Pore Structure Of Cement Mortars Research Articles

Effect of sand content on strength and pore structure of cement mortar

The effects of four sand contents on the compressive, flexural and splitting-tensile strength of cement mortars were evaluated. Moreover, we experimentally investigated the pore structure of cement mortar brought about by changing the sand content and water/cement ratio. The changes in the pore structure were quantified by measuring the porosity and pore size distribution obtained by using mercury intrusion porosimetry (MIP) technique. The test results show that the strengths of cement mortar increase with increasing sand content. It is also suggested that the traditional water/cement ratio law can be applied to cement mortar with different sand contents, provided that a slight modification is introduced. Sand content is an important parameter influencing the pore structure of cement mortar. Moreover, there is a good relationship between the pore structure and strength of cement mortar.

Effect of Nano-Alumina on Pore Structure and Durability of Class F Fly Ash Self-Compacting Mortar

In this study the effect of pore structure on the mechanical properties and durability characteristics of Self-Compacting Mortars (SCM) containing nano-Al2O3 (NA) and class F fly ash are investigated. Al2O3 nanoparticles with the maximum size of 15 nm in three different proportions of 1, 3 and 5% of the binder content were utilized to partially replace the cement. The 25% of the cement weight was also replaced by class F fly ash. The pore structure of cement mortars was determined through the Mercury Intrusion Porosimetry (MIP) and Gas Adsorption (BET) methods. The microstructure of the SCMs was evaluated by Scanning Electron Microscopy (SEM). The results indicated a reasonable correlation which was observed between the pore structure and other properties of mortars. The addition of the NA at proportions over 1% led to an increase in the pore volume of specimens by virtue of agglomeration. In overall, it seems that 1% NA can be considered as a suitable replacement regarding the pore structure and hardened properties.

Effect of Pozzolanic Additive on Pore Structure of Cement Mortar

In this paper are explored the changes of pore structures of mortar with pozzolanic admixture exposed to aggressive environments, namely 5% wt. sodium sulphate solution. Influence of non-flowing sulphate solution on the test specimens were determined in dependence on the different type of cement and used minced clay brick as pozzolanic admixture. Attention is also paid to the properties of the individual components of the mortar. From the results obtained follows that the additive of minced clay bricks has positive impact on the sulphate resistance.

Influence of pore structure on compressive strength of cement mortar.

This paper describes an experimental investigation into the pore structure of cement mortar using mercury porosimeter. Ordinary Portland cement, manufactured sand, and natural sand were used. The porosity of the manufactured sand mortar is higher than that of natural sand at the same mix proportion; on the contrary, the probable pore size and threshold radius of manufactured sand mortar are finer. Besides, the probable pore size and threshold radius increased with increasing water to cement ratio and sand to cement ratio. In addition, the existing models of pore size distribution of cement-based materials have been reviewed and compared with test results in this paper. Finally, the extended Bhattacharjee model was built to examine the relationship between compressive strength and pore structure.

Influence of water-to-cement ratio and curing period on pore structure of cement mortar

The effect of water-to-cement ratio (w/c) and age on the pore structure of cement mortar was determined through mercury intrusion porosimetry (MIP). The cement mortar specimens were prepared with w/c of 0.4, 0.5 and 0.6, and were tested at different curing ages (14, 28, 180days). The degree of hydration of the cement in cement mortar was obtained by determining the non-evaporable water content. Test results have shown that, the degree of hydration increased with increasing curing time and water-to-cement ratio of the cement mortar for the ages of cement mortar varying between 14 and 180days. An increase in the water-to-cement ratio increases the total porosity. In addition, the existing models of pore size distribution of cement-based materials has been reviewed and compared with test results in this investigation.

Effects of admixture type and dosage on microstructural and mechanical properties of cement mortars

Effects of admixture type and dosage have been investigated in the scope of this study. The influence of incorporation of chemical admixtures at different dosages on the development of pore structure of cement mortars has also been investigated. A delay on the development rate of strength by incorporation of chemical admixtures at early ages has been determined. The highest strength values were obtained for the cement mortars prepared by naphthalene sulphonate based chemical admixture. The strength values of specimens prepared with overdosage were lower than those of control specimens. Therefore, setting time and flow values were investigated related to admixture dosage and type. Increase in dosage of admixtures results in an increase of setting time and flow values. The pore structure development was given by time and dosage. Maximum pore area ratio values are determined for cement mortars prepared with overdosage. Pore area ratio values decrease by time, as compressive strength values increase.

Physical and Chemical Influence of Polyacrylate Latex on Cement Mortars

In this research, the physical and chemical influence of polyacrylate (PA) latex on cement-based materials were studied using polymer modified mortars with polymer/cement (P/C) ratios of 0%, 5% and 10%. Physically, the mechanical performance of PA latex modified mortars was investigated with compression toughness energy and bending strength. Further more, a comparison of the pore structure and porosity between PA latex modified and unmodified mortars was conducted. The chemical reactions between PA polymer and cement hydrates were clarified with thermogravimetric (TG) analysis. It can be concluded from this research that PA polymer can refine the pore structure of cement mortars and link the cement hydration products together chemically. While, at the same time, PA latex addition can cause air entrainment which will weaken the physical behavior of cement mortars. So there is an optimum P/C ratio to achieve the best mechanical properties. And in this research, the optimum P/C ratio is 5%.

A comparison study of porosity and compressive strength mathematical models with image analysis

In this study, mathematical models obtained to determine the relationship between pore structure of cement mortars and compressive strength values were compared with results of image analysis results. Micrographs of polished sections of prepared cement mortars were taken to determine the area ratio values of pore structure in cement mortars. The relationships between pore structure and compressive strength values were investigated. Four different types of mathematical models for the relationship between porosity and compressive strength were examined. The obtained results for each mathematical model were compared to image analysis results. The study shows that image analysis techniques have a great capacity to define the relationship between pore area ratios obtained by microstructural investigations and compressive strength values. There is a good correlation between this relationship by image analysis and other mathematical models.

Determination d'un réseau aleatoire de pores pour modéliser la sorption et la migration d'humidité dans un mortier de ciment

The pore-structure of cement mortar is modelled by a cubic network of pores in order to simulate various static and dynamic phenomena concerning moisture, using elements of the theory of percolation. The pore diameter distribution is fitted in order to obtain a simulation of the hysteretic sorption in good agreement with experimental data. In the range of large diameters, the distribution is more accurately defined with the help of mercury intrusion data. The isothermal moisture migration in the structure previously determined is modelled, taking into account both vapour diffusion and viscous flow of liquid water, and assuming local equilibrium. Even at large liquid water content of the material, the vapour diffusion is found to be the dominant migration mechanism. The simulated coefficient of transfer is in very good agreement with the drying experimental data. The model is not as successful in the description of imbibition experiments. Some explanations are proposed.

Effect of heat treatment conditions on the pore structure of cement mortars

Effect of heat treatment conditions on the pore structure of cement mortars

Changes of pore structure of cement mortars due to temperature

Changes of pore structure of cement mortars caused by high temperatures (up to 900 °C) as well as by extremely low temperatures (down to − 170 °C) could be proved by means of mercury porosimetry. While high temperatures lead to an increase of the total volume of pores > 40 A ̊ low temperatures do not. But in both cases a coarsening of the pore structure occurs. The usefulnes of the test method for detecting structural defects caused by a temperature treatment was shown exemplarily by establishing an experimental relation between the pore volume and the residual strength after low temperature cycles.