Papers by Keyword: Aggregate

Abstract: The results of the investigation of new surfactant additives for concrete are given in the article. Their values of density and surface tension are determined at temperatures of 10-50 oC in steps of 10 degrees. Dependences of the surface tension on temperature, the dependence of density on temperature, the dependence of the surface tension on the density for six types of additives for concrete are obtained.

Abstract: The article is devoted to the effect of surface-active substances on the interface of phases. The hydrophobization and hydrophilization of surfactants, their role in building composites are considered. The dependence of the surface tension on temperature, the dependence of the density on the temperature of various kinds of additives for concrete, is given.

Abstract: This paper deals with the influence of the coarse aggregate grain size on the frost resistance of concrete. For the purpose of the experiment, three types of concrete were produced, varying only in the maximum grain size of the used natural aggregate. The evaluation of the frost resistance of concrete is based on non-destructive (NDT) dynamic and static testing methods. The results of the experiment indicate influences of the aggregate used in the production of the concrete on the results of its frost resistance.

Abstract: In contrast to foreign practice, in Poland, for many years, there has been a belief, that in prestressed constructions, more expensive concretes on basalt aggregates should be applied. This habit is due to the low quality of national river and fossil aggregates. They allow to obtain low concrete strength and modulus of elasticity. In the paper, basing on two examples of post-tensioned slabs, it has been shown, that it is possible to use concretes with a low value of modulus of elasticity for large-span slabs. These results may be significant in popularizing the use of post-tensioned slabs in buildings in poorer countries, making them cheaper in execution.

Abstract: In the current restoration practice, the mortars based on aerial or hydraulic lime with siliceous aggregate are used on repair / reconstruction of historical plasters. The resulting properties of lime mortars do not depend only on the type of aggregate, but also on its contamination, origin and a degree of hardening. For this reason, it is needed to know a detailed characteristic of the aggregate and the results obtained for the particular aggregate cannot be generally applied for the similar type of aggregate. This work presents the applicability of Czech local crushed limestone aggregate and limestone fines as a filler to natural hydraulic lime-based mortars. The role of aggregate and limestone fines on the properties of mortars is examined by comparing the mechanical strengths, porosity and frost resistance of the mortars with pure quartz sand and limestone aggregate and its quantity in the mortar. It was found that the limestone aggregate has produced lower strengths, higher total porosity of natural hydraulic lime-based mortars. It has resulted in low frost resistance of the mortars.

Abstract: Pervious concrete primarily is used as a means of storm water management. Taking into consideration the environment issues, the binder can also be formed by partially replaced Portland cement by cementitious materials, such as blast furnace slag fine powder, fly ash and silica fume. The combination of the binder materials was determined based on previous work, which composed of 56% Portland Composite Cement, 15% fly ash Type F, 26% air-cooled blast furnace slag from a local steel Industry and 3% condensed silica fume. The compressive strength of specimens with coarser aggregate was lower compared with the control pervious concrete, but still within the range of the requirement compressive strength according to ACI 522R-2010. The difference of the aggregate size affected the enhancement of the compressive strength. The flexural strength of pervious concrete with aggregate size of 9.5mm-12.5mm tend to be higher compared with that of pervious concrete with smaller aggregate size. Furthermore, the addition of 6% natural fine aggregate while applying higher water/cement ratio could be a contribution to the enhancement of the compressive and the flexural strength.

Abstract: This study deals mainly with the mix proportions using granite and unwashed gravel as coarse aggregate for self-compacting concrete (SCC) and its workability, by considering the water absorption of unwashed gravel aggregate. Mix proportions for SCC were designed with constant cement and fine aggregate while coarse aggregates content of granite-unwashed gravel combination were varied in the proportion 100%, 90%/10%, 80%/20%, 70%/30%, 60%/40%, 50% /50%, represented by SCC1, SCC2, SCC3, SCC4, SCC5 and SCC6. 100% granite (SCC1) serves as the control. The workability of the samples was quantitatively evaluated by slump flow, T₅₀₀, L-box, V- funnel and sieve segregation tests. Based on the experimental results, a detailed analysis was conducted. It was found that granite and unwashed gravel with SCC1, SCC2 and SCC3 according to EFNARC (2002) standard have good deformability, fluidity and filling ability, which all passed consistency test. SCC1, SCC2 and SCC3 have good passing ability while all mixes were in the limit prescribed by EFNARC (2002). It can be concluded that the mix design for varying granite-unwashed gravel combination for SCC presented in this study satisfy various requirements for workability hence, this can be adopted for practical concrete structures.

Abstract: The lime addition in the mix asphalt became nowadays an innovative technique in the field of infrastructure. The objective of the experiences is to improve the durability of roads, especially in the United States and in Europe. In Morocco, this aspect remains in the reflecting phase, a part from some simple experiences; this technique allows, from a precise dosage of lime, to increase the service life of roads, and to optimize the maintenances costs caused by the damages.

Abstract: Lime mortars represent indispensable building materials that have been used for centuries in civil engineering. Considering the necessity of numerous restoration work on historical buildings, a research of the applicability and suitability of various types of plasters for repairing the historical plasters has been developed. This work presents the applicability of limestone aggregate and limestone fines to aerial lime-based mortars. The role of aggregates on the properties of lime mortars is examined in this paper by comparing pure quartz sand and limestone aggregate and its quantity in the mortar. It was found that limestone aggregate produced the comparable or higher mortar strengths than quartz aggregate and slightly increased porosity, water absorptive capacity and carbonation rate of the mortars. Partially replacement of aggregate by limestone fines has caused dramatic growth in strength, especially in mortars with high content of binder. The applied limestone aggregate is convenient to lime-based mortars and the addition of limestone fines contributes to better mechanical properties of lime mortars.

Abstract: Economic and environmental issues are directly related to industrial processes which, not only employ natural resources but also generate by-products that may impact the environment. In order to achieve sustainable development, reducing the use of natural resources and lowering cost through adequate destination of waste becomes a crucial issue. The aim of this paper is to analyze the suitability of reusing waste (wood ash) resulting from the combustion process at wood product industries for manufacturing cement based materials used in civil engineering. The material assessed is ash from the combustion process of a wood product industry. In this study, physical and chemical properties such as grain size, mineral and chemical composition of this by-product were characterized. Thermal analysis and X-ray diffraction techniques were used for this purpose. Preliminary results show the suitability of using the waste (wood ash) for manufacturing cement based materials