mineral admixture contributes not only to overcome the technological difficulties encountered in the process of silica fume delivery in cement mortars and concretes but also to improve cement stone strength and resistance.

Air-cured woodpulp, fibre/cement mortars

The mechanical properties of cement mortars reinforced with kraft wood-pulp fibres have been studied. The composites were air-cured for up to 450 days. Although the fibre mortars have lower flexural strength values than either autoclaved fibre mortars or air-cured fibre cements, they do have improved values of fracture toughness of approximately 3kJ m −2 at fibre loadings of 8% fibre by mass. This would suggest there may be a use for such products in areas where the materials are subjected to impact, eg, renders on walls or products which are handled frequently such as outdoor gardenware.

Porosity and mechanical properties of cement mortar

The effect of volume fraction porosity on the mechanical properties of cement mortar is studied. It is shown that both the Young's modulus and fracture toughness decrease with porosity. Although the flexural strength also decreases with porosity the linear relationship is largely fortuitous. Maximum size pores do not act as critical flaws in controlling flexural strength. The critical crack size is several times larger than the maximum pore size due to stable crack growth according to the crack growth resistance curve concept applied to cement mortar.

Mechanical properties of cement mortar with randomly oriented short steel wires : Pakotiprapha, B. Magazine of Concrete Research, Vol 26, No 86 (March 1974) p 3

Mechanical properties of cement mortar with randomly oriented short steel wires : Pakotiprapha, B. Magazine of Concrete Research, Vol 26, No 86 (March 1974) p 3

Discussion: Mechanical properties of cement mortar with randomly oriented short steel wires

Discussion: Mechanical properties of cement mortar with randomly oriented short steel wires

Mechanical properties of cement mortar with randomly oriented short steel wires

Synopsis This paper deals with an analytical and experimental investigation of the mechanical properties of cement mortar reinforced with randomly oriented short steel wires. Analytically, the material is treated as a composite and its properties are derived by the laws of mixture. The effect of random orientation of the short wires is taken into consideration by the introduction of dimensionless factors which are derived on the assumption that the geometric centres of the wires are uniformly distributed in space and that any wire has an equal probability of being oriented at any angle to the direction of the applied stress. Explicit expressions are given for the moduli of elasticity and the ultimate strengths in tension and compression. In bending and torsion, the composite is idealized as a bi-linear material to describe its behaviour in the uncracked and in the cracked range provided that the volume fraction and the length of wires used exceed certain values which are suggested. Experiments were conducted and the results obtained are shown to be in good agreement with theoretically predicted values.