Sustainable Concretes for Structural Applications
251
2 Materials and Methods
To explore the effects of CSA cement, GBBS and DHE steel fibers on the engineering
properties of concrete, eight different concrete mixes were developed in this study.
The concrete mixes included concretes containing 100% OPC and 100% CSA, 50%
OPC and 50% CSA, 25% OPC with 50% CSA and 25% GBBS without and with
1% DHE steel fibers. To assess the effect of curing age on the strength of concrete,
the compressive strength tests were conducted at the ages of 1, 7, 28, and 56 days.
Additionally, the splitting tensile tests were performed at 7, 28, and 56 days. All the
other features of the concretes were evaluated at 28 days.
2.1 Materials
The binder materials used in this study were ASTM Type I Portland cement; CSA
produced by Italcementi Group and ground granulated blast-furnace slag. Both natural sand, with a 2.9 fineness modulus, and crushed gravel, with a nominal maximum
size of 19 mm, were used as the aggregates at a volume fraction of 50%. To achieve
the desired workability in different concrete mixes, a Driver Care 10-Sika, was used
as a superplasticizer. Additionally, in CSA cement-based concretes, tartaric acid was
used as a retarder to increase the setting time of those mixes. Double hooked-end
(DHE) steel fibers with a 60-mm length and an aspect ratio of 65 were employed in
this study.
2.2 Concrete Mixtures and Mixing Procedure
The water-binder ratio was maintained at 0.35 and the water amount was 157 l for all
mixtures. A pan mixer was used for the preparation of all the mixes. Prior to adding
the raw materials, the surface of the pan mixer was cleaned with a wet towel to avoid
the absorption of aggregates moisture by the mixer. The mixing procedure, which
was designed by trial, was chosen as follows: initially, the fine aggregate and cement
were mixed for one minute. Afterward, approximately half of the water including SP
was introduced into the mixer; the ingredients were further mixed for two minutes.
The saturated surface dry (SSD) coarse aggregates and remaining mixing water were
then introduced and the mixing was continued for another 5 min. To fabricate uniform
fiber-reinforced concrete, discrete fibers were added gradually to the rotating mixer
and were mixed for an additional 5 min in order to obtain a homogenous concrete
mix. Details of mix proportions and the results of a slump test are summarized
in Table 1. The content of SP in that table is given as a percentage of the total
mass of the binder. To determine the workability of fresh concrete, slump tests were
performed as per ASTM C143 (2010) during the preparation of the concrete mixes.
251
2 Materials and Methods
To explore the effects of CSA cement, GBBS and DHE steel fibers on the engineering
properties of concrete, eight different concrete mixes were developed in this study.
The concrete mixes included concretes containing 100% OPC and 100% CSA, 50%
OPC and 50% CSA, 25% OPC with 50% CSA and 25% GBBS without and with
1% DHE steel fibers. To assess the effect of curing age on the strength of concrete,
the compressive strength tests were conducted at the ages of 1, 7, 28, and 56 days.
Additionally, the splitting tensile tests were performed at 7, 28, and 56 days. All the
other features of the concretes were evaluated at 28 days.
2.1 Materials
The binder materials used in this study were ASTM Type I Portland cement; CSA
produced by Italcementi Group and ground granulated blast-furnace slag. Both natural sand, with a 2.9 fineness modulus, and crushed gravel, with a nominal maximum
size of 19 mm, were used as the aggregates at a volume fraction of 50%. To achieve
the desired workability in different concrete mixes, a Driver Care 10-Sika, was used
as a superplasticizer. Additionally, in CSA cement-based concretes, tartaric acid was
used as a retarder to increase the setting time of those mixes. Double hooked-end
(DHE) steel fibers with a 60-mm length and an aspect ratio of 65 were employed in
this study.
2.2 Concrete Mixtures and Mixing Procedure
The water-binder ratio was maintained at 0.35 and the water amount was 157 l for all
mixtures. A pan mixer was used for the preparation of all the mixes. Prior to adding
the raw materials, the surface of the pan mixer was cleaned with a wet towel to avoid
the absorption of aggregates moisture by the mixer. The mixing procedure, which
was designed by trial, was chosen as follows: initially, the fine aggregate and cement
were mixed for one minute. Afterward, approximately half of the water including SP
was introduced into the mixer; the ingredients were further mixed for two minutes.
The saturated surface dry (SSD) coarse aggregates and remaining mixing water were
then introduced and the mixing was continued for another 5 min. To fabricate uniform
fiber-reinforced concrete, discrete fibers were added gradually to the rotating mixer
and were mixed for an additional 5 min in order to obtain a homogenous concrete
mix. Details of mix proportions and the results of a slump test are summarized
in Table 1. The content of SP in that table is given as a percentage of the total
mass of the binder. To determine the workability of fresh concrete, slump tests were
performed as per ASTM C143 (2010) during the preparation of the concrete mixes.