Comparison of Efficiency of Accelerating Admixtures for Concrete Using Multiple-Criteria Decision Analysis (MCDA)

Abstract

A lot of different types of accelerating admixtures for concrete are used nowadays. The aim of this paper is to determine efficiency relations between several accelerating admixtures for concrete with usage of multiple-criteria decision analysis (MCDA). Tests of cements' initial setting time, consistency and compressive strength of mortars were made. Tests of cements and fresh mortars were conducted in temperature 8°C and 20°C. Compressive strength were tested after 12, 24, 48 hours and 7, 28 days of curing. Specimens for those tests were cured in temperature 8°C in water and 20°C in climatic chamber with relative humidity 60%. Mortars were made of Portland cement (CEM I 52,5R), Portland-slag cement (CEM II/B-S) and two kinds of blast furnace cement (CEM III/A, CEM III/C). Examined admixtures were based on calcium formate, crystal seeds and calcium nitrate. All of them are described as both set and hardening accelerators for concrete. Admixtures were added in maximum dosage allowed by producer. All of admixtures caused decrease of initial setting time and increase of early compressive strength (12-48 hours) with varying degrees. Decrease of 28 days compressive strength was not noted in case of any admixture. In order to determination of efficiency relations the multiple-criteria decision analysis (MCDA) was made for every kind of cement separately. Criteria were defined on the basis of conducted tests and were divided accordingly to environmental conditions. Weights of criteria were evaluated with pair analysis method. Values of tests' results were converted with usage of Neuman-Morgenstern method. Result of analysis is sum of criteria evaluations according to their weights. Accelerating admixture based on crystal seeds in proven to be the most efficient one, while the one based on calcium formate is the least efficient of tested admixtures.