Ground Granulated Blast furnace slag (the GGBFS) is known as a potential by-product that can be used as a source of alumina-silicate in production of the geopolymers. The GGBFS based geopolymers possess disadvantages such as high shrinkage, low workability and short setting time. It has been proven that these defects can be reduced by partial replacement of the GGBFS by the other low calcium alumina-silicate materials. The bamboo leaf ash (BLA), which contains high content of SiO2 and low content of CaO, can be one of these materials. In this article, the effects of bamboo leaf ash on fresh, microstructural and mechanical properties of the GGBFS and the GGBFS/natural zeolite powder based geopolymer pastes have been investigated. Moreover, effect of the NaOH solution concentration( i.e. 8, 12 and 16 mole/liter) and the Al/Bi ratio (i.e. 0.5, 0.6 and 0.7) on properties of the geopolymer pastes have been evaluated. The results show that replacing 10% wt. of the base materials by the BLA in the studied geopolymer pastes leads to an increase in the workability and setting time. While, this substitution results a reduction in the amount of crystalline phases produced and consequently a decrease in the mechanical characteristics. Based on the results, as the NaOH solution concentration increases from 8 to 16 mole/liter, the workability, setting time and mechanical characteristics of the GGBFS/BLA based geopolymer paste have been reduced. Moreover,

One of the factors of damage and destruction of concrete structures is fire. Concrete structures, in addition to having the proper mechanical characteristics, they must have durability properties to use their capacity over their lifetime. In this study, the effect of various volume fraction of steel fibers on improving the mechanical and durability properties of concrete at various temperatures has been investigated. Mechanical properties including compressive and tensile strength of concrete in the hot condition and the durability characteristics of the concrete after cooling, including surface water absorption, the penetration depth of water, electrical resistance and weight loss have been investigated. This study covers 0.25 and 0.50% volume fraction of steel fibers and temperatures of 28 to 800 ° C. The results show that the increase in compressive strength and tensile strength due to the age of the samples was higher in fiber concrete than non-fibrous concrete. It was also observed that the addition of 0.25 and 0.5% of steel fibers at the tested temperatures improved the compressive and tensile strength in the range of 10 to 27% and 8 to 200%, respectively. In addition, application of these fibers has reduced the sorptivity coefficient, the penetration depth of water, the electrical resistance of concrete and the weight loss of concrete owing to the high temperature. The results of this study showed that, at temperatures below 500 °C specimens containing 0.25% of steel fiber and 500 °C onwards, specimens containing 0.50% of steel fiber had the best performance on the improvement of the mechanical and durability properties of normal concrete at high temperatures.

In this experimental study the effects of two types of polymers including ethylene vinyl acetate and styrene acrylic on the properties of cement mixtures have been investigated. Polymer contents of the mixtures were 5, 10, 15 and 20% by weight of cement and the ratio of water to cement was 0.33. In order to investigate and evaluate the effect of polymer materials on the properties mixtures, the compressive, flexural and tensile strengths, impact resistance, shrinkage, rapid chloride migration coefficient and the capillary water absorption contents were investigated. The specimens were cured under wet conditions at early ages (7 days) and dry periods at later ages (After 7 days). The results indicate an improvement in several mechanical characteristics such as flexural strength, tensile strength, impact resistance and a significant influence on reducing the permeability of cement mixtures in the rapid chloride migration and water absorption tests by use of polymers.

In this research the effects of three types of commercial polymers including Styrene-butadiene-rubber, Ethylene- vinyl acetate and Styrene-acrylic on the properties of cement mixtures have been investigated. Polymer contents in the test mortar mixtures were 5, 10, 15 and 20% by weight of cement and the water-cement ratio was kept constant at 0.33. In order to investigate and compare the influences of polymer materials on the mortar specifications the mechanical properties including compressive strength, flexural toughness and durability properties including rapid chloride migration coefficient and the amount of capillary and volumetric absorption, resistance to sulfuric acid were evaluated. The specimens were cured under wet conditions at early ages (7 days) and air cured at later ages (After 7 days until the test). The results indicate an improvement in several mechanical characteristics such as flexural toughness and significant influence on reducing the adsorption rates of cement mixtures in the rapid chloride migration coefficient, water absorption and resistance to sulfuric acid. Comparing the results at different ages showed that dry curing period has had a significant effect on the strength growth process and mechanical properties of polymer modified mortars. According to the results of mechanical tests, the Styrene-acrylic and Ethylene-vinyl acetate provided significant improvements in the flexural toughness and this improvement was enhanced by increasing the polymer-cement ratio. Concerning the penetration and adsorption of water in the mortars by same polymer-cement ratio, Styrene-acrylic modified mortars have obtained higher enhancements than other compounds. Also, in the ratio of 15% polymer to cement, the lowest amount of water absorption and penetration was observed in the Styrene- acrylic modified mortars which showed the optimal ratio. According to the results of the sulfuric acid test, the best practice was for the Ethylene-vinyl acetate modified mortars. The results of this study indicate that modified polymeric cementitious base mixtures can be widely used in construction industry applications.

It is well known that general concrete alone lacks excellent mechanical properties especially in tension, hence there is need for modification by polymers. Research on polymer concrete began in the 1950s and it has been actively used since the 1970s. The use of Polymer cement concrete is in rapid increase as it possesses improved qualities over conventional concrete. Adequate design of polymer concrete members requires appropriate understanding of its mechanical behavior.There are three kind of polymer concrete: A) polymer concrete (PC): this kind of polymer concrete is formed by polymerization a mixture of a monomer of a thermoset polymer and aggregate, B) latex-modified concrete (LMC): this kind of polymer concrete is named polymer Portland cement concrete. In this way Conventional concrete is replaced with part of mixing water with latex and C) polymer-impregnated concrete (PIC): it is produced by impregnating or infiltrating a hardened concrete with a monomer then polymerization is done.
There are many polymers that used in polymer concrete same as polyester, epoxy, styrene monomer and methyl methacrylate (MMA). Polyester concretes are viscoelastic and will fail under a sustained compressive loading at stress levels greater than 50 percent of the ultimate strength. Sustained loadings at a stress level of 25 percent did not reduce ultimate strength capacity for a loading period of 1000 hr.
The main purpose of this paper is to investigate the effect of post curing effects on the mechanical properties of polymer cement concrete. Polyester was introduced to the mix as cement replacement by weight. A suitable concrete mix was designed and produced, using three different ratios of Polyester as cement replacement varying between conventional concrete for 0% Polyester to 30% Polyester. Two types of samples were cast, compacted and then cured for 28 days. The polymer concrete samples include two types, one has post cured and the other was without post curing. The cylinder specimens were tested in compression and split tension to determine the compressive and the tensile strength. The variation of compressive strength, tensile strength were determined and assessed for samples especially for samples with and without post curing. Based on the experimental program post curing has Significant effects compressive and tensile strength of concrete samples. The effect of weight percentage of polyester resin and post curing condition were investigated in relation to the mechanical properties of polymer concrete. The results indicate that an increase of polyester content in polymer concrete enhances the mechanical properties same as the tensile and compressive strength of the composite. Also, post curing increases mechanical properties, especially in the lower weight percent polyester. It seems that post curing causes increased degree of cross-linking in resin and increased the effect of polyester in the composite in lower percentage. It can be seen that post curing increased the mechanical strength for lower weight percentage of polyester more than the higher ones. In other words, lower weight percentage of polyester is more effective than the higher. This result comes from the effect of cross-linked density of polyester in polymer concrete composite because cross-linked density is very low when the weight percentage of polyester is low. Post curing can increase the cross-link density of polyester therefore increasing the mechanical properties of polymer concrete.

Employing different waste materials in roller compacted concrete (RCC) mixtures has fascinated investigators recently. The main interception of utilizing wastes in concrete is its engineering properties loss. As a result, using additives has been suggested to modify mechanical properties of mixes efficiently and economically. In present research, waste crumb rubber has been used for fabricating specimens and the influence of nano-silica and fly ash incorporation was assessed. Design of experiments was programed using Taguchi method and mix design was optimized accordingly. A 40 % to 70% fly ash content (by the weight of cement and replacement), 0 to 30% crumb rubber content (by the weight of fine aggregates and replacement) and 0 to 3% nano-silica content (by the weight of cement and replacement) were incorporated in the RCC mixtures. Moreover, L16 orthogonal array with a mixed-level design and signal-to-noise (S/N) of larger is the better was used for design of experiments. The Taguchi method is a proper way for mix optimization and determining precise percent of components in mix design. The main objective is RCC strength optimization based on RCC structural limitations. It is noteworthy that crumb rubber incorporation in concrete precedes mechanical loss of mixture. To gain proper mix design with great engineering properties and to obscure mechanical loss nano-silica powder was employed in mix combinations. The final results of compressive, flexural and splitting strength of mixtures tested after 28 days curing in laboratory were maximized with Taguchi method. Finally, the results reviled that the mix with 27% crumb rubber (by mix volume), 50% fly ash (by weight of cement) and 2% nano-silica (by weight of cement) incorporations, should be considered as optimal mix.

This study focuses on determining the engineering characteristics of asphalt concrete using fillers with different physical and chemical interactions properties. Mineral and Portland cement as the common fillers and nano clay and precipitated calcium carbonate (PCC) as the novel fillers. Mechanical properties that were investigated are marshall stability, flow, indirect tensile strength, resilient modulus, dynamic creep and indirect tensile fatigue. More than 200 sample were be made in size of Marshall Sample with different filler/asphalt ratio. The results show that fillers properties such as surface area have the most effect on mechanical properties of aspartic mixtures. By increasing in filler content penetration and ductility reduce and softening point increase. Silica filler have more strength under static loading but strength under cyclic loading reduces. Nano clay can improve creep behavior but fatigue life reduces. PCC have the most effect to increase fatigue life.

Around 25 billion tons of concrete is used each year globally that means over 3.8 tons per person in the world each year. Occupying about 60% to 70% of the volume, aggregate is a main ingredient of concrete. Nowadays, there is an increasing trend toward using sustainable concrete and reusing of aggregates from demolished concrete is one way to achieve this aim. Although using recycled concrete aggregate (RCA) does not lead to significant reduction of CO2 emission, but it reduces using natural resources (natural aggregate) as well as helping to reduce dumping construction and demolition wastes in landfills. More than 900 million tons of construction and demolition waste is produced each year only in Europe, the U.S., and Japan. A comprehensive literature review on mechanical properties of recycled aggregate concrete (RAC) including compressive strength, splitting tensile strength, modulus of elasticity and modulus of rupture is presented. In addition, databases are created for mechanical properties of RAC in order to lead to changes or acceptance in design codes and standards’ provisions. These data were compared with the American, European, Australian, Japanese, Canadian standards provisions. Results of this study show that existing code provisions are not always conservative for mechanical properties of RAC.

High-Performance Fiber Reinforced Cement Composites (HPFRCC), are mortars exhibit strain hardening behavior in the tensile test also have features such as flexibility, Durability, and high energy absorption capacity. In this paper, the effect of the fiber on the characteristics of the HPFRCC mechanical properties, the Fracture pattern and the energy absorption capacity have been investigated. Since there is no specific standard test available for HPFRCC, first, 18 mixing designs with different material proportions were made, the mixing that was the most economical and has the most appropriate mechanical properties has been selected. Finally, the selected mixing was evaluated with 60 specimens in three states of non-fibers, one and two percent fibers at different ages. The results indicate that with increasing age of specimens in all three conditions, the tensile and compressive strength increased, also the pattern fracture of the specimens has been improved by adding the fibers has moved from the deep cracks and the fragmentation of the specimens to the surface cracks .Also energy absorption capacity increased by 1 and 2 percent fiber, 24 and 52 percent, respectively. Then the relations for determining the compressive strength at different ages and the calculation of tensile strength with compressive strength for plain concrete presented in the standard were also evaluated for HPFRCCs.

This study aims at improving the tensile behavior of concrete blocks by adding polypropylene fibers to the concrete mixture. For this purpose, 84 cylindrical and cubic specimens were constructed and tested under tensile splitting and compressive force. Three variables of fiber dosage, cement content, and fiber type were taken into account to study the sensitivity of splitting strength, strain capacity, compressive strength, and energy absorption to these variables. The results show that the specimens without fibers experienced a sudden non-ductile failure, whereas this is not the case for the specimens with added fibers. All the considered response parameters were improved thanks to the addition of fibers. Generally, the improvement of specimens with micro fibers was better than that of the corresponding specimens with macro fibers, especially when larger cement content was included.