Reactive POWDER concrete (RPC) is a type of ultra-high performance concrete (UHPC) with a high cementitious materials content. Coarse aggregates are removed in RPCs and ultra-fine POWDER materials such as silica sand, silica fume and pozzolans are used to provide a homogeneous concrete with excellent microstructure. In this study, the effect of LIMESTONE POWDER on mechanical properties of reactive POWDER concrete has been investigated. LIMESTONE POWDER was replaced with different percentages of silica sand, and compressive strength, flexural strength, shrinkage, and water absorption percentage of samples were measured at 7, 28, and 90 days of age. Experimental results showed that the 28-day compressive strength of this concrete was greater than 100 MPa and the physical and mechanical properties of the concrete were improved by increasing the amount of stone POWDER The mixture containing 54% replacement of LIMESTONE POWDER had the highest compressive strength and the lowest water absorption. Also, replacing silica sand with LIMESTONE POWDER increases shrinkage due to drying and reduces the Autogenous shrinkage of reactive POWDER concrete.

In this research LIMESTONE POWDER of stone processing factories as pore-forming material in brick was investigated. Brick samples were made with different proportions of brick making clay and LIMESTONE POWDER. Tests for determination of body density, drying and firing Shirinkages, water absorption, compressive strength and thermal conductivity were performed. After obtaining optimum percentage of additive, lightweight bricks and blocks using LIMESTONE were produced in pilot plant scale. In addition to mass decreasing due to CO2 removing, calcite prevents firing shirinkage and density increase. Compressive strength increased in relatively low percentages of calcite. Additive caused improvement of insulation properties.  

The structure must be able to maintain its stability and resistance in the event of a fire to protect human life. From time immemorial, concrete has been known to have fire-retardant properties. That's why the biggest concern with concrete structures at the time of the fire was the reinforcement and their non-flow. But with the development of concrete technology, the focus has also shifted to improving the mechanical properties of concrete to increase its fire resistance. The use of pozzolans and additives in concrete to achieve high-strength and durable concrete has been in the concrete industry for several years. In this study, the role of seashell and lumashell POWDER and their effects on the mechanical properties of concrete and achieving the optimal percentage of using shellfish POWDER to achieve high fire resistance and durability have been studied. For this purpose, laboratory tests involving slump evaluation, water absorption percent, and compressive strength under high temperature were conducted on samples in which the replacement ratios of Portland cement with the same weight of shell POWDER were 2. 5, 5, 10, 15 and 20% weight percent. Experimental results showed that seashell and lumashell POWDER POWDERPOWDERPOWDERPOWDER increase the hydration rate and consequently caused an increase in the heat of hydration which resulted in a faster loss of water in the concrete. Furthermore, Seashell and Lumashell POWDER absorbed more water than cement due to their finer particles. All these ultimately resulted in a reduction in concrete slump such that regardless to the shell POWDER type, adding 2. 5, 5 and 15% of shell POWDER, in average led to 13. 5, 27. 5 and 52% reduction in concrete slump respectively and it became approximately constant when the used shell POWDER was in excess of 15%. In addition, results showed that the presence of seashell and lumashell POWDER decrease water absorption in samples and made them more impenetrable. It happened because by filling the void in the cement paste with fine POWDER particles, the permeable cavities have been reduced and the connection paths of the cavities have been somewhat blocked. Replacement of cement with 2. 5%, 5% and 10% of Seashell and Lumashell POWDER led to (27%, 44%, 73%) and (7%, 59%, 73%) reduction in concrete water absorption values respectively and it became approximately constant when the used shell POWDER was in excess of 10%. The results of this study also showed that the replacement of cement with Seashell and Lumashell POWDER slightly increases the thermal resistance of concrete and the amount of replacement of 5% by weight of cement with shell POWDER is reported as the optimal percentage. Adding more than 5% shell POWDER as a substitute for cement, regardless of its type, is harmful and significantly reduces the thermal resistance of concrete. Also, the results of laboratory tests showed that when concrete is exposed to high temperatures, properties such as load-bearing capacity and durability are reduced, leading to cracking, loss of compressive strength and concrete divot. Finally, it can be concluded that the optimal percentage of using seashell and lumashell POWDER instead of Portland cement can lead to a suitable concrete in terms of respect for the environment.

The amount of adhesion between the concrete and the reinforcing bars plays a decisive role in the behavior of the RC structures, as well as their failure mode in the final extreme cases. This adhesion, known as band resistance, can be altered by changing the concrete mix. Laboratory evaluation of bond strength between rebar and concrete containing LIMESTONE POWDER is carried out in the present paper. For this purpose, 5, 15 and 30% of the cement of the control specimen (without LIMESTONE POWDER) is replaced with LIMESTONE POWDER and bond and compressive strength are obtained for specimens at the age of 7, 28 and 90 days. In this study, 15 cm concrete cubic and 16 mm diameter rebar is used to evaluate the bond. The water to binder ratio (w/b) is fixed at 0. 4. Also, the test of pulling out the rebar is applied to calculate the bond strength between the concrete and steel reinforcement. The overall results show that the bond strength decreases with the increasing percentage of LIMESTONE in concrete, the amount of this reduction is less than 10% for a sample with 5% LIMESTONE POWDER, while a reduction about 40% is obtained for a sample with 5% LIMESTONE POWDER. The assessment of the exciting models for prediction the bond strength indicates that these models estimate a bond strength larger than those given by the experimental results. Therefore, it is necessary to provide a suitable model for estimating the bond strength of concrete containing LIMESTONE POWDER.

The ternary system of Portland cement-microsilica-LIMESTONE has been studied by investigating its set and strength behaviors. A number of different cementitious systems comprised of 0, 10, 15, 20, 25, and 30% LIMESTONE POWDER and 0, 4, 6, 8, 10, 12, 14, and 16% microsilica were designed and prepared. The cementitious systems were then characterized by determining their relative workability and measuring their initial and final setting times and also their 7- and 28-day compressive strengths using paste specimens prepared at a constant W/C-ratio of 0.38. Total 77-dayshrinkage of the systems was also measured. The obtained results reveal that both 7- and 28-day compressive strengths increase with increasing microsilica up to 12% and decrease with increasing the percentage of LIMESTONE POWDER. A comparison of the results confirms the possibility of replacing Portland cement by a proportioned mixture of microsilica and LIMESTONE POWDER for enhancing the strength behavior or producing composite cements containing relatively high proportions of LIMESTONE POWDER with no loss in 7- and 28-day compressive strengths compared to plain cement.

One of the major obstacles to development of self-consolidating concrete (SCC) on the industrial scale and various applications is the high sensitivity or very low robustness of this concrete to conventional concrete. From this, in the present study, a total of eight SCC mixes have been produced and their rehology parameters were tested. A control mix (C) was the initial target and, seven series of mixes were developed with variations of each of the principal properties (i. e. filling and passing ability and segregation resistance) or using of AEA and VMA admixture. In order to evaluate the robustness of each mixture, in addition to the mixture with amount of water content, four mixtures were made that the water content of each mix was changed ± 3% and ± 6% relative to the base water content and then the rheological properties of each mixture were determined. The rheology parameters (yield stress, plastic viscosity) values were determined by a coaxial rhometer. This automated rheometer is a rate-controlled rheometer that was employed to carry out rheological measurements 10 minutes after the initial contact between water and cement. It consists of a four-bladed vane that is immersed into the concrete and rotated at various speeds while the torque acting on the vane is measured. the objective of using rheology measurements is to provide scientific parameters that are capable of describing multiple aspects of workability. This fact are true especially for self consolidating concrete that has several properties in fresh state. So, it is required to perform several tests to evaluation of these properties that in addition to increase the quality control time, it also raises the costs and reduces the accuracy. Therefore, it seems logical to determine rheological parameters that are an accurate test with high sensitivity Instead of measuring multiple properties of fresh state through different workability tests for achieving to a proper robustness index for SCC. Therefore a good approximation of the fundamental rheological quantities for cement based material can be obtained in terms of yield stress (τ 0) and plastic viscosity (μ ). In this study a rheograph is defined as a graph that X axis is yield stress (τ 0) and Y axis is plastic viscosity (μ ). This graph that to that has been named “ rheograph” is a convenient and essential tool to compare different concrete batches and examine the behavior relative to changed constituents, quantities of constituents, and/or relative to different times from water addition (and so forth). Thus rheograph is a systematical way to reveal the effects of slight decrease and increase in mixing water. The results of the study show that a slight increase in the amount of water increase the yeild stress of SCC, but decreasing water content in some concrete increase and in some concrete reduce the yeild stress. In contrast, in plastic viscosity of SCC, a slight decrease in the amount of water content increases the viscosity and a slight increase in the amount of water reduces the plastic viscosity of SCC. An appropriate index for estimating the robustness of SCC is the area enclosed between the rheological properties of concrete in changing the water content by ± 3% or ± 6%. According to this index, the addition of air entraining admixture to SCC improves robustness and reduces the amount of paste volume resulting in a severe reduction of robustness.

Sulfate attack is one of the most important problems concerning the durability of concrete structures. In this paper, the sulfate resistance of concrete and mortar specimens made from ordinary Portland cement containing LIMESTONE POWDER was studied. Strength reductions and mass changes of concrete specimens immersed in 10% Na2SO4 and MgSO4 solutions and Expansion of mortar prisms immersed in 5% and 10% Na2SO4 and MgSO4 solutions were monitored.It was observed that compressive strength decreases with the LIMESTONE replacement percent and also, deterioration is severer, the higher the concentration content sulfate.

Reactive POWDER Concrete (RPC) is a ultra-powerful concrete with superior physical and mechanical properties, which was registered in France in 1994. This concrete uses high cement factor, fine POWDERed materials, low water to cement ratio, and the use of superplasticizer with high compressive strength and very low permeability, high durability and abrasion resistance. the high amount of cement and microsilica used in this concrete not only increases the cost of production, but also increases the heat of hydration. On the other hand, cement production can have harmful effects on the environment. In the production of reactive POWDER concrete, fine-grained POWDER materials such as silica sand, microsilica, and quartz POWDER are used as materials. This concrete has a high compressive strength compared to conventional concrete, which has attracted much attention in recent years. With this type of concrete, the weight of the structure can be significantly reduced, and its important features include high compressive strength, low permeability, durability and abrasion resistance and high ductility that can absorb more energy during an earthquake. In this research, LIMESTONE POWDER was used instead of a part of silica sand. For this purpose, after obtaining optimal mixture ratios based on the compressive strength, consistency and diffusion diameter of flow table test, first, the LIMESTONE POWDER is considered as partial substitute of silica sand with percentages of 0, 10, 20, 30, and then in continuation, LIMESTONE POWDER is used as a substitute-additive with percentages and mixing ratios. Experiments conducted on these samples include testing the flow table, water absorption during curing and compressive strength at the age of 7, 28 and 90 days. The results of the experiments show that by increasing the LIMESTONE POWDER up to 20% replacement with silica sand, the compressive strength significantly increases, and also reduces the water absorption during of curing. The compressive strength of mixtures containing 20% LIMESTONE POWDER is 43% higher than the base concrete for 28-day samples. This increase in compressive strength for 7-day and 90-day samples is 39% and 42%, respectively. Water absorption during of curing for 28-day samples decreased by 19. 7%. In these experiments, it has been attempted to cure under normal environmental conditions (temperatures of 23 to 25 ° C without pressure) and also to be sufficiently fluid in condition of loose concrete or self compacting concrete, so it can easily be used in practical applications. For example, in connections with the number of overlapping reinforcements, ordinary concrete does not have the capacity to fill the very small spaces. In such connections we can use these mixtures. The cement content is 780kg. In order of cement content, it should be noted that the cement content of reactive POWDER concrete is about 700 to 1000 kg, and is used in mixtures up to 1200 kg. So here the cement content is moderate and the lower part of moderate. There is also no pressure and heat to be used in curing of concrete, and the amount of water and superplasticizer is somewhat higher than similar mixtures, so obtained fresh concrete is SCC. These conditions resulted in less compressive strengths than similar mixtures, but they are sufficiently strong for use in building projects, and even more so. The compressive strength of mixtures containing 20% LIMESTONE POWDER at 28 days of age reached 582 kg/cm2 and at 90 days of age, it reached648kg/cm2.

Durability of concrete in the environments containing sulfate ion has been accompanied with special concern for many reinforced concrete structures such as bridge decks and piers. Such structures as well as many other reinforced concrete structures have been suffering from corrosion due to existence of sulfate ions in soil or water adjacent to structure. Conventional methods like use of sulfate resistance cement in concrete has been utilized for long time; however, due to its limited effect and its unsuitability against some other harsh environments, alternative solutions like substitute of pozzolanic materials with a part of cementhas been attracting for many researchers and practical engineers. In the current study, to introduce a concrete with relatively high durability against sulfate ions, concretes containing slag and LIMESTONE POWDER were examined in sulfate environment. Since the concentration of sulfate ion in site is low and the corrosion of concrete adjacent to soil or water containing sulfate ion occurs during a long time, for evaluation of the effect of sulfate ion on concrete within a shorter period of time in the laboratory, it is necessary to perform accelerated experiments. The accelerator tests can be done by increasing the concentration of the sulfate ion and/or performing wetting and drying cycles on the concrete specimens. Accordingly, the solutions of 5% magnesium sulfate, 5% sodium sulfate and pure water were used as laboratory environments to perform the tests.To design the concrete mixes, ACI 363R was used to determine the ingredients; however according to ACI 211.4R-93, 30% reduction in water amount was utilized based on using super plasticizer in the mix. Liquid super plasticizer with Melamine base was used and the slump was stabilized about 80-100 mm. Besides the aforementioned codes, some modifications were made in the amount of solid ingredients based on the recommendations Mostofinejad and Nozhati.In order to evaluate the concrete deterioration process in sulfate ion, the reduction in compressive strength plus the weight changes in all specimens were measured; hence, the effect of the type of sulfate ion in different water-to-cement ratios and different ratios of LIMESTONE POWDER and slag on the decrease of weight and compressive strength of concrete was investigated. To do so, 27 mix designs including 15% and 30% substitute LIMESTONE POWDER and 10% and 20% substitute slag with the water-to-cement ratios of 0.3,0.4 and 0.5 were made and cast in 243 70×70×70 mm cubes. The test results on the specimens after 70 and 140 days showed that a combination of 10% slag and 15% LIMESTONE POWDER substitute to cement not only provides an economical mix design, but also fairly increases the durability-of concrete. Such a combination of cementitious materials could be recommended for concrete in sulfate environments; e.g. for construction of bridge piers.

Concrete is among the widely used materials in all industries and mineral and civil activities worldwide, highlighting its significance. Most natural and non-natural phenomena can influence the concrete's physical and mechanical properties, causing many irreparable damages. Acid rain is a natural inevitable phenomenon, particularly in industrial zones with high pollution percentages. This work investigates the effect of acid rain on the concrete specimens containing micro-silica and LIMESTONE POWDER. To this end, the concrete specimens are divided into six groups. Throughout this paper, CN represents the concrete without micro-silica and LIMESTONE POWDER under no-rain conditions, CO is the concrete without micro-silica and LIMESTONE POWDER under normal rain conditions, CA is the concrete without micro-silica and LIMESTONE POWDER under acid rain conditions, CMLN is the concrete containing micro-silica and LIMESTONE POWDER under no-rain conditions, CMLO is the concrete containing microsilica and LIMESTONE POWDER under normal rain conditions, and CMLA shows the concrete containing micro-silica and LIMESTONE POWDER under acid rain conditions. The measured physical properties are the effective porosity, dry density, water absorption, and velocity of longitudinal waves. The mechanical properties including the Brazilian tensile strength, uniaxial compressive strength, triaxial compressive strength, cohesion, and internal friction angle are also measured. For the samples of CN and CMLN, they are tested under no rainfall conditions, whereas the samples of CA and CMLA are tested after 20 cycles of acid rain (pH = 2). The samples of CO and CMLO are also tested after undergoing 20 normal rain cycles (urban water with pH = 7). In each test cycle, there is 1 hour of rain and 1 hour of no rain. The results obtained show that adding micro-silica and LIMESTONE POWDER improves its properties so that the decrease in the effective porosity, longitudinal wave velocity, dry unit weight, water absorption, Brazilian tensile strength, uniaxial compressive strength, cohesion, and internal friction angle of the specimens of CMLA is less than those for the specimens of CA.