Comprehensive Analysis of the Effects of Superplasticizer Variation on the Workability and Strength of Ready-Mix Concrete

This experimental study aims to examine the influence of many crucial parameters on the workability and compressive strength of Ready-Mix Concrete (RMC). The study utilized two distinct varieties of superplasticizers obtained from the local market. The fine aggregates utilized in this study were sourced from Sylhet sand, whereas the coarse aggregates were comprised of boulder crushed stone chips. The experimental procedures adhered to the requirements outlined by ASTM. A comprehensive investigation was conducted on a range of concrete compositions that used diverse chemical admixtures. The slump test was performed at regular intervals of 15 minutes until the slump value reached or fell below 3 cm after the mixing of the concrete. In the scenario involving two-stage admixture dosage, the second stage of admixture was introduced once the slump reached or dropped below 3 cm, following which the casting process was initiated. The process of curing concrete specimens consists of two distinct stages: the main stage and the final stage. Cylindrical specimens, with a diameter of 4 inches and a height of 8 inches, were manufactured for the purpose of evaluating their compressive strength at both 7 and 28 days. During the experimental trials, the water-cement (w/c) ratio was kept consistent, while different dosages of admixture were applied. The findings of the study indicate that the utilization of a two-stage dose of admixture resulted in enhanced and extended workability, along with higher strength of the concrete in comparison to specimens that did not incorporate any admixture. This research study enhances the comprehension of optimizing qualities of ready-mix concrete (RMC) by varying the superplasticizer, providing useful insights for the building sector

COMPARATIVE ANALYSIS OF CRACKING AND RUTTING CHARACTERISTICS OF ASPHALT MIXES

Idaho mixes are typically good against rutting. It adopted Superpave design method, which was developed through SHRP program in late 1990s. Superpave mixes are described as more drier mixes than Marshall mixes. It has well rutting resistance performance, but bad cracking resistance performance. In addition, using Recycled Asphalt Pavement (RAP) as alternatives for virgin material produces stiffer mixes. Recently, more attention is paid for utilizing laboratory performance assisting tests for mixture assessments for both rutting and cracking. This study evaluates two test protocols (AASHTO T24 and AASHTO T340) for rutting and three fracture tests protocols (AASHTO TP 124, ASTM D8044, and ASTM D6931) for assessing cracking resistance of asphalt mixes. Two rutting resistance indices ( Rut depth @8000 cycle and rut depth @20000 cycles) along with six fracture performance indices were included: Flexibility Index (FI), Fracture Energy (Gf), Cracking Resistance Index (CRI), strain energy release rate (Jc), and Indirect Tension Test Strength (IDTstrength). Indices were evaluated for potential for results variability, and sensitivity for binder content, binder grade, mix type, RAP materials and increment in recycle binder replacement (RBR%). It was found that, Hamburg Wheel Tracking Test (HWTT) and Flexibility Index (FI) was able to capture the most accurate sensitivity for rutting and cracking.masters, M.S., Civil Engineering -- University of Idaho - College of Graduate Studies, 2018-1