Use of limestone Filler in HPC to improve passing ability property

Table of Contents

Chapter 1: The Use of limestone Filler in HPC to improve passing ability property. 3

1.1 Introduction. 3

1.2 Research Methodology (Approach) 4

1.2.1 Materials. 4

1.3 Mixing procedure for Concrete performance tests. 4

1.4 Test methods for concrete performance analysis. 5

1.4.1 Flowability (Slump-flow SF) 5

1.4.2 Slump-flow with J-ring test SFJ (passing ability by J-ring PJ) 5

1.4.3 Passing ability (L-box test PL) 5

1.4.4 Stability (segregation resistance SR) 6

1.5 Design of concrete mixes. 6

1.6 Results and discussion. 8

1.6.1 Slump-flow (with and without J-ring) and segregation. 8

1.6.2 Passing ability by J-rings and L-box. 12

1.6.3 Passing ability and flowability-segregation correlation. 14

1.7 Conclusions. 17

Chapter 1: The Use of limestone Filler in HPC to improve passing ability property

1.1 Introduction of Use of limestone Filler in HPC to improve passing ability property

In recent years, the need to come with a possible alternative type of concrete to reduce building materials' impact on the economy, energy, and environment has attracted many scientists to investigate. Self-consolidating high-performance concrete (SCHPC) is one of these types of concrete that efficiently use the natural resources available locally to produce high passing ability and dimensional stable concrete. Assumed that the dominant and traditional binding material in the concrete structure is cement, and with the extensive use of this expensive binder on the consumer as well as on the planet, it is encouraged to reduce the amount of this binder used in the concrete mixture by natural and local fillers. One of these inert fillers, as suggested by [1] is limestone (LS). Limestone can be one of the most worthwhile filler to add for three reasons:

1.      reducing carbon dioxide emission

2.      lowering the cost associated with saving energy in producing cement clinker

3.      limestone is generally available in the cement quarries which make it easier for the majority of cement manufacturers to handle [2]. Limestone fine filler also has a particle size distribution finer than cement particle size, which makes it perfect to substitute cement.

To increase the passing ability of concrete, the flow-ability should be increased, and segregation should be decreased, or in another meaning, cohesiveness should be increased. These contradictory properties can initiate the variability on the exact relationship between passing ability, segregation stability and durability properties of high-performance concrete. For example, adding water or SP increases the flowability but also increases segregation. Furthermore, adding fine materials decreases segregation, but it decreases flowability. The design of this concrete mix is indirect due to the flow ability and segregation are two opposing performance properties of concrete because any change in the design mix that improves one of these characteristics will actually undermine another. These properties are very vital especially in extreme climatic condition where transportation, handling, pumping, placing and finishing of concrete is an issue that needs to be considered. In-depth, dealing with the different environmental climatic conditions when it comes to high-performance concrete is an important concern for users willing towards utilizing environmentally friendly materials as a partial replacement for Ordinary Portland Cement (OPC). Overall, it is encouraged to help the concrete industry in reducing the amount of cement used in structural projects, which can save building materials cost, production energy, and sustainability in delivering an optimal concrete quality.

As an experimental investigation in this chapter, a scientific mixing design of Self-Consolidating High-Performance Concrete (SCHPC) incorporating non-cementitious limestone filler is developed to understand the behaviour of superplasticizer’s addition mixture on fresh concrete properties. Considered, two groups of concrete were tested, Group A is the first which is the reference mixes with cement only as a powder, Group B is the second when limestone filler substitute cement in the concrete powder composition with three different replacement ratios 15 percent, 25 percent, and 35 percent. The properties of each concrete mix were measured regarding flowability, segregation stability and passing ability then compared to each other; both single and concurrent performance comparison was considered. In summary, many interesting results indicating the competence of advocating limestone filler in advancing the rheological performance of concrete as a partial replacement of cement volume. Additionally, passing ability and concurrent flowability-segregation resistance performance can be connected in a positive relationship.

1.2 Research Methodology (Approach) of Use of limestone Filler in HPC to improve passing ability property

1.2.1  Materials of Use of limestone Filler in HPC to improve passing ability property

Please refer to 3.2

1.3 Mixing procedure for Concrete performance tests of Use of limestone Filler in HPC to improve passing ability property

The prepared dry ingredients, including powder and aggregates, were mixed for 2 min in the pan mixer. Then water was added, and the ingredients were mixed for 3 min before the SP was added. After adding the SP, the mixture would be mixed for 5 min before the concrete performance tests were performed. The total mixing process normally took less than 15 min to complete. Tests on fresh concrete were performed immediately after mixing and were carried out in the following order: slump flow test without J-ring, slump flow and passing ability test with J-ring, L-box test then segregation test.  Concrete used for slump flow test was put back into the mixer, and the whole batch was remixed to eliminate the thixotropic behaviour.  Remixed concrete was used for J-ring, L-box and segregation tests. All of the tests were repeated two times, at least to ensure reliable reading obtained.

1.4 Test methods for concrete performance analysis of Use of limestone Filler in HPC to improve passing ability property

1.4.1 Flowability (Slump-flow SF) of Use of limestone Filler in HPC to improve passing ability property

Flowability is the primary property governing fresh concrete properties, which can be tested by the Slump-flow test. This test is simply pouring the concrete by scope in the normal slump cone with no vibration until its full then lifted it upwards in one movement. The time from starting an upward movement of the cone to the time when the concrete has reached a diameter of 500 mm on the baseplate was measured, and it represents the flow time t₅₀₀. Then, measuring the diameter of the liquid slurry in two points perpendicular to each other until the point where the spreading of aggregate stops on the baseplate. The slump-flow SF will be the average of these two diameters. Also, the flow time could be an indication of the relative viscosity and flow speed of the fresh concrete mixture. The slump flow test carried out in general accordance with BS EN 12350-8 (2010) [3].

1.4.2 Slump-flow with J-ring test SFJ (passing ability by J-ring PJ)

The J-ring test will be taking place in combination with the slump flow test except before filling the slump cone with the fresh concrete mixture, the J-ring, made of a ring of evenly spaced vertical smooth reinforcing bars, needs to be placed outside the slump cone concentrically. In the beginning, the concrete allowed to cross the bars and freely flow toward the edge of slump baseplate. Then, the average of the level differences between the concrete surface and top edge outside of J-ring at four orthogonal point’s and at the center of the J-ring) apparatus measured and specified as J-ring passing ability PJ. The J-ring test used to evaluate the passing ability of fresh concrete mixture when obstructed by vertical reinforcing bars of desired size and spacing without blocking. From the same test, both J-ring flow time t500J and J-ring flow spread SFJ could also be obtained and calculated as discussed before in the slump flow test. J-ring test will be performed according to BS EN 12350-12 (2010) [4].

1.4.3 Passing ability (L-box test PL) of Use of limestone Filler in HPC to improve passing ability property           

The passing ability property will be measured by the L-box test, which is a test that would be carried out incompatibility with BS EN 12350-10: 2010 [5]. L-box is “L” shaped rectangular container that allows fresh concrete mixture to flow from a vertical section into a horizontal section through the gaps between reinforcing bars of specified size and spacing [6]. To stimulate the blockage action of reinforcing bars, three 12 mm diameter steel bars spaced at 41 mm, and sliding gate between the two sections is present. In detail, the vertical section during the test usually filled to the top with concrete mixture. Then after about 1 min, the sliding gate moved up to allow the mixture to flow from vertical to horizontal section through the gaps between reinforcing bars. The height of the concrete volume in the vertical component measured and tabulated as and the height of the concrete volume at the end of the horizontal component measured and tabulated as. The following ratio is a measure of the passing ability of concrete mix through a tight opening between reinforcing bars without segregation or simply L-box test ratio:

1.4.4 Stability (segregation resistance SR) of Use of limestone Filler in HPC to improve passing ability property

The filter segregation test was carried out as per BS EN 12350-11 (2010) [7]. Directly after mixing, nearly 10L of concrete mixture poured into a plastic bucket container and kept without disturbance resting into a stable service. Then after 15 min of waiting, to allow settlement of the aggregate particles to the bottom to take place, the bucket container was taken to sieve segregation test. About 5kg of this mixture was carefully poured on a sieve with a 5 mm square opening with the top of sample container height above the sieve by around 500 mm. The concrete paste then allowed 2 min to pass through the sieve opening if it does not stick to the aggregate and collected by a receiver underneath the sieve. The collected paste was weighed, and the segregated portion SR (wt. %) was calculated as the percentage of the weight of materials passing through to the total weight of concrete placed on the sieve.   

1.5 Design of concrete mixes of Use of limestone Filler in HPC to improve passing ability property

In general, the particle size distribution of concrete materials in this mix design studied deeply and chosen to be very diverse to fill the gaps to reach the optimum particle packing density. This variety in particle size distribution saves excess paste not only to cover the aggregate particles but also to make the mixture movable and manageable regarding concrete flowability. It is already proven that adding fillers can result in reducing the thirsty of the particle to more water and paste content, which might lead to a positive effect on short and long concrete properties.

In this mix design, all the concrete mixes were designed to have a volumetric fraction of paste at 0.4.  The rest of the volume was filled with aggregate out of which 40 vol. percent was fine aggregate and 60 vol. percent was coarse aggregate. The W/C ratio was fixed at 0.4 by weight such that the ratio of water to cementitious materials is kept constant for all mixes, and any variation on the flowability and segregation performance will not be due to the volume change of water.

One type of fine powder, namely LS, was adopted in this test program to investigate their effect on the consistency and stability performance of concrete. LS is slightly finer than cement, and thus, it can improve the wet packing density slightly.  It does not hydrate with water but merges physically with other fine materials and water to form powder paste, which can increase the cohesiveness of concrete.

Table 2 Composition of concrete mixes

Table ‎1‑1: Composition

Group	Mix Name	W/C	Composition of Powders (vol. %)		Composition of Aggregates (vol. %)		SP (%)
			Cement	Limestone	Coarse	Fine
A	R1	0.4	100	-	60	40	0.75
	R2	0.4	100	-	60	40	1
	R3	0.4	100	-	60	40	1.25
	R4	0.4	100	-	60	40	1.5
	R5	0.4	100	-	60	40	1.75
	R6	0.4	100	-	60	40	2.25
B	LS1	0.4	85	15	60	40	2
	LS2	0.4	85	15	60	40	2.5
	LS3	0.4	85	15	60	40	3
	LS4	0.4	85	15	60	40	3.5
	LS5	0.4	85	15	60	40	4
	LS6	0.4	75	25	60	40	2
	LS7	0.4	75	25	60	40	2.25
	LS8	0.4	75	25	60	40	2.5
	LS9	0.4	75	25	60	40	2.75
	LS10	0.4	75	25	60	40	3
	LS11	0.4	75	25	60	40	3.25
	LS12	0.4	75	25	60	40	3.5
	LS13	0.4	75	25	60	40	3.75
	LS14	0.4	75	25	60	40	4
	LS15	0.4	65	35	60	40	2.75
	LS16	0.4	65	35	60	40	3
	LS17	0.4	65	35	60	40	3.2
	LS18	0.4	65	35	60	40	3.4
	LS19	0.4	65	35	60	40	3.6
	LS20	0.4	65	35	60	40	4

 

1.6 Results and discussion

1.6.1 Slump-flow (with and without J-ring) and segregation

Figure 3 shows the variations of normal slump-flow without J-ring for all mixes versus the SP dosage expressed in percent to powder weight ratio (i.e., cement and LS) (%). These slump-flows values are presented in table 3 and approximately ranged from 500 to 800mm. From Figure 2, it is obvious that the concrete mixes that include limestone filler in its powder composition require a slightly higher range of SP addition for the same diameter of slump flow than the mixes that include only cement as a powder.

There are two reasons for the increased demand of SP to reach similar slump flow in Group B. First, LS is non-cementitious and was excluded in the W/C, which was kept constant in this study. Hence, free water was decreased, and more SP was required to disperse better and reduce the agglomeration of the powders. Second, LS is finer in size than cement, and it increases the total surface area of the powder. Since the mechanism of SP to reduce agglomeration is by adsorbing to the surface of fine particles, the SP demand increases as finer limestone is added.

Figure 3 shows the change of slump-flow ratio SFJ-ring/SF for all mixes versus the SP dosage expressed in percent to powder weight ratio (i.e., cement and LS) (%). In Figure 3, it shows that the range for slump flow ratio approximately between 0.6 and 0.99, which means that the difference between measuring flowability by SF and SFJ is reducing the slump flow diameter by too much or a little bit, respectively. The slump-flow ratios for all tested concrete mixes are listed in a separate column in Table 3.

Table 3 Slump-flow, passing ability and segregation of tested concrete mixes

Group	Mix Name	Slump Flow			Passing ability		Segregation SR (wt. %)
		SF   (mm)	SFJ-ring (mm)	SFJ/SF	PJ (mm)	PL-box
A	R1	350	300	0.86	N/A	0	0
	R2	490	410	0.84	120	0.13	0.8
	R3	650	430	0.66	90	0.29	1.5
	R4	690	480	0.70	70	0.41	3.1
	R5	700	435	0.62	62	0.53	5.2
	R6	700	695	0.99	50	0.61	11.9
B	LS1	790	700	0.89	20	0.58	7.2
	LS2	780	730	0.94	14	0.81	7
	LS3	765	685	0.90	10	0.85	7.9
	LS4	745	665	0.89	24	0.75	18.8
	LS5	745	675	0.91	30	0.4	33.5
	LS6	490	285	0.58	65	0.15	0.1
	LS7	610	485	0.80	54	0.41	0.2
	LS8	695	595	0.86	34	0.57	0.2
	LS9	720	645	0.90	25	0.89	0.3
	LS10	755	665	0.88	7.5	0.95	0.8
	LS11	765	705	0.92	10	0.95	1.5
	LS12	765	730	0.95	20	0.82	4.3
	LS13	770	730	0.95	30	0.77	6.1
	LS14	780	755	0.97	51	0.14	8.2
	LS15	740	690	0.93	30	0.42	2
	LS16	750	695	0.93	16	0.65	2.2
	LS17	755	705	0.93	16	0.8	5
	LS18	770	715	0.93	25	0.65	6.7
	LS19	775	670	0.86	30	0.57	8.9
	LS20	780	670	0.86	40	0.48	12.1

 

 

Figure 2:  Slump-flow Versus SP dose

 

Figure 3: Slump-flow Ratio versus SP dose

Figure 4 shows the difference between segregation ratios SR versus SP dosage (%). Both tables 2 and 3 presented the values of these parameters. From Figure 4 it is evident that segregation of concrete increased gradually at the beginning at low SP dosage and more significantly at high SP dosage. The turning points for Group A concrete were at lower SP dosage from 1.5-2 percent, whereas for Group B concrete, these turning points were at higher SP dosage from 3-3.5 percent. The reason for the more gradual increase in the initial segregation is that not all the fine powder was adsorbed by SP and thus not well distributed. After reaching the turning points as mentioned above, fine particles were much better dispersed. Further addition of SP would adsorb more efficiently on the fine particles and hence an increased rate of segregation. The SP dosage at the turning point is larger for Group B concrete because of three reasons: (1) The total surface area of powder in Group B increased due to the fine particle size of LS. Thus, more SP was needed to adsorb to the powder to disperse well the particles; (2) The mixture in Group B contains less free water because LS was added as a partial replacement of cement and not taken into account when calculating W/C ratio. Hence, hydration rate was slower, which produced less Ca2+ (due to ettringite) on the surface of cement particles resulting in less efficient adsorption; (3) Fine materials increase the viscosity of the mortar as well as that of the paste [8, 9].  Limestone being finer than cement yields a more viscous paste, and thus reduces flowability of paste and mortar [10, 11]. This enabled the paste or mortar to hold the aggregates and required a more considerable force to separate the paste or mortar from the aggregates, which would need more SP polymers to create a more significant electrostatic repulsion.

To investigate the effect of SP dose on segregation of concrete mixes with the various percent of limestone addition, a range of about 25 points of acceptable and less than the maximum SR=20 percent segregation limits by The European Guide for Self-compacting Concrete (2005) was obtained in this study. In detail, it can be revealed that the optimum limestone addition percent as a replacement of cement is about 25 percent with respect to segregation resistance because 15 percent and 35 percent produced a higher amount of mortar dripping out of the segregation sieve as shown in Figure 4. It is now clear that concrete with limestone filler needs more SP to increase flowability and influenced by the filler quantity substituting cement, while segregation index can be above or below the reference mixes. Since the passing ability of concrete being subject to both flowability and segregation stability, the addition of limestone filler and/or SP can be controversial for passing ability of concrete.

 

Figure 4: Segregation versus SP dose

1.6.2 Passing ability by J-rings and L-box

In an explanation to discuss the influence of adding SP and limestone filler on the passing ability of concrete, the test results obtained for Groups A and B concrete from L-box and J-ring are studied. The test results for Group A is showing too low slump flow for the mix R1 which makes it unreliable to represent passing ability by J-ring (PJ). So, in this study passing ability is better to be represented by L-box (PL) as it is formulated in Table 3. Both figures 5 and 6 show respectively the variations of passing ability obtained by J-ring (PJ by Eq. 1) and L-box (PL by Eq. 3) against the dosage of SP stated in percent to powder weight ratio (i.e. cement and LS) (%). It can be understood from Figure 5that the passing ability increases (indicated by a decrease in PJ) initially as SP dosage increases until reaching a minimum PJ value around 10 mm then it decreases (indicated by an increase in PJ) as SP dose continues to increase. In practice, this means that when the difference between the level of concrete inside and outside the J-ring is minor that, concrete can pass very easily through J-ring reinforcement bars outside, making it possible to reach the corner of the framework. It is also indicated in Table 3 and Figure 5 that adding limestone filler will improve the passing ability of concrete in general trend by using J-ring passing ability measurement.

From Figure 6, a related point to consider is for values of PL ≥ 0.8; these values indicate a high passing ability is meeting what is recommended by The European Guides for Self-Compacting Concrete (2005) for the passing ability criteria range used to the production of self-compacting concrete. The obtained maximum passing ability (PL), as presented in Table 3, depends on the ingredients of the concrete mixes in Table 2. It is detected that the maximum passing ability PL attained increases dramatically when limestone filler is added to the concrete mix for replacing an equal volume of cement in Group B. Amongst these maximum passing abilities, the one with 25 percent LS replacement of cement is the highest, followed by 15 percent LS replacement of cement, then by 35 percent LS replacement of cement and finally concrete with no filler. It can also be extracted from Figure 5, 6 and Table 2 that the respective SP dosage required to reaches the maximum passing ability by both measures PJ-ring and PL-box is about 2 percent SP addition for concrete mixes that include no filler in their powder compositions and around 3-3.5 percent SP addition for concrete mixes with limestone filler. These accumulating results are adding more assurance to the data obtained here for passing ability.

The rise in the passing ability when limestone filler substitutes cement in concrete mixes can be best described by the wet packing density theory proposed by Wong and Kwan (2007a). This can be explained by the improvement in the filling effect when the finer filler was added, filling up the interstitial void that increases the wet packing density of concrete [13, 14]. For that reason, the maximum passing ability increases [15], as LS is finer than cement in Group B concrete. In comparison with the reference mixes, 25 percent LS filler mixes can achieve the maximum wet packing density by falling between not enough 15 percent LS and excessive 35 percent LS amount of fine filler compared to concrete mixes with 0 percent filler and loosened structure.

 

Figure 5: J-Ring Passing Ability versus SP dose

 

Figure 6: L-Box Passing Ability versus SP dose

1.6.3 Passing ability and flowability-segregation correlation

It was revealed from the above results and discussion that to restore flowability after substituting part of cement content by limestone filler, Superplasticizer needs to be present by a slightly surplus amount. This additional SP could initiate the chance of concrete segregation. So, the outcomes can be one of these conditions. When the increase in flowability is more than that in segregation, the concrete turns out to be more workable and stable, which adds to the passing ability. Otherwise, the concrete turns into less workable and stable, which deteriorates the passing ability? Consequently, when cement substituted by limestone filler in concrete mixes, it can be claimed that rises in passing ability are not granted when a high dosage of SP added. For concrete to have the high passing ability, the concrete mortar should be consistent and homogeneous enough to move the coarse aggregate during the flow through the narrow reinforcement gap without flow separation such that the coarse aggregates will not be residual and block the gap in the passing ability apparatuses. Additional, it needs to be able to flow freely after passing through this reinforcement gap. Therefore, the passing ability of concrete should be well interconnected to the performance of flowability and segregation of concrete, which indicates the maximum limits of flowability and segregation resistance that can be achieved concurrently. This can be achieved by growth in flowability-segregation performance through (1) An increase in flow ability at given segregation; (2) A decrease in segregation at a given flowability; or (3) An increase in both flowability and segregation. All the above measures will enhance the stability and passing ability of concrete flowing through the narrow gap and beyond in J-ring and L-box passing ability determining tests.

To study the flowability-segregation performance of concrete, the slump-flow of concrete (SF), which is the nominated indicator for flowability in this study, was plotted versus the sieve segregation ratio (SR) in Figure 7 for all concrete mixes in Group A and B. It is clear from Fig. 7 that concrete slump flow increases gradually in the beginning as segregation increases slowly, then eventually reaches the maximum flowability and leveled off, for whatever segregation was obtained. In detail, the greatest slump flow diameter achieved in Group A is about 700mm with respective 12 percent SR. When limestone filler is added in Group B, around 765mm was able to accomplish for slump flow with lower segregation performance, which was 1.5 percent SR for 25 percent limestone replacement ratio. For more illustration In Figure 8, the passing ability for all concrete mixes in Group A and B by using L-box test were plotted versus the sieve segregation ratio (SR) for investigating passing ability and flowability-segregation correlation. Evidently, these graphs show that by adding finer limestone filler into concrete to substitute cement, the possible maximum flowability of concrete can be reached at a lower segregation performance or higher cohesiveness of concrete. As mentioned before, lowering segregation at a given flowability could improve the passing ability of concrete, although, with a larger dosage of SP needed, it is now almost certain that the concurrent flowability-segregation performance can be correlated to the passing ability of concrete. The performance of concrete with LS = 25 percent is seen to be the highest, followed by LS = 15 percent, then by LS = 35 percent and lastly followed by concrete with no filler, which is in the same order of their passing ability (PL) as shown in the comparison between Fig. 7 and 8. Accordingly, it confirms that passing ability of concrete can be represented by the performance of flowability and segregation. In addition, Figure 6, 7 and 8 also reveal that even though a higher dosage of SP is added to restore flowability of concrete when LS is used as fine filler, it does not have a precarious effect on the passing ability of concrete if the SP dosage is not too excessive to cause flow separation in concrete.

Overall, it is noticeable that the optimum substitution of cement by limestone filler is located when LS=25 percent in Group B with relatively small segregation effect SR, at the corresponding maximum passing ability and slightly more SP dose as it is obvious from the data presented in Table 2, 3 and Figure 8. It is accounted for the reason to have a better passing ability; concrete needs to be very cohesive and stable for the mortar to hold the coarse aggregate firmly when passing through the narrow gap, and therefore, it must have low segregation. This range of limestone filler replacement addition and segregation percentage can be taken as one of the essential mix design guidelines for producing concrete with the high passing ability for W/C=0.4.

 

Figure 7: Slump-flow Versus Segregation

 

Figure 8:L-Box Passing Ability versus Segregation

1.7 Conclusions of Use of limestone Filler in HPC to improve passing ability property

In this paper, non- cementitious and inert limestone fine filler substitute an equal volume of cement in concrete mixes by three replacement ratios (15 percent, 25 percent, and 35 percent). These powder compositions were studied for their passing ability in comparison with cement only powder concrete mixes. In each concrete group, a suitable number of concrete mixes samples were prepared with altered SP dosage to investigate the passing ability, flow-ability, and segregation resistance performance. The following points can be extracted out from the outcomes of this study:

1) When fine limestone filler is added to the concrete, with a purpose to replace cement, more SP dose was needed to restore the flowability and to prevent segregation from happening in concrete.

2) J-ring test that passing ability apparatus might give a misleading result when slump-flow is too low. Therefore, it is better to use the L-box test for passing ability reading.

3) There is an increase in passing ability when fine limestone filler substitutes an equal volume of cement in concrete mixes. One of the reasons is due to having a better packing density in concrete mixes with LS caused a more excess paste coating around aggregates.

4) In this study, standard slump flow (SF) without J-ring is used to represent flowability in general.

5) Initially, at low SP dosage passing ability of concrete increases and reaches the maximum while segregation increased slowly. Then, a further increase of SP could cause passing ability to drop and result in a more considerably increase in flow separation of concrete.

6) ) The passing ability of concrete can be positively correlated to its flowability-segregation envelope. The higher the envelope, then the larger the passing ability will be.

7) At a given flowability, for designing concrete mixes with LS replacement of up to 25% percent of cementations materials, the passing ability of concrete can be superior with the lower possible segregation. This can be reached by putting in slightly more SP to improve the concurrent flowability-segregation performance.

References of Use of limestone Filler in HPC to improve passing ability property