Strength and mechanical behavior of soil–cement–lime–rice husk ash (soil–CLR) mixture

This study presents results of geotechnical investigations on treated silty sand soil with cement, lime and rice husk ash (CLR) and cement-lime (CL) admixture. Consolidated undrained triaxial test and unconfined compressive test were performed to estimate the potential of CLR and CL. The study investigates the influence of the amount of CLR%, main effective stress and curing days on soil strength, deformation, post peak behavior and brittleness. The percentages of the additives of CLR and CL varied from 2.5 to 12.5 % by dry weight of the soil with dry densities of 14.5 kN/m³ and the curing times of 3, 7, 28 and 60 days were examined. From the results, the stress–strain response is strongly influenced by the CLR contents and effective confining pressure. Strength and post peak strength of the CLR–soil are greatly improved by an increase in binder content. An increase of the effective cohesion c′ (kPa) and effective friction Φ′ (degree) is observed with increasing the CLR content, consistently. Brittle behavior observed at lower confining pressures and high CLR content. For both CLR and CL additives, linear trend was observed for variation of the q _u (kPa) with respect to the additives percentages. RHA was also found to be effective in increasing the shear strength of CLR–soil mixture.     

Utilisation of oil-contaminated sand stabilised with cement kiln dust in the construction of rural roads

This article investigates the strength behaviour of oil-contaminated sand stabilised with cement kiln dust (CKD) in order to assess the engineering properties of the stabilised soil for its application in the construction of rural road. Tests including pH measurement, compaction, unconfined compressive strength (UCS) and California bearing ratio (CBR) were conducted. The investigations were carried out by varying the percentage of CKD, the percentage of oil content, the type of oil, the ageing of stabilised samples and the ambient temperature. Depending on the pH response, the CKD content from 5% to 15% represents a practical limit for cost-effective stabilisation. Results revealed that an increase in the UCS and CBR values of oil-contaminated sand occurred with the addition of CKD. The strength of stabilised contaminated sand decreases as the percentage of oil increases. The addition of 10% CKD to the sand contaminated with 6% oil content is found to give the optimum UCS and CBR values. Furthermore, a series of two-dimensional finite-element model was developed using PLAXIS software package.     

Engineering and environmental evaluation of spent coffee grounds stabilized with industrial by-products as a road subgrade material

Current construction technology increasingly seeks the sustainable usage of waste by-products as a resource material. This paper evaluates the viability of utilizing spent coffee grounds (CG), a highly organic beverage waste, to be stabilized as a road subgrade material. The additives used in this research incorporates industrial by-products such as fly ash (FA), ground granulated blast-furnace slag (S) as well as traditional binders such as portland cement (PC) and hydrated lime (L). CG collected from a coffee roaster were mixed with controlled additive content ratios by mass to assess the effects of these common engineering stabilizers towards the load-bearing capacity of CG. The additive contents of FA and S were 10, 20, 30, 40, and 50 % whereas the PC and L additive contents were 3 and 5 % by dry unit weight. Modified proctor compaction tests, 7-days unconfined compressive strength (UCS) tests, and California bearing ratio (CBR) tests were carried out to determine the optimum moisture content and bearing strength of the different mixes produced. It found that as the proportion of additives in the specimen increased, the optimum moisture content of the additive-stabilized CG specimens subsequently decreased. Regardless of the type of stabilizers used, the UCS strength increases were found to be nominal. FA and S mixes above the 20 % additive contents satisfied the requirements for subgrade materials; however, the low PC and L contents were insufficient to meet subgrade requirements. The research findings indicate that instead of being disposed of into landfills, stabilized CG has the potential to be used as a subgrade material. Such a sustainability driven approach for reuse of CG will have the potential to divert CG from landfills and at the same time utilize CG as a viable construction material.     

Heat and Moisture Transport and Storage Parameters of Bricks Affected by the Environment

The effect of external environment on heat and moisture transport and storage properties of the traditional fired clay brick, sand–lime brick and highly perforated ceramic block commonly used in the Czech Republic and on their hygrothermal performance in building envelopes is analyzed by a combination of experimental and computational techniques. The experimental measurements of thermal, hygric and basic physical parameters are carried out in the reference state and after a 3-year exposure of the bricks to real climatic conditions of the city of Prague. The obtained results showed that after 3 years of weathering the porosity of the analyzed bricks increased up to five percentage points which led to an increase in liquid and gaseous moisture transport parameters and a decrease in thermal conductivity. Computational modeling of hygrothermal performance of building envelopes made of the studied bricks was done using both reference and weather-affected data. The simulated results indicated an improvement in the annual energy balances and a decrease in the time-of-wetness functions as a result of the use of data obtained after the 3-year exposure to the environment. The effects of weathering on both heat and moisture transport and storage parameters of the analyzed bricks and on their hygrothermal performance were found significant despite the occurrence of warm winters in the time period of 2012–2015 when the brick specimens were exposed to the environment.     

Thermal Transmittance of Porous Hollow Clay Brick by Guarded Hot Box Method

The thermal property of a porous hollow clay brick was determined by measuring the thermal transmittance of the wall made of porous hollow clay bricks. Prior to the production of porous hollow clay bricks, nonporous and porous tiny clay bricks were prepared to determine the physico-mechanical properties by modifying the amount of wood flour and firing temperature. The bricks were produced by uniaxial pressing and then fired in an electric furnace. Their physico-mechanical properties were measured by water absorption, apparent porosity, bulk density, and compressive strength. The porous tiny clay bricks were produced with three types of wood flour: coarse wood flour (1–0.36 mm), medium-sized wood flour (0.36–0.15 mm), and fine wood flour (< 0.08 mm). The thermal transmittance of porous hollow clay bricks was determined through the guarded hot box method, which measures the wall made of porous hollow clay bricks and nonporous cement bricks. The two walls had a thermal transmittance of 1.42 and 2.72 \(\hbox {W}\cdot \hbox {m}^{-2}\cdot \hbox {K}^{-1}\), respectively. The difference in thermal transmittance was due to the pores created with fine wood flour (< 0.08 mm) as a pore-forming agent.     

Behaviour of sand–clay mixtures for road pavement subgrade

Materials forming sand grains and colluvial soil deposits have a distinct structure, consisting of a composite matrix of coarse and fine soil grains. The influence of sand grains content on the behaviour of sand–clay mixtures was investigated by a series of intensive laboratory experiments. The California bearing ratio (CBR), unconfined compression strength (UCS) and compaction tests were carried out on various contents of sand and clay mixtures. The sand–clay mixtures were prepared with sand contents of 0, 10, 20, 30, 40, and 50% by weight. The laboratory tests on these mixtures have indicated that their behaviour will depend on the relative concentration of the sand and clay samples. The results of the tests showed a decrease in the UCS, and an increase the CBR values with an increase in the amount of sand. An increase in dry unit weight and a decrease in respective moisture content by an increase in the amount of sand were observed in the compaction tests.     

Development and investigation of cellular light weight bio-briquette ash bricks

The present paper deals with the development of cellular light weight bricks using bio-briquette ash. The necessary physical and chemical tests were conducted on a bio-briquette ash sample to investigate its suitability for the development of bricks. Physico-mechanical, durability and thermal conductivity tests were conducted on cellular light weight bio-briquette ash bricks that fulfilled the requirements of Indian standard. The test results of cellular light weight bio-briquette ash bricks were compared with commercially available fly ash bricks. With reference to fly ash bricks, the cellular light weight bio-briquette ash bricks were found 43 % light in weight, having 13 % higher compressive strength and resulted in 66 % lesser thermal conductivity. A small scale model room (1 m × 1 m × 1 m) made up of fly ash bricks was designed. A similar built form for the cellular light weight bio-briquette ash bricks was also modelled. Both the models were analysed for indoor temperature control and cost. When compared with fly ash model room, cellular light weight bio-briquette ash brick model resulted in a 6 % better indoor temperature control and 29 % cost savings. Thus, the developed cellular light weight bio-briquette ash bricks were found suitable as an alternate construction material for non-load bearing walls.     

Influence of the design materials on the mechanical and physical properties of repair mortars of historic buildings

Historic buildings are subjected to deterioration by natural weathering or by corrosion due to polluted atmosphere and the materials more susceptible are the mortars used. This study examines the influence of the type and quantity of design materials on compressive strength, creep, water absorption and length change of repair mortars produced. The design materials used were lime, natural pozzolan, sand and brick fragments in order to obtain the compatibility required between historic and repair mortars; different quantities of Portland cement were also used in order to quantify his influence. Nine mixtures were then designed and produced considering as parameters two binder: aggregates ratios, three pozzolan: cement ratios and three sand: brick fragments ratios. The experimental measurements continued until the age of 3 years or the stabilization of the test values. The results indicate that compressive strength is strongly affected by cement content and aggregates dosage and type. It appears that the increase of cement as well as brick fragments leads to confinement of creep deformation, while the mixtures with high pozzolan and sand content experience considerably high creep values. Water absorption reaches higher values when pozzolan or aggregate dosage arises and brick is in excess. Shrinkage increases when binder or brick quantity arise and is considerably influenced by cement content.     

Valorization of stabilized river sediments in fired clay bricks: factory scale experiment

The objective of this study is to demonstrate the practical use of polluted river sediments after treatment into brick production. Consequently, a full-scale industrial experiment was conducted at a brick factory in the north of France. Polluted sediment was stabilized by the Novosol process and then was introduced in the mix-design with a substitution ratio of 15% as a partial replacement of quartz sand. Approximately 15,000 perforated sediment-amended bricks were produced. The produced bricks were then subjected to several qualification tests (compressive strength, freeze and thaw resistance, water absorption). The results obtained showed that the substitution of quartz sand by treated sediment resulted in a significant increase in brick compressive strength and firing shrinkage, and in a decrease in porosity and water absorption. Moreover, leaching tests performed according to different standards on substituted brick samples showed that the quantities of heavy metals leached from crushed bricks were within the regulatory limits. Thus substituted bricks can be regarded as non-hazardous material.     

碱激发和复合激发下建筑垃圾砖粉活性研究

为提高建筑垃圾废砖再生利用率,采用砂浆力学测试手段研究了建筑垃圾砖粉活性和碱激发、复合激发对建筑垃圾砖粉活性的影响,并借助扫描电镜和热分析方法对建筑垃圾砖粉、建筑垃圾复合粉体材料的颗粒形貌、水化产物组成等进行了研究。结果表明:建筑垃圾砖粉活性较小,当掺量大于20%时,砂浆强度随其掺量的增加直线下降;不同碱激发剂对建筑垃圾砖粉有不同的激发效果,Ca(OH)2激发效果最好,NaOH次之,Na2SiO3·9H2O激发效果最差;复合形成的建筑垃圾复合粉体材料具有较好的活性,当其掺量不超过40%时,砂浆28d抗压强度高达50 MPa。微观分析结果表明:建筑垃圾复合粉体材料比砖粉具有更好的颗粒级配,在其水化过程中降低了稳定性较差的Ca(OH)2含量,提高了水泥石密实度,是一种经济、环保的新材料。     

Steel slag and iron ore tailings to produce solid brick

The main goals of this work were to verify the potential of reuse of steel slag and iron ore tailings as secondary raw materials to produce solid brick and to evaluate whether this application can consume the amount of slag generated in Brazil. The feasibility of this application was verified through a comparative study. The mechanical behavior of concrete artifacts and pressed bricks made from residues was compared with others described in the literature. The residues were initially characterized using chemical and granulometric analysis. The bricks were produced by mixing different compositions of the residues with the addition of cement in the contents of 0 and 5%. The bricks were pressed in a manual mechanical press and sent to curing. The values of flexural strength of the bricks were higher than 2.0 MPa, and the average weight of the bricks was like those found in the ecological bricks. The simulation with the construction of houses showed that the proposed application can consume the amount of slag generated in Brazil. The generation of the income from carbon credits associated with CO₂ reduction is an incentive to implement environmental management tools in Quadrilátero Ferrífero territory, specifically, industrial symbiosis and the carbon market.     

A micromechanical model for linear homogenization of brick masonry

A micromechanical model, originally developed for long-fiber composites, is applied to determination of the overall linear-elastic mechanical properties of simple-texture brick masonry. The model relies upon exact solution after Eshelby and describes brickwork as a mortar matrix with insertions of elliptic cylinder-shaped bricks. The macroscopic elastic constants are derived from the mechanical properties of the constituent materials and the phase volume ratios. The ability of the suggested model to predict the behavior of real brickwork has been checked by performing uniaxial compression tests on brick masonry panels of two types, with cement mortar and lime mortar. The results obtained through the proposed model fit experimental data more closely than other models selected from the literature for the sake of comparison.     

An application of blended fly ash and residual rice husk ash for producing green building bricks

The present study investigates the possibility of using a blended class-F fly ash (FA) and residual rice husk ash (RHA) in the production of green building bricks through the application of densified mixture design algorithm (DMDA) in order to provide a new use for solid waste materials. This study uses unground rice husk ash (URHA) as a partial fine aggregate substitution (10–40%) in the studied cementitious mixtures. Solid bricks of 220 × 105 × 60 mm in size were prepared under forming pressure of 25–35 MPa, a curing temperature of 90 °C, and a relative humidity of 50%, for tests that assessed: compressive strength, flexural strength, bulk density, void volume, and water absorption. The test results showed that all brick samples demonstrated excellent properties. Compressive strength and flexural strength ranged, respectively, between 20.2–33 MPa and 5.4–6.9 MPa. Additionally, up to 30% of URHA content, the values of water absorption and void volume ranged, respectively, between 8.8–15.7% and 1.5–2.1%. All of these values not only conformed well to the requirements of the Vietnamese codes but also demonstrated great potential for using a blended FA–RHA in producing green building bricks.     

Direct and interactive influence of explanatory variables on properties of a calcium phosphate cement for vertebral body augmentation

We used the response surface methodology to investigate the direct and interactive effects of three explanatory variables on three properties of a calcium phosphate cement (CPC) for use in vertebroplasty (VP) and balloon kyphoplasty (BKP). The variables were poly(ethylene glycol) content of the cement liquid (PEG), powder-to-liquid ratio (PLR), and the amount of Na₂HPO₄ added to an aqueous solution of 4 wt/wt% poly(acrylic acid) (as the cement liquid) (SPC). The properties were injectability (I), final setting time (F), and 5-day compressive strength (UCS). We found that (1) there was an interactive effect between the variables on I and F but not on UCS; (2) the maximum I (98 %) was obtained with PEG = 20 wt/wt% and PLR = 2 g mL^?1; (3) F = 15 min (the proposed optimum value for a CPC for use in VP and BKP) was obtained with PEG = 4 wt/wt% and PLR = 2.9 g mL^?1; and (4) the maximum UCS (39 MPa) was obtained with SPC = 0 and PLR = 3.5 g mL^?1.     

Modeling of Brick Properties for Earth-Based Domes Structures

The use of earth-based materials is becoming increasingly popular, particularly in the rural areas of developing countries. One example is the introduction of an earth dome for low-cost housing in the rural areas of Mozambique [1], although this project is still at a research level. The earth bricks used in building the dome are a type of composite material, consisting of porous soil and possibly cement. The brick properties depend on the proportions of soil, cement and air-filled pores. For economic reasons, the amount of the stiffer and stronger cement phase needs to be minimized. Here, some initial experimental results and the results of a simple numerical model for estimating the stiffness and strength of the bricks are presented. The numerical analyses use a 3D linear elastic finite element program to calculate the effective elastic properties of the brick and a failure stress under uniaxial compression is calculated based on a Drucker-Prager type condition for cohesive materials.     

Fire-resistant geopolymer bricks synthesized from high-calcium fly ash with outdoor heat exposure

This research proposed an alternative utilization of high-calcium fly ash to produce geopolymer bricks for fire-resistant applications. Outdoor heat exposure (OHE) was applied to cure geopolymer mortar. The temperature was up to 40 °C. Geopolymer brick was created with a 30-day compressive strength of 47 MPa via OHE curing for 3 days. The brick experienced a low weight loss after the firing test, which indicated its fire-resistant property. For the flame test, the maximum temperature on the opposite side of the brick from the flame was lower than 380 °C, with no observable cracks, complying with the fire-test requirement. Therefore, high-calcium fly ash geopolymer cured with OHE is suitable for use as a fire-resistant material. In addition, outdoor heat exposure is a promising renewable means to cure geopolymer.     

Toughness of fibre reinforced hydraulic lime mortar. Part-2: Dynamic response

The seismic rehabilitation of historical masonry buildings necessitates a quantitative understanding of the repointing mortar under variable strain rates. In Part-1 of this paper, plain and fibre reinforced hydraulic lime mortar specimens were examined under compression, flexure and direct shear to evaluate the post-crack response under quasi-static loading. It was seen that although the fibres enhance the flexural toughness of hydraulic lime mortar, the material is weakest in Mode I fracture. In Part-2 of this paper, the authors describe the strain rate sensitivity of hydraulic lime mortar on the basis of impact testing of notched beams. The mixes were identical to those examined in Part-1, and the dynamic response was evaluated using a drop-weight impact machine for strain rates in the range of 10^?6 to 10 s^?1. The authors found that compared to fibre reinforced Portland cement-based mortar and concrete, the flexural response of hydraulic lime mortar is more sensitive to strain rate.     

Strength and elasticity of brick masonry prisms and wallettes under compression

The characteristics of brick masonry are influenced by the properties of bricks and mortar. This paper attempts at studying the properties of brick masonry using table moulded bricks and wire-cut bricks of India with various types of mortars. The strength and elastic modulus of brick masonry under compression have been evaluated for strong-brick soft-mortar and soft-brick strong-mortar combinations. Various sizes of prisms and wallettes have been tested during these experiments to study the size effect and different bonding arrangements. The failure mechanisms of such specimens have been studied. Attempts are also made to derive empirical relationships for masonry strength as a function of brick and mortar strength in the Indian context.     

Compressive strength and elasticity of pure lime mortar masonry

The procedure and findings of an experimental campaign for the mechanical characterization of brick masonry with lime mortar joints are presented. The campaign includes the determination of the properties of the constituent materials and of the resulting masonry composite. The masonry consisted of masonry stack bond prisms made of solid clay bricks and two types of pure lime/sand mortars, material combinations which correspond to the vast majority of historical and existing masonry structures. The paper includes a discussion on the ratio between the elastic modulus and the compressive strength of the masonry constituents and the comparison of these ratios with the ones suggested in design codes. The implications of this comparison are discussed in the context of interventions on historical masonry structures using modern and traditional materials.     

Effects of sucrose and sorbitol on cement-based stabilization/solidification of toxic metal waste

The effects of sucrose or sorbitol addition on the hydration, unconfined compressive strength and leachability of Portland cement pastes containing 1% Pb and 1% Zn were studied as a function of time. Whereas Pb and Zn were found to shorten the time to achieve maximum hydration of Portland cement, the combination of these metals with 0.15 wt% sucrose or 0.40 wt% sorbitol retarded the setting of cement by at least 7 and 28 days, respectively, without affecting the strength at 56 days. The leachability of Pb and Zn evaluated by the TCLP 1311 protocol at 56 and 71 days was slightly reduced or unchanged by the addition of sucrose or sorbitol. SEM-EDS and XRD analyses revealed that ettringite precipitation was favored whereas the formation of CSH gel, which accounts for most of the strength of hydrated cement, was delayed in cement pastes containing both metals and sucrose or sorbitol. These results indicate that controlled additions of sucrose or sorbitol can add flexibility to the handling of cement-treated metal waste, particularly when it needs to be transported by truck or pipeline between the treatment plant and the disposal site, without affecting its long-term performance.