Concrete with ceramic waste aggregate

Use of hazardous industrial wastes in concrete-making will lead to greener environment. In ceramic industry about 30% production goes as waste, which is not recycled at present. In this study an attempt has been made to find the suitability of the ceramic industrial wastes as a possible substitute for conventional crushed stone coarse aggregate. Experiments were carried out to determine the compressive, splitting tensile and flexural strengths and the modulus of elasticity of concrete with ceramic waste coarse aggregate and to compare them with those of conventional concrete made with crushed stone coarse aggregate. The properties of the aggregates were also compared. Test results indicate that the workability of ceramic waste coarse aggregate concrete is good and the strength characteristics are comparable to those of the conventional concrete.     

Influence of fired clay brick waste additions on the durability of mortars

The use of metakaolin is known to help improve properties of Portland cement-based mortars. The presumed similarities between the characteristics of metakaolin and those of a powdered (<45 μm) fired clay brick clean waste (CBW) led to the investigation of the effect on the durability of mortars of partial replacement (10, 25 and 40 wt.%) of Portland cement by CBW. Properties such as 28 and 90 days-compressive strength, water absorption, apparent porosity, absorption by capillarity, chloride retention, carbonation depth and sulphate resistance were evaluated. The CBW-containing cured mortars showed improved strength and density, as the result of combined physical and pozzolanic pore filling effect of added CBW. However, CBW-free mortar exhibited larger spreading and, being more porous, higher sulphate resistance and ability to absorb chlorides. Optimum performance was found for the 40 wt.% CBW mortar whose compressive strength can be up to 130% higher than that of the CBW-free mortar.     

Performance of mortars containing recycled fine aggregate from construction and demolition waste

Waste from construction and demolition accumulates in large quantities in the modern world. Recycled coarse aggregates derived from this waste can replace virgin aggregates used in the production of new concretes but the studies on the effect of using the fine fraction of this waste on the properties of new concrete have not yet led to clear conclusions. The present study evaluated the properties of recycled fine aggregates derived from two recycling plants using two different waste treatment procedures, as well as their effects on the properties of fresh and hardened mortars prepared using these aggregates at two water-to-cement ratios and three replacement ratios. It was found that the recycled aggregates were more porous than the natural aggregates and may have contained some organic matter. Setting times were longer when recycled aggregates replaced natural aggregates and strength and durability were reduced as well. Partial replacement of the fine aggregate is possible if an appropriate compensation of the water to cement ratio is applied.     

Investigation on partially replacing metakaolin with marine shell waste to produce sustainable eco-friendly geopolymer mortars

Clean Technologies and Environmental Policy - This work focuses on the effect of the incorporation of marine shell waste in different mass substitution rates in geopolymer mortars as an efficient...     

Reuse of sanitary ceramic wastes as coarse aggregate in eco-efficient concretes

The sanitary ceramics industry inevitably generates wastes, irrespective of the improvements introduced in manufacturing processes. The present study investigated the reuse of these wastes as recycled coarse aggregate in partial substitution (15%, 20% and 25%) of natural coarse aggregates in the manufacture of structural concretes. The results demonstrate that recycled, eco-efficient concretes present superior mechanical behaviour compared to conventional concrete and it was moreover appreciated that the recycled ceramic aggregate does not interfere in a negative way during the hydration process. It was also observed that the microstructure in the interfacial transition zone (ITZ) between recycled ceramic aggregate and paste was more compact than in the case of natural aggregate and paste.     

The effect of recycled plastic aggregate on chemico-physical and functional properties of composite mortars

In this paper the interaction mechanism between recycled plastic aggregates and lime matrix in composite mortars was investigated by means of thermal, morphological and Fourier Transform Infrared Spectroscopy (FTIR) analyses. In order to assess the fire behavior of the composite mortars, a cone calorimeter method was adopted. The plastic aggregate, mainly made of polyolefin and polyethylene terephthalate, is obtained from an industrial waste, through a process that provides a plasticization and densification by extrusion of plastic waste. Several composite mortars were prepared by replacing silica powder with 10%, 15% and 20% of recycled aggregate. Experimental results attest that, even if the filler was not chemically modified, there is a good chemical interaction between the plastic aggregate and mortar, involving a reduction of the negative effects on physical and functional properties of the mortar composites, such as thermal degradation and fire resistance. In fact all the specimens showed a scarce sensitivity to flashover, and can be classified as low risk materials.     

生活污水的厌氧处理及应用效果分析

应用户用沼气池厌氧发酵原理,通过发酵流程技术改进后对公厕污水进行生物降解处理和物理沉淀截流辅助处理,经检测污水排放指标达到GB8978-88《污水综合排放标准》的Ⅱ级标准,从而提高了水源质量。其实用效果显著,并分析和讨论相关的技术问题。     

Fine ceramics replacing cement in mortars Partial replacement of cement with fine ceramics in rendering mortars

The main objective of the use of very fine red clay ceramic waste in rendering mortars is the reduction in the primary binder (cement) content made possible by the potential pozzolanic effect of this recycled material, with very clear environmental benefits in the reduction of overly-high energy consuming cement and economic benefits in the potential reduction of the cost of mortars. This paper presents an experimental program where ceramic waste crushed to very fine particles was used to partially replace cement in mortars manufacturing, acting as a secondary binder. A large number of tests of the most relevant characteristics of various mortars in which this principle was applied were performed and compared with the results of the same tests in a reference rendering mortar with no ceramic fines (and no reduction of the cement content). The results are most promising both from a performance-based and an environmental point of view.     

Efficiency of ground granulated blast-furnace slag replacement in ceramic waste aggregate mortar

From our previous findings, the recycling of ceramic waste aggregate (CWA) in mortar has been proved an ecological means plus an excellent outcome against chloride ingress. The CWAs were porcelain insulator wastes supplied from an electric power company, which were crushed and ground to fine aggregate sizes. In this study, to further develop the CWA mortar as an eco-efficient construction material, ground granulated blast-furnace slag (GGBS) was incorporated. The slag (having the Blaine fineness of 6230 cm²/g) was utilized as a supplementary cementitious material (SCM) at three different replacement levels of 15%, 30%, and 45% of cement by weight. The efficiency of the GGBS on enhancing chloride resistance in the CWA mortars was experimentally assessed by using a silver nitrate solution spray method and an electron probe microanalysis (EPMA). The tests were carried out on mortar samples after immersed in a 5.0% NaCl solution for 24 weeks. Another set of the mortar samples was exposed to a laboratory ambient condition for 24 weeks and then followed with a carbonation test. The test results indicated that the resistance to the chloride ingress of the CWA mortar becomes more effective in proportion to the replacement level of the GGBS. In contrast, the carbonation depth of the CWA mortar increases with the increase of the GGBS. The activeness of the GGBS was also evaluated on the basis of the compressive strength development up to 91 days. Due to its high fineness, the GGBS can be used up to 30% while the high relative strength (more than 1.0) is achieved at all ages.     

Investigation on the effects of polymer impregnated aggregate on polymer mortars properties

The sustainable management of solid wastes stimulates metallurgic and metal mechanics industries to look for safety applications for such wastes. The present paper examines the mechanical properties, compressive and flexural strength, of polymer mortars (PM) made with spent foundry waste, i.e., polymer impregnated foundry sand as aggregate, and presents a comparison with specimens made with fresh sand. The foundry sand is contaminated with alkaline-phenolic resin from the mould making process. PM consists of mineral filler and a polymer binder, which is normally a thermosetting resin. Polyester recycled from PET and epoxy resins are used as binders. It is found that the recycled sand does influence the mechanical properties, i.e., the polymer mortars made with recycled sand presents a decrease in mechanical characteristics of polymer mortars. Environmental acceptance of foundry sands requires reliable knowledge of sand composition and sand residue composition variations, especially regarding their environmental characteristics.     

The influence of superabsorbent polymers on strength and durability properties of blended cement mortars

The effect of different quantities of admixed superabsorbent polymers (SAP) on durability and strength properties of normal strength mortars containing various binary cement blends was investigated. Addition of SAP did not significantly affect compressive strength, although a slight retardation of strength development was observed in mortars with higher w/b ratio. Tensile strength values were generally slightly improved with the use of SAP. Durability was assessed by measuring porosity, oxygen permeability, chloride conductivity, accelerated carbonation, and bulk diffusion. The generally improved durability properties, especially for mortars containing silica fume, indicates the potential to use SAP to design high quality concrete repair mortars.     

Utilization of ceramic waste as fine aggregate within Portland cement and fly ash concretes

The aim of this research work was to investigate the feasibility of using ceramic waste and fly ash to produce mortar and concrete. Ceramic waste fragments obtained from local industry were crushed and sieved to produce fine aggregates. The measured concrete properties demonstrate that while workability was reduced with increasing ceramic waste content for Portland cement concrete and fly ash concrete, the workability of the fly ash concrete with 100% ceramic waste as fine aggregate remained sufficient, in contrast to the Portland cement control concrete with 100% ceramic waste where close to zero slump was measured. The compressive strength of ceramic waste concrete was found to increase with ceramic waste content and was optimum at 50% for the control concrete, dropping when the ceramic waste content was increased beyond 50%. This was a direct consequence of having a less workable concrete. However, the compressive strength in the fly ash concrete increased with increasing ceramic waste content up to 100%. The benefits of using ceramic waste as fine aggregate in concrete containing fly ash were therefore verified.     

Influence of the aggregate quality on the physical properties of natural feebly-hydraulic lime mortars

This paper examines the influence of the shape, average size and calcite content of the aggregate on strength, porosity, water absorption, density and capillary suction of natural feebly-hydraulic lime (NHL 2) mortars. Four types of aggregate were analysed in order to determine calcite content, particle shape and average particle size. Four different mortar mixes were then designed and produced using each of the aggregate types and NHL 2 as a binder. The mixing and curing as well as the aggregate:binder proportions were kept constant in order to attribute variation of mortar properties to the quality of the aggregate. The results suggest that an increase in the aggregate’s calcite content lowers the flexural and compressive strength of the mortar. This study also determined that sharp aggregate as well as aggregate with a small average particle size tends to increase the mechanical strength and bulk density of a mortar simultaneously reducing porosity, water absorption and capillary suction. Furthermore, this paper concludes that aggregates containing particles of a wide size range will also increase the mechanical strength and bulk density of the hardened mortar diminishing porosity, water absorption and capillary suction.      

Effect of magnesium sulfate on the durability of limestone mortars based on quaternary blended cements

Currently, the use of blended cements incorporating various supplementary cementing materials, preserved in aggressive environments has become common. This paper describes the investigation results conducted on the evaluation of the resistance to magnesium sulfate solution (MgSO₄) of limestone mortars containing simultaneously; limestone filler, blast furnace slag and natural pozzolan. In this study, the deterioration of limestone mortars due to sulfate attack was evaluated by measuring changes in weight, length and compressive strength at the ages of 30, 60, 90, 120 and 180 days of immersion in exposure environments. The X-ray diffraction was also used in order to determine the different mineral phases. It is noteworthy that, the pH variation of the conservation solutions has been monitored during tests. The exposure solution was renewed monthly until the end of tests. The results showed that, the resistance to sulfate attack of mortars made with quaternary binders was better than that of mortars based on ordinary Portland cement.     

The effect of metakaolin on the corrosion behavior of cement mortars

In this paper the effect of metakaolin addition on the corrosion resistance of cement mortar is studied. A poor Greek kaolin with a low kaolinite content was thermally treated and the produced metakaolin (MK) was ground to the appropriate fineness. In addition, a commercial metakaolin (MKC) of high purity was used. Several mixture proportions were used to produce mortar specimens, where metakaolin replaced either sand or cement. Mortar specimens were then exposed to the corrosive environment of either partial or total immersion in 3.5% w/w NaCl solution. For the evaluation of the performance of metakaolin, the following methods were used: compressive strength, corrosion potential, mass loss, electrochemical measurements of the corrosion rate by the Linear Polarization method, carbonation depth and porosity. It is concluded that metakaolin improves the compressive strength and the 10% w/w addition shows the optimum contribution to the strength development. In addition, the use of metakaolin, either as a sand replacement up to 20% w/w, or as a cement replacement up to 10% w/w, improves the corrosion behavior of mortar specimens, while when metakaolin is added in greater percentages there is no positive effect.     

Effects of windshield waste glass on the properties of structural repair mortars

The use of waste glass incorporated into construction materials has been the focus of several studies. Its utilization in cementitious matrices as a cement surrogate has been the most suitable application because of its potential pozzolanic properties. In this study, the influence of varying the amount of cement replaced by waste glass on several mechanical properties considered essential to ensuring the performance of mortars in structural repair, such as compressive strength, modulus of elasticity, linear shrinkage and tensile bond strength, was analyzed. Additionally, the influence of waste glass on water absorption by capillarity and the microstructure of these mortars were also assessed. The results indicate the potential use of this waste material for cement mortars. The 5% replacement rate showed the best results.     

The effect of heat treatment on the compressive strength of cement-slag mortars

Thirty-eight mix proportions of ordinary Portland cement-slag mortars (OSMs) were used to study the effects of temperature and relative humidity on strength. Three levels of slag (0%, 40%, and 50%) and different temperatures were used; the 50% level and heat curing of 60 °C for duration of 20 h were found to be the optimum. The optimum mortar’s strength at 3 and 7 days for the specimens cured in air were 55.0 and 62.0 MPa, respectively. The results show that for durations of 4–26 h, the strength of specimens cured in air is greater than those cured in water. This is a novelty with major advantages in arid areas. It was proved that more ettringite production at early ages resulted in higher early strengths. Comparison of curing regimes with different temperatures and the same relative humidity or different relative humidity and the same temperatures showed that higher strengths are attributed to higher temperatures and lower relative humidity, respectively.     

Effects on concrete durability of using recycled ceramic aggregates

Ceramic waste from ceramic and construction industries is one of the most important parts in the global volume of construction and demolition waste (CDW). Ceramic waste may have several uses, one of which as coarse aggregate for concrete artefacts. Within a research campaign in course at Instituto Superior Técnico (IST), concerning the reuse and recycling of CDW, the viability of replacing primary limestone aggregates with ceramic waste on the production of concrete pavement slabs has been studied. Compression and bending tests previously performed have shown the mechanical suitability of replacing, at least partially, limestone aggregates with ceramic recycled ones. In this paper, the results of the water absorption tests, either by capillarity or by immersion, and the results of the abrasion resistance tests are presented, all related to long-term concrete durability.