Effect of varying silica-limestone sand fines on the physical-mechanical performance of concrete

The use of crushed limestone sand in the concrete industry will be quite possible and imperative for environmental reasons. Many researchers around the world have found that concrete based on 50% substitution of river sand by limestone sand gives better physico-mechanical characteristics. The main objective of this investigation is to search for an optimal percentage of silica-limestone fines resulting from the substitution of half in quantity of alluvial sand by crushed limestone sand in ordinary concrete. The proportions of fines that were tested in this work are 6%, 8%, 10%, 12% and 14%. The obtained results revealed that concrete based on silica-limestone sand and containing 14% of the same type of fines strongly improves the different mechanical strengths and participates in the reduction of 10% and 13%, of the coefficient of capillary absorption and of the porosity accessible to water, respectively, compared to the control concrete. In addition, good statistical relationships between the studied parameters were also found

Effect of Using Limestone Fines on the Chemical Shrinkage of Pastes and Mortars

The main aim of this study is to examine the effect of incorporating limestone fines (LF) on chemical shrinkage of pastes and mortars. For this purpose, five paste and five mortar mixes were prepared with 0, 5, 10, 15 and 20% (by weight) LF as replacement of cement. The water to binder ratio (w/b) was 0.45 for all mixes. The sand to binder (s/b) ratio in the mortar mixes was 2. Testing included chemical shrinkage, compressive strength, density and ultrasonic-pulse velocity (UPV). Chemical shrinkage was tested each hour for the first 24 hrs, and thereafter each 2 days until a total period of 90 days. Furthermore, compressive strength and UPV tests were conducted at 1 day, 7, 28 and 90 days of curing. The results show that the long-term chemical shrinkage of pastes was found to increase with the increase in LF content up to 15%. Beyond this level of replacement, the chemical shrinkage started to decrease. However, the chemical shrinkage for mortars increased with the increase in LF content up to 10% LF and a decrease was observed beyond this level. It was also noticed that compressive strength for pastes and mortars attained the highest value for mixes containing 10 and 15% LF. The trend in the UPV results is somewhat similar to those of strength. Density for pastes and mortars increased up to 15% LF followed by a decrease at 20 % replacement level. Correlations between the various properties were conducted. It was found that an increase in chemical shrinkage led to an increase in compressive strength.

Volume Stability of Cement Paste Containing Limestone Fines

The common cause of cracking in cement paste is shrinkage due to different reasons, such as loss of water and chemical reactions. Incorporating limestone fines (LF) as a cement replacement can affect the shrinkage of the paste. To examine this effect, five paste mixes were prepared with 0, 5, 10, 15 and 20% LF as a cement replacement and with a water-to-binder ratio (w/b) of 0.45. Four volume stability tests were conducted for each paste: chemical, autogenous and drying shrinkage and expansion. Chemical shrinkage was tested each hour for the first 24 h and thereafter every 2 days for a total period of 90 days. The drying shrinkage, autogenous shrinkage and expansion were monitored every 2 days until 90 days. The results showed that replacing 15% LF enhanced the chemical shrinkage of the paste. However, autogenous shrinkage of the paste was found to increase between 0 and 10% LF and decline sharply at 15 and 20% LF. Drying shrinkage was found to increase with the increase in LF content. Expansion exhibited little variation between 0 and 10% LF and an increase for replacement above 15% LF. These results are discussed in terms of the formation of hydration products and self-desiccation due to hydration.

The Damping Effect in the Propagation of the Cracks in Fine-Grained Carbonate Concrete

The paper enlightens the connection between the specifics of the fine-grained concrete structure and the mechanics of its destruction under crack propagation with due account of damping effect of limestone fines. It is possible to obtain specific information about the ways of controlling the structure formation of concrete by finding out the relationship between the mechanism of formation, and damping mechanism of limestone additives retarding the crack propagation during consolidation and destruction of concrete.

Calcination thermokinetics of three Brazilian limestones

Limestone and lime producers inadvertently generate a considerable amount of fine material during their processing, consequently becoming a great environmental liability. As far as the industrial calcination process is concerned, there is still a need for an experimental survey on Arrhenius law parameters, as apparent frequency factor and activation energy, referring to Brazilian limestones. The knowledge of these thermokinetic parameters may contribute to energy saving during the industrial calcination process, as well as for allowing the use of limestone fines in other industrial applications. This study aimed to characterize three Brazilian limestones by focusing on their laboratory-scale calcination using both quasi-isothermal and non-isothermal methods to estimate their kinetic parameters. The non-isothermal method (by thermogravimetric analyses) allowed estimating the activation energy for each limestone through the high calcination rate ranges. However, the kinetic parameters estimated by the quasi-isothermal method turned out in lower values, indicating the need to control the reactor atmosphere.

Effect of Sugarcane Bagasse Ash and Lime Stone Fines on the Mechanical Properties of Concrete

Cement production releases huge amounts of carbon dioxide having a significant impact on the environment while also having huge energy consumption demands. In addition, the disposal and recovery of natural concrete components can lead to environmental degradation. The use of waste in concrete not only reduces cement production, but it also reduces energy consumption. The aim of this study is to evaluate the properties of fresh and hardened concrete by partially replacing cement with sugarcane bagasse ash (SCBA) and limestone fines (LSF). In this investigation work the cement was replaced with SCBA ash and LSF by 0% (0% SCBA+ 0% LSF), 5% (2.5% SCBA+ 2.5% LSF), 10% (5% SCBA+ 5% LSF), 15% (7.5% SCBA+ 7.5% LSF) and 20% (10% SCBA+ 10% LSF) by weight of cement. In this regard, a total of 60 samples of concrete specimens were made with mix proportion of 1:1.5:3 with 0.56 water-cement ratio. Cube specimens were tested for compressive strength and cylindrical specimens were used for determining splitting tensile strength at 7 and 28 days respectively. The optimum result displayed that the crushing strength and split tensile strength increased by 10.33% and 10.10% while using 5% SCBA+ 5% LSF as a substitute for cement in concrete after the 28th day. The slump value of concrete declined as the content of SCBA and LSF increased.