Investigating the effect of slag iron oxide slag, microsiliea, nanosilica and polymer fibers on mechanical properties of concrete pavements

In this study, using absolute volume mix design, the total amount of cement materials was 360 kg/m3 and the ratio of water to cement was 42% of the test mixture. In these mixtures, new technologies in the field of concrete materials are used. The two powdery materials of slag and slag iron furnace and silica as a substitute for cement in order to reduce the consumption of cement and its contaminations have been investigated in terms of mechanical properties. In next step, two materials of nano-silica and nano-titanium oxide as a new generation of nanotechnology pavements in terms of mechanical properties have been investigated. At the last stage, polypropylene fibers have been used as an advanced technology for increasing the tensile and wear properties of concrete. Mixing designs with sufficient dough volume whose efficiency is based on the slip test in the range of 5 to 7 centimeters has been selected. In the next step, the mixes with substitute cementitious material of Isfahan iron smelting slab and synthetic pozzolan silica, nano silica, nano-titanium and polymer fibers have mechanical properties such as compressive strength, flexural strength, tensile strength (Brazilian) and abrasion resistance in comparison with the concrete was analyzed. The results indicate that the use of alternative materials for powdered and nanoclay cements not only does not show a negative effect on mechanical properties reduction compared to the control concrete, but also the good performance of these materials ,makes concrete with higher mechanical properties and longer lifetime than control concrete polymer fibers have also a good performance in all mechanical properties , but due to the effect of these materials on the properties of new concrete and it`s rigorous implementation in the projects, it is necessary to determine a comprehensive implementation method for their use, which requires the attention of all authorities.

reached, the sample is split into half to the middle. Bending strength is the maximum tensile stress due to bending in concrete. The loading causes bending and, as a result, creates tensile stresses in the concrete.

Laboratory Program 2.1. Specifications of consumable materials 2.1.1. Cement
The cement used in designs is type 2 of Delijan Cement Factory. The results of various experiments, such as compressive strength of cement mortar at different ages and other specifications, are presented in table 1 and 2.

Silica Soot
The high reaction rate of silica soot leads to an increase in the initial released heat in concrete. Application of silica soot in concrete has a high degree of operational sensitivity and especially its homogeneous distribution in concrete and proper treatment of concrete in early ages is absolutely necessary. It is necessary to explain that in this research silicate soot from Azna, Lorestan has been used. The used chemical analysis of the silica soot is presented in table 3. Table 3. specification od cement supplements

iron furnace slag
The iron oxide slag used in this research is from Isfahan Steel Zone 111. The main feature of this line is the rapid cooling of the iron slag by water jet. This instant cooling will help to activate and reactivate the iron oxide slag. In order to perform better and increase the particle size, the iron oxide slag used in this study is more than the usual cement mill and its softness has reached 4500 cm/g. in table 3, the density and chemistry analysis are performed in this method on this iron oxide slag.

nano silica gel
The shortage of aggregates and nonexistence of fines or fillers (which are usually not repairable due to workshop limitation) will inevitably lead us to consume more cement. Efficiency, which ultimately increases the permeability of concrete. The additive of nano-silica gel, the main component of which is its microcrystalline material, is added to the concrete to enhance its properties during construction. This material, which adds about 6 to 9 percent of the weight of the cement to the concrete, in addition to the possibility of a reduction of about 15 to 20 percent of the water to cement ratio, increases the efficiency or slump of the concrete and improves the concrete density and helps to prevent air congestion in concrete. The amount of permeability and the percentage of water absorption of concrete is greatly reduced, which according to the workshop conditions and the concrete mixing plan, increases the compressive strength of the concrete.

titanium Nitric oxide
One of the nanoscale particles that enhance the properties of concrete is titanium dioxide, which is used in painting and window glasses, because of its sterilizing properties and strong catalytic reactivity in cement. The beneficial effects of the use of nano-particles are based on the psychological increase of the concrete paste prior to the time of grabbing, which causes the aggregate suspension to improve and the concrete availability increases. In this study, the mechanical properties of concrete pavement containing titanium dioxide as an additive substance in the nanoscale area have been investigated. In figure 1, a microscopic image of titanium dioxide is presented for better understanding.

polypropylene fibers
Polypropylene fibers typically with different lengths for concrete and cement mortar application, with 6 mm long for gypsum and thin mortar and with a cut of about 3 mm for the automotive battery industry and 12 and 18 cuts for armed concrete construction is used. In this study, studying the literature on the use of fibers in pavement concrete, the fiber replacement rate in the design of the control mixture is 15% vol. in figure 2, polypropylene fibers are shown for a better recognition.

Sand
In this research, three type of stone materials such as almond sand, grape peas and sand are used. Selection of suitable material for self-compacting concrete was performed by carrying out numerous experiments on various types of materials and finally, mineral stone materials in river-type in a mine in Shahriyar with a suitable quality were selected. The sand used in these mixtures is of a natural type and 0-6 mm in size. The specific weight of this sand is 256 and the water absorption is 3/3 percent. The sandy softness modulus is 3/5, which is suitable for the production of concrete according to ATSM C 33[7] standard. Figure 1 show the grain gradient graph.   In this research, a mixed design is considered as a control mixture, and then the changes to the new technologies for pavement concrete productions have been applied in this mixed design. At first, two powder materials were replaced by the optional substitution percentage from previous studies on these materials in the control mixture design. Slag of fusion furnace, 30% and micro silicon, have been replaced by 10% cement mixed cement. In the next step, by studying the previous studies, the amount of nano-silica gel replacement 4%, titanium dioxide 5% and polypropylene fiber 0.15% cement material were considered. Replacement in all mixture designs based on the total amount of cement materials was 360 . in order to achieve equivalent efficiencies in 5-7 cm of slipper, a polycarboxylate ether-based extruder has been used.

slump test
In this study, to investigate the effect of new technologies on the mechanical properties of concrete in a single surface. Polycarboxylate based super-lubricating materials have been used to produce slumps of 50-70 mm in less effective concretes.

2.2.
Concrete compressive strength test The test for determining the compressive strength on 10*10 cm specimens was carried out according to Iran`s standard no-1608. Samples were stored in lab environment after 24 hours of molding and then kept in water and lime saturated for 28 days. On 28 th day, the specimens were extracted from the treatment pond and the compressive strength of the concrete was calculated using a concrete breaker jack in figure 5

concrete flexural strength Test
The bending strength test was performed on beams with dimensions of 15*15*60 cm in accordance with Iran`s standard number 490 on day 28. The samples of the beam were stored in saturated lime for 28 days after the molding and then the test of the beam defeat was performed using the bending compartment shown in figure 6. The results of the flexural strength test of concrete pavements containing various additives are presented in table 4.

tensile strength testing of concrete
This test is used to determined the tensile strength of an unidirectional concrete sample, known as Brazilian test. the test was performed on cylindrical specimens of 15*30on day 28. In figure 19,

Results Analysis 3.1. compressive strength
The compressive strength diagram of the proposed mixtures design is presented in the figure below. According to this chart, concrete containing nano-silica and micro-silica have a higher resistance. Concrete containing micro-silica has high resistance to a very small numerical difference. It is noteworthy that the use of slag not only has no negative effect on the process of obtaining resistance to the control concrete, but also showed an increase. The result can be a good alternative to cement as an environmentally friendly product.

bending strength
The Figure below shows the results of bending strength. The most flexural strength has been obtained from concrete containing fibers and the lowest for concrete specimens. Another physical effect of micro silicon is also the placement of particles near the aggregate and cement pulp, which shows that the tensile strength of the bending concrete is very high.

tensile strength of concrete
The Test results are presented in the figure below. In general, the tensile strength of concrete in a two-tiered manner is greater than the tensile strength and is smaller than the tensile strength in bending state. Similar to the results of flexural beam bending, concrete containing fiber has the highest tensile strength of duality. Micro silicon replacement concrete has shown increased tensile strength relative to the control concrete. Other cement materials, such as slag, have not only reduced the tensile strength due to proper bonding in aggregates and concrete dough, but also increased resistance in the case of slag powder.

. Abrasion Resistance of Concrete
In this study, due to the concentration on concrete pavements, ASTMC779 test has been selected using a rotary disk. This method adapts with concrete pavement performance better. To do this, the rotary disk device is used according to the standard. In this test, the index is expressed as the wear depth in millimeters. Increasing the use of nanoscale materials will reduce the distance between particles in the nano range and reduce and decrease the ratio of crystal to the C-S-H gel and the concrete microstructures will be loose. The abrasion resistance of concrete is improved in the presence of polypropylene fibers, which has the greatest effect on hair cracks. Concrete containing micro silica and slag also have good performance in increasing the abrasion resistance of concrete in the presence of good impregnation effect in concrete create a good density for pavement concrete.