Effect of a polypropylene fibre on the behaviour of aerial lime-based mortars

A polypropylene fibre was added to lime-based mortars in order to check whether they were improved by this admixture. Different properties of lime-based mortars were evaluated: fresh state behaviour through water retention, air content and setting time; hardened state properties such as density, shrinkage, water absorption through capillarity, water vapour permeability, long-term flexural and compressive strengths, pore structure through mercury intrusion porosimetry, and durability assessed by means of freezing–thawing cycles. An improvement in some properties of aerial lime-based mortars – such as permeability, mechanical strengths, reduction in macroscopic cracks or durability in the face of freezing–thawing cycles – was achieved when fibre was added at a low dosage. When a larger amount of additive was used, only the reduction in cracks and the durability of the material were improved.     

Strength–porosity relationships in lime–pozzolan mortars

Lime–pozzolan mortars are the hydraulic mortars widely used in the past for the construction of monumental structures and nowadays for their repair. These mortars are of higher porosity and lower strength in comparison with cement-based mortars but they have exhibited noticeable durability. For the design of lime–pozzolan mortars it is important to know the fundamental strength–porosity relationship as well as the parameters influencing the porosity since it is the driving factor for the functional behaviour of the mortar and its resistance to aging. In this research, an adequate number of mortar series were prepared and tested to find the effect of water/binder (w/b) ratio, the aggregate volume content, the evolution of porosity with time and formulate the strength–porosity relationship based on Power’s basic mathematical expression. According to results it seems that the water/binder ratio is the most important parameter influencing the porosity. Strength–porosity relationship can be predicted with an acceptable deviation. Porosity of lime–pozzolan mortars decreases with time and it is strongly influenced by the curing conditions.     

公路工程大孔隙试件孔隙率精确测定方法研究

阐述了孔隙率与有效孔隙率的概念，对试验规程中有关测定试件孔隙率的方法进行了分析，指出规范中各方法在测定大孔隙试件时存在的不足，并提出一种测定有效孔隙率的方法。     

Calculating air content in cement mortars

The new buying power of Saudi Arabia has quickened both building development and research and testing work in that country. Here, scientists at the Public Works Materials Testing Laboratories in Riyadh describe their methods of calculating air content of mortars made from home produced and imported cements.     

Incorporation of fine ceramics in mortars

This paper presents a study of the viability of improving the performance of cementitious mortars through the addition of very fine aggregates from crushed red clay ceramics. For that purpose, an experimental campaign was performed with the main purpose of testing the possibility of improving the performance of cementitious mortars at several levels: strength, water absorption, shrinkage, water permeability, durability, among others. The results obtained look very promising, even though this line of research needs to be further pursued.     

Polymer-cement mortars for repairing ancient masonries mechanical properties

The usual problems encountered during restoration of a historical masonry with strong adhesion mortars, are the irreversibility of the method, the incompatibility between the old and new mortar and the lowering of the masonry porosity, resulting in the increase of humidity. For these reasons, mortars with controlled strength and porosity have been designed and studied, in order to be used in restoration of ancient masonries.     

Activation of Algerian slag in mortars

Blastfurnace slag has been widely used as a successful replacement material for Portland cement, and concrete of enhanced qualities can be achieved as a result. Due to the slag’s slow reactivity, however, the early-age mechanical properties may suffer. This paper reports the results of an investigation, carried out at Chlef University (Algeria), using Algerian slag, known to exhibit low reactivity due to its low CaO/SiO₂ ratio. The slag was activated mechanically by grinding the slag to 250, 360 and 420 m²/kg Blaine surface area, thermally by curing mortar specimens at 20°, 40° and 60 °C, and chemically by mixing the slag with two alkalis, NaOH and KOH at different concentrations. Samples were tested for compressive strength at the ages of 1, 3, 7, 28 and 90 days. All three methods enhanced the reactivity of the slag. The results indicated that the slag is very sensitive to temperature rise. Increase in fineness resulted in increased strength development and the fineness of the slag must be greater than that of the cement to achieve better performance. Alkali activation of slag results in increased strength development but the strength was lower than that of the control mortar.     

相变储能型粉刷石膏的配方研究

采用正交设计方法,研究了不同因素对相变储能型粉刷石膏性能的影响,通过筛选石膏基材与相变材料的较好适应品种,确定相变储能型粉刷石膏的配方,并对优化配方后的相变储能材料进行了试验.试验结果表明,相变材料的掺量对相变储能型粉刷石膏的抗折、抗压强度影响显著,制备的相变储能型粉刷石膏凝结时间、可操作性及保水率等均符合JC/T 517-2004的要求,蓄热系数和导热系数均满足研究指标要求,强度优于传统保温砂浆.     

一种适应多品种干粉砂浆材料的生产线

对于大多数定位在生产特种砂浆的国内企业而言,产量普遍不大,年产量基本是在2万t以下,小型生产线完全能满足要求.另外,特种砂浆配方的调整非常频繁,且每个配方的产品可能产量都很有限,如何使生产线具备最大程度上的灵活性和可靠性是必须要考虑的问题.具体介绍KMA500特种干粉砂浆生产线的性能、特点及应用实例.     

Interaction diagrams to assess SCC mortars for different cement types

The present paper provides a comprehensive procedure for the design of mortar mixtures which are adequate for self-compacting concrete (SCC). A central composite design was carried out to mathematically model the influence of four mixture parameters and their coupled effects on deformability, viscosity and compressive strength of mortar mixtures. The derived models and a numerical optimization technique were used to determine the range of mortar mixture parameters where deformability and viscosity coexist in a balanced manner. Interaction diagrams are suggested to represent the optimized solutions. Six different types of cement were assessed in combination with limestone filler and a polycarboxylate type superplasticizer. Each type of cement has unique properties that interact with other constituents, resulting in different interaction diagrams and mix proportions in the concrete mixture. The utility of numerical models and optimized solutions for quality control, tailor-made concrete mixtures and selection of constituent materials is highlighted.     

Use of diatomite as partial replacement for Portland cement in cement mortars

The aim of the present study is to investigate the use of diatomite as a partial replacement for cement in the production of cement mortar. Diatomite was used at 0%, 5%, 10% and 15% replacement by weight for cement while sand and water quantities were kept constant. Compressive and flexural strength, freeze–thaw resistance, sulfate resistance, water absorption and dry unit weight of the mortars were determined. The compressive and flexural strength decreased with increasing diatomite content for all curing periods. However the compressive strength of the cement mortar which was produced with 5% diatomite content complied with the minimum specified value of given in the standards. Diatomite replacement generally increased the compressive strength of the cement mortar after 25 freezing and thawing cycles. Water absorption of the mortars decreased with the increase of diatomite content except the mortar containing of 15% diatomite. Dry unit weight of the cement mortar was lower than the control mortar because of high porosity of diatomite. The expansion of the cement mortar bars immersed in 5% sodium sulfate solution decreased with increasing diatomite content and generally the sulfate resistance of the mortars was higher than that of the control mortar.     

EJ系列建筑砂浆稠化粉的性能研究

EJ系列砂浆稠化粉是一种新型的水泥砂浆拌合物的添加剂 ,掺入之后不仅能改善砂浆的和易性及保水性 ,而且能明显提高砂浆的各项性能指标。本文详细地介绍了该稠化粉的各项性能指标。该产品具有很好的社会效益和经济效益     

Comparison of different methods for activation of ordinary Portland cement-slag mortars

This paper compares three methods for activation of OPC-slag mortars (OSM): (1) prolonged grinding of binders (mechanical method), (2) elevated temperature curing of mortars (thermal method), and (3) use of chemical activators such as NaOH, KOH, and Na₂SiO₃, 9.35H₂O (chemical method). The proper reactivity of OSM was evaluated using a mixture of 50% OPC and 50% slag. Early and ultimate strengths were compared. All three activation methods accelerated both the slag reaction and strength development rates. However, the chemical method did not show a significant effect on the ultimate strength, while thermal activation increased the early strength by 3 days. Mechanical activation increased the early strengths of the mortar significantly, but about 6% strength loss occurred in the ultimate strength. Although, the application of mechanical and thermal activation methods needs extra equipment and energy, due to more significant of strength improvement; based on current test results, it can be said that mechanical activation is the most efficient and feasible method for the activation of OSMs.     

Organo-modified reservoir sludge as fine aggregates in cement mortars

In Taiwan, a considerable amount of reservoir sludge is being increasingly difficult to dispose of in landfills and creates serious disposal problems. Attempts have been made to study the feasibility of using reservoir sludge as a substitute for a portion of fine aggregates in cement mortars. Reservoir sludge in Taiwan mainly composed of smectite clay is first organo-modified by a cationic-exchange reaction. The compressive strengths and permeability ratios of cement mortars with various percentages of organo-modified reservoir sludge (OMRS) particles were measured and then compared to those of plain cement mortars. The experimental results indicate that it could be possible to replace up to 30% by weight of fine aggregates by OMRS particles in a cement mortar for normal practice. Meanwhile, OMRS particles can be used in controlled low-strength materials (CLSM) if their replacement percentage for fine aggregates is higher than 80%. Also, excellent waterproof of cement mortars is achieved when the percentage of OMRS particles is within the range of 5–50%.     

Utilization of industrial wastes and unprocessed micro-fillers for making cost effective mortars

The use of fly ash, slag, silica fume and marble dust as replacement of cement on the compressive strength and cost effectiveness of low w/c ratio superplasticized portland cement mortars was investigated. The blending of industrial wastes in mortars was also studied. Cement mortars (1:3 and 1:6) incorporating various proportions of industrial wastes were designed to have a flow of 110 ± 5%. The compressive strength of mortars with and without superplasticizer was determined at 1, 3, 7, 28 and 180 days and their cost effectiveness was analyzed.     

聚苯板粘结砂浆成本优化的创新方案

纤维素醚和可再分散聚合物胶粉为聚苯板粘结砂浆提供了重要的功能。外墙外保温体系"墙-粘结砂浆-聚苯板"中最关键的是粘结砂浆与聚苯板之间的粘结。一种特殊改性的聚苯板粘结型纤维素醚Bermocoll PAD 1,特别适用于EPS外墙外保温系统的粘结砂浆。Bermocoll PAD 1除具有纤维素醚的所有功能外还可提高砂浆与聚苯板间的粘接强度。即使在低掺量的情况下,它不仅能提高新拌砂浆的保水性和工作性,同时由于独特的锚固技术还可以显著提高砂浆与聚苯板之间的原粘接强度和耐水粘接强度。     

Studies on paper mill effluent as a workability aid for cement mortars

An attempt to use paper mill effluent, which is a source of pollution, as a workability aid for cement mortars is presented. Various percentages of effluent from a medium scale unit have been studied in cement mortar as a workability aid. The effects of dosages on setting time of cement, flows, compressive strength and reduction in water content have been determined.     

Performance of limestone cement mortars in a high sulfates environment

With the aim of studying the influence of cement composition on resistance in high sulfates environment, standard mortars have been produced using ordinary Portland cement (CEM I – 32.5) and limestone cement with 35% limestone (CEM II/B-LL – 32.5). The pore size distribution of the cement pastes was measured. The mortars were immersed in a 5% Na₂SO₄ solution at 20 °C for 1.5 years and the caused deterioration was been visually observed at a regular basis. Furthermore, the mortars expansion was being estimated by measuring the change of length. At the end of the experiment the compressive strength of the mortars was measured. The deterioration products of the mortars have been identified by means of X-ray diffraction, optical microscopy and environmental scanning electron microscopy. The limestone cement based mortar presented cracking that started at the age of 6 months and continued throughout the experiment. It also displayed high expansion after 250 days of immersion in a 5% Na₂SO₄ caused, as proved using the analytical techniques, by the formation of gypsum and ettringite. Concluding, the cement with 35% limestone did not perform as well as ordinary Portland cement under the most aggressive laboratory conditions. Hence, it is obvious that the addition of limestone in the cement leads to a totally different behaviour than Portland cement with respect to the resistance in high sulfates environment.