Environmentally Friendly Pervious Concrete for Treating Deicer-Laden Stormwater: Phase I

A graphene oxide-modified pervious concrete was developed by using low-reactivity, high-calcium fly ash as sole binder and chemical activators and other admixtures. The density, void ratio, mechanical strength, infiltration rate, Young’s modulus, freeze-deicer salt scaling, and degradation resistance of this pervious concrete were measured against three control groups. The test results indicate that graphene oxide modified fly ash pervious concrete is comparable to Portland cement pervious concrete. While the addition of 0.03% graphene oxide (by weight of fly ash) noticeably increased the compressive strength, split tensile strength, Young’s modulus, freeze-deicer salt scaling, and degradation resistance of fly ash pervious concrete, it reduced the void ratio and infiltration rate. The fly ash pervious concrete also showed unfavorable high initial loss during the freeze-deicer salt scaling test, which may be attributed to the low hydration degree of fly ash at early age. It is recommended that durability tests for fly ash concrete be performed at a later age

Durability and Smart Condition Assessment of Ultra-High Performance Concrete in Cold Climates

The goals of this study were to develop ecological ultra-high performance concrete (UHPC) with local materials and supplementary cementitious materials and to evaluate the long-term performance of UHPC in cold climates using effective mechanical test methods, such as “smart aggregate” technology and microstructure imaging analysis. The optimal UHPC mixture approximately exhibited compressive strength of 15 ksi, elastic modulus of 5,000 ksi, direct tensile strength of 1.27 ksi, and shrinkage of 630 at 28 days, which are characteristics comparable to those of commercial products and other studies. The tensile strength and modulus of elasticity in tension, dynamic modulus, and wave modulus show slight increases from the original values after 300 freeze-thaw (F-T) cycles, indicating that UHPC has excellent frost resistance in cold climates. Although porosity deterioration was observed in the F-T cyclic conditioning process, no internal damage (cracks or fractures) was found during imaging analysis up to 300 cycles. Since structures for which UHPC would be used are expected to have a longer service life, more F-T cycles are recommended to condition UHPC and investigate its mechanical performance over time. Moreover, continuum damage mechanic-based models have the potential to evaluate damage accumulation in UHPC and its failure mechanism under frost attack and to predict long-term material deterioration and service life

Assessment of Strength Characteristics of Concrete Made from Locally Sourced Gravel Aggregate from South-South Nigeria

Aims: The aim of this research is to verify the suitability of local gravel aggregates obtained from the Southern part of Akwa Ibom State for designed concrete production in place of crushed granite aggregate sourced from distance places at exorbitant cost. This paper assesses the strength characteristics of concrete made from two locally sourced gravel aggregates of 10 mm and 20 mm maximum sizes. Study Design: Three samples of gravels divided into washed and unwashed gravels were used for the research. Concrete mix design of 25 N/mm2 at 28 days of curing was the target mean strength of the research. Place and Duration of Study: Department of Civil Engineering, Covenant University, Ota – Nigeria, between September 2014 and July 2015. Methodology: Particle size distribution test, specific gravity test, water absorption test, aggregate crushing value test, flakiness and elongation tests, slump test, compressive strength test were performed on the samples. Concrete cubes150 mm were cast for each gravel size and three specimen tested for 3, 7, 14, 21 and 28 days compressive strength. Results: The washed gravels with 10 mm and 20 mm maximum size reached the target mean strength with 29.7 N/mm2 and 26.2 N/mm2 respectively while the unwashed gravel with 20 mm maximum size yielded a compressive strength of 24.5 N/mm2 at 28 days. Conclusion: The results prove that the size, grading, internal bonding and deleterious material contribute immensely to the strength of concrete made from gravel aggregate

Expanded Fly Ash Clay Aggregate a Sustainable Alternative Coarse Aggregate for Concrete

Demand for natural aggregates in making concrete is increasing every day. Concrete is widely used in turnkey projects and small-scale projects. An alternative sustainable coarse aggregate for natural coarse aggregate can reduce the amount of pollution and preserve natural resource. An attempt is made in this research project to use locally available soil from the site and fly ash waste to prepare an alternative sustainable coarse aggregate for concrete to be used in small constructions. Concrete mix is prepared with natural aggregate and expanded fly ash clay aggregate EFCA and their fresh state, strength and durability properties were studied. The slump value of EFCA concrete under same water content is similar to that of natural aggregate concrete. A compressive strength of 21.45 MPa is achieved for EFCA concrete, which is acceptable for normal structural concrete. Flexural strength of 3.67 MPa is measured. Rapid chloride penetration test conducted on EFCA concrete showed moderate resistance to sulfate attack and a higher water penetration

Laboratory investigation on utilization of recycled materials in SMA mix

SMA (stone matrix asphalt or stone mastic asphalt) was originally developed in European and German countries as impervious or highly durable wearing surface for bridge decks. But today, it is pavement surface of choice. Generally it consists of two parts, a coarse aggregate and a binder rich mortar. It is made by a mixture of crushed coarse and fine aggregates, stabilizer such as fibres or polymers, mineral filler, cement. In present research work, an attempt has been made to study the properties of SMA mixes with cellulose fibre and using recycled pavement material as well as slag in partial replacement of stone aggregates as coarse and fine aggregate grades. This research project was done to check the usage of recycled pavement material in SMA mixture by conducting Marshall test in the laboratory in which stability value and flow values was examined along with other properties of mixtures. Here IRC -SP-79 specification, aggregate gradation is taken for stone matrix asphalt. Binder used is 60/70 penetration grade bitumen. Binder content is varied as 4%, 5%, 5.5%, 6%, and 7% by weight of aggregates and fibre used is optimum fibre content at 0.3% by weight of aggregate

Evaluating potential of diatomite as anti clogging agent for porous asphalt mixture

Clogging is a major problem that occurs throughout the service life of porous asphalt due to the open nature of the mixture itself. Diatomite with characteristic of abrasiveness and porous structure seems to have potential in order to remove the clogging materials that mainly consists of soils. This study aims to investigate the effects of diatomite as anti-clogging agent on the permeability rate and strength of porous asphalt. The porous asphalt samples were prepared using Malaysia aggregate gradation and polymer modified bitumen of PG76 was used as the binder. This study focuses on clay as the clogging material at different concentration. A fixed amount of 0.5 g/L diatomite was applied to the porous asphalt samples as an anti-clogging agent prior to clogging cycles. The permeability test and resilient modulus were then conducted at different clogging concentrations (0.5, 1.0, 1.5 g/L) and cycles, with and without diatomite. It was found that samples with diatomite have a higher permeability rate compared to those without any application of diatomite after a few clogging cycles. As the clogging cycles increase, the clogging materials have trapped and filled up the voids in the porous asphalt samples and increase the resilient modulus result

Treatment of end-of-life concrete in an innovative heating-air classification system for circular cement-based products

A stronger commitment towards Green Building and circular economy, in response to environmental concerns and economic trends, is evident in modern industrial cement and concrete production processes. The critical demand for an overall reduction in the environmental impact of the construction sector can be met through the consumption of high-grade supplementary raw materials. Advanced solutions are under development in current research activities that will be capable of up-cycling larger quantities of valuable raw materials from the fine fractions of End-of-Life (EoL) concrete waste. New technology, in particular the Heating-Air classification System (HAS), simultaneously applies a combination of heating and separation processes within a fluidized bed-like chamber under controlled temperatures (±600 °C) and treatment times (25–40 s). In that process, moisture and contaminants are removed from the EoL fine concrete aggregates (0–4 mm), yielding improved fine fractions, and ultrafine recycled concrete particles (<0.125 mm), consisting mainly of hydrated cement, thereby adding value to finer EoL concrete fractions. In this study, two types of ultrafine recycled concrete (either siliceous or limestone EoL concrete waste) are treated in a pilot HAS technology for their conversion into Supplementary Cementitious Material (SCM). The physico-chemical effect of the ultrafine recycled concrete particles and their potential use as SCM in new cement-based products is assessed by employing substitutions of up to 10% of the conventional binder. The environmental viability of their use as SCM is then evaluated in a Life Cycle Assessment (LCA). The results demonstrated accelerated hydration kinetics of the mortars that incorporated these SCMs at early ages and higher mechanical strengths at all curing ages. Optimal substitutions were established at 5%. The results suggested that the overall environmental impact could be reduced by up to 5% when employing the ultrafine recycled concrete particles as SCM in circular cement-based products, reducing greenhouse gas emissions by as much as 41 kg CO2 eq./ton of cement (i.e. 80 million tons CO2 eq./year). Finally, the environmental impacts were reduced even further by running the HAS on biofuel rather than fossil fuel.The authors of the present paper, prepared in the framework ofthe Project VEEP "Cost-Effective Recycling of C&DW in High AddedValue Energy Efficient Prefabricated Concrete Components forMassive Retrofitting of our Built Environment", wish to acknowl-edge the European Commission for its support. This project hasreceived funding from the European Union’s Horizon 2020 researchand innovation programme under grant agreement No 723582.This paper reflects only the author’s view and the European Com-mission is not responsible for any use that may be made of theinformation it contains.The authors are also grateful to the Spanish Ministry of Science,Innovation and Universities (MICIU) and the European RegionalDevelopment Fund (FEDER) for funding this line of research(RTI2018-097074-B-C21)

Fresh and mechanical properties of self compacting concrete containing copper slag as fine aggregates

An investigation is carried out on the development of Self Compacting Concrete (SCC) using copper slag (CS) as fine aggregates with partial and full replacement of sand. Six different SCC mixes (60% OPC and 40% Fly Ash) with 0% as control mix, 20%, 40%, 60%, 80% and 100% of copper slag substituting sand with constant w/b ratio of 0.45 were cast and tested for fresh properties of SCC. Compressive strength and splitting tensile strength were evaluated at different ages and microstructural analysis was observed at 120 days. It has been observed that the fluidity of SCC mixes was significantly enhanced with the increment of copper slag. The test results showed that the compressive strength increases up to 60% copper slag as replacement of sand, beyond which decrease in strength was observed. The highest compressive strength was obtained at 20% copper slag substitution at different curing ages among all the mixes, except for 7 days curing. The splitting tensile strength of the CS substituted mixes in comparison to control concrete was found to increase at all the curing ages but the remarkable achievement of strength was detected at 60% copper slag replacement. The microscopic view from Scanning electron microscopy (SEM) demonstrated more voids, capillary channels, and micro cracks with the increment of copper slag as substitution of sand as compared to the control mix