Properties of cement mortars in fresh and hardened condition infl uenced by combined application of SCMs

Abstract

Abstractin the hardened cement paste -through pozzolanic reactions -additional hydration products can be formed by the use of supplementary cementing materials (scms). the expected results of these processes are: increase in strength, decrease in permeability and the improvement of other important durability properties. in the present research, properties of mortar mixtures were investigated with different cement substitution rates of scms both in fresh and hardened conditions. the consistence of mixtures was determined by flow table test, and the change in workability was repeatedly measured until 120 minutes. the specimens were stored in water up to the age of 7 days then under laboratory conditions (in climate chamber of 20±3°c temperature and rH=65% relative humidity) up to the age of 28 days. Afterwards half of the specimens were immersed into and stored under water and the other half was kept continuously under laboratory conditions. the properties of the hardened specimens (flexural tensile strength, compressive strength, water absorption, apparent density and apparent porosity) were investigated at the age of 28, 56, 90 days. seven mortar mixtures were made of cem i 42.5 n Portland cement with different cement substitution ratios of metakaolin (mk) and/or silica fume (sF). Quartz sand was used as aggregate with the range of 0/2 mm particle size. the results of consistence measurements showed that the flow values of the fresh mortar mixtures which contain scms are smaller comparing with the reference mixtures (without scms), since the physical properties of these materials (particle size, specific surface area, particle shape, etc.) influence the consistence. the specimens with smaller substitution ratio showed more effective utilization of scms in the view of strength. the water absorption and apparent porosity were higher, and at the same time the apparent density was smaller than those of the mixtures with higher substitution ratios.

The influence of combined application of two SCMs on the corrosion and acid attack durability of mortars

“…The reason is that the SF had the smallest particle size and the highest specific surface area comparing with the metakaolin and cement used in the experiments. The results of our previous study proved that addition of silica fume resulted in more compact microstructure in the early hydration [30].…”

“…In our previous research on these mortar mixtures, made with the same materials and mix proportions, the influences of SCMs on fresh and hardened condition were investigated [30]. Differences observed between the properties of the mixtures in the fresh condition are: (i) the addition of SCMs resulted in decrease of consistency, (ii) the change of workability in time is less pronounced for mixtures made with SCMs than that of the reference mixture.…”

“…The water absorption and apparent porosity were higher, but the apparent density was smaller than those of the mixtures with higher substitution ratios. It is important to find optimum dosage and substitution ratio, because application of SCMs over the optimum amount may reduce the performance both in strength and durability parameters [30]. After demoulding the prismatic specimens were stored in water under laboratory condition up to 7 days then in climatic chamber up to 28 days (T = 20 ± 3°C and RH = 65%).…”

Cellular concrete waste as an economical alternative to traditional supplementary cementitious materials

“…Two basic concrete mixes were used during our experiments, which are described with more details in [27,30]. The first concrete mix was designed to have a relatively low resistance against freezing.…”

Characteristics of cement pastes incorporating different amounts of waste cellular concrete powder

“…This experimental work was examined as an initial phase to PhD work for producing green self-compacting high performance concrete (GSCHPC) using different waste materials and recycled concrete aggregate, one of these waste materials is WCCP. Whereas the response of mortar systems and concrete systems depend greatly on the properties of paste materials especially in case of self-compacting concrete [13,14].…”