Effect of aggregates and water contents on the properties of magnesium phospho-silicate cement

Properties of magnesium phospho-silicate cement (MPSC) mortars with different fine aggregates, and different water contents were investigated in the present work. Three types of fine aggregates, natural sand, dead burnt magnesia and alumina particles were used. Two types of hard burnt magnesia powder with MgO content 89.51 and 71.50 wt.% were used as binder. Compressive strength of MPSC mortar with different water/binder ratios were determined at ages of 1, 3, 7, and 24 h. The 3, 7, and 28 day compressive strength and modulus of elasticity were also tested. It was found that the compressive strength of MPSC mortar decreases with the increase of sand content, regardless of sand type. However, the strength reduction of MPSC mortars formed with magnesia and alumina sand was much smaller than that of mortars formed with natural sand. Moreover, in spite of the raw materials, compressive strength and elastic modulus of MPSC decreased with the increase of water/binder ratio at all ages. The hydrate products were analysed by XRD and TG-DTA, and the porosity of MPSC mortar was analysed by MIP. Results showed total porosity increased with the increase of water content. The content of hydrate product of MPSC, phosphate hexahydrate, also increased with the increase of water content. However, it seems that the change of mechanical properties of MPSC is mainly controlled by increase of total porosity which was determined by water content.     

Durability of lightweight masonry mortars made with white recycled polyurethane foam

Masonry mortars made with Portland cement, sand, water and white recycled polyurethane foam from industrial waste are examined in this study. Different mixtures were firstly prepared through the substitution of different amounts of sand by equivalent volumes of polyurethane and then, with different ratios of cement/aggregates. The comparative study was carried out on the effect that different ageing tests have on the mechanical properties of these mortars under flexion and compression. For this purpose, the samples were exposed to different corrosion and hardness tests: resistance to dry heat, hot water, salt spray test and Kesternich testing. After ageing, a small reduction in compressive strength was observed. However, in all the samples, the strength values were sufficiently high to consider that these types of recycled materials remain practically unaffected when compared with the reference specimens. Finally, alkali-silica reaction tests were performed to determine the chemical stability of these mortars.     

Durability of lightweight masonry mortars made with white recycled polyurethane foam

Masonry mortars made with Portland cement, sand, water and white recycled polyurethane foam from industrial waste are examined in this study. Different mixtures were firstly prepared through the substitution of different amounts of sand by equivalent volumes of polyurethane and then, with different ratios of cement/aggregates. The comparative study was carried out on the effect that different ageing tests have on the mechanical properties of these mortars under flexion and compression. For this purpose, the samples were exposed to different corrosion and hardness tests: resistance to dry heat, hot water, salt spray test and Kesternich testing. After ageing, a small reduction in compressive strength was observed. However, in all the samples, the strength values were sufficiently high to consider that these types of recycled materials remain practically unaffected when compared with the reference specimens. Finally, alkali-silica reaction tests were performed to determine the chemical stability of these mortars.     

Characterization of historical mortars from Santa Catarina (Brazil)

The aim of this research is to characterize the mortars (binder and aggregate) of nine historical buildings, built between 1750 and 1922, in the State of Santa Catarina, Brazil, using X-ray diffraction (XRD), thermogravimetry (TG), Fourier transform infra-red spectrometry (FT-IR) and atomic absorption spectrometry (AAS). The compositions and granulometric distributions of the aggregates were determined by sedimentology, and the aggregate content was estimated by hot hydrochloric acid attack.The results showed that the principal binder is hydrated lime, obtained from the burning of seashells, in some cases mixed with hydraulic materials (clay, ground ceramic tile or brick, and hydraulic lime). The results of the hot HCl attack revealed three average binder/aggregate ratios.     

The role of aggregates on the structure and properties of lime mortars

Lime mortars have been used for centuries in civil engineering construction. Considering ancient monuments and historical buildings it seems that these mortars have proved to be durable and reliable materials although they are of low strength in comparison with cement mortars. Nowadays, they are used for the repair of monuments and for the manufacture of renderings and plasters.

In the present paper the role of aggregates on the structure and behaviour of lime mortars is examined by studying the influence of the aggregate content and the grain size on strength, porosity and volume stability of the mortars. Capillary porosity by suction was also measured as an indicator of resistance to weathering. It is shown that coarse aggregates contribute to the volume stability of lime mortars independent of strength enhancement when adequate compaction reduces the capillary pores. The highest strength values, and consequently, the low porosity, were attained by lime mortars of low binder/aggregate ratio which contained aggregates of maximum size 0–4 mm.     

Effect of W/B ratios on pozzolanic reaction of biomass ashes in Portland cement matrix

In this study, the effects of W/B ratios on pozzolanic reaction of by-product biomass ashes, namely rice husk-bark ash (RHBA) and palm oil fuel ash (POFA), were determined. These biomass ashes were ground to the same fineness as that of Type I Portland cement (OPC) and partially replaced OPC at replacement levels of 10-40% by weight of binder. Water to binder (W/B) ratios of 0.50, 0.575, and 0.65 were used. The compressive strengths of mortars were compared to those of mortars made with OPC partially replaced with ground river sand of similar particle size. The results demonstrate that at the same cement replacement levels, the degrees of pozzolanic reaction of RHBA and POFA increase with W/B ratio. In addition, ground river sand with the same particle size of OPC can be used as a non-reactive material to replace OPC for determining the compressive strength due to pozzolanic reaction of biomass ash.     

The use of oil shale ash in Portland cement concrete

An experimental investigation was undertaken to study the potential use of Jordanian oil shale ash (OSA) as a raw material or an additive to Portland cement mortar and concrete. Different series of mortar and concrete mixtures were prepared at different water to binder ratios, and different OSA replacements of cement and/or sand. The compressive strength of mortar and concrete specimens, cured in water at 23 °C, was determined over different curing periods which ranged from 3 to 90 days. The results of these tests were subjected to a statistical analysis. Equations were developed by regression analysis techniques to relate the effect of batch constituents on the strength developments of OSA mortars and concretes. The models were checked for accuracy by comparing their predictions with actual test results.The obtained results indicated that OSA replacement of cement, sand or both by about 10% (by wt) would yield the optimum compressive strength, and that its replacement of cement by up to 30% would not reduce its compressive strength, significantly. It was found that OSA on its own possesses a limited cementitious value and that its contribution to mortar or concrete comes through its involvement in the pozzolanic reactions. The statistical model developed showed an excellent predictability of the compressive strength for mortar and concrete mixes.     

Influence of elevated temperatures on the mechanical properties of blended cement concretes prepared with limestone and siliceous aggregates

The investigation performed was aimed at showing the influence of high temperatures on the mechanical properties and properties that affect the measurement by non-destructive methods (rebound hammer and pulse velocity) of concrete containing various levels (10% and 30%) of pozzolanic materials. Three types of Pozzolans, one natural pozzolan and two lignite fly ashes (one of low and the other of high lime content) were used for cement replacement. Two series of mixtures were prepared using limestone and siliceous aggregates. The W/b and the cementitius material content were maintained constant for all the mixtures. Concrete specimens were tested at 100, 300, 600 and 750 °C for 2 h without any imposed load, and under the same heating regime. At the age of 3 years, tests of compressive strength, modulus of elasticity, rebound hummer and pulse velocity were come out. Results indicate that the residual properties of concrete strongly depend on the aggregates' and the binder type. Relationships between strength of concrete as well as rebound and pulse velocity versus heating temperatures are established. The above results are evaluated to establish a direct relationship between non-destructive measurements and compressive strength of concrete exposed to fire.     

High strength concrete containing natural pozzolan and silica fume

Various combinations of a local natural pozzolan and silica fume were used to produce workable high to very high strength mortars and concretes with a compressive strength in the range of 69–110 MPa. The mixtures were tested for workability, density, compressive strength, splitting tensile strength, and modulus of elasticity. The results of this study suggest that certain natural pozzolan–silica fume combinations can improve the compressive and splitting tensile strengths, workability, and elastic modulus of concretes, more than natural pozzolan and silica fume alone. Furthermore, the use of silica fume at 15% of the weight of cement was able to produce relatively the highest strength increase in the presence of about 15% pozzolan than without pozzolan. This study recommends the use of natural pozzolan in combination with silica fume in the production of high strength concrete, and for providing technical and economical advantages in specific local uses in the concrete industry.     

Thermal Conductivity of Building Materials Employed in the Preservation of Traditional Structures

Historic structures are a part of our cultural heritage and nowadays, in the polluted environment, the need of their preservation is more intense than ever. One of the anticipated problems includes new materials that have to be compatible with those existing in older structures. In the case of mortars, traditional binders such as lime, natural pozzolanas, brick dust, and white cement have been combined successfully. In the present article a series of mixtures combining lime, two types of natural pozzolanas, brick dust, and different types of cement have been produced in order to measure their thermal conductivity for the first time. The parameters tested are: the binder type, the proportion of the binders, and the water/binder ratio. For the measurement of the thermal conductivity of the samples, a commercial instrument was used. To test its operability and extend its range, a transient hot-wire instrument was employed.     

Effect of mixture constituents on properties of slaked lime–metakaolin–sand mortars containing sodium hydroxide

In the present study, percentage of slaked lime (20–30%) in binder with metakaolin, water–binder ratio (0.8–1.0), sand–binder ratio (1–3) and sodium hydroxide (NaOH)–binder ratio (0.02–0.04) were factors varied to investigate properties of fresh or hardened mortars. Sodium hydroxide was used as a chemical activator in the slaked lime–metakaolin binders. Properties studied after 7 or 28 days of curing mortars at 40 ± 1 °C were consistency, compressive strength and water absorption. The physical, chemical, mineralogical and pozzolanic characteristics of materials used in study were determined. It was concluded that water–binder and sand–binder ratios are the most influential factors for consistency and water absorption of mortars. Compressive strength is influenced by all mixture constituents but NaOH–binder ratios less than 0.03 are recommended for use in mortars.     

Properties of self-compacting mortar made with various types of sand

Higher cement and fines content is needed in self-compacting mortars (SCMs) to increase their flowability and stability. Different inert fillers and supplementary cementitious materials are usually added. The use of sands rich in fines may be a cost effective alternative source of filler. This paper presents the results of an experimental study on the rheological and mechanical properties of self-compacting mortars (SCMs) made with various types of sands: crushed sand (CS), river sand (RS), dune sand (DS) and a mixture of different sands. The mini-slump flow, V-funnel flow time and viscosity measurement tests were used to study the rheological properties. The experimental results indicate that the rheological properties and strength improve with mixtures of crushed and river sands but decrease with mixtures of crushed and dune sands especially for higher dune sand content. Crushed sand with (10–15%) of limestone fines can be used successfully in production of SCM with good rheological and strength properties. However, a reduction in compressive strength with increasing dune sand content (up to 50%) in mortar with binary and ternary sands was observed.     

Properties of self-compacting mortar made with various types of sand

Higher cement and fines content is needed in self-compacting mortars (SCMs) to increase their flowability and stability. Different inert fillers and supplementary cementitious materials are usually added. The use of sands rich in fines may be a cost effective alternative source of filler. This paper presents the results of an experimental study on the rheological and mechanical properties of self-compacting mortars (SCMs) made with various types of sands: crushed sand (CS), river sand (RS), dune sand (DS) and a mixture of different sands. The mini-slump flow, V-funnel flow time and viscosity measurement tests were used to study the rheological properties. The experimental results indicate that the rheological properties and strength improve with mixtures of crushed and river sands but decrease with mixtures of crushed and dune sands especially for higher dune sand content. Crushed sand with (10–15%) of limestone fines can be used successfully in production of SCM with good rheological and strength properties. However, a reduction in compressive strength with increasing dune sand content (up to 50%) in mortar with binary and ternary sands was observed.     

Effects of cold-bonded fly ash aggregate properties on the shrinkage cracking of lightweight concretes

This paper presents an experimental study on the restrained shrinkage cracking of the lightweight concretes made with cold-bonded fly ash lightweight aggregates. Two types of fly ash having different physical and chemical properties were utilized in the production of lightweight aggregates with different strengths. Afterwards, lower strength aggregates were also surface treated by water glass and cement–silica fume slurry to improve physical and mechanical properties of the particles. Therefore, a total of eight concrete mixtures were designed and cast at 0.35 and 0.55 water–cement ratios using four types of lightweight coarse aggregates differing in their surface texture, density, water absorption, and strength. Ring type specimens were used for restrained shrinkage cracking test. Free shrinkage, creep, weight loss, compressive and splitting tensile strengths, and modulus of elasticity of the concretes were also investigated. Results indicated that improvement in the lightweight aggregate properties extended the cracking time of the concretes resulting in finer cracks associated with the lower free shrinkage. Moreover, there was a marked increase in the compressive and splitting tensile strengths, and the modulus of elasticity.     

Compressive strength development of binary and ternary lime–pozzolan mortars

This study considers the compressive strength development of broad range of hydraulic lime mortars prepared with a range of commercially available alumino-silicate by-products and modern pozzolanic additions. Specifically this paper considers the effect of mineral addition selection, binary and ternary combinations, pozzolan content and the effect of curing conditions on the compressive strength development of hydraulic lime based mortars. The study was undertaken as the initial phase of a broader investigation considering the feasibility of producing modern, sustainable hydraulic lime–pozzolan concretes with comparable strengths to Portland cement based concretes. The aim of the initial phase was to identify a small number of additions, and combinations thereof, which would result in a structural strength lime–concrete when scaled up from mortars to concretes.In the absence of a definitive source of information on the mechanical properties of hydraulic-lime mortars prepared with binary and ternary combinations of alumino-silicate by-products, 22 combinations consisting of Natural Hydraulic Lime (NHL5) and a range of possible additions, identified from historical and current practice, were prepared. The results have shown that combining an eminently-hydraulic NHL5 with silica fume and ground granulated blastfurnace slag can produce mortars with a 28-day compressive cube strength of around 28 N/mm², at a water-to-binder (w/b) ratio of 0.5. This is eight times the strength of an equivalent mortar prepared with NHL5 alone and broadly speaking comparable with that of low-heat cementitious mortars. The contribution of the pozzolanic reaction to the strength of hydraulic lime mortars is discussed for a range of alumina-silicious materials and combinations thereof.     

Properties of some cement stabilised compressed earth blocks and mortars

Findings from an on-going investigation into the effects of soil properties and cement content on physical characteristics of compressed earth blocks and soil mortars are presented. A series of test blocks were fabricated using a range of composite soils, stabilised with 5% and 10% cement, and compacted with a manual press. Results for saturated compressive strength, drying shrinkage, wetting/drying durability, and water absorption testing are presented in the paper. In conjunction with the block tests, workability and compressive strength characteristics of suitable soil: cement and cement: lime: sand mortars were also studied. Mortar consistency was assessed using cone penetrometer and slump tests. Water retention properties of the mortars were also measured. For a given compactive effort, the strength, drying shrinkage, and durability characteristics of the compressed earth blocks improved with increasing cement and reducing clay content. Slump testing proved the most reliable means of assessing soil: cement mortar consistency. Both the flow table and cone penetrometer tests were found to be unsuitable. Water retention properties of soil: cement mortars appear well-suited to typical unit water absorption characteristics. Mortar strengths were closely related to cement and clay contents, but as expected were less than the average unit strengths.     

Early-age autogenous cracking of cementitious matrices: physico-chemical analysis and micro/macro investigations

High-performance cement-based materials, characterized by low water-to-cement (W/C) ratio and high cement content, are sensitive to early-age cracking because their autogenous shrinkage rate and magnitude are particularly high during this period. This article firstly presents experimental tools especially designed for the measurement of free and restrained autogenous shrinkage at early-age. Then, the results of a multi-parameter experimental study conducted on three different types of binder are analyzed. The physico-chemical deformations of cement pastes and mortars were measured from the very early-age up to several days in saturated and autogenous conditions to investigate the effects of binder, water-to-binder ratio, presence of aggregates and temperature on the driving-mechanisms leading to early-age autogenous cracking. Complementary tests such as hydration rate measurement and microscopic observations were also performed. Among the three binders used, the blast furnace slag cement shows higher chemical strain, for a given quantity of chemically-bound water, and higher early-age autogenous shrinkage. The presence of aggregates generates a local restraining effect of cement paste deformations, leading to the formation of microcracks in the surrounding cement paste. Ring test results reveal that the first through crack of cement pastes systematically appears for maximal internal stress values lower than the material tensile strength, estimated with three-point flexural tests. This phenomenon may be due to diffuse damage of the cementitious matrix, whose deformations are partially restrained.     

Diffusivity evolution under decalcification: influence of aggregate natures and cement type

Since the decalcification of cement paste has been largely reviewed, we focus our studies on the influence of aggregate nature on this phenomenon in relation to the type of cement used, Ordinary Portland Cement or blended cement with fly ash and slag. Some characteristics of similar mortar mixtures where only aggregate nature differs (lime and siliceous sand) are therefore compared for the two types of cement before and after chemical decalcification induced by ammonium nitrate attack: mechanical strength, microstructure (porosity observed by mercury intrusion and profiles of oxide content trough degraded and sound zones determined by electronic microprobe analysis), transport properties (chloride ions diffusivity, gas and water permeabilities). The characterization of sound mortars underlines that siliceous aggregates promote less porous cementitious matrix. The duplication of ammonium nitrate attacks on same material allows testing the experimental parameters governing the degradation. The flows of calcium leached, the microstructure and the evolution of transport properties with decalcification suggest that limestone aggregates are not inert material. Consequently, for the mortars incorporating siliceous sand, the cementitious matrix is more decalcified and this leads to an amplification of ionic transports, especially through blended cement paste.     

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 limestone powder,fly ash and silica fume on the properties of self-compacting repair mortars

Self-compacting repair mortars (SCRM) are preferred for the rehabilitation and repair of reinforced concrete structures especially at narrow mould systems. Self compactability and stability are susceptible to ternary effects of chemical and mineral admixture type and their content. In this study, the effect of limestone powder (LP) on the properties of SCRM has been compared with other mineral additives (silica fume (SF) and fly ash (FA) and their combinations) effects. Fresh properties, flexural and compressive strengths and water absorption properties of mortars were determined. The use of SF in mortars significantly increased the dosage of superplasticiser (SP). At the same constant SP dosage (0·8%) and mineral additives content (30%), LP can better improve the workability than that of control and FA mixtures by 19% and 27%. However, the results of this study suggest that certain FA, SF and LP combinations can improve the workability of SCRMs, more than FA, SF and LP alone. LP can have a positive influence on the mechanical performance at early strength development while SF improved aggregate-matrix bond resulting from the formation of a less porous transition zone in mortar. SF can better reducing effect on total water absorption while FA and LP will not have the same effect, at 28 days.