Replacement Of Normal Aggregate Research Articles

Behavior of self-compacting concrete by the addition of recycled aggregates and nano-silica

The construction industry is growing rapidly all over the world and busy in inventing the new construction materials. The existing construction materials which are used for constructions from past decades were accumulating on the land as a waste, due to lack of reutilizing the used materials. In this experimental work, efforts were made to re-utilize the recycled aggregates which are also called demolition waste aggregates. The current study is divided into two stages. The first stage of work examines the influence of recycled aggregates on the characteristics of self-compacting concrete (SCC). The second stage includes the substitution of cement by nano silica and replacement of normal aggregates by recycled aggregates (RA) in the SCC mix. In this study, natural aggregates are replaced by 10%, 20%, 35% and 50% with recycled aggregates by the weight of total aggregates. Nano silica (NS) is used in this study, which replaces the 0.5% and 1% by weight of cement for each partial replacement level of recycled aggregates. The workability tests were performed on prepared SCC mix. The workability properties were satisfying the requirements of SCC. The compressive, split tensile and flexural strength tests were conducted on hardened concrete. The microstructural configuration of SCC containing with and without RA & NS mixtures were examined using a scanning electronic microscope (SEM). The RCPT test was conducted to understand the durability of the SCC. The outcomes of mechanical properties were optimum at 35% replacement of RA in first stage of work. Similarly, mechanical properties were optimum at 1% of NS and 35% of RA in second stage of work. The SEM analysis reveals the micro structure of mixes, the nano silica replaced concrete mix exhibit the lesser voids compared to RA replaced concrete. It results shows that voids were filled with nano particles and enhances the performance of SCC mix.

Evaluation of the Structural Performance of Low Carbon Concrete

Evaluation of the effect of embodied carbon reduction using an optimized design section for a ground beam, use of supplementary cementitious materials, and replacement of normal aggregate with light weight aggregate on the mechanical properties of low-carbon concrete was carried out. A creep coefficient of 0.019 was estimated for a 365-day period on a change in section from 1 to 0.6 m2 on a proposed trapezoidal section for ground beam, which showed a negligible difference when compared to the normal rectangular section owing to a reduction in embodied carbon due to the associated reduction in concrete volume and reinforcement. Training of 81 low-carbon concrete data sets in MATLAB using artificial neural network for 100% cement replacement with ground granular base slag indicates good performance with a mean square error of 0.856. From the study, it was observed that the extent of carbonation depth in concrete evidenced the measure of compressive strength formation based on the specific surface area of the binder and the water absorption rate of the aggregate, while enhancing the flexural strength of the low-carbon concrete required a cement-to-supplementary-cementitious-material ratio of 0.8.

THE FIRE RESISTANCE OF CONCRETE MADE WITH RECYCLED PLASTIC AS PARTIAL REPLACEMENT FOR COARSE AGGREGATE

This research is aimed to investigate the fire resistance of recycled discarded plastic when used as partial replacement for normal granite coarse aggregate in concrete when exposed to elevated temperatures. Discarded Polyethylene Terephthalate (PET) bottles were cut into a maximum size of 20mm to produce Recycled Plastic Aggregate (RPA). The replacement of normal aggregates with RPA were in proportion of 0%, 5%, 10%, 15%, 20%, 25% and 30% by weight of normal coarse aggregate. The compressive performance of the concrete made with RPA were studied by casting three 100 mm cubes for each of the percentage replacements and tested at 7, 14 and 28 days of curing age. A set of three (3) concrete cubes for each percentage replacement was cured for 28 days and subjected to a temperature of 718oC for a duration of 15 minutes in a furnace. Results of slump tests on fresh concrete showed that workability decreased with increase in RPA. Densities and compressive strengths for normal cube samples not subjected to elevated temperatures and the sample subjected to temperature of 718oC increased with increase in curing age and decreased with increase in percentage of RPA. The result showed that the concrete specimen with 10% replacement of RPA was optimum for good thermal stability.

Mechanical properties and freeze-thaw resistance of lightweight aggregate concrete using artificial clay aggregate

Abstract This work intends to make structural lightweight aggregate concrete by using artificial expanded clay aggregate with different replacement levels from normal coarse aggregate and improve it with a high-performance superplasticizer to increase its strength. The mechanical characteristics covered in the present work were compressive strength, flexural strength, and splitting tensile strength in addition to freezing and thawing resistance. Different densities were found for all mixes ranging between normal and lightweight concrete and that depends on the replacement of normal aggregate with lightweight aggregates. Mixes with replacement exceeding 25% give compressive strength less than 17 MPa and cannot be regarded as structural lightweight concrete. Modified mixes give higher values of mechanical properties, and also some non-structural lightweight concrete mixes were improved to structural lightweight concrete by using PC-superplasticizer in this study. The research also includes freezing and thawing cycles on reference mixes and lightweight mixes. Lightweight mixes give high durability against freeze-thaw cycles where the reduction in compressive strength was 6.2, 4.6, and 5.5% for 10% rep, 15% rep, and 20% rep mixes, respectively, compared with 32.2% reduction for reference mix.

Recycling of Stone Cutting Waste In the Construction Sector: A Review

Huge amounts of stone cutting waste are generated annually posing a heavy environmental load on nature and resulting in economic challenge to the plants' owners. The conducted researches in this field showed that stone, marble and granite waste could be reused in many applications. This paper aims to investigate the possible application of stone cutting waste in the construction sector. Review process includes investigation of the conducted researches, outcomes of the performed projects, and the impact of this waste on the characteristics of concrete compressive strength, flexural strength, splitting strength, concrete workability, bricks strength, terrazzo tile strength and soil properties. The results revealed that at suitable substitution ratio, this waste can increase the compressive strength of concrete up to 21%, the flexural strength by 33% and splitting strength by 4.3%. In contrast, the compressive strength of bricks decreased by up to 67% at replacement ratio of 100%, and the transverse strength of tiles decreased up to 18% at replacement ratio of 50%. Replacement of soil with stone cutting waste resulted in an improvement in the characteristics of cohesive and sandy soil. Concrete workability decreased significantly with replacement of normal aggregate with stone cutting waste. Such results buttressed the feasibility of reusing this material in the construction sector, which reduces the cost of storage and disposal, and creates a nonconventional income.

Mechanical Properties of Glass Fiber Reinforced Concrete with Recycled Aggregates

ABSTRACT Scarcity of the construction resources such as money, labour, material, land and technology is creating a big chaos and so the nations are facing problems of low GDP’s. This research focuses on reuse of laboratory waste used aggregate and studying the mechanical properties of concrete with glass fiber and varying percentages of recycled aggregates. The study focuses on use of higher percentages of recycled aggregates and analyse optimum mix that can be used for structural applications by adding glass fibers without compromising the strength parameters. The behaviour of compressive, flexural and split tensile strength of concrete using glass fibers is studied where normal aggregates are partially replaced with recycled aggregates in proportions of 40%, 60%, 70%, 80% and 100% and usage of 0.25% glass fibers as addition by weight. After analyzing results it was observed that on addition of recycled aggregates strength decreases but mix designation CR80G0.25 (80% replacement of normal aggregates with recycled aggregates and addition of 0.25% of glass fibers) has least reduction 8.23% in compressive strength. Flexural and split tensile strength shows a reduction of 2.95% and 1.76% respectively for mix designation CR70G0.25 (70% replacement of normal aggregates with recycled aggregates and addition of 0.25% of glass fibers). This shows that Mix designation CR80G0.25 can be used for compression members like columns in buildings and Mix designation CR70G0.25 can be used in construction of beams and slabs.

Ultra-violet and chemical treatment of crumb rubber aggregate in a sustainable concrete mix

ABSTRACTThis paper illustrates the usage of crumb rubber as a recycled aggregate in concrete. However, the presence of crumb rubber leads to a lower concrete compressive strength primarily due to its much lower stiffness. Under stress, the rubber deforms, re-distributing the load to the cement paste, which subsequently fails prematurely. Instead of reverting to conventional methods of increasing concrete compressive strength, such as lowering the water cement ratio facilitated through the addition of a superplasticiser or enhancing the binder effectiveness with the addition of silica fume, this paper will focus on some of the pre-treatment methods on crumb rubber that can help mitigate this loss of strength. These include accelerated aging and stiffening crumb rubber through exposing it to ultraviolet light to enhance its surface roughness characteristics or pre-treating crumb rubber by soaking it in sulphuric acid to develop a stiffer surface layer. By increasing the rubber’s stiffness, it is observed that its load share increases, thereby improving the crumb rubber concrete’s compressive strength and allowing a larger dosage replacement of normal aggregate without significant strength loss. In summary, identifying whether or not different pre-treatment of the crumb rubber aggregates are successful in avoiding a substantial loss in strength consequent upon its inclusion in concrete is the primary objective of this paper.

Effects of partial replacement of normal aggregates with lateritic stone in concrete

: Lateritic stones abound in the tropical and semi tropical areas of the world more than the igneous and other standard rocks that are used as concrete aggregates and road chippings. The increasing utilization of natural aggregate for concrete production have created negative impact on the environment. Therefore searching for alternative material which has potential to replace the use of coarse aggregate from normalrocks in concrete mix either wholly or partially is very much in need. This research presents the engineering properties of concrete containing lateritic aggregate as partial coarse aggregate replacement. The coarse aggregate was replaced by 10, 20, 30, 40 and 50% with lateritic aggregate. All the specimens were cured and compressive strength test were carried out at the age of 7, 14, 21 and 28 days respectively. The result revealed that replacement of lateritic aggregate up to 30% was able to produce lateritic concrete exhibiting the target strength which is 30 N/mm2. However, the slump decreases as the percentage of lateritic aggregate in the mix increases, this may be due to the porosity of the lateritic aggregate due to absorption of the water in the mix. The result of the two way analysis of variance shows that both lateritic aggregate and curing age (days) has significant effects of the compressive strength of concrete. Keywords : Lateritic stone, Cement, Concrete, Compressive strength

Energy Absorption Capacity Of Layered Lightweight Reinforced Concrete Beams With Openings In Web

This research presents the flexural behavior on reinforced concrete beam with transverse web opening constructed from layered concrete. The layered concrete combining normal concrete and lightweight aggregate concrete (LWC) are depended in present study. In the experimental program, 13 models of normal and layered reinforced concrete beams are tested under the effect of four-point loads. All beams had the same overall geometrical dimensions and main longitudinal top and bottom with internal diagonal reinforcement provided around the openings. One of the beam specimen is tested as control beam and the other specimens are divided into three groups [G1, G2, and G3] to study the effects of the following variables: effect of presence of web openings, layered system, lightweight aggregate (partially volumetric replacement of normal aggregate by thermostone) on the ultimate load, cracking load, cracking pattern and energy absorption capacity. The existing of an opening in beam specimens reduced the flexural capacity of beams with a percentage depending on the size of opening and opening number. The test data obtained from the adopted layered technique of (NEW) and (LWC) have shown that for beams constructed from two layered concrete (LWC with thermostone in the web and bottom flange of I-beam section) ultimate load is decreased about (9.3%-48.8%). It has also, the beams constructed from three-layered of concrete (LWC with thermostone in the web of I-beam section), their ultimate load is decreased about (25.6%-58.1%). On the other hand, magnitude increased of energy absorption capacity are achieved by the decreased opening size, introducing the full size opening of dimension (100×1000) mm reduces the energy absorption capacity of the RC I-section beams at least 80% compared to solid beam while the beam with opening size (100×100) mm decrease up to 16%. In the case of the layered concrete beams specimen, the real influence of lightweight concrete (LWC) type in the layered reinforced concrete is observed significantly after increasing the length of opening more than 100 mm.

Properties of structural lightweight concrete containing treated oil palm shell as coarse aggregate

One way of attaining sustainable and environment friendly structures is to use industrial waste as construction material. Oil palm boiler clinker obtained from palm oil extraction process in palm oil industry is a promising material which can be used for replacement of coarse aggregate in concrete. In this study, development of water absorption rate in oil palm shell is modified with water-repellent admixture to maintain the mechanical properties as same as normal weight concrete (NWC). These oil palm shells are lightweight and can be used as coarse aggregate for structural application in construction structures. The physical and chemical properties of such aggregate are evaluated and improved for those parameters which are deficient to produce good quality concrete. Internal curing of concrete takes place when treated oil palm shell is used as lightweight aggregate which is an added advantage for durable concrete. Properties like sorptivity, density, compressive strength were measured and discussed. Results show that replacement of normal aggregate with industrial waste product is structurally good and environmental friendly, compression strength ranging from 25 to 30 MPa which is same in case of NWC.

Properties of rubberized concrete modified by using silane coupling agent and carboxylated SBR

Using waste rubbers as aggregates in concrete is a feasible approach to recycle the material. However, due to the poor adhesion of rubber to cement paste, the replacement of normal aggregate with rubber will lead to a reduction in the mechanical strength of concrete. This paper presents a new approach to overcome this deficiency by treating waste rubbers with silane coupling agent (SCA) and carboxylated styrene–butadiene rubber (CSBR) latex to develop chemical bonds between rubbers and cement paste. This study investigates the influence of this surface treatment on the mechanical strength and chloride penetration resistance of rubberized concrete. Experiments were conducted with six different volume fractions of rubbers (between 0% and 30%) to replace fine aggregate in the concrete. The experimental results showed that the compressive strength and flexural strength of concretes incorporating proper amount of treated rubbers could be improved by 4% and 13% respectively as compared to the control concrete with no rubbers. Moreover, the chloride penetration resistance was also improved by 35%. The good adhesion of waste rubbers to cement paste, the formation of rubber networks and the embedding effect of rubbers as shown in SEM images are explanations for the enhancement in the mechanical strength and durability for the treated rubber concrete.