Showing papers on "Polymer concrete published in 2011"

The influence of curing conditions on the mechanical performance of concrete made with recycled concrete waste

Abstract: Research on the use of Construction and Demolition Waste (CDW) as recycled aggregate (in particular crushed concrete) for the production of new concrete has by now established the feasibility of this environmentally-friendly use of otherwise harmful waste. However, contrary to conventional concrete (CC), no large applications of concrete made with recycled concrete have been made and there is still a lack of knowledge in some areas of production and performance of recycled aggregate concrete (RAC). One issue concerns curing conditions: these greatly affect the performance of concrete made on site and some potential users of RAC wonder how RAC is affected by far-from-ideal curing conditions. This paper shows the main results of experiments to determine the influence of different curing conditions on the mechanical performance of concrete made with coarse recycled aggregate from crushed concrete. The properties analyzed include compressive strength, splitting tensile strength, modulus of elasticity, and abrasion resistance. The general conclusion in terms of mechanical performance is that RAC is affected by curing conditions roughly in the same way as CC.

Bond strength of reinforcing steel embedded in fly ash-based geopolymer concrete

Abstract: Geopolymer concrete (GPC) is an emerging construction material that uses a by-product material such as fly ash as a complete substitute for cement. This paper evaluates the bond strength of fly ash based geopolymer concrete with reinforcing steel. Pull-out test in accordance with the ASTM A944 Standard was carried out on 24 geopolymer concrete and 24 ordinary Portland cement (OPC) concrete beam-end specimens, and the bond strengths of the two types of concrete were compared. The compressive strength of geopolymer concrete varied from 25 to 39 MPa. The other test parameters were concrete cover and bar diameter. The reinforcing steel was 20 mm and 24 mm diameter 500 MPa steel deformed bars. The concrete cover to bar diameter ratio varied from 1.71 to 3.62. Failure occurred with the splitting of concrete in the region bonded with the steel bar, in both geopolymer and OPC concrete specimens. Comparison of the test results shows that geopolymer concrete has higher bond strength than OPC concrete. This is because of the higher splitting tensile strength of geopolymer concrete than of OPC concrete of the same compressive strength. A comparison between the splitting tensile strengths of OPC and geopolymer concrete of compressive strengths ranging from 25 to 89 MPa shows that geopolymer concrete has higher splitting tensile strength than OPC concrete. This suggests that the existing analytical expressions for bond strength of OPC concrete can be conservatively used for calculation of bond strength of geopolymer concrete with reinforcing steel.

Compressive strength and durability properties of ceramic wastes based concrete

Abstract: This paper presents an experimental study on the properties and on the durability of concrete containing ceramic wastes. Several concrete mixes possessing a target mean compressive strength of 30 MPa were prepared with 20% cement replacement by ceramic powder (W/B = 0.6). A concrete mix with ceramic sand and granite aggregates were also prepared as well as a concrete mix with natural sand and coarse ceramic aggregates (W/B = 0.5). The mechanical and durability performance of ceramic waste based concrete are assessed by means of mechanical tests, water performance, permeability, chloride diffusion and also accelerated aging tests. Results show that concrete with partial cement replacement by ceramic powder although it has minor strength loss possess increase durability performance. Results also shows that concrete mixtures with ceramic aggregates perform better than the control concrete mixtures concerning compressive strength, capillarity water absorption, oxygen permeability and chloride diffusion. The replacement of cement and aggregates in concrete by ceramic wastes will have major environmental benefits.

Characterization of self-compacting concretes prepared with different fibers and mineral additions

Abstract: In this work, several self-compacting concretes were prepared by using three different types of fibers made of steel, poly-vinyl-alcohol (PVA) and high toughness poly-propylene (PPHT) and two different types of mineral addition (limestone powder and powder from recycled concrete). The water to cement ratio was held constant at 0.40. Fresh concrete behavior was evaluated by means of slump flow, V-funnel and L-box tests while the hardened concrete behavior was evaluated by means of flexure and compression tests, as well as free drying and restrained plastic shrinkage tests. Excellent performances were generally obtained, particularly for the self-compacting concretes prepared with steel fibers and powder from recycled concrete.

Durability studies on copper slag admixed concrete

Abstract: Utilization of industrial soil waste or secondary materials has encouraged in construction field for the production of cement and concrete because it contribute to reducing the consumption of natural resources. Copper slag is one of the materials that is considered as a waste which could have a promising future in construction Industry as partial or full substitute of either cement or aggregates. Many researchers have already found it possible to use copper slag as a concrete aggregate. But not much research has been carried out in India concerning durability and corrosion studies of copper slag admixed concrete. This paper presents the results of an experimental study on various corrosion and durability tests on concrete containing copper slag as partial replacement of sand and cement. For this research work, M20 grade concrete was used and tests were conducted for various proportions of copper slag replacement with sand of 0 to 60%, cement of 0 to 20% in concrete. The obtained results were compared with those of control concrete made with ordinary Portland cement and sand.

Effects of the fine recycled concrete aggregates on the concrete properties

Abstract: In this experimental study, the effects of the recycled fine recycled concrete aggregate (FRA) that was manufactured from concrete wastes on the concrete properties were investigated. In concrete mixtures, 0, 10, 20, 30, 40, 50 and 100% by weight FRA were used instead of river sand. Afterwards, unit weight and water absorption ratios and 28-day compressive strength were determined. According to the test results obtained, it was seen that FRA can be used up to 10 % ratio for producing C30 concrete, between 20-50% ratios for producing C25 concrete. Thus, environmental impacts and consumption of the natural resources can be significantly reduced by using recycled fine concrete aggregates in concrete applications. Key words: Compressive strength, concrete, normal crushed aggregate, recycled fine concrete aggregate, waste concrete.

Structural Concrete Prepared with Coarse Recycled Concrete Aggregate: From Investigation to Design

Abstract: An investigation of mechanical behaviour and elastic properties of recycled aggregate concrete (RAC) is presented. RACs were prepared by using a coarse aggregate fraction made of recycled concrete coming from a recycling plant in which rubble from concrete structure demolition is collected and suitably treated. Several concrete mixtures were prepared by using either the only virgin aggregates (as reference) or 30% coarse recycled aggregate replacing gravel and by using two different kinds of cement. Different water-to-cement ratios were adopted ranging from 0.40 to 0.60. Concrete workability was always in the range 190–200 mm. Concrete compressive strength, elastic modulus, and drying shrinkage were evaluated. Results obtained showed that structural concrete up to C32/40 strength class can be manufactured with RAC. Moreover, results obtained from experimentation were discussed in order to obtain useful information for RAC structure design, particularly in terms of elastic modulus and drying shrinkage prediction.

Design and Control of Concrete Mixtures: The guide to applications, methods, and materials

Abstract: The properties of concrete as needed in concrete construction, including strength and durability, are presented in this book. In terms of their optimal use in designing and proportioning concrete mixtures, all concrete ingredients (cementing materials, water, aggregates, admixtures, and fibers) are reviewed. American Society for Testing and Materials (ASTM), American Association of State Highway and Transportation Officials (AASHTO) and Association of the Cement Industries (ACI) standards are extensively referred to, as applicable. Also addressed is the use of concrete from design to batching, mixing, transporting, placing, consolidating, finishing, and curing. Reviewed as well are concrete sustainability, along with special concretes, including high-performance concretes.

Polymer concretes: A description and methods for modification and improvement

Abstract: Portland cement concrete (PCC) has been successful in many applications. However, since the 1960s technological investigations concerning modificatio ns of concrete by polymeric materials have been conducted. Attention has been focused on concretes in which the continuous phase is some kind of polymeric resin and the discrete phase is some type of mineral aggregate. Such composite materials are known as Polymer concrete (PCt) and boast sever al advantages such as higher strength and a shorter curing process. In spite of these advantage s, th re are deficiencies that could be addressed b y fiber incorporation into PCts, however this kind of approach is not typical. Here we acquaint readers with the nature of polymer concretes as these mater ials have not yet gained wide recognition. We describe recent developments regarding the influenc e of fiber reinforcements on PCts. The curing process is a critical concern in dealing with polym er concretes as it is with Portland cement concrete . Studies on the effects of gamma ionizing radiation on the curing process and on final properties of PCts are ongoing. Developments in this area are als o de cribed here. In particular, the effects of gamma irradiation on the mechanical properties are discussed. Notably, improvements of the Young’s modulus E described here have wider implica tions and may be indicative of improvements or modifications to other properties not directly t ested. Specifically, the modifications to the Young ’s modulus can be a defining measure of whether one wi ll obtain a ductile or more brittle concrete.

Fibre reinforced concrete using domestic waste plastics as fibres

Abstract: Fiber Reinforced Concrete (FRC) is a composite material consisting of cement based matrix with an ordered or random distribution of fiber which can be steel, nylon, polythene etc. The addition of steel fibre increases the properties of concrete, viz., flexural strength, impact strength and shrinkage properties to name a few. A number of papers have already been published on the use of steel fibres in concrete and a considerable amount of research has been directed towards studying the various properties of concrete as well as reinforced concrete due to the addition of steel fibres. Hence, an attempt has been made in the present investigations to study the influence of addition of polythene fibers (domestic waste plastics) at a dosage of 0.5% by weight of cement. The properties studied include compressive strength and flexural strength. The studies were conducted on a M20 mix and tests have been carried out as per recommended procedures of relevant codes. The results are compared and conclusions are made.

Effect of aging on the fracture mechanics of unsaturated polyester based on recycled PET polymer concrete

Abstract: This research investigates, the fracture mechanics (toughness and energy), at early ages, of polymer concrete made with unsaturated polyester resin as binder. The results indicate that the fracture parameters (toughness and energy) decrease and the brittleness increases with the age of the polymer concrete.

Experimental study on properties of pervious concrete made with recycled aggregate

Abstract: This paper investigates recycled aggregate (RA) obtained from construction waste, with a particular focus on the properties of pervious concrete. The authors reveal the mechanical performance and permeability of pervious concrete with regard to volume fraction of the binder (binder/voids between aggregate), type of binder (cement paste and styrene-butadiene latex modified paste), particle size of aggregate, and aggregate to cement ratio. The three nominal diameters of the aggregate were 3.6 mm, 7.2 mm and 11.1 mm. The volume fraction of the binder ranged between 0.3 and 0.5, by varying the nominal diameter of the aggregate. The authors designed and cast concrete specimens with water to binder ratios (w/b) of 0.35. The authors conducted laboratory testing of mixture proportions for various properties, such as workability, unit weight, compressive strength, flexural strength, porosity and permeability. The results show that mechanical strength decreases as permeability increases. Decreasing the aggregate to the cement ratio enhances mechanical strength but may reduce permeability, and styrene-butadiene latex greatly enhances flexural strength. From an economic point of view, the authors' recommendation to achieve optimal strength and permeability in pervious concrete using recycled coarse aggregate is: w/b=0.35, nominal diameter of 11.1 mm for the recycled aggregate; the volume fraction of 0.5 for the binder; and aggregate to cement ratio of 3.9. The permeability coefficient for the above mentioned mix was 0.33 cm/sec with the 28-day compressive strength and flexural strength reaching 12.6 MPa and 2.1 MPa, respectively. The mixture for RA pervious concrete developed in this study satisfies the typical requirement for concrete sidewalks and is thus applicable for civic paving projects.

Experimental investigation on the effects of recycled aggregate on fracture behavior of polymer concrete

Abstract: The sustainable management of solid wastes stimulates metallurgic and metal mechanics industries to look for safety applications for these wastes The present paper examines the fracture behavior of polymer concrete (PC) manufactured with recycled foundry waste in substitution of fresh one The recycled foundry sand is contaminated with polymer resin from the mold making process Epoxy and unsaturated polyester resins were used as binder as cement substitute The fracture results are analyzed by fracture energy; Gf, fracture toughness, KIc, and the crack tip opening displacement, CTOD It is found that the use of recycled foundry sand significantly influences the fracture properties The use of recycled sand increase fracture toughness and similar fracture energy is observed These results show that recycled sand is an excellent alternative as raw material

Use of Recycled Aggregate and Fly Ash in Concrete Pavement

Abstract: Problem statement: Recycled materials aggregate from the demolished concrete structures and fly ash from burning coal shows the possible application as structural and non structural components in concrete structures. This research aims to evaluate the feasibility of using concrete containing recycled concrete aggregate and fly ash in concrete pavement. Approach: Two water cement ratio (0.45 and 0.55) the compressive strength, modulus of electricity and flexural strength for concrete with recycled aggregate and fly ash with 0, 25% replacing cement in mass were considered. Results: The material properties of recycled aggregate concrete with fly ash indicate comparable results with that of concrete with natural aggregate and without fly ash. Conclusion/Recommendations: The recycled materials could be used in concrete pavement and it will promote the sustainability of concrete.

Engineering properties of self-compacting rubberized concrete

Abstract: The use of rubber in self-compacting concrete is gaining more attention from the point of view of improved engineering properties of the product and also sustainability. Although several attempts h...

Design of Normal Strength Concrete Mixtures with Recycled Concrete Aggregates

Abstract: This paper investigates the design of normal strength concrete mixtures that use recycled concrete aggregates as replacement for virgin natural aggregates. Three mix design methods utilizing direct weight replacement, equivalent mortar replacement, and direct volume replacement are compared based on concrete workability, compressive strength, and elastic modulus. A total of 42 mixes were made with different aggregate replacement amounts. It was determined that the concrete workability changes significantly depending on the replacement method used, with the direct volume and equivalent mortar methods resulting in the best and worst workability, respectively. The compressive strength and elastic modulus of the mixes with recycled concrete aggregates showed little variation from concrete with natural aggregates.

Tests of Flexible Polymer Joints Repairing of Concrete Pavements and of Polymer Modified Concretes Influenced by High Deformations

Abstract: Three kinds of repair methods of cracked concrete floors are presented in the paper. One of them, based on coating using of polymer-cement composites, is discussed with presentation of the influence of different amount of styrene-butadiene co-polymer dispersion additive onto the shrinkage and strength. The next two correspond to injecting repair methods. There are also presented two different approaches in repair bonding of damaged floors. Following these ideas, results of testing of epoxy and polymer (PU) bonding of cracked specimens made of concrete and polymer-cement composites are discussed. Proposed new repair polymer flexible joints introduce energy dissipaters which allow protecting concrete pavements against large deformations. Presented comparisons of results indicate that the use of flexible polymers in repair process is efficient, what was confirmed by tests and observations of repair done at the KRK airport concrete pavement.

Tests on Cementless Alkali-Activated Slag Concrete Using Lightweight Aggregates

Abstract: Five all-lightweight alkali-activated (AA) slag concrete mixes were tested according to the variation of water content to examine the significance and limitation on the development of cementless structural concrete using lightweight aggregates. The compressive strength development rate and shrinkage strain measured from the concrete specimens were compared with empirical models proposed by ACI 209 and EC 2 for portland cement normal weight concrete. Splitting tensile strength, and moduli of elasticity and rupture were recorded and compared with design equations specified in ACI 318-08 or EC 2, and a database compiled from the present study for ordinary portland cement (OPC) lightweight concrete, wherever possible. Test results showed that the slump loss of lightweight AA slag concrete decreased with the increase of water content. In addition, the compressive strength development and different mechanical properties of lightweight AA slag concrete were comparable with those of OPC lightweight concrete and conservative comparing with predictions obtained from code provisions. Therefore, it can be proposed that the lightweight AA slag concrete is practically applicable as an environmental-friendly structural concrete.