The mix design for self-compacting high performance concrete containing various mineral admixtures

Accepted Manuscript The mix design for self-compacting high performance concrete containing various mineral admixtures Ha Thanh Le, Matthias Müller, Karsten Siewert, Horst-Michael Ludwig PII: DOI: Reference:

S0261-3069(15)00019-9 http://dx.doi.org/10.1016/j.matdes.2015.01.006 JMAD 7082

To appear in:

Materials and Design

Received Date: Accepted Date:

1 August 2014 21 January 2015

Please cite this article as: Le, H.T., Müller, M., Siewert, K., Ludwig, H-M., The mix design for self-compacting high performance concrete containing various mineral admixtures, Materials and Design (2015), doi: http:// dx.doi.org/10.1016/j.matdes.2015.01.006

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

The mix design for self-compacting high performance concrete containing various mineral admixtures Ha Thanh Le a,b,*, Matthias Müller a , Karsten Siewert a, Horst-Michael Ludwig a a)

F.A. Finger-Institute for Building Materials Science, Faculty of Civil Engineering, Bauhaus-University Weimar, Germany b)

Institute of Construction Engineering, University of Transport and Communications, Hanoi, Vietnam

Authors Ha Thanh Le a,b,*: (H. T. Le): M.Sc., corresponding author Email: [email protected] Tel: +49-3643-584765, Fax: +49-3643-584759 Matthias Müller a : Dipl.-Ing Email: [email protected] Tel: +49-3643-584807, Fax: +49-3643-584759 Karsten Siewert a: Dr.-Ing Email: [email protected] Tel: +49-3643-584725, Fax: +49-3643-584759 Horst-Michael Ludwig a: Prof. Dr.- Ing Email: [email protected] Tel: +49-3643-584761, Fax: +49-3643-584759

Abstract This paper is an effort towards presenting a new mix design method for self-compacting high performance concrete (SCHPC) containing various mineral admixtures (MA). In the proposed method, the constituent materials were calculated by using the absolute volume method. The packing theory of Funk and Dinger with the exponent q = 0.25 was adopted to determine the grading of aggregate. The primary paste volume for filling capacity was computed from the void content of compacted aggregate. The superplasticizer dosage for the concrete was set on the basis of the superplasticizer saturation dosage of the corresponding mortar. Efficiency factors were used to express the effect of MAs on compressive strength of concrete. The results show that the method was adequate to proportion SCHPC mixtures containing ternary 1

binders, i.e. cement and two different MAs (rice husk ash (RHA), silica fume, fly ash, and lime stone powder), satisfying the self-compactability requirements and compressive strength class in the range of C60/75 to C90/105. With 5-20 wt.-% cement replacement, RHA was very effective in improving compressive strength of SCHPC. The efficiency factor for RHA, i.e., 2.7 to 1.8, which is the first time applied, is only marginally lower as compared to that of silica fume.

Key words Self-compacting high performance concrete, mix design method, rice husk ash, efficiency factor, self-compactability, compressive strength

2

Nomenclature A

the designed air content (vol.-%)

Ai

the content of the air-dry aggregate i (kg/m3)

ai

the ratio of aggregate i to aggregate blend (wt.-%)

AB

the content of aggregate blend (kg/m3)

WAAi

the water absorption of aggregate i (wt.-%)

B

the binder content (cement plus MA) (kg/m3)

C’

the cement content in the MA-blended concrete (kg/m3)

Dmin, Dmax

the minimum and maximum particle sizes in the aggregate blend (mm)

SP

the dosage of SP (wt.-%)

fc,cube

the characteristic minimum cube compressive strength (MPa)

fc,dry,cube

the average cube compressive strength cured in dry conditions (MPa)

ki

the efficiency factor of MAi the moisture content of aggregate i (wt.-%)

n

the number of MA used

P(D)

the weight percentage of aggregate passing the sieve with size D (wt.-%)

PMAi

the content of MAi (kg/m3)

pi

the percentage of cement replaced by MAi (wt.-%)

RS,A

the coefficient related to the shape (S) and the angularity (A) of aggregate in the range of 1-5 [1]

Ssp

the solid content of SP (wt.-%)

VAB

the absolute volume of the aggregate blend (m3)

VAi

the absolute volume of aggregate i (m3)

Vexp

the excess paste volume (vol.-%)

Vp

the primary paste volume required for filling ability (vol.-%)

Vvoid

the void volume of the compacted aggregate blend in concrete (vol.-%)

Voids

the void content in compacted aggregate blend (vol.-%)

Wad

the adjusted water content (kg/m3)

AB

the bulk density of dry aggregate blend (kg/m3)

fc

The allowance for compressive strength (6-12 MPa) regulated in DIN EN 206-1

Ai

[2] the density of aggregate i (kg/m3)

AB

the density of dry aggregate blend (kg/m3)

c

the density of cement (kg/m3)

MAi

the density of MAi (kg/m3) 3

1. Introduction Self-compacting concrete is a concrete that can flow and consolidate under its own weight, pass through the spaces between the reinforcement bars to completely fill the formwork, and simultaneously maintain its stable composition [3-5]. Self-compacting high performance concrete (SCHPC) is defined as a new generation of concretes on the basis of the concepts of self-compacting concrete (SCC) and of high performance concrete (HPC). A method for proportioning SCHPC aims at fulfilling the self-compactability requirements of SCC (filling ability, passing ability, and segregation resistance), as presented in Table. 1, and of high compressive strength and good durability of HPC [6]. To realize this goal, a high volume of Portland cement, a very high dosage of chemical admixtures, i.e. super plasticizer (SP) and viscosity modifying admixtures, and reactive mineral admixtures (MA), e.g. silica fume (SF), are used [5-7]. Hence, high costs and environmental impact constitute the main disadvantage of SCHPC. The performance of SCHPC is highly improved by using SF however it is expensive due to the limited availability especially in developing countries. Rice husk ash (RHA), with its high amorphous silica content, is a very good replacement for SF with regards to compressive strength and durability of concrete [6, 8-12]. The reactive RHA is the residue of under proper conditions completely incinerated rice husk. Rice husk, the outer covering of a rice kernel, is an agricultural waste from the milling process of paddy. Rice husk is abundant in many rice cultivating countries, e.g. Vietnam, India and China. Normally, rice husk from paddy rice mills is disposed directly into the environment or sometimes is dumped or burnt in open piles on the fields. This results in serious environmental pollution, especially when it is disintegrated in wet conditions. Substitution of less-expensive RHA for SF as a partial cement replacement, not only improves the sustainability of SCHPC, but also reduces environmental pollution from the disposal of rice husk. It is well known that mix design is of major importance for the concrete production process. The mix design can be understood as combining optimum proportions of the constituent materials to fulfill the requirements of fresh and hardened concrete for a particular application [13]. Generally, in the mix proportioning of ordinary concrete, the required compressive strength is the prime criterion. For SCHPC, however, self-compactability, compressive strength and durability are equally taken into account in proportioning mixtures [6]. Regarding the properties of SCC/SCHPC, there exist two main mix design approaches to proportioning mixtures. One approach emphasizes on self-compactability, and ignores or does not give equal importance to compressive strength and durability as presented in [1, 4, 14, 15]. This approach does not render properly controlling the compressive strength, nor 4

reaching high compressive strength levels due to the high W/B ratio determined from the water demand of the binder. The other approach considers self-compactability as well as compressive strength as the targets of mix design for SCC/SCHPC. Compressive strength of SCC/SCHPC designed by these methods ranges mostly from 30 to 90 MPa [16-18]. This kind of method does not take into consideration the effect of MAs on self-compactability and compressive strength of SCC/SCHPC. Regarding the utilization of MAs in SCC/SCHPC, several individual MAs such as FA, RHA, SF, ground granulated blast-furnace slag (GGBFS) etc., are taken into consideration in the mix design to satisfy adequate self-compactability and required compressive strength [6, 19-22]. Each MA has its own advantages and disadvantages. Combination of various MAs can exploit their advantages and increase the cement replacement level. In order to take into account the effect of MAs on the mechanical properties of concrete, the concept of “efficiency factor” has been developed. The efficiency factor is empirically determined for the given content of materials and the exposure conditions [23-25]. The efficiency of RHA and other MAs will be presented in the next section. The efforts to relate the efficiency factor of MAs and compressive strength in mix-design for SCC/SCHPC are scarce in the literature, especially when more than one MA is used as cement replacement to achieve a particular high compressive strength exceeding 90 MPa. In this study, a simple mix design method for SCHPC was developed on the basis of the cementitious efficiency of mineral admixtures and of the requirements for ordinary concrete proportions laid down in DIN EN 206-1 [2] and DIN EN 1045-2 [26]. The proposed method was applied to design mixture proportions of SCHPC containing ternary binders, i.e. cement and two different MAs, i.e. RHA, SF, FA, and LSP, at various low W/B ratios.

2. Cementitious efficiency of RHA and other mineral admixtures All kinds of MAs, i.e. nearly inert, pozzolanic and latent hydraulic MAs, have been used to produce SCHPC. Where LSP is nearly inert or low reactive. SF, RHA, metakaolin, and low calcium class F-FA (according to ASTM: C618) are pozzolanic. And ground granulated blastfurnace slag and high calcium class C-FA (according to ASTM: C618) are both latent hydraulic and pozzolanic MAs [6, 8, 13]. Each type of MA exerts different effects on properties of both fresh and hardened concrete depending on its characteristic and replacement levels. In terms of compressive strength, the effect of MA can be expressed as an efficiency factor (k-value). The efficiency factor is defined as the portion of MA, which can be considered as equivalent to Portland cement in a MA-containing concrete. A k-value of a MA equal to 1 indicates that the MA is equivalent to cement. On the contrary, a k-value less 5

than 1 implies that the MA underscores cement as to its effect on compressive strength. The content of a MA can be multiplied by the k-value to convert to the equivalent cement content [23]. Recently, the efficiency factors for compressive strength of calcined kaolin and SF have been determined by the procedure proposed by Wong [25]. The k-value of a MA is obtained from the ratio of compressive strength of the MA-blended mixture to the control mixture (containing 100% OPC). It is generally concluded that the k factors increase with age but decrease with higher pozzolanic content. It was also observed that changes in W/C ratio from 0.33 to 0.27 did not significantly affect the resultant efficiency factors. The fundamental principle of Abram’s rule is applied in the method. The compressive strength of the MAblended mixture is inversely proportional to the water to equivalent cement content ratio (W/Ceq), where the equivalent cement content is C’ + kPMA. The compressive strength of Portland cement concrete, fc, can be expressed by: (1) The compressive strength of concrete containing a MA, fMA, can in analogy with Eq. (1) be expressed by: (2) in which the k-value relevant for the specific MA is used to estimate the equivalent cement content. Further, K1 and K2 are proportionality constants. In Eq. (1) and (2), C is cement content in the control mixture (kg/m3); C’ is cement content in the MA-blended mixture (kg/m3); and PMA is MA content (kg/m3). It is assumed that K1 is equal to K2, because the mixture proportions, W/C ratio, curing history and testing conditions for the control and the MA-blended mixtures are similar. Therefore, k can be assessed for a specific MA by dividing Eq. (2) by Eq. (1), yielding: (3) When p is the percentage cement replacement by the MA, Eq. (3) transforms into: (4) In this study, the strength efficiency factor of RHA was determined by the procedure above. The control and RHA-blended mortars with cement-sand-water proportions of (1/3/0.5) were prepared. For the RHA-blended mortars, Portland cement (CEM I 52.5 R) was partially 6

replaced by 5, 10, 15, 20, 25, 30 wt.-% RHA (average grain size of 7.7 µm), and superplasticizer was introduced to meet the flow of the control mortar determined in accordance with DIN EN 1015-3[27]. Mortar specimens having dimensions of 40 x 40 x 160 mm3 were cast and cured in moulds at temperature of 20 oC and 95 % relative humidity for one day. After demoulding the specimens were stored in water at 20 oC until testing at 28 days. Compressive strength was tested according to DIN EN 196-1[28]. Six specimens of each mixture were tested and the average values were reported. The average 28 daycompressive strength of mortars and efficiency factor at different percentage replacements by RHA are shown in Fig. 1 and Fig. 2 respectively. Based on the experimental data in this study, a model for the efficiency factor at 28 days (k28) at different percentage replacements by RHA is given by: k28 = 0.0007p2 - 0.076p + 3.056

(5)

According to this model, the k-values for RHA with 5 - 20 wt.-% cement replacement decline from 2.7 to 1.8. In Table. 2, k-values for RHA and other MAs at concrete age of 28 days are presented.

3. Proposed mixture design procedure The proposed method considers SCHPC to consist of two phases: aggregate and paste. The grading of the aggregate blend is determined in accordance with the packing theory of Funk and Dinger with the exponent q = 0.25. The paste volume is determined on the basis of a void content in the compacted aggregate blend. Adequate self-compactability is mainly governed by the paste volume, the type and content of MA, and by the SP dosage. The W/B ratio and the cementitious efficiency of MA are mainly taken into account to achieve the required compressive strength. The proposed procedure for proportioning SCHPC containing various MAs is schematically presented in Fig. 3 and follows the basic steps, listed thereafter. Step 1: Determination of the void content of compacted aggregate blend The ratio of aggregate components are computed on the basis of Funk and Dinger theory with exponent q = 0.25 [29], which follows Eq. (6). The optimum ratio of aggregate results in the particle size distribution of aggregate, which follows the ideal curve with the minimum deviation. (6)

7

The ideal grading curve of the Funk and Dinger theory with q = 0.25, Dmax = 16 mm and Dmin = 0.63 mm is applied. The grading curve of the aggregate used in this study and the required range of aggregate grains for ordinary concrete (A16 and C16) complying with DIN EN 206 1 [2] and DIN 1045-2 [26] are shown in Fig. 4. The bulk density of compacted aggregate blend is determined by experiment with the determined ratio of the aggregate components. The mixed aggregate blend was filled into a 8 litters container and vibrated in two times of 2 minutes each. The bulk density of the compacted aggregate was calculated from the weight and volume of aggregate in the container. Next, the void content of the compacted aggregate blend can be calculated by: (7) (8) Step 2: Determination of the primary paste volume The paste volume in SCHPC is significantly larger than that in ordinary concrete. It is required to fill the void volume between aggregate particles, and make sufficient lubricating layers on the surface of aggregate particles. The lubricating layers reduce the friction between the aggregate particles, and hence increase the flowability of concrete [6]. The primary paste volume can be calculated via the equations given by Koehler and Fowler [1]. So, (9) (10) (11) The paste volume should range from 30 to 42 % by volume of the concrete according to [1, 4, 30]. Step 3: Determination of the water-binder ratio Established relationships between components of normal concrete, such as W/C vs. compressive strength, can also be applied to SCC/SCHPC [13, 17]. As a consequence, the average compressive strength can be determined in accordance with DIN EN 206-1 [2] and DIN 1045-2 [26] from: (12)

8

Thereupon, the equivalent W/Ceq ratio can be calculated from the relationship between compressive strength and W/C ratio (Walz curve) presented in Fig. 5. For the durability, the W/C ratio should satisfy the limit values regulated in DIN EN 206-1 [2] and DIN 1045-2 [26]. When the type and content of MA replacing the cement are known, the W/B ratio can be calculated via Eq. (13). (13) The W/B ratio of HPC is generally in the range of 0.25 - 0.4 [9, 31], while the W/B ratio of SCC ranges from 0.26 to 0.48 [30]. Therefore, the appropriate W/B ratio for SCHPC should be between 0.25 and 0.4. A W/B ratio below 0.25 can be used when SP and paste composition can yield a low enough plastic viscosity. Step 4: Determination of cement, mineral admixture, and water contents The content of the cement, of each MA and of the water can be determined on the basis of the known paste volume (Vp), W/B ratio, and the cement content replaced by each MA. By solving Eq. (14) for B, the binder content is obtained. Then the cement, both mineral admixtures and water contents can be calculated by: (14) (15) (16) (17) The binder contents should be in the range from 425 to 625 kg/m3 [30], while the cement content should not be lower than the limit values regulated for durability in DIN EN 206-1 [2] and DIN 1045-2 [26]. The water content should be lower than 200 kg/m3 [15]. Step 5: Determination of aggregate content Based on the known paste volume and the ratio of aggregate components, the content of aggregate blend and then individual aggregate components can be calculated by using the following equations: (18) (19) 9

The coarse aggregate content should vary from 28 to 38 vol.-% of the concrete [30]. Step 6: Determination of the dosage of superplasticizer The saturation superlasticizer dosage (SSD) of the corresponding mortar is used as the primary SP demand for SCHPC. The SSD is determined by testing the mini-cone slump flow of mortar, as described in EFNARC [15] (Fig. 6 and Fig. 7). The SSD is defined as a SP dosage beyond which the slump flow no longer increases or reaches a maximum slump flow [6]. Step 7: Adjustment of the water content The water absorption of aggregates and the water contribution of SP should be considered to adjust the content of mixing water. Therefore, the adjusted water content can be determined by: (20) Step 8: Trial mixtures and adjustments Trial batches are prepared using the proportions calculated above. To examine whether the mixture proportions designed by the proposed method could meet the self-compactability and compressive strength requirements, the quality control tests should be carried out. When the results of the quality control tests do not fulfill the requirements of the fresh concrete (Table. 1), adjustments will be made until all properties of SCHPC meet the requirements expected in the design. For example, when the filling and passing abilities are poor, the SP dosage should be increased first. When the filling and passing abilities cannot be achieved by adjusting SP dosage, increase in paste volume leads to higher filling and passing abilities for a given SP dosage.

4. Validation of the proposed method 4.1. Materials The materials used in this study were Portland cement (CEM I 52.5 R), RHA, undensified SF (USF), densified SF (DSF), FA, LSP, natural sand (0-2mm), and crushed basalt stone (2-5 mm, 5-8 mm, 8-11 mm, 11-16 mm). Rice husk from Vietnam was burnt under appropriate temperature conditions, and the obtained ash was thereupon ground in a ball mill. In the present study, RHA was used with two different mean particle sizes of 5.7 µm (RHA5.7) and 7.7 µm (RHA7.7). The first type was used in mixtures with W/B ratio of 0.26 and the second one in the mixtures with W/B ratio of 0.30 and 0.34. The physical properties and the chemical 10

composition of cement and MAs are summarized in Table. 3. Their particle size distributions are shown in Fig. 8. In Fig. 9, SEM images show the morphology of RHA and of other MA particles. Obviously, the ground RHA is a porous material with macro pores (>50nm) and meso pores (2-50 nm) on the surface and inside the particles. The pore structure of RHA has been analyzed in detail in the previous studies [32, 33]. The physical properties of aggregate are presented in Table. 4, and its particle size distribution is shown in Fig. 4. In addition, a Polycarboxylate-based SP with density of 1080 kg/m3 and 40 wt.-% solid content was used. 4.2. Mixture proportions Nine SCHPC mixtures were designed to validate the proposed method. They contained ternary binders, i.e. cement and two different MAs, such as RHA, SF, FA and LSP. The aim of the design was to fulfil slump flow class SF2, viscosity class VF2, passing ability class PJ2, segregation resistance class SR2 (Table. 1) and compressive strength classes C60/75, C70/85, C80/95, and C90/105 as regulated in standards DIN EN 206-1 [2] and DIN 1045-2 [26]. The ratio of aggregate components was computed on the basis of Funk and Dinger with the minimum deviation, yielding: natural sand (0-2mm): 45.0 wt.-%, basalt stone (2-5 mm): 28.0 wt.-%, (5-8 mm): 6.2 wt.-%, (8-11 mm): 11.2 wt.-%, (11-16 mm): 9.6 wt.-%. The particle size distribution of the aggregate blend is illustrated in Fig. 4. The bulk density of compacted aggregate blend was determined by experiment, AB = 2170 (kg/m3), while the density of aggregate blend was calculated from Eq. (8), AB = 2930 (kg/m3). Next, the void content of compacted aggregate blend was calculated by using Eq. (7), Voids = 26 vol.-%. The proportions of constituent materials were determined in accordance with the procedure, as mentioned in Section 3. Summarizing, the volume fractions of paste, fine and coarse aggregates are 0.365, 0.298 and 0.317 (m3), respectively. The air content was set at 2 vol.-% (0.02 m3) for non-air entrained concrete. The mixture proportions are presented in Table. 5. The mixture types were designated on the basis of W/B ratio, type and percentage of MA replacing cement by weight. For instance, in the mixture ’’30LSP20R10’’, 30 wt.-% cement content was replaced by 20 wt.-% LSP, and 10 wt.-% RHA, and the W/B ratio was 0.30. 4.3. Experimental methods All SCHPC mixtures were prepared in a Pemat ZK30 mixer with total mixing time of 13 minutes. The mixing procedure is shown in Fig. 10. SSD of mortar was determined by testing the mini-cone slump flow as described in EFNARC [15]. Flow rate of mortar was also evaluated by T 250 time, which is the spread time for a 11

diameter of 250 mm, corresponding to T 500 time measured in SCC/SCHPC [15, 34] (Fig. 6 and Fig. 7). To examine whether the mixture proportions designed by the proposed method could meet the self-compactability and compressive strength requirements, the following tests were carried out. Slump flow test: Test was carried out in accordance with DIN EN 12350-8 [35] to measure filling ability and flow rate T 500, which indicate plastic viscosity of the fresh concrete. V-funnel test: Test was carried out in accordance with DIN EN 12350-9 [36] to measure the flow time through the V-funnel. The plastic viscosity of fresh concrete can be evaluated based on the V-funnel flow time, and the arching effect of aggregate can be detected as well. J-ring test: Test was carried out in accordance with DIN EN 12350-12 [37] to assess filling ability and passing ability of fresh concrete between reinforcement bars. Sieve segregation test: Test was carried out in accordance with DIN EN12350-11 [38]. The test aims at investigating the resistance of SCHPC to segregation by measuring the portion of the fresh SCHPC sample passing through a 5 mm sieve. If the SCHPC has poor resistance to segregation, the paste or mortar can easily pass the sieve. Therefore, the sieved portion indicates whether the SCHPC is stable or not. Compression test: Cubic specimens of 150x150x150 mm3 for compressive strength were cast without vibration and compaction. After 1 day, the specimens were demoulded, stored in water at 20 ± 2 oC for further 6 days, and then cured in a room under controlled temperature (20 ± 2 oC) and humidity (65 ± 5 %) conditions until testing at 7 and 28 days according to DIN EN 12390-2 [39]. Compressive strength of concrete was determined under DIN EN 12390-3 [40]. Three specimens of each mixture were tested, and the average values are reported. 4.4. Self-compactability of SCHPC The experimental results of self-compactability of fresh concrete are presented in Table. 6. The slump flow of the SCHPCs ranged from 730 to 780 mm, without signs of bleeding and segregation. The V-funnel flow times and T500 values were in the range of 9.2-22.3 s and of 2.9-7.0 s, respectively. The J-ring step height is equal to 10 mm in most cases. The sieve segregation index ranged from 4.7 to 13.6 wt.-%. This indicates that the SCHPCs had excellent filling ability, good plastic viscosity, adequate passing ability and good segregation resistance. All of the SCHPC mixtures meet the requirements of slump flow class SF2, 12

viscosity class VF2, passing ability class PJ2, segregation resistance class SR2, as shown in Table. 1. It is well known that the self-compactability of SCHPC is governed by paste composition and SP dosage when the paste volume and aggregate volume are fixed. All trial batches of concretes were made with the SSDs of the corresponding mortars. Interestingly, the SP demand of SCHPC to meet self-compactability requirements was similar to the SSD of the corresponding mortar, as shown in Table. 5 and Fig. 11. Mixtures proportioned with W/B ratio of 0.26 satisfied the requirements of self-compactability with the SSDs of the corresponding mortars. For mixtures proportioned with W/B ratio of 0.30 and 0.34, SP demand for the requirements of self-compactability of concrete was slightly adjusted in some cases compared with SSD of the corresponding mortars. For instance, the mixture ’’34LSP20R10’’ made with SSD had a slump flow of 650 mm, T 500 value of 2.8 s, and sieve segregation index of 3.8 wt.-%. However, the J-ring step height was 20 mm significantly higher than the standardized value of 10 mm (Table. 1). After SP dosage was increased from the SSD of 2.0 to 2.25 wt.-%, all requirements for self-compactability were fulfilled (Table. 6). The results of properties of fresh SCHPC show that the mixtures incorporating LSP need a much higher SP dosage than the mixtures incorporating FA to meet the required selfcompactability (Table. 5). It is caused by LSP having angular particles with rough surface and smaller size, and hence with a larger specific surface area. On the contrary, FA has spherical particles with larger size and hence has a lower specific surface area and water demand (Table. 3 and Fig. 9). As a result, the incorporation of LSP into the mixtures leads to an increase in viscosity of paste and hence a decrease in slump flows of concrete. To reach the required flowing ability, a higher SP dosage must be used in the mixture containing LSP, compared to the mixture containing FA. At W/B of 0.34, the SP demand of concrete increased with a higher content of RHA7.7. The increase in RHA7.7 content decreased the filling ability (slump flow), and increased the plastic viscosity (V-funnel time) and hence segregation resistance of SCHPC (sieve segregation). As concluded in the previous studies [32, 33], RHA is a macro-mesoporous material (Fig. 9c). The partial replacement of cement by RHA results in the increase in specific surface area of binder and water demand of mixture due to the large amount of water absorbed into macro and meso pores of the RHA particles. With 10, 15, and 20 wt.-% cement replacements by RHA7.7, the amount of water needed to fully fill its pore volume is about 13

5.5, 8.2 and 10.9 liter/m3 concrete and about 3.1, 4.7 and 6.2 wt.-% mixing water, respectively. At W/B of 0.26, the mixture containing RHA5.7 had a higher SP demand than the mixture containing USF, and similar to the mixture containing DSF. The incorporation of RHA5.7 reduced the filling ability, and significantly increased plastic viscosity and hence segregation resistance of SCHPC. The effect of RHA5.7 is stronger than USF and similar to DSF (Table. 6). Different from RHA, USF particles are spherical and dense (Fig. 9a) and hence increased filling ability and decreased viscosity of SCHPC due to ’’ball bearing effect’’ and lower water demand. The difference in effect of RHA and SF has been fully explained in the previous studies [32, 33]. In the case of DSF, very fine SF particles were compacted as large SF particles (Fig. 9b). The experimental results show that the mixture containing DSF had lower filling ability, higher plastic viscosity and hence higher segregation resistance compared to the mixture containing USF. That indicates that the compacted particles could not be separated completely during mixing. The pores formed between the fine SF particles in the large compacted SF particles might absorb an amount of water resulting in the reduction in free water in mixture, hence decreased the filling ability and increased viscosity of mixture. 4.5. Compressive strength of SCHPC Compressive strength results of SCHPC are presented in Fig. 12 and Fig. 13. It can be seen that the 28-day compressive strengths of all SCHPC mixtures reached over 90 MPa and met the designed compressive strength classes. The relationship between expected and experimental compressive strength at 28 days of all SCHPC mixtures (Table. 5) is presented in Fig. 12. These results in this study indicate that application of the efficiency factor (kvalue) and the relationship between compressive strength and W/C ratio for ordinary concrete (Walz curve) are suitable for estimating compressive strength in the mix design for SCHPC. The development of compressive strength of SCHPC is presented in Fig. 13. At W/B of 0.34, increasing RHA7.7 content decreased compressive strength of concrete at 3 and 7 days however increased compressive strength at 28 days. RHA is a very reactive porous MA. The additional C-S-H formed by the pozzolanic reaction of RHA refines the pore structure of the cement matrix, and improves the interface transition zone resulting in the increase in compressive strength [6, 9, 41, 42]. Furthermore, the internal water curing effect of RHA can also exert a positive effect on compressive strength at 28 days, especially at later ages. The amount of water absorbed in the pores of RHA particles will be released to promote further hydration of the cement, especially when the relative humidity of the paste considerably 14

decreases [41, 43]. At the early ages (3 and 7 days), the incorporation of 20 wt.-% RHA7.7 led to the reduction in compressive strength. This result has also been obtained in a previous study [41] and other studies on ultra high performance concrete [12]. 20 wt.-% cement replacements by RHA7.7 resulted in a significantly lower cement content in the paste and hence reduced compressive strength due to the diluting effect. Additionally, the larger amount of water absorbed in the pores of RHA particles causes a lack of available water for cement hydration at the early ages. RHA particles with porous structure are themselves the weakest points in the cement matrix [32]. This might be another negative effect of RHA on compressive strength at the early ages, especially at high RHA content in concrete. At W/B of 0.30 and 0.34, the compressive strength of the mixtures containing FA is slightly higher than that of the mixtures containing LSP, regardless of ages, especially at the lower W/B ratio. LSP is considered as a nearly inert MA, whereas FA is a pozzolanic MA with kvalue of 0.59 (Section 2). Consequently, pozzolanic activity of FA might contribute the higher compressive strength of the mixture containing FA. At W/B of 0.26, the compressive strength of the mixture containing RHA was similar to that of the mixture containing SF, irrespective of ages. As mentioned in Section 2, RHA is a highly reactive MA comparable with SF [8, 9, 32, 42]. This result is also consistent with the results in a previous study and of other studies [6, 9, 12, 41, 42]. 4.6. Discussion Most proportioning design methods for SCC/SCHPC are based on empirical tests and considerably different from those for ordinary concrete. To compare with the proposed method, several well-known mix design methods for SCC/SCHPC are summarized and analyzed in what follows: In the method of Okamura and its modified versions [3, 4, 14, 15], generally, the coarse aggregate volume is fixed at 50 % of the solid volume in the concrete, and the fine aggregate volume is fixed at 40 % of the mortar volume. The W/B ratio is first determined from the slump flow tests on the paste. Then the W/B ratio and SP content are determined from slump flow tests on mortar. The final W/B ratio and SP content are determined by trails on concrete so as to ensure self-compactability. The procedure developed by Peterson et al. [44, 45], the so called CBI method, aims finding the maximum content of aggregate that ensures the flow of concrete through the reinforcement without causing blockage. The content of the filler, water and SP are determined on concrete tests with coaxial rheometer. More recently, the mix design method proposed by Su et al. [17, 46] is developed on the basis of the packing factor 15

of aggregate which is the mass ratio of tightly to loosely packed aggregate in SCC. Then coarse and fine aggregate contents are calculated with the assumption of volume ratio of fine to coarse aggregate (50-57 %). The cement content is determined by the required compressive strength (0.11-0.14 MPa/kg cement). MA, e.g. FA and GGBFS, is used to obtain the high paste volume ensuring the required self-compacting properties. The water demand of MA is considered. The SP content is chosen on the basis of engineering experience, finally determined from experimental tests on concrete to meet the required self-compacting properties. This survey of common mix design methods reveals their complexity for practical implementation. They use as prime parameters the content of coarse and fine aggregate and of the SP, as well as the W/B ratio. Hence, grading and packing of the aggregate are ignored, although well-known to influence paste content and workability of the SCC. Viscosity of the concrete declines at tighter packing of the aggregate because more paste will be available as lubricant between the particles for a given paste content. This is similar to viscosity of slurry produced by solids and water [29]. Next, W/B ratio is determined to meet the selfcompactability requirements, so that compressive strength cannot be controlled. Actually, many mixtures composed by the Okamura method have a higher compressive strength than required due to a relatively high paste content [47]. Su et al. [17, 46] control the compressive strength via the strength efficiency factor of cement. However, this is a valid approach for type I PC (CEM I) only and not for a blended cement, such as CEM III/B 42.5 [47]. For all mix design methods, SP content and W/B ratio are derived from experiments, i.e., by slump flow test and/or rheometer, a procedure that is laborious, time-consuming and expensive. Furthermore, the effect of MA or filler on rheological properties/self-compactability and compressive strength is not taken into consideration either. The proposed method in this study is developed on the basis of the cementing efficiency of MA and the requirements for proportioning ordinary concrete. In doing so, all major parameters are taken into consideration, as demonstrated herein. Further, due to its similarity with the methods for normal concrete, the present set up is as simple and handy for practical applications. The mixture proportions designed by the proposed method are consistent with the regulations for SCC/SCHPC proportioning as recommended by EFNARC [4] and with reported studies on successful mixtures in the period 1993-2003, as presented in Table. 7. It is very difficult to produce SCHPC with very high compressive strength as obtained for ultra high performance concrete because of the high entrapped air content at very low W/B 16

ratio. Yet, in the herein reported tests that were based on mixture proportioning by the proposed method, guaranteeing good self-compactability, we have demonstrated that a compressive strength level of 120 MPa can be obtained, exceeding the reported strength levels in earlier reports [6, 13, 17, 30, 48].

5. Conclusions The aim of this work was to develop a new mix design method for SCHPC on the basis of the cementitious efficiency of mineral admixture and the requirements for ordinary concrete proportions regulated in DIN EN 206-1 [2] and DIN 1045-2 [26]. From the experimental results, the following conclusions can be drawn: 1) The strength efficiency factor of RHA was assessed. Increasing percentage replacement of cement by RHA decreased the efficiency factor of RHA. 2) A simple mix design method was proposed for SCHPC containing RHA and other MAs. It is based on the cementitious efficiency of mineral admixture and the requirements for ordinary concrete proportions regulated in DIN EN 206-1 [2] and DIN 1045-2 [26]. Selfcompactability can be achieved with a few trials. A proper compressive strength level as in ordinary concrete can be obtained for a particular W/B ratio, a given content and type of MA. 3) The procedure of the proposed method for SCC/SCHPC is similar to that of ordinary concrete, so is as simple for mix design of SCC/SCHPC and for practical applications. The packing theory of Funk and Dinger with an exponent q = 0.25 was adopted to determine the grading of aggregate. The primary paste volume for filling ability was computed from the void content of compacted aggregate. The superplasticizer dosage for the concrete was set on the basis of the superplasticizer saturation dosage of the corresponding mortar. W/B ratio was determined on the basis of the required compressive strength. Efficiency factors were used to express effect of MAs on compressive strength of concrete. 4) In the range of 5 - 20 wt.-% cement replacement, RHA was very effective in improving compressive strength of SCHPC. The underlying design of the SCHPC could be successfully based on the proposed value range of the efficiency factor for RHA. i.e., 2.7 to 1.8, which is only marginally lower as compared to that of SF. 5) Using the proposed method, SCHPC was developed with ternary binders, i.e. cement and two different MAs from RHA, SF, FA, and LSP, having good self-compactability and high compressive strength in the range of over 90 MPa. It was demonstrated that even 120 17

MPa is attainable at 28 days with the hybrid blended mixtures of SCHPC, while still manifesting good self-compactability. 6) It is possible to use common MAs (LSP, FA) in combination with RHA to produce SCHPC with good self-compactability and very high compressive strength. The combination of 10 wt.-% RHA and 20 wt.-% FA is superior over 10 wt.-% RHA and 20 wt.-% LSP with respect to superplasticizer demand and compressive strength of SCHPC.

18

Acknowledgements The authors would like to express thanks to Ministry of Education and Training of Viet Nam, F.A. Finger-Institute for Building Material Science (FIB) - Bauhaus University Weimar and German Academic Exchange Service (DAAD) for financial support. The authors are also grateful to Dr. Bui, D.D.; Dipl.-Ing. Flohr, A.; Dipl.-Ing. Ehrhardt, D.; Dipl.-Ing. Giese, A. for helpful discussions.

References [1] Koehler E, Fowler D. Aggregate in self-consolidating concrete. ICAR Project 108. The University of Texas at Austin: International Center for Aggregates Research; 2007. p. 362. [2] DIN EN 206-1. Specification, performance, production and conformity. Berlin: Beuth Verlag GmbH; 2001. p. 77. [3] Okamura H, Ouchi M. Self-compacting high performance concrete. Prog Struct Eng Mater. 1998;1:378-83. [4] The European guidelines for self-compacting concrete, specification, production and use. Norfolk: The Self-Compacting Concrete European Project Group; 2005. p. 63. [5] Guidelines for viscosity modifying admixtures for concrete. Norfolk: The European Federation of Specialist Construction Chemicals and Concrete Systems (EFNARC); 2006. p. 12. [6] Safiuddin M. Development of self-consolidating high performance concrete incorporating rice husk ash [PhD thesis]: University of Waterloo, Canada; 2008. [7] Gesoğlu M, Güneyisi E, Özbay E. Properties of self-compacting concretes made with binary, ternary, and quaternary cementitious blends of fly ash, blast furnace slag, and silica fume. Construct Build Mater. 2009;23:1847-54. [8] Mehta PK. Rice husk ash - a unique supplementary cementing material. Advances in concrete technology. Center for Mineral and Energy Technology, Ottawa1994. p. 41944. [9] Bui DD. Rice Husk Ash as a mineral admixture for high performance concrete [PhD Thesis]. The Netherlands: Delft University of Technology; 2001. [10] Rodriguez de Sensale G. Effect of rice-husk ash on durability of cementitious materials. Cem Concr Compos. 2010;32:718-25. [11] Chao-Lung H, Anh-Tuan BL, Chun-Tsun C. Effect of rice husk ash on the strength and durability characteristics of concrete. Construct Build Mater. 2011;25:3768-72. [12] Nguyen VT, Ye G, van Breugel K, Fraaij ALA, Bui DD. The study of using rice husk ash to produce ultra high performance concrete. Construct Build Mater. 2011;25:2030-5. 19

[13] De Schutter G, Bartos P, Domone P, Gibbs J. Self-compacting concrete. Caithness, Scotland, UK: Whittles Publishing; 2008. [14] Okamura H, Ozawa K. Mix design for self-compacting concrete. Concrete library of JSCE. 1995;25:107-20. [15] Specification and guidelines for self-compacting concrete. Norfolk: The European Federation of Specialist Construction Chemicals and Concrete Systems (EFNARC); 2002. p. 32. [16] Saak A, Jennings H, Shah S. New methodology for designing self-compacting concrete. ACI Mater J. 2001;98:429-39. [17] Su N, Hsu K-C, Chai H-W. A simple mix design method for self-compacting concrete. Cem Concr Res. 2001;31:1799-807. [18] Kheder G, AlJadiri R. New method for proportioning self-compacting concrete based on compressive strength requirements. ACI Mater J. 2010;107:490-7. [19] Kwan A. Use of condensed silica fume for making high strength, self-consolidating concrete. Can J Civ Eng. 2000;27:620-7. [20] Chowdhury S, Basu P. New methodology to proportion self-sonsolidating concrete with high-volume fly ash. ACI Mater J. 2010;107:222-30. [21] Xie Y, Liu B, Yin J, Zhou S. Optimum mix parameters of high-strength self-compacting concrete with ultrapulverized fly ash. Cem Concr Res. 2002;32:477-80. [22] Dinakar P, Sethy K, Sahoo U. Design of self-compacting concrete with ground granulated blast furnace slag. Mater Des. 2013;43:161-9. [23] Papadakis VG, Antiohos S, Tsimas S. Supplementary cementing materials in concrete: Part II: A fundamental estimation of the efficiency factor. Cem Concr Res. 2002;32:1533-8. [24] Papadakis VG, Tsimas S. Supplementary cementing materials in concrete: Part I: efficiency and design. Cem Concr Res. 2002;32:1525-32. [25] Wong HS, Abdul Razak H. Efficiency of calcined kaolin and silica fume as cement replacement material for strength performance. Cem Concr Res. 2005;35:696-702. [26] DIN 1045-2. Concrete specification, properties, production and conformity-Aplication rules for DIN EN 206-1. Berlin: Beuth Verlag GmbH; 2008. p. 62. [27] DIN EN 1015-3. Determination of consistence of fresh mortar (by flow table). Berlin: Beuth Verlag GmbH; 2007. p. 12. [28] DIN EN 196-1. Determination of strength. Berlin: Beuth Verlag GmbH; 2005. p. 33. [29] Funk JE, Dinger DR. Predictive process control of crowded particulate suspension, Applied to ceramic manufacturing New York: Kluwer Academic Press; 1994. [30] Domone PL. Self-compacting concrete: An analysis of 11 years of case studies. Cem Concr Compos. 2006;28:197–208. 20

[31] Neville A, Aïtcin P-C. High performance concrete—An overview. Mater Struct. 1998;31:111-7. [32] Le HT, Rößler C, Siewert K, Ludwig HM. Rice husk ash as a pozzolanic viscosity modifying admixture for self-compacting high performance mortar. Proceedings of the 18th international conference on building materials (Ibausil 18). Weimar, Germany: F.A. Finger-Institut für Baustoffkunde; 2012. p. 0538-45. [33] Le HT, Siewert K, Ludwig HM. Rheological behaviour of fresh mortar formulated from self-compacting high performance concrete incorporating rice husk ash. Proceedings of The 1th RILEM internaltional conference on rheology and processing of construction materials. Paris, France: RILEM publications S.A.R.L; 2013. p. 131-8. [34] Rizwan SA. High performace motars and concretes using secondary raw materials [PhD thesis]. Freiberg, Germany: Technischen Universität Bergakademie Freiberg; 2006. [35] DIN EN 12350-8. Self-compacting concrete – Slump-flow test. Berlin: Beuth Verlag GmbH; 2010. p. 12. [36] DIN EN 12350-9. Self-compacting concrete –V-funnel test: Beuth Verlag GmbH; 2010. p. 10. [37] DIN EN 12350-12. Self-compacting concrete –J-ring test. Berlin: Beuth Verlag GmbH; 2010. p. 13. [38] DIN EN 12350-11. Self-compacting concrete –Sieve segregation test. Berlin: Beuth Verlag GmbH; 2010. p. 11. [39] DIN EN 12390-2. Making and curing specimens for strength tests. Berlin: Beuth Verlag GmbH; 2009. p. 10. [40] DIN EN 12390-3. Compressive strength of test specimens. Berlin: Beuth Verlag GmbH; 2009. p. 19. [41] Le HT, Nguyen ST, Ludwig HM. A Study on High Performance Fine-Grained Concrete Containing Rice Husk Ash. Int J Concr Struct Mater. 2014;8:301-7. [42] Nguyen VT. Rice husk ash as a mineral admixture for ultra high performance concrete [PhD thesis]. The Netherlands: Delft University of Technology; 2011. [43] Nguyen VT, Ye G, van Breugel K, Copuroglu O. Hydration and microstructure of ultra high performance concrete incorporating rice husk ash. Cem Concr Res. 2011;41:110411. [44] Petersson Ö BP, Van BK. A model for self-compacting concrete. In: Bartos PJM MD, Cleand DJ, editor. RILEM conference product methods workability concrete: E & FN Spon; 1996. p. 483–92. [45] Petersson Ö, Billberg P. Investigation on blocking of self-compacting concrete with different maximum aggregate size and use of viscosity agent instead of filler. In: Petersson ÅSaÖ, editor. First International RILEM Symposium on Self-Compacting Concrete. Paris: RILEM Publications SARL; 1999. 21

[46] Su N, Miao B. A new method for the mix design of medium strength flowing concrete with low cement content. Cem Concr Compos. 2003;25:215-22. [47] Brouwers HJH, Radix HJ. Self-Compacting Concrete: Theoretical and experimental study. Cem Concr Res. 2005;35:2116-36. [48] Bouzoubaâ N, Lachemi M. Self-compacting concrete incorporating high volumes of class F fly ash: Preliminary results. Cem Concr Res. 2001;31:413-20. [49] DIN EN 206-9. Additional rules for self-compacting concrete. Berlin: Beuth Verlag GmbH; 2010. p. 29. [50] Domone PL. A review of the hardened mechanical properties of self-compacting concrete. Cem Concr Compos. 2007;29:1-12. [51] Puntke W. Wasseranspruch von feinen Kornhauf-werken. Beton 2002;52:242–8. [52] Zement-Taschenbuch. 51. Auflage ed. Düsseldorf: Verein Deutscher Zementwerke; 2008.

22

The list of table captions Table. 1 The requirements for the properties of fresh SCC/SCHPC according to DIN EN2069[49] Table. 2 Efficiency factors of RHA and other mineral admixtures Table. 3 Chemical composition (wt.-%) and physical properties of cement and MAs Table. 4 Physical properties of the fine and coarse aggregate Table. 5 Mixture proportions of SCHPC Table. 6 Test results of self-compactability of investigated SCHPC Table. 7 The mixture proportions in this study, by EFNARC and in reported studies

23

Table.1 Slump-flow

Viscosity

Passing ability

Segregation resistance

Class

Slumpflow (mm)a

Class

T500 (sec)b

V-funnel (sec)

Class

J-ring step height (mm)

Class

Sieve segregation (%)

SF1

550-650

VS1/VF1

<2

< 9c

PJ1

≤10 with 12 bars

SR1

≤ 20

SF2

660-750

VS2/VF2

≥2

9-25d

PJ2

≤10 with 16 bars

SR2

≤ 15

SF3

760-850

-

-

-

-

-

-

Permissible deviation: a) ± 50mm; b) ± 1s; c) ± 3s; d) ± 5s

Table.2 Mineral admixtures

LSP [50]

FA [50]

SF [25]

RHA*

Content (wt.-%)

15-55

20-60

5-15

5-20

k-value

0.29

0.56

3.1-2.1

2.7-1.8

* proposed by the authors

Table.3 Chemical analyses

Cement

RHA

USF

DSF

FA

LSP

SiO2

19.4

87.0

96.6

96.2

56.6

10.9

Al2O3

5.3

0.8

0.7

0.7

25.8

4.2

Fe2O3

2.5

0.4

0.2

0.3

6.4

1.3

CaO

61.2

1.2

0.3

0.0

2.5

46.8

MgO

1.2

0.6

0.4

0.1

1.3

1.2

SO3

3.2

0.4

0.1

0.1

0.6

0.6

Na2O

0.07

0.4

0.16

0.06

0.62

0.3

K2O

0.61

2.63

0.65

0.37

2.08

1.02

4.9

3.7

0.9

1.6

2.9

34.0

Density (kg/m )

3090

2270

2260

2260

2270

2740

MPS (µm)

7.07

5.7; 7.7

0.35

0.29

16.39

7.88

[0.595]

25.21(5.7µm) 23.05(7.7µm)

18.09

26.43

2.14

6.88

0.34

0.57 (5.7µm) 0.61 (7.7µm)

0.53

0.53

0.33

0.37

-

0.08 (5.7µm) 0.106 (7.7µm)

-

-

-

-

LOI 3

Specific surface area BET [Blain] (103 m2/kg) Water demand by Puntke method [51] (10-3 m3/kg) Pore volume by BJH method (10-3 m3/kg)

LOI- Loss on Ignition, DSF- Densified SF, USF-Undensified SF

24

Table. 4

Properties

Natural sand

Basalt stone

Fineness modulus

2.32

6.14

Density (kg/m3)

2650

3050

Water absorption (wt.-%)

0.08

0.8

Moisture content (wt.-%)

0.0

0.2

25

Table 5 Mixtures

W/Ceq

W/B

Water (kg/m3)

Cement (kg/m3)

LSP (kg/m3)

FA (kg/m3)

SF (kg/m3)

RHA (kg/m3)

Sand (kg/m3)

Basalt stone (kg/m3)

SP (wt.-%)

SP/SSD* (%)

Strength class

34LSP20R10

0.34

0.34

182

374

107

0

0

53

790

968

2.25

113

C60/75

34FA20R10

0.32

0.34

178

366

0

104

0

52

790

968

1.25

100

C70/85

34FA20R15

0.32

0.34

176

336

0

104

0

78

790

968

1.50

100

C70/85

34FA20R20

0.32

0.34

175

308

0

103

0

103

790

968

1.65

94

C70/85

30LSP20R10

0.30

0.30

168

397

113

0

0

57

790

968

3.0

109

C70/85

30FA20R10

0.28

0.30

170

388

0

111

0

55

790

968

1.5

92

C80/95

26FA20R10

0.24

0.26

155

413

0

118

0

59

790

968

2.0

100

C90/105

26FA20DSF10

0.24

0.26

155

413

0

118

59

0

790

968

2.0

100

C90/105

26FA20USF10

0.24

0.26

155

413

0

118

59

0

790

968

1.75

100

C90/105

*) Percentage ratio of SP demand for concrete to saturation SP dosage of mortar

26

Table. 6

Mixtures

Slump flow (mm)

T500 (sec)

V-funnel (sec)

J-ring step height (mm)

Sieve segregation (%)

Air content (vol.-%)

34LSP20R10

770

2.9

10.2

10

12.7

1.9

34FA20R10

780

2.9

10.5

10

12.5

1.4

34FA20R15

770

3.3

12.5

10

10.5

1.3

34FA20R20

760

3.7

16.4

10

8.3

1.4

30LSP20R10

730

4.8

11.0

10

8.3

2.7

30FA20R10

770

3.3

18.5

10

11.0

1.1

26FA20R10

760

6.7

19.7

9.5

4.7

1.0

26FA20DSF10

750

7.0

22.3

10

5.4

1.3

26FA20USF10

770

4.0

9.2

10

13.6

2.5

Table. 7 Results in this study

By EFNARC [4]

From reported studies [30]

Coarse aggregate (vol.-%)

31.7

27.0 - 36.0

28.1 - 42.3

Fine/ total aggregate (wt.-%)

45.0

48.0 - 55.0

38.8 - 52.9

Paste (vol.-%)

36.5

30.0 - 38.0

29.6 - 40.4

Powder (kg/m3)

514 - 590

380 - 600

410 - 607

Mixing water (kg/m3)

155 - 182

150 - 210

160 - 200

W/B ratio

0.26 - 0.34

0.28 - 0.36/

0.26 - 0.48

(by wt./vol.)

0.85 - 1.15

27

The list of figure captions Fig. 1 Compressive strength vs. percentage replacement by RHA Fig. 2 Efficiency factor vs. percentage replacement by RHA Fig. 3 Procedure of mix design method for proportioning SCHPC Fig. 4 Aggregate grading ranges for SCHPC Fig. 5 Relationship between compressive strength and W/C ratio; Walz curve [52] Fig. 6 Mini-cone slump flow and T250 time test Fig. 7 SSD of mortar formulated from SCHPC mixture ’’30LSP20R10’’ determined by minicone slump flow Fig. 8 Particle size distribution of cement and MAs used in this study Fig. 9 SEM images of undensified SF (a), densified SF (b), porous structure of RHA7.7 (c), FA (d), porous structure of RHA5.7 (e) and LSP (f) Fig. 10 Mixing procedure for SCHPC Fig. 11 SP demand of SCHPC vs. SSD of mortar formulated from the SCHPC Fig. 12 Expected vs. experimental compressive strength data at 28 days Fig. 13 Compressive strength of investigated SCHPC

28

Compressive strength at 28 days (MPa)

80

70

60 fMA = -0.027p2 + 1.049p + 63.207 R² = 0.97 50

40 0

5

10

15

20

25

30

35

30

35

RHA content (wt.-%)

Fig. 1

Efficiency factor at 28 days

4

3

2

1 k28 = 0.0007p2 - 0.076p + 3.056 R² = 0.99 0 0

5

10

15

20

25

RHA content (wt.-%)

Fig. 2

29

Inputs on expected performance (fc, SF, VF, SR, PJ)

Select and test the constituent materials

Determine voids of the compacted aggregate blend

Determine the primary paste volume

Determine the water-binder ratio

Determine the cement, mineral admixtures, and water contents

Determine the content of aggregate components

Determine the saturation SP dosage of mortar Adjust Vp Conduct trials to test fresh properties Adjust w/b Adjust SP

No Are fresh properties fulfilled? Yes Conduct trials to test hardened properties

No Is expected compressive strength fulfilled? Yes Designed mixture proportions

Fig. 3

30

100

Passing (%)

80

Real aggregate Funk & Dinger C16 A16

60 40 20 0 0.10

1.00 Sieve size (mm) Fig. 4

Fig. 5

31

10.00

350

25

300

20

250

15

200

10

150

5

Mini-slump flow T250 time

100

0 1

1.5

2

2.5

3

Superplasticizer dosage in mortar Fig. 7

32

3.5

T250 time (sec)

Mini-slump flow (mm)

Fig. 6

Cumulative passing (vol.-%)

100 80

60

USF DSF RHA5.7 RHA7.7 Cement LSP FA

40 20 0 0.01

1

100

Particle size (µm) Fig. 8

33

(a)

(b)

(c)

(d)

(e)

(f)

Fig. 9

34

Fine, coarse 1 min aggregate

Cement MAs 2 min

80 % Water

2 min

20 % Water SP

8 min

Fig. 10

SP demand for SCHPC (wt.-%)

3.0 R² = 0.96 2.5

2.0

1.5

1.0 1.0

1.5

2.0

2.5

3.0

3.5

120

130

SSD of mortar (wt.-%)

Expected compressive strength (MPa)

Fig. 11 130 R² = 0.95

120 110 100 90 80 80

90

100

110

Experimental compressive strength (MPa) Fig. 12

35

End of mixing

140 3 days

7days

28days

Compressive strength (MPa)

120 100 80

60 40 20 0

Fig. 13

36

*Graphical Abstract (for review)

1 k28 = 0.0007p2 - 0.076p + 3.056 R² = 0.99

25

300

20

250

15

200

10 Mini-slump flow

150

5

T250 time 100

0 5

10

15

20

25

30

1

35

Content (wt.-%)

2.5

3

Funk & Dinger

80

0.29

FA

20 - 60

0.56

SF

5 – 15

3.1 - 2.1

2.7 – 1.8

2.5

2.0

1.5

1.0 1.0

3.5

Real aggregate

k-value

15 - 55

5 - 20

2

100

LSP

RHA

1.5

R² = 0.96

Superplasticizer dosage in mortar

Rice husk ash content (wt.-%)

Mineral Admixtures

0

C16 A16

60 40 20 0 0.10

1.00 Sieve size (mm)

10.00

1.5

2.0

2.5

3.0

3.5

SP saturation dosage of mortar (wt.-%)

Expected compressive strength (MPa)

0

3.0 SP demand for SCHPC (wt.-%)

2

350

T250 time (sec)

Mini-slump flow (mm)

3

Passing (%)

Efficiency factor at 28 days

4

130 R² = 0.95 120 110 100 90 80 80

90

100

110

120

130

Experimental compressive strength (MPa)

Highlights     

The strength efficiency factor of rice husk ash is assessed. A mix design method is proposed for self-compacting high performance concrete. Saturation superplasticizer dosage of mortar is similar to superplasticizer demand for concrete. Efficiency factors of mineral admixtures are used to predict compressive strength. Concrete containing ternary binder has compressive strength in the range of 90-120MPa.

37