Reactive Powder Concrete Mixture Research Articles

Mechanical Properties and High Temperature Performance of Sustainable Reactive Powder Concrete Containing Waste Glass

At present, it is a challenge to produce a high performance reactive powder concrete (RPC) from local available materials due to the least costly components of a conventional concrete are eliminated by more expensive elements such as the silica fume and steel fibers. In the other hand, million tons of glass is being dumped every year all over the world. More than 75% of glass composition is basically silica and reported to having a pozzolanic reaction. Thus, glass is potentially suitable material as replacement materials for the RPC mixture. In our work, waste glass powder (WGP) was used to completely replace silica fume. Compressive strength, splitting tensile strength, flexural strength and elastic modulus measurements were reported along with the density and colour of the RPC produced. The highlight of this study is on the assessment of the RPC at high temperature tested by direct burning at 600˚C. This had addressed to a very limited reported finding on the high temperature performance of RPC utilizing waste materials. It was found that, RPC containing waste glass powder changes the colour of RPC from darkish grey to light grey. Adding waste glass powder had reduced the density of RPC by (0.05) gm/cm3. Using waste glass powder instead of silica fume had also improves the mechanical properties of RPC. However, there is no effect of adding waste glass powder in solving the spalling problem of RPC at high temperature up to 600˚C. This paper reports finding on the mechanical properties and high temperature performance of sustainable RPC that utilize waste glass powder in total replacement for the silica fume. This is carried out as an effort to address the high cost of the material used in the ordinary RPC and to enhance the recycling of local waste glass.

Formulation of inexpensive and green reactive powder concrete by using milled-waste-glass and micro calcium-carbonate – A multi-criteria optimization approach

In view of its high strength and durability, reactive powder concrete (RPC) is a promising construction material. The replacement of cement and silica fume with sustainable alternatives to RPC may provide significant benefits, however, there are challenges to overcome. In this study, calcium carbonate and ground waste glass powder were introduced as mineral mixtures to develop an environmentally friendly and cost-effective RPC mixture. The best flowability, proper compressive strength, and reduced cement content were achieved using a multi-objective simultaneous optimization approach based on the Derringer & Suich methodology. As a result of the study, 603 kg/m3 of cement was determined as the most suitable dosage for RPC. Additionally, the optimized mix contained 368 kg/m3 of waste glass and 118 kg/m3 of calcium carbonate, which had a beneficial impact on both cost and environmental considerations. As a result of numerous experimental tests, including compressive strength, elasticity modulus, chloride ion penetration, and drying shrinkage, the developed RPC's properties were validated and were comparable to the control mixture while showing superior drying shrinkage behavior. A further benefit of adding these admixtures was the reduction of superplasticizer dosage. Despite the optimized RPC's lower mechanical and chloride ion penetration performance at early ages, the performance discrepancy diminished over time due to the pozzolanic properties of waste glass powder. A significant characteristic of the optimized RPC was its superior drying shrinkage behavior throughout the testing period resulting from its reduced water dosage. Ultimately, the study highlights the potential of the addition of calcium carbonate and waste glass powder to RPC for sustainable concrete production at a low cost.

The Effects of Silica Fume and Superplasticizer Type on the Properties and Microstructure of Reactive Powder Concrete.

This paper deals with the optimization of reactive powder concrete mixtures with respect to the addition of silica fume and the type of polycarboxylate superplasticizer used. First, the properties of reactive powder concrete with eight different commercial polycarboxylate superplasticizers were tested in terms of workability, specific weight, and mechanical properties. It was found that different commercially available superplasticizers had significant effects on the slump flow, specific weight, and compressive and flexural strengths. The optimal superplasticizer (BASF ACE430) was selected for further experiments in order to evaluate the influences of silica fume and superplasticizer content on the same material properties. The results showed that the silica fume and superplasticizer content had considerable effects on the mini-cone slump flow value, specific weight, flexural and compressive strengths, and microstructure. There were clearly visible trends and local minima and maxima of the measured properties. The optimal reactive powder concrete mixture had a composition of 3.5-4.0% superplasticizer and 15-25% silica fume.

Intelligent data-driven compressive strength prediction and optimization of reactive powder concrete using multiple ensemble-based machine learning approach

In recent years reactive powder concrete (RPC), also known as ultrahigh-performance concrete, emerged as one of the most efficient building materials due to its ultrahigh compressive strength (usually greater than 150 MPa), ductility, and durability. The existing literature presents a wealth of experimental data exploring the intricate interactions among the various components within RPC mixtures, emphasizing the requirement for a potent and efficient model to optimize, simulate, and enrich the understanding of RPC mixture characteristics. This study presents a notable attribute utilizing a multilayer stacked model that harnesses the potential to harmoniously seamlessly integrate and synergize various machine learning (ML) algorithms. An extensive dataset from reliable resources in the literature was used to develop a new ML model for predicting the compressive strength of RPC. It was found that there is a strong positive correlation between the RPC’s compressive strength and the dosage of silica fume, fiber dosage, and age of concrete. In contrast, water content and dosage of GGBFS were observed to have a low correlation with the compressive strength of the RPC. The most significant features were age, fiber dosage, silica fume content, cement content, HRWR dosage, fine aggregate content, and water content. Further, in this study, predictive efficacy identifies the stacking algorithm as optimal, followed by XGBoost, RF|ETR, and KNN. Notably, R2 strengths vary: stacking achieves 0.96, XGB sustains 0.954, RF and ETR hold 0.95, while KNN reaches 0.77.

Development of a novel 124 MPa strength green reactive powder concrete employing waste glass and locally available cement

In this study, a new reactive powder concrete (RPC) was developed, with environmentally friendly typical RPC components obtained from ground quartz substituted by the waste glass. In this manner, the carbon footprint and final cost are minimized by replacing aggregates and reducing cement. A challenge in this study was using high-celite phase available cement and avoiding the alkali-silica reaction. The Box–Wilson design and Derringer–Suich optimization were used to create an RPC mixture with a low cement content and high-volume waste glass dosage that achieved a compressive strength of more than 120 MPa. It was demonstrated that having all ground waste glass particles smaller than 1000 µm is not sufficient to prevent the alkali-silica expansion. Furthermore, commercially available cement with a high celite proportion had a modest beneficial influence on the compressive strength at an early-age but a significant detrimental impact on the RPC’s compressive strength at 28 days. Finally, the current study proved the potential of manufacturing an RPC that satisfied the strength threshold criterion while utilizing a local cement with over 12% celite and a substantial volume of waste glass powder comprising more than half of the RPC weight.

Mechanical Properties and Pore Structure of Multiwalled Carbon Nanotube-Reinforced Reactive Powder Concrete for Three-Dimensional Printing Manufactured by Material Extrusion.

Three-dimensional (3D) concrete printing technology has been considered promising, attracting extensive attention in the engineering field. Multiwalled carbon nanotubes (MWCNTs) have been used as an additive to reinforce the cement-based material. However, the research on the 3D printed MWCNT-reinforced high-strength concrete is rare. This research is to study the mechanical properties and pore structure of MWCNT-reinforced reactive powder concrete (RPC) for 3D printing. In this research, the workability of the printed RPC mixture with MWCNTs was first tested to pass the criteria of 3D printing. Then, the enhancement effect of MWCNTs on the printed RPC was tested by mechanical properties after hardening. Meanwhile, strength-displacement curves were recorded. In addition, the pore structures of printed RPC were observed and analyzed by X-ray computed tomography (CT) images. The results show that 0.05 wt% MWCNTs have no effect on the workability of the printable RPC slurry. MWCNTs could enhance the mechanical properties of the printed RPC by filling the flaws inside the samples, increasing the viscosity of the RPC slurry and forming bridges between cracks. Besides, 0.05 wt% MWCNTs may cause the failure mode of the printed RPC from brittle failure to ductile failure. In addition, MWCNTs significantly reduced the porosity of the printed RPC by decreasing pores with a volume over 0.01 mm3. As CT images show, the interlayer zone (IZ) of the 3D printed RPC sample is prone to pores, and a higher volume fraction is evident. In particular, within the volume of IZs, the minimum volume fraction at the IZ of 3D printed RPC appears on sample with MWCNTs.

Optimization of mixture parameter for physical and mechanical properties of reactive powder concrete under external sulfate attack using Taguchi method

• Taguchi analysis has been used to determine optimum mix design parapeter of RPC exposed to different Na 2 SO 4 solutions and exposure conditions. • Optimized level for RPC mixture with different water to binder ratio, steel fiber contents, and silica fume contents depends on different external sulfate attack exposure conditions. • RPC appears to be sustainable and durable material under different external sulfate attack exposure conditions. Reactive powder concrete (RPC) is defined as a cementitious composite material with an optimized size of granular constituents, very low water-to-binder ratio (w/b), pozzolanic materials like silica fume (SF), and discontinuous fiber reinforcement. RPC applications include bridge decks and girders, seismic columns, wind turbine towers, and pile foundations. Especially, a durable and robust RPC pile foundation with long service life is essential in building construction because continuous maintenance is impossible. Moreover, natural in-situ conditions such as water table, temperature, and sulfate concentration in soil to which the pile foundation is exposed are critical and related to deteriorating the pile foundation. Therefore, the Taguchi design of experiments (DOE) was used in this research to determine the optimal RPC mixture with beneficial characteristics against external sulfate attack (ESA). Mixture design parameters included steel fiber content (0, 1 and 2 %), w/b (0.16, 20 and 0.24), and SF content (15, 20 and 25 %). In contrast, environmental conditions of ESA exposure contained three different sodium sulfate (Na 2 SO 4 ) concentrations (0.35, 1.05, and 3.15 M), cyclic and continuous exposure at normal temperature (20 °C), and continuous exposure at elevated temperatures (40 °C and 60 °C). The analytical and statistical investigation evaluated mass change, compressive strength, and modulus of rupture in RPC mixtures exposed to these conditions for 52 weeks. Test results show that cyclic exposure and increased solution temperature in ESA facilitate RPC damage. If measured after air drying, RPC mixtures subjected to cyclic ESA are especially susceptible to failure. Taguchi analysis indicated the optimum parameters’ level for mass change as: 0 % steel fiber, w/b = 0.16, and 20 % SF content; for the compressive strength: 2 % steel fiber, w/b = 0.24, and 20 % SF content; and, for modulus of rupture: 2 % steel fiber, w/b = 0.20, and 25 % SF content. In conclusion, RPC appears to be sustainable and durable material under different ESA exposure conditions.

Performance evaluation of fiber-reinforced reactive powder concrete exposed to high temperature combining nondestructive test

An experimental study has been performed in an attempt to evaluate the performance of fiber-reinforced reactive powder concrete (RPC) after high temperatures using nondestructive methods. In this context, four RPC mixtures containing 2% steel fibers and 0–0.2% polypropylene (PP) fibers were produced. After samples exposure to various temperatures 20 °C, 100 °C, 200 °C, 300 °C, 400 °C, 500 °C, 600 °C, 700 °C and 800 °C, different non-destructive tests (NDTs) including ultrasonic pulse velocity (UPV) and resonance frequency (RF) as well as sound velocity calibration tests were conducted. Besides, specimens damage roughly assessed by physical observation and mass loss. Further on, mechanical performance was evaluated by axial compressive strength, and scanning electron microscopy (SEM) was employed to understand the high temperature deterioration mechanism of RPC specimens. The results indicated that mass loss and NDTs parameters values gradually deteriorated with the increasing temperature. Additionally, the compressive strength raised up to 200 °C. Nevertheless, it dropped dramatically from 200 °C to 700 °C. After that, the strength increased mildly. The weight loss and residual strength as well as NDTs parameters were related to temperature and fiber content. Moreover, quantitative description formulas of mentioned factors were presented. It was also found that 2% steel fiber and 0.15% PP fiber seems to be the optimal fiber combination always performed better in comparison with other fiber contents regarding the residual compressive strength and NDTs parameter values. Furthermore, the regression equations between compressive strength and NDTs values have been provided with all correlation coefficients exceed 0.95. The research demonstrated the potential of the NDTs methods for application of fiber-reinforced RPC exposed to high temperatures.

Assessment of Reactive powder concrete subjected to three different sodium sulfate Concentrations: Compressive Strength, Absorption, Porosity, Microstructure, and durability

Reactive Powder Concrete (RPC) is a relatively new type of concrete material characterized by very low water-to-binder ratios (w/b), the addition of supplementary cementitious materials like silica fume (SF), and the presence of very fine aggregates instead of conventional coarse aggregates. The durability of RPC with various w/b (0.18, 0.22, and 0.26) and SF content (15%, 20%, and 25%) against external sulfate attack (ESA) at various sodium sulfate (Na2SO4) concentrations (0.35 M, 0.7 M and 1.4 M) was investigated in this study through examinations of compressive strength, expansion and mass change, microstructural characteristics, mineralogy, porosity, and sorptivity. The results indicated that: 1) owing to its improved microstructure, RPC could accommodate expansive products of ESA reactions, which can provide additional strength; 2) RPC showed very high resistance to Na2SO4 attack under the ASTM C1012 criteria; 3) considerable sulfate ingress did not result in significant expansion and strength reduction for RPC mixtures at early stages of exposure, especially for the mixtures with high initial sorptivity and high interparticle connectivity; 4) considering the coupled effect of w/b and SF content on the number of RPC characteristics, mixture with w/b = 0.22 and 20% SF content showed the best performance upon exposure to ESA.

A Study of the Residual Strength of Reactive Powder-Based Geopolymer Concrete under Elevated Temperatures

This paper reports on studies relating to the unstressed residual compressive strengths of geopolymer pastes that are heated up to 800 °C, behavior of reactive powder concrete before and after exposure to elevated temperatures and thermal behavior of novel reactive powder geopolymer-based concretes. For this purpose, 10 geopolymer pastes and three reactive powder concrete mixtures were tested for residual strengths. Gladstone fly ash was used as the primary binder for both geopolymer pastes and reactive powder geopolymer concretes. In addition, four novel reactive powder geopolymer concrete mixes were prepared with zero cement utilization. While reactive powder concretes achieved the highest seven-day compressive strengths of approximately 140 MPa, very poor thermal behavior was observed, with explosive spalling occurring at a temperature of ca. 360 °C. The reactive powder geopolymer concretes, on the other hand, displayed relatively high thermal properties with no thermal cracking at 400 °C, or visible signs of spalling and very mild cracking in one case at 800 °C. In terms of the strength of reactive powder geopolymer concrete, a maximum compressive strength of approximately 76 MPa and residual strengths of approximately 61 MPa and 51 MPa at 400 °C and 800 °C, respectively, were observed.

Mechanical Behavior of Reactive Powder Concrete Made From Local Material Subjected to Axial Pressure

In order to investigate the influence of various parameters on the compressive strength and fluidity of reactive powder concrete (RPC) made from local materials, 22 groups of RPC cubic specimens and 3 groups of RPC prism specimens were designed, and the main parameters included water to binder ratio, the ratio of silica fume to cement, the ratio of slag powder to cement, the ratio of quartz sand to cement, volume fraction of steel fiber, and steam curing time. The stress-strain curves and failure mode of RPC cubic specimens were obtained by the axial compression test. The influence of various parameters on the compressive mechanical properties and the mixture fluidity of RPC cubic specimens was analyzed. The results showed that the ultimate compressive strength (fcu) of RPC gradually decreases with the increase in the water to binder ratio; however, fcu increases with the increase in the volume fraction of steel fiber. fcu increases firstly and then decreases with the increase in the ratio of silica fume to cement, the ratio of slag powder to cement, and the ratio of quartz sand to cement, so there exists a peak point. The fluidity of RPC mixture increases with the increase in the water to binder ratio and the ratio of slag powder to cement; on the contrary, it decreases with the increase in the ratio of silica fume to cement, the ratio of quartz sand to cement, and volume fraction of steel fiber. Based on the analysis of the parameters, the optimal mix proportion of the RPC made from local materials is proposed. The constitutive model of RPC is established according to the stress-strain curves of RPC prism specimens. Finally, the relationship between compressive strength and elastic modulus of RPC made of local materials is regressed statistically.

The Design of Reactive Powder Concrete (RPC) Mixtures Using Aceh Quartzite Powder

Original reactive powder concrete (RPC) consists of a large amount of cement, fine sand, crushed quartz, and silica fume, with a very dense matrix achieved by optimizing the granular packaging of the materials. This study, therefore, applied the modified Andreasen & Andersen particle-packing model using Aceh quartzite powder to design a densely compacted matrix and low cement content RPC mixtures. The research involved the preparation of two series of the mixture with different percentages of silica fume and Aceh quartzite powder and the 70.7 mm cube specimens were treated with combined steam curing and normal curing after which their compressive strength was tested at the age of 7 days and 28 days. The result showed the use of 61% local quartzite powder by weight of cement through an optimized mix design and cured treatment improves the RPC strength at any variation of silica fume.

Mechanical properties of reactive powder concrete under distinct curing environment

Reactive Powder Concrete (RPC) is composed of fine powders (cement, sand, quartz powder and silica fume), steel fibres (optional) and superplasticizer. This gives good compaction and an impenetrable matrix is achieved, and this strong concentration gives RPC, an ultra-high strength and durability properties. In this research work, focus was aimed to produce reactive powder concrete (RPC) composite material with compression strength up to 100 N/mm2. Components for RPC mixture are carefully selected to achieve optimal mixture. Detailed concrete mix proportions are given in this research paper. Preparation and testing of material were produced in laboratory belonging to the Department of Civil Engineering in SRM Institute of Science and Technology. Casting of concrete cubes and beams was done for both M60 and M100 grades of concrete. This paper investigates mechanical and fresh concrete properties of reactive powder concrete for both the design mix. Laboratory investigations like; Compressive test, split tensile test and flexural strength were conducted to evaluate strength characteristics of RPC, under different curing conditions like oven, steam, and hot water with respect to time factor of T1 (60 min), T2 (61-90 min) and T3 (91-120 min). In every aspect of testing, the steam curing at 100°C shows improved results of 15.71-17.40% in compressive strength, 24.66-25.93% in tensile strength and 20% in flexural strength for both grades of concrete

The Effect of Various Polynaphthalene Sulfonate Based Superplasticizers on the Workability of Reactive Powder Concrete

A superplasticizer is a type of chemical admixture used to alter the workability (viscosity) of fresh concrete. The workability of fresh concrete is often of particular importance when the water-to-cement (w/c) ratio is low and a particular workability is desired. Reactive Powder Concrete (RPC) is a high-strength concrete formulated to provide compressive strengths exceeding 130MPa and made of primarily powders. RPC materials typically have a very low w/c, which requires the use of a chemical admixture in order to make the material workable for placing, handling and consolidating. Superplasticizer are commonly used for this purpose. Superplasticizers are developed from different formulations, the most common being Polynaphthalene Sulfonate (PNS), Polymelamine Sulfonate (PMS) and Polycarboxylate Ether (PCE). This study investigates the impact of various PNS based superplasticizers on the compressive strength and rheological performance of a RPC mixture. Six different types of PNS based superplasticizers were used; three of various compositional strengths (high, medium, low range) from a local provider, and three of the same compositional strengths (high, medium, low) from a leading manufacturer. Specific properties assessed were the superplasticizers viscosity, concrete workability through the mortar-spread test, concrete rheology, and 7, 14, and 28 day RPC compressive strengths. Two mixtures were produced with two w/cm (0.20 and 0.15), which would subsequently increase the amount of superplasticizer needed, from 34.7L/m3 to 44.5L/m3. The results show that the name brand high range composition produced the overall highest spread, lowest viscosity, and a highest compressive strength at all ages tested. However, the local provider outperformed the name brand in the mid and low range compositions. Additionally, the rheology test also demonstrated that the name brand high range, and RPC produced with the name brand high range, had a lower viscosity at all angular speeds than the others tested.

Properties of reactive powder concrete containing different combinations of fly ash and metakaolin

Reactive powder concrete (RPC) is a special type of concrete that has excellent properties, especially compressive strength. However, one of the disadvantages of RPC is that it has a high cement content, which can reach 1000 kg/m3. Because of the high cost of producing cement and the greenhouse gas emissions associated with its manufacture, researchers have resorted to investigating alternatives to cement, including supplementary cementitious materials. Accordingly, this research aims to produce environmentally friendly RPC in which 50% of the cement was replaced by metakaolin (MK) and fly ash (FA) combinations. To achieve the aim of the study, three RPC mixtures: 10MK + 40FA, 15MK + 35FA, and control mixture (without replacement) were cast. The fresh and mechanical properties tests were performed. The results showed that the combination of MK and FA improved the fresh properties of RPC, while the hardening properties were decreased.

The Influence of the Use of Cement Brands on the Physical and Mechanical Properties of Reactive Powder Concrete (RPC)

The most popular building material today is concrete. Concrete is used for buildings, industrial structures, bridges, railroad sleepers, roads, dams and more. Along with the development of concrete technology is increasingly developing and innovative so as to achieve better characteristics, cheaper prices and environmentally friendly. In the early days of the development of concrete it is explained to us about the origin from ancient times to civilization to the present century of its development. In current developments, concrete already has a very high compressive strength up to 200-800 MPa, this is also called Ultra Hight Concrete (UHC). It is developed by the Reactive Powder concrete (RPC) method. Where in the research conducted, the manufacture of reactive material, namely Reactive Powder concrete (RPC) was given with a compressive strength of up to 52 MPa. The components of the RPC mixture consist of cement, fine aggregate, silica fume, superplasticizer and water. To produce a compressive strength of 52 MPa, the composition of the mixture used previous research. Detailed RPC concrete mix proportions are given in this study. Preparation and testing of materials are made in the laboratory of the Faculty of Civil Engineering in Untan. The results that will be obtained are the physical and mechanical properties of RPC Concrete. As previously explained, the manufacture of RPC concrete requires basic ingredients that include cement, fine aggregate, silica fume, superplasticizer and water mixed together. Of course, with basic ingredients with good and correct composition, the physical and mechanical properties of RPC concrete will reach the planned quality. Cement sold in the market today has PPC and PCC types. Therefore, the cement which is a binder of powder materials into a solid one plays a very important role in the formation of the best physical and mechanical properties of RPC concrete. With cement as a binding material, it is certain that the strength of RPC concrete is determined by the binding capacity of the type of cement to be used, thus RPC concrete will be obtained according to the planned quality of the plan. From the cement brands on the Indonesian market consisting of PPC and PCC cement types, it can be concluded that one of the cements using the PCC type cement brand has better physical and mechanical properties than the PPC type cement brand. And all brands of cement with PCC type produce compressive strength > 52 MPa. So, in the manufacture of RPC concrete it is recommended to use a cement brand with PCC type.

PENGARUH PENAMBAHAN SERAT BAJA TERHADAP SIFAT MEKANIS REACTIVE POWDER CONCRETE

As urban growth increase, massive high-rise building construction become a critical solution. In high-rise building, column base may be subjected to very high axial load from the upper stories and may experience very large moment due to the lateral loads. As a result, the column base requires a great deal amount of reinforcement which make it very cramped. In order to prevent honeycomb as the reinforcement gap is narrow yet difficult to provide sufficient vibration during concrete casting, high performance concrete (HPC) may be the solution. One of the HPC innovations is Reactive Powder Concrete (RPC). RPC is a self-compacting type of HPC contains well graded fine and super fine aggregates with cement and pozzolanic material to strengthen the Interfacial Transition Zone (ITZ) between the mortar matrix and fine aggregates. RPC may achieve high compressive strength as the mix uses low water to cement ratio, thus it introduces less void and no coarse aggregates, thus ITZ is stronger. RPC has similar characteristic as concrete, with its brittle behaviour. To avoid the brittle failure of RPC, in this study steel fibers are added into the RPC mixture. This research is conducted to examine the effectiveness of using steel fibers on the mechanical properties of Steel Fiber Reactive Powder Concrete (SFRPC). The steel fiber is aimed to increase ductility of tensile strain hardening condition by its multiple crack-bridging behavior.

Effects of elevated temperatures on mechanical properties of reactive powder concrete elements

Although reactive powder concrete (RPC) is a well-known composite that achieves high rates of compressive strength, its behavior during fire still questionable. This study investigates the mechanical characteristics of RPCs following exposure to high temperatures. RPCs were prepared using high quantities of cement, silica, quartz, and fine aggregates, very small quantities of water (w/c less than 0.25). The testing was carried out on five different RPC mixtures: control mixture (plain RPC), and four test mixtures (RPC with glass, steel, polypropylene (PP), and a hybrid of steel and PP fibers). RPCs were analyzed to explain the original and residual mechanical conduct and spalling during different temperatures between 25 °C and 800 °C. After exposure to elevated temperatures, specimens were testedfor compressive, flexural, and indirect tensile strengths. Appearance and color change, spalling, mass loss ratio, and ultrasonic pulse velocity (UPV) were examined as well.Compressive and tensile strengths for RPC’s mixes and flexural strength for RPC with steel fibers and RPC with steel and PP fibers gradually increases when specimens heated to 200 °C. However, the strengths of all mixes begin to drop as temperatures rise.Although RPC with steel and PP fibers had a high loss of its original compressive, tensile, and flexural strength at 800 °C, this RPC showed the best performance regarding spalling resistance and mechanical characteristics compared to the other types of RPCs. Also, all RPC mixes showedincreasing in mass loss and decreasing in UPV with temperature increase until spalling or became doubtful.

Abrasion of Reactive Powder Concrete under Direct Water Impact

An experimental program was directed in this study to evaluate the abrasion resistance of reactive powder concrete (RPC) under direct normal impact of water jet. Abrasion and compressive strength specimens were cast from six RPC mixtures using different single and hybrid distributions of 6 mm-length and 15 mm-length micros-steel fibers and 18 mm-length polypropylene fiber. Fixed mix proportions were used for the six RPC mixtures and with fixed total volumetric fiber content of 2.5%. In addition to the RPC mixtures, a normal concrete mixture was prepared for comparison purposes. All specimens were cured in the same conditions and tested at an age of 28 days. The test results showed that abrasion weight losses increase with time at rates that are independent of fiber type and fiber distribution. The results also showed that all RPC mixtures exhibited significantly lower abrasion losses than normal concrete. The lowest percentage abrasion weight losses were recorded for the mixture with pure 15 mm micro-steel, where after 12 testing hours, it was 0.41% of the total weight before testing. On the other hand, the mixture with pure 6 mm micro-steel fiber exhibited the highest percentage abrasion weight loss (0.98%) among the six RPC mixtures. Another conclusion is that the inclusion of polypropylene fiber to compose hybrid fiber distribution with micro-steel fiber led mostly to lower abrasion losses.

Reactive Powder Concrete Mix Ratio and Steel Fiber Content Optimization under Different Curing Conditions.

In this paper, a practical reactive powder concrete mixture ratio is created on the basis of an orthogonal experiment. Previous studies have combined the compressive and splitting tensile strengths of four categories of reactive powder concrete (RPC) for major materials. These categories include water/binder ratio, silica fume volume content, sand/binder ratio, and dosage of fly ash volume. The optimal mixing proportion of each factor was determined by analyzing the compressive strength of the RPC matrix. For this purpose, steel fiber was used as a reinforcing agent. The compressive and splitting tensile strength test results of steel fiber RPC were analyzed by comparing compound, standard, and natural curing. This was conducted to explore the improvement effect of different steel fiber contents on compressive performance, especially tensile strength of the RPC matrix. According to the results, the optimal steel fiber content was found to be 4% under the three curing conditions. The effect of compound curing on early strength was found to be greater in RPC than by natural or standard curing. However, the effect of late improvement is not obvious. Although standard curing is slightly stronger than natural curing, the performance under the latter can still meet engineering requirements.