Powder-type SCC with crushed mineral aggregates

Design concept and flow properties of SCC – Part 2

Fig. 1 Schematic representation of the “shear resistance” of an aggregate mix depending on water content. In this diagram, the minimum water amount w_min characterizes the conversion of the particle mix to a suspension (taken from [6]).

Fig. 2 Example of a power measurement during the SCC mixing process while adding water up to an amount in excess of w_min, and subsequently adding a plasticizer (PL).

Table 1 Mix composition (actual composition) of the SCCs tested, including gravel (K), quartz porphyry chippings (Q),
shell limestone chippings (WI), fluvial sand (-F) and crushed quartz porphyry sand (-Q).

Fig. 3 Photographs of the automatic slump table with the sensors arranged diagonally on the table to capture the slump curve of the SCC with (right) and without (left) blocking ring.

Fig. 4 Photograph and drawing (taken from [12]: abrams cone put overhead by the author ) of the setup to measure the difference in height within/outside the J-ring (st_J).

Fig. 5 Test results for the blocking step (st_J) recorded when varying the paste volume. Additions: CFA (left); LSD (right). Parameters: sf_B…slump flow without J-ring; Δsf_B…difference of slump flow with and without J-ring; t_VB…V-funnel flow time; d_Leim…paste layer thickness (spherical).

Fig. 6 Results of the rheological test performed in the BTRHEOM while varying the paste volume (addition: CFA). Parameters: sf_B slump flow without J-ring; Δsf_B…difference of slump flow with and without J-ring; t_VB…V-funnel flow time; d_Leim…paste layer. thickness (spherical).

Fig. 7 Results of the rheological test performed in the BTRHEOM while varying the paste volume (addition: LSD). Parameters: sf_B…slump flow without J-ring; Δsf_B…difference of slump flow with and without J-ring; t_VB…V-funnel flow time; d_Leim…paste layer thickness (spherical).

Fig. 8 Flow curves recorded during the slump test in accordance with the SCC Guideline [2] for the SCCs with gravel/fluvial sand (K-F), quartz porphyry chippings/fluvial sand (Q-F), shell limestone/fluvial sand (WI-F) and quartz porphyry chippings/crushed sand (Q-Q) when varying the paste volume with (d,J) and without (d) blocking ring. Time recording started when the slump diameter reached
400 mm. Concrete additiion CFA.

Fig. 9 Flow curves recorded during the slump test in accordance with the SCC Guideline [2] for the SCCs with quartz porphyry chippings/fluvial sand (Q-F) and quartz porphyry chippings/crushed sand (Q-Q) when varying the paste volume with (d,J) and without (d) blocking ring. Time recording started when the slump diameter reached 400 mm. Concrete additive: LSD.

Fig. 10 Bingham body created by a parallel arrangement of a friction element (St. Venant element) and a damping element (Newtonian element).

Fig. 11 Diagram of flow velocity v(s), or flow acceleration a(s), as a function of the flow path in the slump test from a radius of 200 mm.

Fig. 12 Diagram showing the slump flow coefficient b resulting from the analysis of the flow curves during the slump test without J-ring in relation to the plastic viscosity h_pl,HB-B derived from the flow curves recorded in the BTRHEOM rheometer test. All 41 pairs of values are shown that were verified as part of the tests.

Fig. 13 Slump flow coefficients b and plastic viscosity values h_pl,HB-B as a function of paste layer thickness d_Leim for the tested SCCs with gravel/fluvial sand (K-F), quartz porphyry chippings/fluvial sand (Q-F), shell limestone/fluvial sand (WI-F) and quartz porphyry chippings/crushed sand (Q-Q), as well as with CFA and LSD as addition.

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The first half of this two-part article presented an approach to determining the volume of the cement paste required to produce SCC whilst considering the granulometric characteristics of the aggregate mix. On this basis, the second part deals with the mix design and the flow properties of SCC of the powder type. Starting from the required amount of cement paste determined in tests, the concept for the design of powder-type SCC mixes is introduced. Moreover, the fresh concrete characteristics of the SCCs produced according to this design concept are examined. In this regard, the article concentrates on describing the flow properties documented during the slump test and the correlation to the plastic viscosity measured in the rheometer.

Powder-type SCC mix design

To produce the SCCs under study, the above-described aggregate mixes consisting of gravel and fluvial sand (K-F), quartz porphyry chippings and fluvial sand (Q-F), shell limestone chippings and fluvial sand (WI-F) and quartz porphyry chippings and crushed sand (Q-Q) were used with a ratio of particles smaller than 4 mm in size that amounted to approx. 50 percent by mass (ABB 16 grading curve). The mix was determined using the known material volume calculation by defining the cement paste volume and the volume-related cement/additive and water/powder ratios (V_W/V_M)....