Strength and durability of low-impact environmental self-compacting concrete incorporating waste marble powder

This research studies the effect of waste marble powder (WMP) as substitute of Portland cement on strength and durability of self-compacting concrete (SCC) in order to produce SCC with reduced impact environmental. For this purpose, five mixtures were designed in which four mixtures contained WMP at substitution levels of 5, 10, 15, 20%, and mixture included only the Portland cement as control mix. The realized tests are compressive strength at 3, 7 and 28 days, water capillary absorption, water absorption by immersion and sulfate attack. The results show a reduction in the compressive strength with increasing WMP content. The use of WMP was found to increase both of the water capillary absorption and water absorption by immersion. SCC containing WMP subjected to magnesium sulfate attack presented a lower expansion and higher resistance to sulfate aggressions

Experimental and numerical study of behaviour of reinforced masonry walls with NSM CFRP strips subjected to combined loads

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).Near surface mounted (NSM) carbon fibers reinforced polymer (CFRP) reinforcement is one of the techniques for reinforcing masonry structures and is considered to provide significant advantages. This paper is composed of two parts. The first part presents the experimental study of brick masonry walls reinforced with NSM CFRP strips under combined shear-compression loads. Masonry walls have been tested under vertical compression, with different bed joint orientations 90ffi and 45ffi relative to the loading direction. Different reinforcement orientations were used including vertical, horizontal, and a combination of both sides of the wall. The second part of this paper comprises a numerical analysis of unreinforced brick masonry (URM) walls using the detailed micro-modelling approach (DMM) by means of ABAQUS software. In this analysis, the non-linearity behavior of brick and mortar was simulated using the concrete damaged plasticity (CDP) constitutive laws. The results proved that the application of the NSM-CFRP strips on the masonry wall influences significantly strength, ductility, and post-peak behavior, as well as changing the failure modes. The adopted DMM model provides a good interface to predict the post peak behavior and failure mode of unreinforced brick masonry walls.Peer reviewe

Effect of limestone powder as a partial replacement of crushed quarry sand on properties of self-compacting repair mortars

Self-compacting repair mortars (SCRM) are particularly desired for the rehabilitation and repair of reinforced concrete structures. The properties of SCRM can be improved by using chemical, mineral, polymer and fiber additives. In limestone quarries, considerable quantities of limestone fine powder are obtained during the process of crushing rock. These fine powders are being collected and their utilization is a big problem from the aspects of disposal, environmental pollution and health hazards. The introduction of limestone powder as cement and sand replacement present interesting possibilities to reduce the cement cost production, CO2 emission and the conservation of natural resources. The effects of limestone powder content in crushed sand on the properties of SCRM are not studied. An experimental study was undertaken to find out the effect of limestone powder content on fresh and hardened properties of SCRM. SCRM mixtures were prepared using crushed sand partially replaced with limestone powder at varying percentages up to 30%. Results indicate that the limestone powder as sand replacement significantly improves the fresh and hardened properties of SCRM with a content ranging from 10 to 15%. The use of limestone powder in repair mortar and concrete application would offer technical, economical and environmental advantages for concrete producers.Self-compacting repair mortars (SCRM) are particularly desired for the rehabilitation and repair of reinforced concrete structures. The properties of SCRM can be improved by using chemical, mineral, polymer and fiber additives. In limestone quarries, considerable quantities of limestone fine powder are obtained during the process of crushing rock. These fine powders are being collected and their utilization is a big problem from the aspects of disposal, environmental pollution and health hazards. The introduction of limestone powder as cement and sand replacement present interesting possibilities to reduce the cement cost production, CO2 emission and the conservation of natural resources. The effects of limestone powder content in crushed sand on the properties of SCRM are not studied. An experimental study was undertaken to find out the effect of limestone powder content on fresh and hardened properties of SCRM. SCRM mixtures were prepared using crushed sand partially replaced with limestone powder at varying percentages up to 30%. Results indicate that the limestone powder as sand replacement significantly improves the fresh and hardened properties of SCRM with a content ranging from 10 to 15%. The use of limestone powder in repair mortar and concrete application would offer technical, economical and environmental advantages for concrete producers.Self-compacting repair mortars (SCRM) are particularly desired for the rehabilitation and repair of reinforced concrete structures. The properties of SCRM can be improved by using chemical, mineral, polymer and fiber additives. In limestone quarries, considerable quantities of limestone fine powder are obtained during the process of crushing rock. These fine powders are being collected and their utilization is a big problem from the aspects of disposal, environmental pollution and health hazards. The introduction of limestone powder as cement and sand replacement present interesting possibilities to reduce the cement cost production, CO2 emission and the conservation of natural resources. The effects of limestone powder content in crushed sand on the properties of SCRM are not studied. An experimental study was undertaken to find out the effect of limestone powder content on fresh and hardened properties of SCRM. SCRM mixtures were prepared using crushed sand partially replaced with limestone powder at varying percentages up to 30%. Results indicate that the limestone powder as sand replacement significantly improves the fresh and hardened properties of SCRM with a content ranging from 10 to 15%. The use of limestone powder in repair mortar and concrete application would offer technical, economical and environmental advantages for concrete producers

Effect of limestone powder as a partial replacement of crushed quarry sand on properties of self-compacting repair mortars

Self-compacting repair mortars (SCRM) are particularly desired for the rehabilitation and repair of reinforced concrete structures. The properties of SCRM can be improved by using chemical, mineral, polymer and fiber additives. In limestone quarries, considerable quantities of limestone fine powder are obtained during the process of crushing rock. These fine powders are being collected and their utilization is a big problem from the aspects of disposal, environmental pollution and health hazards. The introduction of limestone powder as cement and sand replacement present interesting possibilities to reduce the cement cost production, CO2 emission and the conservation of natural resources. The effects of limestone powder content in crushed sand on the properties of SCRM are not studied. An experimental study was undertaken to find out the effect of limestone powder content on fresh and hardened properties of SCRM. SCRM mixtures were prepared using crushed sand partially replaced with limestone powder at varying percentages up to 30%. Results indicate that the limestone powder as sand replacement significantly improves the fresh and hardened properties of SCRM with a content ranging from 10 to 15%. The use of limestone powder in repair mortar and concrete application would offer technical, economical and environmental advantages for concrete producers

Experimental study on the reuse of cathode ray tubes funnel glass as fine aggregate for developing an ecological self-compacting mortar incorporating metakaolin

Industrial waste causes a lot of pollution, particularly electrical and electronic waste (WEEE) such as glass cathode ray tubes (CRT) which create environmental pollution and health hazards. The field of civil engineering, like sectors in the world has leaned towards sustainable development by emphasizing environmental aspects as an important goal. This strategy is achieved by recycling and reusing polluted industrial sites, materials, waste, by-products or industrial residues. In this paper a study was carried out to explore the use of recycling waste glass obtained from crushed CRT as fine aggregate, and metakaolin (MK), as a partial replacement of Ordinary Portland cement (OPC) for the development of eco-self-compacting mortar (SCM). Here, OPC is replaced by 5, 10, and 15% of MK by weight, and fine aggregate is replaced by 0, 10, 20, 30, 40 and 50% of CRT by weight. The mini-slump flow and V-funnel flow time of fresh SCM are evaluated. The compressive strength, flexural strength, water absorption, resistance to high temperature, porosity and microstructure of hardened SCM are also performed. These experiments indicate that using CRT glass with MK increases the flowability of SCM and reduces the dosage of superplasticizer (SP). The incorporation of 10% MK with CRT mixture showed higher mechanical properties, lower porosity and dense structure. Moreover, the water absorption and resistance to high temperature have been improved by 10% and 15% of the MK group respectively, for all SCM made with CRT glass. This combination of MK and CRT glass as a fine aggregate in SCM is a low-cost ecosystem for a much cleaner environment

Effect of using metakaolin as supplementary cementitious material and recycled CRT funnel glass as fine aggregate on the durability of green self-compacting concrete

This present work is a study of the durability of green self-compacting concrete (SCC) that incorporates recycled cathode ray tube glass (CRTG) and metakaolin (MK). In these SCC mixtures natural sand has been replaced with CRTG at levels of 0, 10, 20, 30, 40 and 50% by weight, and the cement has been partially replaced by MK at substitution ratios of 5, 10, and 15% by weight. The fresh properties of SCC mixtures were then evaluated by slump flow, V-funnel, L-Box tests and their resistance to segregation was measured by the sieve stability test. The strength and durability properties of hardened SCC mixtures was assessed according to the compressive strength, ultrasonic pulse velocity (UPV), porosity, ions chloride permeability, gas permeability, and Alkali-silica reaction (ASR) tests. A SEM analysis was also carried out to examine the developing microstructure of hardened SCC mixtures. This study revealed an improvement in the fresh properties of SCC mixtures with up to 50% CRTG replacement. At the hardened state, the compressive strength and UPV of the SCC mixtures (10MK + 50CRTG) improved by 16% and 3% respectively after 90 days of ageing compared to SCC control mixtures. Moreover, using MK in SCC mixtures with different amounts of CRTG resulted in the best durability, while 10% of MK enhanced the porosity, permeability of chloride and gas permeability in SCC. Results show also that, 10% and 15% of MK can be prescribed in 0.1% limit of ASR in SCC mixtures with CRTG

Characteristics, strength development and microstructure of cement mortar containing oil-contaminated sand

The application of oil-contaminated sand (OCS) in concrete is considered a highly sustainable solution and cost-effective recycling method for minimising its negative effect to the environment. The present study investigated the mechanical characteristics, strength development, hydration and microstructure of cement mortar containing oil-contaminated sand. The parameters investigated in the present study are the level of oil contamination, mixing method, water-to-cement (w/c) ratio, and the age of curing. The microstructural characteristics of hardened samples, physical and mechanical properties and the strength development pattern of cement mortar containing oil-contaminated sand were assessed up to 365 days. Result shows that the presence of crude oil up to 4% can improve the properties of mortar compare to the uncontaminated samples. The mixing of water and cement before adding oil-contaminated sand is found effective method of mixing, while the optimum compressive strength obtained at a w/c ratio of 0.5. The strength of cement-based mortar having contaminated sand with 2% light crude-oil is similar to the cement mortar with uncontaminated sand after one year. However, the rate of gaining strength of cement mortar with high levels of contamination with light crude oil (4–10%) is found slow. The microstructure of mortar containing contaminated fine sand up to 2% oil appeared to be quite dense and have a finer pore structure. The interfacial tension zone (ITZ) is not affected by crude oil up to 2%, however, the higher percentages of oil contamination (6–10%) can increase the porosity and affect the ITZ

Potential pozzolanicity of Algerian calcined bentonite used as cement replacement: optimisation of calcination temperature and effect on strength of self-compacting mortars

The effect of using calcined bentonite (CB) as a partial replacement for Ordinary Portland cement (OPC) in self-compacting mortar (SCM) is investigated. The pozzolanicity of this calcined clay is evaluated using the strength activity index and TG/ATD analysis. The cement in SCM has been replaced with CB at 0, 5, 10, 15, 20, 25 and 30% by mass of cement. The effect of CB on fresh SCM properties is examined using mini-slump flow and V-funnel flow time. The compressive strength is determined at the age of 3, 7 and 28days, and the ultrasonic pulse velocity (UPV), hardened density and water absorption are determined at the age of 28days. The behaviour of SCM exposed to high temperature is also studied. The results indicate that CB significantly decreased the flowability of SCM, but these results are good enough for SCM and SCC production. Incorporating 10 and 15% of CB improves the compressive strength and UPV. Water absorption tends to increase slightly with an increase in CB content and there is a decrease in density as the amount of CB increases. SCM containing CB is stronger when exposed to high temperature than those exposed to normal temperature (23C)

Experimental Research and Numerical Analysis of CFRP Retrofitted Masonry Triplets under Shear Loading

This paper presents an experimental and numerical study into the shear response of brick masonry triplet prisms under different levels of precompression, as well as samples reinforced with carbon fiber-reinforced polymer (CFRP) strips. Masonry triplets were constructed with two different mortar mix ratios (1:1:3 and 1:1:5). In this study, finite element models for the analysis of shear triplets are developed using detailed micro-modelling (DMM) approach and validated with the experimental data. The failure mechanisms observed in the masonry triplets were simulated using a coupled XFEM-cohesive behaviour approach in ABAQUS finite element software. The nonlinear behaviour of mortar and brick was simulated using the concrete damaged plasticity (CDP) constitutive laws. The cohesive element with zero thicknesses was employed to simulate the behaviour of the unit–mortar interfaces. The extended finite element method (XFEM) was employed to simulate the crack propagation in the mortar layer without an initial definition of crack location. CFRP strips were simulated by 3D shell elements and connected to masonry elements by an interface model. The changes in failure mechanism and shear strength are calculated for varying types of mortar and fiber orientation of CFRP composite. Based on this study, it was concluded that the ultimate shear strength of masonry triplets is increased due to the external bonding of CFRP strips. The performance of masonry specimens strengthened with CFRP strips is assessed in terms of gain in shear strength and post-peak behaviour for all configurations and types of mortar considered. The comparison of FE and experimental results proved that the models have the potential to be used in practice to accurately predict the shear strength and reflect damage progression in unreinforced and CFRP-reinforced masonry triplets under in-plane loading, including the debonding of the CFRP reinforcement. Additionally, XFEM was found to be a powerful technique to be used for the location of crack initiation and crack propagation in the mortar layer

Rheology and strength of concrete made with recycled concrete aggregates as replacement of natural aggregates

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