Microstructural study of Styrene Polyacrylic (SPA) latex modified mortars

In this paper, the influence of the styrene polyacrylic (SPA) latex polymer on the microstructural properties of limestone mortars has been studied. For this purpose, five mortars were developed with different dosages of the SPA latex (0%, 2.5%, 5%, 7.5% and 10%) by weight of cement. This research was carried out using XRD, FTIR, and SEM analyses. The results of XRD and FTIR studies showed that the addition of SPA latex can increase the portlandite content of polymer-modified mortars (PMMs), compared to the control mortar. In addition, the moist environment promotes the Ca(OH)2 consumption in PMMs at early age and accelerates the hydration. Moreover, the SEM analysis revealed that the cement hydrate structure of the reference mortar is loose. In contrast, the hydrates of the PMMs were covered by a polymer film or membrane, and the pore structure is significantly affected by the filling effect the micropores by the latex particles

Microstructural study of Styrene Polyacrylic (SPA) latex modified mortars

In this paper, the influence of the styrene polyacrylic (SPA) latex polymer on the microstructural properties of limestone mortars has been studied. For this purpose, five mortars were developed with different dosages of the SPA latex (0%, 2.5%, 5%, 7.5% and 10%) by weight of cement. This research was carried out using XRD, FTIR, and SEM analyses. The results of XRD and FTIR studies showed that the addition of SPA latex can increase the portlandite content of polymer-modified mortars (PMMs), compared to the control mortar. In addition, the moist environment promotes the Ca(OH)2 consumption in PMMs at early age and accelerates the hydration. Moreover, the SEM analysis revealed that the cement hydrate structure of the reference mortar is loose. In contrast, the hydrates of the PMMs were covered by a polymer film or membrane, and the pore structure is significantly affected by the filling effect the micropores by the latex particles

Mixture design approach to evaluate fresh properties of SCC made with various sands

The aim of the present paper is to provide a mixture design modelling to evaluate the effect of different sand types on fresh properties of self-compacting concrete (SCC). A statistical approach was used to highlight the effect of river sand (RS), crushed sand (CS) and dune sand (DS) as proportions in binary and ternary systems in SCC composition. The responses of the derived statistical models are sand packing density (SPD), T500 and J-ring. The resulting mathematical models are used to illustrate the variation of different responses in ternary contours plots with respect to the proportions of RS, CS and DS. This offers flexibility to optimize RS, CS and DS blends with tailor-made of a given property that suit a particular recommendations. Results indicate that SPD of RS can be enhanced by a 40% of CS and 30% of DS proportions. Moreover, it is shown that flowability, measured by J-ring, can be improved by the increase of CS and DS in RS-CS and RS-DS binary systems. Results also indicate that passing ability measured with T500 decreased with the increase of CS proportion and increased with the increase of DS proportion in binary and ternary systems

Mix proportioning and performance of a crushed limestone sand-concrete

Satisfying the ever-growing demand of concrete aggregates poses a problem in many parts of the world due to shortage of natural sand. Moreover, to conserve natural resources and protect civil engineering infrastructures, there is a need to find alternative materials. Crushed stone sand has been identified as a potential substitute material for natural sand in making good quality concrete. The main objective of the present investigation is to determine an adequate mix design method and evaluate engineering properties of crushed limestone sand concrete mixtures in both the fresh and hardened sates. More than thirty concrete mixtures were examined. The results indicate that water demand and cement paste content in crushed sand concrete are generally higher than that used in similar conventional concrete. Good mechanical properties were obtained for concrete using crushed limestone sand as fine aggregates with a superplasticizer. However, a higher than normally used dosage of superplasticizer is required in these concrete mixtures and the optimum dosage of the superplasticizer needs to be determined for each cement and sand content

Effect of Mineral Additions and Metal Fibers on the Resistance of Cracking of the Dune Sand Concretes

International audienceThis article presents the results of tests on the behavior to cracking of concrete made with dune sand compositions containing mineral additions namely silica fume, limestone fillers and metal fibers (0%, 1% and 2%) and studies the influence of water/cement ratio (W/C). Research has shown that the age of cracking and the cracking stress of the selected specimens vary with the rate of mineral additions and fiber content. It has been noticed that the mixture with a water ratio = 0.40 shows an age of cracking shorter than the mixture with a higher ratio (W/C = 0.53) and that the age and the constraint of cracking of dune sand concrete vary with the rate of the mineral additions and fiber content. Indeed, the silica fume and the limestone filler significantly increase the age of the concrete cracking. It is found that the addition of metal fibers slightly reduces shrinkage on the other hand there is very little difference between the different dosages in fiber. In the long term, the action of the fibers is clearer because the reinforced fiber matrices are stabilized more quickly than the control matrices without fibers. The outbreak of the restrained shrinkage cracking is delayed and it appears in form of a network of cracks shorter, not very open and therefore less damaging for the new composite

Physico-mechanical characterization of composite cementitious mortars modified by resin containing antifoam

Nowadays, polymer-modified mortars (PMM) are generally used in the field of building as finishing materials. In general, The properties of the fresh and hardened PMC are affected by several factors that tend to interact each other: the nature of materials used as latex, cement and aggregates; the mix proportions (W/C, polymer/cement ratio, etc.); air content; type and amount of surfactants and anti-foaming; and curing methods. This present experimental work aims to study the influence of the rate of partial substitution of cement by resin containing anti-foaming on the properties of composite mortars in the fresh and hardened state particularly workability, tensile and compressive strengths at different times (3, 7 and 28 days) and module of static elasticity at 28 days. For that purpose, seven mortar combinations were developed from the various substitution percentages (0 to 15% by step of 2.5%). The treatment of the obtained results reveals that this partial replacement of the cement by resin improves, clearly, the workability of mortars and decreases the report W/C at the same time. Besides, the incorporation of resin affects significantly the mechanical strengths, and consequently, the addition by substitution of the polymer-latex improves, slightly, the mechanical behavior in tensile where the rates of increase range from 2.20% to 8.54% for replacement percentages of 2.5% and 15%, respectively. Furthermore, the compressive strengths of cement - resin composite mortars are lower compared to the reference mortar made with the cement Portland (CEM I). The notable decrease in compressive strength of polymer–modified mortars can be justified by the reduction of cementitious part, in hybrid materials, which is an indispensable and responsible part of improving compressive strength